This circuit uses an unusual PLL, the 4046 CMOS. We found it in the October 1994 issue of Electronics Now. The circuit also uses a 4093 gate as a trigger.
This circuit uses a variable transformer available at the time. This turns of the windings were...
This simple indicator is for 12 batteries, just adjust the trigger point in the trimpot. The...
This 3-transistor circuit is from a Radio Electronics magazine from May 1963. The transistors used...