Voice Communication System Procurement Guidelines

EUROPEAN ORGANISATION FOR THE SAFETY OF AIR NAVIGATION EUROCONTROL Voice Communication System Procurement Guidelines Edition Number : 1.0 Edition Date : 22.05.2003 Status : Released Issue Intended for : General Public EUROPEAN AIR TRAFFIC MANAGEMENT PROGRAMME

Procurement Guidelines DOCUMENT CHARACTERISTICS TITLE Voice Communication System Procurement Guidelines EATMP Infocentre Reference: 03052701 Document Identifier Edition Number: 1.0 VCS Procurement Guidelines.doc Edition Date: 22.05.2003 Abstract This document offers guidance to ECAC Member States who wish to procure Voice Communication Systems that will be compatible at both the Operational and Engineering levels with the Eurocontrol Air Traffic Management Strategy For The Years 2000 +. Keywords VCS VCS-TF COMT Voice Communication Procurement Guidelines Ground Telephone Air-Ground Telephony Radio PBX QSIG ATS-QSIG ATS-R2 ATS No.5 Contact Person(s) Tel Unit Chris Clegg +32 2 7293356 CSM Business Unit STATUS, AUDIENCE AND ACCESSIBILITY Status Intended for Accessible via Working Draft General Public Intranet Draft EATMP Stakeholders Extranet Proposed Issue Restricted Audience Internet (www.eurocontrol.int) Released Issue Printed & electronic copies of the document can be obtained from the EATMP Infocentre (see page iii) ELECTRONIC SOURCE Path: H:\VCS Procurement guidelines Host System Software Size Windows_NT Microsoft Word 8.0b 523 Kb Edition: 1.0 Released Issue Page iii

Procurement Guidelines EATMP Infocentre EUROCONTROL Headquarters 96 Rue de la Fusée B-1130 BRUSSELS Tel: +32 (0)2 729 51 51 Fax: +32 (0)2 729 99 84 E-mail: eatmp.infocentre@eurocontrol.int Open on 08:00-15:00 UTC from Monday to Thursday, incl. DOCUMENT APPROVAL The following table identifies all management authorities that have successively approved the present issue of this document. AUTHORITY NAME AND SIGNATURE DATE Please make sure that the EATMP Infocentre Reference is present on page ii. VCS - Task Force Chairman Chris Clegg Head of Business CSM Mel Rees Acting Director ATM Strategies Wolfgang Philipp Edition Number: 1.0 Released Issue Page v

Procurement Guidelines DOCUMENT CHANGE RECORD The following table records the complete history of the successive editions of the present document. EDITION NUMBER EDITION DATE INFOCENTRE REFERENCE REASON FOR CHANGE PAGES AFFECTED Page vi Released Issue Edition Number: 1.0

Procurement Guidelines CONTENTS PART 1 - INTRODUCTION... 14 1. SCOPE OF DOCUMENT... 14 2. SCOPE OF THESE PROCUREMENT GUIDELINES... 14 3. ENQUIRIES AND COMMENTS... 14 PART 2 - VOICE COMMUNICATION SYSTEM IN OUTLINE... 18 1. GROUND TELEPHONE... 18 1.1 HUMAN-MACHINE INTERFACE (HMI)... 18 1.2 MAIN SWITCH... 18 1.3 INTERNAL INTERFACES... 19 1.4 EXTERNAL INTERFACES... 19 1.5 SYSTEM MANAGEMENT / ENGINEERING TERMINAL... 19 1.6 SYSTEM CONFIGURATION... 19 2. AIR-GROUND RADIO... 20 2.1 HUMAN-MACHINE INTERFACE (HMI)... 20 2.2 MAIN SWITCH... 20 2.3 INTERNAL INTERFACES... 21 2.4 EXTERNAL INTERFACES... 21 2.5 SYSTEM MANAGEMENT / ENGINEERING TERMINAL... 21 2.6 SYSTEM CONFIGURATION... 21 3. COMBINED GROUND TELEPHONE AND AIR-GROUND RADIO VCS... 22 PART 3 - USER FACILITIES... 24 1. GROUND TELEPHONE... 24 1.1 PRIMARY USER GROUND TELEPHONE FACILITIES... 24 1.2 DEFINITIONS AND ASSUMPTIONS... 24 1.3 ACCESS METHODS... 26 1.3.1 Direct Access... 26 1.3.2 Instantaneous Access... 27 1.3.3 Indirect Access... 29 1.3.3.1 Call Queuing facility... 29 1.4 CALL PRIORITY... 31 1.4.1 Intrusion by a Priority Call... 32 1.5 SIMULTANEOUS CALLS... 32 1.6 SUPPLEMENTARY USER TELEPHONE FACILITIES... 33 1.6.1 Common Appearance / Ring Group... 33 1.6.2 Call Transfer... 33 1.6.3 Hold... 33 1.6.4 Conference... 34 1.6.5 Call Pick Up... 34 1.6.6 Call diversion... 34 1.6.7 Group Hunting... 34 1.6.8 Call Completion/ Call back On busy... 35 1.7 ADDITIONAL SERVICE-RELATED GUIDELINES... 36 1.7.1 Audible Tones... 36 Edition Number: 1.0 Released Issue Page vii

Procurement Guidelines 2. AIR-GROUND RADIO... 38 2.1 DEFINITIONS AND ASSUMPTIONS... 38 2.2 RADIO ACCESS... 39 2.2.1 Basic Description... 39 2.2.2 Modes of Operation... 40 2.2.3 Receiving - frequency active... 40 2.2.4 Audio Device Selection Rx Mode... 40 2.2.5 Transmitting... 41 2.2.6 Side Tone... 41 2.2.7 Multiple Frequencies... 41 2.2.8 Transmitter / Receiver Selection... 41 2.2.9 Main and Standby Radio Coverage... 42 2.2.10 Frequency Cross-Coupling... 42 2.2.11 Use of Optional Channels... 43 2.2.12 Short-Term Recording... 43 PART 4 - HUMAN-MACHINE INTERFACE (HMI)... 46 1. GENERAL... 46 1.1 ACTIVATION AND PRESENTATION DEVICES... 46 1.2 AUDIO DEVICES... 47 1.3 MANAGEMENT OF MIXED AIR-GROUND RADIO AND GROUND TELEPHONE COMMUNICATIONS... 48 1.4 TRAINING FACILITIES... 49 1.4.1 Monitoring... 49 1.4.2 Student / Mentor Facility... 49 1.5 HUMAN ENGINEERING GUIDELINES... 49 1.6 PHYSICAL ENVIRONMENTAL CONSIDERATIONS... 51 PART 5 ENGINEERING GUIDELINES... 54 1. ENGINEERING GUIDELINES... 54 1.1 AVAILABILITY, RELIABILITY AND MAINTAINABILITY (ARM)... 54 1.1.1 Availability... 54 1.1.2 Reliability... 55 1.1.2.1 Reliability and System Redundancy... 55 1.1.3 Maintainability... 56 1.1.3.1 Hardware... 56 1.1.3.2 Software... 56 1.2 GENERAL RESPONSE CRITERIA... 57 1.2.1 Call Processing Delay... 57 1.2.2 PTT Set-Up Delay... 57 1.2.3 A/C call (Squelch) Delay... 58 1.2.4 Dial Tone Delay... 58 1.2.5 Software response delay... 58 1.2.5.1 Alarm Indications... 58 1.2.5.2 Configuration Changes... 58 1.2.6 System Response Times... 59 1.2.7 Performance Conditions... 59 1.2.8 Software... 59 1.3 TRAFFIC HANDLING CAPACITY AND BLOCKING... 60 1.3.1 Traffic Handling... 60 1.3.2 General Guidance on Non-Blocking Functionality... 60 1.3.3 PTT and A/C call Blocking... 61 1.4 SYSTEM MANAGEMENT... 61 1.4.1 Performance management... 61 1.4.2 Fault (or maintenance) management... 62 1.4.3 Configuration management... 62 1.4.3.1 Configuration of telephone and Radio Access keys... 63 1.4.3.2 Alpha-numeric identification labels... 63 1.4.3.3 Physical configuration parameters... 64 1.4.3.4 Allocation of "A" side and "B" side... 64 1.4.3.5 Recovery after system failure... 65 Page viii Released Issue Edition Number: 1.0

Procurement Guidelines 1.4.4 Accounting management... 65 1.4.5 Security management... 66 1.4.5.1 Physical security... 66 1.4.5.2 System security... 67 1.4.5.3 Public Network security... 67 1.5 MODULARITY... 67 1.5.1 General guidelines... 67 1.5.2 System Modularity for Security... 67 1.6 ACCESSIBILITY... 68 1.7 SAFETY AND PROTECTION... 68 1.8 ELECTROMAGNETIC COMPATIBILITY (EMC)... 68 1.9 SYNCHRONISATION STRATEGY... 68 1.10 LINE INTERFACES... 69 1.10.1 General... 69 1.10.2 Legacy Interfaces... 69 1.10.3 Public network interfaces... 70 1.10.4 Inter-VCS Circuit Interfaces... 71 1.10.4.1 Analogue Signalling Systems ATS-R2, ATS-No5... 71 1.10.4.2 Digital Signalling System EN 301 846 "ATS-QSIG... 71 1.11 NUMBERING SCHEMES... 72 1.12 STANDBY VCS REQUIREMENTS... 72 1.13 CALL AND EVENT RECORDING... 73 1.13.1 Radio and Telephone voice recording... 73 1.13.2 Telephone Call event recording... 73 1.13.2.1 Outgoing call information... 74 1.13.2.2 Incoming call information... 74 1.13.3 Radio Call event recording... 75 1.13.3.1 Outgoing call information... 76 1.13.3.2 Incoming call information... 76 1.13.3.3 Best Signal Selection... 76 2. CONNECTION APPROVALS REQUIREMENTS... 77 3. TRAINING... 77 4. DOCUMENTATION... 77 ANNEX A REFERENCES... 79 ANNEX B ABBREVIATIONS... 81 ANNEX C - REF MODEL EXAMPLE FOR THE MANAGEMENT OF INCOMING CALLS... 83 C.1 INTRODUCTION... 83 C.1.1 IDA Call Queue... 84 C.1.2 The DA Panel... 84 C.1.3 The IA Panel... 85 Edition Number: 1.0 Released Issue Page ix

Procurement Guidelines Page x Released Issue Edition Number: 1.0

Procurement Guidelines EXECUTIVE SUMMARY This document offers guidance to ECAC Member States who wish to procure Voice Communication Systems that will be compatible at both the Operational and Engineering levels with the ATM Strategy For The Years 2000+ [1]. The emphasis is on Ground Telephone aspects where the User Facilities are described in detail along with the Engineering requirements necessary to support them. Air-Ground aspects are also covered but to a much less extent than those for the Ground Telephone. In compiling these guidelines due regard has also been paid to work completed within ICAO to revise related parts of Annex 10 [7]. Thus VCSs specified in accordance with these guidelines should also have a high degree of compatibility with related ICAO Recommendations as well as those of Eurocontrol. Wherever possible the Features and other implementation aspects have been left open so as not to prevent VCS suppliers from offering innovative solutions. Edition Number: 1.0 Released Issue Page 11

Procurement Guidelines Page 12 Released Issue Edition Number: 1.0

Procurement Guidelines: PART 1 PART 1 INTRODUCTION Edition Number: 1.0 Released Issue Page 13

Procurement Guidelines: PART 1 PART 1 - INTRODUCTION 1. SCOPE OF DOCUMENT This document has been produced by the Voice Communications System Task Force (VCS-TF) convened by the Communications Team (COMT) of Eurocontrol. The purpose of the document, as its title implies, is to offer selective guidance to ECAC Member States in compiling a procurement specification for a Voice Communications System (VCS). The guidance is "selective" because it is only intended to address those matters that contribute towards a VCS being compatible, at both User/Operational and Engineering levels, with other VCSs both in neighbouring as well as distant States. It would thus be possible for all VCSs, that have been specified in accordance with these guidelines, to become part of an ECAC-wide voice telephone network, the justification for which is to provide voice communications systems in support of the Strategy for ATM in the Years 2000+ [1] and in accordance with the associated Communications Strategy [2]. Accordingly these guidelines do not constitute a complete and comprehensive VCS specification, which it is assumed, will be written by experienced Operational and Engineering experts. If preferred States may also request the assistance of Eurocontrol. Equally the Guidelines do not include any contractual procedures and endeavours to avoid the use of any terms or system descriptions that may be regarded as proprietary to a particular manufacturer. The objective is not to stifle innovation by manufacturers thus opening up the possibility of a number of VCSs products in a free market that may meet a particular customer's requirements. 2. SCOPE OF THESE PROCUREMENT GUIDELINES These Procurement Guidelines have been written to cover both Ground Telephone and Air-Ground Radio aspects. The emphasis, however, is on the Ground Telephone parts. For confirmation of the current status of these Guidelines please refer to Eurocontrol as detailed in Part 1: section 3 following. 3. ENQUIRIES AND COMMENTS Comments on this document are welcome and should be directed towards Eurocontrol as detailed below. Eurocontrol would also be pleased to provide answers to any enquiries that may arise. Page 14 Released Issue Edition Number: 1.0

