Guide to CCTV – Introduction
There are a vast range of CCTV products and prices to choose from in the marketplace but little information to help discriminate between them. Here are some examples.
A camera described as good in low-level light will often not produce images at night unless there is additional lighting. There may be no explanation or qualification of the term low-level light.
Wireless cameras can be fitted in minutes as there are no cables to run back to your TV or monitor. However, the cameras still require a power source and while battery power is convenient the consumption is great giving a working time of less than 24 hours (as low as 2 on some products tested).
Wireless connectivity is nevertheless very useful for some applications as described later.
There are plenty of professional CCTV installers who will give you a site survey and recommend appropriate products but, of course, you pay for this service. Modern technology has now made CCTV products much more affordable and they can be very easy to fit for the average DIY person. This guide will help you choose the correct products and show some simple methods of fitting complete systems to domestic and commercial properties. DIY CCTV Systems can easily be fitted by people with moderate DIY skills.
The traditional CCTV camera has a very industrial style and, therefore, many people would not find this suitable for fitting to their homes or shops.
This traditional style is actually a housing that is designed to keep the camera dry and within the recommended operating temperature. Thermostatic heating elements within the casing also reduce condensation and misting.
These types of top-end cameras are usually specified without a lens, this being chosen to give the required focal length and field of view. Motorised pan and zoom lenses allow an observer to follow or move in closer to the person or object in view.
We can supply these types of cameras to those of you who do not find the price prohibitive.
Fortunately, for those of us with more down-to-earth budgets modern technologies now allow the production of cameras with excellent performance. There are two common types of CCTV cameras, CMOS and CCD (see glossary of terms). CMOS based cameras are generally cheaper but do not produce as clear or sharp images as CCD cameras. There is little point installing a CCTV camera if it is incapable of allowing you to easily identify who or what is being captured and recorded. CCD cameras provide pin-point clarity and should be specified wherever possible.
The KT&C, Everfocus and Concept camera range, in general use the Sony CCD chipset. Beware of competing products that do not state whose chipset is used.
Integrated cameras and lenses often referred to as “bullet cameras” are sealed to prevent ingress of moisture. The sealing is so good that they can be permanently immersed to some considerable depth in water if required.
Bullet cameras do not need a heater and their small size makes them highly suitable for fitting to domestic and commercial properties. It is not possible to make adjustment to these cameras because they are permanently sealed. Most of the bullet cameras are fitted with a 3.6mm lens which gives a 72 deg angle of view which is suitable for most domestic and small commercial properties. Please contact us if you require alternatives.
Choosing a Camera Specification
The main criteria of a camera’s performance are its sensitivity and resolution. Secondary considerations are colour or monochrome and indoor or outdoor suitability.
Sensitivity is the camera’s ability to respond to light levels. Resolution defines the amount of picture detail in the image produced by the camera.
This is expressed as the number of television lines that the camera is capable of producing. For example the KT&C monochrome bullet camera is classed as 420 lines or usually 420 TVL. The comparable colour model is 380 TVL
These are typical figures for CCD cameras, CMOS cameras are usually lower.
Higher resolution cameras of over 500 TVL are available for select applications. For example, trying to read the number plate of a fast moving car would need the best resolution affordable. You should be able to read a stationary number with a resolution of 380 TVL. Below 300TVL and using CMOS cameras even facial features will be difficult to distinguish. These are very broad guidelines and also depend on the light levels and shadow conditions.
If a camera is to be sited outside and is not going to be mounted in an enclosure it must be classed as weather resistant.
The cable entry points are sealed and most bullet cameras come with trailing leads that allows the connections to be made inside the building. Typically 18ins (45cm) should be sufficient. One bullet camera under review had only a few centimetres of cable. This means the connection would be exposed to the rigours of the weather. Needless to say this model did not meet the selection criteria of IPTEC.
The strength and durability of the casing is difficult to quantify but we have rejected cameras with flimsy plastic enclosures, particularly wireless cameras where the antenna dish looks like it could be easily damaged. The range of KT&C bullet cameras have strong aluminium bodies and sealed cable entry points and were selected for these features.
Choosing the correct camera to operate in the ambient light conditions is possibly the most important although most tricky specification to understand.
Light levels are usually measured in Lux. This is a measure of the light energy arriving on an area 1m2 of surface per second.
