This circuit was found in a Radio Electronics magazine from June 1962. The circuit is for cars of the time with platinum ignition. The indication is made on an analog instrument.
The circuit shown is from an old European publication. In it we have the way to activate a relay...
We found this circuit in a European publication from the 1990s. Transistors are still common types...
This circuit was found in an American documentation and can be added to common amplifiers of any...