We found this circuit at Popular Electronics. The components are still current. Changes can be made to obtain higher voltages, as indicated in the second diagram.
This circuit was found in an English documentation from the 90's. Equivalent components such as...
This circuit was found in an Electronics Now of the 80s applying to NiCad batteries of the time....
The pulses applied to input C of the SAA1027 integrated circuit determine the engine speed. Each...