AV SHARECAM WIRELESS COLOUR CAMERA SYSTEM
WHAT OUR EXPERTS SAY...
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