The Castlegate III is a single residence, hands-free telephone auto-dial telephone entry system for use at a private residence. It uses the existing telephone line for communication and access control. However, since calls do not go into the telephone company network, there are no charges for calls made from the system.

Visitors initiate calls from the entrance by pressing the "call" button on the illuminated faceplate. The call is received in the residence as with any other call. Residents can discern between entrance calls and regular telephone calls due to the unique ring modes available with the Castlegate III. A second relay allows control of an optional internal camera.

Residents, employees, or guests can access the premise immediately by entering their personal code on the Castlegate III keypad