Found in American documentation from the 90's, this circuit is very current and can be implemented with transistors of general use. Never use a power supply without a transformer.
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...