FAQ

A network video server is a computer that runs special Video Management Software known as VMS and is used to record video from IP cameras. A windows computer is usually the platform for the VMS, and video is recorded onto the computer’s hard drives in a special video format.

Sometimes people are confused by this term because a number of years back a device that attached an analogue camera to the networks was also called a video or camera server.  This is now known as a Video Encoder.

A Network Video Recorder, or NVR, is a complete IP camera recording device. It includes a computer and special Video Management Software.  VMS is required for recording video, but it also allows multiple viewers to monitor real time and recorded video.

The ability to film in low light conditions or even complete darkness is essential for many CCTV applications. Part of the that ability is down to using the right electronics which are sensitive enough to work in low light, the other tool used is infra red or IR lighting. We have a guide to infra red in our camera buying guide.

Infra red light isn’t visible to the human eye but CCTV cameras switch to black and white as light levels fall and can film the IR light spectrum. This means that to the camera its like shining a torch. IR has to bounce off something but providing there is a hard surface to reflect the infra red your camera is able to see in the dark.

Previously cameras had separate infra red light lamps bolted onto the side of their housings. It made the whole unit very large and industrial looking. In more recent times cameras have been designed with IR lighting built into them. This greatly reduces their overall size and visual impact. It also reduces cost when compared to modular cameras using separate lighting units.

Many people selling CCTV cameras describe them in terms of infra red range. Do not confuse this with the optical range of the camera or the distance at which a camera can record detail. That is determined by the lens. Wider angle lenses will have a shorter optical range, more telephoto lenses a longer range. The IR range is a largely immaterial figure, often made up and is supposed to represent the distance at which the camera’s infra red can be detected. In reality the ability of a camera is a combination of the lens, how powerful the IR is and how sensitive the electronics are.

Something you might see mentioned is an IR cut filter. This is a mecanical filter which moves in front of the camera lens during the daytime. The filter is designed to improve colour rendition during daylight filming. Electronic adjustments can also me made to the camera to improve colour representation.

We get a number of calls from people experiencing problems with their CCTV cameras at night. They install a CCTV system during the day then at night find they have issues. We have created this page to cover some of the most common symptoms and causes.

No image at night

The most extreme problem is seeing nothing at all on the screen. Check all the same things you would look at during the day. Make sure the camera has power, ensure all the connections are secure and that the infra red is illuminating (this will mean power is getting through to the camera). If that is all in order then stand in front of the camera quite close to it. Infra red needs to bounce off a surface back into the camera. If you just point the camera into space it won’t see anything.

If you have bought a camera with a long range, 20 or 30 metres plus from someone and you are expecting it to work at that distance don’t rely on quoted specs. IR range is pretty much made up and shouldn’t be used as a guide to effective range. You could be trying to film too far away. Stand closer to the camera and see it you can see an image. Failing that you may be suffering voltage drop.

Voltage drop

One of the most common problems experienced is voltage drop. When the IR illuminates the power requirement of the camera increases, if the cable run is too long or there isn’t enough copper you will experience voltage drop. This could cause the camera to stop working all together. It could also cause the camera to cycle on and off. The IR illuminates which causes the camera to switch off. The camera re-starts and works until the IR switches on again. You may also see image deterioration when voltage drop occurs. If you are using CAT5 cable to join the cameras to the DVR and power supply make sure you are using pure copper cable rather than CCA or copper clad aluminium. Wire the cameras as per our guide to CAT5 cabling or CAT 6. In particular make sure you use 3 pairs of wire for the 12 volt supply.

A white screen or white areas on the screen

This is another common issue. If you see a white screen at night or a white haze then the most likely cause is infra red light reflecting back into the camera lens. The wider the angle of view the more chance there is of this happening. Have you got the cameras sun visor too far forward? We suggest having the rear or the visor in line with the back of the camera body. Is there something just out of shot but in front of the camera which can reflect IR back into the camera, guttering and soffits are common culprits. On vandal dome cameras check to make sure any sealing rings which fit between the lens and the inside of the clear plastic cover are securely in place.