Procurement Guidelines: PART 1 Eurocontrol Rue de la Fusee, 96 B-1130 Brussels Belgium For the attention of the CSM Business Division Tel ++ 32 2 729 3291 Fax ++ 32 2 729 3511 Edition Number: 1.0 Released Issue Page 15

Procurement Guidelines: PART 1 Page 16 Released Issue Edition Number: 1.0

Procurement Guidelines: PART 2 PART 2 VOICE COMMUNICATION SYSTEM IN OUTLINE Edition Number: 1.0 Released Issue Page 17

Procurement Guidelines: PART 2 PART 2 - VOICE COMMUNICATION SYSTEM IN OUTLINE A Voice Communication System (VCS) may be comprised of two major components Ground Telephone and Air-Ground Radio; each of these is described, in outline, below. 1. GROUND TELEPHONE The Ground Telephone component of a VCS permits telephone conversations to take place between Users (for a description of 'User' see Part 3: Section 1.2) connected to the same VCS or to other external Users. In many respects the everyday equivalent of a Ground Telephone VCS is the Private Branch Exchange (PBX) where many Users are able to call each other or to make long distance calls via the Public Switched Telephone Network (PSTN) or private circuits. In some cases a commercially available PBX may be all that is required for a particular application but the special attributes of a VCS designed and manufactured for ATM applications usually preclude this. Although the switching capabilities of a PBX and a VCS are almost identical, most commercially available PBX systems do not provide the functionality required at a Controller Working Position (CWP). The Ground Telephone component may be further considered to consist of five subsystems: Human-Machine Interface (HMI) Main Switch Internal Interfaces External Interfaces System Management / Engineering Terminal 1.1 Human-Machine Interface (HMI) The HMI requirements are further described in Part 4: section 1, but it is essentially the part that permits a User to make and receive telephone calls. Everyday examples include Ordinary Telephones, Feature-phones, Key-Pads and Attendant Consoles each of these have an increasing level of User Facilities and complexity. The HMI requirements are usually so specialised for ATM that off-the-shelf commercial PBX products will not meet them. 1.2 Main Switch This is the principal component of the system and contains all the switching hardware and software together with the interfaces to the HMI and interfaces to the outside world (external ports). Power supplies for all systems are also usually included here. Page 18 Released Issue Edition Number: 1.0

Procurement Guidelines: PART 2 The Availability, Reliability and Maintainability (ARM) requirements of the main switch (and all component parts) are addressed in Part 5: section 1.1 and these usually exceed those of off-the-shelf commercial PBX products. 1.3 Internal Interfaces Internal Interfaces connect the main switch to the HMI. Depending upon the multiplicity of HMIs required, several types of Internal Interface may be required. Although Internal Interfaces may be physically part of the Main Switch it is useful to regard them as separate components because they often contain special software or firmware that is independent of the main switch and control system 1.4 External Interfaces External Interfaces connect the main switch to the outside world and may be of digital, or analogue (exceptionally DC) types. Although External Interfaces may be physically part of the Main Switch it is useful to regard them as separate components because they often contain special software or firmware that is independent of the main switch and control system. (Further Engineering information on Ground Telephone External Interfaces is given in Part 5: section 1.10). 1.5 System Management / Engineering Terminal A System Management / Engineering Terminal can provide a multitude of facilities ranging from the configuration of an HMI through to the collection of system performance parameters. It is common for such terminals to be PC-based systems with sophisticated software to provide a user-friendly interface in order to carry out either tedious or complex tasks. (Further information on System Management / Engineering Terminals is given in Part 5: section 1.4). 1.6 System Configuration Having described the component parts of the Ground Telephone VCS as five subsystems above, there is no reason why (with the possible exception of the System Management / Engineering Terminal) such a system may not be supplied as a single unit including all components; such systems are often purchased either for very small operational units or as standby/back-up systems for large operational units as further described in Part 5: section 1.12. Edition Number: 1.0 Released Issue Page 19

Procurement Guidelines: PART 2 2. AIR-GROUND RADIO The Air-Ground Radio component of a VCS permits radio telephone conversations to take place between Users connected to the VCS and to mobile units primarily aircraft but also to ground mobiles too. In many respects the everyday equivalent of an Air-Ground Radio VCS is a radio control system that may be used by the emergency services (fire, police, ambulance and coastguard in particular). Radio applications are generally considered to be much more safety critical than those of Ground Telephone and accordingly the ARM criteria are much more stringent. The basic functionality is for a controller to be able to select one or more radio frequencies and then to be able to transmit to and receive messages from pilots of aircraft. The use of Headsets for this type of application is often common. In a similar manner to the Ground Telephone Component, the Air-Ground Radio component of a VCS may be further considered to consist of five sub-systems: Human-Machine Interface (HMI) Main Switch Internal Interfaces External Interfaces System Management / Engineering Terminal 2.1 Human-Machine Interface (HMI) The HMI subsystem essentially permits a User to select frequencies and to be able to either monitor them or to make transmissions on them usually both. A headset is a common audio device but many users prefer hand microphones and loudspeakers or handsets; a VCS should be able to accommodate all of these to meet any User preferences or operational requirements. Some form of control panel is also provided to select frequencies and to be able to see which frequency is active. Due to the individual requirements and preferences by ANSPs these guidelines do not include any specific details of HMI attributes or standards. 2.2 Main Switch This is the principal component of the system and contains all the switching hardware and software together with the interfaces to the HMI and interfaces to the transmitter and receiver equipment. Power supplies for all systems are also usually included here. Page 20 Released Issue Edition Number: 1.0

Procurement Guidelines: PART 2 2.3 Internal Interfaces Internal Interfaces connect the main switch to the HMI. It is common for only one type of proprietary Internal interface to be provided since the radio control panel is also proprietary. Although Internal Interfaces may be physically part of the Main Switch it is useful to regard them as separate components because they often contain special software or firmware that is independent of the main switch and control system. 2.4 External Interfaces External Interfaces connect the main switch to the radio transmitter and receiver equipment. External interfaces may be of several types to suit transmitters/receivers that are locally connected to those that require remote Radio Control Equipment (RCE). Many manufacturers also provide RCE as an integral part of the external interfaces since there are no common standards as compared with external telephone lines. Unless the RCE is also provided by the same VCS supplier problems with interfacing can be encountered. Due to the specialised nature of RCE these guidelines do not include any details of them 2.5 System Management / Engineering Terminal A System Management / Engineering Terminal can provide a multitude of facilities ranging from the configuration of an HMI through to the collection of system performance parameters. It is common for such terminals to be PC-based systems with sophisticated software to provide a user-friendly interface in order to carry out either tedious or complex tasks. Where a VCS supports both Radio and Ground Telephone services (see Section 2.3 above) a common system management / engineering terminal is often provided. Even when the Radio and Ground Telephone functions are not components of the same VCS, a common system management / engineering terminal could offer benefit in terms of maintenance and support. (Further information on System Management / Engineering Terminals is given in Part 5: section 1.4). 2.6 System Configuration Having described the component parts of the Air Ground Radio VCS as five subsystems above, there is no reason why (with the possible exception of the System Management / Engineering Terminal), such a system may not be supplied as a single unit including all components; such systems are often purchased either for very small operational units or as standby/back-up systems for large operational units as further described in Part 5: section 1.12. Edition Number: 1.0 Released Issue Page 21

Procurement Guidelines: PART 2 3. COMBINED GROUND TELEPHONE AND AIR-GROUND RADIO VCS As stated in Sections 1.6 and 2.6 above both the Ground Telephone and the Air- Ground Radio sub components of a VCS may be provided as single units. Equally it is possible for a VCS to be provided that combines all the functionality of both the Ground Telephone and Air Ground Radio components. To which extent this potential feature is used, will be governed by the User requirements and the Security aspects (see Part 5: Section 1.5.2). Most applications in Air Traffic Management will, in fact, require the combined VCS as illustrated in the Table 1 below and throughout the ATM industry the term VCS is usually interpreted as a combined system. Table 1: VCS Typical Configurations Flight Briefing Unit (FBU) Emergency Services Ground Telephone Small Combined Telephone and Radio VCS Medium Combined Telephone and Radio VCS Control Tower Large Combined Telephone and Radio VCS Control Centre NOTE: There is no firm definition of what constitutes a large, medium or small VCS, but for guidance purposes the following values can be used. - Large VCS >700 ports; - Medium VCS 350-700 ports - Small VCS <350 ports. Air Navigation Service Providers (ANSPs) who have a broad range of requirements as illustrated above may wish to consider the possible benefits in maintenance and support of having a common range of products to meet them. This concept can be extended such that the physical appearance of Controller Working Positions may be identical throughout an operations room. An example of this is the operational concept of the Tactical and Planner controller suite where the Tactical controller has both radio and telephone facilities whilst the planner may have telephone facilities only. The role or mission of each suite (which radio frequencies and telephone lines provided etc) is simply a question of assignment or configuration carried out from a common System Management / Engineering Terminal (see Part 4: HMI 1). The role of each suite can thus be changed for both operational and engineering purposes. Page 22 Released Issue Edition Number: 1.0

Procurement Guidelines: PART 3 PART 3 USER FACILITIES Edition Number: 1.0 Released Issue Page 23

Procurement Guidelines: PART 3 PART 3 - USER FACILITIES 1. GROUND TELEPHONE This section of the Voice Communications System (VCS) specification guidelines outlines the operational functions to support ground-to-ground telephone applications. 1.1 Primary User Ground Telephone Facilities This section describes the primary ground telephone facilities required by Air Traffic Controllers and other operational personnel in order to carry out their duties of Air Traffic Management. Performance criteria as demanded by such personnel are included without any reference to the engineering facilities needed to provide them. 1.2 Definitions and Assumptions Bi-lateral Agreement The term 'Bi-lateral Agreement' refers to the appropriate authorities within the 'A'-party and 'B'-party ANSPs. Busy Terminal busy The condition that arises when an incoming call has reached the 'B'-party CWP but there is no resource available to present the call to the user (see User definition). The Terminal busy condition should not arise on a DA call (Part 3: Section 1.3.1) or an IA call (Part 3: Section 1.3.2), but is possible for an IDA call (Part3: Section 1.3.3) in the event that the incoming call queue is full. An illustration of what is meant by Terminal Busy is given in ANNEX C "Reference Model example for the Management of Incoming Calls". NOTE: The condition of "User busy" in the sense of the User being occupied with other calls in progress while the call queue is not full is not relevant to these guidelines and is considered to be a matter of local operational procedure. Network busy The condition that arises when all speech paths between one VCS and another are either currently in use or (exceptionally) configured as out-of-service via the System Management Terminal. Throughout these guidelines, the term "congestion" is used synonymously with "network busy". Page 24 Released Issue Edition Number: 1.0

Procurement Guidelines: PART 3 Call parties The terms 'A'-party, 'B'-party and 'C'-party are used throughout these guidelines to identify the users involved in a telephone call, as follows: 'A'-party: 'B'-party: 'C'-party: the user who initiates a telephone call the calling party; the user who first receives the telephone call the called party; any other party involved in an established call. Dynamic display A device used for the visual presentation of operational information such as caller identities, call status and programmable touch-keys. Facility The term 'facility' is used to describe the function to be carried out and the term 'Feature' gives further details or the particular attributes of the Facility Key Throughout these guidelines, the term 'key' is used to refer to a single activation device such as a key, switch, button or an icon Normal/Abnormal The terms 'normal' and 'abnormal' refer to when the Performance criteria defined for each Facility are either met or infringed respectively Port A communication connection point to a VCS. Normally, a single simple analogue telephone extension will be associated with a single port although other interface types may require the association of more than one port to each interface. Supervisory Tones The various supervisory tones and announcements used (when applicable) by the VCSs are detailed in Part 3: Section 1.7.1. User An Air Traffic Controller or other operational person carrying out the duties of Air Traffic Management. NOTE: This definition does not include personnel carrying out administration and maintenance functions. Edition Number: 1.0 Released Issue Page 25

