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.
Equivalent transistors, such as the BC548, can be used in this circuit that we find in...
Found in a 90s documentation, this circuit makes use of D1, a switching diode that is uncommon today....
This is the suggested transmitter circuit for the CB16880E. The emitting LED must be a...