This circuit is for 12 V batteries but can be used with batteries of other voltages by changing the zener diode. The trigger point is adjusted by R1. The operating system accepts equivalents.
An interesting application that can be implemented with the LM139 is the pulse width modulator. This is...
This circuit is from a 1956 Sylvania publication, using the company's transistor. The transistor is from...
This circuit was found in a 1980s documentation. Similar configurations appear in the section, but from...