Using an analog microamperimeter this circuit has a phototransistor adapted to the wheel as a sensor. The circuit is from American documentation from the 1980s, but the components are common today.
This old configuration of an audio amplifier has a push-pull two-transistor output stage. Output...
This is the traditional configuration of na Astable Multivibrator using two NPN ttransistor....
This circuit is from 1987 documentation. The operating system used is not common today, but two...