| Cameras and Camera Kits |
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Understanding Digital Signal Processing (DSP) |
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DSP is a term becoming frequently used in the CCTV industry. DSP cameras contain chips or chip sets which replace several conventional integrated circuits in the camera head. These DSP chips enable advanced video processing and manipulation to be carried out in the camera head.
DSP technology provides several benefits in either enhancing camera performance, or it can also be used by the manufacturer to simplify assembly and set up time thereby reducing costs.
DSP cameras can be divided into two categories:
- Intelligent DSP Cameras -
These cameras provide intelligent features combined with enhanced performance.
Intelligent DSP Cameras typically would have one or several of the following features:
- Programmable intelligent backlight compensation (BLC)
- Video Motion Detection (VMD)
- Remote set-up/control via a serial data link
- Built-in character generator
- On-screen menu
- Standard DSP Cameras
These entry level DSP cameras do not provide any of the intelligent features associated with DSP technology, but are designed to provide cost effective products. When choosing a DSP camera we advise you to CHECK THE SPEC!! |
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Understanding Lux |
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The amount of light on site should always be taken into consideration when choosing the right cameras for your installation. Lux, the measurement of light levels, refers to the level of illumination in a given area. In well lit areas a medium performance camera will usually suffice.
However, on a site where lighting is below 1 lux a high performance camera will normally be required. Using a light meter will give you the lighting level, the following are the light levels recommended by the lighting industry.
INDOOR
- Warehouses 20 - 75 lux
- Emergency stairs 30 - 75 lux
- Corridors & stairs 75 - 200 lux
- Shops 75 - 300 lux
- Offices & reception areas 300 - 500 lux
- Banks & offices 200 - 1000 lux
- Assembly lines 300 - 1000 lux
OUTDOOR
- Full sunlight 10,000 - 1,000,000 lux
- Overcast day 100 - 10,000 lux
- Twilight 1- 10 lux
- Full moon 0.1 - 1 lux
- Overcast night 0.01 - 0.1 lux
- Star light, clear 0.001 - 0.01 lux
- Star light, overcast 0.0001 - 0.001 lux
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| Consumable items |
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Understanding Fibre Optics |
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There are two distinct types of fibre optic transmission systems, multi-mode and singlemode. This refers to the fibre used and way the light travels down the fibre, not to the number of signals that are being sent.
MULTI-MODE
Cost effective at distances up to 4KM. This uses cost effective LED transmitters and in general is restricted to one signal per fibre (not too much of a restriction as we can get up to 96 fibres in a single 18mm tube). As the transmitters are cost effective and there is no requirement for expensive electronics to combine many signals onto a single fibre, multi-mode is the ideal low cost answer to small fibre optics systems. The multi-mode transmission system is limited to distances of 4KM.
SINGLE-MODE
Wide bandwidth, offering distances in tens of kilometres.
This uses the more expensive Laser transmitters that have a very wide bandwidth, this allows many signals to be sent down a single fibre, simultaneously and in both directions. This necessitates the use of the more expensive transmitters and electronics, and is normally used in large and complicated sites. Single-mode transmissions can travel tens of kilometres.
The transmission system VIS is selling is of the multi-mode type as this is more suitable to large scale distribution.
FIBRE OPTIC CABLES
Multi-mode fibres have the larger diameters (50 to 100um) and are designed for a light source of about 850nm. Single-mode fibres have smaller diameters (8 to 10um) and are designed for a light source of about 1300nm. VIS are offering multi-mode equipment, in Europe you are likely to come across 2 sizes of multi-mode fibres, 50/125 and 62.5/125. All the equipment and connectors VIS sell will fit and work with both sizes of cable.
CONNECTORS AND INSTALLING
There have been many types of connector for FO cables over the years but the most popular connector is the ST type. In the past fitting these connections involved using epoxy resins, and ovens to cure the resins, this was followed by many ‘happy’ hours of polishing to ensure the perfect finish. With the latest developments all this is a thing of the past. Nowadays excellent terminations can be made with Crimp Type connectors, very similar to those used on co-axial cables.
Despite the ease of these modern connectors there will still be times when sheer numbers of connections will make it more cost effective to subcontract the termination of the site to specialists. VIS can also arrange this service for you if it is required.
