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Video Surveillance - CCTV - is the backbone of an efficient security system. It assists with detection and alarm verification

Last Updated 29 March 2022


Closed-Circuit Television (CCTV) is a system in which images are monitored and recorded for surveillance and security purposes. Though still in general us, the acronym 'CCTV' is now outdated, as this refers to the hard-wired analogue cabling approach which has generally been replaced by digital Video Surveillance Systems (VSS) that operate over TCP/IP networks. Analogue CCTV systems are still available and, if it suitable for your requirements, can still provide a viable and cost effective option, particularly for small installations.

For simplicity, CCTV will be used throughout this article.

It is important to understand that CCTV will not prevent criminal action, but may deter, or detect a criminal action. CCTV should always be used alongside other security measures to provide a coordinated security solution.

Site CCTV systems are generally deployed to achieve the following functions:

  • Deter an attempted intrusion by causing an adversary to reconsider the site due to enhanced probability of detection.
  • Detect an attempted intrusion to the site using video analytics.
  • Verify and further investigate and alarm event from a Perimeter Intruder Detection System (PIDS).
  • Tracking of an intruder when they have breached the perimeter.
  • Recording of digital image evidence suitable for use in an investigation or court proceedings (see guidance below for retention policies).
  • Overlooking Access Control area

The term Video Surveillance Systems covers a wide range of technology, which can include:

  • Visible band camera sensors.
  • Infrared band camera sensors.
  • Thermal imaging sensors
  • Video analytics and content analysis.
  • Static cameras with fixed/varifocal lens.
  • Pan, Tilt, Zoom (PTZ) cameras.
  • Panoramic/360*/180* cameras.

The video outlines how a video surveillance system - CCTV - may be used in a layered security solution.

View Video Transcript

CCTV, or closed circuit television, is an essential technology for any site that's looking to increase its security level. CCTV should be deployed around the site's perimeter fencing to cover the area around your site, within your site borders, or within the buildings themselves.  

CCTV cameras should be monitored live by an operator in a security control room, SCR. In this central hub, footage can also be recorded for evidential purposes.  

When monitoring live, an operator can only be expected to detect an intruder on screen if they are more than 10% the height of the screen. Due to the restrictions of the human eye an intruder that appears at a size smaller than this is unlikely to be spotted. Whilst a higher definition picture such as 4, 6, or 8K, does make the image clearer it does not make the intruder appear larger on the screen.  

When deploying CCTV around the perimeter of a site there are some basic rules that must be followed. Perimeter CCTV needs to be fixed view cameras that overlap in a heel-to-toe configuration allowing for all of the outside areas to be covered with no gaps in coverage.  

Perimeter lighting is required to support visible band cameras. It must be of uniform height and spacing, and set back far enough away from the fence so that it does not provide a climbing aid to intruders. The minimum light level should be three lux. This creates an area of light in which most CCTV cameras will be able to pick up intruders. Good perimeter lighting also enables a response team to operate in the event of an intruder or a raised alarm, as they can move around the site unencumbered by poor visibility.  

Most modern CCTV cameras come equipped with infrared or IR capabilities. These will automatically activate when a preset level of light is reached. As the light level lowers the camera switches to its IR function. Using IR technology can negate the need for perimeter lighting. However, your response force will still need site lighting in order to operate effectively.  

CCTV can also be used to provide additional coverage of vulnerable areas or access points within your site's perimeter. Fixed cameras should be supported by Pan Tilt Zoom, or PTZ cameras, to offer a further verification capability and to aid in the tracking of any intruders. Cameras are used to verify any triggered alarms and can also be used to track any intruders across your site.  

Tracking intruders using CCTV can be automatic or manual. Automatic tracking is currently very difficult to achieve on all but the highest tech systems.  

Manual tracking requires skill and good site knowledge on the part of the control room operator. It's unlikely that every part of your site will be covered by CCTV, and a fast moving intruder could be hard to follow. Training on how to operate the systems and familiarity with the camera locations and site layout is important for all SCR staff. Because of this internal CCTV is likely to be deployed in public areas, such as the main entrance and reception, or at other access points, stairwells, and corridors, or areas of particularly high security that have restricted access.  

