Pace Book 3

Security PACE Book 3 - CCTV Systems and Control Concepts

Course Introduction

CCTV Systems and Control Concepts CCTV System Definition Cameras Lens Technology Light Considerations Monitors Transmission Mediums CCTV Accessories Signal Management

Security PACE Book 3 - CCTV Systems and Control Concepts CCTV Systems and Control Concepts is Book Three in this PACE series on Security Basics. It was designed to cover the basic concepts, technologies and applications of CCTV systems.

Learning Objective After completing this PACE Book, you should be able to: identify the three (3) components of CCTV systems and describe their functional interrelationships list peripherals commonly used with CCTV systems list the three (3) possible functions a customer wants a CCTV system to provide describe the basic considerations influencing a CCTV system design explain the three (3) functions required to create a video image describe the function and advantages of a CCD (Charge-Coupled Device) given industry standard camera (CCD) formats, identify and describe their individual features and applications list and explain the three (3) primary considerations in selecting a camera describe the four (4) secondary factors that affect image quality list the environmental factors that contribute to the selection of an appropriate camera/lens configuration given the two (2) principles of illumination, reflected light and available light, define their role in the design of CCTV systems list the factors to consider in selecting monitors distinguish between the types of transmission media, their capacities, limitations and applications explain the three (3) most important considerations when selecting an enclosure describe the unique requirements of fixed and pan-tilt-zoom cameras, and how they are used given types of control/signal processing equipment, identify, select and apply the equipment to technical requirements Use the Menu at left to navigate through the course.

CCTV System Definition

CCTV System Definition Select the first topic below to begin this lesson: ● ● ●

System Definition Basic System Performance Issues Structure of Video

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System Definition CCTV — Closed Circuit Television — has become a prime tool in modern security systems. In the past few decades, technological advances have made video monitoring systems much more effective for security and much more affordable. This book introduces CCTV concepts and equipment. It highlights the capabilities and limitations of each component of a CCTV system. The most basic CCTV system consists of a: camera (imaging device) transmission medium (connecting cable) monitor . Larger, more complex CCTV systems:

http://training.simplexnet.com/SEC603/A1-U-760.htm (1 of 5) [10/16/01 9:10:52 AM]

CCTV System Definition

utilize many more cameras (which may be remotely controlled) may include multiple viewing points (monitors, controllers, multiplexers) use a variety of transmission mediums to send the signal from the camera to viewing device (coaxial cable, fiber optic, twisted pair, even phone lines or wireless transmission via microwave). In most systems, peripherals provide additional capabilities. Recorders allow video images to be stored. Printers generate "hard copy" of selected images. Switching devices allow operators to select specific cameras and direct their output to specific monitoring devices. Controllers permit operators to point the camera at an area of interest and to zoom in or out.

CCTV System Definition

Basic System Performance Issues Regardless of the technologies used in designing and implementing a CCTV security system, there are a number of issues that must be addressed in all situations. First, what information does the customer want the system or component to provide? There are three (3) possible answers: Detection - indicate something is happening in the field of interest Recognition - determine exactly what is happening Identification - determine who is involved in the activity. Each of these three answers can effect the type of equipment selected for a given CCTV application. In addition, there are other basic considerations that will influence CCTV system design — and, of course, the customer's budget. These basics include: Required quality of representation of field of interest Environment in which the equipment will be used Size of the field of interest to be viewed Available light — and need for supplemental lighting Power source. Again, each of these will influence the CCTV design. For example, if a "truer" representation of a scene is required, design specifications might call for color as opposed to Black and White cameras.* Each additional consideration also has a significant impact on component selection

CCTV System Definition

criteria. By the conclusion of this book, you will have an understanding of what system designers must consider as they develop a CCTV system. * More detail and resolution can be acquired using a lowlight level Black and White Camera. However, to support shoplifting litigation color cameras are required to properly identify perpetrators. As a rule of thumb, color cameras and monitors should be used in systems that will be used for identification purposes.

Structure of Video

CCTV System Definition

The most basic piece of information regarding "video" is its structure. As shown in the figure, all video motion images are actually made up of still images — or frames. Each frame, in turn, is composed of two (2) fields. When these two fields are properly synchronized and interlaced in a 2:1 ratio they form a complete still frame of video. Video cameras use AC voltage to synchronize this process of creating motion video. In countries using 60 Hz (cycles) alternating current, each second of video contains 60 fields forming 30 frames. In Europe and other regions using 50 cycle, there are 50 fields and 25 frames of video per second. To the human eyes, these frames of video appear as moving images.

Cameras

Cameras Select the first topic below to begin this lesson: ● ● ● ● ● ● ● ●

Camera Technology CCD Function Camera Ratings Camera Options Camera Sensitivity Illumination Camera Resolution Other Camera Issues

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Camera Technology Video cameras were once large, heavy devices requiring high levels of power, with multi-wire cabling to transmit signals to and from the camera. The image sensor was a large photocathode tube. Such tubes, which are still in use today, are susceptible to jarring or vibration. Even minor bumps to a tube camera can seriously degrade image quality. In addition, tube cameras aimed at the same scene for long periods experience "burn-in." The image, especially from bright or linear shaped objects, permanently sensitizes the image sensing tube, so that a "ghost" of an object appears to be present in the scene

