Hard starts relay and start capacitor combination, gives maximum torque possible for all single phase units from 1/12 through 10 HP. The simple 2 wire connection is Voltage sensing and has instant restart capability. A backup electronic timing circuit protects the compressor.Electronic potential relay EPR technology and 330 VAC start capacitorUL recognized file E146162Can be used on PSC and CSIR type compressorsVoltage sensing 90V-277V