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.
Found in a 1967 documentation this circuit can be applied to any operational amplifier. Components...
Mouser Electronics has in stock the MUSBR robust connectors for USB 30 applications from Amphenol. These...
This interesting transistor configuration, which can be seen elsewhere on this website and in this...