At least 15 years ago, I sucessfully integrated a Key Voice VM system to a Nitsuko Onyx. It works because the Onyx sends integration digits to the single line port programmed as a VM port and the Key Voice has the mode of waiting for the digits before anything else happens. I probably burned about 16-24 hours making it behave and the customer probably used it for a couple of years before he replaced the system.

Your Rhetorex board is probably a full-length ISA board designed to run under DOS. I would think any modern software, Amanda, my Brickmail :-), or anything that's trainable would do as a starting point. You just need to sit down with the service codes table and start testing. If you can score Amanda software, it will actually run for 3 days in the "demo" mode while you test it. It's not practical to keep rebooting the box every 3 days, but it would give you an idea of how to make a system work.

Carl

This model is end of life