Typical light levels are:
- Full Summer Sunlight: 50,000 Lux
- Dull Daylight: 10,000 Lux
- Shop/Office environment: 500 Lux
- Dawn/Dusk: 1 – 10 Lux
- Main Street Lighting: 30 Lux
- Side Street Lighting: 0.5 – 3 Lux
The golden rule when deciding which camera to use for a given lighting condition is not to choose one that will only just give a picture. Try to give the camera approximately 10 times its quoted minimum scene illumination. Most cameras will be able to cope with excess light. The major problem is when they do not have enough light to produce a picture.
The sensitivity of covert cameras with pin-hole lenses are often quoted as 0.1Lux @f1.4. This seems to indicate that the camera will work in ¼ moonlight. Actually the pin-hole lens will have an aperture ratio of something like f4 and so the camera will need approximately 1 Lux to produce a picture.
Unless your house is directly under main-street lighting the light level is probably less than 1 Lux at the front and even lower at the back. Bright security flood lights in theory help but often produce dark shadows a short distance from the house.
A monochrome camera rated at 0.05 Lux will produce reasonable results. Colour needs a little more. However, colour cameras achieve good night-time vision by switching to a monochrome mode. You will never get good night-time colour pictures without huge amounts of additional lighting. So think carefully about the added cost of colour over monochrome cameras. As most people are used to colour television it sets a standard so it is very common to still select a colour camera knowing it will switch to monochrome mode at night.
Monochrome cameras respond well to additional IR (infra red) lighting. With this in mind true night-vision cameras include a ring of IR LEDs. Colour cameras also offer IR illumination but as stated previously will switch to monochrome at night even with the IR LEDs turned on. These are true night-vision cameras and are rate at 0 Lux.
How to display the picture from more than one camera
Most CCTV systems deploy several cameras so a method is required to view and record the images. Simple, says the professional, use a video switcher, a quad or a multiplexer. DVRs (digital video recorder) now have multiplexer built into them but it still useful to understand the basic principles. Here are the simple benefits of each system.
A CCTV switcher is a unit that changes between camera pictures one at a time, the output being viewed on a monitor or passed to the recording device. As switchers can use any VCR to record in true real-time, the pictures which are captured can be of a very high quality. Many professionals under-rate switchers. The fact that they provide true real-time recording unlike a snapshot from a multiplexer means they provide a superior picture quality. This can sometimes outweigh the disadvantages that switchers can only record one picture at a time.
When to use a switcher
Use for low cost systems
Advantages – Simple, low cost, good quality real-time pictures.
Disadvantage – Can only record one camera at a time.
Quad units enable 4 camera pictures to be displayed on a screen simultaneously.
When to use a quadsplitter
They are useful where it is necessary to monitor several areas at the same time. As with a switcher, what is seen on the monitor is the picture that is recorded on the VCR.
Advantages – Simple to use – shows multiple displays
Disadvantage – Records only 1 camera at a time or 4 at a quarter of the screen size
A multiplexer allows simultaneous recording of multiple full-sized camera pictures on to one VCR tape providing more comprehensive recorded surveillance than with a switcher or a quadsplitter. Most have variable display options such as quad and picture in a picture allowing flexible surveillance of more than one camera at once.
When to use a multiplexer
Generally use when a high degree of surveillance is required and it is necessary to record full-size pictures from a number of cameras at the same time.
Advantages – Records all camera pictures full size on one tape – gives better monitoring of areas simultaneously – enables large areas to be monitored without losing surveillance due to camera switching time.
Disadvantages – Does not record in real time – Raises the overall cost of the system.
More on Multiplexers
Video multiplexers overcome the problems of both switchers and screen splitters. The pictures from the cameras arrive at the multiplexer unsynchronised. i.e. they all start and end their picture at different times.
These signals cannot be recorded directly because a VCR needs to be synchronised to the incoming video signal. If the incoming video signal is constantly changing then the VCR would be permanently re-synchronising to the new video signal. This can take up to 1 second to achieve.
Multiplexers digitally grab pictures from each camera in turn and feed them out to a video recorder at exactly the correct rate for them to be recorded reliably. Hence, up to 50 different pictures can be recorded every second and from any of the cameras connected to the multiplexer.
