We found this active crossover in a Radio Electronics magazine from June 1961. Note the different adjustment ranges. The signal must be applied to the amplifier input.
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...