Whilst you can’t see the infra red light to the camera it is extremely bright and any surface close to the front of the camera can reflect the light back into the lens. Even if the surface is out of screen shot it can still reflect the IR. If you can’t move the camera try zooming it in more so you narrow the field of view. Light pollution from other sources can also cause white areas to appear on the screen. Vandal dome cameras are particularly prone to corruption from external light sources.

Camera mounted inside a window produces a white image at night

Well it will do. The glass is a reflective surface and is right in front of the camera. The infra red will bounce off the glass straight into the lens causing the camera to dazzle it’s self. It’s a bit like taking a flash photograph in front of a window at night.

General image deterioration at night

When the infra red switches on the camera draws more current. If your power supply is not powerful enough this extra current draw could cause problems. Also make sure you have not exceeded the recommended cable run length and that the cable is substantial enough. Voltage drops along the length of the cable and the thinner the cross sectional area of the cable the more this happens.

General haziness of the image at night with some movement on screen

Check the camera for spider webs. During the day you don’t notice spider webs. The camera focuses beyond the web and it appears invisible. At night the infra red bounces off the web and it shows very clearly. We do sell a spider spray to help reduce this problem.

Moving spots in front of the camera at night

This is similar to the spiders web problem but instead of a web the light is reflecting off dust or particles in the air. This is particularly noticeable in fog where the water droplets suspended in the air reflect the infra red. Warm currents in the air can cause particles to rise as well as fall.

We get asked if we sell CCTV kits a lot and the answer is no. We sell all the bits you need make up a cctv kit but we don’t stock the whole lot in one box and there is a very good reason.

CCTV systems use several different cameras

Everybody’s CCTV needs will be different. Some people want cameras for outside, some for inside. Some cameras need to film overall views whilst others need to film higher levels of detail. Some subjects will be close to the camera, others some distance away. The cameras will also be fitted in a variety of different locations. You begin to see that a one box solution can never provide a good CCTV solution. The most important thing to get right on a CCTV system are the cameras. We have a guide to choosing CCTV cameras elsewhere on the site.

The CCTV kits you see advertised all contain fixed lens wide angle cameras. The single worst thing you can do is use fixed lens wide angle cameras because they spread pixels apart as you move away from the camera and you don’t capture any detail. They may claim an effective range of up 20 or 30 metres but the reality will be nothing like that, probably 3 metres in standard definition.

Cables and connections

Cable distances will vary from application to application so the likelihood is whatever cables came in the box would either be too long or too short. In fact pretty much every element of a CCTV system needs to be tailored to the user’s needs. All in one box CCTV kits often have unique connectors to that particular kit meaning if you need to change a camera you can’t because no one sells equipment with those fittings. The result is everything goes in the bin and you have to buy a completely new system.

Quality

CCTV kits tend to be very poor quality. You don’t have a choice in how good or bad each element is, you simply get what’s in the box. Because they are sold to a price one box CCTV systems tend to contain decidedly average quality equipment other than the outer box it’s self. That will be bright, colourful and contains words such as professional, high quality, razor sharp, pinpoint, high definition and so on. They almost spend more money on the box than the contents!

Buy what you need

We allow you to choose elements of your CCTV system individually to make sure you end up with exactly what you need. Save money in areas where conditions are less demanding, buy the right gear for the job where things get a little tougher or results are more critical.

We still reflect the fact you’re not just buying a single camera by including a free power supply when you buy 4 cameras. We fit the hard drive into the DVR recorder, format it and configure the DVR settings free of charge to save you having to wade through a 60 page instruction manual. We also include a good quality warning sign pack should you need one. Remember we are happy to offer free help and advice to make sure you buy the right kit.

This isn’t an exhaustive list of problems encountered at night but it covers the most common ones.

Motion detected recording is a feature on all our DVR recorders. The DVR monitors camera images and decides when it thinks there is movement. To do this the DVR looks at individual image frames and compares them to the previous one. If it sees differences then motion is assumed to have taken place. It is the DVR not the cameras which is looking for movement.

