T1 definition


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2 definitions found

From Virtual Entity of Relevant Acronyms (Version 1.9, June 2002) [vera]:

       [digital] Transmission link 1 [1.544 Mbit/s] (DS1)

From The Free On-line Dictionary of Computing (27 SEP 03) [foldoc]:

           An {AT&T} 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 cause no pip to be sent, "{bit stuffing}" is
          used so the receiving apparatus will not lose track of the
          sending clock.
          A T1 circuit requires two twisted pair lines, one for each
          direction.  Some newer equipment uses the two lines at half
          the T1 rate and in {full-duplex} mode; the sent and received
          signals are separated at each end by components collectively
          called a "hybrid".  Although this technique requires more
          sophisticated equipment and lowers the line length, an
          advantage is that half the sent and half the received
          information is mixed on any one line, making low-tech wiretaps
          less a threat.
          See also {Integrated Services Digital Network}.

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