This highly sensitive circuit was found in a 1967 General Electric SCR manual. Equivalent components can be used.
The operational amplifier is a type introduced at the time by RCA. The circuit is from a Radio...
This project is from a 1982 documentation, based on an astable multivibrator with two transistors. The...
Found in a 1968 Motorola publication, this circuit generates a high-powered audio tone when...