Using no mechanical parts, the GRI Sensors are triggered by a moisture bridge across the sensor contacts. The GRI Sensor can be installed to detect a layer of liquid as minute as 1/16 of an inch in depth. These sensors use an external power source to energize a built-in relay contact (battery power is not recommended.) Used in an active SPDT configuration, an alarm condition will occur when moisture is detected, power to the sensor is lost or if the sensor should fail. The relay output can be wired directly to a control panel or can be used to actuate an external device, i.e. transmitter, annunciator, etc., and can be used to monitor evaporative air conditioners, drip pans, overflows and/or drains.