Using BGFAX for DOS with Windows:
The Flow Control Problem

Many people have used the DOS version of BGFAX to send faxes while running under Microsoft Windows 3.1. (The flow control settings do NOT matter if you are receiving faxes, only sending them.)

You do not need to read this if you are sending with BGFAX32.EXE. The 32-bit version of BGFAX for Windows 95 and NT will handle the flow control settings automatically!

Almost always, people encounter flow control problems while attempting to send faxes with Windows 3.1. There is an easy fix for this, but the easy fix will interfere with other communications programs.

Pick either the one-step or the two-step fix below. Do not apply both.

The easy one-step fix...

In the Windows SYSTEM.INI file, set COMxProtocol=XOFF

Where "x" is the com port number.

The better two-step fix...

1. Add a /HW switch to the end of the BGFAX command line.

This tells BGFAX to use hardware handshaking (CTS flow control) when sending.

 BGFAX /send test.fax 5551212 /hw 
2. Edit the BGFAX.CNF configuration file and make a modification to the ds= verb.

Before modification...


After modification...

For Rockwell-based modems ds=atm2s7=90&K3dt

For US Robotics modems (Class 1 mode only) ds=atm2s7=90&H1dt

This is the better fix, because it should not interfere with any of your other Windows communications programs, as you are localizing the change to BGFAX directly instead of modifying the SYSTEM.INI file on a global scale.

Look up the Rockwell "&K3" command in your manual to make sure that it enables CTS flow control. Sometimes modem makers change the commands around just to be different.

Speaking of different, use a "&H1" command on US Robotics modems, instead. Note that if your US Robotics modem is sending the fax using Class 2.0 mode, you do not need to modify the ds= string, because there is a Class 2.0 fax command that allows BGFAX to select the flow control method.

Why do you need to perform one of these fixes?

Because BGFAX probably will not be able to correctly send faxes under Windows if you don't! Many multitasking operating systems seem to want to play with the flow control settings for the com port. OS/2 does this as well, but since BGFAX has an OS/2 version, I can twiddle with the serial I/O settings for the port inside the actual BGFAX2.EXE file. I do not believe this can be done for Windows with a DOS executable file--so it requires manual intervention to make one of the two quick fixes.

These fixes might also work well for DesqView if you are having trouble sending under DV, too.

BGFAX defaults to use XON/XOFF flow control during fax send, because most modems default to XON/XOFF mode as soon as they are switched into fax mode.

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