PIR Wall Switch Occupancy Sensor. 1 Button. The IR WLS 1 is a line voltage, single relay, Passive Infrared (PIR) wall switch occupancy sensor intended to control lighting in commercial spaces. PIR is used where the sensor will have a clear view of the occupants in the desired coverage area. The hold OFF photocell daylight option will keep the lighting load off if the light level is greater than the threshold level setting. The convenient “Switch Link” feature enables up to four sensors to link together for pier to pier grouping achieving expanded detection zones and multiway switching.