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The T-carrier is a hardware specification for carrying multiple time-division multiplexed (TDM) telecommunications channels over a single four-wire transmission circuit. It was developed by AT&T at Bell Laboratories ca. 1957 and first employed by 1962 for long-haul pulse-code modulation (PCM) digital voice transmission with the D1 channel bank.
A T1 feed demultiplexed through a Newbridge channel bank to 24 channels with an Amphenol connector. In telecommunications, a channel bank is a device that performs multiplexing or demultiplexing ("demux") of a group of communications channels, such as analog or digital telephone lines, into one channel of higher bandwidth or higher digital bit rate, such as a DS-1 (T1) circuit, so that all the ...
In the 1970s it replaced the original T1/D1 framing scheme of the 1960s in which the framing bit simply alternated between 0 and 1. Superframe is sometimes called D4 Framing to avoid confusion with single-frequency signaling. It was first supported by the D2 channel bank, but it was first widely deployed with the D4 channel bank.
In an NFAS configuration, multiple T1 circuits share a single D channel, with an upper limit of 20 T1 circuits in a single NFAS configuration. A full NFAS configuration can then be described as 479B + D. There is one problem; a failure on the T1 trunk carrying the D channel will also affect all 19 other trunks.
The T1 line consists of 23 bearer (B) channels and one data (D) channel for control purposes, [1] for a total bandwidth of 24x64-kbit/s or 1.544 Mbit/s. The E1 carrier provides 30 B- and one D-channel for a bandwidth of 2.048 Mbit/s. [2] The first timeslot on the E1 is used for synchronization purposes and is not considered to be a B- or D ...
A CSU/DSU (channel service unit/data service unit) is a digital-interface device used to connect data terminal equipment (DTE), such as a router, to a digital circuit, such as a Digital Signal 1 (DS1) T1 line. The CSU/DSU implements two different functions.
T1 is a protocol for digital transmission over telephone networks. A T1 circuit combines 24 DS0 channels through time-division multiplexing. Data is transmitted in frames, where each frame contains an 8-bit sample of each of the 24 channels, plus one extra framing bit for a total of 193 bits. Each channel carries 8,000 samples per second.
In order to efficiently transport slowly varying channel associated signalling bits, second order structures known as multiframes or superframes are defined. For example, for E1 trunks the CAS signaling bits are updated once per multiframe of 16 frames (every 2 milliseconds) while for T1 ESF trunks the superframe is 24 frames (3 milliseconds).