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 oscillator from a 1970 documentation uses an operational amplifier that is no longer common on...
The integrated circuit used in this 90's circuit is not common today, but the configuration can be...
Found in a 70s RCA manual, this circuit uses a transistor of the time for an UHF L band...