Cameras

even if it is removed. Today, with advances in technology, cameras can be smaller than a lipstick case, with minimal power requirements, high resolution, and high image stability. But despite all the improvements, the functions required to create a video image remain the same. lens - a means of gathering the light reflected from a subject image sensor - a device to convert the light image to electronic signals processing circuitry - to organize, optimize, and transmit those signals. CCTV cameras are available in both monochrome (black and white) and color. Monochrome affords the following advantages: Higher resolution Requires less light Lower cost Color, on the other hand, offers: Better overall representation of a scene (with proper light) Better capabilities for identification and prosecution

Cameras

CCD Function The preferred camera for use in CCTV security applications today has no tubes; instead, the camera is designed using all integrated circuits. The electronic component replacing the image sensing tube is, in most instances, a CCD (ChargeCoupled Device). A CCD is actually an integrated circuit containing hundreds of thousands of tiny light sensitive receptors. This grid of receptors breaks an image into picture elements (pixels). When individual receptors are "excited" they emit electrons. The amount of electrons emitted varies according to the amount of light hitting the surface at any given moment. A

Cameras

receptor being excited by a lot of light emits a higher voltage (more flowing electrons) than one being excited by lower levels of light. In a simplified explanation of the process, electrical impulses generated by the CCD are processed and outputted from the camera in a rigidly defined manner. Monitors and other output devices then reprocess the incoming information in the same defined manner, thus creating a representation of the image "seen" by the camera. While CCD cameras are being used more and more, many CCTV security systems still employ tube cameras. For most companies which use tube cameras, there is no reason not to upgrade to CCD cameras. Tube cameras are no longer manufactured and CCD cameras are economically priced. CCD cameras offer the following: less susceptibility to shock and vibration lower power requirements (because they are solid state) no distortion of the image highly resistant to image "burn-in" greater sensor reliability (requires less maintenance) longer overall life cycle than a tube camera can be used in a wide range of lighting conditions

Cameras

Camera Ratings The primary way of identifying cameras is by image sensor size. The current standards are listed in the figure. These dimensions refer to the diagonal size of the image sensing device, either tube or CCD. The image lens or size effects the camera's light sensitivity (the amount of light required to process an image) and resolution (a measure of image detail and quality). With advances in technology and increasing miniaturization, these standard sizes continue to shrink, allowing for even smaller camera packages. This is due

Cameras

to higher yields in silicone wafer chips, resulting in chips with equal sensitivity at lower costs.

Camera Options Proper camera selection for a CCTV system is of course important for maximum system effectiveness. On the other hand, with the range of cameras available, it is possible to select "over-qualified" cameras, that is, cameras with more capabilities than are actually required. By selecting cameras with features which closely match the needs of a given job, significant cost savings may be realized and the system may be expanded or otherwise enhanced as a result. Therefore, in selecting a camera, it

Cameras

is important to know why, where, and under what conditions a camera will be used. Specific camera features and capabilities can then be matched to the customer's needs.

Camera Sensitivity Sensitivity describes a camera's ability to "make pictures" in varying levels of light. The higher the sensitivity, the less light is required by the camera to produce usable images. The terms, "usable video" and "full video" are often heard in discussions of sensitivity. An image that contains some recognizable detail but also has dark areas with no observable detail may be classified as "usable." As shown in Figure 3-8, using a camera with higher sensitivity (or adding light to the same scene) will immediately cause details to appear where there was formerly just blackness. When all objects in an image are all visible, it is described as "full video." Most customers want their systems designed to full video standards. Full video is 7.14 volts peak to peak + 100 IRE (1

Cameras

IRE = .714 mvolt). (IRE is Institute of Radio Engineers.) While there may be some subjectivity in determining usable video, light can be measured scientifically. Camera sensitivity is, therefore, expressed in terms of the level of light required to produce usable or minimal quality video. Most camera specifications provide usable and full video light levels. Therefore, when considering camera sensitivity, it is important to know the lighting conditions in which the camera will be used (see "Illumination" below). Camera selection should include determination of how high the sensitivity must be to produce usable video with the minimum amount of light available at the surveillance location. Note there are cameras available which can produce images in extremely low light level. Some CCD cameras (using intensifier CCD's) can produce images with just the illumination from starlight. Specialized tube cameras can even produce images with less light. More typical cameras have more than enough sensitivity to function well in standard industrial or corporate settings.

Cameras

Illumination Illumination refers to the light falling on a scene. Strictly speaking, illumination is not a camera function; however, it is a critical issue when considering which camera to select for a given area. Adequate illumination is essential to acquiring images which allow security personnel to monitor an area (detection), observe activity at the location (recognition) and identify specific actions, objects or persons (identification). Keep in mind that the camera (like the human eye) actually processes reflected light (Figure 3-9), that is, light reflected off objects and persons in the field of view. We will discuss additional lighting issues later, but for now, we simply want to note the following: the amount of illumination

Cameras

available — in conjunction with the camera's sensitivity — is crucial information when selecting a camera for a given application. Illumination and sensitivity have an inverse relationship: more light, less sensitivity is required .. less light, higher sensitivity is required.

