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 rarity is from a 1926 publication. The galena detector (D) can be replaced in a modern...
This circuit with transistors in parallel was found in a Radio Electronics of August 1952....
Found in a 90s documentation, this circuit appears in other configurations on this site. The...