What's On CCTV?

Even the best designed and installed camera system is nothing more than a security tactic or tool that should help answer the question: What is the owner interested in protecting?For example, when trying to protect the exterior building perimeter, parking lots, utility connections and other outdoor items, exterior cameras must be used.

11/01/2001


Even the best designed and installed camera system is nothing more than a security tactic or tool that should help answer the question: What is the owner interested in protecting?

For example, when trying to protect the exterior building perimeter, parking lots, utility connections and other outdoor items, exterior cameras must be used. These cameras are more expensive than interior cameras because of their cabling pathways and weatherproof environmental housings. Exterior cameras must also dynamically adjust to a wide range of lighting extremes from direct sunlight to situations where night vision cameras are required.

To obtain a usable image outdoors, a digital signal processor camera with the ability to balance the light in multiple zones within the image must be used. Monochrome cameras are also very useful outdoors, with a better ability to see contrast in low light conditions. Some color cameras will automatically switch to monochrome when the available light drops in the evening.

For general conditions, one cost-effective approach is to limit the number of cameras, however, the use of a pan/tilt/zoom (PTZ) camera is not an effective way to reduce the number of cameras. The cost for a PTZ camera is approximately three to five times the cost of a fixed camera, and typical PTZ cameras are not able to view all 360° at the same time. At best, 180° can be viewed, leaving 180° unprotected. Consequently, an intruder is often able to see where the camera is aiming and stay out of the line of sight. PTZ cameras are adjusted by human intervention or a signal from a motion detector or door contact. Because security personnel are not always available to move the camera, events can go unseen or unrecorded. PTZ cameras can be programmed to oscillate like a fan, but it is still possible for an intruder to avoid the camera. In addition, this constant motion creates a great deal of wear and tear on the camera motors, increasing maintenance costs.

Viewing the images

Another important question is how will the images be monitored and viewed?

At the lower end of the price spectrum is a multiplexer. This device is used to receive up to 16 different camera images and display them on the same screen, simultaneously or individually. When the images are shown at the same time, as small squares on the screen, they are not full-motion video; the images average less than two frames per second, so a person walking is shown as a series of still pictures two seconds apart. The benefit of multiplexing is that it allows all images to be viewed until more detail is required.

At the higher end of the price spectrum is a video matrix switcher. A switcher allows for thousands of camera images to be controlled through a single keyboard. Each port can be turned on or off, and can be viewed at any frame rate up to full motion. These are very common in casinos, airports and universities, or at school districts that need to control their buildings from a single site. Multiple sites can be networked to allow monitoring from a single point.

Another attractive approach is digital recording, which has been around since the mid 1990s. Although it tends to be more expensive, digital recording systems enable the end user to reduce the cost for PC components, bringing the cost to a point that most organizations can afford.

A digital recorder can be programmed to record at frame rates up to full motion for all images. The recorders also dynamically change the frame rate when motion is detected in the screen, which helps maximize the recording archive period. In other words, a full motion recording of an empty stair tower is not required, but when there is a change in the picture caused by a person walking through the scene, recording would be necessary. Also, a digital recording system by nature doesn't experience degradation of the image resolution, because the files are the stored in the same format as they are recorded.

There are a lot of choices in CCTV systems, but the key is to determine how critical the system will be to the goals of the security plan.



CCTV Options

Digital recording

Multiplexer

Video matrix switcher

Exterior/interior cameras

Monochrome for low-light conditions



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