Indicated for 12 V systems, this circuit was obtained in a 90s Siliconix documentation. The components used are from the time and current equivalents can be tested.
This experimental amplifier was found in the 1960 Mullard transistor reference manual. The...
This circuit from Motorola is from 1968, appearing elsewhere on this site. The transistors admit...
This circuit triggers the LED when the monitored battery voltage drops below 9 V for 12 V...