Installers may get puzzled about radio frequencies for UK wirefree alarm systems. But who controls these frequencies? Ashley Thomas answers some frequently asked questions

Who controls radio frequencies?

Ofcom currently controls all radio frequencies used for all applications in the UK. Ofcom has inherited the legacy of several other regulatory bodies including the Radiocommunications Agency, which controlled frequency allocations until December 29, 2003.

Ofcom and the Radiocommuni- cations Agency have altered the radio frequency allocations for many applications over the years to meet the ever-changing needs of users, while trying to avoid interference between frequencies used in different products for different applications. In today’s world when many demands are made for more wirefree products, the available radio spectrum is now more crowded and needs to be controlled more carefully than it ever has been before to prevent clash between users.

What frequencies are commonly used for UK wirefree alarm systems?

In the UK four frequencies have commonly been used for wirefree alarm systems: 173.225 MHz, 418 MHz, 433.92 MHz & 868.6625 MHz. Others are available for certain alarm applications.

Why have some manufacturers changed their operating frequency?

This is due to a frequency allocation change at 418 MHz by Ofcom & the Radiocommunications Agency. The radio spectrum in the 410 to 430 MHz band is now identified for the use of civil TETRA, a mobile tele-communications service operating to a European harmonised standard.

This means that the current frequency allocation used for wirefree alarm systems at 418 MHz will be withdrawn. Equipment on this frequency should only have been placed on the market until December 31, 2002. Systems supplied before December 31, 2002 will be accepted for use in the UK until December 31, 2007. After December 31, 2007 the band is expected to be re-assigned for use by TETRA.

New equipment or systems using the 418 MHz band will not be able to be placed on the UK market. How-ever, existing systems using the 418 MHz band may continue operating in that band provided they do not cause interference to the TETRA network.

Please note: Currently, there is no requirement to change systems operating on 418MHz if they are functioning correctly.

Will BS EN 50131 affect the frequency used on alarm wirefree systems?

EN 50131-5-3 is the section of the standard referring to requirements for interconnections equipment using radio frequency techniques. This document is not currently published as a standard, however the current draft version of this document refers to the assigned band, which is the frequency band within which the equipment is authorised to operate.

I am informed that the frequency allocation is outside the scope of the TC79 committee which is responsible for the development of security standards including BS EN 50131.

In the UK, Ofcom now allocates frequencies so any currently allocated frequency can be used provided it meets all the other appropriate requirements of the standard.

If you wish to export products outside the UK, contact the manufacturer before you place the order to ensure the frequency and necessary approvals supplied are suitable for the destination country.

Which is the best frequency?

This is a difficult question to give a direct answer to, as the answer will vary from application to application, as no two buildings are ever exactly the same. Within buildings the different frequencies will tend to travel (propagate) in different ways. As a simple general rule: the lower frequencies will find their way through the building walls etc more easily, and higher frequencies will find their way through small spaces more easily.

In practice, if a system on one frequency does not work, another on a different frequency might. At other times the equipment location just needs changing by a very small amount to make the difference bet-ween a system that will operate successfully and one which won’t. In some locations a radio-based system may not be suitable due to other influences, e.g. electrical noise or other transmissions already present from other systems operating in the area.

Most manufacturers will provide a means of checking signal strength and background noise. I strongly recommend checking this with transmitter and receiver devices and their remote aerials if appropriate in their exact proposed locations before you mount any device in its final location. Sometimes even a very small amount of movement at either end can make a large difference to the final signal strength.

Would you like further assistance?

Most manufacturers offer technical support lines. Often a quick phone call to a person who is familiar with the product you are working with will provide you with the answers to most of the problems you will come across during both survey and installation. If you are interested in finding out which frequencies are allocated for which applications go to www.ofcom.org.uk as Ofcom is the regulator for the UK communications industries, with responsibilities across television, radio, telecommunications and wireless communications services.

  • Ashley Thomas is technical sales engineer with FM Electronics Ltd, Forest Vale Road, Cinderford, Gloucestershire GL14 2PH. Tel 01594 827070. ashleythomas@ fmelectronics.co.uk
  • Take a look at the following range of wirefree products available and specify one for your next installation.

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Go to www.security-installer.co.uk/enquiries and key in the number of the products of which you would like details

What a combination!

FM Electronics’ recent addition of the Pet Tolerant detector combined with the FM4040 Universal Class 6 interface has provided a very successful solution for many installers adding to existing wired systems.

This combination can work into any panel with sufficient available zones for the application and provides all the outputs required to meet current requirements for police response.

The interface will operate with any of the 4000 series detection devices including door contacts, inertia sensors and a range of PIRs. The Pet Tolerant unit has the ability to ignore a pet up to 25kg in weight, but still provide effective detection throughout a 12m 90 degree area.

The Class 6 Universal interface and wirefree detector combination has been proven to provide a reliable radio link up to 100m.

Reader Service No 103

Immunity from interference

The standard Freewave system from CQR is easy to install, fully expandable and complies to EN50131-1.

Freewave uses a “unique” encrypted code, ensuring high immunity against interference from external sources such as mobile phones, TV and other radio signals. In addition, a floating code, anti-scan, anti-jamming and anti-collision features provide reliable transmission between the detection devices and the control panel.

