An H-bridge's an electronic circuit which enables a voltage to be applied across a load in either direction. These circuits are often used in robotics and other applications to allow DC motors to run forwards and backwards. H-bridges are available as integrated circuits, or can be built from discrete components. A "double pole double throw" relay can generally achieve the same electrical functionality as an H-bridge (considering the usual function of the device). Though an H-bridge would be pref… (More on H-bridge)