T1

T1 (1) A 1.544 Mbps point-to-point dedicated, digital circuit provided by the telcos and upstream providers. The monthly cost is typically based on distance. T1 lines are widely used for private networks as well as interconnections between an organization's PBX or LAN and the telco. The first T1 line was tariffed by AT&T in January 1983. However, starting in the early 1960s, T1 was deployed in intercity trunks by AT&T to improve signal quality and make more efficient use of the network. A T1 line uses two wire pairs (one for transmit, one for receive) and time division multiplexing (TDM) to interleave 24 64-Kbps voice or data channels. The standard T1 frame is 193 bits long, which holds 24 8-bit voice samples and one synchronization bit with 8,000 frames transmitted per second. T1 is not restricted to digital voice or to 64 Kbps data streams. Channels may be combined and the total 1.544 Mbps capacity can be broken up as required. See DS, T-carrier, bipolar transmission, D4 and Extended Super Frame (ESF). 64 Kbps 128 Kbps T-carrier Total speed Channels T1 1.544 Mbps 24 T2 6.312 Mbps 96 T3 44.736 Mbps 672

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