This MOSFET circuit for microphone applications was found in the December 1969 issue of Radio Electronics magazine. The transistors are uncommon today.
This oscillator from an old publication uses one of the first commercial transistors, the CK722....
The integrated circuit used in this configuration is not common today. The zener determines the...
With good filtration, a battery charger can be used as a power source. The filter shock can be the...