[cross-posted to uk.tech.electronic-security]

In article ,
"CJ" writes:
On a technical front, PIR detectors can last over 15yrs but deteriorate with
age becoming hyper-sensitive causing false alarms.
Dual tec devices start to fail mainly because the microwave antenna corrodes
(especially in damp or cold locations like garages) this causes the device
to go out of tune giving false alarms.

I have tried a number of them...

Focus Dual-tec: 7 out of 8 failed within 3 months and returned.
The one remaining one is still working fine 12 years later.

Pyronix Equinox Dual-tec: No failures in 12 years, but have had
to increase sensitivity on one in a cold location.

Guardall Astra Micra dual-tec: No failures in 12 years.

Pyronix Octopus 360 degree PIR-only: They all lasted about 5 years
before starting to generate false alarms.

Scantronic 460 dual-tec: too soon to say, but no problems in 6 months.

AEI 360 degree PIR-only (CPC): too soon to say, but no problems in 6 months.

[...]
From the above it becomes clear that to guarantee everything works a company
must regularly check the system and would not normally take on a DIY
install.
We all know this is not always the case but hopefully you can see why nobody
will touch a DIY system.

or even a system installed by another alarm company, unless they're
doing a bulk take-over of all their business.

--
Andrew Gabriel
[email address is not usable -- followup in the newsgroup]