This oscillator that generates signals below the audible range (sub audio or infrasound) was found in a 1965 documentation. Transistors are for general use.
This oscillator circuit for sinusoidal audio signals with operational 741 requires a symmetrical power...
Found in a 1974 Radio Shack documentation. This circuit must have a connection to the ground of...
This sensitive circuit detects the live pole of a power grid or outlet. The circuit makes use of a high...