T1 definition communications term for a digital carrier facility
used to transmit a DS1 formatted digital signal at 1.544
megabits per second. T1 transmission uses a bipolar Return To
Zero alternate mark inversion line coding scheme to keep the DC
carrier component from saturating the line. Although some
consider T1 signaling obsolete, much equipment operates at the
"T1 rate" and such signals are either combined for transmission
via faster circuits, or demultiplexed into 64 kilobit per second
circuits for distribution to individual subscribers. T1 signals
can be transported on unshielded twisted pair telephone lines.
The transmitted signal consists of pips of a few hundred
nanoseconds width, each inverted with respect to the one
preceding. At the sending end the signal is 1 volt, and as
received, greater than 0.01 volts. This requires repeaters about
every 6000 feet. The information is contained in the timing of
the signals, not the polarity. When a long sequence of bits in
the transmitted information would c