A DVR isn’t as intelligent as you or I and can’t differentiate between background movement, changes in light and someone coming to break into your property. To help minimise false triggers it is possible to limit where on the screen the DVR looks for movement and limit this to a small area or a number of areas. You don’t have to use the full screen. You can set the trigger area using the set up menu on the DVR, you can also set the trigger area remotely if the DVR is connected to your local network / the internet.

Some people only record footage when motion is detected in an attempt to extend the time footage is stored. We are not big fans of doing this. We would rather see motion triggering being used to create bookmarks within 24/7 recording rather than the sole means of capturing footage. Use it to identify which sections might be important but still have constant footage either side of the trigger.

Systems which use motion triggering as the sole method of recording are usually trying to compensate for too little memory. We recommend allowing 250GB of hard drive space per camera on SD systems, 500GB per camera on HD systems

A CCTV system will be based around a DVR or digital video recorder. CCTV cameras are connected to the DVR using cables and there will be some ancillary items such as a power supply for the cameras.

DVR or digital video recorder

The DVR is the heart of the CCTV system. It takes all the camera inputs, arranges them on screen for live viewing and also stores footage onto a hard drive for viewing at a later date. Our DVRs record all the cameras regardless of what you are viewing live on your monitor. It is possible to view 1 camera at a time or several camera in various combinations depending on how many channels the DVR supports. We sell 4, 8 and 16 channel DVRs which are suitable for 4, 8 or 16 cameras respectively. They can be combined, so 2 16 channel DVRs could host a 32 camera CCTV system.

Our DVR recorders also support remote access over the internet. You need to connect the DVR to your internet router. This can be done either with a cable, a power bridge adapter which uses your electrical wiring or a wireless network point. Then wherever you are in the world you can view live footage from your cameras, see previously recorded footage, make back ups of important events and even make settings changes to the DVR.

The cameras

CCTV cameras are the most important thing to get right and we have devoted quite a bit of space on our website to helping you make the right choice. We are always glad to offer help and advice if you are planning a CCTV system so pick up the phone and give us a call. We can have a look at your property using aerial images whilst talking through your specific requirements and select which cameras will best suit your requirements.

Cables

The cable from the DVR to the camera does 2 jobs. It transfers video from the camera back to the DVR and it supplies 12 volt power to the camera. Video connection is via a BNC connector. If you are using CAT5 cable then the BNC connector will be part of the Video Baluns.  12 volt power connections are 5.5mm jack plugs. At the camera end there is a DC plug, at the DVR end a DC socket into which the 12 volt power supply for the camera connects. For this reason you would normally locate the camera power supply next to the DVR unit. The DVR will be supplied with it’s own 12 volt power supply.

What is a PTZ camera ?

PTZ stands for Pan, Tilt, Zoom. PTZ cameras can be remotely controlled allowing it to move up and down as well as zoom in on potentially important targets. You can also program a tour between pre-set points. In theory PTZ cameras sound great, they can cover large areas and even zoom in when more detail is required.

The downsides of using a PTZ camera

PTZ cameras are expensive, certainly good ones are. There are a few low quality products on the market aimed at the bottom end of the DIY market, these should be avoided. However the biggest problem with PTZ cameras is that you need a full time operator to control them. When pointing in one direction they can’t see elsewhere.

When the camera is moving the image will be blurred meaning you can’t get any detail or identify people. So when you set the camera on a tour between preset points the image will be blurred for a large part of the recording.

Infra red illumination is often not fitted to PTZ cameras meaning they are less effective at night. It is possible to find PTZ cameras with effective IR and our PTZ cameras feature zoom sensitive IR which increases brightness as you zoom in, the assumption being you are hoping to see further away.

Latency when remote accessing the cameras. When remote accessing PTZ cameras there is a delay between you asking a camera to move and seeing the result of that movement on your remote monitor or computer. This is known as latency and it can make it difficult to accurately control PTZ cameras remotely over the internet.

Consider fitting more fixed cameras

Rather than use a PTZ camera consider fitting more fixed cameras for the same cost as a single PTZ camera. That way you will cover all the views all the time. You also don’t need the expense of a full time operator. There are some “self tracking” cameras which identify targets and keep following them, the problem is the image will be blurred when the camera moves and how does the camera know who to track when faced with multiple targets. Thieves often work in gangs.

