The Reverse Y Adapter has two male plugs with special power isolation circuitry for added safety. When one plug is connected to a receptacle, the circuitry isolates the second plug. The reverse Y provides 50A 125/250V power when only two 30A 125V receptacles are available. Note: Reverse Y will NOT work with 50A, 125V, 3-wire inlets. Power is provided in both circuits to the 4-wire inlet, but the dock side receptacles limit the current in each circuit to 30A. The two 30A 125V receptacles must be supplied from a single power source providing from 208V to 250V between them for proper operation.