The special reverse Y adapter features special power isolation circuitry, so if one plug is connected to a receptacle, the second plug is isolated so no power flows through it. The Y adapter provides 50A 125/250V power from 2 30A 125V receptacles. Female end has a sealing collar system. (Note: The reverse Y adapter will not work with 50A, 125V, 3-wire inlets.) Power is provided in both circuits to the 4-wire inlet, but the dockside receptacles limit the current in each circuit to 30A. The two receptacles must be supplied from a single power source and provide from 208V to 250V between them for proper operation.