06 attenuation distortion in, 269 later versions of, 304-306 based on CCITT Rec. V.110, 277-278 propagation time for, 303 defined, 251 CSMA (carrier sense multiple access) LAN, 299, on a digital network, 277-278 300-306 noise in, 269-271 CT2 common air interface, 482 CT2+ common air interace, 482 on permanent virtual circuits, 388 cue channel, 413 phase distortion in 268, 269 cultural factors, calling habits and, 173 versus digital telephony, 387-388 current data user part (DUP), 364 in ac circuits, 594-596 Dauber, Steven, 542, 543 early sources of, 20-21 dBd values, 635. See also decibels (dB, dBm) subscriber loop, 95 dBi values, 635 current flow, telephone, 93 dBmC unit, 628-630 customer premise equipment (CPE), 169, 195 dBm values, calculating, 619-621, 624-625 customer satisfaction, 14 dBmV values, 434-435 cyclic redundancy check (CRC), 256 dB values, calculating, 623-625 CRC-4, 546-547 dBW values, calculating, 619-621, 624-625 CRC-6, 545 dc (direct current) circuits, 23 electrical power in, 584-585 dash, Morse code, 22 dc loops, 258 data channel propagation time, 376 calculating resistance in, 96 data circuits dc networks, solving problems in, 583-584 as a QoS parameter, 44-45 dc signaling, negative-impedance repeaters and, signaling on, 388 data communication equipment (DCE). See dc transmission, 258-259 DTE-DCE interface DDS signal subhierarchy, 278f data communications, 251-290 decibels (dB, dBm), 14, 41, 42, 51, 52, 615-635. binary convention in, 252 See also dB entries binary transmission and time concept, 259-265 basics of, 615-619 coding in, 252-254 decision circuit, 35 data interface in, 265-267 decoding, 119 data protocols in, 278-287 DECT (digital European cordless telephone), 482 data transmission errors, 254-258 degrees, time-scale, 27-28 dc nature of data transmission, 258-259 degrees of rotation, angular, 25 defined, 251 dejitterizer, 393 digital transmission on an analog channel, delay, 47. See also echo delay 267-278 LEO system, 484 layers of, 280-281 postdialing, 160 data frame, 261f, 388f p