High voltage interface relays, a.k.a., interface relays: or coupling relays or insulating interfaces is a special class of electrical relays designed to provide informational and electrical compatibility between functional components isolated from each other and not allowing for a direct connection due to a high difference of potentials. A common design principle of these devices is a special galvanic isolation module between the input (control) and the output (switching) circuits of the relay. Interface relays are widely used in control and protection systems of high voltage (10-100 kV) electronic and electrophysical equipment and in high power installations.