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WITNESS CCD OBSERVATION SYSTEM
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WHAT OUR EXPERTS SAY...
The success of products such as Philips Pro-Vision
and Mitsubishi Mel-Guard over the past five years has clearly demonstrated
there is a steady demand for easily installed, off-the-peg multi-camera video observation
systems. This niche has been created by small businesses and residential users,
who do not require heavily featured systems, that may be technically over-qualified
and economically unviable for this kind of application.
The Witness CCD Observation System from
Electronics Line, has clearly been designed to meet the needs of this increasingly
important sector. The basic package comprises a 12-inch monochrome monitor with
built-in camera switcher; it comes supplied with a single monochrome line-powered
camera plus mounting bracket and 20 metres of pre-wired connecting cable. In
addition to power and video signals, the cable also carries two-way audio
between the monitor and the camera module, plus alarm information from optional
PIR sensors.
The switcher can accommodate up to four
cameras, they connect to the monitor via a bank of modular phone-jack sockets,
on the rear of the case. Two similar sockets are fitted to the back of each
camera; one connects the camera to the monitor, the other is for an associated alarm
sensor. In addition to extra cameras and sensors the monitor’s video output can
also be connected to a VCR for recording and playback. Although not featured on
our sample we understand all new models are now fitted with a slave monitor
output. Other options include a weatherproof housing for the cameras, and
extension leads, that can increase cable runs up to 100 metres.
CUBIC CAPACITY
The cube-shaped cream-coloured monitor measures
304 x 282 x 308mm. Most of the controls are grouped together on the front
panel. There’s a line of seven buttons and LED indicators, for manual camera
selection, engaging auto-sequence, selecting VCR input and press-to-talk for
two-way audio contact with a camera. Next to that there’s four preset controls
for adjusting brightness, contrast and volume, and setting the camera dwell time, which can be from 1 to 30 seconds.
There’s a small loudspeaker behind a grille on the left side of the fascia, the
microphone is mounted just below the main on/off switch.
Around the back there’s a row of five modular
jack sockets, one for each camera, the fifth carries VCR input and output, a
suitable modular jack-to-phono/RCA adaptor lead is supplied. Additionally there
are two recessed presets, for adjusting vertical and horizontal hold. Unfortunately the holes on the back
panel on our sample didn’t quite line up, making it difficult to carry out any
adjustments.
The monitor is fairly well built with a sturdy
metal chassis and cover, that should be able to withstand a fair amount of
punishment. The general standard of construction is quite good, though some
aspects of the internal layout could be better, including the position of the
mains transformer, which is very close to the side of the case. In fact it’s
close enough for the transformer’s shielding to come into contact with the metal
outer cover. The modular jack sockets do not appear to be very strong, the
camera cables are quite heavy and look as though they could put the sockets --
and their soldered joints -- under quite a lot of strain; care needs to be
taken to ensure the cables are not pulled.
CAMERA CHOICE
Two styles of monochrome camera are
available. The standard issue item is a neat flat-pack design containing a
board camera module and a second PCB for the audio and alarm functions. The camera also houses a tiny 1.7-inch
loudspeaker and electret microphone, it’s quite crowded inside the box which
measures just 62 x 75 x 35mm. The board camera is fitted with a fixed 4.3mm wide-angle
lens; behind that there’s a 1/3-inch
CCD image sensor with 315k pixel array, giving a low-light sensitivity of around
0.4 lux (f1.8); stated resolution is in the order of 400 lines. The exposure system
is fully automatic, a high-speed shutter varies between 1/50th and 1/100,000th
second.
The second
type of camera has a similar general specification but is a more
conventional shape, and can be fitted with a C-mount lens. Cameras are supplied
with a universal mounting brackets that can be fixed to a wall or ceiling. Any
type of alarm sensor with an N/O contact can be connected to the second modular
jack socket on the back of the cameras, Electronics Line can supply a suitable
pre-wired PIR and adaptor cables for other devices. When the sensor is triggered
the camera switcher is automatically overridden and an internal siren sounds in
the monitor.
OPERATION
Alignment is very straightforward, there are
no external user adjustments for the cameras; the only preliminaries on the
monitor are to set the picture controls, volume and camera dwell time. As soon
as the system is turned on the switcher is engaged and continues to operate until
a camera selector button is depressed. The alarm system is activated by pressing
a button on the back of the monitor -- not a very convenient location -- if a connected alarm sensor is triggered the
switcher stops and displays the relevant camera output. The alarm siren will
also sound, this is cancelled by pressing the auto-sequence button on the front
of the monitor.
Sounds picked up by the microphone on each
camera are heard at the same time as the image is displayed; pressing the push
to talk button allows the operator to be heard through the camera’s on-board
loudspeaker.
At this point it’s worth pointing out a
couple of the system’s shortcomings. The most significant one being the lack of
a switched alarm output, which would have enabled the system to be integrated
with other security devices. This would have added very little to the cost, yet
increased it functionality dramatically. The other feature we would have liked
to have seen, would be a means of switching off the monitor screen, so that the
switcher and cameras could continue to operate, whilst connected to a VCR.
IN USE
The cameras are unsynchronised, nevertheless,
when the switcher changes from one camera to the next there is only a very
slight jitter on the screen; this lasts for no more than one field. The picture
is sharp and clean, contrast is good, and there’s plenty of detail. Picture
alignment is fine and there is very little noise.
The images from the cameras are crisp and
well defined, resolution on our test samples didn’t quite manage the 400-lines
resolution figure quoted by the manufacturer, though they weren’t far short, at
around 380-lines. Low-light sensitivity was within spec and although noise
levels were quite elevated under those conditions, the image was still useable.
At higher illumination levels noise is negligible. The fixed lens provides a
wide angle of view, though there is a fair amount of barrelling at the edges.
The camera’s on-board microphone is very
sensitive and can pick up a conversation -- in quiet surroundings -- at a
distance of several metres. Needless to say the tiny loudspeaker built into the
camera isn’t very loud, it’s just about okay if there’s no background noise but
if the camera is mounted more than a half or metre or so away from the subject,
it’s a struggle to hear it. If the camera is fitted in the optional
weatherproof housing the audio becomes even more muffled. Incidentally, the
transparent window at the front of the housing can produce internal reflections
when there’s a strong light source to the side of the camera.
OVERALL ASSESSMENT
The lack of a standby facility, so the system
can continue to function with the monitor switched off, and an external alarm
output, impose some limitations on flexibility. We suspect quality control could
be better, and whoever decided to put the alarm enable switch on the back of
the monitor needs their heads examining. Against that should be weighed the quite
impressive performance -- comparable with similarly specified systems -- plus
the lower than average cost of the basic system and add-on components. That firmly
swings the balance in the Witness system’s favour and it deserves to do well.
PRODUCT ASSESSMENT
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 ****
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Ó R.Maybury 1996 2403
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