The PDM-1 Phone-Doorbell Mute Plate is used with RTI Audio distribution systems (Models: AD-8x/AD-4x/AD-8/AD-4) to provide a connection point for phone and doorbell systems. When an incoming call is received or a doorbell is rung, the voltage from these systems is passed to the audio distribution system and will temporarily mute the audio. The PDM-1 is wall mounted in a standard single gang electrical box and uses a Decora style wall plate (not included).