Found in Popular Elecronics, this configuration also appears in this section, but obtained from other sources. The 14.4 V supply allows the circuit to be used in the car.
This simple indicator is for 12 batteries, just adjust the trigger point in the trimpot. The...
This circuit was found in an American 1980s documentation. The circuit can be digitally programmed...
This small tone generator was found in the November 1987 issue of Radio Electronics magazine. The...