Equisys technical notes

Technical guidance, explanations and fixes for our products

FIX: Errors using Zetafax with Equinox Analogue modem pool



ID: ZTN1040

This Zetafax technical note applies to:

  • Zetafax 5.5 and 6.00


A modem that works with Zetafax when attached directly to the COM port of the computer, does not work correctly via Equinox analogue modem pool (AMP). Calls either fail during transmission, or the received fax is missing horizontal bands of the page.

This can also apply to other serial port expansion cards.


Modems use a technique called "flow control" to prevent the computer sending them data more quickly than they can process it.  There are two different types of flow control - "hardware" and "software", and most serial (COM) ports support both types.  By default Zetafax uses software flow control, since this should be supported by all modems.

However, a few serial port devices (such as the Equinox AMP) do not support software flow control, and give errors if this is selected.  When used with these devices, Zetafax must be switched to hardware flow control only.


This issue is resolved in the current version of Zetafax.

You may also need to make a configuration change to select hardware flow control for each modem being used with the serial port expansion card.  The method of doing this depends on the version of the Zetafax Configuration program you have installed.

Zetafax configuration program version 8 or later

  1. Run the Zetafax Configuration program, then go to the "devices" section and edit the first fax modem installed (eg FCLASS-1)
  2. Click the "More" button to display the advanced settings dialog, then select hardware flow control
  3. Save the changes, then repeat for all other devices.


Zetafax version 5.5 and 6.00 are no longer supported by Equisys. This issue is resolved with the latest version of Zetafax. If you wish to upgrade to the latest version of Zetafax please contact the Zetafax distributor for your country for more information or:

EQUISYS plc - United Kingdom

Phone: 020 7203 4000 (Intl +44 20 7203 4000)

Fax: 020 7203 4005 (Intl +44 20 7203 4005)

Email: sales@equisys.com


EQUISYS Inc - USA and Canada

Phone: (770) 772 7201

Fax: (770) 442 5789

Email: sales@zetafax.com


Last updated: 27 February 2003 (GC/SV)

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