Hmm, not sure on this 7 core cable idea. You can put several pir's on the same zone just wire them in series the same way the tamper circuit is done, using 6 core cable; 2 for power (continue to next pir), 2 for tamper (in series), and 2 for the alarm (in series). Not sure wher the 7th core gets used.
Mike T
December 2011