Camera Resolution

Cameras

As suggested in the figure, resolution is a means of defining image sharpness and detail. The higher the resolution, the better the definition and clarity of the picture. A system within the camera "scans" an image in a series of lines running horizontally. Each horizontal line is made up of a number of elements. Once one line is scanned, the second line is scanned and so on. Resolution is a measure of the quantity of both the individual lines and the component elements making up each line. In a CCD camera, resolution has a direct relationship to the number of pixels on the CCD image sensor. Resolution measures the number of horizontal lines a camera uses to produce an image. Horizontal resolution measures the number of elements making up each horizontal line. Vertical and horizontal resolutions typically yield a 3:4 ratio relationship; e.g., 600 lines vertically, to 800 elements in each line. Resolutions for CCTV security cameras are usually in the 320 to 470 line range. Special high resolution cameras can generate up to 800 lines and higher per image scan. The higher the camera's resolution, the more detail is visible (because the lines are closer together and there are more elements in each individual line). Lower resolution cameras produce images with less detail; however, do no confuse resolution with focus or lens quality. Resolution is a technical measure of a camera's electronic design and function. It is a major factor in image quality, although other factors contribute as well. Light levels, lens quality, monitor resolution, and even the medium of transmission can all effect the way an image

Cameras

ultimately appears to a viewer.

Other Camera Issues In addition to the primary considerations when selecting a camera, there are four (4) other factors that affect image quality. These include: Manual and electronic adjustments Electronic iris/Automatic shutter Backlight compensations Digital Signal Processing

Cameras

Manual and As with all sophisticated electronic Electronic components, periodic adjustments to Adjustments a camera may be required to maintain its optimum performance. On some cameras, these adjustments must be done manually. Newer cameras permit a limited amount of adjustments to be made electronically from remote locations. The benefits to this are clear: Immediate corrections can be made as required Adjustments are instantly made from one central location

Cameras

Consider a camera mounted on a pole in a parking lot. A technician can make such adjustments to this camera with no concern for the weather, and without having to climb a ladder or use a personnel lift. Valuable time is saved, the change of injury reduced, and there are fewer interruptions to the security operation. However, this can be done only with high-end cameras that have advanced technology using a matrix switches with a software control package. Electronic Iris The iris controls the amount of light striking the face of the image sensor. It deals with the quantity of light. It is either a mechanical (manual) or electro-mechanical (automatic) component of the lens. If too much light hits the image sensor, the image "burns out" (the image is all white or portions of the image are "too hot," that is, all light colored surfaces may lose all detail). Closing the iris corrects this. At the other extreme, too little light hitting the image sensor results in a black image or one in which only the brightest objects are visible. Opening up the iris corrects this situation. Irises may be manual or automatic in

Cameras

their operation. In cameras with automatic (electronic) iris control, circuitry continuously samples the amount of light hitting the image sensor and opens or closes the iris accordingly. Auto Iris is especially valuable in setting where light levels are constantly changing — exterior locations for example.

Automatic Automatic shutter control adds further Shutter flexibility to a camera. It deals with the quality of light. Remember basic high school science, "white light" is actually made up of several colors — the colors of the rainbow. Each has a specific wavelength. Sunlight is said to be the

Cameras

most "pure" form of white light, that is, each wavelength is present in roughly equal amounts. However, in other types of light (fluorescent, household light bulbs, sodium vapor streetlights, etc.), wavelengths are unequally represented. While the human eye is able to compensate for many of these differences, a color camera cannot without specialized circuitry. As shown in the figure with a color camera, these differences are extreme, possibly resulting in significantly degraded image quality. Where auto irises adjust for light quantity, automatic shutters compensate for changes in light quality. Thus, an external camera with automatic shutter control is able to produce accurate images of activity in a parking lot in daylight as well as under artificial illumination. Electronic Iris and Automatic Shutter have become more marketing lingo than actual functions. There are several spins on these functions, "Super Shutter, Super Iris", etc. Electronic Iris is actually an automatic iris function that resides in the

Cameras

camera instead of in the lens. An Automatic Iris lens measures the video signal strength of the camera and then decides to open or close. The intelligence is in the lens itself. Realizing that the information needed already exists in the camera, manufacturers developed electronic iris functions within the camera. To accompany this added feature, lens manufacturers have developed "dump" auto iris lenses. More appropriately, simply motorized or "DC" lenses. The decision is made in the camera about the iris opening and voltage rather than in the lens. This technology combination results in lower cost. Automatic shutter is similar in operation but doesn't involve the lens directly. Shuttering is a function of the camera. Basic cameras sample, or look, at an image at a rate of 60 times per second, a shutter speed of 1/60. Digital technology, which already exists in the camera, has been enhanced so that this circuit can now analyze the video signal and, if needed, change the sampling rate of the image up to 100,000 times per second. This allows darker images to be "digitally" sampled more, utilizes

Cameras

existing light, and produces better pictures.

Backlight Backlight is light which is behind the Compensation object of interest in a scene. This can be a major problem, especially in cameras with automatic iris control because the camera will often adjust to keep the bright background within acceptable levels. Consider a camera aimed at a door at the end of a dark hallway. When someone opens the door and steps into the hallway, the camera will try to compensate for the sudden bright

Cameras

exterior background. The result will be the person in the doorway will appear silhouetted and lose detail in "shadow." In extreme cases, there may be no discernible detail at all. Cameras must have backlight compensation to overcome this situation. Backlight compensation is composed of camera circuitry which samples a scene and makes an assumption that objects in focus are the objects of interest and that light levels should be optimized for these objects. Extremely high background light levels are selectively shut down while maintaining optimum levels on the objects of interest.

Cameras

Digital Signal Many cameras today employ digital Processing signal processing. This circuitry allows elements of the video signal to be enhanced or stabilized, thus improving overall image quality when delivered to the monitor. Digital signal processing can be valuable in improving images of low light level scenes. In addition, video signals which are digitized may be sent over longer distances using standard transmission mediums without the degradation associated with standard analog video signals.

