A video Surveillance system is sometimes known as a Closed Circuit Television System (CCTV). A CCTV system is an on premises system consisting of a television camera, video monitor, and a transmission medium (Cable, fiber or wireless) connecting the two. It is used to monitor the premises.
What are Common Applications for CCTV?
Probably the most widely known use of CCTV is in security systems and such applications as retail shops, banks, government establishments, etc. The true scope for applications is almost unlimited. Some examples are listed below.
- Observe and record theft or violence by overtly monitoring retail floor space, office buildings, building perimeters, warehouses, loading docks and parking garages.
- Monitor sensitive areas where infrequent activities occur (i.e. confidential records, safes, etc…)
- Monitor point-of-sale exceptions (cash register voids, over-rings, etc…) reducing cashier theft.
- Observe and record shoplifting activities. “Walk a beat” by programming a moving camera to pan, tilt, and zoom within a defined pattern. Perform covert surveillance (where legally applicable)
- Integrate with access control systems to provide video of persons entering and leaving the premises
- Complement asset tracking systems to provide video when a tagged asset leaves the premises. Loss prevention is the #1 concern for retailers. Inventory “shrinkage” – through a combination of employee theft, shoplifting, vendor fraud and administrative error – is one of the fastest growing expenses in retailing today. According to a National Retail Security Survey, inventory shrinkage cost U.S. retailers more than $32 billion in 2000.
- Monitor Financial Institutions- According to FBI data reported by the American Bankers Association – Bank robberies in the United Sates totaled 8,259 in 2001. Washington State alone averaged a robbery a day, and claimed losses of $1.1 million in 2001. Account, check, identity and internal fraud is also a growing problem for all financial institutions.
- Allow operators to see into areas where the environment is hazardous to life or health
- Monitor potential accident areas.
- Monitor residence halls, common areas, or high-risk areas to ensure safety of an educational institution’s students and faculty.
- Help reduce the severity of some incidents by the timely dispatch of police, fire, and emergency personnel.
- Monitoring traffic on a highway or bridge.
- Management Tools
- Train employees, check stock on store shelves and monitor retail sales floor coverage, production lines, etc.
- Demonstrate management’s due diligence towards protecting employees, clients, and visitors, and perhaps avert or minimize litigation and negative publicity
- Document video images on magnetic tape or optical hard drives to record events. This information may be reviewed and later presented as evidence for prosecution of criminals, or as a training tool.
Analog or Digital?
In the past, all CCTV Cameras were attached to a Multiplexer (A device which can split multiple camera pictures onto 1 CCTV Monitor). The Multiplexer then sends the camera images to a Time Lapse Video Player (A device which unlike a normal VCR, can prolong video recording for up to 960 hours on a 3 hour tape by missing out frames). This method is still used today for simple CCTV installations but the quality of recording is usually very low (1 Frame Per 12.8 Seconds). Nowadays, most CCTV systems are Digital. Digital Surveillance uses current PC technology to digitize camera images, compress them into a PC friendly format and store them on a PC’s Hard Disk Drive. CCTV pictures are stored on a computer Hard Drive which means you can save lots of CCTV footage and access them very easily and quickly. By using a PC to store CCTV footage, you are able to take advantage of today’s powerful PC technology and capture CCTV images in High Resolution and Real Time.
Color vs. Black & White?
Color cameras generally require higher levels of lighting than their monochromatic (B/W) counterparts. Color produces a more natural, richer image than black and white and may keep the operator’s interest for longer periods of time. It also makes it easier to detect subjects. For example, with a color system a viewer can easily distinguish a red car from a green one, while on a black and white system both cars would appear a similar shade of grey. In retail applications, a color system can help security personnel identify shoplifters and their clothing more easily and convincingly. Color accuracy is extremely important in gambling casinos, where hundreds of dollars can ride on the ability to recognize the difference between maroon chips and red ones.
