T3 - technical definition

Corresponds to DS-3 (Digital Signal Three), the third level in the North American T-carrier digital hierarchy. Designed for long-haul transmission in support of interoffice trunking in the public switched Digital Circuit DS-1 Framing Bit Byte Frame Host 1 2 ... 24 Buffer Buffer TDM TDM ... 24 ... 24 ... 24 ... 2 1 2 1 2 1 ... 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 1 0 0 1 1 0 0 1 19 20 21 22 23 24 24 ... 24 ... 24 1 2 1 2 1 2 1 2 24 telephone network (PSTN), T3 runs at a signaling rate of 44.736 Mbps. A T3 actually begins as four T1s multiplexed into a T2, by an M13 (Multiplex T1 to T3) mux, which then multiplexes seven T2s to yield a signaling rate of 42.924 Mbps. Stuff bits are added to adjust for variations in the clocking rates of the incoming T2s, bringing the signaling rate up to 44.736 Mbps, comprising 672 DS-0 channels at 64 Kbps.T3 will run over a four-wire twisted-pair circuit, but for no more than 50 feet, due to issues of signal attenuation. Other media, such as coaxial cable, microwave, and optical fiber, are more appropriate. See also bit stuffing, channel, digital hierarchy, DS-0, four-wire circuit, long haul, multiplexer, PSTN, signaling rate, T-carrier, and trunk.