Lens Technology

Lens Technology Select the first topic below to begin this lesson: ● ● ● ●

Lens Technology Mounts Focal Length Lens Selection

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Lens Technology The lens is essential for creating video images. A camera lens is the mechanical equivalent of the lens in the human eye. It controls the amount of light hitting the image sensor (retina, in the eye) and keeps objects of interest in focus. The characteristics of a particular lens determine the portion of an area "seen" by the image sensor, where the focus will be, the magnification (if any) of the objects of interest, and the amount of light striking the image sensor. The lens is designed to be used with specific image sensor sizes (1", 2/3", 1/2", 1/3"). The figure identifies the basic components of all lenses. Every lens is composed

Lens Technology

of a barrel, one or more glass lenses, an iris or aperture, and a mount. The barrel prevents extraneous light from hitting the image sensor. It also provides the means for mounting the lens to the camera. It houses the mechanics which allows the lens to be adjusted. The glass lenses define the image area, its size, shape and focus. As discussed above, the iris (also referred to as the aperture) controls the amount of light striking the image sensor.

Mounts

Lens Technology

For decades the standard video mount has been the C mount. Today, a new mount — the CS Mount — in replacing the C mount as the standard for small format (smaller image size) cameras. As shown in the figure, the major difference in the two mounts is that the CS mount puts the back flange of the lens 5 mm closer to the image sensor. With the use of an adapter, C mount lenses can be used on CS mount cameras; however, the reverse is not true: CS-type lenses cannot be used on C mount cameras. Finally, CS mount lenses are generally less expensive than C mount lenses.

Lens Technology

Focal Length Lenses may be categorized by both their focal length and aperture opening. Focal length (fL) is the distance between the center of the lens and the image sensor. Focal length measurement is expressed in millimeters. This is an important measure. Lenses are defined as normal, wide angle, or telephoto according to their focal length. For a 1/3 inch format camera, an 8mm lens, for example, is a wide angle lens, that is, it "sees" a wide field of view. On the other hand, a 1000mm lens on the same camera in the same location see a much narrower field of view, although the objects are significantly magnified. The longer the focal length, the greater the magnification. Zoom lenses are actually variable focal-length lenses. Focal length is one of three factors that are closely related and of crucial important in designing a CCTV installation. The other two related factors are camera placement and desired field of view. Changing one of these factors results in a change in the other two. For example, by increasing the camera distance from the area of interest or by decreasing the focal length of the lens, it is possible to enlarge the field of view. Conversely, by moving the camera closer to the area of interest or by increasing the lens focal length, the field of view if reduced (and magnified). As discussed earlier, the iris (or aperture) opens or closes to adjust the amount of light striking the face of the image sensor. Although there are some fixed aperture lenses, most are adjustable using a ring which can rotate around the lens

Lens Technology

barrel. Aperture control may be either manual or automatic. In addition, some cameras allow an operator to control the iris from a remote location. Aperture opening are expressed in fstops. The smaller the f-stop, the larger the opening and the greater light transmission, and vice versa — the larger the number, the smaller the opening, with less light being transmitted through the lens. Note that aperture opening may also be referred to as "speed" — a somewhat confusing term, since nothing is actually moving faster in a "fast" lens than in a slow one.

Lens Technology

Lens Selection Proper lens selection requires four specific pieces of information: Camera format Mount format Distance from subject to image sensor Height and/or width of scene. Camera format (measures as size of the image sensor) and mount format are "nuts and bolts" issues. Generally, in designing a system, the latter two items — distance to subject and size of field of interest — are the primary considerations. Lenses are then selected according to those parameters, making sure that the selected lens matches the camera, both in camera format size and type of mount. This is true when both lens and camera are being purchased. If a new lens is being purchased for an existing camera, then obviously only lens mating with the existing camera can be considered. The fact is, a lens which meets the requirements of distance and field of view size should be available in each mount and camera format.

Light Considerations

Light Considerations Select the first topic below to begin this lesson: ● ●

Light Source Comparison Reflected Light

Light Source Comparison There are two aspects of light which effect camera performance: quantity quality The quantity of light is fairly obvious: adding light makes a scene brighter generally produces a better video image (unless the amount of light is extremely high or the lighting is uneven). The quality of light was discussed earlier. To summarize the earlier discussion, not all light is the same; cameras must be able to compensate for different types of light with special circuitry. In addition to the range of light visible o the human eye, cameras can "see" certain "invisible" wavelengths of light — infrared, for example. Some cameras are specifically designed to enhance these invisible wavelengths, thus producing higher quality images in low levels of "visible"

Light Considerations

light. Light — its quantity and quality — is always an issue in designing CCTV security applications. In addition, other factors must be considered if additional lighting is required at a given location. The Light Comparison chart in the figure lists several types of lighting and their characteristics — both in terms of optical performance and practical features such as average life and operating cost. Selection of specific type of lighting depends on the demands of the application, budget, maintenance issues, etc.

Reflected Light

Light Considerations

The camera, like the human eye, actually sees reflected light. Light strikes an object, bounces off it, and that light passes through the lens, strokes the image sensor and creates an image. Different materials reflect light at different rates. A black cloth, for example, is black because it absorbs all of the light, and reflects very little. A red object is seen as "red" because it reflects that specific wavelength and absorbs all the others. A white object reflects virtually all light. Finally, because different light sources may emphasize certain wavelengths, the light source itself affects reflectance, color, and overall illumination. So far, our examples have dealt with objects of "pure" color. The figure lists several common areas or objects and the reflectance values, that is, the percentage of light reflected off them. Also man-made materials tend to reflect more light that natural objects. This is especially true in fabrics. Cotton or wool will absorb light, while polyester or rayon will reflect light.

