Even some analog and PRI circuits are not modem friendly. I found it impossible to use dialup with AT&T PRI hand-off. We have a Cable company analog at our office that seems work close to POTS. Since I don't have an analog at home I have a PC at the office with Logmein software that I use for dialup connections to the locations that still work. As more people switch their phone lines it is getting increasingly harder to support a dialup connection.

Some of the equipment we installed has a Windows operating system, so Logmein would work fine. Some of the equipment is Linux based and administered with a Web browser. Unless their IT forwards public ports or grants VPN access we can't admin those accounts.

As a test I was able to use a Linux machine as a gateway device using Logmein Hamachi. With this I was able to access the system through a network connection behind the firewall. I believe that you could do the same thing with a Raspberry Pi, but I did not test it this way.

David
Tele Express Business Systems