Closed Circuit Television, also known by the acronym CCTV, is a private or closed video system where viewing of the video is restricted to a specific group of individuals. Systems can range in size from being within a single building, to a complex of buildings, to large campuses and city centers, and can even span across a continent. Such monitoring of areas and/or activities may be used for security, safety, industrial, or private purposes. The visual images created by a CCTV system may be viewed while an event is happening, or recorded for ‘after-the-fact’ review either on-site or off-site. Review is done via the use of VHS videotapes, CD, DVD, and/or other such tape or computer based mediums. Such reviews of prerecorded visual information may also be done ‘remotely’ through the use of telephone lines, fiber optics, microwave, the internet, and/or a host of other such transmission methods according to the design and complexity of the CCTV system.

CCTV is a visual surveillance technology designed for monitoring a variety of environments and activities all at the same time. CCTV systems typically involve a dedicated communications link between cameras in the field and monitors at one or more control centers. Systems can be made up of technically mature analog cameras and image storage devices, or newly developed digital cameras and image storage devices, or a mix of the two technologies.

CCTV systems may provide real-time, time-lapse, event, or digitally recorded surveillance information to help in detecting, responding to, investigating and providing evidence for security, safety and related incidents. A CCTV system may also be used to prevent security breaches by allowing security personnel to monitor access control systems at entry points to secure areas.

A CCTV system usually involves a linked system of cameras able to be viewed and operated from a series of control rooms and/or a central point of operation. Cameras come in many configurations, but can be classified under two general categories; stationary and moving.
Stationary cameras are pointed at a specific scene of interest, such as a hallway, and broadcast that one scene to the control site 100% of the time. Stationary cameras can be adjusted to compensate for the specific lighting conditions of that scene. Stationary cameras can be fully exposed, or contained within a large variety of enclosures designed to meet the specific requirements of that site, such as discreteness or vandal resistance.

Moving cameras, commonly called PTZ (for pan, tilt, zoom) allow a system operator to move the camera by remote control to follow an object of interest, such as a person or a car, over a large area of interest. This is typically done by use of a joystick in the control center that provides side to side (pan), up and down (tilt) and zoom control. PTZ devices can also be programmed to move in user-defined PTZ sequences to provide general surveillance of areas of interest. PTZ devices can be further programmed to automatically move to areas of interest, such as when a door or gate opens, or when motion is detected. Because the camera can be aimed at scenes with different lighting conditions, these cameras typically have many automated adjustments, such as auto focus and auto iris to keep the image optimized for accurate viewing.

Effectiveness

CCTV systems have proven to be essential tools in most any surveillance and security application. Just a partial list of applications includes banking, retail, hospital, traffic management, and city centers. In all of these applications, video cameras are used as visual tools of the security staff or security design. CCTV systems greatly increase the geographic areas that can be covered by one security professional. No longer are long, arduous guard tours needed, requiring an individual to walk or drive long distances to provide security. And once an event has transpired, video can be used for investigation and evidence in criminal and civil liability cases. The installation of CCTV security systems thus provides a large deterrence to unlawful activity, and provides a strong sense of security to patrons of facilities that use CCTV. Due to great advances in the controlling or manipulating interfacing systems, video systems can be automated to great degrees.

Advancements in ‘video motion’ detection has given the system designer the ability to use video cameras in place of fence alarms, outdoor microwave motion detection systems, outdoor modulated infrared photo beam systems, leaky coaxial motion detection systems and more with higher degrees of effectiveness and accuracy. The video motion system may be programmed to do the following: detect motion when it is moving in a specific direction; detect motion of objects of specific sizes; detect motion within three dimensional areas; etcetera. Additionally, cameras on pan/tilt systems can be designed to automatically follow or track individuals or targets throughout their visual range.

Video non-motion detection systems may be designed into a CCTV system to detect the lack of motion of objects. This allows a large, open area to be view for objects left behind. Such technology also allows guards to concentrate on other facets of security.