Monitors

Monitors

Monitor Size and Recommended Viewing Distance While CCTV monitors may appear similar to standard television sets, they generally have no tuner circuitry; therefore, they can only generate images from direct composite video input. (Some recent models do incorporate TV tuners, although this is certainly the exception, not the rule.) Monitors may be either black and white (monochrome) or color. In the past, virtually all security CCTV monitors were B&W (as were CCTV cameras), although current trends point to an increasing use of color. Care should be taken to avoid mixing B&W cameras and color monitors. Linking a high resolution B&W camera to a color monitor of lower resolution produces images of poor resolution and lower quality. Monitors are available in a variety of sizes ranging from 5 inches to 27 inches. In systems having a dedicated monitor for each camera, the monitors are typically small — 9" diagonal measure, for example — with perhaps one larger monitor to allow the operator to "call-up" a specific camera to view in greater detail. Larger monitors allows for effects such as split screen viewing where two or more

Monitors

video sources are displayed simultaneously on one monitor. In the past, a frequently cited "ideal" design for security applications called for one monitor for each camera; however, today systems increasingly use large monitors in conjunction with new multiplex and quad compressor technology to view several video sources on one screen. Fewer monitors can mean reduced maintenance cycles and lower initial cost, although multiplexing and compressor technology will offset this. Also recent studies have reinforced the fact that operators can not effectively view and comprehend more than three (3) monitors for more than 45 minutes continuously. Monitor size also has a bearing on the design of the operation center where the monitors are located. Smaller monitors will require that the operator be closer to them in order to see detail within the image. The figure lists common monitor sizes and the recommended viewing distance from the operator to the screen. Just as cameras scan an image in a series of horizontal lines, monitors draw information on the screen in scanned lines. Smaller monitors put these lines closer together than larger monitors, therefore the smaller the monitor, the higher the resolution. Also, as a general rule, the resolution of monitors will exceed the resolution of most CCD cameras. A final note regarding monitors: the home television market has a direct bearing on the monitor market. Picture tubes, specifically, are built to the less demanding specifications of the consumer market, and therefore are likely to have a shorter lifespan than other CCTV

Monitors

equipment.

Transmission Mediums

Transmission Mediums Signals from the camera to the monitor and other devices are typically transmitted by coaxial cable, fiber optic cable, twisted pair wire or microwave. Special CCTV applications may utilize other transmission mediums. Select the first topic below to begin this lesson: ● ● ● ● ●

Coaxial Cable Fiber Optic Cable Twisted Pair Wire Microwave Telephone Network

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Coaxial Cable

Transmission Mediums

Coaxial cable ("co-ax") is by far the most common method of transmitting video signals from the camera to the monitor or other video processing devices. Coaxial cable consists of a single wire surrounded first by a nonconductive insulating layer (dielectric), then by a braided wire shield, and finally a plastic or rubber covering. Note that CCTV applications require cable of the highest quality materials and manufacture. Both the center conductor and the braided shield must be copper. Aluminum foil-wrap shield, which is used in some consumer cable applications, does not meet CCTV requirements. As reported in the chart of coaxial cable specifications in the figure, direct-run distances of up to 2,000 feet can be achieved, depending on the gauge of the cable. (The heavier the cable the lower the signal loss, and thus, the longer the run.) Cable runs across greater distances are possible, although this requires the use of amplifiers inserted in the line between the camera and monitor. Poor quality cable can have a serious impact on reliability and image quality. In addition, other factors can effect system performance. Because transmission through coaxial cable is electrical, it is susceptible to RFI (radio frequency interference) and EMI (electro-magnetic interference). Signal loss occurs along the course of the cable and it is possible for unauthorized persons to acquire the video signal either through these emissions or by directly tapping into the cable. Care should be taken in properly grounding the entire CCTV system when using coaxial cable or any other form of electrical signal transmission. Improperly grounded devices and cabling can result in ground loop effects (RFI/EMI

Transmission Mediums

interference) and other potentially damaging effects.

Fiber Optic Cable

Transmission Mediums

Fiber optic cable is lightweight and made up of a single spun glass or plastic fiber or a group of such fibers encased in a protective covering. It has a broad bandwidth making it ideal for carrying video signals. In fact, a single fiber cable can carry several video signals, or a combination of video, audio and data, this is dependent upon the transmitters and receivers used in the application. Fiber optic cable can transmit signals up to six (6) miles without amplification. Because it transmits modulated light, the video signal coming from the camera must first go through a fiber transmitter which converts electrical signals to light impulses. A fiber receiver at the other end is required for conversion back into electrical signals. Fiber optic cable is immune to RFI and EMI and other types of electrical interference. Grounding is not an issue with fiber optics. Furthermore, in systems designed with top-of-the-line components, fiber optic cable has high costperformance ratios. In low end systems, this may not be the case and the expense of fiber optic cable may not be warranted. Fiber optic cable requires extremely precise installation. Even the most minor damage to the cable or sharp bends can cause a major degradation of the signal.

