Add the Intermatic 178PA28A Freeze Air Temperature Sensor to installations where below-freezing outdoor temperatures are a concern. The Intermatic freeze sensor is designed to protect the pool and spa equipment and plumbing against freeze damage. The sensor plugs into the circuit board on the back of the P1353ME and turns ON the filter pump when air temperature drops below the programmed temperature. The freeze programming mode will not appear unless the sensor is plugged into the clock.