Procurement Guidelines: PART 3 1.3 Access Methods There are three types of Primary Telephone Facilities by which calls can be made known as "Access Methods"; these are: Direct Access; Instantaneous Access; Indirect Access. NOTE: The audible tones referred to in the sub-sections below should be provided to the User. The intention is to give an indication of the status of the called terminal or the network. However, in order not to distract the User from the task, in which they are engaged, the audible tones may be replaced by suitable visual indications. The types of which both audible and visual indications can be derived when external circuits are used will be dependent upon the signalling system used on those circuits. 1.3.1 Direct Access Facility Description (a) (b) (c) (d) (e) (f) (g) (h) (i) With this facility the operation of a single key by the 'A'-party is all that is required to initiate a call. The 'B'-party address is assigned and fixed semi-permanently in the 'A'-party VCS and is thus uniquely associated with each key and each key is labelled as such. Dial tone and out-going signalling tones are not given to the 'A'-party. Ringing tone should be given (and / or visually indicated). Busy tone shall be given if appropriate. Terminal Out-of-service shall be given should the call fail for any reason other than Busy. The 'B'-party is alerted to the presence of the incoming call by audio and or visual means as determined by the 'B'-party VCS. The 'A'-party identity is indicated to the 'B'-party either by association with a key assigned and fixed semi-permanently in the 'B'-party VCS or by means of a dynamic display. The 'B'-party must accept the incoming call by means of a single action associated with a key or dynamic display. Page 26 Released Issue Edition Number: 1.0

Procurement Guidelines: PART 3 (j) (k) (l) Due to either the exclusive, one-to-one, assignments of the keys between the 'A' and 'B' - parties or reserved capacity in the 'B'-party dynamic display, it is abnormal for the 'A'-party to encounter the 'B'-party busy; this is a fundamental attribute of the Direct Access Facility. Under normal conditions the 'B'-party can receive one or more Direct Access calls and by observing the identities of the respective 'A'-parties, together with defined operational procedure or (more likely) operational experience, the 'B'-party will deal with each call appropriately in the appropriate sequence. At the end of a call either the 'A'-party or the 'B'-party may be required to deselect/clear. Performance Criteria (a) Direct Access is designed to meet the requirements for Direct Controller- Controller Voice Communication (DCCVC) which stipulates that communication be established between radar controllers within 2 seconds in 99% of the time [3]. (b) The interval of 2 seconds is the delay between the 'A'-party initiating the call (Section 1.3.1 para (a)) and the 'B'-party receiving the call alert/indication (Section 1.3.1 para (g)). 1.3.2 Instantaneous Access Facility Description (a) (b) (c) (d) (e) (f) (g) With this facility the operation of a single key by the 'A'-party is all that is required to initiate a call; some ANSPs prefer, however, that it is necessary for the 'A'-party to sustain the key operation for the duration of the call. The 'B'-party address is assigned and fixed semi-permanently in the 'A'-party VCS and is thus uniquely associated with each key and each key is labelled as such. Dial tone and out-going signalling tones are not given to the 'A'-party. Ringing tone is not given to the 'A'-party. 'Terminal Out-of-Service' tone is given to the 'A'-party should the call fail for any reason including any busy conditions encountered. The arrival of the call from the 'A'-party to the 'B'-party causes, simultaneously, the events detailed in paras (g) to (I) inclusive. The 'A'-party identity is indicated to the 'B'-party either by association with a key assigned and fixed semi-permanently in the 'B'-party VCS or by means of a dynamic display. Due to the usually urgent nature of Instantaneous Access calls any visual (and/or audible) alerts should be distinctive from other types of call. Edition Number: 1.0 Released Issue Page 27

Procurement Guidelines: PART 3 (h) An audible alert is generated at the 'B'-party VCS in accordance with the following options: no audible alert an alert of fixed duration a continuous alert requiring a silencing action by the 'B'-party. (i) The 'B'-party VCS automatically accepts the incoming call without any intervention required by the User; this occurs regardless of the 'B'-party being engaged on any other type of call. Thus 'B'-party busy is totally abnormal and should result in Terminal Out-of-Service tone being given to the 'A'-party. At this stage the speech channel from the 'A'-party to the 'B'-party is established. The 'B'-party ANSP may decide to have any speech from the 'A'-party handled in one (or more) of the following ways: connected in conference with other speech at the 'B'-party CWP; directed to a loudspeaker; directed to one side of a split-working headset; any other arrangement appropriate to the local operational procedures. (j) (k) (l) (m) The establishment of the call as detailed in para (a) above may also result in the 'A'-party having some Monitoring facilities of the 'B'-party's Controller Working Position including ground - ground and air-ground radio telephony. This enables the 'A'-party to exercise discretion before passing the message. Although such monitoring will require the prior establishment of a bi-lateral agreement if two ANSPs are involved, it is recommended throughout the ECAC region. The 'B'-party may respond to the 'A'-party by activation of a key associated with the incoming call. This action enables the return speech path if it occurs during the current call; otherwise, it is treated as a new Instantaneous Access call. If the 'B'-party responds during the current call, this has the effect of preventing the call from being cleared until both parties clear the call; without B-party response, the call is cleared when the 'A'-Party terminates the IA-call. Call clearing has no effect on other calls in progress at either the 'A'-party or the 'B'-party. Performance Criteria (a) Instantaneous Access is designed to meet the requirements of Instantaneous Controller-Controller Voice Communication (ICCVC) which stipulates that twoway direct communication be established between non-physically adjacent controllers within 1 second or less in 99% of the time [3]. Page 28 Released Issue Edition Number: 1.0

Procurement Guidelines: PART 3 (b) The interval of 1 second is the delay between the 'A'-party initiating the call (Section 1.3.2 para (a)) and the 'A'-party to 'B'-party speech path being established (Section 1.3.2 para (i)). 1.3.3 Indirect Access The Indirect Access facility enables a 'A'-party to enter a complete 'B'-party address on a telephone dialling keypad (or equivalent device) in order to select a network and to cause a call attempt to be made to the supplied address. This is equivalent to normal dialled telephone operation. In addition to dialling the 'B'-party address in full, the following PBX-type Facilities are also used to establish Indirect Access calls: Abbreviated Dialling: entering a short code (up to four digits, a character string of unrestricted length or a specific labelled key) on a telephone dialling keypad (or equivalent device), shall cause a call attempt to be made from the 'A'-party to a predefined 'B'-party associated with the supplied code; Last Number Redial: the operation of a key, shall cause a call attempt to be made from the 'A'-party to the 'B'-party to which the most recent previous call attempt (successful or unsuccessful) was made; Ringing tone and busy tone are given to the 'A'-party as appropriate. A suitable mechanism (i.e., Terminal Out-of-service tone) shall be provided to inform the 'A'-party, should the call fail for any reason other than Busy. It may be possible for calls from more than one 'A'-party to be presented to a 'B'-party simultaneously. In such cases, the selection of the next call to be answered by the 'B'-party is determined either directly by the 'B'-party or on the basis of an operational parameter such as longest waiting time or the Priority of the incoming call (see Part 3: section 1.4) It is possible for either the 'B'-party or the 'A'-party to terminate an established Indirect Access call. 1.3.3.1 Call Queuing facility The Call Queuing facility provides a means for a user to have a number of incoming calls placed in a queue so that the order of their arrival and some means of identifying their origin can be easily determined. Edition Number: 1.0 Released Issue Page 29

Procurement Guidelines: PART 3 Although the means of indicating the order of arrival is implementation specific, it is common for some form of stacking arrangement to be used. Consideration needs to be given to the maximum size of queue that would be considered manageable. Typically, a queue would be 5 or 6 calls deep. The extent to which the call origin (identity of the 'A'-party) can be displayed will be dependent upon the signalling system when external lines are involved but it is recommended that a global identity should indicate the generic source of the call if a specific identity is not available. Some examples are given in Table 2. Table 2: Examples of generic identities Identity indicated ATSN PSTN Origin Another user on the ATS network but without the means to indicate the ATSN number. A PSTN user without 'A'-party identity. The basic attributes of the Call Queuing facility are as follows: all calls in the queue are in a calling (ringing) condition until answered; a manual process may be used for selecting the next call to be answered but this does not preclude some form of first-in-first-out automatic selection; Additional indications should be used to identify Priority Calls (Part 3: Section 1.4) that have arrived in the queue. Such indications might include a unique flag against the queue entry, a different display attribute (e.g. flashing characters or a unique colour) and a distinctive audible alert. Although it will usually be IDA calls that are directed to the Call Queuing facility, in some exceptional circumstances (most commonly fault or call diversion conditions) DA calls may also be placed in a call queue. In these cases, it is recommended that some additional means of identifying the call as a DA call is given. An illustration of the use of a call queue is given in ANNEX C "Reference Model for the Management of Incoming Calls". Page 30 Released Issue Edition Number: 1.0

Procurement Guidelines: PART 3 1.4 Call Priority Description The priority facility is a means of attaching an indicator (or flag) to a telephone call to show that it is "urgent" as opposed to "routine". It is intended for use when it is necessary to make an urgent call concerning the safety of aircraft (i.e., an emergency situation) and to enable, if necessary, the interruption of less urgent calls in progress at the time. Thus calls can be made with or without priority so that there are two types as follows: Priority Calls Routine Calls The ultimate decision and responsibility as to whether a call is a Priority Call rests with the 'A'-party in accordance with local operational procedures. There are 3 ways in which a priority call can be made: i) manually before the call is made: before making the call, operation of a priority key will set the call to "Priority". This method is used when the call is already known to be urgent; ii) during call set up: this method would be used as a reaction to an urgent operational situation that has arisen, including a delay in answering at the far end or on receipt of busy tone; iii) automatic setting of priority: the calls from a particular CWP or set of keys is pre-programmed in the VCS to be "Priority". This method can be used for operational reasons when calls made from a particular CWP or key are always to be treated as urgent. It is recommended that the setting of the CWP or keys for automatic priority is an easily selectable option by means of the system management terminal. Equally, the 'B'-party VCS should react to an incoming priority call in the following manner: i) provide some means of indicating that a priority call has been received (e.g. special visual and/or audible indications); ii) allow the priority call to intrude in a call already established (see Section 1.4.1 below) If a priority call cannot proceed due to congestion (all available circuits, links or channels being busy), the priority call should interrupt an established unprotected routine call (should one exist), thus allowing the priority call to proceed. Before the established routine call is interrupted, all parties engaged in that call should receive an interrupt warning tone (see Table 3 in Section 1.7.1 General Public). Edition Number: 1.0 Released Issue Page 31

Procurement Guidelines: PART 3 The priority call interruption implementation should also be available for VCSs acting as transit VCSs. 1.4.1 Intrusion by a Priority Call In the event that the 'A'-party has made a Priority Call but encounters the 'B'-party busy, Intrusion should take place automatically. Upon Intrusion all Parties are connected together in conference (see Part 3: Section1.6.4). Before the Intrusion occurs a warning tone (see Table 3 in Section 1.7.1) should be given. It should be possible for any user to be protected against intrusion by other users. This protection should be selectable either individually on a user-by-user basis or as a single parameter for all users connected to a VCS. 1.5 Simultaneous Calls A Simultaneous Call (SC) occurs when two Users call each other at exactly (or very nearly exactly) the same time. Simultaneous calls may arise as a result of any type of call (IA, DA and IDA) but the outcome will vary depending upon the specific situation prevailing at the time. Overriding Principles In all cases of simultaneous calls the following overriding principles will apply: a) Indeterminate call states and/or VCS conditions shall not arise b) Users shall not receive false, ambiguous or misleading indications c) Notwithstanding the specific situations described below the guaranteed outcome for both Users shall be a User Busy indication. Specific Situations There are two specific simultaneous call situations that should be considered. These are: 1. Both Users Connected to the same VCS 2. Each User Connected to a separate VCS of any type Situation #1 Both Users connected to the same VCS In this situation, within the performance criteria stipulated for Direct Access and Instantaneous Access (Part 3: sections 1.3.1 and 1.3.2 respectively), a simultaneous call attempt should result in both Users being connected. Page 32 Released Issue Edition Number: 1.0

Procurement Guidelines: PART 3 Situation #2 Each User Connected to a Separate VCS. In this situation, within the performance criteria stipulated for Direct Access and Instantaneous Access (Part 3: sections 1.3.1 and 1.3.2 respectively), a simultaneous call attempt should result in one of the following outcomes. a) Busy tone presented to the Users. b) An automatic re-dial by each VCS after an interval of random length not exceeding 3s. If this attempt is also unsuccessful, the re-dial sequence should be repeated. If, after the second attempt, the re-dial sequence is unsuccessful, Busy tone should be presented to the User and the re-dial sequence stopped. NOTE: By bi-lateral agreement the outcome (a-b) for simultaneous call attempts has to be defined for each access method (IA, DA, IDA). 1.6 Supplementary User Telephone Facilities Most VCSs will have a wide range of PBX-type facilities and it is not the purpose of these guidelines to describe all of these in detail. The following Facilities are recommended as those most useful for ATM applications some of which can be found in the ICAO Annex 10 Recommendations [7]. It should be noted that these services are considered to be provided locally in each VCS with no specific requirement that they should interoperate with other VCSs in the ATS network. 1.6.1 Common Appearance / Ring Group The Common Appearance service allows a number of users to be logically grouped for the purpose of receiving calls. Calls to a Common Appearance Group are presented to all members simultaneously for anyone to answer. Users need to be aware, however, that certain types of connection to remote VCSs can cause complexities with implementation (usually associated with numbering and addressing in modern signalling systems) and specialist technical advice is recommended if this facility is required. 1.6.2 Call Transfer The Call Transfer service enables a user involved in an active call to establish a new call between the other user in the active call and a third party. 1.6.3 Hold The Hold service allows a user to disconnect temporarily from an established call in order to carry out other telephony functions before returning to the original established call. Edition Number: 1.0 Released Issue Page 33

