Found in the October 1979 Radio Electronics magazine, the purpose of this circuit is to monitor the coolant level in a car's radiator. The circuit is based on the LM1830.
The LM150, 250 and 350 series are manufactured by several semiconductor industries that suggest...
This amplifier with gain control was obtained in a documentation from Signetics of the 80's....
The SCR sector of this circuit can be powered by high voltage AC and instead of the LEDs we can...