Euro standards in close-up

To keep you all informed since last month's article; there has been a change to the date of withdrawal for conflicting BS standards. IMPORTANT: the CENELEC BT committee has agreed to move the Date of Withdrawal from September 1, 2003 to March 1, 2004. This means that a breathing space is provided to issue the revised PD6662, which is still being worked on, and time to train people.

The final article was originally intended to cover PD6662. This document was published in 2000 and was intended to enable intruder alarm systems to be installed, which complied with the European standards available at that time. However we are not aware of any systems being installed in accordance with the requirements of PD 6662: 2000. The reason for this lack of enthusiasm for using this document was probably related to the fact that it was only possible to install grade 1 and 2 systems, as the detector required for compliance with grade 3 systems i.e. one capable of detecting "significant reduction of range" were, and still are, not available.

PD 6662: 2000 is currently being revised to reflect the publication of the Date of Withdrawal of standards conflicting with BS EN 50131-1: 1997. This date was originally given as August 30, 2003 but has now been changed to March 1, 2004 as mentioned above.

As PD6662 is still in a draft state it would be sensible to cover, in this article, another EN standard which will affect organisations installing intruder alarm systems. In this last article in the series we will therefore precis EN50136-1 (of which there are four parts) and EN 50136-2 (of which there are three parts).

You may have noticed that the number for this standard changes from the EN50131 series. This is because transmission systems are common to both Intruder and Fire systems.

Within the 50136-1 there are four parts:

• EN 50136-1-1 General requirements
  
• EN 50136-1-2 Requirements for systems using dedicated paths
  
• EN 50136-1-3 Requirements for systems with digital communicators using the public switched telephone network.
  
• EN 50136-1-4 Requirements for systems with voice communicator using the public switched telephone network.

Within 50136-2 there are three parts:

• EN 50136-2-1 General requirements for alarm transmissions equipment
  
• EN 50136-2-2 Requirements for equipment used in systems using dedicated alarm paths.
  
• EN 50136-2-3 Requirements for equipment used in systems with digital communicators using the public switched telephone network.

As we are limited for space in this article we will concentrate on EN 50136-1-1. This will set the scene for the requirements of the 50136 standard.

The logical configuration of an alarm transmission system is shown in Figure 1. This is not the only configuration possible. Dependent on the required reliability levels and alarm receiving centre's operational features, various system configurations are possible. This may include the use of more than one alarm transmission path between an alarm system and one or more receiving centres.

Selection of the type of transmission system to be used will be determined by the required level of reliability and security. Reference should be made to the required standards, where these exist, for each type of transmission system.

For purposes of transmission system "redundancy" it is permissible for a supervised premises alarm system to be connected to a remote centre by more than one type of transmission system, e.g. dedicated alarm transmission path system or a digital communicator using the public switched telephone network. Where a transmission network is used the alarm transmission path may only exist for a period of time for which the connection is established.

Transmissions characteristics
The transmission of the state of the alarm system will be:

• continuous
  
• periodic; and/or
  
• whenever the status of an alarm system changes.

If the transmission is not continuous then the control will be provided by:

• the alarm system; and/or
  
• the alarm receiving centre; and/or
  
• the alarm transmission system

Alarm transmission system classification
EN 50136-1-1 defines alarm transmission system characteristics. You will see from the following tables that for some specific characteristics a classification system or measuring scale is also introduced. These are applicable to a number of very different applications e.g. intrusion, fire and access control.

The requirement for each application should be specified and included for:

• transmission time
  
• maximum time
  
• reporting time
  
• availability time

It should also include requirements regarding:

• signalling security
  
• remote parameter modification
  
• access levels