Found in an American documentation from 1969, this astounding circuitry makes a relay operate on 3 Hz cycles. The relay is of the high voltage type of the time.
This circuit, shown in the figure, consists of a variable gain amplifier with differential input...
This circuit releases a lock only if the correct 4-digit sequence is entered. The circuit uses...
Found in documentation from the 1980s, this circuit generates signals that can reach a few...