Quoted from neurokinetik:If this turns out to be a "parts no longer available" issue, there is an alternative that should be able to be made to work.
http://www.bannerengineering.com/en-US/products/8/Sensors/23/Compact-Photoelectric-Sensors/57/MINI-BEAM-Series/
I've used these sensors for timing applications, and they are typically 15 feet apart. The ones we use also happen to run on 12VDC.
Does the BSD opto use a lens?
Excellent photo eye....