This circuit indicates when the voltage of a 12 V battery is low. With changes, for example, the zener, the circuit can be used to monitor other voltages.
Found in a 90s 73 magazine for radio amateurs, this circuit makes use of common operational...
We found this circuit in a Popular Electronics from the 90s. Transistors can be modern...
The 4046 PLL is uncommon these days. This circuit was found in the August 1994 issue of...