We found this circuit in a 1965 publication by General Electric. The zener is 8.2 V x 1 W and the table shows the capacitor values according to the number of cylinders in the vehicle.
This series and parallel sensor circuit was found in Popular Electronics from the 1990s. Any SCR...
This circuit was found in a 1973 documentation, being able to use any general purpose NPN...
This circuit was found in a 1974 documentation. The bipolar transistor can be the BC548 and at the...