Transmission Mediums

Twisted Pair Wire Twisted pair wire is exactly that: two wires, twisted together. They are most often 22 or 24 (AWG) gauges in size. When using twisted pair for video transmission, use only shielded twisted pair and only use the wire to connect one camera to a monitor or other device; that is, the twisted pair must be dedicated solely to this particular video camera. While the per foot cost of twisted pair wire is lower than coaxial cable, it requires signal conversion devices (transmitter and receiver) at either end of the wire run. Twisted pair wire can be used in runs of up to 5,000 feet. By using repeaters at least every 4500 feet, twisted pair can be used over greater distances. Twisted pair, like other electrical transmission mediums, may

Transmission Mediums

be susceptible to various forms of interference and unauthorized acquisition of the signal. A final note: performance is compromised when wires are routed through a telephone switching station.

Microwave

Transmission Mediums

Microwave transmission is line of sight. It involves transmitting a narrowly focused radio signal from the camera transmitter to a receiver. Signal strength may degrade because of fog, rain, even flocks of birds and other factors. These problems can be overcome by a proper design and properly selected components. Because of this, the transmission distance is always determined with a "margin of safety" — technically called a freznel zone. Thus, microwave transmission is, at best, a mid-range medium (in the 2,500 foot range). Greater distances may be achieved by using repeaters. While some newer, low power systems do not require FCC licensing in the U.S., most microwave technology does, with similar requirements in other countries. Depending on its specific configuration, a microwave systems can transmit video, audio and/or data. Microwave transmission is only appropriate in special applications. The chief reasons for using microwave are if conventional "hard-wired" options are impossible or extremely expensive. Consider a company having its CCTV operations base in a building in St. Louis, with requirement to monitor a company building in East St. Louis across the Mississippi. Microwave may be the most feasible solution in this situation. Portable microwave systems may also be appropriate for shortterm usage — for example, providing coverage for a special one-time event occurring in a remote part of the grounds of a facility.

Transmission Mediums

Telephone Network A final option for transmission of video signals is the use of the world-wide telephone network. Standard voice grade telephone lines have a narrow bandwidth. This means these lines do not have enough capacity to handle full "real-time" video. Nevertheless, phone lines still have value in specialized CCTV applications. Many CCTV systems utilize "slow-scan" video imaging. Instead of using the standard 30 frames per second, slow scan video selectively skips frames. In addition, each frame may be a lower resolution than standard video. Digital compression can improve this transmission method considerably. With constantly improving compression technology, it is now possible to send video images more efficiently across the phone network. Currently, one frame of video can be

Transmission Mediums

transmitted every 6 to 12 seconds over standard phone lines at 28.8K bits per second. Higher bandwidth quality ISDN (Integrated Services Digital Network) phone lines combine two 56K "channels" for a total transmission speed of 112K bits per second. This high speed data transfer rate allows one frame of video to be transmitted in approximately one second. As of this writing, other high speed options have yet to realize their full capability. These include T-1 or Fractional T-1 lines and satellite. The T-1 family of technologies allow for multiple 56K channels to be combined to achieve wider bandwidths. Current technology only allows use of two channels, effectively limiting the T-1 output to that of ISDN. Satellite communication technologies for CCTV applications remain in development. Eventually, you will be able to send video, audio and data transmissions over these mediums for CCTV systems. As in fiber optic cable and twisted pair, conversion devices are required for all these technologies using the telephone network. In voice grade telephone lines, the video signal is converted to audio signal, much as a modem converts digital computer information to audible tones. In other telephony transmission mediums, the signal is transmitted digitally. Despite the current limitations of telephone transmission, it does have one clear advantage: signals can be sent and received (video, audio, and pan, tilt and zoom instructions) anywhere throughout the global telephone network.

Transmission Mediums

CCTV Accessories

CCTV Accessories Once basic decisions have been made regarding cameras, lenses, monitors, and method of transmission, several other considerations remain. The first of these decisions has to do with enclosures and/or mounts for the camera and remote control positioning systems. Select the first topic below to begin this lesson: ● ● ●

Enclosures Mounts Remote Positioning Devices (RPD)

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Enclosures Enclosures serve two distinct functions. They protect the camera and lens from environmental factors and they disguise the camera and lens, thus minimizing the possibilities of detection. Enclosures may be designed for either exterior or interior use. There are three important considerations when selecting an enclosure: the ability to protect the camera and lens from

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tampering interior or exterior use identification of specific environmental conditions at the camera location Tamper proof switches and lock kits address the first concern. Enclosures are available in both interior and exterior configurations. Although current cameras are more rugged than older cameras, they are still susceptible to a variety of environmental factors. Heat, cold, humidity, dust, wetness, direct sunlight can all degrade a camera's performance and shorten its expected life cycle. To compensate for such environmental conditions, a number of options exist for enclosures: coatings to resist salt or even radiation heaters and blowers defoggers wipers/washers sun shields insulation packages protective coatings such as Rain-X® With respect to the last item, raindrops on the enclosure window (through which the lens is aimed) can quickly and seriously degrade visibility. These coatings help prevent raindrops from building up.

