For electric heat, hot gas or compressor shutdown defrost. The DTAV40 Series Auto Voltage Defrost Timer is applicable to air defrost (compressor shutdown) and electric or hot gas defrost systems where the defrost cycle is terminated by the timer. If the coil is frost-free, the timer can also be terminated by temperature or pressure switches before the programmed defrost termination time has been reached. The time termination functions as a fail-safe and terminates the defrost cycle if the temperature or pressure switch fails to do so.