This circuit is from a 1992 Electronics Handbook. The circuit consists of an alarm to be hung on a handle. The capacitance of the hand of the person who touches the handle triggers the circuit. BU1 is a buzzer and the SCR can be the TIC106. The transistors can be the BC548. The coil can be wound with about 30 turns of wire 20 in the form of an old transistorized radio FI with adjustable core. Capacitors must be ceramic.
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