In the figure we have a basic PLL circuit with the LM567 or equivalent. The circuit is from a 1977 documentation.
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...