This circuit was found in a 1976 documentation. We can assemble it with equivalent transistors, for example, the BC548 for the bipolar. The critical component is the oscillating coil that can be tested with 30 + 30 turns of wire 28 in a 1 cm diameter tube. The relay must be of the high sensitivity reed type with a trigger current of 1 mA. The adjustment pot R2 can be 47 ohms and R3 220 ohms, both of wire.
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