Peter:

The links below take you to some of many web pages that describe the common "Hayes Command Set".

http://docs.kde.org/en/3.1/kd...mands.html
http://www.spiralspider.demon.co.uk/reference.../hayes.htm
http://www.its.unimelb.edu.au/InfoSheets/162/


As you can see, not all Hayes commands begin with an A character byte. There is the command AT that is the ATTENTION command that tells a modem that other modem commands follow. This is used at the beginning of a sequence of modem commands that could be many commands long.

I am also not sure that it is a general rule that modems will "autobaud" detect off the AT command. Some may and some may not. I don't use a modem much at all anymore and these days almost all modems are the "windows bus modems" where baud rate between the host and the modem is immateral. I do however recall personal experiences in times gone by when a modem that was external on a COMM port had to have the baud rate to the computer set correctly before the modem would accept the "Hayes commands". Later on when MNP 4 and MNP 5 modems came along then the COMM port speed between the modem and the computer was often set to a rate faster than the data rate on the phone line. In some cases this may have allowed a modem to use an autobaud off the AT command but I can also see some old equipment I have laying around that still had baud rate switches on the modem despite the fact that it supported the MNP protocols.

Michael Karas