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.
This circuit was found in Radio Electronics magazine from August 1966. The transistors are from...
We found this circuit in an old documentation for radio amateurs. The circuit uses an analog...
This circuit is found in a 2005 Linear Technology application manual. The circuit monitors the High...