its straight forward, but could be better drawn.
You connect your power to the four terminal and from there you also connect power to the transmitter (2 terminal), making sure that voltage and polarity are correct.
Then you set the jumpers to normally open or normally closed as suits your application.
If you select normally open : when the beam is broken the relay is closed (COM is shorted to OUT)
So if you connect 5v from your Arduino to COM and OUT to pin2, you can then use attachinterrupt on pin 2 to detect every time the beam is broken. (However, read up on avoiding bounce on switches to avoid counting a single break more than once)
For anyone interested in IR protocols – we have just launched a Crowdfunding campaign on IndieGoGo for AnalysIR – IR Decoder & Analyzer (Arduino & Raspberry Pi). Currently we support 17 IR protocols and are looking for more to add as part of the campaign. Suggestions Welcome!
You can find out more about the Campaign on http://bit.ly/1b7oZXH
or Screenshot via www.AnalysIR.com