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.

 Cameras

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. Please contact 2SEETV with your requirements.
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 in the 2seetv store 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.

 Camera resolution

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.

 Indoor/Outdoor Cameras

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 2seetv.

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.

 Color vs. Black & White (Monochrome)

The amount of light available at any time on the scene, and its constancy in time will influence the choice of Black and White vs. Color.
Color Surveillance-cameras generally require a higher level of lighting than black & white.

Color produces a more natural, richer image than black & white. If the scene has to be monitored constantly, color may keep the observer's attention for longer periods of time. It may also make it easier to detect suspect persons. With a color system a viewer can easily distinguish colors, while on a black & white system any color would appear a similar shade of gray.

While the use of color cameras is growing, black & white Surveillance-cameras continue to offer some unique advantages because they are better suited for extremely low light situations and for IR (Infrared) illuminated scenes. At low illumination levels most color images look anyway like black & white on monitors.

Capturing good quality images in low light increases the cost of both black & white and color Surveillance-cameras. It is possible, and has to be determined, if low-light cameras (that is with increased sensitivity, lower lux rating) will cost less than the expense to increase and maintain lighting.

Day/Night color Surveillance-cameras are available that see colors during the day in full light, but switch to black and white for clearer pictures after dark.

 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.

 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, 9 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 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 9 channel DVR will    give a 3 by 3 matrix to display all channels. All other functions of multiplexers like alarms, time and date    stamping should be available.

 3 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. It is preferable that the disks are mounted in slide out drawers to aid replacement.
  

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. The Concept DMR4-MPEG-4 product has a recording capacity of up to 6000 hours.

 4 Maximum Frame Rate. This is maximum number of frames or images that can be recorded in a second.     Traditional cctv VCRs used low frame rates to achieve reasonable recording times from VHS tape. This     resulted in jerky images. DVRs give the user the flexibility to choose the desired resolution.
    If your application is simply to observe a person or vehicle entering an area then a frame rate as low as     1per second is all that is required. To observe fine detail of somebody taking an item and putting it in     their pocket then higher frame rates are needed.

The most common DVR specification is 25 frames per second. DVRs with higher rates, 50 or 100 frames per second are only specified for very high end system specifications.
Check the quoted frame refers to the British PAL system. Some products quote 25fps for NTSC and 18fps for PAL.

Some specifications can be confusing in that they quote fields per seconds 50 fields per second = 25 frames    per second.

 5 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, typically at     256 levels

If this function is 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.

 6 Remote set-up and viewing. The provision of an RS232 or RS485 interface allows the DVR to be     connected to a PC and setup by the use of the keyboard.
    To connect to a LAN or the Internet a web server is required. This can either be an optional extra or is     already built-in.

 7 Transferring recorded images. Choose from a number of options.

   a) Remove hard disk and send to the police or reviewer.
   b) Copy from the DVR onto a conventional VCR tape.
   c) Send across the LAN or Internet
   d) Use a network connection to a PC with a DVD burner
   e) Built-in CD Writer