Found in a 90’s Popular Electronics, this circuit generates sinusoidal signals with frequency controlled by an input signal. C4, C3 and C1 together with R12 and R3 determine the frequency generated.
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...