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Despite being billed as ‘the toughest surveillance camera in the world’, the Canadian-built Silent Witness arrives cocooned in some of the thickest packaging we’ve ever seen... It’s all very well claiming to be tough, but can they back it up? They can, Silent Witness have a string of independently certified test results, relating to their camera’s performance at extremes of temperature and humidity, weatherproofing and ability to withstand vibration and shock.


The key to this highly unusual camera’s durability is its rugged two-piece die-cast zinc housing, the first we’ve come across on a video system of this type and size. This is effectively an all-weather camera that can be installed inside or out, usually without the need for any additional protection. It will operate in temperatures from -25 to +60 degrees centigrade and is impervious to dust, rain or salt spray. The two halves of the case are sealed by a rubber gasket, all other entry points are waterproofed or heavily coated with silicon mastic. Inside the electronics in one of the two models are further protected by thick neoprene foam padding around the interior surfaces, there’s even a small pouch of silica gel dessicant, to absorb any moisture that may somehow find its way inside.


The metal case is grounded and will also provide the circuitry with a degree of protection against electromagnetic radiation and electrical spikes. The exterior of the case is finished in a hard-wearing cream-coloured Lexan coating. Despite the fact the camera will function in harsh environments, it is surprisingly compact, measuring just 63 x 69 x 114 mm, moreover the attractive cosmetics blend in easily with almost any type of surroundings, be they industrial, commercial or residential. 


Silent witness is available in two basic configurations, based around colour or black and white CCD board camera modules. They can be fitted with a range of off-the-shelf lenses, from a 2.5 mm wide-angle to a 16 mm long-range; custom-designed optics are also available. The cameras are fitted with a microphone, a red ‘tally’ light flashes when the camera is powered. Silent Witness can also supply dummy cameras, also fitted with a flashing LED, that are indistinguishable from the real thing.


Power and signal connections are made via a small plug-in module -- also weather proofed -- that doubles up as a mounting head. It’s held in place by a single tamper-resistant bolt. This allows cameras to be fitted, removed or exchanged quickly -- less than a minute the manufacturers claim -- using the specially designed hex key supplied with the outfit. Power requirements are fairly modest, they need a 12 volt DC supply rated at 250 mA or 150 mA (colour or monochrome respectively) and can be locally powered by a simple plug-in mains adaptor. Silent Witness supply a range of mounting hardware -- the outfit contains a simple U-bracket --  a sturdy universal three-axis mount is available as an option. Both types of bracket attach to the connector head, using security bolts.  A single 6-foot shielded cable emerges from the head, this terminates in three connectors, a male BNC carrying the video output, a male RCA/phono plug for the audio, and a female 2.1 mm power socket.  Connector heads with 20 and 50-foot cables are available.


The specification and construction of the two camera modules differs slightly, though both are based around one-third inch CCD image sensor chips. The black and white camera is a single board device with a quoted low-light sensitivity of 0.5 lux and horizontal resolution of 380 lines. The image sensor on the colour camera is located on a separate board, with the video processing electronics on a second PCB beneath the sensor. Low light sensitivity in this case is rated at 5 lux, and resolution is 350 lines. Both types of camera are connected to a power supply and interface board bolted to the inside of the back panel, which also carries the connections for the LED indicator and microphone.


Installation and alignment are very straightforward. There are no external controls, or indeed any user or installer adjustments to be made prior to switching on. Both cameras have fully automatic exposure systems that can cope with a wide range of lighting conditions.



Resolution on our sample monochrome camera was very close to the stated 380-lines; the low-light sensitivity figure appeared slightly ambitious, though it will certainly produce a useable image in light levels below 1 lux. The low-light figure for the colour camera was about right, though in practice the scene needs to be quite well lit, otherwise contrast levels are low and colours look muddy. This time the resolution was only a few lines short of the quoted figure. The exposure system on the colour camera is noticeably more responsive and better able to deal with fairly large variations in lighting levels or bright lights in the scene area. Colour accuracy in natural light is good, though there is a slight yellow caste under fluorescent or tube lighting, that the white balance system appears unable to neutralise.


The exposure system on the black and white camera has a narrower range of response, it tends to favour low scene illuminations and it is not so good at  compensating for bright lights or strongly back-lit subjects. The transparent window in front of the lens on both cameras produces internal reflections from bright lights in and around the scene area -- not necessarily in the picture -- some of which can become quite severe, and there is the characteristic vertical smearing produced by the CCD from bright spots of light, so some care has to be taken over alignment. 


We couldn’t pass up the opportunity to put at least some of the manufacturers environmental performance claims to the test. We subjected both cameras to a series of trials, designed to simulate conditions the manufacturers say they can endure. The first one was a simple shock test. The picture on the colour camera jarred slightly but otherwise remained stable and locked when it was tapped lightly with a rubber-tipped mallet. The black and white camera responded to the same treatment with a momentary flash and loss of picture. It seemed to be most sensitive around the connector head, suggesting a slight intermittency in or around the plug and socket contacts. The connection was re-checked and tightened but it remained touchy.


Test number two involved putting both cameras inside a shower and spraying them with hot and cold water from different angles for half an hour. During this time the video and audio output was closely monitored. A small amount of condensation built up on the inside of the transparent cover on the colour camera but it dissipated within a few minutes. The colour balance also changed very slightly with a small increase in the red levels, when the camera was doused with hot water, but in general both cameras continued to function satisfactorily. The audio output became muffled as droplets of water collected around the microphone opening but normal operation resumed once they were dried off. After the test the cameras were opened up, and we’re pleased to report they were both completely dry inside.


The third test subjected the cameras to a range of extreme temperatures consisting of an hour in a freezer at minus 18 degrees centigrade, and ten minutes in an oven heated to plus 50 degrees centigrade. Whilst the cameras were powered up they continued to operate without any problems or significant change in performance characteristics, though once again the response of the colour camera changed slightly during the time it was heated. Neither camera worked from cold, taking about five minutes to warm up,  before the picture appeared.



Aside from the slight intermittence with the black and white camera, which was almost certainly due to a minor contact problem on the connector head, the cameras performed very well. They have been designed to cope with the extremes of the Canadian climate so our tests were relatively gentle by comparison with some of the possible conditions -- particularly their Arctic Winters  -- even so our very encouraging results suggest that at the very least they should be capable of withstanding the worst that the British weather has to throw at them.


The only significant compromises concerns the range of lenses available to fit these cameras and their rather limited exposure systems. Otherwise the highly original concept and quality of design and construction are very impressive. Silent Witness cameras can operate effectively in a uniquely wide range of conditions and environments, that previously would have demanded specialist cameras suited to each individual task. Surprisingly this level of versatility is not reflected in the price, which compares quite favourably with conventional general purpose monochrome and colour cameras.



Design and design features              9

Circuitry and components                  9

Ease of installation and wiring    9    

Range and variety of functions            7     

Accompanying instructions                   7          

Technical advice and backup            9     

Value for money                         8                            




Ó R.Maybury 1995 1512











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