This sophisticated circuit with two LF411 operational amplifiers appeared in the November 1984 issue of Radio Electronics magazine. The circuit uses a Mallory buzzer as an indicator.
Originally this circuit was designed to power tube transceiver equipment in the car, using a 12 V...
This circuit is from a Radio Electronics from February 1966. The circuit is of a type that was...
This circuit is from a Japanese publication in 1967. The circuit uses a Geiger-Muller valve and...