As expected, there is interference when two of these can see each other.
I started out with the obvious configuration below.
I set the range to sense about 6-8" and fired the two up. About every 15 seconds at a somewhat random time, one or both would trigger.
Next I pointed them at a 45 degree angle at the parts cabinets you see at the top of the shot, and it was pretty much the same, slightly less often I'd say. Finally, I moved them about 4 feet apart and pointed at the cabinets or straight on they still triggered in a similar manner.
The last test was point them out where there was about 7-8 feet to the first obstruction, they didn't trigger at that point, at least for around 10 minutes.
An obstruction placed in front of one but out of the sensing range did seem to block the signal and the other unit stopped randomly triggering.
Obviously, the use of these would have to meet some guidelines on positioning.
OTOH, they seem dead reliable triggering on a lot of different surfaces.
