ADN networks

I am a utility supervisor overlooking a SCADA project. Part of this project calls for 3 remote sites to use telephone lines to transfer small packets of information. Telecom is proposing ADN circuits. What are ADN networks? The ADN network will be installed on AT&T phone lines by their techs and contractor will install some type of modem. I understand this is old technology and very few techs understand it or even know of it. Any info would be much appreciated