the thieves guild used to have burglary as a 2 man job, sensors wired in parallel would detect 2 men in the 2 separate rooms at the same time.
I blame thatcher for breaking the unions ever since the poor alalrm monkey ensure they did their zone in series or one devices a zone.... bitch
as I said wire it correctly and it will function, but you need a latching sensor in one place to know which one triggers. Best way is to have a panel that has enough inputs for your detectors. Also get builders to build, get an alarm specialist to do alarms.