This circuit was found in a Popular Electronics documentation from the 90s. It is possible to switch the frequency of an oscillator by voltage. The circuit can act as a shield.
This circuit is from 1968 General Electric documentation. It can certainly be adapted for any...
This tester from a 1960 magazine is only for capacitors with insulation voltages above 200 V (110...
Found in a 1991 publication this circuit can be assembled with more modern components. We can use...