The Daikin-McQuay 1840061 Sensor is an OEM pyroelectric passive infrared (PIR) sensor designed to detect movement and occupancy within compatible Daikin HVAC systems. It works by sensing changes in infrared radiation emitted by people or moving objects and communicating occupancy information to the unit’s control system. This sensor is used in compatible Daikin air conditioning system... https://www.partshnc.com/1840061-daikin-mcquay-sensor