Surveillance Devices

Visual recording devices can play an important part in physical security. Their presence can discourage would be attackers, provide the ability for one person or system to monitor multiple areas simultaneously, and provide a log of events for an area. A commonly used system is closed-circuit TV (CCTV).

CCTV systems are made up of cameras, transmitters, receivers, and monitors. The camera captures the data and transmits it to a receiver which then displays the data on a monitor. Today's systems surpass older models that only allowed one feed to be displayed on a monitor at a time. Today, a monitor can show feeds from multiple cameras so that a security guard can see more than one environment simultaneously. Data captured by the camera is also often recorded on a drive for record and later review. Most modern CCTV cameras today also use light-sensitive chips call charged-coupled devices. This chips are what convert the light received into electrical signals. What makes the chips advanced is that they include infrared light which is normally beyond the scope of human eyesight. This allows for more granularity and detail in the resulting image.

An important consideration for CCTV cameras is what type of lens will you need. There are two main types used: fixed focal length and zoom (varifocal). The focal length affects how objects are viewed on a horizontal and vertical basis. Short focal length lenses provide a wider-angle view, while long focal length lenses provide a more narrow view. This angle determines what size the images seen by the camera will be and how much of an area the camera can view. So if you want to be able to monitor a wide area at once, a short focal length lens is most appropriate. If the camera is installed in a smaller area, a long focal length lens is best. A fixed focal length lens comes in a size such as wide or narrow and is stationery. A zoom lens is adjustable, however, and can be used to view something closer and will refocus.

The next characteristic of lenses is depth of field. Depth of field refers to what portion of the image is in focus when shown on the monitor. Depth of field is affected by the size of the lens opening, the distance of the subject, and the focal length of the lens. The depth of field increases as the size of the lens opening increases, the subject distance increases, or the focal length decreases.

Lighting also plays an important role in CCTV. Cameras have an iris lens which controls how much light enters the camera. A manual iris lens has to be adjusted manually and is best suited for an environment with a steady light supply. An auto iris lens has the ability to self adjust as the environment light changes such as outside.

The last consideration is that of mounting. A fixed mounting is stationery and cannot move in response to security personnel commands, whereas a camera with PTZ capabilities provides pan, tilt, and zoom features.

As you can see, there are many considerations for installing a CCTV system. To get the best results, a thorough assessment of the environment and needs of the organization should be done. CCTV systems can become very expensive quickly so it is important to prioritize what features are needed where.