In article ,
Dave wrote:
that would be handy - I might change our 3 PIRs to these immune ones if
they arent too expensive

Some give you a choice of lenses - the idea being to avoid ground level
and therefore pets. Of course, cats can jump up on things. But if yours
are this type you might be able to buy the lenses only and experiment.
A pal who had several cats avoided PIRs altogether and relied on shock
sensors. But had loads of false alarms.

IMHO, if you can be bothered with the work, sensors on all the external
doors and windows are pretty reliable, unless you are 'attacked' by a pro
burglar.

--
*No husband has ever been shot while doing the dishes *

Dave Plowman London SW 12
RIP Acorn