Reply 20 of 51, by 486man_
Thanks for good post on an interesting subject. I have to try VOIP gateway and/or Cisco router at some point as they sound interesting. Based on your post I assume the VOIP gateways can be used as "poor mans PBX" to interconnect two modems in such a way that doesn't break modem communication (without or with proper VOIP coding). And generate RING signal of course.
As a side note you dont need "phone line simulator" kind of device at all if both of following conditions are true
a) at least one of the modems is USR courier
b) you have a way to make the "server side" modem answer without RING signal
I have used USR courier as server side modem. You can program the data/voice button to execute arbitrary at command. Of course here the command would be ATA. After dialling out with client (e.g. atx3dt123456 or just atx3d) you would hit the button and listen modems handshaking (the beautiful sound). After completing the handshake PPP (or slip) takes place.
Here's my other post Internet with retro PC and HW
Unfortunately I didn't find your tutorial when building my setup.. 😒