Functions of Video Multiplexers
There are three main functions a video multiplexer can perform:
Encoding – taking a single picture from each camera in turn and feeding it out to a video recorder in rapid succession.
Decoding – playing back previously encoded recordings showing only the selected camera for display
Multi-screen – showing live pictures in many different formats including PIP (picture in a picture) and split screen up to 16 ways.
Types of Video Multiplexers
Simplex – capable of performing any one of the above functions at any one time.
Duplex – capable of performing any two of the above functions at any one time (normally encoding of cameras and generating a live multi-screen picture).
Duplex multiplexers can simultaneously record and play back but this will require two video recorders.
Triplex – capable of performing all three functions at the same time (simultaneous recording and playback of cameras and a multi-screen display with both live and playback images). This allows the operator to keep monitoring the site whilst reviewing previously recorded tapes.
Added Functions of Multiplexers
Since the images are digitised it is easy to add the function of motion detect. Most multiplexers also offer alarm input and output modes.
Recording CCTV Images
The simplest low-cost solution is to use a domestic VCR. These will typically give 8 hours recording time and can be used in conjunction with Video Remote Control module to provide event-only recording.
Disadvantages – most domestic recorders have a slow “take-up” time. (the time taken to start recording)
– cannot use the VCR to record TV channel whilst camera input is selected.
Advantages – very low cost. Worth considering purchase of a dedicated VCR for camera recording. The dedicated VCR can be hidden in the attic or a cupboard making it less likely to stolen by an intruder.
Similar to a domestic VCR but with a slower-moving tape that records the camera pictures as snapshots at split second intervals. The time-lapse can be set to give 24, 240 or 960 hours of recording on standard VCR tapes.
Disadvantages – the longer the recording time the longer the period of time between the snapshots.
Advantages – very long recording time, cost-effective. Added features like alarms, auto tape-rewind.
A digital video recorder will take analogue images from a cctv camera, digitise them and store them electronically. The most common media for storage is a hard disk drive as used in most personal computers.
Most DVRs now come combined with multiplexer and motion detect functions and are generally considered the future of cctv recording.
DVRs can generally be split into two groups – standalone black box and PC-based solutions. PC-based solutions are discussed in their own section.
All-in-one box for recording, multiplexing, alarms and motion detection, making the installation of a cctv system much simpler.
Higher resolution than S-VHS VCR is possible Near instant access to recording from known time and date No loss of quality when copies taken Large storage capacity eliminates the need to frequently change tapes Can record events in real-time before an alarm actually occurs with “Pre-event trigger” Enhanced playback function, forward and reverse frame by frame playback Easy to connect to networks/internet for remote viewing and playback.
At first glance the cost seems high but taking into consideration the cost of separate units of recorder, multiplexer, alarms and motion detect the all-in-one box now proves to be a viable solution.
How to choose a DVR for CCTV applications
1 Number of Channels.
Most DVRs are classified by the number of channels or cameras that can be connected. Typical configurations are 1, 4, 8 or 16 channels. Consider carefully how many cameras are required, both now and in the future. It is sensible to pay a little more now and have room for expansion at a later date.
2 Display Resolution and Record Resolution
The display (live images) and record (captured to hard drive) resolutions are a digital signal and they are stated in pixels (picture elements).
The common standards for composite video signals are as follows
- CIF 352 x 288
- 2CIF 704 x 288
- D1 704 x 576
D1 is the same as most domestic DVD players but CIF is still way higher than the resolution achieved on VHS tape.
There are numerous resolutions in and around the above standards, each DVR manufacturer may cut down on the resolution to save cost.
Surprisingly, Display and Record resolutions are often not the same.
Check the record resolution meets your requirements. Ignore claims of high resolution display.
DVRs with a VGA -type output signal can upscale the picture to a higher display resolution. For example, a display resolution of 1280 x 1024. This is purely to allow the use of a PC-type monitor and will not enhance the image quality. If the image quality is not present in the original recording upscaling will not produce better clarity.
3 Frame Rates
A CCTV camera operating under the PAL system will produce 25 frames per second (fps). This is the maximum rate that can be recorded.
It is usually not necessary to record at the highest rate. Lower rates will save disk space. The human cannot detect a frame rate of greater than about 12fps. For most applications a recording rate of 3 or 6 fps is adequate.
