What is a Photointerrupter?

What is a Photointerrupter?
A Photo interrupter is a transmission-type photosensor, which typically consists of a light emitting elements and light receiving elements, aligned facing each other in a single package.
Ir LED vs Photointerrupter
Ir LED is a photoelectric conversion element that converts electrical energy into optical energy. Photointerrupters combine a photodiode and transistor.
Types Of Photointerrupters
The two basic types of photointerrupters are the transmissive type (gap type) and the reflective type.