T2 definitions

A 6.312 Mbps point-to-point, digital dedicated line provided by the telephone companies. A T2 line provides 96 64-Kbps voice or data channels. See T-carrier and DS.
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Corresponds to DS-2 (Digital Signal Two), the second level in the North American T-carrier digital hierarchy. T2 was designed for intercity transmission at distances up to 500 miles. T2 runs at 6.312 Mbps and comprises four T1s at 1.544 Mbps each, plus 132 kbps of overhead and justification, or bit stuffing, to adjust for variations in the clocking rates of the incoming T1s. Multiplexing is performed by M12 (Multiplex T1-to-T2) terminals that multiplex four T1 signals, which yields 96 DS-0 channels at 64 kbps per channel.T2 is unusual, although some does remain in place in the local loop, where Bell System companies used it in digital loop carrier (DLC) applications. The Subscriber Line Carrier-96 (SLC-96) system introduced by Western Electric (now Lucent) in 1979, for example, essentially is a remote line shelf and time division multiplexer (TDM mux) that allows a single four-wire twisted-pair or optical fiber circuit to serve as many as 96 channels. See also bit stuffing, digital hierarchy, DLC, DS-0, DS-2, local loop, and T-carrier.
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A set of standards for facsimile (fax) machines published by the ITU-T in 1966, and based on the EIA RS-328 specification published by the Electronic Industries Alliance (EIA). Machines conforming to T.2 later became known as Group I. See also EIA, facsimile, Group I, ITU-T, T.3, T.4, and T.6.
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