spnoSPNO, SPDT, DPNO, & DPDT General Purpose Switching Relay Relays control circuits through a low-power snal. An electro-magnetic current actuates the relay, creating a closed circuitSPNO, SPDT, DPNO, & DPDT General Purpose Switching Relay Relays control circuits through a low-power snal. An electro-magnetic current actuates the relay, creating a closed circuit