TECSEC Europe gives installers a boost
The difficulty of sending video information over long distances has proved to be an enduring challenge for the surveillance industry. As installations get bigger, with ever more cameras managed by fewer operators, the problem can only get worse. Over the years numerous ingenious solutions have been developed, some more successful than others.
But while a number of 'wireless' systems have proved to be highly effective under specific conditions, the vast majority of installations still rely on a cable linking the camera to the monitor or switching and control equipment.
In addition to being the simplest means of connecting two devices together, a cable has the advantage of being reasonably secure and largely immune to interference and the influence of surround buildings or local terrain. Cable is also comparatively cheap and if properly installed, requires little or no maintenance. Cable is also very reliable but when it does go wrong, it is (usually) easy to fault-find and repair.
Cable sounds like the answer to every installer's prayer – but there is a catch. Normally configured video signals do not travel well over distances of more than a few hundred metres. A video signal is a remarkably complex entity comprising a dense mixture of amplitude and frequency modulated waveforms that are adversely affected, to a greater or lesser extent, by the electrical characteristics of the cable they are passing through.
Moreover on really long cable runs, as the signal becomes weaker the effects of noise also become more problematic.
There are various ways around these problems. The two commonest approaches are to 'boost' or amplify the video signal before it starts its journey, or the weakened signal can be processed at the monitor end, to compensate for the changes that occur on a long cable runs, and boost the signal back to its original or optimum level.
That brings us to the subject of this Bench Test, two products from TECSEC Europe which one way or another make it possible to send video signals over long cable runs, emerging at the other end in more or less pristine condition.
The devices in question are the VCE2 video cable equalisation amplifier and VLA2 video launch amplifier, which can be used either separately or in combination with one another.
The VCE2 equalisation amplifier is normally located close to the monitor or control/switching devices, though it can also be used as a repeater, at a point in a cable run determined to be in need of equalisation.
It is available in a range of configurations. The sample we have been looking is housed in a rack-mounting case, which can be fitted in banks of three in a standard 2U frame.
The key features include frequency compensation on 75 Ohm balanced or 110 – 150 Ohm unbalanced (coaxial or twisted pair) cable runs up to 6km, variable video gain (-1 to +10dB). It has a built-in video loss detector with front panel indication and alarm contact. A low band filter and optical isolation of the input and output signal paths provides a high degree of immunity to noise, hum and earth current rejection, and the input and output connections have lightning and over-voltage protection.
Bandwidth can be tailored to suit a variety of applications; a 5.5MHz narrow band setup is recommended for installations with extra long cable runs or where noise is likely to be a problem. The standard 8MHz option is designed for the majority of colour and monochrome cameras.
There is a 10MHz wide-band system for use with higher definition and S-Video equipment. Models with additional interference immunity, from local or nearby transmitters, are also available. The unit has a built-in mains power supply.
Rear panel connection on the VCE2 consist of a three-pin IEC mains socket, two BNC sockets for coaxial video in/out and two spring terminals, for the balanced twisted pair video input and output. Alarm connections are handled by a five-pin DIN socket. A small rocker switch is provided for power on/off. On the front panel there are three LED indicators showing power status (mains and low power circuits) and the third one shows video input, flashing when the input is removed or interrupted.
Build quality is truly impressive, reminiscent of the proverbial brick outhouse and clearly designed for use in earthquake zones or to survive a nuclear war ...
The standard of construction is also very impres-sive; three PCBs are firmly bolted to the sturdy steel chassis. It is a little unusual to see what amounts to a mini wiring loom inside any electronic product these days, but it is all very neat and tidy.
The VLA2 launch amplifier is designed to be mounted next to or close to a camera, providing the signal with an additional boost to improve its prospects while travelling along balanced or unbalanced runs of up to 400m. Improvements in signal quality may also be possible – depending on cable type – in cable runs as short as 200m.
The module we have been looking at is housed in a two-tone white and grey 'Verobox' type enclosure, powered from an external 12v DC source and coming supplied with a mains adaptor.
Video connections on the VLA2 are also in the form of two BNC sockets, and one set of screw terminals for a balanced twisted pair output. On the opposite end there are two DC connectors, for power in and out, and a power-on LED indicator.
