Abstract: A solid state circuit providing the function of a ratchet relay which circuit is relatively immune from noise and is capable of high speed switching operation. The circuit is adapted to receive an AC input trigger signal and convert such signal into an appropriate signal for alternately firing a pair of triacs that are each serially connected with a load and an AC power source. The circuit includes an input section comprising an AC to DC pulse converter, a time delay network, and a pulse shaping circuit which provide a clean input pulse to trigger a flip-flop and an output section including an opto-isolated Darlington transistor pair which is provided with a separate power supply and which operates to alternately fire the triacs in response to the output state of the flip-flop.