While the use of color cameras is growing, black and white cameras continue to offer some distinct advantages. Black and white cameras are better suited for extremely low light situations. The ability to capture good quality images in low light situations increase the cost of both black and white and color cameras. Before purchasing cameras, you should consider the crossover points between lighting costs and camera costs. It’s possible that low-light cameras will cost less than paying to increase the lighting level of a parking lot
The starting point for any CCTV system must be the camera. The camera creates the picture that will be transmitted to the control position. Apart from special designs CCTV cameras are not fitted with a lens. The lens must be provided separately and screwed onto the front of the camera. There is a standard screw thread for CCTV cameras, although there are different types of lens mounts.
Cameras come is a variety of shapes and sizes. Some are mounted to be visible for ease of installation and deterrent effect. Others are concealed to enhance detection.
Versatile surveillance cameras are designed to suit almost any application requiring a view of a given location. With the broad selection of available lenses, cameras can be configured to cover broad areas such as parking lots or waiting areas, or tighter, up-close views of entrances and access points.
The lens is an optical device for focusing a desired scene onto the imaging device in a CCTV camera.
Selecting the most appropriate lens can be a complex task because lenses have a number of characteristics that must be considered to match a particular requirement with the best lens for the job.
- Fixed focus lenses are the simplest type of Lens. The preset focal length means a precise calculation is required to select the lens most suitable for the location, based on the desired size of viewing area and its distance from the camera. Typical Lens sizes offer either 30 degree view – narrow to allow more detail at distance – or 60 degree, which offers a much wider angle of view.
- Varifocal lenses offer more flexibility, allowing the field of view to be adjusted manually to get the view required rather than the limited by the constraints of the fixed Lens.
- Zoom lenses are the most complex type, offering the widest choice of associated features and technologies. Zoom lenses can be remotely adjusted to allow variation of the focal length. This means that a single lens can be used to view a wide area until an intruder is detected whereupon it can be zoomed into capture facial details. Generally Zoom lenses incorporate an Auto Iris mechanism to permit 24-hour usage.
Lenses are also categorized according to size format. As Camera technology has advanced, sensor chips have reduced in size, requiring lenses to produce smaller images at the focal point. This has made smaller lenses possible (less glass resulting in less physical size and weight) although the requirements of precision manufacturing doesn’t permit a proportional price reduction – the component materials of a Lens being a very small proportion of the overall manufacturing cost. The quoted format of the Lens (1″, 1/2″, 1/3″ and now even 1/4″) is derived from the ratio of diameter to the viewing image produced. Whilst it is often most cost effective to match the lens format to the camera sensor size, it is possible to use a larger lens on a smaller size camera since the image only needs to be at least as large as the sensor. Using a larger lens can often be advantageous, since it offers greater depth of field (the range of distances from the lens before objects are too close or too far away to be in focus). Larger lenses also mean that the area of the image that is used is taken entirely from the central, flatter part of the lens causing much less corner distortion and better focus.
A lens with a manually adjusted iris can be used in indoor applications, where the lighting level is controllable and consistent. Both manual and fixed iris lenses can be used with cameras which offer a feature known as ‘electronic iris’ – an on-board technology to effectively reduce the sensor exposure to compensate for the lack of iris control. This can be cost effective, but does not provide the increased depth of field offered by a correctly sized iris.
For external use (where conditions generally vary the most), an automatic iris lens offers the best performance, as the iris aperture automatically adjusts to create the optimum image by monitoring the output signal from the camera. There are a number of different lens types offering this method of iris control. The original design for automatic iris lenses was wholly self-contained, with the image analysing technology built into the lens and an iris that was adjusted by servomotors.
The final lens characteristic to take account of is the light-gathering speed of the lens-expressed as an f-stop number. This literally measures the amount of light captured by the lens in a given period of time; the lower the f-stop range, the more light that can be transmitted.
The monitor receives the transmitted electronic video signal from the camera from the paints it across a monitor to display an image to a viewer. Although similar in function to a TV, a CCTV monitor provides higher lines of resolution (better picture quality) and accepts only video signals rather than RF/antenna signals.
Lines of resolution refers to the total number of horizontal lines the camera or monitor is able to reproduce. The more lines on a screen, the better or sharper the video picture will appear. CCTV monitors can provide up to 1000 lines of resolution compared to an average of 300 lines provided by some TV sets.
