Abstract

T1 carrier provides 24 voice channels by time division multiplexing and pulse code modulation (PCM). Each voice channel is sampled 8000 times a second and each sample is coded into a 7-digit binary word. Provision for signaling and synchronization raises the pulse repetition rate on the repeatered line to 1.544 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">6</sup> pulse positions per second. The bipolar pulse train out of the terminals is transmitted over pulp, paper or plastic insulated paired cables by the use of regenerative repeaters. For 22-gauge cable pairs, repeaters are normally located at 6000-foot intervals. The system has been designed for low cost and is being widely applied on many trunks interconnecting switching units within metropolitan areas. Western Electric Company manufacture of T1 began in 1962 and about 100,000 channels are now in service throughout the Bell System.

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