This circuit uses a resonant reed relay to recognize the frequency of an input signal. Adaptations can be made to obtain functioning as a shield. The circuit is from 1965 documentation.
This single transistor radio without a power supply was found in documentation from the 1960s. The...
With this circuit it is possible to control a current of several amps, depending on Q1, from a low...
This small low current inverter operates at 20 kHz frequency. We found it in documentation from...