Several factors can affect the monitoring function: Size of the monitor, its positioning and angle relative to the viewer, and the quality (resolution) of the monitor itself. In all cases, sufficient growth must be factored into any console design. It’s also important to note that all monitors generate heat. Whether on a table or enclosed in a console, be sure to provide adequate ventilation and air-conditioning.
Most CCTV systems use both dedicated monitors and call-up (switchable) monitors. A dedicated monitor displays the video from only one camera. A call-up or switchable monitor enables the operator to call or switch different or multiple cameras into view. Generally call-up/switchable monitors are larger than dedicated monitors and give operators the ability to view multiple images simultaneously (multiplexed) as well as scrutinize the camera image more closely.
Time-lapse VCRs have been used as a storage medium for some time.VCRs have some drawbacks including, introduction of noise, wear and tear and the simple requirement that the tape needs to be rewound to access information. In a practical situation the reviewing of tapes to secure the important face shot” or “scene of crime” can involve long and tedious work.
Digital Video Recorder (or DVR) uses a computer hard disk memory to store images and are excellent at reproducing high quality images with little noise or picture degradation and are extremely useful in calling up an alarmed picture. In addition to they may offer a number of additional features:.
- Ability to view and control the system from computers around the world.
- Interconnectivity to Computer networks.
- Motion Detection for setting alarm events and immediate retrieval.
- Ability to go direct to a time or incident without the need to search through hours of videotape.
PC Based Digital Video Surveillance Capture Cards use a card installed in computer along software to allow you to view your CCTV Cameras, search through previously recorded footage, backup footage to CD/DVD, control pan tilt and zoom cameras either on the PC system or remotely and much much more.
CCTV cameras can be fixed or have pan, tilt, and zoom (PTZ) capabilities. Fixed cameras are mounted on a fixed bracket and cannot move in response to operator commands. PTZ cameras are motor driven and can pan left or right, tilt up or down, and use the lens to zoom in and out. A camera housing protects the camera and lens from vandalism and the environment. It also can enhance the appearance of the camera installation and conceal the equipment from the casual observer. All outdoor cameras require a housing of some type. Protection from cold, heat, dust, dirt, or other elements is needed to ensure optimal performance and extend the life of the camera. Broadly categorized into internal and external usage, pan/tilts are normally selected on the basis of the maximum load they can take.
The purpose of the transmission medium is to carry the video signal from the camera to the monitor. Today, many video transmission methods exist: coaxial cable, fiber optic, phone lines, microwave, and radio frequency. Due to varying application technologies in use within the same CCTV system. The choice of transmission mediums depends on factors such as distance, environments, cost and facility layout. In addition nearly all methods of transmission suffer from various forms of interference or loss. The essence of good design is to minimize this impact. Examples of current video transmission include:
- Coaxial Cable– A coaxial cable is one that provides a continuous physical connection – or closed circuit – between the camera and the monitor. The cable is shielded to minimize interference from any nearby electronic devices or electrical wires. Copper braided coaxial cable is recommended to maximize conductivity and minimize potential interference. For traditional CCTV systems, as well as many applications today, this is the most common economical method of signal transmission over relatively short distances (few hundred feet).
- Fiber Optics– Fiber optic technology changes an electronic video signal into pulsed or laser light and injects (transmits) it into one end of a glass rod (the fiber optic cable). At the other end, a receiver translates the pulsed light back into an electronic signal capable of being displayed on a monitor. The transmission is unaffected by any kind of interference, water in conduit or high voltage being run in the same conduit. Fiber optic capable have a large signal capacity (bandwidth) and no possibility of a spark from a broken fiber. Hence, there is no fire hazard to a facility even in the most flammable environment. Fiber optics offers a cost-effective method of sending large transmissions over long distances.
- Telephone line– A telephone line is a standard twisted pair of wires that can transmit the image for distances up to one kilometer without signal boosting. The dedicated line connects the transmitter (camera end) with a receiver (monitor end). Through the use of specialized transmission and receiver equipment, it is possible to use standard telephone lines for video signal transmission (RSM).