Procurement Guidelines: PART 3 1.6.4 Conference The Conference service enables a user to interconnect a number of Controller working positions and/or external lines of varying types, allowing full speech facilities to all connected parties. NOTE: An established conference is maintained until only two parties remain connected (at which point it reverts to being a normal basic call). The conference is not released when the originator clears. Consideration should be given to the complexities of managing conferences of more that 5 parties in an ATM situation before the dimensions of the conference are specified. It is also recommended that costs for having this facility are sought from potential suppliers and that checks are made if there are any regulatory restrictions (see Part 5: Section 2). 1.6.5 Call Pick Up The Call Pickup service enables a user to answer a call that is in the alerting phase (ringing) at another user's terminal. 1.6.6 Call diversion The Call Diversion service enables a user to cause all incoming DA and IDA calls to that user to be routed to another user in the following circumstances: unconditionally; if a busy condition is detected at the 'B'-party; if the 'B'-party fails to answer an incoming call within a predetermined time (no reply). 1.6.7 Group Hunting The Group Hunting service allows a number of users, as a configuration option, to be associated in a group (a Hunt Group) with a single address. Calls to that address will be routed to one of the users in the group using a predefined distribution algorithm. NOTE: The difference between the Group Hunting service and the Common Appearance service is that a call to a Hunt Group causes only one member of the group to be alerted whereas a call to a Common Appearance group causes all members of the group to be alerted. In addition to the Hunt Group address, each member of a Hunt Group may also be assigned a unique address from the VCS numbering plan. A user may belong to more than one Hunt Group. Page 34 Released Issue Edition Number: 1.0

Procurement Guidelines: PART 3 1.6.8 Call Completion/ Call back On busy The Call Completion Facility enables the completion of an Indirect Access call to another user, which was unsuccessful because a busy condition was encountered at the B party; Edition Number: 1.0 Released Issue Page 35

Procurement Guidelines: PART 3 1.7 Additional Service-Related Guidelines 1.7.1 Audible Tones A VCS should be capable of providing call parties with audible tones, as recommended in Table 3 below, to indicate call progress. Dial Ringing Table 3: System tones Tone Purpose Frequency (Hz) Terminal busy Congestion (Note 1) Number Unobtainable (Note 2) Interrupt warning (Note 2) Intrusion warning (Note 2) Returned to a user when that user indicates to the system readiness to dial (for example, taking the telephone set off-hook). Returned to the 'A'-party after successful call establishment and prior to call acceptance. Returned to the 'A'-party if all available voice paths to a user are occupied. Returned to the 'A'-party if a call cannot be completed to the required 'B'-party due to all appropriate inter-vcs links being occupied or otherwise unavailable. Returned to the 'A'-party if a terminal is "Out of Service" or the 'B'-party address is unassigned. Injected into the voice path to warn a party of the imminent priority interruption of an established call. Injected into the voice path to warn a party of the imminent priority conferencing of an established call Period 425 continuous 425 (1 s on, 4 s off), repeated 425 (0.5 s on, 0.5 s off), repeated 425 (0.5 s on, 0.5 s off), repeated 1000 (0.5 s on, 0.5 s off), repeated 1000 (40ms, 0.5s off) repeated for up to 15s prior to forced disconnection 1000 1 s on Note 1: The recommendation for congestion tone is the same as that for busy tone. If users wish to distinguish between the two tones, a dual frequency tone, e.g. 425Hz / 1000Hz (0.5s each; repeated) can be used. Note 2: Not specified in ITU-T Recommendation E.180 [20] Page 36 Released Issue Edition Number: 1.0

Procurement Guidelines: PART 3 The tones in Table 3 conform, wherever possible, to those specified in ITU-T Recommendation Q.35/E.180 [20]. Regional variations in the tones generated by a VCS are possible where: the tones are generated by the local VCS; the tones are transmitted to another VCS and a bi-lateral agreement exists between the two ANSPs involved. Edition Number: 1.0 Released Issue Page 37

Procurement Guidelines: PART 3 2. AIR-GROUND RADIO This section describes the radio functionality recommended at a Controller Working Position (CWP) where Air-Ground Radio facilities are required. It does not specify how this functionality is to be achieved technically or the parameters within which the radio system shall operate. Although not necessarily required at every CWP, all functions should be supported by the VCS, and be capable of being assigned to CWPs as required. 2.1 Definitions and Assumptions Dynamic display A device used for the visual presentation of operational information such as radio frequencies selected, frequencies in-use / aircraft calling. Key Throughout these guidelines, the term 'key' is used to refer to a single activation device such as a key, switch, button or icon. User An Air Traffic Controller or other operational person carrying out the duties of Air Traffic Management. Push-to-talk (PTT) PTT is the User action of operating a key to transmit on one or more radio frequencies. The PTT key itself is invariably a mechanical device spring loaded to deactivate upon release but some operational applications require the use of a PTT lock-on mechanism. Aircraft (A/C) Call A/C call is a visual indication presented to the User that a particular frequency is active due to the reception of a carrier frequency by one or more receivers. A/C call is often associated with Mute Lift or Squelch. How A/C call is conveyed to the CWP is beyond the scope of these guidelines. Radio Frequency The term Radio Frequency is used to refer to a nominal ATC frequency such as 123 decimal 00 (25kHz spacing), 123 decimal 000 (8.33kHz spacing). Radio Channel The term Radio Channel is used to specify the nominal centre frequency in conjunction with a specific radio location when in fact the actual frequency used may be an off-set of the nominal sector frequency. Furthermore a radio channel always defines at least a logical transmission line, very often it specifies the VCS s physical radio interface. Page 38 Released Issue Edition Number: 1.0

Procurement Guidelines: PART 3 Radio Coverage The radio coverage is the airspace in which a frequency is usable. The use of more than one Tx/Rx equipment to control the extent of radio coverage is useful in some circumstances: Airspace size Geographical considerations (mountains, sea..) Main and standby radio coverage Remote/Radio Control Equipment (RCE) In situations where transmitters (Tx) and receivers (Rx) are remote from the main VCS equipment some form of Remote Control Equipment (RCE) may be required. In essence RCE is designed to provide two-way remote control and telemetry using a variety of interconnections ranging from dc cables, Network operator provided analogue or digital links to public and private radio links. Thus the RCE bridges the gap between the VCS and the Tx / Rx equipment. Specification of RCE is beyond the scope of these guidelines, but it must be compatible with the VCS interfaces. ANSPs may perceive the provision and management of RCE as an autonomous facility in which case problems can arise with specifying the interfaces and agreeing points of demarcation with several parties involved. Although these guidelines provide no RCE specific details the following two sets of facilities and services are common requirements:- Tx / Rx Services Voice Push-to-talk (PTT) A/C call or Squelch Automatic Gain Control / signal strength Equipment status Site Management Information Door contacts Fire alarm Intruder alarm Power failure 2.2 Radio Access 2.2.1 Basic Description Radio access enables a User to transmit and receive voice communications on selected radio frequencies. Edition Number: 1.0 Released Issue Page 39

Procurement Guidelines: PART 3 2.2.2 Modes of Operation Radio access at a CWP is activated by the operation of a key associated with a particular frequency. The key enables a particular radio frequency to be in one of four modes: Off/Deselected Receive only (Rx) Transmit and receive (Tx/Rx) Cross-coupled 2.2.3 Receiving - frequency active When Rx mode has been selected the User can hear any transmissions that are made on that frequency. At the same time the presence of the carrier frequency, regardless of speech modulation, will also cause the A/C call visual indication at the CWP. 2.2.4 Audio Device Selection Rx Mode Information on audio devices is given in Part 4 (HMI), Section 1.2. This facility enables the User to select whether transmissions received from aircraft are directed to either a headset or loudspeaker at the CWP. For safety reasons, the system should have to ensure that: a) Once the audio device selection for a specific radio channel at a CWP has been completed, this should be indicated to the user. b) The selection of audio through a headset should only be allowed if the headset jacks are plugged in the CWP. Compliance with this requirement will enable the radio channels selected in the headset to be automatically deselected from the headset and selected in the loudspeaker when the jacks are removed. The loudspeaker volume should be adjustable by the User, but with a limited minimum according to operational requirements; some means of indicating that the loudspeaker volume is at minimum should be provided. These measures should guarantee that the audio can be heard at the CWP. c) It is not possible to select a frequency without having an audio device (headset or loudspeaker) connected. d) Any frequencies that have been enabled on the VCS do not go unmonitored by always ensuring that they are Rx selected on at least one (typically a supervisor s) CWP. Jack-coded plug-in devices (such as headsets) are commonly used to determine which (if any) audio devices are connected. Page 40 Released Issue Edition Number: 1.0

Procurement Guidelines: PART 3 2.2.5 Transmitting When both receive and transmit ( Tx/Rx ) mode has been selected the User can transmit on the frequency by operating a Push-To-Talk (PTT) key. It should not be possible to transmit on a frequency without receive also being selected. 2.2.6 Side Tone When transmitting, Side Tone is the User s own speech fed, at reduced level, into the User s ear-piece in Hand Microphone Telephones or Headsets. Side tone may be generated locally by the VCS or from speech received off-air via a receiver. The latter method has the advantage of proving, to some extent, that the system is working but complexities associated with audio delays, phase shifts and multiple receiver operation often precludes its use. 2.2.7 Multiple Frequencies A CWP may have radio access to several frequencies, each of which can be set individually in one of the four modes described in section 2.2.2 above. Thus simultaneous reception on more than one frequency is possible; similarly simultaneous transmission on more than one frequency is possible by operation of a common PTT key. The total quantity of frequencies that can be accessed simultaneously at a CWP will be specified by the ANSP. 2.2.8 Transmitter / Receiver Selection ANSPs may require that the extent of radio coverage for each frequency can be controlled by transmitter and/or receiver selection; several options are available. Option 1: Individual transmitter and receiver selection is either a VCS or RCE configurable parameter. The User has no means of selection available at the CWP. Option 2: The User can select at the CWP, which transmitter and receiver combinations are in use on each frequency. The quantity of transmitters and receivers and permissible combinations including default settings - will be specified by the ANSP. Option 3 The User can select at the CWP which transmitter locations and receiver locations should be active. Automatic Best Signal Selection (BSS) chooses the specific receiver signal transferred to loudspeaker/headset. Edition Number: 1.0 Released Issue Page 41

Procurement Guidelines: PART 3 NOTE: The issue of co-frequency and other types of radio interference as well as audio phase interference and additional complexity in conjunction with cross-coupling are beyond the scope of these guidelines. 2.2.9 Main and Standby Radio Coverage ANSPs may require standby radio coverage for each frequency. The means of selection and control of such coverage will be specified by the ANSP but the following are typical switching possibilities: Automatic switching on line failure or transmit/receive loop failure detection Switching on command of the System Management/Engineering Terminal Manual switching directly on radio interfaces 2.2.10 Frequency Cross-Coupling Cross-coupling may be applied to two or more frequencies but the principles may be illustrated with reference to two cross-coupled frequencies A and B as follows. If an aircraft transmits on frequency A it is received on the ground and cross-coupled to be re-transmitted on frequency B. For the User on the ground when they transmit on either frequency A or B both transmitters will be activated at the same time. How cross-coupling is effected is beyond the scope of these guidelines and the extent (two or more frequencies) will be specified by the ANSP. Also the means of selection and control of cross-coupling will be specified by the ANSP but the following are typical options: At any CWP At a specified supervisor CWP By means of the system management terminal Whatever means of cross-coupling is selected it is extremely important that the User (or Users) are given clear indications which frequencies are in cross-coupled mode. NOTE: Operational safety hazards, particularly during busy/heavy traffic situations, may arise due to cross-coupling where the chance of missed or disturbed radio transmissions increases significantly. These operational safety hazard considerations are beyond the scope of these guidelines. In view of the safety hazards outlined above consideration should be given to restricting the extent of cross-coupling as follows:- limiting the number of frequencies that can be cross-coupled limiting the number of cross-coupling sessions at a CWP Page 42 Released Issue Edition Number: 1.0

