Low-cost User Interface Design for Supplementary Services

Low-cost User Interface Design for Supplementary Services Matthias Schneider-Hufschmidt and Martin Böcker Siemens ICP CD TI 3, Hofmannstr. 51, 81359 Munich, F.R. Germany. msch@mch.siemens.de, martin.boecker@mch.siemens.de Abstract The users of European communications networks are offered nowadays supplementary services ("CLASS services") in analogue networks that were previously available only in digital networks (ISDN). For making use of these ISDN-features, a number of specially designed telephone terminals is available most of which are at the high-end price segment. This paper reports about a user interface (UI) design project that aimed at developing a low-cost terminal with CLASS-functionality. The experiences and lessons learnt during this design process may also benefit other design projects. Class services in analogue networks Digital telecommunications networks (e.g. the ISDN) are promoted for their higher data throughput (compared to the Public Switched Analogue Network, PSTN) as well as for the large number of supplementary services they allow. Recently, most European telephone network operators have started to offer for their analogue networks supplementary services (CLASS-functions) that previously were only available for the ISDN, including Call Waiting (CW), Call Forwarding (diverting, CF), and the Calling Line Identification Presentation (CLIP). Analogue telephones that fully support these network features have so far been placed in the higher end of the price range. Network operators put the challenge to Siemens to develop a low-cost telephone that supports the above mentioned features at only minimum additional costs and offering an acceptable level of usability to the users. Framework for the UI-design process The basis for the new telephone was the Siemens Euroset 815S, a corded analogue telephone with a one-line, 7-segment display and an additional icon line and with handsfree functionality (see Fig. 1). The user interface (UI) design process for the new Siemens Euroset 815SC was conducted within the limitations of several tough constraints. Keeping changes to a minimum As few changes as possible were to be made to the existing telephone (Euroset 815 S). In particular, the design of the upper casing including the key layout were not supposed to be altered. The 815 S has the standard 12-key keypad, nine preset function keys (Save settings, Telephone lock, Time settings, Hook flash, Redial, Microphone on/off, Volume up, Volume down, and Loudspeaker on/off), and two rows with a total of 16 programmable function keys used for direct dialling (quick dialling). Adding new functionality 1

To accomodate the additional CLASS-functions, the number of functions had to be increased considerably. 14 CLASS-functions and a missed calls list had to be added to the already existing functionality: Recall on busy (CCBS) Voice Mail (Answerphone in the network) Fixed call Anonym. Call (CLIR) Call waiting (CW) Transfer Forward. gen. off 3 party conf. (three party conference) Forward. no reply (CFNR) Altern. Corresp. (Call swap) Forward. on busy (CFB) Take 2 nd Call (Accept waiting call) Forward. direct (CFU) Reject 2 nd Call (Reject waiting call) Minimising changes to the display No substantial changes could be made to the display. Therefore, the UI-design had to accommodate the additional functionality with the 16 digit, 7-segment display and an additional icon line. No text-based dialogues (menus, prompts) could be realised. Display Speaker 12-Keypad Direct Dialling Keys FFunction Keys Fig. 1: The User Interface of the Euroset 815 S Keeping software resources to a minimum Due to memory limitations, additional requirements on software resources had to be kept to an absolute minimum. Allowing the indication of feature states Unlike the ISDN, analogue networks do not return feedback messages during CLASSfunction calls that can be interpreted by the terminal. In analogue networks, these are given aurally (spoken message or tones) to the user who, if necessary, has to "tell" the 2

interface about the outcome (e.g. activation of call forwarding not successful). This means that a mechanism for manual feedback to the telephone by the user has to be provided. The UI-Design of the Euroset 815 SC The key idea for the modification of the original phone is the use of two additional layers ( shift -keys) on the direct dialling key-set. These layers are distinguished semantically. Layer 1 (initiated by a green shift key) denotes positive actions (i.e. initiation and confirmation), Layer 2 contains negative actions (cancellation, deactivation). The original use of the direct-dialling keys remains unchanged. The UI designed on the basis of this key idea used the following approach (see Figure 3). Two dialogue keys for controlling CLASS features The bottom two of the 16 programmable keys for direct dialling were re-defined as dialogue keys: A green key for activating CLASS-functions. A second, red key for de-activating CLASS-functions. The two keys implement a shift-key functionality. If pressed directly after the green key, each of the remaining 14 programmable keys initiates a CLASS function. Otherwise they still function as direct-dialling keys. Functionality of dialogue keys In addition to initiating an activation / de-activation sequence, the dialogue keys are used to feed back to the telephone the success or failure of an attempted CLASSfunction setting (this so because, as mentioned above, the analogue network provides only auditory feedback about the outcome of the function which the telephone cannot interpret). E.g. the activation of Call waiting requires the sequence 1 : GREEN (for activate) CALL WAITING key Wait for network response GREEN (for positive feedback, the Call waiting active icon will appear in the display) or RED for unsuccessful attempt. The final key press of the green key is not necessarily required and will time out with the activation attempt being registered as successful by default. De-activation is performed accordingly starting the sequence with the red key. RED (for de-activate) CALL WAITING key Wait for network response GREEN (for positive feedback, the Call waiting active icon will disappear in the display) or RED for unsuccessful attempt. The dialogue keys are also used for dialogue pacing, i.e. the explicit completion of a dialogue step, is done using the green key (positive confirmation). E.g. the activation of Call forwarding on busy (CFB) requires the sequence: GREEN (for activate) FORWARD ON BUSY key Directory number of destination for diverted calls GREEN (for pacing to the next dialogue step) Wait for network response GREEN (for positive feedback, the Call forwarding active icon will appear in the display) or RED for unsuccessful attempt. Finally, the dialogue keys can be used the same way also for other terminal functions 1 It is worth noting that prior to all actions, the phone has to go off-hook because the phone receives its power through the subscriber line. 3