- Microwave- If already in place, microwave can be a very efficient and cost-effective method of delivering black and white or color video. Microwave turns the video and data signals into high radio frequency signals and transmits them from one point to another via free air and space. A receiver then converts the transmission back into the video and data signals and displays the scene on a monitor. Good quality transmission can be achieved over a line of sight path. Microwave technology offers a large bandwidth to carry video, however it can be affected by environmental conditions. It is a practical option when a wire path between the camera and the monitor locations cannot be established or is prohibitively expensive. Microwave transmissions are regulated by the FCC and a license is required.
- Radio Frequency- Radio frequency (RF) is a reliable, but short distance, line of sight video transmission technology. It is becoming increasingly popular where hardwiring methods are easier impossible or impractical, and has been used successfully to reduce cabling costs even within large buildings. Environment conditions or other RF in the area can affect it.
- Network/IP Cameras– Cameras can be connected Ethernet IP networks with a built-in 10Base-T/100Base-TX Ethernet connection to allow you to monitor and control the units via an IP-protocol network from a networked PC. The cameras can operate on multiple protocols, including TCP/IP, HTTP, FTP, SMTP, DHCP, and others, depending on model. This flexibility allows you to utilize existing LANs, WANs, or Virtual Private Networks – and even the public Internet – to monitor remote locations without installing standalone video networks.
A video switcher enables different cameras to be switched to call-up monitors. In a smaller, cost-conscious applications, a manual switcher allows users to select the camera they want to see by pressing the appropriate button. The most popular type of switcher, a sequential switcher, contains circuitry that will switch one camera to another automatically. The operator can set the length of time (dwell time) that a scene remains on the monitor before sequencing automatically to the next camera. This allows operators to keep tabs on numerous cameras with only one monitor.
A matrix switcher is a more complex design enabling the user to switch any video signal to any call-up monitor in a large-scale system. They normally incorporate pan, tilt and zoom control and other features such as preset and alarm inputs and outputs.
Unlike conventional recording systems, a video multiplexers collects full-screen pictures from several cameras and displays them simultaneously on a monitor. Operators have the option of displaying any camera full screen or multiple cameras in reduced sizes. Multiplexers also can record all cameras in the system onto a single videotape or DVR. The cameras are recorded sequentially at a high rate of speed. As mentioned earlier, a standard video signal is comprised of 30 separate frames each second. In a video system containing 15 cameras, the multiplexers selects two frames from each camera and records them to a single videotape. The result is an effective frame rate of 2 frames per second, instead of the standard 30.
Most multiplexers today contain motion detection features that enables the system to record more frames of video from cameras showing motion than from those not showing any motion. The multiplexer does this by reallocating frames from one camera to another as needed. The net result is higher quality recordings of scenes that are more likely to be important to security personnel.
The main feature of a quad is the ability to compress images from four separate cameras and simultaneously display them on a single monitor screen. When four cameras are displayed, each occupies a quarter of the screen. A single camera can be selected and displayed full screen as well. Unlike multiplexers recording, quad recordings yield only what appears on the monitor at the time of recording. If the VCR is recording in quad mode, then the playback is in quad mode.
Continuous still cameras, also known as automatic cameras, take pictures at preset intervals and may be turned on and off by a timing mechanism during certain hours.
Sequence cameras take photos only when activated. A push button, connection with a holdup system or connection to a motion sensor or alarm may be used to activate the camera.
Both types of cameras usually use film cartridges which are removed to be developed after the camera is activated.
How to Choose a CCTV Camera?
Choosing the correct CCTV Camera for your surveillance system is very important. The CCTV Camera, together with a CCTV Lens, uses a CCD (Charge Coupled Device) sensor that captures the image and turns it into an electric signal which can be sent to a monitor or surveillance system.
You need to decide the following when choosing a CCTV camera & lens:
- The environment the camera will be in i.e. Will the camera be situated: Indoors? Outdoors?
- The amount of light or variable light conditions for the camera i.e. Will the camera have to record in low-light conditions?
- The Field of View required for the camera. How wide or narrow an angle you require. The distance within which objects in a picture are in focus.
- The Focal Length- How far away objects you wish to record will be from the camera
- Your budget