T1 Digital Service
0.3 kHz - 3.4 kHz analog bandwidth sampled at 8 kHz with 8-bit resolution (28 = 256 levels) gives 8000 X 8 = 64 kb/s per voice channel (DS0). For voice traffic may only use 7 of the 8 bits and use 1 bit for encoding
T1 frame is 24 X DS0 time division multiplexed full duplex circuit
24 X DSO + frame = (24 X 8 X 8000) + (1 X 8000) = 1.544 Mb/s
Digital Cross-connect System allows any DS0 from one T1 line to be connected to any other T1 line without additional multiplexing or switching
T3 = 672 X DS0 + frame = 44.736 Mb/s (i.e. T3 ~ 28 X T1)
For a tutorial on T1 cabling and signaling see http://www.laruscorp.com/
Framing bit provides synchronization mechanism
and management and control information