Procurement Guidelines: PART 3 limiting the number of cross-coupling sessions for the whole VCS It is also important, in order to prevent coupling chains, to ensure that a particular frequency can only be included in one coupling session. 2.2.11 Use of Optional Channels This facility enables an authorised User to configure access, by pagination or any other means, to optional channels that had not been pre-configured at the CWP. 2.2.12 Short-Term Recording The CWP should provide a local short-term digital recording and instant replay function of the last radio communications (minimum 3 minutes duration). Edition Number: 1.0 Released Issue Page 43

Procurement Guidelines: PART 3 Page 44 Released Issue Edition Number: 1.0

Procurement Guidelines: PART 4 PART 4 HUMAN-MACHINE INTERFACE (HMI) Edition Number: 1.0 Released Issue Page 45

Procurement Guidelines: PART 4 PART 4 - HUMAN-MACHINE INTERFACE (HMI) 1. GENERAL Each User interfaces with the VCS through a Controller Working Position (CWP) which provides a means of communication for both Ground Telephone and Air- Ground applications. The Features and attributes of the HMI are perhaps the most critical part of the VCS design since they have a direct impact upon the efficiency and safe working of Users. Some guidance on HMI aspects are given in this section but it is recommended strongly that the best way of selecting HMI is to permit Users the opportunity to try them out, at length, in realistic situations. As stated in Part 1 these guidelines can only offer some general information on the HMI for Air-Ground applications. For the Ground Telephone part there are also no strict rules regarding the physical design of the CWP but ANNEX C provides a typical model on its layout and functionality. There are also strong preferences throughout Eurocontrol s ANSPs as to the extent of separation that should be provided between the Ground Telephone and Air- Ground components of a VCS. Some ANSPs require that as much separation be provided as possible with perhaps only a headset being a common device. On the other hand some ANSPs prefer a totally integrated solution with Ground Telephone and Air-Ground sharing common systems including all aspects of the HMI. These guidelines make no recommendations on these matters but some points for consideration are given in PART 5: section 1.5 (Modularity). 1.1 Activation and presentation devices A CWP uses a range of activation and presentation devices to provide access to all of the user-functions implemented by a VCS. These devices may include, but are not limited to: activation devices: - touch-sensitive screens; - mouse or tracker-ball pointers in conjunction with screen icons; - physical push-button switches; - keyboard or keypad; - for the Air-Ground Push-to-talk (PTT) operation (See Part 3: section 2.1) mechanical keys are preferred including those that are integrated into hand microphones, desk-mounted, floor/foot switches and free or clip-on lapel switches integrated into a Headset cable Page 46 Released Issue Edition Number: 1.0

Procurement Guidelines: PART 4 presentation devices: - CRT monitor; - plasma display; - LCD display; - LED or LCD indicators - illuminated keys. The ability to re-configure the layout of a User's VCS panel is often a requirement that prescribes the use of dynamic displays for both activation and presentation. Displays with segmented touch-sensitive screens are popular devices for this purpose. For the future there may also be a trend towards total integration of the CWP to include all services radar, radio, telephone etc for which computer graphic displays and on-screen selection via mouse-type input devices are likely solutions. 1.2 Audio Devices The audio devices that are common for use by European ANSPs include a combination of the following devices: Headsets including Telephone/Radio Split Headsets and noise-cancelling microphones Moveable Desk microphones Fixed Boom Microphones Hand microphones Loudspeakers Hand Microphone Telephones (telephone handsets) In addition to personal preferences, the choice of which devices to be used is greatly influenced by the CWP ergonomics and the working environment. Some of the common problems that arise are detailed below: Clutter moveable devices such as desk microphones Cable limitations (physical length) and cable tangles Edition Number: 1.0 Released Issue Page 47

Procurement Guidelines: PART 4 Obscuring cables and fixed devices obscure displays and panels etc Noise nuisance arising from both the ambient environment, adjacent Users and loudspeakers etc Feed-back Audio management and planning across the whole workplace (control room) is thus an important criteria to be considered as part of the VCS specification not only from the perspective of the local Users but also for remote Users including pilots on the flight deck. 1.3 Management of Mixed Air-Ground Radio and Ground Telephone Communications The use of the audio devices, described in the section 1.2 above, is subject to ANSP and local preferences, but one of the more complex situations to be considered is the Tactical Controller in an Area Control Centre who uses both Air-Ground Radio and Ground Telephone communication facilities. The principle problem in this type of situation is that a pilot can have no knowledge of how the controller he is about to contact may be engaged with Ground Telephone calls. A similar problem may also arise with other Air-Ground Radio calls but it is assumed that these are covered by established operational procedure. It is generally (but not exclusively) agreed that Air-Ground Radio communications takes precedence over those of Ground Telephone i.e. the Radio is always heard. One way of accomplishing this is by the use of split-headset working. Split-Headset Working In this configuration, the controller for all outgoing speech uses a common headset microphone. Incoming Ground Telephone calls will always be routed to one earpiece. While a Ground Telephone call is in progress, an incoming Air-Ground Radio call may trigger one of the following effects: a) Ground telephone speech is suppressed and both ear-pieces receive the Air- Ground Radio call. b) The Air-Ground Radio call is routed to one specific ear-piece. When the controller replies by activation of his PTT key, the pilot receives the transmission in the usual way. Some ANSPs also allow the remote telephone caller to hear the controller s response to the aircraft, others prefer that it is suppressed. Page 48 Released Issue Edition Number: 1.0

Procurement Guidelines: PART 4 A Safety hazard may arise by mixing air-ground and ground-ground calls. Thus facilities combining A/G and G/G-voice should be carefully considered. Ground telephone calls are never mixed, inadvertently with Air-Ground Radio transmissions to the pilot. Other Variations Other variations include the following:- a) use of separate telephone and radio audio devices b) common loudspeaker and common microphone c) Instantaneous Access (IA) calls always routed to a separate loudspeaker sometimes with a latching indicator so that the calling party may be identified. 1.4 Training Facilities 1.4.1 Monitoring A means of monitoring may be provided to enable a suitably authorised User to listen in on voice communication from one or more other User terminals. 1.4.2 Student / Mentor Facility The Student/ Mentor Facility is similar to the Monitor Facility described in section 1.4.1 above, but is specifically associated with an individual Controller Working Position (CWP). It includes a monitor Facility, but the Mentor is also able to activate their own microphone whilst at the same time disabling that of the Student so that they can take executive control of the conversation. This facility is particularly important for Radio applications when Student's are undergoing on-the-job training, but is applicable to both Radio and Ground Telephone facilities. 1.5 Human engineering guidelines The following guidelines identify some important human engineering aspects that should be considered for Human Machine Interfaces (HMI): a) The interaction between a controller and the HMI should leave the controller in no doubt about the next action to be taken in implementing the current function. b) A HMI should make it clear to the controller what type of input is required at any particular instant. Edition Number: 1.0 Released Issue Page 49

Procurement Guidelines: PART 4 c) A HMI should immediately make it clear to the controller that invalid data has been entered. d) Any message, instruction or information should be displayed for a sufficient period to allow the controller to read it. e) Display attributes such as colours, bolding, flashing and highlighting should only be used in those situations where the impact they cause is essential. Over-use can be distracting and can lead to important messages being ignored. f) The current status of all function keys and direct access keys should be obvious at all times. g) Any change in the status of a function key or direct access key should be highlighted by an appropriate means. h) The availability of a particular function or service should be shown by the status of the indicator associated with the key that activates the service. i) The indicator associated with a Direct Access key or an Instantaneous Access key should use different attributes (for example, lit, unlit, coloured and flashing) to distinguish between: an active call in progress; no active call or service in progress (idle); an unanswered incoming call; priority calls busy/congestion. j) The indicator associated with the A/C call should be distinctive to enable active frequencies to be easily identified. k) A distinctive and clear indicator showing any frequencies that have been cross-coupled should be provided. l) A set of keys grouped to represent a standard telephone dial-pad should be available for the entry of numeric (address) data. m) It should be possible to configure the keys and indicators of touch sensor devices (TSD) for left-handed as well as right-handed operation. n) Great care should be exercised in the choice of displays/indicators to be used so that they are usable in the actual physical HMI environment. Particular care should be taken with regard to: Page 50 Released Issue Edition Number: 1.0

Procurement Guidelines: PART 4 Viewing angle Adjustable Brightness (day, night, sun glance operation etc). Light reflections obscuring visibility Adjustable tone volume Selectable tones Particular consideration should be given to the sensitivity and feel of push-buttons as well as feedback on activated touch sensors. 1.6 Physical Environmental Considerations The keys, panels and displays associated with a VCS are usually located in a combined Work Position that houses the HMI of many other systems comprising the CWP. Care should be taken to ensure that the various components can co-exist in the physical environment intended and that the environment itself is suitable. Particular consideration should be given to addressing the following known problems: Electrical interference from adjacent units; Inadequate ventilation and excessive heat generation, the latter of which may demand air conditioning for components that would otherwise not need it; Noise generation by cooling or storage devices should be avoided, thus no fan or mechanical disk drives should be used for VCS operator position equipment All touchable equipment (keys, switches, touch sensor devices etc.) should be of such kind that it doesn t feel cold or hot Edition Number: 1.0 Released Issue Page 51

Procurement Guidelines: PART 4 Page 52 Released Issue Edition Number: 1.0

Procurement Guidelines: PART 5 PART 5 ENGINEERING GUIDELINES Edition Number: 1.0 Released Issue Page 53

Procurement Guidelines: PART 5 PART 5 ENGINEERING GUIDELINES 1. ENGINEERING GUIDELINES This section of the Voice Communication System (VCS) Procurement Guidelines addresses some of the technical requirements to be met by a VCS. In keeping with the overall purpose of these guidelines (as outlined in the Introduction to this document in Part 1: Section 1) only those matters considered to be of particular relevance are covered and this is not a full and comprehensive technical specification. Each of the parameters described in this Part will be classified as follows:- (General) - applicable to both Ground Telephone and Air Ground VCS (Telephone) - applicable to Ground Telephone VCS only (Radio) - applicable to Air-Ground VCS 1.1 Availability, Reliability and Maintainability (ARM) 1.1.1 Availability (General) Mean Time Between Failures (MTBF) The average interval of time that a component or system will operate before a service-affecting failure. Mean Time To Restore (MTTR) Average amount of time needed to repair/replace a component, recover a system, or otherwise restore service after a failure. NOTE: For guidance purposes a value of 15 minutes to replace a board/module and 1 minute for system recovery would be a reasonable performance figure for a modern VCS. Availability The availability of any system is simply defined as follows: MTBF Availability MTBF MTTR Page 54 Released Issue Edition Number: 1.0

Procurement Guidelines: PART 5 The availability of a VCS should be in excess of 99.999%. Modern technology makes this a realistic target for commercially available PBXs and terminal equipment. It should be noted, however, that the availability for Air-Ground services in terms of maintaining radio communications with aircraft is quoted as 99.99999%. This would not be realistically achievable with one VCS on its own. It can, however, be achieved by the use of autonomous standby or back-up VCS, transmission technology and radio equipment. As a 99,999 % availability figure is viable and realistic with today s commercially obtainable VCSs, it should be considered to what extent the availability of specific services contribute towards the availability of the overall VCS. For example guaranteed leased line availability is often defined at less than 98,5%. To achieve the necessary availability figures, stand-by and back-up features are an essential part of system design and configuration. 1.1.2 Reliability (General) The reliability of a VCS can be expressed in terms of the Mean Time Between Failures (MTBF) of individual Printed Circuit Boards (PCBs) but an MTBF for the overall system is probably more useful. The MTBF value will depend on the exact configuration installed but, as a guide, an MTBF in excess of 5 years would be reasonable for the complete loss of all telephony, voice and data services in a non-redundant (single central processor) VCS. 1.1.2.1 Reliability and System Redundancy (General) The reliability of a VCS is influenced significantly by the use of system redundancy. At a fundamental level, for example, individual external interface cards may be deployed in parallel so that in the event of a fault occurring in one of them the second one will continue to provide the service without any fault apparent to the User. This philosophy can be extended to the provision of duplicate processing for central control systems or even dual processors for autonomous multi-control systems. When requesting MTTR and MTBF figures from VCS suppliers, however, it is strongly recommended that the bases of these are clearly defined and also whether they have been sourced on actual performance data from products in the Field or by the use of analytical predictive techniques. The applied analytical predictive techniques and results should be documented in detail. Edition Number: 1.0 Released Issue Page 55

