Photoelectric barrier

Hello,

I am new in this forum and a beginner in electronic, I want to use a photoelectric barrier.

I dont know which dropping resistor have to use!

Can you help me?

http://agelektronik.de/lichtsensoren/6977-infrarot-drehzahlsensor-4-pin-fur-arduino.html

Resistor for what?

The thing advertises it has an LM393 comparator on board, which implies it has a push/pull output that can go straight to an Arduino pin.