Many recorders will capture images at D1 resolution at 25fps shared across all channels (that is 6fps per camera on a 4 camera system). However, they will capture CIF images at 100fps (25fps per camera)
As a guide to different applications the following may be useful:
|Application||Typical Recording Rates (Frames per Sec)|
|Car Parking, external people movement||0.5-2fps|
When comparing with the specifications of other DVRs make sure the recording rates are not quoted in fields per second. (1 frame = 2 fields)
4 Method of Channel Display.
This is similar to the functions carried out by Switchers, Quads and Multiplexers. A single channel recorder will probably not have any of these functions so will need the additional purchase of this type of unit.
The better DVRs have full multiplexer functions built into them. This is the desired type of product. A 4 channel DVR will split the screen into 4 and display one camera in each window. Similarly a 16 channel DVR will give a 4 by 4 matrix to display all channels. All other functions of multiplexers like alarms, time and date stamping should be available.
A Triplex DVR will perform the functions of encode, display and record simultaneously. They will usually also allow several other simultaneous functions such network viewing and backup. Some manufacturesuse the terms “pentaplex” and “heptaplex” to try to describe the functions. This just gets confusing.
5 Duration of Recording Time.
This will depend on the capacity of the hard drive. The more sophisticated units allow a number of user-definable options. Typical settings allow the DVR to automatically start again at the beginning and record over the oldest data or the unit can indicate that it is full and the hard disk should be changed.
By using video compression techniques it is possible to greatly extend the amount of data that can be stored on a hard drive. Similarly, by reducing the number of images per second that are recorded the capacity is increased. As very rough guideline DVRs using H.264 compression fitted with a 500GB hard drive will record about 10 days worth of high resolution images.
6 Motion Detection.
Depending on the application, it is not necessary to set the DVR to continually record. The better DVRs have a built-in motion detection system. This function is performed by electronically noting when the composition of the image changes and consequently setting the DVR to record mode. To ensure the required accuracy it should be possible to select the sensitivity of detection. An overlay mask allows areas like trees, which will move in the wind, to be blanked out of the motion detection area.
If these functions are not included then it will be necessary to use traditional PIR sensors. Fitting PIRs means a lot of cabling and extra expense so it is often more cost effective to choose a DVR with motion detection.
7 Remote set-up and viewing.
DVR with a network or LAN port can be connected to a PC or network. This will usually allow remote setup and viewing.
8 Transferring recorded images.
Choose from a number of options.
- Copy from the DVR onto a conventional VCR tape.
- Copy to USB memory stick
- Send across the LAN or Internet
- Use a network connection to a PC with a DVD burner
- Built-in DVD Writer
The latest addition of the AVTech KPD675 makes digital recorders very affordable. It offers 4 channels and multiplexer functions. It is now priced to be cheaper than time-lapsed VCRs and as such should be considered a modern replacement for a VCR. It has a selectable choice of frame rates to allow for long recording times.
It can be triggered to record manually by an alarm from a PIR or on timer or using its motion detection function.
The Concept Pro VXH264 range is a digital multiplexer and recorder. 4, 8 and 16 channel versions are available with hard disks up to 8000 GB. The high frame rates and a choice of 4 levels of quality recording (Best, High, Normal, Basic) makes it a very versatile machine.
The Jog/Shuttle control makes reviewing of images very easy.
This product is ideal for home, school, shop or business surveillance.
This product is most suited to applications that require extensive reviewing of recorded images.
PC-based Systems, Digital CCTV Systems
If you already have a PC then with the addition of a video-capture card and surveillance software you have a powerful digital system. The latest PC DVR products like the Swann USB Guardian are simple to install.
The purchase of a video capture card and software has been a very cost effective method of providing a high specification system.
However, the falling costs of standalone DVRs is challenging the cost savings.
- software allows many configurations for monitoring e.g. quad display
- records in real time, simultaneously from all cameras
- time and date stamping with motion detect
- alert wizard, send email with photo or video clip,
- mobile phone alert with voice,
- SMS alert
- audio alert
- MMS alert
- remote monitoring from another PC through Clinet Software, Internet Explorer or Pocket PC
- connect to Alarm panel
- low- cost all-in-one solution does away with the need for separate motion detect, splitters, quads or multiplexers.
Disadvantage – PC hard drive must have enough free space to record the camera pictures.
