The Solid State Relay Module Fotek SSR 40 DA allows you to control high current AC loads from lower voltage DC control circuitry. Solid-state relays have several advantages over mechanical relays. One such advantage is that they can be switched by a much lower voltage and at a much lower current than most mechanical relays, and since there are no moving contacts, solid-state relays can be switched much faster and for much longer periods without wearing out.