http://www.machineguardsolutions.com/images/lightcurtain2.jpg [Broken] A light curtain seems like a basic communication system setup (TX & RX). But what kind of signal are you trying to send and receive? How should the receiving end get processed? How do you deal with crosstalk from using multiple transmitters and receivers? What is the best way to deal with aligning the IR transmitters and receivers? How far of a distance can IR leds transmit? I don't know much about IR technology as well as this particular application. So, any information or direction on the topic would be greatly appreciated. Book, articles, anything. I've been trying to search the internet but I am having a hard time finding material. Thanks.