(n., adj.) A digital carrier facility that transmits a DS-1 formatted digital signal at 1.544 megabits per second (Mbps). Two unshielded twisted-pair telephone lines are used to transport T1 signals, one pair for each direction. Some hybrid equipment operates at half the T1 rate in full-duplex mode, separating the sent and the received signals at each end with components. The transmitted signal consists of pulses a few hundred nanoseconds wide, each inverted with respect to the preceding one. At the sending end the strength of the signal is 1 volt, and at the receiving end the strength must be greater than 0.01 volts. This requires repeaters about every 6000 feet. The information is contained in the timing of the signals, not in the polarity. A process known as bit stuffing is used so that the receiving apparatus will not lose track of the sending clock when a long sequence of bits of the same polarity is sent. Pronounced “TEE-one.”

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