Indicated for the protection of three-phase systems, this circuit was found in an American documentation of the 70's. The circuit can be implemented with modern components.
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...