It is easy to see the benefits of the PC-based system providing you satisfy the following criteria:
Competent in installing additional hardware and software programmers.
Have good housekeeping to ensure adequate free disk space
Do not intend to use the PC for any other video capture or editing
Even with the long-recording facilities of DVRs and digital systems it is seldom desirable to continuously record. The most common method is to fit a PIR (Passive Infra Red) detector in the area to be monitored. Most people will be familiar with this concept as applied to security lighting.
The output of the PIR can be fed to a Video Remote Control module, hence the video recorder will only turn on when motion is detected. As a basic system it works well and wireless models are available that remove the need for additional cabling. As they are low-voltage devices battery life can be up to three years.
A VMD (video motion detector) is the modern alternative to the PIR. It works by analysing the video signal from the camera. When it detects changes in the signal it recognises this as movement within the camera’s picture the output being used to switch on the recording device. The sensitivity can be adjusted which will overcome the problem of bright lights being turned on causing the VMD to activate.
The more sophisticated units feature an on-screen marker or rectangle. Only movement in the rectangle will trigger the output. By resizing and repositioning the rectangles it is possible to allow for pet activity within the observation area. In the example the blue car turning into the drive will activate the recorder but the grey car passing on the road will not. It is difficult to achieve this degree of accuracy with PIRs.
Most digital and PC-based systems have VMD built in to them. This can make multi-camera digital systems very cost effective as it alleviates the need to buy motion detectors for each camera or observation area
Getting the picture signal from the camera to the monitor, recorder or TV.
The most common method used on professional installations is RG59 Coaxial cable. The centre core is the signal conductor while the outer shield protects the signal from electro-magnetic interference. It is a low-loss cable which will allow cable runs of up to 250 metres. Longer cable runs can be achieved with the use of a video amplifier.
BNC connectors are the preferred type of connector in professional CCTV installations and are recommended by IPTEC for all DIY CCTV applications. The connectors twist and lock together giving secure connection.
Professional switchers, multiplexers, monitors etc. will all use BNC connectors. If you are connecting to a domestic TV or VCR you will need to convert to phono or SCART connectors. Simple adapters are available and are supplied with many of our kits.
Increasingly popular for CCTV installations is the use of twisted pair cable, typically CAT5 or CAT6.
Twisted pair cable uses the balanced signal principle. Hence a screened conductor is not required. As cameras and DVRs will use an unbalanced signal it is necessary to convert between balanced and unbalanced. A simple device called a Balun will perform this function. A balun must be fitted at either end of a twisted pair cable.
A 4 way balun will allows 4 camera video signals to be sent down one CAT5 cable
This type of cable is more flexible than RG59 cable and its small size makes it suitable for running along the top of a skirting board or around a door frame.
We can supply a range of ready-made coax/BNC cables that are very price competitive. Alternatively, rolls of cable and either screw-on or crimp-on connectors are available.
It is advisable to keep cable runs as short as possible. Unless you are experienced in refitting a crimped BNC connector we do not recommend you cut the cable. Before ordering a camera kit measure the required cable run. BNC cables can easily be joined together with a coupler such as CCA-005.
High-quality cameras with anti-mist coating, CCD lenses will give clear, crisp, noise-free pictures. It is essential to use good quality cable if these images are not to deteriorate. For CMOS cameras the quality of cable is less important.
Increasingly popular is wireless transmission. Government regulations now allow licence-exempt systems that can typically transmit signals up to 100 metres in line of sight. This reduces to approximately 30 metres when used indoors. Simple wireless cameras will only work on one frequency so you cannot use 2 such products within 100 metres of each other. Cameras and receivers are available with 4 selectable channels making multi-camera systems feasible.
Even the small covert type of camera can be supplied with its own built-in transmitter. Alternatively, any camera can be connected to a stand-alone transmitter.
Remember that CCTV cameras require power to operate. The voltage is usually in the range 9-12V DC and this is typically derived from a small power supply plugged into the mains supply. So “wireless” does not mean totally “wire-free”. Battery operation will be measured in hours, so is not suitable for permanent installations. However, it is often easy to pick up the power for the camera in some areas such as the loft of the house.
Wireless transmission is also useful for temporary monitoring of an office or reception area. The miniature wireless cameras with battery power can be fitted to model aircraft or model trains. The receiver can be connected to a domestic camcorder to recorder the “ride-on” experience.
