We found this circuit in a 1998 publication. The circuit has controls for both frequency and signal strength. A lamp is used to monitor the signals. The supply is made with a voltage of 12 V.
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...