What our experts say…
From James Bond to Mission Impossible, the enduring image of secret agents and bank robbers donning their special goggles to avoid triggering an active infrared beam has been with us for some time. Where would the caper film director be without the imagery of that thin red beam of light?
It must be true to say that no alarm device has quite as effectively captured the public imagination as the active infrared beam. So strong is our collective perception of the laser type thin red lines that beam manufacturers even feature the image in their promotional literature. It would be churlish to reveal that the form of electromagnetic output is not so focused and more correctly resembles a conical shape – and stating the obvious to mention the beam cannot be revealed by blowing smoke across the line of sight. However, the concept of a red laser beam (they are always red) suits us well and looks set to continue.
The RV Micro-beam comprises an internally rated active infrared transmitter and receiver using two parallel beams – commonly known as a twin format – designed for short range use in a domestic or light commercial environment. They are made and supplied directly by Radiovisor in Mitcham, Surrey, and are available for around GB pound 35 + VAT. The equipment carries the CE mark and includes a two-year warranty.
Each of the transmitter and receiver PC boards are enclosed within identical two-piece mild steel white powder coated boxes. The design is dull but inoffensive, and the small size and white finish means the system would not look too out of place in a domestic environment, which we believe is the intended market for the Micro-beams. The enclosures are not IP-rated but are clearly intended for internal use only.
No internal rotation of the infrared LEDs is possible, so the units must be located more or less exactly opposite each other for the beams to correctly align. Although RV calls the pair a ‘biaxial twin beam’, the distance between each LED of the beam pair is only 25mm, so it would in fact take only a relatively small object to interrupt the line of sight of both beams and create an alarm condition. Installers will need to ensure therefore, that the equipment is intelligently sited in order to prevent false alarms due to local movement.
The transmitter output operates at a wavelength of 880nm, and the IR transmission power is user selectable to tweak the output to match the environment and distance required.
The receiver provides a useful NO/NC changeover relay output, together with an on-board AT microswitch to give warning when the enclosure cover is removed. No anti-tamper protection is provided for the transmitter.
Both the receiver and the transmitter will operate between 10.5v and 15v DC. The units only need to be powered from the same PSU if more than one overlapping pair of beams are in use. RV have catered for this eventuality by providing a ‘synchro link’ facility which allows up to six sets of beams to be installed in close proximity with each receiver only responding to infrared modulation from its own transmitter.
Set-up procedure
Since the Micro-beam has no in-built vertical or horizontal alignment mechanism, setting up the equipment merely requires the installer to mount each head looking face-to-face with the other. It is then prudent to perform a quick test to ensure that each LED beam will hold off the output relay even if the other is blocked.
Easy stuff, but only made simple because the maximum range is relatively short, and each unit is mounted at the same height. Installers should avoid the temptation of mounting the units at different heights – to incline each unit to the correct angle, though possible, would be very difficult to achieve in practice without an audible or visual guide of some kind.
Performance
The unit was found to work very well within the design parameters. The recommended maximum range of 20m was easily achieved when used internally.
In fact a greater distance is achievable in situations where there are hard reflective surfaces running adjacent and parallel to the infrared beam. This is because the infrared energy is ‘bounced’ alongside the direction of travel creating a gun barrel effect, focusing the energy into the receiver.
For this reason, careful use needs to be made of the transmitter output level, in order to limit the beam strength needed to hold off the receiver, and prevent the infrared energy bouncing alongside the line of sight.
The current consumption was found to be slightly less than specified by the manufacturer, at 24mA on standby, dropping to around 12mA during an alarm condition.
Technical literature & backup
The RV Ltd technical support number is provided with the literature – the technician was informative and helpful and very willing to talk about other RV products. He offered to email Micro-beam data in addition to our telephone conversation and was an impressive ambassador for the company.
The installation instructions are contained on both sides of a single sheet of A4, showing wiring diagrams for beam stacking and a separate diagram for the ‘RX inhibit link’ set up, to avoid frequency cross-talk between adjacent units. The installation instructions overall are quite adequate for setting up purposes.
What the manufacturer says…
The Micro-beam is both aesthetically pleasing and robust in design, making it the ideal choice for domestic or office environ-ments. The white finish provides a new look to the infrared beam that has in the past been stigmatised as the ‘black box’.
Its introduction provides a secure and reliable alternative to breakglass or vibration detection, when considering ‘first to alarm’ devices suitable for meeting the criteria set out in the ACPO Policy.
The discreet metal housing not only provides a level of resilience to damage, it also provides strong immunity to emissions from other electrical equipment that may be located in close proximity.
Fixed optics allow for easy alignment. Although the main feature of the ‘Biaxial’ sensing is to make the device unaffected by small insects, it additionally aids the alignment test facility, as does the beam status LED. With an internal range of 20 metres, the Micro-beam is equally at home with corridor and room detection, as it is with detection across windows or doors.
A transmitter power switch and fine-tuning pot cater for problems encountered with ‘bounced’ beam paths from windows, shiny floors and other reflective surfaces.
An integral link and connection provides transposed beam pair reflective immunity. This is generally associated when transposing a set of beams, only to establish that one of the transmitters IR energy is being reflected off the surface which its associated receiver is fixed to, and interfering with the receiver of the other set.
The sync link high security synchronisation facility provides a means of multiple stacking beam sets without cross interference, and additionally helps eliminate possible interference from other adjacent IR light sources.
An exceptionally high level of sun circuitry allows the unit to be used in close proximity to windows without the fear of interference from low level sunlight or other artificial light sources that may be directed into the receiver optics.
The Micro-beam is an exceptional little unit packed with an abundance of features aimed at providing zero false alarms.