CCTV Monitors or TVs
The signal from a cctv camera is classed as analogue, 1 volt peak to peak into 75 Ohms. A compatible display device must be used to view the images.
The simplest method of displaying the images from the camera is by connecting to the AV input or SCART input on a television set. Most modern TVs now have these type of inputs. The AV input is usually a RCA/Phono type of connector. A simple BNC to Phono converter is all that is required to connect cameras fitted with a BNC type of connector. Most of our camera kits are supplied with BNC and Phono connectors. Alternatively, a BNC to SCART connector can be purchased as an optional extra.
Switchers, multiplexers and digital recorders generally have BNC input connectors.
If you have an older type television that does not have an AV or SCART connector it is possible to convert the camera signal to the broadcast frequency and connect through the aerial input. A small device called an RF Modulator or Wide Band Modulator provides this function.
Alternatively, for more complex or dedicated cctv system a specialist cctv monitor can be used. The tubes or screen (referred to as the CRT)used in cctv monitors are of a much higher resolution than standard TVs. The resolution is measured in TV lines and on monochrome monitors this can be up to 1000TV lines. A good quality TV will be classed at 450 TV lines. These figures are measured at the centre of the tube and will be less at the edges.
Monitors are also designed for continuous running and will contain a high-reliability long-life power supply.
If you are fitting high definition cameras with over 500 TV Lines resolution then a suitable cctv monitor is needed.
LCD screens are now available for cctv applications. The advantages of LCD monitors are:
- They are smaller and lighter than CRT monitors
- Offer the possibility of 12 volt operation
- Offer high resolution that is uniform across the screen
- The resolution does not decrease with the age of the monitor as is the case CRTs.
- The disadvantage is the cost although this is reducing rapidly.
An LCD monitor designed for connection to a PC does not usually have the required analogue inputs so check carefully before choosing this type of display.
Tips on fitting CCTV to a house.
The prospect of drilling holes through the external walls of your home to run the power and video cable for a camera may at first seems only feasible for the most accomplished DIYer.
With a little forethought it can be remarkably simple.
Positioning of cameras
Most people want to make the camera position as discreet as possible. The modern bullet-type camera is no bigger than your small finger in length and can easily be located under or on the fascia/soffit boards where the roof line meets the wall. This location also provides good shelter from wind and rain and can be shaded from excessive sunlight. The height of the camera position will give a good area of view and minimise the risk of vandalism.
However, another advantage of this location is cabling. It is usually easy to run the cables into the loft from this position. Many houses have a small ventilation gap between the roof tiles and the external wall, or a small hole may be drilled in the fascia board to gain access to the loft.
It is usually easy to pick up mains power in the loft or at least if additional cabling is required it is now internal. Wireless transmission can be used for the video signal with the receiver being placed next to the monitor or recorder (TV, VCR, PC etc.). That’s it, installation complete.
A hard-wired system can almost be as easy to install. Locate the TV aerial down-lead that may be in the loft or run down the outside of the house. It is usually possible to run the CCTV camera video cable alongside the aerial cable, which will lead directly to the TV.
A neat method of connection is to use an RF modulator. This little box changes the camera’s video output to an RF output. This means you can pipe the CCTV images down the existing TV aerial down-lead and view on the TV/VCR as if it were another channel. If the house is fitted with a TV aerial distribution system, this method of connection allows the camera pictures to be viewed on all TV sets.
Addition of DVR, Muliplexer and Switchers.
Consider placing switchers, mutiplexers or DVRs in the loft. This contains all the camera cabling in the loft with just one output cable to a monitor. It also hides away the recording device.
Consider positioning the cameras indoors. Point each camera at the exterior doors. Use a motion detector or PC-based system to activate the camera when a door is opened.
The advantage of this type of system is that you do not need a traditional burglar alarm and sensors. The output of the system can be connected to an alarm or, better still, the more sophisticated methods of dialing/SMS to your mobile phone.
This method avoids activation of the motion detector by sudden changes in light levels. Set the activation area just above the level of the cat flap to allow freedom of passage for your pets. Credits for this Article goes to : http:// www . 2seetv .co .uk (Thank You)
Thank you for seeing the CCTV Guide at IPTEC UK.