Undervoltage detector with the LM3900 (CB25172E)

The figure shows how to implement an undervoltage detector using a Norton amplifier and a zener diode as the main elements.

() CB8710E Turns on and off with SCR
We found these circuits in a 90s Radio Electronics. In them, we have the way to turn a load on and...
Multi-pulse trigger (CB21477E)
This circuit was found in a 1967 EEE. The transistors are from the time and can be tested...
Optical Explorer (CB14990E)
This circuit uses a photodiode or a phototransistor as a sensor. When pointed at a light source it...