Clap Switch

Here is a Hobby Circuit for electronics hobbyists that can switch on & off a light, Fan, Radio etc. by the sound of clap. The sound of clap is received by a small microphone The microphone changes sound wave in to electrical wave which is further amplified. Amplified output  is then feed to the Bistable Multi vibrator circuit also known as flip-flop circuit.
Flip flop circuit is made by using 2 Transistor,  In a flip-flop circuit, at a time only one transistor conduct and other cut off and when it gets a trigger pulse from outside source then first transistor is cutoff and 2nd transistor conducts. Thus output of transistor is either logic-0 or logic-1 and it remains in one state 0 or 1 until it gets trigger pulse from outer source.
The pulse of clap which is a trigger for flip-flop which makes changes to the output which is complementary (reverse). Output of flip-flop which is  connected to a Relay (Electromagnetic switch) which works like a mechanical switch and it becomes easy for connecting other electrical appliance.
The relay contact is connected to the power line and hence turns on/off any electrical appliance connected all the way through relay.