This circuit activates a relay when the supply voltage drops below the value set in the trimpot. The transistors can be the BC548 and BC558 and the 6 V relay. The circuit was found in a 1999 Poptronics.
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...