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Don't throw away your wire cutters and cable crimpers just yet, but their days are numbered… If nothing else the AV Share system from Haydon Marketing gives us a glimpse into the not too distant future of CCTV, when the chore of connecting cameras to monitoring equipment by costly and inefficient cables will no longer be necessary.


AV Share is a modular wireless camera system operating on the 2.4GHz band. The UK Radiocommunications Agency has recently opened the band in line with EU directives to allow the use of low power, licence exempt video transmission and wireless computer networking systems. The interim specification (I-ETS 300 400), allows for a maximum output power of 10 milliwatts, making it suitable for short-range (up to around 100 metres) video (and audio) links with a maximum bandwidth of 20MHz.


The manufacturers of the AV Share system have split the bandwidth allocation into four separate channels which reduces the chance of interference from other nearby systems, or allows up to four cameras to operate simultaneously, more about that in a moment. Interference is actually less of an issue than might be expected, since transmission power levels are very low and systems like AV Share use directional antennas. Additionally, in the early days at least, the chances of 2.4GHz systems operating in close proximity to one another will be remote.


Various configurations are available, including combined camera/transmitter modules (colour and black and white) and stand-alone transmitter units that can be used with a standard CCTV camera. The system we've been looking at is the AVCAM2 package, which comprises one colour camera/transmitter, 4-channel receiver, mains power supply modules and camera mounting hardware kit, this is currently selling for around £259.00.


The camera is only a little larger than a typical CCTV video camera, it's housed in a black ABS plastic case with the image sensor and lens at one end, and three sockets for audio and video output (for a local monitor), and DC power in, at the other end. On the top of the unit there is a fold-up antenna plate, this can tilt through 180 degrees, and swivel through 360 degrees, so it can be directed at the receiver. On the underside is a standard 1/4-inch UNC mounting threat, which attaches to a simple universal mounting bracket. The camera is based around a board camera module using a 1/3-inch inch CCD (500 x 582 pixels) with an integral fixed wide-angle lens (F2.0, 4.0mm) giving a 78-degree field of view. Low light sensitivity is in the region of 4-lux and off-camera resolution is quoted at 350-lines. Exposure is fully automatic with an electronic shutter range of 1/50th to 1/100,000th sec. For the record the monochrome camera has a similar specification to the colour model but low light sensitivity is down to 1 lux. The monochrome camera also has a set of six built-in IR illuminators (three either side of the lens) which will light up subjects up to a metre or two in front of the lens in 0-lux conditions. There are only two controls, an on/off switch and a 4-way channel selector switch, both on the left side of the case. A red power-on LED is mounted just above the lens and next to that is a small hole for the microphone.


There's not a lot to see inside the camera, up front is the board camera module, in the base if the unit is a motherboard with control and power regulation circuitry, all of the RF processing is handled by a small screened module. Build quality is good and the only point to watch is that the case has no weatherproofing so it cannot be used outside or in a hostile environment without some from of protection.


The receiver module bears more than a passing resemblance to a number of recently launched domestic 'video senders' designed to allow the AV outputs from satellite receivers and VCRs to be viewed (and controlled) from a TV in the bedroom. Further clues to its domestic alter-ego can be seen in the now redundant IR remote control receptor window on the front and blanked off sockets on the back panel for right and left stereo audio outputs. Rear panel sockets consist of two phono connectors for mono line-level audio and composite video, DC input and a modulated RF output, for connection to a TVs aerial socket. Once again there are only two controls, an on/off slide switch on the side and a sequential channel selector button on the front. The channel in use is shown by a row of four LEDs. On the top there is a fold out plate antenna and like the one on the receiver it can be tilted and turned to get the best signal. Receiver build quality is to a similarly high standard and once again the use of dedicated modules for the RF circuitry should ensure a high degree of reliability and stability.     



Installation poses no problems whatsoever, the only considerations are location, range and antenna alignment. Since the receiver is self contained it should be a relatively simple matter to try the unit in a number of positions, to ensure the best picture (and sound) quality. There are no user or installer adjustments on the camera, aside from channel selection. The design of the power supply plug could have been better, as it is it projects almost 6 cm from the rear of the camera, which could cause problems if the camera is going to be mounted close to a wall. A shorter plug or a side-mounted socket would have been preferable. The top-mounted antenna could also prove a nuisance in some circumstances but in the scheme of things these are relatively minor considerations, compared with the usual problems of a traditional cable installation.


Multiple camera operation is possible either by using one receiver, which acts as a manual switcher, or using four receivers, one for each channel, though the facility to use four cameras simultaneously will depend to a large extent on budget and local conditions.



The monitor output socket on the back of the camera module makes it easy to make a direct comparison of picture quality before and after transmission. At very close range (4 to 5 metres) under ideal conditions the only difference is a very small increase in picture noise, resolution at a little over 300-lines remains much the same. Colour fidelity is very good indeed and colours look reasonably lifelike in a well-lit scene. As the range increase so too does the noise levels, this gives the picture a slightly grainy appearance and starts to impinge on the amount of detail in the image. Up to around 30 metres in the open, the increase noise levels are relatively insignificant, when there are solid objects in the way – walls or structures -- the noise does start to have a more noticeable impact on the picture, though again they are still acceptable. Towards the limits of the open-air range -- 80 to 100 metres -- the picture can start to look quite hairy and more care need to be taken with antenna alignment, the best 'indoor' range we achieved was just over 40 metres after which the image became increasingly unstable.


Operation is possible in a wide range of lighting conditions and the camera's auto exposure systems coped well with sudden changes and bright lights within the scene area though some from of backlight compensation would have been helpful for awkwardly lit scenes.  


The forward facing microphone is moderately sensitive and directional. It is possible to hear normal speech up to a distance of three or four metres in front of the camera when ambient noise levels are low.


Our sample performed well on all four channels though some bleed-over was evident on a couple of the channels but it was at a very low level and unlikely to cause problems since the antennas are quite directional.  



We have absolutely no doubt that one day all CCTV camera systems will be this way, and cables will eventually become a thing of the past. There is still a long way to go however, and several issues remain unresolved regarding the present 2.4GHz system. The most obvious one is the lack of security. The video and audio signals are unprocessed and not encoded or encrypted in any way so it would be possible for images to be picked up on another receiver in the immediate vicinity. The second problem concerns the number of channels. Four cameras are adequate for residential applications or small commercial premises but it falls some way short of what is needed for larger multi-camera installations. Thirdly, the potential for interference exists, admittedly the risk is very small at the moment but as more 2.4GHz products appear it could become a consideration. Finally, it hasn't happened yet, but there may be some health and safety implications over the use of the 2.4GHz band, which is close to that used in microwave ovens. Power levels are tiny but given the current concerns over high frequency radio emissions from cellular telephones the debate could well spill over into this area. Leaving that aside the AV Share system has much to commend it, it works very well indeed, it is easy to use and install realistically priced and within its obvious limits, a viable alternative to cabled systems.



Design and design features                      ****

Circuitry and components                ****

Ease of installation and wiring            ****

Range and variety of functions            ***

Accompanying instructions              ****                          

Technical advice and backup            ****     

Value for money                         ****                           



ã R. Maybury 1999 0705



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