This circuit was obtained from an Electronic Design from the 90's. The circuit generates signals at a frequency determined by R and C. The selection by the jumpers determines the PWM modulation.
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...