 Division Multiple Access), Telephone networks, 29/1-20 25/15-16 13/3, 13/13-15, 13/19-20 architecture, 29/4-7 Symmetric channels, 4/7-8 AMPS cellphones, 47/8 digital transmission, 29/10-12 Symmetric cryptosystems, 14/12 cordless telephones, 49/11 grades of service, 29/16-19 Symmetric pair cables, 15/3-5 GSM cellphones, 47/10 international, 29/7-8 Synchronisation distortion, 10/10 ISDN, 44/15 numbering and charging, 29/12-15 Synchronous containers, SDH, 42/5, multipoint systems, 52/4, 52/7-8 routing, 29/15-16 42/9-11, 42/16 PCN air interface, 48/8 services, 29/12 Synchronous digital hierarchy see SDH satellite, 51/14-15 standards, 29/8 Synchronous island strategy, SDH, 42/25 TDR (Time Domain Reflectometer), transmission and trunk circuits, 29/8-10 Synchronous operation, modems, 39/5, 33/8, 61/12 Telephone signals, 10/5-6 39/11, 39/12 TE (Terminal Equipment), ISDN, 44/7-8 Telephone switching systems, Synchronous TDM see STDM; TDM TEC (Triple Error Correction) code, 14/6 analogue space-division, 29/10, 31/12 Syntran digital multiplexing system, 53/25 TEI (Terminal Endpoint Identifier), analogue switching, 31/9-12 System 12 exchange system, layer 2 ISDN, 44/9 digital switching, 29/10, 31/12-15 architecture and hardware, 32/8-12 Telecommunication cables see Cables security, 31/16-17 evolution, 32/7-8 Telecommunication standards see signalling, 31/8 System software testing, 25/4, 25/16 Acronyms for individual organisations; stored program control, 31/15-16 Standards, organisations subscriber types, 31/6 T1 multiplexers see TDM Telecommunications industry, system structure, 31/4-8 reverberation time, 8/10-11 competition, 11/12-13 telephones, 31/4-6 T carrier framing and coding, 21/6-9 developing countries, 11/12 teletraffic, 31/8-9 TACs (Technical Advisory Groups) of Europe, 11/7-10 time division, 31/12 ISO, 22/13 Japan, 11/7 see also Telephone exchanges TACS (Total Access Communications pricing and costs, 11/10-11 Telepoint, 11/3, 49/4 System), cellphones, 47/8 PTTs and PTOs, 11/4-6 Teleprinters, 59/3 TAG (Technical A