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Mounts Mounts attach the enclosure and its contents to a stable surface. Many are adjustable, permitting the camera to be oriented for optimal viewing of an area. It is important that the mount be both tamper resistant and stable. Especially with a telephoto lens, even a small amount of movement — vibration from machinery on the floor above a mounted camera, for example — can severely degrade image quality. The mount must be matched to the weight and load displacement of the enclosure and camera assembly, again to ensure proper orientation and stability. Mounts may have fixed or adjustable heads. Adjustable heads allow the enclosure and/or camera to be positioned for optimal viewing. Some of the most common mounts for

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interior applications include: wall mounts ceiling mounts - either flat (flush mount) or drop parapet mounts corner mounts pole mounts The figure shows some of these mounts. Another type, the dome mount,<.i>, essentially combines the functions of the mount and enclosure. The dome mount is typically mounted on the ceiling and is made of clear, mirrored or tinted material. Domes offer all the other mounting configurations as well. To review, selection of the proper enclosure and mount depends on: weight and load displacement of the camera package actual surface or structure to which the mount will be attached the environment in which the mount/enclosure/camera is located

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Remote Positioning Devices (RPD)

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CCTV system operators have a distinct advantage in monitoring events if they are able to move and refocus the camera. It is only practical to do this be remote control. Such remote control devices allow operators to pan (move the camera side-to-side), tilt (move the camera up and down), and zoom (change from wide angle to close-up). These Pan/Tilt/Zoom capabilities are often referred to a "PTZ." Note: when using telephoto lens or zoom lens extended to telephoto, it is essential that the camera be capable of either remote focusing or autofocus. RPD units are available in several configurations: 355 degree (pans an almost complete circle, hits a stop, then must pan back) 360 degree (pans continuously in any direction) Present/Prepositions (sensors and motors in the drive-unit automatically pan and tilt to pre-defined positions) Auto-pan (automatic and continuous panning in a predefined manner) Scanners (pan, without tilt capability Selecting which Remote Positioning Device is appropriate for a given application requires assessing the type of coverage needed, the environment, load, and power requirements of the various system options. You must also factor in that regular maintenance should be performed to ensure its functionality remains constant.

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Signal Management

Signal Management Select the first topic below to begin this lesson: ● ● ● ● ● ● ● ●

Signal Management Switchers Matrix Switchers Quad Compression Multiplexing Video Recorders Video Recording Additional Signal Management Hardware

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Signal Management Signal Management is simply how the video signal is controlled by the system, once it leaves the camera. If the signal goes directly into one monitor, there is essentially no management. If, however, an operator can intervene to route the signal to one or more destinations (either monitors, VCR's or other devices), then signal management is in play.

Signal Management

Switchers

Signal Management

The controllers used to route video signals are called switchers. In their most primitive form, they are in fact little more than mechanical switches; however, today these devices can be highly sophisticated digital systems. They permit not just one-to-one switching (one camera to a selected monitor), but one-to-many (one camera to many output devices), and even many-to-one or a combination of all of the above. Such switchers may be operated manually or they may be driven by a computer. State-of-the-art CCTV switchers are generally programmable. This permits functions or sequences of functions to occur at specified times. For example, operators may program the system to display images from a number of cameras in a set sequence. Each image may be displayed for a set number of seconds or frames. Thus, an operator viewing one monitor can see the front entrance of a building, its lobby, a hallway leading from the lobby, a stairway leading off the hallway, and a doorway at the second floor landing of the stairway, all within the space of a few seconds, with the sequence repeating continuously until the operator requests a different sequence or a specific camera location. In addition, frames from selected sources may be recorded for purposes of logging and archiving events.

Signal Management

Matrix Switchers A new class of programmable CCTV switcher is the matrix switcher. These utilize a CPU (Computer Processing Unit) to manage the programming and control of the switcher's operation. Matrix switchers generally permit many more video source and output devices to be managed. Cross-point switching allows any input to be directed to any single or multiple output devices.

Signal Management

Quad Compression As shown in the figure, quad compression allows four (4) images to be displayed simultaneously on one monitor. Such "split-screen" displays require careful selection of monitors with respect the size and resolution. In addition, while the quad compression video can be recorded, when playing back, any of the four compressed images can only be "expanded" to full frame using digital enhancement. Notice that the monitor in the lower portion of the figure displays a digitally expanded full screen image. The image appears significantly degraded, and is a result of the digital expansion process. This condition is

Signal Management

known as "pixelation."

Multiplexing

Signal Management

Multiplexing affords methods of archiving video from several source onto one videotape. This process uses "Time Division Multiplexing" technology. Here individual frames from each camera are encoded with a camera ID number, date and time. As shown in the figure, the multiplexer cycles frames from each source to the recorder at a rate faster than the human eye can see. The actual number of frames depends on the number of multiplexed cameras and recording rate of the video recorder. Viewing the playback of multiplexer recordings requires a decoder ("D-mux," for De-MUltipleX). Operators can specify which single or multiple images they wish to view full-screen. The image may be degraded slightly, not a poorer picture, just less frames depending on the number of cameras involved. Full frame viewing is full resolution. Multiple camera call-up is digitally compressed. In addition, multiplexed video can be presented in a split-screen format on one monitor. The figure shows a few of the many screen configurations possible in multiplexed systems.

Signal Management

Video Recorders

Signal Management

Video recorders for CCTV security applications have the ability to record at: "real-time" frame rates (30 frames per second (fps) in North America) "near real-time" (20 fps) time lapse. Time lapse records only a specified number of frames per second. This procedure allows a standard two hour video cassette to record images from one camera over several days. A standard 2 hour cassette is capable of recording 432,000 individual fields of video, i.e., (120 minutes X 60 seconds per minute) X 60 fields per second = 432,000. If, instead of recording at the full 30 frames per second rate (60 fields per second), the recorder "grabs" five (5) frames of video every second, the same 2 hour tape will last 24 hours. A simple formula demonstrates how many fields per second will be recorded given a desired time lapse recording mode: 120/Mode = Fields per second where 120 represents the minutes of recording time on a standard length tape, and Mode represents the total hours desired to be archived on the tape. Note: the recording mode is selected from a range of options by programming the recorder. Refer to the figure for recording rates available at various recording modes.

