58 composite signal in, 407-409 time switch. See time-slot interchanger (time- conference, 423-427 switch, TSI) digital, 417-423 time unavailability, 213 factors in, 404-406 TMN reference points, 567-568 frame transport for video conferencing, 427-428 token-passing ring network, 306-307 over LOS microwave, 414-416 token ring protocol, 306-308 program channel transmission methods in, toll connections, 75-76 413-414 toll-connecting exchange, 175 by satellite relay, 416-417 tone direction, 151 video parameters in, 409-410 "tone-off,", 152, 157 temporary signaling connections, 379-380 "tone on when idle,", 151, 152 terahertz (THz), 35 terminal, battery, 21 topologies, 10, 292 LAN, 292-294 terminating line appearances, 70, 71f TerminationID, 400 network, 10-13 terminations, 398 total capacity utilization, PSTN, 7 terrestrial links, signaling link delays over, tower height calculation, LOS microwave antenna, 376-377 200-203 tested routes, 181 tracking, LEO system, 484-485 test level point (TLP), 51 traffic. See also data traffic; signaling traffic test tone, 42, 51 management tether, 478 add-drops of, 199, 200f TFTP (Trivial File Transfer Protocol), 357 frame relay network, 333-334 theoretical design, 99, 100 sources of, 60 thermal noise, 120, 269-270, 48-49 traffic characteristics, message transfer part, 376 in CATV systems, 435-436 traffic concentrator, 7 in long-distance PCM transmission, 127-128 traffic control, ATM, 532-533 power level of, 207 traffic flow, variations in, 13-14 in upstream services, 451 traffic formulas, 61-63 three-level hierarchy network, 176, 177f traffic intensities, 55-67. See also traffic studies three-way handshake, 326, 327 busy hour, 8 threshold circuits, 122 dimensioning and efficiency, 63-67 through-timing, 500 Erlang and Poisson traffic formulas, 61-63 tilt, 439 waiting systems (queueing), 63 time availability, 199, 213 traffic matrix, 178, 180 time constant, 592 traffic path, 56 time-dependent routing, 182 traffic peakedness, 66f example of, 185-186 traffic relation, 10 time distribut