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.
Found in an 80's Elektor, this circuit can use any equivalent optical coupler. The buzzer is of the...
This circuit with SCR and Unijunction and which can be assembled today with modern equivalents was found in a...
This circuit was developed to find intermittent defects in an electrical control. In the event of a...