# DEFINITIONS TERMS. 3) Considered as transmission medium. Trench. 5) Modulates a sine wave carrier. I Channel Bits

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1 CHAPTER 11 DIGITAL T-CARRIERS AND MULTIPLEXING # DEFINITIONS TERMS 1) Transmission of information from one or more source To one or more destination over the same transmission medium (facility). 2) Unsophisticated form of multiplexing that simply constitutes propagating signals from different sources of different cables that are contained within the same trench. Space-Division 3) Considered as transmission medium. Trench 4) Form of phase-division multiplexing (PDM) where to date channels (the I and Q) modulate the same carrier frequency that has been shifted 90 in phase. QPSK 5) Modulates a sine wave carrier. I Channel Bits 6) Modulates a cosine wave carrier. Q Channel Bits 7) Three most predominant methods of multiplexing signals. Time-Division ; Frequency-Division ; Wavelength-Division 8) Transmissions from multiple sources occur on the same but not on the same time. Time-Division 9) Most prevalent encoding technique used for TDM digital signals. PCM Prepared By : MA. ELAINE L. CORTEZ 71

2 10) Use an 8-kHz sample rate and an eight-bit PCM code, which produces a 64 kbps PCM line speed. DS-O Channel 11) Simply an electronically controlled digital switch with two inputs and one outputs. Multiplexer 12) One eight-bit PCM code from each channel (16 total bits). TDM Frame 13) Time it takes to transmit one TDM frame. Frame Time 14) A communications system that uses digital pulses rather than analog signals to encode information. Digital Carrier System 15) Specifies a digital carrier system using PCM encoded analog signals. TI or Transmission One 16) Voice band channel bandwidth. 300 Hz to 3000 Hz 17) Special conditioned cables. TI Lines 18) Used to maintain frame and sample synchronization between TDM transmitter & receiver. Framing Bit 19) PCM encoders & decoders with a seven-bit magnitude. Digital Channel Banks 20) Supervision between telephone offices, such as on hook, off hook, dial pulsing, and so forth. Signaling 21) Only seven-bit resolution. Signaling Frame 22) Consist of bit frames, totaling 4632 bits, of Extended Super Frame Format Prepared By : MA. ELAINE L. CORTEZ 72

3 which 24 are framing bits. 23) Used for an error detection code. CRC-6 ( Cyclic Redundancy Checking ) 24) Signaling bit in frame 6. A Bit 25) Signaling bit in frame 12. B Bit 26) Signaling bit in frame 18. C Bit 27) Signaling bit in frame 24. D Bit 28) Digital interface that provides the physical connection to a digital carrier network. Data Service Unit / Channel Service Unit 29) Upgrade from one level in the hierarchy to the next higher level. Multiplexers / Demultiplexers 30) Provides a convenient place to make patchable inter connects and perform routine maintenance & trouble shooting. Digital Cross Connect 31) Provides frequency shifting for the master group signals. Signal Processor 32) Low quality video transmission for use between nondedicated subscribers. Picturephone 33) Identify when transitions occur in the data and whether that transition is from a 1 to a 0 or vice versa. Three-Bit Code 34) First bit of the code. Address Bit Prepared By : MA. ELAINE L. CORTEZ 73

4 35) Converting standard logic levels. Digital Line Encoding 36) Involves the transmission of only a single nonzero voltage level. Unipolar 37) Two nonzero voltages are involved ( a positive voltage for a logic 1 and an equal-magnitude negative voltage for a logic 0 or vice versa). Bipolar 38) Categorize the type of transmission. Duty Cycle 39) Maintained the entire bit time. Nonreturn to Zero 40) Less than 100% of the bit time. Return to Zero 41) Produces a condition in which a receive may lose its amplitude reference for optimum discrimination between received 1 s & o s. DC Wandering 42) Popular type of line encoding that produces a strong timing component for clock recovery and does not cause dc wandering. Digital Biphase 43) Uses one cycle of a square wave at 0 phase to represent a logic 1 and one cycle of a square wave at 180 phase to represent a logic 0. Biphase 44) Used for encoding SMPTE(Society of Motion Picture and Tele vision Engineers) time-code data for recording on videotapes. Biphase M 45) Commonly called the Manchester Code and specified in IEEE standard for Ethernet local area networks. Biphase L Prepared By : MA. ELAINE L. CORTEZ 74

5 46) Forms of delay-modulated codes where a logic 1 condition produces a transition in the middle of the clock pulse, and a logic 0 produces no transition at the end of the clock intervals unless followed by another logic 0. Miller Codes 47) Used for the transmission of PCM-encoded timedivision multiplexed digital signals. T Carriers 48) Filters and shapes the incoming digital signal and raise its power level so that the regenerator circuit can make a pulse-no pulse decision. Amplifier / Equalizer 49) Recovery circuit reproduces the cocking information from the received data and provides the proper timing information to the regenerator so that samples can be made at the optimum time, minimizing the chance of an error occurring. Timing Clock 50) A threshold detector that compares the sampled voltage received to a reference level and determines whether the bit is a logic 1 or a logic 0. Regenerative Repeater 51) Different version of T carriers used in Europe. E-Lines 52) Used for frame alignment pattern and for an alarm channel. Time Slot 0 53) Digital carrier frame synchronization. Added-Digit Framing Robbed-digit framing Added-channel framing Statistical framing Unique-line code framing 54) Methods of Interleaving PCM transmissions: Bit Interleaving Word Interleaving Prepared By : MA. ELAINE L. CORTEZ 75

6 55) Used more often for the transmission of data when they are called asynchronous TDM, intelligent TDM, or simply stat muxs. Statistical Time-Division 56) Large-scale integration (LSI) chip designed for use in the telecommunications industry for private branch exchanges. CODEC 57) Three functions of codec. Analog Sampling; Encoding / Decoding; Digital Companding 58) Used to gate the PCM word onto the PCM highway when an external buffer is used to drive the line. Time Slot Strobe Buffer 59) Data are input and output for a single channel in a short burst. Burst Mode 60) Allows for a flexible data input and output clock frequency. Variable-Data-Rate Mode 61) Data from the PCM highway are clock into the codec on the next eight consecutive negative transitions of DCLKR. Shift Register Mode 62) Multiple sources that originally occupied the same frequency spectrum are each converted to a different frequency. Frequency Division 63) Process is accomplished without synchronization between stations. Stacking 64) AT&T s communications network is subdivided into 2: Short Haul; Long Haul 65) Basic building block of the FDM Heirarchy. Message Channel Prepared By : MA. ELAINE L. CORTEZ 76

7 66) Separate signals with different wavelengths in a manner similar to the way filters separate electrical signals of different frequencies. Demultiplexers / Splitters 67) Similar to regular multiplexers and demultiplexers except they are located at intermediate points in the system. Add / Drop Multiplexers / Demultiplexers 68) Direct signals of a particular wavelength to a specific destination while not separating all the wavelengths present on the cable. WDM Routers 69) Enable more efficient utilization of the transmission capabilities of optical fibers by permitting different wavelengths to be combined and separated. WDM Couplers 70) Three basic types of WDM couplers: Diffraction Grating ; Prism ; Dichroic Filter 71) system similar to conventional time division multiplexing. Synchronous Optical Network 72) Has a Mbps synchronous frame structure. STS-1 73) Second level of SONET multiplexing. OC-48 Prepared By : MA. ELAINE L. CORTEZ 77