Designing Your Security Video System

Food for thought as you plan your video installation


What Can Current Video Technology Do For Me?
This article is not intended to be a review of current technology, but it is important to understand the capabilities and limitations of technology before trying to mitigate any security problems. So let's go into a brief overview of what's out there today.

The capabilities of video equipment and, in particular, digital video equipment are advancing faster and with more impact than any other security technology area. The intelligent data processing of digital signals is creating this revolution. Video systems can now tell you

  • if something has been added permanently to a scene-e.g., a bag has been left unattended
  • if a fixed item has been removed from the scene-e.g., a painting from a wall
  • if an object is moving fast or slowly-e.g., a person is walking or running
  • the direction that an object is moving-e.g., a vehicle moving the wrong way on a one-way street
  • if an object moving in the scene is large or small-e.g., a truck on a road restricted to non-commercial vehicles
  • the estimated distance to an object and if it crosses a predefined boundary
  • the classification of an object, such as a person, a car, a truck, a boat, or an animal.

This list is not exhaustive but illustrates that video cameras are no longer just for surveillance or alarm assessment. They can now be the field sensors that capture primary data that, when processed, annunciates off-normal conditions.

Another area that should be understood is the design of the complete video system and the availability of functional interfaces of other security systems, such as access control, alarm monitoring and intercom. A decade ago, a camera was connected to a video switcher that controlled at which monitor its image was viewed. A video multiplexer also may have been used to display multiple images on a single screen; a time-lapse VCR was used for recording; and an interface to an alarm monitoring system may have been used to select camera views to be displayed based on associated alarm conditions and to select recording mode and/or recording speed.

Now the digital video recorder or, more recently, the network video processing system, is the center of the security video universe. It gathers the digital data from field sensors (intrusion detection and intercom devices as well as cameras), determines if there are off-normal conditions, and orchestrates the required displays, visual and audible operator alerts, and recording schemes. It may also interface with an access control system to assist its function of personnel identification and verification by augmenting its display with live video of someone seeking access.

What Support Infrastructure Do I Need?
Connectivity. The first area of focus is connectivity. The trend is to use the same cable as is specified for the voice and data telecom systems, and this is supported by current video technology. TCP/IP addressable cameras now connect, via Category 5 (Ethernet) cable, to a node on an existing corporate network or a dedicated security video network, or even the Internet. The video servers, DVRs or NVRs, are also network compatible.

Alternatively, the video signal is converted to communicate over unshielded twisted-pair cable with transmission distances far greater than the traditional coaxial cable, even in high-EMF areas such as elevator machine rooms.

Digital video, despite ever-improving data compression engines, is a bandwidth hog. Not all security video applications require a lot of bandwidth; for instance, not much is used if you're displaying single camera images only associated with an alarm or an access control validation. However, any application that plans to use existing corporate network capacity should be cleared with the network "owner"-often the IT department.

Lighting. The next support area to review, particularly if you plan to use exterior cameras, is lighting. Traditionally, black-and-white cameras have had the edge in producing a better picture under low-light conditions, while color technology, which requires higher light levels, provides a superior image for security identification and incident evaluation. Many camera manufacturers now offer units with the benefits of both: dual elements that can automatically switch between modes depending on ambient lighting.