I got a question from one of my colleagues about administration through PSTN. Other PBX vendors we sell and support has the possibility to have a BRI or FXO on the PBX to let us administer the PBX from our office. In some of our deployments we are not able to get connected to the UC through the WAN interface and it would be great if it was possible to administer the UC via the BRI,FXO or PRI interface on the UC.
Pretty much any modem should work. here is a config example with US Robotics:
You will need to connect your computer to a phone line via a built in model or something like that. unless of course, you can find that service you describe.
Voice ports on the UC500 do not support modem dialin. You can connect a modem to the Console port and get remote access that way.