This is rather frustrating. There is a horizontal "beam" and a diagonal one going to the ground. Both these need to be broken to activate the alarm. A dog would only be able to break one beam unless its big enough and stands upright to break both beams at the same time. Well that is what they say on the packaging. With cats jumping they easily break both sensors while jumping over the wall.

I have another PIR to install but now hesitant for the false alarms. Need to find a way to get the cats off the property.