Replacement PIR for Scantronic 9449 alarm

One of the PIRs in my alarm system has died. Odd failure in that it appears to be a faulty contact in the reed relay - I can hear the relay operating, but the contacts are permanently O/C and the alarm shows a fault in that zone when set.
So, I 'liberated' an unused PIR from one of my sheds and installed that in place of the duff one and promptly blew the fuse for the 12V supply to the PIRs - thought I'd killed the whole system as NOTHING worked after that, but replacement of the fuse cured that. Checking the wiring revealed dodgy jelly crimps which I had disturbed when swopping PIRs. I've replaced _all_ the dodgy wiring and find that the liberated PIR seems to work, in so far as the red LED lights when the PIR detects bodies. I have not connected the signal leads as the N/C circuit appears to be referenced to OV via a transistor unlike the dead PIR with it's reed relay.
The installation manual for the alarm doesn't say whether I can use a PIR that doesn't use a reed relay for signalling.
Can I use any old PIR - as shown in my trusty TLC catalogue (pp 198-199)? If so, how do I choose one and are there any polarity issues if I use a PIR with a transistorized switch? There doesn't seem to be any indication on the control board as to how the contacts/PIRs are referenced wrt to OV
The PIR is located in the corner of a 3.5 x 6.0 m room. The cat is excluded from the room when the alarm is set. There is a radiator and an open fireplace.
The dead PIR is labelled REX VISONIC.
Incidentally, the manual refers to installing a 2 parallel 16 ohm speakers for monitoring internal sounder or EE tones. At one part of the manual this is described as essential, whilst another part suggests that it is optional. Views?
TIA
Richard
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Jelly crimps are for solid core cable, whereas alarm wiring is usually stranded cable.

Most have volts-free contacts, but some of the very cheapest use an open collector transistor ouput. I always use dual-techs, which avoids the cheap end of the spectrum ;-)

Sorry, not familiar with that alarm.
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Andrew Gabriel

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Andrew Gabriel wrote:

Well it was installed by a professional alarm installer (I'm not joking, I have the certificate to prove it). Judging from the ghastly mess of wiring I'm surprised it ever worked.
The 9449 is, according to the manual, a domestic/small commercial 8 zone unit cpable of driving an auto dialer and having up to 4 control pads and ofering part/full set! So there!
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On Mon, 07 Aug 2006 19:54:13 +0100, Richard wrote:

The one in my house is a 9452 which is likely very similar? A couple of PIRs started to go wrong a few years ago they were then about 10 years old. So I replaced all the rest in one go.
Generally the PIRs are the same from most makers they have a contact pair to signal that they have detected, 0 and +12V DC for power and another pair normally closed until you open the case for tamper.
Doubtless if you have the full service manual you can tell the box to let you do maintenance on it. I simply kept entering the reset code until it stopped complaining about my open the PIR units.
HTH
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Ed Sirett - Property maintainer and registered gas fitter.
The FAQ for uk.diy is at http://www.diyfaq.org.uk
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Hi Ed
Ed Sirett wrote:

Probably
yes but some are solid state whilst others are relay isolated.

Do you have know how to change the user and engineer codes or how to reset them to factory values?
Richard
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