This circuit from an old 1978 publication uses germanium transistors but can be implemented with more modern transistors. The transformers are obtained from radios and transistorized recorders of the time. BC548 transistors can be used in the circuit. The lamp can be 6 or 12 V if we change the voltage to this value, but it must be of type for a maximum of 100 mA. The sensor consists of wires with peeled ends. Do not use a source without a transformer to power this circuit.
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