This circuit is from an old American documentation from the 70s. Transistor 2N3904 can be replaced by BC548. The relay must have 100 mA of maximum current.
This circuit from the 70's used germanium transistors and operated in the range of medium and...
Found in a 1965 Electronic Design, this circuit produces a signal with the waveform shown in the...
Unlike the previous detector circuit, this includes the inverter not requiring a high voltage...