This circuit is from a 1967 documentation. It makes use of varicap and diode tunnel in addition to currently uncommon FET. It serves as a reference.
This circuit triggers the LED when the monitored battery voltage drops below 9 V for 12 V...
Suggested by National Semiconductor, this circuit can be applied to almost any operational...
This circuit was found in Radio Electronics from the 90s. The circuit can generate signals up to...