This circuit makes use of a 741 single source operational amplifier to measure resistors on a linear scale. The circuit may use as an indicator a common multimeter on a low current range.
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...