This circuit is from an August 1984 Radio Electronics magazine. It monitors the state of a RAM backup battery. Resistor R1 determines the battery charge.
In the figure we have an improved method of varying the voltage of a 7812 regulator. The circuit is...
This 5-range current measurement circuit was found in the September 1989 issue of Radio...
Found in an old English publication this circuit uses a dual gate MOSFET. Coils not specified....