Solving Fax Modem Problems

If your fax software and fax modem just aren't talking to each other, or fax sending or receiving has suddenly become unreliable, there are a number of possible problems and solutions:

-- Is the (external) fax modem plugged in (AC and phone line), turned on,
   and connected to the correct serial port?
-- Is the (internal) fax modem attempting to use an IRQ (interrupt request)
   that another serial port is already using?

If your fax modem software is running from Windows and fax communications (or the quality of received faxes) are unreliable, check the following:

-- Does your internal fax modem or serial-port I/O board use a 16550 UART
   (universal asynchron
ous receiver/ transmitter)? Use MSD.EXE to find out.
-- Are you using Microsoft's old Windows 3.1 COMM.DRV? If so, update the
   driver to version 3.11, or use the driver supplied with your fax software.
   You can also buy a third-party driver, such as TurboCommander.
-- Is your available DOS memory (before starting Windows) low? Disable as many
   TSR programs (from AUTO-EXEC.BAT) as possible. Also remove any unneeded
   TSRs from the LOAD= line of Windows' SYSTEM.INI file. Screen savers
   and virus checkers are particular culprits.
-- Make sure Windows is using a permanent swap file and it's at least the
   recommended size. (From Windows' Main group, enter the Control Panel,
   choose the 386 Enhanced icon, and click on the Virtual Memory button.)
-- Delete any .TMP files created by Windows and Windows applications. These
   are usually deleted automatically. (To find where .TMP files are stored,
   type SET at a DOS prompt and make note of the directory that TEMP= points
   to. Change to t
hat directory and delete all .TMP files in it.)
-- Run CHKDSK /F from DOS (SCANDISK from MS-DOS 6.22) to check for disk
   errors and repair them.
-- Run DEFRAG (from MS-DOS 6 or higher) or a third-party disk defragmenter
   to optimize your hard disk.
-- If Windows fax performance is still flaky, try adding the following
   lines to the [386Enh] section of Windows' SYSTEM.INI file:

   COMBOOSTTIME=30
   COMxBUFFER=4096

(x is the COM port number your fax modem uses).