This circuit is from the time when cars used contact breakers. This 80's version measures the dwell angle of the contact breaker for dwell adjustment using an era integrated circuit, the LM3917.
This circuit makes use of high voltage transistors and can be connected to the 110 V (117 V)...
This selectivity multiplier circuit for 455 kHz IF receivers was found in American documentation from the...
Found in a 90s Popular Electronics, this touch switch uses a single sensor. PLLs are common today....