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 is the basic operational amplifier configuration for gain 10. R2 can be changed to other...
This circuit uses a capacitor that depends on the frequency of the crystal. We found it in a 1967...
The crystal frequency of this circuit found in an American documentation is limited only by the...