This circuit was found in an English magazine from August 1982, but it can be easily assembled with some changes. The first is to use the BC548 for TR1 and TR2 and the BC558 for TR3 which in the original scheme meets the NPN arrow when in reality it is PNP. The circuit triggers an oscillator when the sensor is touched. Never supply this circuit with a source without a transformer. The circuit will work with an 8-ohm speaker without the need for a transformer.
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