Designing a CCTV Camera Security System

The first step is to make a list of the key security issues that are to be covered. For example this list might include:

• Bill Changer.
• Auto Cashier.
• Equipment Room Door.
• Inside Equipment Room with view of Bill Changer money hoppers.

The second step is to create a second list of nice-to-cover items such as:

• Individual Bays (allow cleanliness to be checked)
• Vacuum Cleaners
• General View of Premises.

The next step is draw a sketch of the site keeping it close to scale. (Using graph paper makes this step easier.)On this sketch make sure all the items in the lists above are shown. We suggest using different colors for the different priorities of the items to be covered. On the sketch also show utility poles and other likely sites for locating the cameras.

Now the locations of the cameras must be chosen. Using the sketch from the previous step, pencil in arrows that represent the location and direction of the cameras. Cameras need to be located where vandalism wont be a problem. Generally this consists of mounting the cameras high and out of reach. In some instances hidden cameras may be desirable. (For example, a hidden camera may be best for monitoring the service side of a bill changer inside the equipment room.)If identification of a villain is a goal, then the camera-lens combination must be located such that personal features are readily recognized. If the camera is located at a distance from the location of a bill changer, then the lens must be chosen to have sufficient telescopic ability to make the person's features recognizable.

With the camera locations chosen, the task becomes that of choosing the appropriate camera. In order to do this, the task to be accomplished by a particular camera must be kept in mind. For example, color is highly recommended for use in identifying suspects for prosecution as is a resolution of greater than 400 TV Lines.

In low light areas, Black & White cameras may have some advantage. Generally Black & White Cameras are slightly less expensive that the corresponding color camera. The LUX rating of a camera informs the user of the camera's relative performance with a given light intensity. The lower the LUX rating, the less light that is required to capture an acceptable image. (Black & White cameras are not recommended where identification of people may be important.)

Camera resolution is a measurement of a camera's ability to show detail in the image. Generally the more TV Lines, the better image results.

Some serious thought needs to be given to recording or reporting the visual data. Generally a recorder is used. There are two types of recorders available:

• VCR Tape Recorders
• Digital Recorders

VCR Tape Recorders The standard recorder is an endless loop VCR that works very similarly to a home VCR recorder. The difference is that the tape is continuously reused by the next series of images. When an incident occurs in which identification is required, the tape is removed from the recorder and a new tape is installed.The problem which frequently arises in such cases is that the tape containing the desired image was worn out by continuous reuse and thus the desired image is useless. The lesson to be learned is that the tape needs to be checked at regular intervals to make sure it is still suitable for use. See comparison of VCR vs. Digital Recorders

VCR Tape Recorders are designed to accept the input of a single camera. In order to use resources more efficiently, a Multiplexer may be utilized. Four channel and sixteen channel units are commonly available although other numbers of cameras may be accommodated.

Digital Recorders The Digital Recorder is essentially a computer that uses the hard disk as the storage media for the visual images collected by the camera. Since the Digital Recorder is a computer it can

• Accommodate up to sixteen cameras without using a multiplexer.
• Detect motion and sound an alarm or begin recording when motion is detected.
• Allow off-site viewing without additional software or hardware using an existing office computer. (The included software must be loaded on the office computer. Ask us for detailed requirements in order to use this feature.)
• Optional ATM or cash register interface is available at extra cost.
• Digital recordings don't wear out like VCR tape.
• Instant search by incident or date and time. (Do not have to wait for the tape to wind/rewind to the right spot.)

Multiplexers A Multiplexer is a device that accepts the input of more than one camera and combines these separate video signals into a single signal for storing on tape. The image returned from a VCR Tape Recorder which has a multiplexer in line is a split image screen. For example, a four channel multiplexer will divide the image into four equal rectangles on the display screen.

Definitions

• LUX The LUX rating is a measure of a camera's ability to record light. The lower the LUX rating, the less light that is required to acquire a good image. Technically one LUX is one lumen per square meter where a lumen was originally chosen to represent the light of one ordinary candle. Thus 1 LUX is the amount of light that a single ordinary candle displays at a distance of one meter, (39.37 inches.)
• Resolution The ability of a camera to show fine detail is measured by its "resolution." The resolution of a camera is stated in lines per inch. That is the picture that is drawn by the camera is made up of the number of lines per inch given in its rating. Thus a camera rated at 420 TV Lines will show more detail than one rated at 380 TV Lines. Generally more lines is better and especially if identification of suspects is a requirement for the camera.