The following are what we feel are the key points of the DD243 policy. This is not
a definitive list and should not be seen as the limit of an installation company's
responsibilities, merely as a guide to some of the main issues.
CONTENTS
Section 4 Primary design and configuration
considerations
- 4.1 Design Objectives
- 4.3 Transmission Fault Signals
Section 5
Design, installation and configuration of intruder alarm systems
Section 6
Other means of minimizing false alarms
- 6.2 Alarm Filtering
- 6.3 Means of Completion of setting
- 6.4 Means of unsetting
Section 5
Design, installation and configuration of intruder alarm systems incorporating alarm
confirmation technology
5.4.1 Criteria for sequentially
confirmed alarm conditions
The general criteria for the way an IAS is configured for an alarm condition to
be sequentially confirmed is as follows:
a) At least two separate alarm conditions are reported, each originating
from an independent detector, within the confirmation time; and
b) The two detectors must be:
EITHER of different technologies
OR (if they are of the same technology) the two detectors must not have overlapping areas
of coverage.
The detectors must have separate outputs and be connected to separate zones in the control
panel. Although two separate zones must be used, the detectors can be in the same area, or
room.
The 'confirmation time' is the term used for the period of time after the first
activation, during which a second, or confirmed, activation can be reported. The
confirmation time must not be less than 30 minutes and must not be more than 60 minutes.
Two detectors of different technologies (such as the Pyronix Veritec P2) are allowed. Two
detectors of the same technology are also allowed provided that those detectors do not
have overlapping areas of coverage.
Where both detectors are movement detectors further rules apply under the following
section:
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5.4.2 Configuration of movement detectors that may offer a
sequentially confirmed alarm
In simple terms, the key points from this section are as follows;
Where any two movement sensors are used (single technology or dual technology) and they do
not have overlapping areas of coverage, they should be located far enough apart to
minimise the possibility of false alarms. (NSI suggests 2.5m)
In the case of two movement detectors, with any overlapping areas of coverage, at least
one must be a dual-technology detector. The overlapping areas of coverage should be at the
far end of the field of view, to minimise the overlapping coverage areas and thus, the
likelihood of false alarms. Again these detectors should be mounted 'some distance apart'.
Two separate dual-technology movement detectors with overlapping areas of coverage are
allowed, providing the above criteria is met.
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5.4.3 Configurations not regarded as offering a sequentially
confirmed alarm condition
This section describes other configurations that are not acceptable under the DD243
policy.
These are basically as follows:
A 'double knock' configuration
A 'dual-technology' detector
Two (or more) detectors or devises of the same type with overlapping areas of coverage
including: -
- Two vibration sensors
- Two glass break sensors
- Two foil-on-glass detectors
- Two door contacts (or similar)
- Two audio monitoring devices
- Two video motion detection devices
- Two or more detectors responding to changes in
atmospheric pressure
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