Found in a Popular Electronics from the 90s, this circuit uses components that are still current. The circuit triggers the vehicle's horn. The sensors can be increased in number.
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...