The system can accept up to eight wirefree keypads and, with its standard 16 zones, up to 32 detectors of varying types.

The highly rated 115dB(A) p.42 internal sounder is supported in the event of an alarm by the wirefree external sounder.

A GSM version is also available, which offers all the above features as well as the convenience of text messaging to eight mobiles, giving installation and event details and the ability to control the system and selected appliances by text.

Add-on devices include gas detectors, break glass detectors, smoke detectors, keyfob and doorbells.

Reader Service No 104

Less than two hours

Honeywell Security has launched Domonial, a completely wireless intruder system for residential applications. The Domonial is a flexible 20-zone control panel which is quick and easy to install – less than two hours. The only cable requirement is for mains power supply or PSTN.

Domonial has been designed with a built-in modem to enable remote diagnostics, programming and maintenance.

If alarm activation occurs, the Domonial transmits a signal to the ARC or monitoring station by PSTN, GSM or SMS. It is available with two keypad options – with or without LCD. It also operates with up to four keyfobs, as well as up to four wireless internal and external sirens or wireless relays. The system allows up to ten users.

Reader Service No 105

For sheltered housing

Cirrus Communication Systems has developed a dispersed alarm system that does not require a power cable. Smart Call is easy to install and relies on battery power, lasting for up to two years based on five minutes voice link usage per day.

The system benefits sheltered housing providers and tenants. Specifiers can avoid the usual intricate installation method and alleviate the need for a mains power and a telephone connection to be installed in the same location. The wireless system means there are no hazards from exposed cables, and tenants are free to move their furniture without restrictions.

Smart Call (below) is also compatible with a range of peripherals including smoke detectors and tabletop transmitters. It can also be connected with UK-based monitoring centres, and gives clarity of speech in simplex or duplex.

Reader Service No 106

Wireless and flexible

The PowerMax Plus from Visonic provides remote access to premises via the internet, telephone or mobile from wherever the homeowner may be. From logging on at work to see that the children are home from school, to switching on lights and setting central heating via SMS, the PowerMax Plus provides flexibility.

Reader Service No 107

No more cut phone lines

Bosch Security Systems provides secure remote alarm monitoring with the DS900i-GSM even when telephone lines go down. It has dual path transmission and dual band hardware and full compatibility with most alarm panels and alarm receiving centre systems.

The DS900i-GSM is an advanced digital solution which sends intruder or fire alarm messages via the mobile phone network, including text messages. The interface constantly monitors the installation telephone line and in the event of failure or a line being cut, automatically communicates an alarm to the central control point via GSM (the mobile phone network).

The device can also operate as a SMS communicator with six dedicated inputs and one remote output to send text message alerts to mobile phones.It is suitable for use in any domestic, industrial or commercial security application where the integrity of the telephone line is likely to be jeopardised.

It is also useful for remote sites or buildings under construction, where telephone lines are not installed. In these circumstances, the system can be used as a complete standalone wireless telephone system for all voice calls, with no need for land lines.Reader Service No 102

Hints and tips for installing wirefree systems

When installing a wirefree system, in addition to reading the instructions supplied for each piece of equipment, here are my top 10 tips for a successful installation.

1. Always check the signal strength and background noise levels from the proposed locations of all devices before you mount any device onto its intended location. If a signal strength measurement is not available, at least do a few tests to ensure that alarm signals are received at the control panel before you mount any devices.

2. Avoid mounting transmitting or receiving devices or aerials under metal lintels at the top of windows & doors.

3. Don’t mount transmitters or receivers onto metal or upvc clad metal door or window frames.

4. In systems where the receiver aerial is mounted vertically, the greatest radio range can usually be obtained by mounting all the transmitters so that their aerials are also vertical. In some systems the aerials are mounted in both orientations so this will not apply.

5. If you need to run wiring into any transmitter or receiver always try to keep this away from the aerial(s) as any metal object near an aerial will reduce its performance.

6. Don’t alter the length of the aerial or replace the aerial inside any transmitter or receiver with an aerial that is not approved by the system manufacturer. Aerials are designed to a tuned frequency and altering the physical length of the aerial will affect the operating frequency and performance of the aerial.

7. Avoid mounting the receiver or the receiver aerial near to electrical distribution equipment, televisions, or computer equipment as these can generate background noise. Avoid large metal objects such as water tanks, boilers and radiators etc. Large metal objects can prevent radio signals from passing between the transmitter and the control panel.

8. If you install a remote aerial on a system, ensure it is mounted in the correct orientation. Don’t cut the aerial cable until you have checked the signal strength. Always look at the direction in which the cable leaves the aerial and keep running the cable in the same direction and away from the aerial for as far as practically possible. Never clip the aerial cable or any other cable close to the aerial or the aerial cable. Try not to run your aerial cable next to mains cables, but running the aerial cable with the bell wire will not usually cause a problem.

9. Sometimes in properties with very thick walls, adequate signal strength cannot be obtained through them. If the receiver or the receiver aerial can be mounted high up in a loft space so the signal path is through the floor boards, this can increase the signal strength to an adequate level, particularly where the devices are mounted on outside walls.

10. Look for the ideal position for the detection device. A passive will not necessarily need to go at ceiling level or on an internal wall, as hiding a cable is not a consideration.

Source

Security Installer