With this circuit it is possible to use a frequency meter as a tachometer. The circuit was found in American documentation from the 90s. The phototransistor can be of any type.
It is an interesting toy containing several potentiometers and switches, allowing children to...
This NEC commercial amplifier was manufactured in Japan in the 1960s. The circuit uses 4...
In the figure we have an application of a voltage comparator in a circuit that fires with the...