ues in, 128-129 double seizure, 9 approaches to, 129-135 "downlink channel descriptor,", 353 concepts related to, 135-137 downlink-limited satellite communication, 223 digital switching systems, jitter in, 127 downlink power budget, 226-228 digital symbols, 264 downstream bit rates, 169 INDEX downstream services, 448, 449 versus circuit group size, 66 DQDB (distributed queue dual bus), 511 EIA-232 DTE/DCE standard, 266 D/R ratio, 476 EIA-530 DTE/DCE standard, 266-267 dry cell batteries, 20-21 EIA/TIA (Electronic Industries Association/ connected in series, 21f Telecommunication Industry Association) DS1 PCM line rate, 1.544-Mbps, 277 standards, 266-267 DS1 (T1) PCM system, 108, 109 8-ary PSK, 274 coding for, 115 E-lead signaling systems, 154 digital hierarchy in, 490 electrical coding, of binary signals, 264-265 enhancements to, 122 electrical communication, 1 format with, 489 electrical latching, 72 frame rate for, 545 electrical signals, 19, 28-31 framing structure of, 116, 117f electrical signal transport, 31-38 mapping, 534 coaxial cable, 31, 34-35 signals in, 500 fiber-optic, 31, 35-36 DS2 frame, 125f radio, 31, 36-38 DS2 higher-level multiplex, 122-124, 125f wire pair, 31-34 DS2 signal formation, 124f electrical telegraph, 20, 21-23 DS3 frame, 533-534 electric current, 576. See also alternating current DS3 tributary signal, 498-499 (ac); ac entries; current entries; dc entries DSS-1 (Digital Subscriber Signaling No. 1) magnetism and, 585-586 system, 151 electricity, 19, 575-577 DSX (digital system cross-connect), 142, 143 electricity concepts, 20-28 DTE-DCE interface, 265-267 current sources, 20-21 duplex operation, 9 frequency, 23-28 dynamic alignment, 496 telegraph, 21-23 dynamic routing, 13, 176, 178, 182-183 electric potential, 576 examples of, 185-186 electric power in ac circuits, 596-597 E1 PCM hierarchy ("European" system), 108, 109, in dc circuits, 584-585 124-126 electrode, 21 companding curve and coding for, 114-115 electroluminescence, 236 digital hierarchy in, 490, 546 electromagnetic compatibi