To protect the privacy of individuals, advanced CCTV systems are available with many features designed specifically for this need. PTZ camera systems can be programmed so that specific areas of the viewed scene are overlaid with opaque shapes to prevent viewing of non-public areas, such as into homes through their windows. In addition, control systems can be configured so that only specific security professionals can view video from specific cameras that may be viewing “sensitive” scenes.

The net result or effectiveness of any/all CCTV systems is determined by the sophistication of the interfacing modules and to the extent that the system is designed as a visual tool for the security team.

Performance factors

In modern video systems, it is very possible to have hundreds or even thousands of cameras. Therefore the idea that an individual or group of individuals would be able to ‘monitor’ or ‘view’ the overall system becomes inconceivable. For this reason, modern designs try to obtain systems that are “view free” and “hands free”.

View free video is accomplished through recording “events” versus continuous recording of empty areas. Event recording is accomplished through various forms of ‘alarm interfacing’. I.e.; A magnetic switch may be added to a door to trigger the camera’s assigned recording device to record the image from the camera in the ‘event’ that the door is opened. This saves video storage room (tape, disc, or hard-drive) as well as precious time reviewing video information.

Hands free video systems are also accomplished through the use of various types of electronic, programmable triggers. I.e.; the door opened, the video recorder started recording automatically and continued until the door closed. This action frees the guard from being needed to control the function of the system versus responding to the situation.

Many systems today have the ability to be ‘pre-positioned programmed’. This gives the designer or operator the ability to set up multiple view points in advance of need. In this way, cameras on pan/tilt systems (either mechanical or digital) can be programmed to automatically move from point to point in a pre-determined route. Additionally, alarm points (such as the door in the previous paragraph) can be added to automatically move the camera’s view to the alarmed position when needed. Once again the operator is freed up to respond to versus operate the system.What are the Basic Components of a CCTV System?

All CCTV systems consist of the following equipment:

1. Camera
The modern CCTV video camera is available in both monochrome (black and white) and color. Modern cameras use a CCD (Charged Couple Device) imaging device to create an image. Color cameras have the advantage of providing color information to describe a subject. Monochrome cameras have the advantage of higher nighttime sensitivity.

2. Monitor
A monitor is very similar to a standard television set, however, it lacks the electronics to pick up regular television. Monitors are available in both monochrome and color versions. CCTV monitors usually have up to two or three times the horizontal resolution of a regular television and so reproduce an image with superior quality or resolution. In digital systems, standard SVGA monitors may also be used to view video.

CCTV systems may also have any one or combination of the following equipment:

1. Recording / Visual Storage Systems
Recording of visual images and/or events is paramount to the CCTV system in security. Such recorded events are used for multiples of reasons ranging from evidence to records of actions. With the advancements of technology, several different methods of recording information have been made available over the past years.

A. Time-lapse Recorders: 

This style of recording allows time to lapse between taking individual images or pictures. “Real time” recording is 30 pictures (NTSC, 25 pictures PAL) per second. By allowing time to lapse between images, fewer images are recorded per second and less storage medium (video tape, disc, hard drive, etcetera) is required for ‘recording’ the action. Ie; 240 hour mode allows 10 days of continuous recording to be stored on a single 2 hour cassette. This is because 1 picture is recorded each 2 seconds versus the normal 60 images in the same amount of time. Playback of the images is directly reflected by the lack of continuity … therefore, the total length of the time allowed to lapse will be determined by application.

B. Event recorders:  

This style of recording allows specific events to be recorded with little or no loss time from the point of trigger to the point of recording. In this way, less storage medium is required as compared to full term recording of dead or inactive areas. Determination of length of events, number of events and other such criteria is paramount to determining when to change videotapes.

C. 24 hour / 72 hour high density (HD) recorders: 

These units were developed to work in specific applications with multiplexing switchers. By changing the method of sweeping or placing the video information on the videotape, three times the normal amount of information can be recorded per inch of videotape. In this way, video multiplexers were made more effective. Ie; in the 24 hour mode, a time-lapse recorder records 5 images per second. Using an eight camera multiplexer, the time-lapse recorder stores an average of .625 images per camera per second. A 24 hr. HD recorder stores 15 images in the same space. Therefore, using an eight camera multiplexing system the recorder stores 1.87 images per camera per second.