Inside the box there is a single PCB and once again it has a slightly old-fashioned feel to it with lots of full-size discrete components, rather than the usual forest of chips and microscopic surface mount components. Build quality is generally satisfactory, though some rather sloppy hand soldering around the video input connections on one of our sample units came close to preventing the use of some setup link pins on the PCB.
Setup & operation
The instructions leaflets for both units are on the brief side and could do with more detailed illustrations, but all salient points are covered. Installation and setup are reasonably simple, a pair of shorting links determines whether the video input is balanced or unbalanced and a second shorting link sets normal (1v) or high (3v) video output.
Preset controls on the main PCB, which the instructions warn can only be correctly set with the use of a signal generator and oscilloscope, are provided for setting input balance, input impedance (when using a balanced/twisted pair video connection), video level, low, mid and high-frequency lift.
Setup and adjustments in the VLA2 launch amplifier follow a similar theme with links for setting coaxial or twisted pair output, video level (-1 to +10dB), high-frequency lift and output balance, the latter being factory set and that is the way it should remain unless the output transistors are replaced.
The installation of the VCE2 follows normal conventions and should pose no problems. The VLA2 on the other hand has a slightly unfinished feel to it. At the very least it needs some form of mounting bracket or fixing hardware. Moreover it does not look terribly well protected against the ingress of dirt and moisture and this particular version is really only suitable for indoor installations.
Performance
Unfortunately due to various constraints we were unable to conduct any serious field tests or check the Equalisation Amplifier up to its theoretical 6km limit. But there were more than enough cable reels under the test bench to give both devices a fairly decent workout. The results were impressive.
A simple A/B test, looking at direct and atten-uated video signals, with and without assistance from the VLA2 through a simulated cable run of well over 300m, was very encouraging. Unamplified signals through the cable showed significant levels of noise and a marked reduction in colour depth but as soon as the launch amplifier was put into the circuit, the image returned to within a whisker of its original condition.
Similarly, feeding an unassisted signal through the VCE2 after it had passed through our test cable, brought about an immediate and very obvious improvement in picture clarity and a worthwhile reduction in colour noise.
What the manufacturer says …
The object of using special transmission amplifiers is to be able to produce a video frequency response which is a mirror image of the cable loss. The net result is that the video output will be a faithful reproduction of the input and effectively the cable loss disappears completely.
Designed and manufactured by TECSEC Europe Ltd, the VCE2 cable equalising amplifier provides frequency compensation for video signals after transmission over very long lengths of either twisted pair or co-axial cable. Up to three units used in conjunction with a VLA2 launch amplifier can can produce a useable video signal over a cable length of up to 6km (depending on the cable).
An opto-coupled stage is included within the VCE2, which will move any earth current and offer a high degree of hum rejection. The input stage is protected against over voltage and both input and output stages have lightning protection. Video loss detection is built in to all models, excluding the weather-proofed version.
The VLA2 video launch amplifier, also designed and manufactured in the UK by TECSEC Europe Ltd, provides high frequency pre-emphasis of the video signal for use on long unbalanced or balanced video transmission cables. With a total power consumption of less than 1VA, over voltage protection on the video input and lightning protection on the output, the unit can produce 3v terminated in 110 to 150 Ohm twisted pair cable.
A higher output version of the VLA2 is available to special order. This will provide over 6v of video in 75 Ohm unbalanced cable. This unit is intended for use only with cables which suffer from excessive noise or interference.
All TECSEC units benefit from simple and compact design, ease of installation and configuration, are backed by 12 months warranty, full technical support and a range of test equipment designed to aid correct installation. Available in a number of formats including 19 inch 2U rack mount, freestanding or fully weatherproof.
Overall assessment
Our checks indicate that these two units have the potential to enable video signals to travel over significant distances with minimal loss of quality or integrity. Overall build quality is very good, especially on the equalisation amplifier, which looks virtually bullet-proof. The launch amplifier on the other hand has a few rough edges and the lack of a mounting bracket or any guidance in the instructions might lead installers to suppose it can be safely left laying around, which would be inadvisable.Source
Security Installer
No comments yet