PTZ cameras do have their uses but in the vast majority of cases you are better off using more fixed cameras.

Like everything in life CCTV is available at a range of different prices points and quality levels. You can fly on a plane for $800 in economy or you can pay $5,500 to fly on the same plane in a first class suite.

The problem with CCTV is a lack of regulation and failure to understand the basic principles means people often sell systems which won’t do what they claim. They sell you a first class suite but you board the plane to find yourself squeezed into a small economy seat. Actually its worse than that, they sell you a first class suite to New York but you get to sit on an orange crate whilst the plane flys to Luton.

People selling CCTV tell lies

We set up Bright wires as frustrated customers. We did our homework, looked at the specifications, listened to the sales patter and were very disappointed with what turned up. When you know what you are looking at the claims made by people selling CCTV are appalling. It isn’t just the odd seller on ebay, it’s rife across the industry. Big national retailers are misleading buyers in an attempt to get their money.

When you see a camera with a claimed range of 25 metres you assume it’s capable of filming something 25 metres away. You might allow a bit of artistic licence and work on 20 metres to be safe but the reality is it might only have an optical range of 3 or 4 metres.

The specifications retailers use are often not important

Sticking with CCTV cameras as our example retailers often use TVL (television lines) as a determining factor in how good or bad their products are. The number of TV lines has little to do with the quality of a camera, that is more to do with the lens fitted and its optical range. Even if TVL was important retailers rarely quote TVL correctly, they advertise 560TVL cameras as 1000 TVL cameras because they don’t understand how TVL is calculated.

We have recently added our camera buying guide which has a section specifically about CCTV camera range. It’s worth spending some time reading through the guides as they will answer most or all of the questions you might have. If you need help regarding a specific project please don’t hesitate to get in touch, we are always happy to provide advice free of charge and without obligation.

TVL and IR range

People selling CCTV are often very misleading when it comes to CCTV camera range. They normally quote two figures, the number of TVL and the IR range. This might be called the night time range. IR range is a largely made up number based around how far away from the camera Infra red light can be detected. It has nothing at all to do with the effective range at which detail can be filmed.

Optical range

The distance at which detail can be captured using a camera is its optical range. Unfortunately no one every quotes it, they only quote the IR range. The optical range has nothing to do with how many TVL the camera has or how bright the IR is, it all depends on what lens is fitted.

A DVR stores images as tiny dots or pixels. With D1 resolution you get around 400,000 pixels per image frame. With a wide angle lens the pixels spread apart very quickly as you move away from the camera and fewer pixels mean less detail is captured. Conversely a more telephoto lens concentrates the pixels and captures more detail further from the camera. Camera lenses are measured in mm, the smaller the number the wider the angle of view. 2.8mm or 3.6mm would be considered wide angle.

How do you quantify detail?

There is no definitive answer, it will depend on your specific needs. With some systems the ability to identify people will determine detail, on other systems it might be the ability to read a vehicle registration plate. When we quote optical ranges we base them around how far from the camera a vehicle registration plate can be read.

We have a page which shows HD1080P CCTV camera images with different lens options

Varifocal cameras

A varifocal camera allows you to manually zoom in or out during installation. This means one camera is able to perform different jobs. It can be set to wide angle or telephoto. This means you don’t have to worry as much when buying the camera, you can balance the angle of view and detail captured once it is fitted. You just need to make sure you have the correct lens range, we can help you decide.

With fixed lens cameras you only get one chance, if its the wrong angle you have to replace the camera. For that reason we would always advise buying varifocal rather than fixed lens cameras.

An approximate guide to the optical range of different lens cameras ie. the distance at which a number plate or a person can be identified using standard definition CCTV. For HD1080P systems you can double these figures.

In recent years the invention of the video balun has meant CAT5e cable can be used to connect CCTV cameras to CCTV DVR recorders. All the connections can be made using only a screwdriver, no need for special tools or fiddly components. Before you start there are a couple of important things to know.

What components do I need?

