Smile--You're On Camera

Oct 1, 2001 12:00 PM, By Jeffrey A. Lupinacci

Many schools and universities are installing closed-circuit television (CCTV) systems for security surveillance. Unfortunately, sometimes these systems are being installed without a clear understanding of what benefits the system will provide, and how the system will be supported by other security measures. Often, people think cameras alone will eliminate security problems.

Even the best designed and installed camera system is nothing more than a security tactic or tool to support the overall school security plan. Typically, cameras do not prevent an event from happening; usually they are used to review the event after the fact in an investigation.

Why cameras?

A solid security plan for a school facility should answer the question, “What are we interested in protecting?” If the answer is personnel and property both inside and outside the building, a school or university needs to identify its trouble spots. Is the institution more likely to have an assault in the parking lot or have equipment carried out the back door?

The configuration of the camera system needs to be based on a philosophy, such as the desire to record the face of everyone entering the building. If you also want to record the face of a person leaving the building, especially those stealing equipment, you will need at least a second camera, since the first will only view the back of the subject's head. If you also want general surveillance of long corridors, the images of persons at the far end of the corridor may be too small to identify, but might be adequate to identify a person carrying equipment.

When trying to protect the exterior building perimeter, parking lots, utility connections and other outside areas, you must use exterior cameras. Exterior cameras are more expensive than interior cameras because of the cabling pathways and weatherproof environmental housings. Exterior cameras also must adjust dynamically to a wide range of lighting, from direct sunlight to little or no light in the evenings.

For instance, a DSP digital camera can balance the light in multiple zones within the image. Monochrome (black and white) cameras can see better in low-light conditions and have sharper contrast. Some color cameras will switch to monochrome automatically when the available light drops.

The use of a pan/tilt/zoom (PTZ) camera is not always an effective way to eliminate the need for multiple cameras. The cost for a PTZ camera is three to five times the cost of a fixed camera, and a typical PTZ camera is not able to view all 360 degrees at the same time. It is possible for a person 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. Since security personnel are not always available to move the cameras, sometimes events are not seen or recorded. PTZ cameras can be programmed to oscillate like a fan, but again, a vandal can determine where the camera is pointed and avoid the camera's view. In addition this can create a great deal of wear and tear on the camera motors, and increased maintenance costs.

Take a look

As a school's philosophy and facility itself dictate the number of cameras and their placement, schools must determine who will be reviewing the images and how will they be used. Is the school willing to invest in the personnel, supplies and equipment maintenance to keep the system functioning correctly? Obviously, if cameras are installed and forgotten, they will soon fail.

A common misconception is that a security tape will rewind and record over itself automatically; therefore, no human intervention is required. In general, the use of analog tapes should not exceed 10 rewrites. After this amount, the recorded images are of such a degraded quality that they are extremely difficult to see. Often, a school will only find out that the equipment failed weeks earlier after an event causes them to review the tape.

This is a common problem in banks where ATMs are used. For instance, a customer gets mugged at an ATM while withdrawing money. The police request to review the bank's tape recording, only to find out that the camera has not worked in months.

Get equipped

How will the images be monitored and viewed? This will be a big factor in determining the flexibility of the system and, of course, the price of the equipment. The better the quality and the more features the equipment has, the higher the cost will be.

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 either simultaneously or individually. When the images are shown at the same time in a small square on the screen, they are not full-motion video. They average less than two frames per second, so a person walking is shown as a series of still pictures two seconds apart. The multiplexer's processor is working like a blackjack dealer, looking at each camera in secession, then returning to the first camera and beginning again.

The benefits of multiplexing is that it allows all images to be viewed until more detail is required and a specific image can be chosen to be viewed individually at full motion. The multiplexer also allows for all 16 cameras to have their images recorded on a single recording media.

At the high 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. Multiple sites can be networked and monitored from a single point. These are common in universities, or if an entire school district wants to control cameras from a single site.

Some studies show that a person can watch a monitor effectively for only 11 minutes of each hour. If this time is divided by the number of monitors that are in a control center, it is clear that CCTV cannot be used to stay on top of all images all of the time. Therefore, it is critical to record images as an investigating tool.

Traditionally, analog recording on time-lapse VCRs has been a mainstay in the industry, and has the lowest cost. The problem with time lapse is that the tape is slowed to make a tape last up to 96 hours. Using a multiplexer slows the recording down and will only produce a frame every three to 10 seconds. The images are at a low-resolution, making it critical to change tapes often.

Digital recording is more expensive and has been around since the mid-1990s. The reduced cost for PC components has brought the cost to a point that most institutions can afford. A digital recorder can be programmed to record at frame rates up to full motion for all images.

Digital recorders can change the frame rate dynamically when motion is detected in the screen. This is important to maximize the recording archive period; for instance, a school does not need a full motion recording of an empty stair tower, only when there is a change in the picture, caused possibly by a person walking through the scene. A digital recording system by nature does not experience degradation of the image resolution because the files are stored in the same format as when they are recorded, 1s and 0s.

Lupinacci, RCDD, is a LAN specialist and security designer for Brinjac Engineering, Inc., Harrisburg, Pa.

NOTABLE

• 11
  Number of minutes per hour a security person can effectively watch a security monitor.

• 96
  Number of hours the film is slowed to fit on a time-lapse recording tape.

• 16
  Number of cameras a multiplexer system can accommodate.

• 10
  On average, number of rewrites a camera security tape can be recorded over and still be effective.