The circuit is a voice controlled circuit. It consists of a Microphone to sense the sound or voice. When any sound hits the Microphone, it energizes the relay. The sensitivity of sound intensity to energize the relay can be adjusted by the variable resistor Rp placed across the Mic. The sensed sound is converted to electrical signal by the Mic. The converted electrical signal switches the Transistors. These transistors energizes the relay which is connected across the diode IN4001.
The circuit can be connected in banks, treasuries or at any places for security purpose.When it is connected with a siren,the siren gets energized when the circuit senses any sound. It can be used as clap switch for lighting arrangements also. The relay can be connected with any electrical appliance to activate the electrical appliance.