It’s the flip-flop, and while its ... to what they called a “trigger relay.” While their original papers show that they recognized the utility of a circuit with two stable states, and ...

If you need a circuit that converts a momentary push button to a latching switch with low standby current, this design might ...

it stores the value in the flip-flop. The next time a clap is sensed, the circuit is reset. Output is as simple as a LED and a buzzer, but once you have that, connecting a relay is a piece of cake.