Video is transmitted along the CAT5e cable using a pair of video baluns, one at the DVR end, one at the camera end. We sell 2 types of video baluns, Standard definition and High definition designed to be used with our HD 1080P cameras and DVR recorders. Power is transmitted using using screw in DC plugs and sockets. The plug goes at camera end the socket at the DVR end. Locate the camera power supply close to the DVR.

Use the correct type of CAT5e cable

You must use pure copper CAT5 cable . Some CAT5 cable is not pure copper but CCA or copper coated aluminum. Don’t rely on the label or what the retailer says, actually check the cable yourself. CAT5, CAT5e, CAT6 and CAT6e can all be CCA rather than pure copper. CCA tends to break easily when bent and you can scrape the copper off to reveal silver coloured metal in the centre. All the cable we sell is pure copper external grade.

Don’t exceed the maximum cable run

The maximum distance video signal can be transferred with our video baluns is approximately 300 metres. If you are using the cable to power a camera as well as transfer video signal then we would suggest a maximum distance of about 50 metres to avoid voltage drop. This assumes you are using 3 pairs of wire for 12 volt supply and 1 pair for video signal transfer as per our images below.

Use a colour convention, stick to it and check carefully

It is important to check your wiring carefully. Choose a colour convention and stick to it. In the examples below we have used blue for video signal and solid colour for +ve, white plus coloured stripe for -ve.

You need to run 1 length of CAT5e cable from the DVR recorder to each camera. The cable is going to do 2 jobs. One pair of wires will handle the video signal, the other 3 pairs of wires will be combined to take 12 volt power from the transformer located next to the DVR to the camera.

Firstly identify the polarity for all your connectors

Separate the 4 pairs of wires in the Cat5e cable. In this case we are going to use the blue pair for transferring video signal from the camera to the DVR. Keep this pair twisted, to reduce the chance of interference.

The green, brown and orange pairs are going to be used to take 12 volt power from the transformer to the camera. We use 3 pairs of wires combined to reduce the risk of voltage drop at the camera. Having unwound the wire use the solid colour for 12 volt +ve and the white with coloured trace for 12 volt -ve.

Here we can see the cables inserted into a video balun and a power plug.

Remember to strip back the outer plastic sheath to reveal the copper conductor before pushing into the fittings and tightening the connector with a small screwdriver.

Note how we have combined the 3 pairs of wires for the 12 volt DC fitting.

Be aware the DC power fittings are different for the DVR end of the cable and the camera end of the cable. The DVR end requires a female socket to take the 12 volt power from power supply.

The camera end requires a male DC plug To take 12 volt power to the camera

It is important to protect the fittings from water so we recommend using weather proof junction boxes by each camera. All the components you need are available in the CCTV accessories section of our online shop.

Each week we speak to a lot of people planning CCTV systems. No two conversations are ever the same but the subject of wireless CCTV and in particular wireless CCTV cameras often comes up. In theory wireless offers the ideal solution, no cables to run means installation times are reduced. So why don’t we sell wireless CCTV?

Before you buy wireless CCTV cameras or a wireless system read this.

There are a number of problems with wireless CCTV. Firstly it isn’t actually wireless, you still need to power the cameras via a cable. Wireless cameras tend to be fairly poor quality aimed at the lower end of the DIY market. The electronics aren’t great and you only have a limited choice of lens options. Choosing the correct lens CCTV camera is the single most important factor in determining the overall quality of your CCTV system. Read our camera buying guide to understand what you need to consider when looking at CCTV cameras.

Wireless problems and limitations

The wireless link it’s self often causes problems. In the UK a lot of other devices share the relatively narrow frequency bands allocated to this sort of device. Wireless routers which stream the internet around your home share the same 2.4GHz frequency of many wireless CCTV systems for instance. Microwaves, baby monitors, bluetooth devices, structural building components, cordless telephones, walls and other solid objects are just some of the things which can get in the way of a potential signal.

