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.
Found in a 90’s Popular Electronics, this circuit applies to almost any operational amplifier. With...
This circuit is suitable for calibrating old oscilloscopes. It was found in a 1980s documentation. It...
We found this circuit in the April 1979 Radio Electronics magazine. Note the filter capacitor bank...