However, if your operational requirement identifies a need to install CCTV in offices or any other less public location, this is permissible as long as the current data protection rules are observed.  

If a camera is installed with a specific purpose in mind, such as monitoring who accesses a server room, then 50% or above screen height should be adhered to. This is to make sure that identification of those captured on the camera is indeed possible. Having internal CCTV present on site greatly increases the ability of control room staff to identify and track any intruders who gain access to your buildings.  

CCTV is the backbone of any site security and should be deployed accordingly. A combination of perimeter, internal, fixed and Pan Tilt Zoom cameras should be used in order to secure your site. But whatever the reason for deploying CCTV on site, CCTV is only as good as the people who are using it.  

Training on the technology and familiarity with the site are needed to operate a CCTV system correctly. CCTV should be deployed in conjunction with other security measures, such as automatic access control and intruder detection systems in order to build effective security across all of your site. 

Subtitled version

Active Infrared Cameras

A camera with active infrared lighting is designed for low light environments and uses integral infrared LEDs to spread IR light over the scene. IR light is not visible to the human eye. This IR light is reflected to the camera sensor and interpreted to generate a usable image within the Greyscale (black and white) colour spectrum. The image produced within the IR lighting parameters, will not provide colour definition, for example - a red jacket will appear dark grey or black. The viewed image is not black and white as per the normal understanding.

The monochrome (black and white) image shows the tree as a darker shade and the person wearing a dark coat


The Infra-red image shows the same tree as a light colour and the person in a lighter coat


In many cases, the integral IR LEDs within the camera will not be adequate to illuminate the scene sufficiently. In this case, supplementary IR lighting should be installed to assist the camera in achieving a good quality image.

Active infrared cameras are useful where the operator needs to see more detail in low light situations, such as identifying or recognising a person.

Thermal Imaging

Thermal imaging camera technology uses mid to long wavelength IR energy. Although the term camera is often used with thermal imaging, the devices are, in fact, sensors. Thermal imagers are passive and will only sense differences in heat, not light as with standard cameras. These heat signatures are then displayed within the image. This type of camera technology is primarily used for detection and is ideal for use on a site perimeter where the focus is detection of attempted intrusion.

As thermal imaging sensor technology operates in longer infrared wavelength regions than active IR, they do not see reflected light, and are therefore not affected by rain, fog, smoke, haze and dust. This makes them highly effective in perimeter monitoring over long ranges.

Thermal cameras monitoring a perimeter should be placed so their fields of view run parallel to the perimeter and perpendicular to the movement of potential intruders to ensure targets move horizontally across a camera's field of view. This design approach results in the highest probability of detection and the lowest rate of false alarms.

Thermal imagers can be used to determine the class (vehicle, person, animal) of a target, but will not allow an operator to identify the person, or the colour of a vehicle.

It is important to note that thermal imagers cannot see through glass, as the glass acts as a mirror for infrared radiation.

This thermal image shows a person using binoculars. Note that the partially rolled down window allows the background to be seen through the open portion only. The glass blocks the image. The person is clearly visible and can be seen to be wearing equipment at their waist


This is the same image captured using a visible band camera. The person is not visible at all, and the background is very dark. However, the car's interior light allows much greater definition of the car door


Video Analytics

Video analytics is a technology that processes video signal using specific algorithms in order to perform a task or function. They are a way of using machines and software to understand the scene in real time or in retrospect. The primary aim of video analytics is to make detection more accurate and reduce the burden on the operator.

There are many uses of video analytics which include, but are not limited to:

  • Identifying items left behind
  • Sterile zone detection
  • Anomaly detection
  • Automatic number plate recognition
  • Tracking

Video analytics may also be used retrospectively, for example by police when reviewing CCTV imagery following an incident.

NPSA currently evaluate 4 video analytic system types:

  • Sterile Zone
  • Abandoned Baggage
  • Doorway Surveillance
  • Parked Vehicle

The Catalogue of Security Equipment contains those that have successfully passed evaluation.

Currently evaluations are carried out on behalf of NPSA by the Building Research Establishment (BRE). Details are available on the BRE Website.


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