2.4GHz or 5.8GHz

There are 2 frequencies in use, 2.4GHz and 5.8GHz. In theory 5.8 GHz wireless transmission is supposed to suffer less interference than 2.4 GHz but that is changing as more and more devices switch to the higher frequency. The higher frequency also tends to be blocked more readily by solid objects such as walls. Whether you choose 2.4 or 5.8 GHz there is one thing which is unavoidable, the power limit imposed on unlicensed wireless devices in the UK. Keep this in mind if you ever watch a demonstration of wireless CCTV technology, was it made in the UK using unlicensed equipment or overseas where no such limitations exist?

Licensed products

There are wireless solutions with improved power outputs but these require specialised professional licenses and the systems are expensive. Often the wireless link alone costs more than a typical system from ourselves. For unlicensed wireless cameras totally ignore the claims in terms of range and image quality.

Hard wired CCTV is best

A wired solution will always give the best results. It might take a little more time to install initially but you only have to do it once. CAT5 cable when used in conjunction with a simple pair of passive video baluns can transmit video signals up to 300 metres without deterioration. Switch to active baluns and that distance increases to an incredible 1,200 metres far in excess of any wireless Camera.

We have recently created a CCTV camera buying guide which should answer most of your questions relating to cameras and which one to use.

When people call us on the phone to discuss their needs they usually start by describing each area of the property to be secured. “I want a camera to cover my front garden which is 23 metres long by 18 metres wide. We need to cover the gate in the middle and driveway to the side and I’d also like to cover my ornamental fountain which is over by the neighbour’s wall”

The problem with CCTV is that you can’t cover vast areas with a single camera. Or rather you can, but the trade off is no one area will get special attention in terms of detail recorded. Even with high definition CCTV cameras once you widen the angle of what the camera sees recorded detail drops off dramatically. Think about it, you have a given number of pixels across the screen and as you move away from the camera the area the camera sees increases but that means the pixel density decreases. It doesn’t help that many people selling CCTV tell lies and claim their wide angle CCTV cameras can film crystal clear detail at distances of 20 metres or more. Typically a 75 degree angle of view camera has an effective optical range of up to 3 metres in standard definition, 6 metres in HD1080P.

When that person looked around their garden they moved their head and focussed in on the areas of interest, the gate, the fountain and the driveway. A CCTV camera can’t do this, it shares it’s attention across the whole screen.

Zooming in electronically, increasing the TVL (number of TV lines) or increasing the number of megapixels wont help. You need to increase pixels by a factor of 4 to double the identification distance of the camera. The only way to get more detail in these areas is to optically zoom the camera in on an area, but it can only look in one place at a time. So there is a trade off with CCTV cameras, you either have a wide angle of view or you have good levels of detail. You can’t have both.

Think carefully about where you actually need to film and how much detail you need to capture when calculating which CCTV cameras to use. Don’t try to machine gun the whole of an area with CCTV, it won’t work. Instead try to think of your site in terms of specific target points where you can capture information. Obviously there might be some instances where all you need is an overall view, but don’t kid yourself that you will be recording footage from which you can read number plates or identify people. Here in our offices we have a camera which films the front car parking area. It can’t be seen from the office and so we just want to know as and when someone arrives. A separate camera films them close up as they drive in to record number plate details and so on.

If you are planning a specific CCTV project we are always happy to help. We can look at your site using internet mapping from which we can take accurate measurements. At the same time we can chat on the phone to understand exactly what you want the CCTV system to do for you. From there we will be able to put together a list of equipment including the correct cameras. There is no charge for this and you are under no obligation.

CCTV matrix – real or virtual

CCTV Handbook 2006 CCTV, Surveillance & Remote Monitoring

The traditional analog matrix is under threat from IP video systems which use a so-called virtual matrix. But are they a true replacement and can they offer the many benefits promised by IP-based solutions? Shawn Ciccarelli of CCTV and security equipment distributor Norbain SA, compares the two technologies and separates fact from fiction.

Analog matrix

The core of most traditional analog CCTV systems is the video matrix. This is typically an electronics rack that is situated close to the control room. The matrix is a switch that routes video inputs from cameras to video outputs that are fed to monitors and DVRs/VCRs for recording as required. This is achieved by the operator(s) using desk-mounted keyboard controls.

