This circuit uses a 7-segment display to indicate the logic level of a test circuit. The power supply is made with 5 V that can come from the analyzed circuit itself.
This circuit triggers the LED when the monitored battery voltage drops below 9 V for 12 V...
We found this circuit in a Radio Electronics from January 1967. The SCR is already the C106, which...
This power source with silicon diodes at a time when valves were still used was found in Radio...