This circuit can be used to test crystals from 1 to 20 MHz and also has an output to measure their frequency. We found it in the November 1998 Electronics Now magazine.
This circuit was found in documentation from 1977. Its purpose is to diode-switch the frequency of a VFO....
This circuit is from a 1974 Ferranti transistor manual. The circuit is analog, and the components used...
Found in a 90s Popular Electronics, this circuit generates high voltage for radiation detecting...