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.
Based on Texas Instruments documentation, this circuit is based on the BQ2000 a circuit used to...
The circuit shown was found in a Japan publication from the 1960s. The transistors can be of any...
This circuit is from a 1977 documentation. It is powered by the power supply of the circuit under...