If you have two models connected to two computers. You might be able to
test your setup by connecting a null modem phone cable between the phone
line ports of both modem.
Basically crossing transmit pairs from one side to the receive pairs of the
other modem and vice-versa.  Not sure if it will work without dial tone
from the phone line present. But there might setting in your modems
configuration that would activate what is needed for such a modem to.modem
direct link.

On Sat, Oct 23, 2021, 7:50 PM John Floren <john@jfloren.net> wrote:

> I'm experimenting with my PiDP-11; I think I may have my modem set up
> properly to accept incoming calls, but with only one phone line I'm unable
> to test it. If anyone with a modem is willing to help me test, send me a
> message off-list and I'll give you my phone number & some login details.
>
> john
>
>