WB75-A 110V 50Hz / 110-127V 60Hz / 110V DC is a mechanical latching unit used for converting standard contactors into latched contactors. The WB75-A block contains a mechanical latching device with electromagnetic impulse unlatching (AC or DC) or manual unlatching. After closing, the contactor continues to be held in the closed position by the latching mechanism should the supply voltage fail at the contactor coil terminals. Contactor opening can be controlled: • electrically by an impulse (AC or DC) on the WB75-A block coil. (the coil is not designed to be permanently energized) • manually by pressing the pushbutton on the front face of the WB75-A block.