Revex Wireless Chime Intercom XPN Series Transmitter and Receiver Set Sound/Shock Sensor Expansion Light and Sound Call Chime Security XPN760 This is a set of two sound sensor transmitters. They were stored away with little use. - Brand: REVEX - Model Name: XP Series - Function: Sound Sensor Transmitter - Quantity: Set of 2 - Included: Remote Control Thank you for viewing.