This circuit is from American documentation from the 1980s. The circuit can make use of any common NPN transistor and the power comes from two small batteries.
This is a Japanese commercial circuit found in a 1967 documentation. The transistors are from the...
This circuit was obtained in the publication 101 Electronics Projects of 1979. The circuit can be...
This control of DC motors for currents up to about 200 mA was obtained in an American publication of...