SETTING UP
Fibre optic systems, unlike copper systems attenuate the signals equally irrespective of their frequencies. So rather than having several controls to balance the signal after transmission all that is required is simple amplification. This is carried out automatically by the Automatic Gain Control (AGC) in the receiver units, and this same circuit ensures that the signal level is adjusted throughout the life of the installation, making these units truly 'fit and forget'. |
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Selecting the correct cable |
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Typical dB loss/100m @ 5MHz
URM70 = 2.3 dB
RG59U = 2.2 dB
RG11 = 1.2 dB
CT125RBS = 1.1 dB
A 6 dB loss at 5MHz will give you acceptable results for a high resolution black and white or colour camera.
NOTE:
To prevent sheath decay all coaxial cables supplied by Vista are made from high specification copper and have ultra violet light protection.
CABLE RUNS
Coaxial distances of 250 metres for RG59 and URM70 and 500 metres for RG11, will give clear pictures. Acceptable pictures have been obtained on distances almost twice as far, but this cannot be guaranteed. If cable runs are too long, the signal will have to be amplified at either one or both ends. If the coax runs along any high voltage cables, the approximate current which the cable takes should be found out. Electromagnetic fields can cause induced interference or hum (wavy picture).
If high voltage cables are close by, the coax should be run another way if possible. If not, a longitudinal hum rejector unit may be needed. Other forms of electromagnetic interference can be greatly reduced by use of a launch amplifier at the camera end, twisted pair cable, and a video line corrector at the monitor end. |
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| Domes |
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Tinted domes, lighting and picture quality |
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Tinted domes normally cause 1 ‘F’ stop loss of light. You need to double the light required for a given picture quality and even with tinted domes under certain lighting conditions you can still detect the position of the camera. Under certain lighting conditions dome loss of picture quality due to the curvature in the viewing windows can cause internal reflections. |
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| Hardware and Accessories |
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Advice on Mountings |
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- Allow plenty of time for selection of mounts because they will often need to be specially manufactured. If this decision is left to the last minute, it will increase lead times.
- Mountings include:
- wall mount
- corner mount
- ceiling mount (how high is the ceiling?)
- dome
- tower/pole
- Infra-red lamps hang low, so 6" column spacer should be used to stop them fouling pan and tilt head brackets (if used).
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Auto Pan and Preset Tours |
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It is important to remember that Auto Pan is not designed for continual 24 hour usage as this places undue strain on the Pan gearing. We do not recommend that the Auto Pan mode is used for more than 12 hours each day as any failure of Pan gearing due to the head being left in permanent auto pan is not covered by manufacturers’ warranties. It is also worth considering using more cameras instead of Auto Pan as the increased reliability and lower cost of CCD cameras can make this a more viable option.
This is also applicable to pan and tilt heads fitted with presets. These are often left on a permanent ‘tour’ and this can lead to premature failure of the pan/tilt unit and again is not covered by manufacturers' warranty. Please telephone our technical department for further advice. |
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Choosing Infra-Red lamps |
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Infra red lamps are available in different powers and with either 715nM or 830nM filters. The choice of filter is dependant on a combination of factors:
- can the user accept that the light can be easily seen. 715nM lamps look like a red traffic light at night.
- range of illumination (high powered 715nM filters illuminate most).
- the camera used, if for example, you must use a low power, 830nM filter, then you will require a high sensitivity camera such as a Vista VPM8420 or Baxall CDSP9742.
- lenses with a large aperture (small 'F'stop) should be selected.
- lamps should be selected to match lens angles.
RANGE
Maximum illumination range is dependent on weather conditions, contrast of the scene and ambient light levels. For guidance, maximum distances obtained for spot lamps are:
- 500W = 150 - 200 metres
- 300W = 80 - 120 metres
- 50W = 15 - 30 metres
- 30W = 5 - 15 metres
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Choosing side or top mount pan/tilt/zoom |
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The pro’s and con’s:
TOP MOUNT
- Pro: Can fit two IR lamps on sidecheeks of Pan/Tilt. These act as a counter balance enabling you to use a lighter duty Pan/Tilt head.
- Pro: Compact size.
- Con: Cannot be inverted.
- Con: Restricted tilt often -45° to 0° dependant on housing fitted.
SIDE MOUNT
- Pro: Can be inverted.
