This circuit for light modulated in frequency (FM) operating at 50 kHz was found in a 90’s Electronics Now. The circuit has an active filter. Modern equivalent transistors can be used.
This circuit for the power grid was found in the June 1969 Radio Electronics magazine. The load is...
July 2017 - Microchip's new MCP9V91 operational amplifiers with input offset and low drift voltage...
Found in the August 1970 Radio Electronics magazine, this circuit uses a CA3018 with the trigger...