Procurement Guidelines: PART 5 1.1.3 Maintainability (General) The maintenance of a VCS will be greatly simplified if the system is capable of detecting and reporting any faults that occur in its component sub-systems (e.g., PCBs) and to indicate the impact on the system of any reported fault. Once identified, it should be possible to replace the faulty sub-system while the VCS continues to function. Maintainability should be viewed from both hardware and system software perspectives. 1.1.3.1 Hardware (General) Easy access to the following VCS components should be available: all PCBs; equipment shelves; line and power connections; test points; diagnostic displays and indicators. When system hardware changes need to be made (modifications or up-grades) it is important to know how this would be achieved, the time to carry it out and the full nature of any effects that the process may have on the operation and performance of the VCS. 1.1.3.2 Software (General) All software (and hardware) faults should be reported to the System Management Terminal (See Part 5: Section 1.4). A VCS should provide self-diagnostic capabilities, with the ability to detect failures, isolate defective modules, and take out of service any defective communication path or communication link. When system software changes need to be made (modifications or complete up-grades) it is important to know how this would be achieved, the time to carry it out and the full nature of any effects that the process may have on the operation and performance of the VCS. Furthermore the VCS should offer a means of changing back to previous software revisions if problems occur. Page 56 Released Issue Edition Number: 1.0

Procurement Guidelines: PART 5 1.2 General Response Criteria (General) In addition to determining the MTTR and MTBF figures as detailed in section 1.1.1 above other response criteria, as detailed below, should be determined as a means of assessing the performance of a VCS. 1.2.1 Call Processing Delay (Telephone) The delay incurred by a single VCS in processing a call event i.e., the time between the instant that a User request is accepted by the VCS and the instant that the associated response occurs. A User request should be accepted and indicated by VCS in less than 100ms. Call processing events include: call establishment; call acceptance; call release; call arrival. This requirement applies to the following call types: local terminal to local terminal; local terminal to line interface (call acceptance does not apply); line interface to local terminal. For guidance purposes a value of less than 200ms would be a reasonable performance figure for a modern VCS 1.2.2 PTT Set-Up Delay (Radio) In this safety-critical Air-Ground application this is delay that occurs from the instant the User activates his PTT key to the moment the transmitter (or transmitters) have been activated into a usable condition. In this end-to-end process the VCS is one of several components in series including the RCE, link and the transmitter. ANSPs have their own performance criteria for this and the performance of the VCS must be specified accordingly. Edition Number: 1.0 Released Issue Page 57

Procurement Guidelines: PART 5 As a guide, the delay between selecting PTT and the activation of the line interface should have a value of less than 10ms. 1.2.3 A/C call (Squelch) Delay (Radio) This is the delay from the moment of the receiver mute lift/squelch activation to the A/C call indication at the CWP. When this occurs, the speech path from the receiver through to the User s headset or loudspeaker must be assured. In a similar manner to PTT Delay defined in section 1.2.2 above, the performance of the VCS is only one part of an end-to-end process and will be specified by the ANSP. As a guide, the delay between the Squelch signal arriving at the VCS from the receiver to the audio activation at the CWP loudspeaker/headset, should have a value not greater than 10ms. 1.2.4 Dial Tone Delay (Telephone) The time between the instant that a terminal is detected by the VCS as 'off-hook' and the instant that dial tone (if used) is injected on the voice path. For guidance purposes a value of 30 ms would be a reasonable figure for a modern VCS. 1.2.5 Software response delay (General) This paragraph provides some indication of the parameters that should be considered when specifying the performance of VCS software. Typical values of some of these parameters are provided but they should not be considered to be firm requirements. 1.2.5.1 Alarm Indications Alarm indications should be guaranteed to be displayed and printed within a reasonable period of the occurrence of the related fault. Typically, this period should be less than 3s. 1.2.5.2 Configuration Changes The time taken to effect a change in the user configuration (telephone number, class of service etc.) should be no more than a few seconds (typically 10s). However, in VCS systems having user information stored at each of the user terminals, it would not be unreasonable for large data tables, such as the directory of users, to take up to 1 minute to be fully distributed. Page 58 Released Issue Edition Number: 1.0

Procurement Guidelines: PART 5 1.2.6 System Response Times (General) The sections above provide details of critical operational timing constraints such as call processing delay, but there are other, less critical timings, which if not met, may make CWP operation rather difficult. These include: Key response time (time between the activation of a key and the corresponding reaction on the HMI) which should not exceed 100ms; Action response time for non-critical applications (for example, setting up a destination address for call diversion) which should, typically, not exceed 3s; System start-up time, which should rapidly make the VCS operational after system power-up or a software restart. Typically, this should not take longer than 2 minutes. 1.2.7 Performance Conditions (General) The Delay figures as detailed above should be achieved under all operating conditions of the VCS including the specified full telephone traffic load, the specified maximum number of simultaneous incoming and outgoing radio calls and the maximum cross-coupled Radio Tx/Rx configuration. 1.2.8 Software (General) A specified type and revision of software should be declared for the ARM and all performance figures. It is worth checking that the software to be provided will meet the full telephone and radio capacity (traffic, Users and ports) without degradation in performance or for the cost of enhancements. VCS operational software at the time of procurement should have sufficient capacity available for future enhancements. Edition Number: 1.0 Released Issue Page 59

Procurement Guidelines: PART 5 1.3 Traffic Handling Capacity and Blocking 1.3.1 Traffic Handling (Telephone) For ATM applications the ability for a VCS to handle a specified amount of traffic is an important performance criteria. Two performance terms sometimes quoted and for easy reference definitions are given below: Bust Hour Call Attempts (BHCA) The number of attempted calls that a VCS can process successfully, during a single busiest hour of a typical day, to each active internal or external port. Blocking Probability The probability of a call attempt, either between internal Users or between internal and external Users, failing during the busiest hour of the day. 1.3.2 General Guidance on Non-Blocking Functionality (Telephone) Traffic handling capacity and blocking probability is a complex science and there are no universally accepted definitions. It is recommended, therefore, that a pragmatic approach be taken when obtaining such details from VCS suppliers or when including such details in a VCS specification. Any Traffic Handling and/or Blocking performance data should always be specified in accordance with all of the following conditions: The VCS at its maximum physical configuration (internal and external ports) For a quality controlled set of hardware and software revisions Under the conditions given above, the performance criteria stated in Part 5: Section 1.2 must be achieved (or the level of achievement specified). Care must be taken that not only is there sufficient time slot or matrix switching capability, but also that there is sufficient call processing power to handle them. Could for example call processing be effected by other routines such as system diagnostic panel reconfigurations? At a more fundamental level, is it possible that a call attempt may fail (or is delayed) due to the lack of tone generators / receivers? A VCS for operational ATC, when configured as detailed above, would simultaneously permit all users to establish calls without any degradation in performance. Thus Blocking Probability equals zero. A VCS for operational use should always be configured as non-blocking. Blocking may be acceptable in degraded mode. Page 60 Released Issue Edition Number: 1.0

Procurement Guidelines: PART 5 1.3.3 PTT and A/C call Blocking (Radio) The concepts of traffic handling and blocking, as detailed for the telephone applications in the section 1.3.2 above, can also be applied to radio for PTT and A/C call. Any blocking possibility is not acceptable. This should be clearly specified and VCS suppliers should be asked to explain, in depth, how their VCS design is compliant with the non-blocking and delay requirements. 1.4 System Management (General) A VCS should have connected to it one or more terminal devices which can be used for system management tasks. The Management Functions have been classified into five Management Functional Areas (as per ISO's OSI Management): (a) (b) (c) (d) (e) performance management fault (or maintenance) management configuration management accounting management security management The list of functions, its terminology and classification is based upon the work of ITU- T Recommendations M.3400 [22] and M.20 [21]. It is advisable to ask potential suppliers to demonstrate their system management to ensure that it is user friendly and to determine how long it takes to add new profiles and make moves and changes. 1.4.1 Performance management (General) Performance management provides functions to evaluate and report upon the behaviour of telecommunication equipment and on the effectiveness of the external links, network or VCS. Its role is to gather statistical data for the purpose of monitoring and correcting the behaviour and effectiveness of these and to aid in the planning and analysis phases. Performance management relates to the following set of functions: Performance monitoring: the collection of data concerning the performance of the VCS. Edition Number: 1.0 Released Issue Page 61

Procurement Guidelines: PART 5 Traffic Measurement: the collection of traffic data statistics from VCS. Traffic data reports may be sent upon threshold triggering, periodically or on demand. Status Monitoring Functions: - service availability of the VCS; - the status of controls; - line busy/idle status; - trunk congestion status. Control Functions Quality of service (QoS) observations 1.4.2 Fault (or maintenance) management (General) Fault management functions enable the detection, isolation and correction of abnormal operation of the telecommunication network and its environment. Fault management relates to the following set of functions: Alarm Surveillance: the capability to monitor failures in near real time. When a failure occurs, fault management determines the nature and severity of the fault and may also determine the effect of the fault on the services supported by the faulty equipment. Fault Location: the ability to augment the initial failure information by the use of additional failure localization routines. 1.4.3 Configuration management (General) Configuration management provides functions to exercise control over, identify, collect data from and provide data to a VCS. Configuration management relates to the following set of functions: Provisioning: procedures that are necessary to bring equipment into service. Page 62 Released Issue Edition Number: 1.0

Procurement Guidelines: PART 5 Re-configuration procedures that are necessary to adapt User-facilities like frequencies, DA-key etc. to the actual traffic situation. With particular regard to user configuration management, a common requirement is to be able to build and store a particular combination of ground telephone and radio frequency assignments in accordance with a particular operational role or mission. Roles may be assigned to a particular CWP by the System Management Terminal or invoked by the User. Status and control: The capability to monitor and control certain aspects of the VCS on demand. Examples include checking or changing the service state of VCS sub-parts (in service, out of service, stand-by) and initiating diagnostics tests. When associated with failure conditions, these functions are corrective. Status and control functions can also be part of routine maintenance when execute automatically or on a scheduled periodic basis. Installation: the extension or reduction of system hardware and software components. An important aspect of this function is the ability to make modifications to the configuration while the VCS continues to operate. 1.4.3.1 Configuration of telephone and Radio Access keys (General) Configuration management should permit the multiple assignment of an Access key appearance on more then one CWP. 1.4.3.2 Alpha-numeric identification labels (Telephone) In order to facilitate the presentation of a caller's identity as an alpha-numeric string (for example, caller's name or operational identifier) rather than simply digits representing the caller's ATSN number, it should be possible to associate an external number with an alpha-numeric string which can be substituted when a call arrives from that source. Edition Number: 1.0 Released Issue Page 63

Procurement Guidelines: PART 5 1.4.3.3 Physical configuration parameters (General) Because VCS installations will differ in terms of the number of controllers supported and the traffic expected to be handled, it is not possible to specify fixed dimensions for the provision of common equipment resources. However, the parameters identified in Table 4 should be considered and specified according to the overall requirements of the system. Table 4: Physical configuration parameters Parameter Tel Radio Number of system ports Maximum number of trunks Maximum number of radio frequencies Maximum number of digital trunks Maximum number of CWPs Maximum Number of simultaneous voice paths 1.4.3.4 Allocation of "A" side and "B" side (Telephone) For each ATS-QSIG and ATS-R2 link supported by a VCS, it should be possible to configure the VCS as the "A" side or the "B" side for call processing purposes (for example, for the resolution of call collisions). NOTE: Although there is no impact on the VCS itself, it is recommended that to ensure consistency within the ATSN, the allocation of "A side and "B" side status on each link is based on the ICAO Location Indicators (ordered alphabetically) as illustrated in the following example. Page 64 Released Issue Edition Number: 1.0

Procurement Guidelines: PART 5 Madrid LEAC A side B side Lisbon (Mil) LPAM A side B side B side Bordeaux LFBD A side Figure 1: Example of allocation of "A" and "B" Side using ICAO Location Indicators 1.4.3.5 Recovery after system failure (General) On recovery from loss of power to a VCS or any other fault causing an interruption to service, the VCS should be returned to the configuration established prior to the failure or, if this is not possible, to a predefined configuration. 1.4.4 Accounting management (Telephone) Accounting management provides a set of functions which enables the use of the network service to be measured and the costs for such use to be determined. Accounting functions relate to the following activities: (a) (b) collect accounting records set billing parameters for the usage of services In a private network such as the ATSN, it is unlikely that there will be a significant requirement for accounting management services. However, the use of Virtual Private Network (VPN) services in the future could make the information provided by accounting management more important. Edition Number: 1.0 Released Issue Page 65

Procurement Guidelines: PART 5 1.4.5 Security management (General) Security management provides the functions necessary to ensure adequate security of the installation and the prevention of misuse of a VCS by unauthorised users that compromises the operational integrity. Administrations will need to establish and implement a robust security policy. Safeguards are necessary to protect their own air traffic management as well as other (external) users. This section relates to the security of all systems and services that contribute to the provision of VCS services. Security can be considered from the perspective of three general categories: physical security, system security and network security. They are discussed in the following sections. 1.4.5.1 Physical security Appropriate physical security measures, similar to those usually employed throughout facilities associated with the management of air traffic, should be taken to protect the areas and systems used to provide communications services. All areas of the communications system (including VCS, transmission links, public switched telephone network links and the related power supply, network management and maintenance centres) should be considered as being vulnerable to physical tampering including electrical or electronic attack. Where it is possible for an administration to do so, the following is a list of measures that can be taken to reduce the effect of physical damage: a) duplicate equipment; b) physically split systems; and c) separate environments/locations for equipment with independent power and other services. Of particular importance are those areas where the external communications services are provided including patch bays, line transmission equipment and external cable ducts. In cases where there is no alternative to the use of a single service provider consideration should be given to connecting to completely separate network access points via completely separate physical routes. The ideal is to mitigate against the effects of all common points of potential failure. Consideration of the consequences of loss of service due to physical effects should also be extended to the operational level and planned in conjunction with the users. It might be possible for one user or CWP to provide contingency services for another user or CWP but this could be severely impaired if the contingency was due to the loss of a link they both shared. Page 66 Released Issue Edition Number: 1.0