Virtual matrix

A virtual matrix runs on a data network LAN, WAN or MAN (local, wide or metropolitan area network) that carries information encoded as TCP/IP (Transfer Control Protocol/Internet Protocol). Such networks are now ubiquitous and installed as a matter of course into new buildings as part of the communications infrastructure. The term ‘IP network’ is now a common phrase to describe this type of network.

In a digital CCTV system the analog video from the camera has to be converted to digital data for transmission over the IP network. This usually takes place at the camera in the form of an analog CCTV camera connected to a separate encoder unit (‘transmitter’) nearby, or by using a self-contained IP camera. Either way the result is the same, it is the encoded digital video that travels along the network cabling.

Whereas an analog hardware matrix switches video and PTZ (pan/tilt/zoom) controls, a virtual matrix will also handle the processing of alarm and access control data. It will also accommodate the communications required for VOIP (Voice over IP) and bi-directional, full-duplex audio.

The switching of camera feeds to monitors and recorders is achieved by the video management software. The software, which is normally PC-based, manages the control, administration and viewing of the live camera feeds and recorded video over the IP network. The software allows the operator, with the appropriate permissions, to view/analyse live and recorded video from any camera. Operator PC stations running the software can be located anywhere on the network, which allows for the design of truly distributed systems. The network routes the data directly to the appropriate receiver, there is no central switch as with an analog matrix.

The typical NVR solution simply requires a PC platform and hard disk storage. However, for more demanding fault tolerant applications NVRs can be packaged in standalone units with removable hard disk drives.

Performance

The virtual matrix approach can only be justified if the performance of the final CCTV system is at least as good as an equivalent analog system. So let us take a look at some of the more important considerations when comparing technologies.

Image quality

With modern compression techniques the argument that the picture quality of digitally transmitted images is inferior to analog is really redundant. Modern MPEG-4 compression technologies are capable of encoding the complete image at full resolution – 4CIF, and transmitting them around the network at full frame rate (25 fps for PAL, 30 fps for NTSC).

It can be argued that digital video is often superior to analog transmitted images since IP-based transmission is lossless. Image quality obtained at the receiving end, be it monitoring console or networked video recorder (NVR) is identical to that transmitted. No degradation occurs during transmission, recording or playback.

Reliability

An analog matrix is in effect a single point of failure and a catastrophic failure of the incoming video communication lines, switching, monitoring or recording equipment can bring the whole system down.

In a virtual matrix if part of the network, monitoring or recording equipment goes down the rest of the system can continue to operate as normal. In fact it goes further than this -redundant power supplies and network ports are now built into equipment as standard, and these provide ‘hot standby’ operation.

If one network path fails, another can be automatically swapped in. NVRs can also be distributed around the network providing further levels of redundancy.

Scalability

This is perhaps one of the most important differentiators between the two technologies. To expand a system that uses an analog matrix requires additional coax/fibre cabling, that has to be wired to a single location, and hardware or even a new matrix if the original unit is full. This is clearly expensive in both cabling and extra hardware, particularly if the new additions are remote from the matrix. With a virtual matrix, however, you just add the desired cameras, monitors, recorders or control positions to any point on the network and the job is done. It is totally scalable to an almost infinite degree.

The real answer to expanding existing analog matrix systems is to add an IP video system for the additional cameras and equipment. This fully-integrated hybrid system maintains the original investment in CCTV equipment while providing an expansion path for the future. When the old analog matrix and associated DVRs reach the end of their working lives they can simply be replaced with the virtual matrix and NVRs.

Video recording

An analog system would normally use digital video recorders (DVRs) connected directly to the matrix, whereas in a virtual matrix system networked video recorders (NVRs) are used. It is important to differentiate between DVRs and NVRs, as both are often termed ‘digital’. A DVR digitally compresses analog video feeds and stores them on a hard-drive, the term ‘digital’ referring to the compression and storage technology, not the transmitted video images. The DVR therefore has to be located near the analog matrix. In contrast an NVR stores digital images directly from the IP network.

