240 VAC, 4 Poles, 50 Amps per pole. Enclosure: 8-1/2" x 8-1/2" x 4-1/2". Relay based. Switches between power sources automatically. Switch from power cord to generator by simply starting generator. Switch to inverter power by disconnecting generator and power cord. 25 second (nominal) delay allows necessary warm-up time before transfer and prevents starting the generator under load. Compatible with inverter load sensing circuitry, allows inverter to operate in automatic standby mode. No manual switching, no unnecessary battery drain.