Signal Management

Video Recording Video recording allows the end user to archive video transactions for administrative, legal or liability reasons. There are several methods and technologies used to record video signals: Standard 1/2" Video Tape - VHS T-120, standard two hour tape - S-VHS T-120, high resolution two hour tape (S-VHS decks only) - VHS T-160, extended play 8 hour tape. (Special tape heads used only on machines rated for T-160 tapes)

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8 mm - High resolution, exceptional detail Hard Disk - PAC based, digitally compressed recording There are also numerous methods or lengths of time that can be recorded: Real Time - Generally up to 8 hours - 30 frames per second Near Real Time, or Real Motion - up to 24 hours - 20 to 24 frames per second Time Lapse - up to 960 hours from 20 fps to 1 frame every 8 seconds There is generally a lot of confusion around time lapse recording. For real time recording, the tape is in constant contact with the tape heads. The machine slows down the tape feed to accommodate up to the eight hour mode. After eight hours, it is no longer technically feasible to slow down the tape feed. This is where time lapse recording comes into play. Technically, time lapse is a timing method in which the tape deck automatically places the tape against the tape heads, then removes it based on the desired time lapse mode. As the time lapse mode increases, the length of time the tape is in contact with the tape heads becomes shorter and the interval at which this occurs becomes longer. There is a sacrifice of video quantity and quality in the time lapse mode. As the time mode increases there is proportionately less video recorded, per camera. Depending on the scene being viewed, not recording every frame of video may be allowable. General

Signal Management

surveillance is a prime example. To determine how much video is recorded use the following formula: T120 Tape/Time Lapse Mode (in hours) = # of Fields per Second Example: 120/12 hours = 10 fields (5 frames) per second. Keep in mind this is for one video signal. If you have multiple cameras on the system, the amount of video per camera is reduced. In the above example, if the system has five cameras, there would be only one frame on video, per camera, per second. Once you have the frame rate, divide by how many cameras are in the system for actual frame per second/per camera. Having a time lapse recorder with extended recording up to 960 hours may sound great on a data sheet, however, recording 1 frame of video every eight seconds is not reliable evidence. As you increase the length of time of recording, resolution is also sacrificed. There is no specific formula to determine the loss of resolution. It is generally conditional upon the quality of the video heads and the tape being used. The quality of the tape heads is two fold. One is the manufacturer; you get what you pay for. The second is how clean the tape heads are. Regular service and a clean environment will help produce better time lapse recordings for longer periods of time. The tape used for time lapse recording is very critical. Not only for the quality of the recording, but also for the

Signal Management

maintenance of the deck itself. Many customers will want to go out to a local mass merchant and purchase a ten pack of consumer tapes for ten dollars. If they do, inform them that this may void any warranty of the deck. This is for a good reason. Consumer tapes have a thicker, more pliable emulsion on the tape. They are meant to be used only as a consumer product, several hours here and there. When used on a continuous duty industrial deck, the emulsion heats up and becomes sticky. This clogs and scars the tape heads, resulting in a poorer quality recording and shorter life span of heads. Industrial tapes have a thinner, harder emulsion that is designed specifically for continuous duty and matched to the style of tape heads used in the security industry. There is a new technology in time lapse recording called "Real Time" 24-hour recording. This is a marketing twist on human perception of "Real Motion." Real time video frame rates are determined by the AC sine wave, 60 cycles or 50 cycles. When you go to the movie theater, these 35mm films are at a rate of 24 frames per second. The human eye can perceive real motion down to 20 frames per second. Recent technology advances have made it possible to achieve "Real Motion" recording for a period of 24 hours at a frame rate of 20 per second. The catch is that they use T-160 tapes and tape transports, motor and the over-all design is for this specific length of time. They work extremely well. There is some confusion when some manufacturers refer to them as "Real Time" as opposed to "Real Motion." Selection of recording technology and length of recording time will be determined by the nature of the business.

Signal Management

Some industries, such as gaming and banking, have strict guidelines concerning recording times and archiving. Other industries are less formal, and the user usually defines the criteria. There are some basic guidelines: Determine the risk, safety and loss factors: cash handling, parking area, dormitory, retail, etc. Advise clients about the features and benefits of each technology as they apply to their situation. Assist client in weighing the cost/benefit, along with liability factors. Evaluate the result/cost of the realization of the described risks if video is not recorded or frames are missed. Design the appropriate systems to handle their requirements.

Signal Management

Additional Signal Management Hardware Signal distribution amplifiers boost the power of the signal being transmitted. Just as a cable signal can degrade when split over several TV's in a home, so too can a video signal degrade when distributed across several devices (switchers, monitors in remote locations, etc.). Distribution amplifiers maintain the video signal throughout the system. Video motion detection sensors detect movement at an area of interest or initiate a defined set of events. This may include activation of a video camera and transmission of the video to a monitor or recorder. PC managed systems also provide alarm message capability with routing to multiple locations or operators, which can be used as a proactive element of their security management program. Motion detectors usually employ infrared and laser technology.