- Pro: Often cheaper.
- Pro: Large tilt often ± 180°
- Con: Difficult to mount IR lamps, often required special brackets or drilling.
- Con: Generally larger size
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Installing Wipers |
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Care should always be taken when installing wipers to ensure that the camera does not view the blade. Simply switch them on and off a few times to find the ‘worst case’ park position before installing the camera. Washer units can pump a nominal head of up to 10 metres, although it is best to keep this to a minimum for reliable operation. You should never install the reservoir above the housing as this can lead to the entire contents being syphoned away. Remember that washer units will also require re-filling on a regular basis. |
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IP Ratings |
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IP rating is a system of rating the protection of equipment from dust and water. This system is governed by a number of European and British standards.
The first figure relates to the level of protection against solid objects, while the second relates to protection against liquids.
The usual ratings associated with housings are as follows:
IP55
- Protected against dust - limited ingress.
- Protection against low pressure jets of water from all directions
- limited ingress permitted.
IP65
- Protected against dust - no ingress.
- Protection against low pressure jets of water from all directions
- limited ingress permitted.
IP66
- Protected against dust - no ingress.
- Protection against high pressure jets of water from all directions
- limited ingress permitted.
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Selecting the correct housing |
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- Internal dimensions should be large enough for the camera lens combination, allowing plenty of room for wiring.
- If pan and tilt is required, the weight of the camera/lens, I/R (if used), hand wiper (if used) should be added together and evaluated. The following allowances should be made:
- 1Kg for wind resistance
- 1Kg for cable drag
- up to 3Kg for snow and ice (if applicable),
- plus a healthy safety margin of around 10%
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Washers and Wipers on fixed camera systems |
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Wipers are often specified on fixed camera installations which necessitates the inclusion of hardwire or telemetry control to switch the wipers on and off. This is not usually cost effective and often unnecessary unless the angle of the camera housing means that the view is often obscured by rain or is sited in a dirty location. Wipers are not normally essential to a fixed camera system and are best avoided. |
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| Lenses |
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Back Focus, Fixed-focal length |
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This is a simple setting, if it is needed at all. With the camera viewing a subject the same distance as the final image distance on site, set the focus ring to midway and adjust back focus for optimum clarity. |
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Back Focus, Zoom Lenses |
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Before adjusting, note how the focus ring on the zoom lens appears to have little or no effect when the lens is set to wide angle, and conversely it has a large effect when on telephoto. With the focus set to far (fully clockwise viewed from the front), aim the camera at a subject over 30 metres away, set to wide angle and adjust the back focus for optimum clarity. Now zoom into telephoto and focus on a nearby object, keep this object in view as you slowly zoom out and if all is set correctly it should stay in focus, or track, all the way out. If possible it is better to perform this adjustment in low light conditions or with a filter covering the front optic as this will ensure the iris is fully open giving the smallest depth of field and, therefore, the best results. |
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Calculating horizontal view angles |
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Approximate Horizontal Angle of View:
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Choosing the correct lens |
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Choosing the correct lens can be one of the most important decisions for your installation. Here are a few simple guidelines.
- It depends on camera position and the view required. The wider the field of view, the less detail will be available and vice versa.
- The easiest way to choose is to use a view finder, which, when held to the eye, will indicate the view to expect on the monitor.
- If a view finder is not available, a lens calculator, or lens calculator software, will make the job easier. The only other alternative is to resort to measuring angles, and comparing them to lens specification sheets.
AUTO IRIS or MANUAL IRIS
Manual iris lenses are usually chosen for use internally when the light level remains the same, thereby avoiding the need to adjust the iris to changing light levels. Cameras with electronic iris can adjust the picture in the camera to compensate for changing light levels.
It is preferable to use Auto Iris lenses for external applications where light levels can change considerably during a day as an auto iris lens automatically changes the iris to suit the light level.
Once you have chosen an auto iris lens - do you use video drive or direct drive?
Standard auto iris lenses are video driven which means the lens itself contains the amplifier to convert the video signal from the camera into the control for the iris motor. Direct drive lenses are cheaper as they only contain the motor drive for the iris, therefore the camera must contain the amplifier.
Most cameras listed on this web site may be used with either auto iris or direct drive lenses. |
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Common Lens types |
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Standard - typical horizontal angle 30 degrees A "normal" angle of view is similar to what we see with our own eyes and is approximately equivalent to the diagonal dimension of the CCD imager.
