This circuit was found in the July 1986 issue of Radio Electronics magazine. The circuit has a loudspeaker warning system. The sensor is the ceramic capacitor C1 which acts as a transmission line.
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...