The advantage of an architecture based on NVRs is that they can be located anywhere on a network – at the monitoring centre, adjacent to camera clusters, on the edge of a network or collected together in a hardened environment. In use their location is transparent to an operator; the recorded video stream from any camera can be viewed by any operator at any point on the network. NVRs record and replay simultaneously and recordings on any one machine can be remotely viewed by a number of authorised operators spread across the network simultaneously, all totally independently and without affecting each other.

Cost

In many cases the bandwidth needed to transmit CCTV across an existing network can be easily accommodated on the existing corporate network, giving the virtual matrix a distinct cost advantage over analog systems by removing the need for additional cabling. This infrastructure is not only carrying and switching video images, but alarms, control signals, access control data and audio as well. IP network switches are typically 10% of the cost of analog matrices with an equivalent number of ports.

Latency

It really does not matter if the operator witnesses an event one or two tenths of a second after it really happened. The time when latency matters is when an operator is following a target using pan/tilt/zoom controls. If there is any significant delay in the camera image being updated, as the camera is being moved to track the target, it becomes difficult for the target to be followed successfully.

In virtual matrix systems latency occurs when the bandwidth of the transmission channel is insufficient for the volume of data that is being applied to it, and will not happen in a well-designed system. In the event there are two possible remedies – increase the available bandwidth or reduce the data volume, or both. A number of techniques to manage bandwidth can be employed – see below.

Network bandwidth

This is one of the most common arguments employed to denigrate the virtual matrix, and yet it has no real substance. In some circumstances the bandwidth may need increasing, but that is still preferable to laying down a totally new, but already technologically outdated, analog cabling infrastructure.

There are some well-proven techniques for reducing the bandwidth loading on a network, such as:

* Positioning the NVRs near (in network terms) the camera clusters.

* Using Multicast technology – this is where hundreds of operators in different locations can view the same camera feeds but use no more network traffic than one operator.

* Using ACF (activity controlled framerate) at the camera – the video transmission rate is adjusted based on scene activity. This reduces both network traffic and recording space. You would not buy a sports car and expect to get best performance on a dirt track! The same is true for IP video systems: to operate effectively, the network must be correctly specified, configured and maintained.

The main arguments against the implementation of IP video systems using a virtual matrix have clearly been made redundant. This is borne out by the increasing number of high-profile installations of IP video systems around the world, such as the two most recent Olympic Games in Athens and Turin, where over 2500 cameras were successfully integrated using IP video technology. The flexibility and scalability offered by IP video systems means they can be used for applications that are just not possible or cost effective with analog CCTV solutions, opening up new opportunities for end-users and systems integrators alike.

How do wireless alarm systems work?

Wireless alarm systems can be installed in places where wired alarm systems cannot be accommodated. They are perfect if you don’t have a pre-installed security system because there is no need to install anything else. No more screws, cables or installation work.

How do home alarm systems prevent burglaries?

Home alarm systems can’t prevent burglary attempts, but they definitely will catch anyone who tries! If you have one of the best home alarm systems installed, your family’s safety and home safety will be guaranteed. Your best allies are the motion detector, surveillance camera, door alarms or whichever features your system provides.

How do motion-sensor alarms work?

The outdoor motion-sensor alarm provides you with the best security. It is a good way to protect the perimeter of your home or business. The indoor motion-sensor alarm emits radio energy into each room, then keeps monitoring the reflection pattern in that same space, while another device reads the changes in energy around that same area.

Why do I need a security alarm system?

Even if your neighbourhood is quiet, and you have known your neighbours for years, that is not enough to protect your home from burglars. Burglaries happen quite often in the UK, and for this reason, it is essential that you not only take care of your home through upkeep, but also install a security alarm system for everyday protection.

Why are wireless home alarm systems better?

Wireless home alarm systems offer many advantages compared with wired systems:

• Installation is quicker and easier
• Replaceable batteries provide longer life spans
• Easily replaceable sensors
• Less maintenance
• Lower costs
• Easy to remove if needed
• What makes the best wireless alarm system?
• The best wireless alarm systemis inexpensive and requires very little work on your part. It also should provide many different sensors and detectors and have a good battery-backup system. Over the years, wireless home alarm systems have come to incorporate all the features of a wired system.