such as functions of the missed calls list. E.g. to call a number from the missed calls list: MISSED CALLS key (first entry is displayed) ( MISSED CALLS key for displaying the next entry in the list) GREEN (for displaying date and time of the last call) GREEN (for initiating a call to the number in the list). Prototype testing of the UI concept In order to further develop and evaluate the UI of the Euroset 815 CS, a software prototype 2 has been developed that offers most of the functionality described above (Fig. 2). It turned out that the resources invested in the development of the prototype were well-invested. To start with, the prototype was invaluable for fine-tuning the concept several flaws became obvious once the concept could be directly experienced. Furthermore, the prototype was subjected to expert-walkthrus which produced more valuable criticism and suggestions. Last but not least, the prototype successfully illustrated to the network operators the interface of the new telephone. Fig. 2: The User Interface of the Euroset 815 SC prototype Lessons learnt during the UI-Design During the design of the UI presented in this paper, we learnt a number of lessons that may be of value to others with similar design challenges. 2 The prototype has been developed by Peter Maly of Siemens ICP. 4

Manageability of the system Handling the single dialogue steps is fairly complex due to the limitations of the analogue network. This complexity can be made manageable for the user by means of a meaningful sequence of key presses. As few keys as possible should be used for this sequence, and the sequence itself should make sense intuitively any longer or less intuitive sequence will compare unfavourably with directly using the CEPT syntax, e.g. *21*08972212345#. For this reason, the interpretation of system feedback is very important. If, as in our case, feedback is fairly rudimentary (e.g. due to the characteristics of a low-cost display), the user dialogue is even more difficult to realise. A major advantage of our approach for the user is the fact, that most of the grammar of the CEPT syntax is irrelevant to use the system. To initiate a CLASS function the user has the direct-dialling keys preceded by hitting the red or green shift key, after the number has been dialled (e.g. for call forwarding), the same green key may be used instead of the #-key to signal the end of the dialling information. There is no need to remember function codes (like *21*) or the exact keypad sequence of the CLASS functions in question. Fig. 3: The User Interface of the Euroset 815 SC final product Default behaviour of the system In the light of the relatively high complexity of command sequences for CLASSfunctions, it is necessary to pre-define a large part of the functionality. In our design, the 5

normal case, i.e. the successful activation or de-activation of a function is timecontrolled (time-outs) or executed with the positive (green) dialogue key - the exception to this rule are user inputs (e.g. directory numbers for call forwarding). The user, therefore, has no need to memorise complex key sequences. System feedback A big problem with analogue networks is the lack of interpretable feedback. To ensure that the telephone still receives reliable information about the state of the function, the user has to "assist" the phone by providing network feedback, if necessary. The terminal works on the assumption that the (de-) activation of a CLASS-function was successful. In the exceptional case that it is not, the user can signal this to the phone by pressing the red dialogue key. This provides the basis for a reliable indication of the device and network states by means of icons in the display. Use of conventions One aspect of the design which accounts for the usability of the design is the fact that the design is partly based on conventions that are generally accepted in our society. The green key is used for actions that have a positive meaning ("activate", "continue", "more information", "confirm", etc.) whereas the corresponding red key has meanings like "reject", "de-activate", "back", "no success". We believe that the usage of these keys should be self-explanatory at least in Europe. One indication of the relevance of this principle is that the same logic could be applied to the operation of the missed-calls list: again, green has the meaning of "more information", "initiate return call", red stands for "back to the list", "terminate list handling". Icons vs. speech-oriented design A big problem for the present design was the fact that currently, no standardised symbols for supplementary telephone services exists. For this reason, text labels ("Call forwarding", etc.) had to be employed for the controls (i.e. for the keys) and abbreviations (e.g. CF for Call forwarding) for the indications in the display. This lead to the UI to appear somewhat overloaded. In addition, templates with key labels in languages other than English have to be provided. It may pay of for this type of devices to establish a set of standardised symbols in order to simplify the UI. Outlook During the UI-design of most dedicated devices, there almost inevitably comes the time, when the functionality cannot be realised with an existing UI in a way that makes sense to the user. In such a situation, the UI-designer has essentially two choices. The first one is to reduce the functionality to what can be represented in a meaningful way. If this is not acceptable, it is necessary to leave the known approaches and study alternative UIdesigns. The principle of the solution proposed above is known from other consumer electronics products but has to our knowledge not yet been employed for a telephone. On the other hand, this dialogue principle can also be transferred to devices from other areas such as remote video surveillance. The key feature of our approach is its great simplicity, both for the user as well as for the software developer. This is why we were successful in developing a screen-based prototype with sufficient functionality for basic usability testing (results of usability testing will be available for the detailed version of the paper). To overload a simple consumer product with a large number of functions will always 6

remain a dubious endeavour and will always produce a sub-optimum solution in terms of its usability. A careful design of the user actions and a self-explanatory transfer of these actions on the keypad of the device can considerably increase the acceptable number of functions. Literatur [1] Nielsen, Jacob. Usability Engineering. Boston: AP Professional Press, 1993. 7