The CESF PIR incorporates a passive infra-red quad sensor to detect movement of a warm body within its detection zone and a photocell to monitor the ambient light level.

Upon detecting movement, if the ambient light is dark enough, the CESF PIR will switch the load on. The ambient threshold can be set by the user to between approximately 100 lux and infinite lux (photocell inactive) via the LUX adjuster.

If no more movement is detected within a pre-selected time, then the CESF PIR will switch the load off. This time lag can be set via the TIME adjuster to 10 seconds, 20s, 40s, 1 minute 15 seconds, 2m 30s, 5m, 10m, 20m or 40 minutes.

CESF PIR also incorporates a sensitivity adjuster, labelled SENS, to reduce the range and sensitivity of detection.