TECHNICAL BULLETIN #50 - Rev 1.10 (9/03/96)

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TITLE   : Introduction to Fax Modem "AT" Commands
PRODUCT : Procomm Plus 4.x, 3.x
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The vast majority of modems used with Procomm Plus recognize the original
Hayes-compatible AT modem command set, which was introduced with the original
Hayes 300 baud Smartmodem.

However, today's advanced high-speed modems offer several features that were
not included in the original AT commands, including data compression, error
correction and fax support.  For example, all fax modem AT commands follow the
format:

       AT+F<command>

Of course, since all fax modems can also operate as standard data-only modems,
they also support the standard AT commands.  Fax modem AT commands can be
specified as part of the Fax Initialization string in the Current Setup's Fax
Connection screen.  Alternately, if your fax modem is in AT command mode, you
can type them directly to your modem from the Terminal window.

In this document, you'll learn more about common AT commands used by Class 1
and Class 2 fax modems.

CLASS 1 VS. CLASS 2 FAX MODEMS
Although both Class 1 and Class 2 fax modems qualify as Group III fax devices,
they actually vary quite a bit in features and operation.

CLASS 1
This standard refers to an older class of PC fax modems.  Class 1 fax modems
depends on the computer to perform all fax operations.  The primary task
handled by the modem is the transfer of the document data over the phone line.

CLASS 2
Class 2 is a more recent standard, where the fax modem performs many of the
fax operations along with the data transfer.  For example, a Class 2 fax modem
handles the negotiations for transfer speed.

FAX MODEM 'AT' COMMANDS

+FCLASS?
This command instructs your modem to respond with a zero if it's currently
configured for data calls or a 1 if it's configured in fax mode.  Note that
+FCLASS? will also work for Class 2 fax modems.

+FCLASS=?
This command displays the available fax classes supported by your fax modem.
A response of "0,1" indicates the modem supports data and Class 1 fax
transmission; the message "0,1,2" indicates the modem also supports Class 2
faxing.

+FCLASS=0
This command configures your fax modem for data operation.  Procomm
Plus will send this command string before connecting to a data modem.  Note
that +FCLASS=0 will also work for Class 2 fax modems.

+FCLASS=1
This command configures your fax modem for Class 1 operation.  Procomm
Plus will send this command string to prepare your fax modem before sending
or receiving a fax.

+FCLASS=2
This command configures your fax modem for Class 2 operation.  Procomm
Plus will send this command string to prepare your fax modem before sending
or receiving a fax.

+FMFR?
This command displays the modem's manufacturer identification string for Class
2 modems.  The string can be up to 2K (2048 bytes) long.

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           Copyright (c) 1996 Quarterdeck  All rights reserved.
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