D. Digital Storage systems (DSS/DVR): 

These systems range in size from stand-alone units that use event based or time-lapse recording on floppy disks or hard drives to huge system units that record continuously. Digital storage systems have the advantage of being able quickly search though large amounts of video, based on an event, time of day, or camera. In addition, the amount of storage may be optimized with the ability to program the record rate for each camera, the most critical cameras having the most recorded video.

2. Video Transmission

How the video signal is transmitted from the camera to the control point is usually determined by the most effective means available. Not all applications can use or should use the same method for transmitting the video image.

A. Coaxial cable: 

Coax is the most common method of transmitting the signal. It provides very high bandwidth and assures the transmission of high quality video within its distance parameters. It is restricted, primarily by distance and the quality of the cable used.

B. Twisted pair:  

This method requires the use of a pair of twisted wires to carry the video image. Since the redevelopment and upgrade of twisted pair technology in the early 1990s, twisted pair transmission technology is fast outpacing coaxial cable.

C. Fiber Optics:  

Fiber is clearly the best method for transmitting video over longer distances. When using fiber, the video signal is electronically changed into pulsed light. This light is then injected to a fiber. At the other end of the fiber, the pulsed light is changed back into an electronic signal. The advantages of fiber are that the video signal can be sent over long distances without significant degradation.

D. Microwave:  

This is the use of microwave radio waves to transmit the video signal across areas ranging from 200 meters (short range) to ten miles (long range). In the US, microwave systems over 100 mili-watts must be licensed by the FCC in advance of installation. Microwave systems must have an open line-of-sight between the transmitter and the receiver.

E. WAN Digital transmission: 

The introduction of the internet in the mid 1990’s opened the door for wide area control and monitoring systems within the CCTV industry. Used by large corporate entities, a single control point is now able to monitor activities at multiple points around the world. Wide area networks can be built using private network communications paths, or use the Internet as the communications medium. Major disadvantages of intranet transmission include bandwidth restrictions and potential interference or security breaches from hackers.

3. Video Switching Systems
If a CCTV system has more than one camera, there must be a way to control each video signal going to the recording device and the monitor. As do the applications and designs of CCTV systems, video switching units come in a wide variety of styles.

A. Sequential Switchers: 

Units that provide full screen images, one camera after another, typically for 3 to 5 seconds each. When one camera is on the screen the other cameras are not being recorded. The major drawback is the time loss factor between camera images recorded. Ie; in an eight camera system, at 5 seconds of delay between images, there is 35 seconds of time loss from the point that the system switches from camera #1 to the point that the system returns to camera #1. Video sequential swithers also have severe limitations in controlling multiple PTZ devices.

B. Quads:  

Units that were originally designed to promote visual verification of up to four video images on a signal screen. Designed to display four images of 150 horizontal line resolution at a time, these units were not designed to be used for recording of the images in higher resolution applications.

C. Multiplexers:  

These units are high-speed switchers that provide full-screen images from up to 16 cameras. Multiplexers can playback everything that happened on any one camera without interference from the other cameras on the system.

D. Matrix Switchers: 

These units are designed to ‘manage’ large numbers of cameras and monitors. Usually used in systems of minimum 12 cameras, they are able to expand into the thousands of camera inputs and hundreds of monitor outputs. Each camera input and monitor outputs are completely independently programmable. Ie; Monitor #1 will display all of the odd camera #s in a sequential mode. Monitor #2 will display all video alarms from the odd numbered cameras only. Monitor #3 will display camera image number 4 only. Matrix switching units have many other programmable features such interfacing to access control systems, user log-ins, and PTZ control.

What is Resolution?

What are Remote Transmission and Alarm Verification?

Where is CCTV Being Used?