This circuit uses the LM2931 which is not a common component today. What it does is to activate a lamp causing it to blink at a frequency determined by the capacitor.
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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...