Wide angle - typical horizontal angle 64 degrees These are short focal length lenses which provide wide angle views.
Telephoto - typical horizontal 15 degrees and less These are long focal length lenses that provide high magnification. |
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Iris Definitions |
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AUTO IRIS, DIRECT DRIVE, GALVOMETRIC AND EI
Much confusion has been caused by the introduction of new lens and camera technologies to achieve the correct setting of the iris for a given light level. Manufacturers use the same terms for different systems. The following descriptions refer to what is used in this price list.
Auto Iris (AI) - A lens that takes a video signal reference from the camera. It uses this in an amplifier to derive a DC voltage to open or close the iris aperture. The video level control is part of the lens.
Direct Drive (DD) - A lens that takes a reference DC voltage from the camera to open or close the iris aperture. The video level control is part of the camera.
Electronic Iris (EI) - This is a camera that uses its electronic shutter to control how much of the light falling on the CCD sensor is used to produce a picture. Thereby emulating the iris control of the lens. Video level is normally factory preset.
Galvometric Drive is the method by which the small DC voltages produced by either AI or DD systems are converted into movement of the lens iris. It is a modern cost effective alternative to the servo drive method. It is used in both AI and DD lenses. |
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Mixing C and CS Cameras & Lenses |
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The difference between C and CS mount equipment is the distance between the flange of the lens (the part of the case that butts up against the camera) and the focal plane of the lens (where the CCD sensor must be positioned). This is known as the flange back distance. On C mount lenses this is 17.5mm and on CS mount lenses it is 12.5mm.
Therefore if you have a CS mount camera and a C mount lens you can add a 5mm spacer to obtain the correct focus. If, however, you have a C mount camera and a CS mount lens correct focus cannot be achieved.
Some C mount cameras do allow you to swap the whole mount from C to CS or vice versa. |
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Setting up Auto Iris and Zoom Lenses |
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Note it is best if all these adjustments are performed on a bench before installation.
PEAK/AVERAGE ADJUSTMENT
(P/A) fixed focal length lenses This control effects the degree to which the Auto Iris takes account of any bright areas in the picture, e.g. windows, street lamps, reflection of the sun, etc.
If set to peak these bright areas are taken more into account reducing the contrast of the surrounding area, but allow you to see more detail in the bright area. If set to average these bright areas are taken less into account tending to cause over brightness or flare of these areas but raising the contrast of the surrounding areas. Therefore for most CCTV applications this control should be set fully to average before attempting to set the level control.
(Often this control is left towards peak at installation as there are no peaks in the picture and the control seems to have no effect. However when conditions change and peaks are introduced the overall contrast is reduced and a site visit has to be made, so please ensure it is set fully to average unless it is the rare occasion you wish to see detail in a "PEAK" area).
P/A ON ZOOM LENSES
On most zoom lenses the control marked P/A is little more than a speed control for the iris motor and is best left in the centre of its travel to ensure best operation.
LEVEL FIXED AND ZOOM LENSES
The only correct method of setting the level control is to monitor the camera output on an oscilloscope and adjust the level control for a reading of 0.3V sync. and 0.7 volt video = 1 volt P/P total.
When an oscilloscope is not available the following method can give some surprisingly accurate results with a little experience. You should have your own installation/test monitor, and take a camera known to be set correctly to 1V P/P (a pre test service VIS can provide upon request). Feed this into the monitor and adjust the contrast and brightness until YOU think the picture is correct. NOW mark the controls so you can always set them to this position again. Now as you set up each camera set the P/A control as previously stated. With the monitor set to its "MARKED" positions adjust the ‘level’ until you see the contrast of the picture similar to that achieved with the test camera.
N.B. Never move the monitor controls no matter how tempted. You should then find all the cameras set to equivalent contrast.
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Understanding ‘F’ Stops |
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'F' STOPS
The F number is an indication of the amount of light that will be passed through a lens. The smaller the F number the more light is passed. The F number is calculated by dividing the focal length by the effective diameter of the lens. When you adjust the lens up by 1F stop, you halve the light passed through it. The F stop assumes that there are no losses in the lens.
