Nortel/Polycom make a digital version of this phone. They refer to it as the Norstar Audio Conferencing Unit. If it looks like this, with the Nortel logo, it is a digital set and will NOT work on any system with an analog adapter. The KSU sees this unit as a M7100 and has all the features of a digital terminal.

[img]https://farm4.static.flickr.com/3589/3615209243_dc38021bc8.jpg?v=0[/img]

The "adapter" could very well be the power supply and not an ATA. Polycom makes these phones for other manufacturers as well, so to be sure, connect a digital set to the jack and see if it comes up.