Procurement Guidelines: PART 5 1.4.5.2 System security Within this category all items of communications equipment within a particular operational location are included, such as VCS, and line transmission equipment. Where many items of equipment are physically interconnected steps need to be taken to prevent either deliberate or inadvertent unauthorised access to operational VCSs and external links. VCSs should, ideally, provide support for identification and authentication of authorised users; in particular, management and maintenance personnel. Mechanisms to prevent misuse of the trunk network by unauthorized users (i.e., call barring) should also be provided. 1.4.5.3 Public Network security VCSs may have interfaces to the public switched telephone network (PSTN) to permit calls to be made to destinations outside the ATS ground voice network to provide link back-up or simply as an alternative to the leased line scenario. This functionality must be restricted to ensure that external callers cannot gain access to trunk lines used for operational air traffic management. 1.5 Modularity (General) 1.5.1 General guidelines While there is no essential requirement for a VCS to be designed and built in a modular fashion, consideration should be given to its physical design as a system that has a high degree of modularity is likely to have distinct advantages over one which does not. These advantages include: greater resilience to the effects of partial system failures; easier extension of the system to accommodate increases in the number of users; easier maintenance. 1.5.2 System Modularity for Security Part 2: Section 3 introduces the concept of a combined Ground Telephone and Radio VCS. Whereas this is a common configuration some ANSPs prefer to have separate systems to avoid as far as possible the simultaneous failure of both. The concept can be extended for a single type of VCS where it may be physically dispersed in modules to be secure against common environmental catastrophes (fire & flood etc). Such systems must have the type of architecture that supports physical separation of the modular part but also gives the appearance (particularly to Users) that it is one integrated system. In these case the modules may be linked by proprietary signalling systems, external busses or even by use of Wide Area Networks. It is important in Edition Number: 1.0 Released Issue Page 67

Procurement Guidelines: PART 5 these cases to ensure that any failures (maybe due to physical damage) in the link systems does not have an adverse affect on the operation of the individual modules. 1.6 Accessibility (General) The physical design of the system should permit ease of access to all hardware modules for the purpose of replacement or testing. It should also be possible to remove and replace any hardware module without the need to interrupt operation of the VCS system. 1.7 Safety and protection (General) The VCS equipment should be designed to meet the requirements of EN 60950 [17] and its Amendments. 1.8 Electromagnetic Compatibility (EMC) (General) VCS equipment intended for use in Member States of the European Union (EU) must meet the general requirements for EMC imposed by Directive 89/336/EEC on the approximation of the laws of the Member States relating to electromagnetic compatibility (the "EMC Directive"). It is recommended that VCS equipment intended for use in countries other than those of the EU should also meet these requirements. Bearing in mind the general environment in which it is normally expected to operate, VCS equipment must also be capable of operating in the close proximity of high-power radar transmitters. 1.9 Synchronisation Strategy (General) Synchronisation is particularly important when VCSs are to be linked together by use of digital signalling systems such as ATS-QSIG (See Part 5: Section 1.10.4.2) Synchronisation with RCE and Tx/Rx site links are equally important. Some general guidance is given below but it is strongly recommended that the VCS supplier be contracted to ensure correct and stable synchronisation in the particular network configuration in which the VCS will be used. As a general rule, all digital VCSs should be included as part of a complete synchronisation scheme where each external digital interface within a VCS is designated to be either the source of synchronisation or to receive synchronisation. Page 68 Released Issue Edition Number: 1.0

Procurement Guidelines: PART 5 A VCS can select only one of its digital interface cards at a time to be its source of synchronisation (Synch Master), in which case all other interface cards must be configured to receive synchronisation (Synch Slave). The Synch Master interface must be connected to a selected external source of synchronisation, which is often a PTO digital service. Synchronisation provided by PTO digital services (digital circuits and ISDN/PSTN services for example) may not, however, provide the degree of reliability required in which case the use of a dependable and highly-accurate time system - possibly backed by GPS for example - should be considered. In the event of temporary loss of external synchronisation the VCS must have its own internal clock (or clocks) to maintain system operation. A VCS with an internal clock accuracy of ±1.10-6, commonly used in commercially available equipment, would not normally meet the requirements of complex infrastructure transmission systems for ATC use. As a result periodic buffer slips can occur resulting in clicks being heard in the voice channel during quiet periods. More significantly, however, loss of synchronisation (for whatever reason) can have severe effects on the intelligibility of speech thus any consequential safety hazards should be carefully evaluated. A VCS with an internal clock accuracy of better than ±1.10-6 is therefore recommended. Further guidance on synchronization strategies is given in ISO/IEC 11573 [19] Any change in the synchronisation status of the system or in the status of the clock source should be recorded in the system's event log and cause a prominent alarm in the System Management Terminal. 1.10 Line Interfaces (Telephone) 1.10.1 General It is essential that the VCS will be capable of supporting a number of external interfaces as follows: legacy interfaces public switched network interfaces; inter-vcs circuit interfaces; 1.10.2 Legacy Interfaces The types of legacy interfaces that may need to be supported by a new VCS is outside the scope of these guidelines. It can only be recommended that some consideration be given to the economics of continuing with such interfaces along with the need to support the User facilities detailed in Part 3 as well as the objectives of the ATM Strategy For The Years 2000+ [1]. Edition Number: 1.0 Released Issue Page 69

Procurement Guidelines: PART 5 1.10.3 Public network interfaces The VCS will need to interface to the Public Switched Telephone Network (PSTN). It is recommended that information on the technical requirements for PSTN access be sought from the local service providers. It is further recommended that PSTN access be considered along with the wider benefits of DSS1 (Euro-ISDN) services rather than to opt for solely analogue solutions. For easy reference the following are the current analogue and ISDN Standards: 2-Wire Analogue Interface EN 300 001 [10] "General technical requirements for equipment connected to an analogue subscriber interface in the PSTN." Basic Access ISDN (2B+D) European Standards Layer 1 EN 300 012-1 [12] Layer 2 ETS 300 402-2 [14] Layer 3 EN 300 403-1 [15] "Integrated Services Digital Network (ISDN);Basic User-Network Interface (UNI);Part 1: Layer 1 specification" "Integrated Services Digital Network (ISDN); Digital Subscriber Signalling System No. one (DSS1) protocol; Data link layer; Part 2: General protocol specification" "Integrated Services Digital Network (ISDN); Digital Subscriber Signalling System No. one (DSS1) protocol; Signalling network layer for circuit-mode basic call control; Part 1: Protocol specification" Primary Rate ISDN (30B+D) European Standards Layer 1 EN 300 011-1 [11] Layer 2 ETS 300 402-2 [14] "Integrated Services Digital Network (ISDN); Primary rate User Network Interface (UNI); Part 1: Layer 1 specification" "Integrated Services Digital Network (ISDN); Digital Subscriber Signalling System No. one (DSS1) protocol; Data link layer; Part 2: General protocol specification" Page 70 Released Issue Edition Number: 1.0

Procurement Guidelines: PART 5 Layer 3 EN 300 403-1 [15] "Integrated Services Digital Network (ISDN); Digital Subscriber Signalling System No. one (DSS1) protocol; Signalling network layer for circuit-mode basic call control; Part 1: Protocol specification" 1.10.4 Inter-VCS Circuit Interfaces The Primary User Telephone Facilities (Part 3: Sections 1.1 to 1.5) and the external interfaces (Inter-VCS Circuit Interfaces) are the key to meeting the Ground Telephone VCS requirements in support of the ATM Strategy For The Years 2000+ [1] and the associated Communications Strategy [2]. This section of the guidelines gives recommendations on the types of circuits to be used and further details of how they may be used to meet the Primary User Requirements. There are two current analogue signalling systems ATS-R2 and ATS-No5 and one digital signalling system based on the EN 301 846 standard [16] and commonly known as "ATS-QSIG". 1.10.4.1 Analogue Signalling Systems ATS-R2, ATS-No5 These two analogue signalling systems are described in detail in the EATCHIP document COM-GUI-01-01, "Guidelines For The Implementation Of The Automatic ATS Voice Communication Network" [4] together with further guidance on analogue network planning. ATS-R2 is the preferred analogue signalling system for ground networks whereas ATS-No5 is for use where satellite links may be involved. COM-GUI-01-01 details inter-working between the two. ATS-R2 may be used to support the Primary User Telephone Facilities as detailed in Part 3: Sections 1.1 to 1.5, (excluding 1.3.2 Instantaneous access ), but care must be taken on achieving the required performance parameters where multiple links and transits are involved. The signalling system supports the Priority Facility (see Part 3: Section 1.4). 1.10.4.2 Digital Signalling System EN 301 846 "ATS-QSIG EN 301 846 (ATS-QSIG) is the Eurocontrol preferred digital signalling system for the future and it is strongly recommended that this should be deployed wherever possible. If there is not an immediate justification for the use of ATS-QSIG either on Operational or financial grounds then it is strongly recommended that this should be included as a future option in any new VCS procurement. ATS-QSIG supports all of the Primary User Telephone Facilities as detailed in Part 3: Sections 1.1 to 1.5 (excluding 1.3.2 Instantaneous access ), but as for ATS-R2, care will need to be exercised to ensure that the performance criteria are achieved. Edition Number: 1.0 Released Issue Page 71

Procurement Guidelines: PART 5 Safety and Hazard Warning The reader's attention is also drawn to the existence of the safety and hazard warning in Part 3: Section 1.5 regarding the resolution of Simultaneous Calls. ATS-R2 Gateways - Interworking It is likely that a VCS may need to provide a gateway to existing MFC analogue circuits details of which can be found in the Eurocontrol document "Interworking Between ATS QSIG and ATS R2" [5]. 1.11 Numbering Schemes (Telephone) It is recommended that a VCS should support the following existing user numbering schemes: a) EN 300 189 [13], "Private Integrated Services Network (PISN); Addressing" b) 6 digits as defined in the Eurocontrol document "Guidelines For The Implementation Of The Automatic ATS Voice Communications Network" [4]. Each extension user may be allocated one or more unique numbers within the scope of the VCS numbering scheme. 1.12 Standby VCS Requirements (General) Part 5: Section 1.1 deals with the Availability of a VCS from the ARM perspective and it is possible by use of modular techniques (Part 5: Section 1.5) to safeguard to a certain extent against a total loss of a VCS service. ANSPs, however, define the availability of a particular ATM service and the VCS availability may be one component of this. This concept may be illustrated by reference to a controlled airspace Sector within an ATC Centre and the probability of not being able to maintain separation by means of the Radio facilities for that Sector. Readers are recommended to contact the Regulatory and Safety Authorities within their State for details of the actual probabilities and associated ATM availability (although the EC and Eurocontrol are currently working on common standards). One way of attempting to reduce the effects of VCS failures on the ability to perform ATM is to deploy standby or back-up VCSs along with the main system the availability to a given Sector is thus far higher than could otherwise be achieved. The general principles to be followed are outlined below. Page 72 Released Issue Edition Number: 1.0

Procurement Guidelines: PART 5 Standby VCSs should be separate from the main equipment and utilise separate power as far as possible and all dependent support systems and services. Standby systems may have limited and basic functionality. Standby systems may to be of a different type to the main systems thus avoiding insidious common software and/or hardware faults because of the identical stimulation of possible faults. Standby systems should be located in different rooms 1.13 Call and event recording (General) The following sections give some guidance on speech recording and the logging of events but should be used only in the context of clearly defined procedures for the control, safe keeping and management of the data. 1.13.1 Radio and Telephone voice recording The recording of radio communications is mandated by ICAO and it is strongly recommended that at all times it should be possible, by means of equipment which is either integral to the VCS or connected externally to the VCS, to record simultaneously the audio signals (speech) from every active radio frequency on the VCS. Some ANSPs also extend this to include all voice communications. It must be possible to replace recording media devices (for example, a magnetic tape) without loss of audio information. Sufficient additional information should be recorded to ensure that the date and time (to the nearest second) could be determined at any point in the recording of any call. It should be possible to derive this date and time information from an external master reference source and, in the absence of this, an internal source. 1.13.2 Telephone Call event recording (Telephone) It should be possible to use system management procedures to enable call and event recording for any number of extension or trunk lines connected to the VCS. Recording may be enabled either for all calls or for incoming or outgoing calls on a selective basis. Call records should be sent to an external recording device (for example, magnetic tape recorder or CD writer) for subsequent processing and analysis. It should also be possible to print the recorded information in a tabular form. Call event times should be recorded as the current date with the time of day in hours, minutes and seconds. It should be possible to derive this date and time information from an external master reference source and, in the absence of this, an internal source. Edition Number: 1.0 Released Issue Page 73

