This 80's circuit can be implemented with modern equivalent FETs with lower on resistance. The attenuation is 80 dB at 100MHz.
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...