Intermatic T104M201 24-Hour Mechanical Timer with Heat Protection DPST Provides coordinated control for heater and filter pump operations Designed to turn OFF a gas fired swimming pool heater approximately 20 minutes before the filter pump shuts down Eliminates the problem of pounding and knocking due to overheated water, reduces scale and lime deposits and extends the service life of the heater The 24-hour dial allows up to 12 ON/OFF operations each day One set of ON and OFF trippers is supplied with each switch