Spot Filters
These increase the working range of a lens and can eliminate Automatic Iris 'Hunting' using a series of darker Neutral Density discs at the iris centre.
Please note: Spot Filters are built into lenses to reduce the sensitivity of the iris control.
As the iris closes down to its smallest size for bright scenes, the adjustments required are microscopic. Most scenes over 15,000 lux (sunlight) require an iris closure of 10F stops from a 15 lux scene (a range available on many lenses). Noon sunlight can range up to 1 million lux requiring an iris range of 16F stops. The 2nd 'F' stop figure quoted relates to the effective filtered ‘F' stops at iris closure. |
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| Quads and Multiplexers |
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Understanding PVP™ |
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Parallel video processing (PVP) is a function whereby the input to a multiplexer is controlled by two independent encoders which digitise the incoming image. This signal is then passed on to the framestore enabling the digital main monitor to update much faster. This allows both near real-time multi-screens and the machine to update up to 50 unique fields to the VCR when recording in 3 hour mode. This can be explained by comparing a non-PVP and a PVP multiplexer as follows.
A non-PVP multiplexer has one encoder. This means that due to the way video signals are made up, it takes 20 milli-seconds to read the video signal and a further 20 milli seconds to output this signal giving a total of 40 milliseconds, i.e. the maximum number of unique fields it can process in a single second is 25. A multiplexer with PVP has two encoders which operate independently; one can be reading a video signal whilst the other is outputting a video signal. This is achieved in 20 milliseconds, therefore giving 50 as the maximum number of unique fields processed in a second. |
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| Transmission, Telemetry, and Matrixes |
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Understanding Video Matrix Switching |
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Matrix switchers link all the camera inputs and monitor outputs into a matrix, allowing any camera to be held and sequenced on any monitor. This is very useful when the installation involves large numbers of cameras and monitors.
The term 'matrix switchers' is often used to include alarm inputs and telemetry control in the matrix, as well as the video. But telemetry control on a matrix switcher is normally via a separate twisted pair, and not via the coaxial cable. This is because coaxial telemetry control needs direct access to the coaxial cable, uninterrupted by the electronics needed by a matrix switcher.
Smaller Systems
Switcher units typically linking up to 32 cameras to four monitors, in which all the video inputs and outputs are permanently wired, are available "off the shelf". Attractive options such as character identification and number for each camera and time, date generation and telemetry control codes, are often included as standard.
Telemetry receivers, alarm input interface and control keyboards can easily be added to these units, to build sophisticated, easily installed, medium-sized CCTV systems.
Larger Systems Any number of monitors, cameras or control points can be catered for by adding boards to the switcher. Being modular, large system switchers can cater for a vast range of system size options, typically up to 64 monitors and 512 cameras, controlled from 40 different locations.
Larger systems are also normally more flexible in alarm functions, and in allowing restricted access to cameras from individual control points and to certain monitors.
The basic parameters for matrix switcher design are:
- number of keyboard points and the difference between them
- control station is rack-mounted or desktop
- number and size of monitors
- sequence and number of cameras on each monitor, and
- approximate dwell time of sequence cameras
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Wireless Video Transmission |
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The transmission distances stated are "line of sight". If the "line of sight" is partly obstructed by trees, buildings, vehicles and other bodies this will cause attenuation of the signal, resulting in reduced performance and possible picture fading.
To ensure maximum transmission distances and performance, mount the antennas as high above ground as possible with no obstructions.
Even with a clear path, reflections from intermittent traffic, pedestrians, nearby objects and the ground will occur. These reflections may cause some picture flicker.
VIS cannot guarantee your site conditions. Therefore we recommend field trials are conducted to ensure satisfactory results can be obtained on site. |
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| VCRs |
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VCR Servicing |
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VCRs, like cars, need regular servicing but also like cars this servicing is at the customers’ expense. Each manufacturer has a recommended service interval, measured in hours, but these do vary depending on site conditions and the video tapes used. It is worth remembering that, although they are only recommendations, ignoring them could, in some cases, invalidate your warranty. The service intervals start from as little as 500 hours, but average at 4,000 - 5,000 hours, so you should always make provision for this in your maintenance contracts.
VIS have a fully equipped service area and will be happy to quote for your VCR servicing. |
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01706 364 411
01706 367 600
info@networkvideocentre.co.uk