Advantech PCM-3601 - Manual (Page 12)

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2.3 Communications Protocol
Two popular groups of communications protocol are currently used
in data communications throughout the world, the Bell standard
and the CCITT recommendation. For 1200bps protocols, the Bell
standard is used mainly in the United States and Canada, while
the CCITT standard is used in most other countries. For 2400bps
and faster protocols, the CCITT standards are used internationally.
The following table shows common communications protocols
listed from the highest to the lowest DCE speed.
DCE Speed Bell CCITT Synchronous
56000bps N/A V.90 async
33600bps N/A V.34+ async
28800bps N/A V.34 async
14400bps N/A V.32bis (TCM) async
9600bps N/A V.32 (QAM & TCM) async
2400bps N/A V.22bis async
1200/75bps N/A V.23 Main (host) async
75/1200bps N/A V.23 Back (user) async
1200bps 212A V.22 async
0-300bps 103 V.21 async
Data communications requires that both modems on a link use the
same protocol. The protocol determines the communications
speed and transmission standard (Bell or CCITT). To change
protocols, you can issue a B command and the modem automa-
tically goes to the highest speed of that protocol. If you want to
specify a particular protocol speed, issue a %B command.
2.4 Speeds of the Modem
During an on-line communications path, your modem is located
between the local computer and remote modem. It has to