hronous circuits, 263 INDEX switched multimegabit data service (SMDS), 490, Telecommunication Industry Association (TIA), 15 511, 524 telecommunication management network (TMN), switches, availability of, 59 554, 564-568 switching, 28, 55. See also switches; telephone functional architecture of, 565-568 switching telecommunication planning period, 102 signaling and, 151 telecommunications network, 195f switching center levels, 178 level in, 51-52 switching congestion, inhibiting, 549 Telecommunication Standardization Sector of the switching delays, 551 ITU (ITU-T), 15 switching hubs, 311-312 telegraph, 20 switching matrix SPC function, 73 as a form of long-distance communication, 21, switching nodes, ways to convey signals between, conveying intelligence over, 22-23 switching requirements, in long-distance network dry cell batteries and, 20-21 design, 173-174 electrical, 21-23 switching system overload, 550-551 telegraph circuit, 21, 22f, 22f switch size, traffic intensity and, 55-67 with ground return, 23f switch supervisory limit, 98 telegraph hills, 20 symbols, 603-604 telephone calls period of, 263-264 routing, 150 symbols per second, 263 supervisory information on, 149-150 synchronization, 260 telephone channel, 78 synchronizing (sync) pulses, 408-409 telephone circuit, with two-wire to four-wire synchronous code division multiple access operation, 187f (S-CDMA), 452 telephone density, 176 synchronous data transmission, 261-262 telephone network. See also public switched synchronous digital hierarchy (SDH), 196, 489, telecommunications network (PSTN) 501-508. See also SONET/SDH frame frequency response of, 91f interface and frame structure, 502-508 signaling in, 149 mapping ATM cells into, 536 telephone number, 4, 5-6 synchronous payload envelope (SPE), STS-1, 491f portability of, 5 synchronous transport module (STM), 502. See telephones also STM entries loudness, 14, 43 syntax notation one (ASN.1) specification off-hook, 4 language, 555 ringing, 4-5, 14 system impairments, CATV, 434-441 telephone subscriber