| 摘要 |
A time division multiplex system which has a total bandwidth of 64Kbit/s and has this bandwidth split up into 80 channels each of 800 bits/sec. Three speech channels are provided, each using 20 of these channels, 12 channels are used to provide a 9.6Kbit/s data channel, 4 are used to provide for 50-110 baud start-stop channels and another 4 are used to provide a 3.2Kbit/s signalling channel. To provide fast sync, a sync pattern consisting of two sync words and a channel number is sent at the same time on all of the channels, and the receiving side monitors for the 19th channel. When it finds what is coming in at the time, it first achieves bytes alignment between the received byte stream and the local byte stream, then it checks the respective channel numbers. The difference between them gives an offset which is used to adjust the demultiplexing logic.
|
