Acceleport RAS/4 gets hung intermittently

We have a fax engine that we use for sending outbound courtesy copies of medical reports to physician offices.

For high-volume accounts, we usually use an Acceleport RAS/4 card with 4 phone lines.

Intermittently, but ineveitably, the Digi modems will hang and we will get “modem command timeout” errors from our fax engine because it cannot communicate with the modems.

Either rebooting the machine or disabling and re-enabling the main device in Device Manager solves the problem… until several days later it will occur again.

Our standard init string for the modems is:


I’ve seen a post about “Close Timeout” as a configurable parameter on the virtual modem ports, but there is nothing in the documentation that says what this parameter means.

If anyone could offer some suggestions, I would greatly appreciate it.


All of the AT commands in that string make sense except the K4. That isn’t a valid command in the Acceleport RAS commandset, so I have no idea what effect it would have.

My initial guess as to the lockup issue is that its probably flow control. Modems have RTS/CTS (hardware) flow control set as the default, which is correct and most desireable for modem operation. Serial ports/modem programs on the other hand might have Xon/Xoff (software) flow control set. The result being a flow control mismatch, which would appear as a lockup as you described.

The best way to eliminate this possibility would be to make sure that both your Fax application and the serial port itself are set to use RTS/CTS (hardware) flow control.

If this is setup and testing reveals that the problem still exists, the best course of action at that time would be to open a Technical Support case via phone or online support request form.

Thanks for the suggestions.

As a note, there is no K4 in the init string. There is a &K6, which enables both RTS/CTS and XON/XOFF flow control.

From what you’re saying, it sounds like we ought to try &K3 instead to force RTS/CTS flow control?

I’ll certainly give it a shot :o).

Most definitely &K3, but make sure the serial port side of things is getting set for RTS/CTS as well, since &K3 will only setup the modem. Not sure which OS this is on so hard to say how to do that. Its probably in the Fax software config itself, but check settings on the serial port to make sure.