Procurement Guidelines: PART 5 1.13.2.1 Outgoing call information The following information should be recorded for all outgoing calls: call origination address; call start time (off-hook); call destination address; call result: - no reply; - user busy; - number unobtainable; - network congestion; time of answer (if applicable); call end time (hang-up); line/trunk used; answered; priority level. NOTE: Instead of recording call start time and call end time, it is possible to record call start time with call duration. However the use of start and end times is the preferred method. As an implementation option, the following information may also be recorded for all outgoing calls: charges incurred during the call; service(s) invoked by the caller; service(s) invoked by the called user. 1.13.2.2 Incoming call information The following information should be recorded for all incoming calls: call destination address; call arrival time (start of alerting); call origination address; Page 74 Released Issue Edition Number: 1.0

Procurement Guidelines: PART 5 call result: - answered; - no reply; time of answer (if applicable); call type: - simple call; - transferred call; - diverted call; - conference call; transferring user's address (if applicable); diverting user's address (if applicable); conference parties' addresses; call end time (hang-up); line/trunk used; priority level. NOTE: Instead of recording call start time and call end time, it is possible to record call start time with call duration. However the use of start and end times is the preferred method. As an implementation option, the following information may also be recorded for all incoming calls: service(s) invoked by the caller; service(s) invoked by the called user. 1.13.3 Radio Call event recording It should be possible to use system management procedures to enable call event recording for any number of radio lines connected to the VCS. Call records should be sent to an external recording device (for example, magnetic tape recorder or CD writer) for subsequent processing and analysis. It should also be possible to print the recorded information in a tabular form. Call event times should be recorded as the current date with the time of day in hours, minutes and seconds. It should be possible to derive this date and time information from an external master reference source and, in the absence of this, an internal source. Edition Number: 1.0 Released Issue Page 75

Procurement Guidelines: PART 5 1.13.3.1 Outgoing call information The following information should be recorded for all outgoing radio calls (PTTactivation): CWP/Role-identification Channel identification Date and time Duration 1.13.3.2 Incoming call information The following information should be recorded for all incoming radio calls (A/C call or Squelch signal): Channel identification Date and time Duration Signal quality indicator (where available) 1.13.3.3 Best Signal Selection To optimise radio coverage often several Tx/Rx-locations with an identical nominal frequency are used (Part 3, 2.1, 2.2). An ANSP may employ best signal selection technology to present only the best radio channel to the user. The following information should be recorded for all incoming radio calls: Channel identification Frequency Date and time Page 76 Released Issue Edition Number: 1.0

Procurement Guidelines: PART 5 2. CONNECTION APPROVALS REQUIREMENTS All telecommunications interfaces supported by a particular VCS must comply with the connection approval regulations which apply in the country in which the VCS is to be installed. 3. TRAINING There are four training aspects related to the operation of a VCS for which training is recommended. training in the operation and management of the VCS itself; controller development and ATC procedural training facilities provided by the VCS; reference documentation for use by controllers and maintenance staff; maintenance training. The requirement for Student / Mentor facilities has already been covered in Part 4: Section 1.4. Within the context of this document it is assumed that expert advice will be available to assist with the definition of training requirements. 4. DOCUMENTATION There are several aspects related to the documentation of the operation of a VCS for which different kinds of manuals and preparation materials are needed. For example: native language user manuals for "operational services"; native language user manuals for "management services"; user manuals for service and maintenance; VCS hardware documentation; VCS software documentation; installation documentation; infrastructure documentation; transition documentation. Edition Number: 1.0 Released Issue Page 77

Procurement Guidelines: APPENDICES APPENDICES Page 78 Released Issue Edition Number: 1.0

Procurement Guidelines: APPENDICES ANNEX A REFERENCES For the purposes of this document, the following references apply: 1 Eurocontrol: "Air Traffic Management Strategy for the Years 2000+", Volumes 1 and 2 2 Eurocontrol: "EATMP Communications Strategy" (ECS_V1_E3.0 and ECS_V2_E4.0) 3 Eurocontrol ASM.ET1.ST18.1000-REP-01-00: "Guidelines for the application of the ECAC Radar Separation Minima" 4 Eurocontrol COM-GUI-01-01: "Guidelines for the Implementation of the Automatic ATS Voice Communication Network" 5 Eurocontrol: "Inter-working between ATS QSIG and ATS R2" 6 Eurocontrol: "MFC guidance manual" 7 ICAO Convention on International Civil Aviation, Annex 10, Volume III, Part II, Chapter 4: "Aeronautical Speech Circuits" 8 ICAO Convention on International Civil Aviation, Annex 11, Chapter 6: "Air Traffic Services Requirements for Communications" 9 ICAO: "Manual on Air Traffic Services (ATS) Ground-To- Ground Voice Switching and Signalling" 10 EN 300 001: "General technical requirements for equipment connected to an analogue subscriber interface in the PSTN" 11 EN 300 011-1: "Integrated Services Digital Network (ISDN); Primary rate User Network Interface (UNI); Part 1: Layer 1 specification" 12 EN 300 012-1: "Integrated Services Digital Network (ISDN); Basic User-Network Interface (UNI); Part 1: Layer 1 specification" 13 EN 300 189: "Private Integrated Services Network (PISN); Addressing" 14 ETS 300 402-2: "Integrated Services Digital Network (ISDN); Digital Subscriber Signalling System No. one (DSS1) protocol; Data link layer; Part 2: General protocol specification" Edition Number: 1.0 Released Issue Page 79

Procurement Guidelines: APPENDICES 15 EN 300 403-1: "Integrated Services Digital Network (ISDN); Digital Subscriber Signalling System No. one (DSS1) protocol; Signalling network layer for circuit-mode basic call control; Part 1: Protocol specification" 16 EN 301 846: "Profile Standard for the Use of PSS1 (QSIG) in Air Traffic Services Networks" 17 EN 60950: "Safety of information technology equipment" 18 ISO/IEC 7498-4: "Information processing systems -- Open Systems Interconnection -- Basic Reference Model -- Part 4: Management framework" 19 ISO/IEC 11573: "Information technology -- Telecommunications and information exchange between systems -- Synchronization methods and technical requirements for Private Integrated Services Networks" 20 ITU-T Recommendation Q.35/E.180: "Technical characteristics of tones for the telephone service" 21 ITU-T Recommendation M.20: "Maintenance philosophy for telecommunication networks" 22 ITU-T Recommendation M.3400: "TMN management functions " Page 80 Released Issue Edition Number: 1.0

Procurement Guidelines: APPENDICES ANNEX B ABBREVIATIONS For the purposes of this document, the following abbreviations apply: A/C ANSP ARM ATC ATM ATS ATSN BHCA BSS COMT CRT CWP DA DC DCCVC COMT DSS1 EC ECAC ECMA EMC ETSI FBU HMI HMT IA ICAO ICCVC IDA ISDN ISO ITU-T LCD LED MFC MTBF MTTR OSI PBX PC PCB PSS1 PSTN Aircraft Air Navigation Service Provider Availability, Reliability and Maintainability Air Traffic Control Air Traffic Management Air Traffic Services Air Traffic Services network Busy Hour Call Attempt Best Signal Selection Communications Team Cathode Ray Tube Controller Working Position Direct Access Direct Current Direct Controller-Controller Voice Communication Communications Team Digital Subscriber Signalling No. 1 (ISDN) European Community European Civil Aviation Conference An international industry association dedicated to the standardisation of information and communication systems Electro-Magnetic Compatibility European Telecommunications Standards Institute Flight Briefing Unit Human Machine Interface Hand Microphone Telephone Instantaneous Access International Civil Aviation Organization Indirect Controller-Controller Voice Communication InDirect Access Integrated Services Digital Network (DSS1) International Standards Organization International Telecommunication Union Telecommunication Standardization Sector Liquid Crystal Display Light Emitting Diode Multi Frequency Code Mean Time Between Failures Mean Time To Restore Open Systems Interconnect Private Branch exchange Personal Computer Printed Circuit Board Private Signalling System No. 1 (QSIG) Public Switched Telephone Network Edition Number: 1.0 Released Issue Page 81

Procurement Guidelines: APPENDICES PTO PTT QoS QSIG RCE RX SC TX VCS VCS-TF VPN Public Telecom Operator Push To Talk Quality of Service Q-reference point signalling (PSS1) Radio Control Equipment Receiver Simultaneous Call Transmitter Voice Communication System VCS-Task Force Virtual Private Network Page 82 Released Issue Edition Number: 1.0

Procurement Guidelines: APPENDICES ANNEX C - REFERENCE MODEL EXAMPLE FOR THE MANAGEMENT OF INCOMING CALLS C.1 Introduction This annex describes how incoming calls should be managed on a VCS in order to make the optimum use of the telephone facilities described in Part 3: section 1.1 as well as to ensure uniformity and compatibility in their operational deployment. Figure 2 below shows three fundamental elements of the VCS HMI Telephone Panel used for the management of incoming calls. This arrangement has been produced as a Reference Model in order to explain the principles involved and should not be taken as a recommendation of any criteria for the HMI, which would be supplier dependent. Calls stacked in sequence IDA Call Queue DA Key Matrix IA Key Matrix Figure 2: Telephone Panel Reference Model The User is provided with three incoming call displays as follows: (a) (b) (c) A stacked IDA call queue An matrix of 16 keys in a DA panel An matrix of 8 keys in a IA panel The typical use of each of the above incoming call displays is described below with reference to visual alerting attributes and Operational procedures. Edition Number: 1.0 Released Issue Page 83

Procurement Guidelines: APPENDICES C.1.1 IDA Call Queue In the reference model example, incoming calls are displayed in sequential order with the first call at the bottom of the stack. Calls are displayed with their 'A'-party identity (as detailed in Part 3: section 1.3.3) and are in a ringing condition until answered by the User. Calls can be answered in any sequence chosen by the User. Up to 6 calls may be presented here in any of the following conditions: (a) (b) (c) Ringing not answered Answered and in use Answered and placed on hold A seventh ROUTINE incoming call addressed to the call queue would receive BUSY in the event that all-available spaces in the stack were occupied (i.e. queue full) by one of the above types of call. The Call Queue is used, primarily, for the management of incoming IDA calls. An IDA PRIORITY call would be presented in the stack with some sort of distinctive audio/visual indication so that the User could easily identify it as such. If the User is already in conversation with any other sort of telephone call, the VCS should provide an option (activated via the System Management Terminal), for the PRIORITY call to intrude in this call as detailed in Part 3: section 1.4.1 and within the constraints detailed in Part 3: section 1.4. An IDA PRIORITY call encountering a full queue would similarly have the capability to displace and replace the last unanswered ROUTINE call to arrive. In this event the 'A'-party should be given busy tone, subject to the signalling system in use. C.1.2 The DA Panel The DA panel is used to make and receive up to 16 DA calls by means of the matrix of keys. Incoming DA calls will be presented with the 'A'-party identity as detailed in Part 3: section 1.3.1. The User may answer DA calls in any order and the calls may be in any of the following conditions: (a) (b) (c) Ringing not answered Answered and in use Answered and placed on hold A DA PRIORITY call would be presented at the key with some sort of distinctive audio/visual indication so that the User could easily identify it as such. If the User is already in conversation with any other sort of telephone call, the VCS should provide an option (activated via the System Management Terminal) for the PRIORITY call to Page 84 Released Issue Edition Number: 1.0

Procurement Guidelines: APPENDICES intrude in this as detailed in Section 1.4.1 and within the constraints detailed in Section 1.4. Under exceptional circumstances (such as a fault condition, deliberate diversion) a DA call may be presented on the IDA Call Queue in which case it should be indicated, distinctively, as a DA call. A PRIORITY DA call would be managed in the same way as a PRIORITY IDA call. C.1.3 The IA Panel The IA panel is used to receive (or make) up to 8 IA calls by means of the matrix of keys. Incoming IA calls will be presented with the 'A'-party identity as detailed in Part 3: Section 1.3.2 and upon arrival they are answered automatically 1 by the VCS as detailed in Section 1.3.2. IA Calls should always be sent with PRIORITY to protect them as much as possible if they are conveyed via a voice network with potential blocking. But this does not cause any special reaction at the 'B'-party VCS since, by definition, IA calls are already treated as urgent. 1 Auto answer is not the same as intrusion which is a Supplementary Service applicable only to established calls. Edition Number: 1.0 Released Issue Page 85