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 circuit is from a 1967 General Electric SCR manual. The capacitors are polyester and the...
This oscillator for frequencies up to a few tens of kilohertz was found in a 1970s documentation. The...
This varicap-less modulator circuit was found in an Electronic Design from the 90's. The circuit...