S> 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 DS1SignalS 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 iSStuffed 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)
