Home - FAQs - Key Points

• 4.1 Design Objectives
• 4.3 Transmission Fault Signals

Section 5     Design, installation and configuration of intruder alarm systems

• 5.4.1 Criteria for sequentially confirmed alarm conditions
• 5.4.2 Configuration of movement detectors that may offer a sequentially confirmed alarm
• 5.4.3 Configurations not regarded as offering a sequentially confirmed alarm condition

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 6
Other means of minimizing false alarms

6.2 Alarm Filtering
All IASs must EITHER:

a)    have the means to indicate to the ARC whether the IAS is set or unset;
        OR
b)    be capable of generating a secondary signal identifiable at the ARC as a mis-operation signal.

These requirements remain the same as under the NACP 14 and the previous DD243: 1999 document.

The filtering period (maximum 120 seconds as recommended in BS5979) will apply from the first, unconfirmed activation and will continue to run even in the event of a second, confirmed activation during the filtering period.

There are a series of conditions that mean that alarm filtering can be over-ridden. All four must apply and these would only ever be effectively possible on some commercial systems. The four conditions are:

1)    Set/Unset monitoring in use
2)    Alarm at least 30 minutes after latest agreed setting time    
3)    Alarm at least 30 minutes before earliest agreed unsetting time
4)    System set at least 15 minutes before alarm occurs

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6.3 Means of Completion of setting

The six permitted options for completion of setting IASs are as follows:

a)    Key operated shunt lock fitted to final exit door
b)    Push button switch mounted outside the protected premises
c)    Protective switch (ie door contact) fitted to the final exit door
d)    Portable ACE
e)    In conjunction with an ARC
f)    In the case of systems installed to comply with BS EN 50131, other means.

The traditional timed exit method of setting is now not allowed under DD243 unless the set period is completed by the means of a push-to-set button or final door set using door contacts.

Other methods are now acceptable including completion of setting using portable ACE (ancillary control equipment).

It is worth noting that means of COMPLETION of setting is not the same as means of setting. For example a traditional end user code entered into a Remote Keypad (such as the Pyronix MX-LCD) is acceptable, provided the completion of the setting procedure is by a push-to-set button or by door contacts on the final exit door.

Where systems are installed to EN 50131, setting from outside the protected premises is permitted.

Whatever method is chosen, there should be a time-limited indication to the user that the setting has been completed. This may be audible i.e. the cessation of the exit tone.
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6.4 Means of unsetting
There are five options for means of unsetting under the DD243 policy.

a)    Unlocking the initial entry door unsets the IAS
b)    Unlocking the initial entry door disables all means of confirmation
c)    Opening the initial entry door disables all means of confirmation
d)    Completion of unsetting is achieved using portable ACE
e)    Unsetting is carried out in conjunction with an ARC

This section is possibly the one that will have the biggest impact on many installation companies.

The traditional timed entry route, with the end user entering their code at a remote keypad, is no longer acceptable.

Options (a) and (b) require an electrical connection between the lock and the IAS. For example an electric lock or a shunt lock may be used. Electronic access control liked to the IAS is also acceptable.

Option (c) is obviously the one that leaves greatest risk as a forced entry through the entry door would disable confirmation! It is unlikely that this method of unsetting will be acceptable to insurers for all risks. Furthermore, if this method is adopted the installation company must advise the customer in writing that all confirmation is disabled when the entry door is opened. They must also obtain, from the customer, in writing; that this is acceptable.

Option (d) will allow the use of an entry timer in conjunction with portable ACE (such as the Pyronix Prox) The portable ACE can be self-powered or can be in the form of a proximity tag or card. It must be a single action device to unset the system (such as presenting a tag or card to a proximity reader) and must offer security of no less than that provided by a key switch of 1,000,000 differs.

Where a portable ACE is used however, there are points worth noting with regard to confirmed alarms involving the entry route.

If the entry time expires without the IAS being unset, an unconfirmed alarm will be signalled to the ARC. At that point the ARC will apply the alarm filtering delay.

If a detector off the entry route subsequently activates a further unconfirmed alarm will be signalled to the ARC. Only on activation of a second, independent detector will a confirmed alarm signal be able to be sent to the ARC.

Where detectors off the entry route activate during the entry time, it is considered likely to be due to user error and these will not signal an alarm to ARC, but would cause a local alarm.
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