資料來源 : Free On-Line Dictionary of Computing
DS1C
A {DS level} and {framing specification} for
digital signals in the North American digital transmission
hierarchy. A DS1C signal uses 48 {PCM} channels and has a
transmission rate of 3.15 Megabits per second, twice that of
{DS1}.
DS1C uses two {DS1} signals combined and sent on a 3.152
megabit per second {carrier} which allows 64 kilobits per
second for synchronisation and {framing} using "{pulse
stuffing}". The channel 2 signal is logically inverted, and a
framing bit is stuffed in two out of three code words,
resulting in 26-bit information units. The channels are
interleaved and then scrambled by the addition {modulo} 2 of
the signal with the previous bit. Finally the bit stream is
combined with a control bit sequence that permits the
{demultiplexor} to function by preceding each 52 bits with one
DS1C framing bit. A series of 24 such 53-bit frames forms a
1272-bit "M-frame".
(1995-02-07)