The bench test 1: Resilient & timeless

   The TK-C720 has the same kind of resilient timeless feel to it and you get the impression that it too will still be going strong many years from now.

It is built to last, possibly to the point of being over-engineered when you consider that most general purpose surveillance cameras lead fairly sedate and physically undemanding lives. Nevertheless, being prepared for the worst, even if it never happens, is no bad thing.

JVC has given the C720 a fairly conservative specification; it is based around a high performance 1/3-inch interline CCD image sensor (752 x 582 pixels, 440k effective) with a claimed resolution of 470 lines and a low light sensitivity of 1.5 lux. Exposure facilities include switchable backlight compensation and AGC plus auto/manual white balance.

It can be used with DC or video controlled auto-iris lenses and it is powered from an external 12-volt DC or 24-volt AC supply. The unusual feature is a balanced twisted-pair video output, which is in addition to a normal composite video output. (This put the camera onto the IFSEC Product of the Year shortlist - Ed)

Stylistically it doesn't stray too far from the traditional tried-and-tested beige rectangular box format. At the front is a standard C/CS lens mounting thread, this is attached to a simple back-focus adjustment that's set by moving a large thumbwheel, accessible through a slot on the top of the case. There is a locking screw on the left side of the camera body; on the right side panel there is a four-pin socket for an auto-iris lens, a switch for selecting video or DC control and a recessed level adjustment.

  On the left side of the back panel there is a set of screw terminals for the power supply connections and the twisted pair video output. A six-way miniature DIP-switch in the centre of the panel handles the AGC, backlight, auto shutter, white balance and internal/external line-lock synchronisation. Below it is a set of three push buttons for setting line-lock phase, manual white balance and resetting the camera to its factory defaults. Instead of the usual BNC connector JVC has used a phono/RCA socket for the composite video output and there's a green LED power-on indicator.

A mounting plate that should have a standard ¼-inch UNC thread can be attached to the top or bottom panels on the case. Unfortunately the metal threaded collar on our sample had either fallen out or never been fitted, which realistically is not a big problem but very uncharacteristic of JVC's normally scrupulous quality control.

The case comprises two steel halves with a cast alloy front panel and steel back panel; there has been no attempt at weatherproofing and dust and moisture can easily find its way inside the case so some consideration will need to be given to its protection if it is going to be used in a hostile environment.

Over the years we have become accustomed to the insides of surveillance cameras being mostly filled with empty space so the C720 came as something of a surprise. It's tightly packed with densely-populated circuit boards which belies the modest feature list and lack of controls, but the quality of construction is beyond reproach and the heavyweight chassis and casework should make it virtually indestructible.

Setup & operation
Aside from the dodgy mounting plate, installation is unlikely to pose any problems and the initial setup, which at worst entails flipping a few switches and setting a couple of levels, should take no more than a few minutes. The only slightly fiddly adjustment is the back-focus, which proved to be highly sensitive and moving the thumbwheel a fraction of a degree either way would throw the setting off. The only other point to note is that it does get quite warm so care should be taken to ensure that it is mounted in a well ventilated location.

   Performance
Tested using both the twisted pair and composite video outputs, the camera's auto exposure system reacts reasonably quickly to rapid changes in lighting levels but it can be easily fooled by bright lights in the scene area even with the backlight compensation enabled. Resolution and low light sensitivity on our sample were both close to the manufacturer's specs and in poor light noise levels remain well below average, resulting in a crisp, clean image under all but the most adverse conditions. Colour accuracy with the white balance system in auto-trace mode is also very good, even under artificial light and while there is a slight greenish-yellow caste in tube light, it's at a much lower level than most comparable cameras.

The solidity of the construction showed through during our intermittency tests and the picture never missed a beat when the camera received the customary beating from the Bench Test rubber mallet.

What the manufacturer says ...
JVC's first twisted pair camera, model TK-C720TPE, boasts a 1/3-inch high resolution CCD with special built-in output for connecting to a twisted pair cable, where video images are able to be transmitted over distances of 900m +.

The camera delivers excellent picture quality, due to 470 lines of horizontal resolution and 1.5 lux sensitivity.

The added feature is an inbuilt transmission facility. Conventionally the transmitter is an add-on to the rear of the cameras, increasing the housing space.

This makes the TK-C720TPE a neat and compact unit.

As a result of recent improvements in technology and reduction in market prices, increasingly more CCTV dealers and installers are specifying twisted pair for the entire cabling systems.

The use of balanced video over UTP cable is less susceptible to environmental, electrical interference and earth potential problems, therefore the image quality is maintained over short or long distances.

It is also cost-effective to switch to UTP as it is possible to pass more than one signal down a multi-core UTP cable, thus saving precious storage space and reducing strain on a building's cable infrastructure and ducting.