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Back Focus

A procedure of adjusting the physical position of the CCD - chip / lens to achieve the correct focus for all focal length settings (especially critical with zoom lenses).

Back Light

A light placed at the rear of a subject to light from behind.

Back Light Compensation, BLC

This is a method that CCTV camera deals with a common and often unnecessary problem trying to register detail in a target that is harshly silhouetted against a bright light source.  This problem and its 'cure' is almost a tradition in our industry.  Sadly, even with the very best technology using well considered algorithms to reduce the silhouette effect it still is a compromise solution when combating the natural effects of light.

Balanced Line

A cable having two identical conductors which carry voltages opposite in polarity, but equal in magnitude with respect to ground, suitable for differential signal transmission.

Balun

Balanced to unbalanced (Bal-un) is the transformer used to connect an unbalanced transmission line (i.e. coaxial cable) to a balanced system or cable, or vice versa.  It can also provide impedance transmission, as 300 ohm balanced to 75 ohm unbalanced.

Bandwidth

The difference between the upper and lower limits of a given band of frequencies. It is expressed in Hertz. The range of frequencies that a transmitted communications signal occupies or that a receiving system can accept. For example, it takes more bandwidth to download a photograph in a second than to download a page of text. Virtual reality and three-dimensional audio/visual presentations require even more.

Baud

Rate of digital transmission equal to the reciprocal of the time of one output signaling element.

Bitmap

A bitmap is a data file representing a rectangular grid of pixels. It defines a display space and color for each pixel (or “bit”) in the display space. This type of image is known as a “raster graphic.” GIF’s and JPEG’s are examples of image file types that contain bitmaps.  Because a bitmap uses this fixed raster method, it cannot easily be rescaled without losing definition.  Conversely, a vector graphic image uses geometrical shapes to represent the image, and can thus be quickly rescaled. 

BNC Connector

Abbreviation for Bayonet Neil-Concelman., BNC connector is a coaxial cable connector used extensively in video and RF applications and named for its inventors. It is a connector for coaxial cable that locks when one connector is inserted into another and rotated 90 degrees.

Braid

A group of textile or metallic filaments interwoven to form a tubular flexible structure which may be applied over one or more wires or flattened to form a strap.

Broadband

In network engineering terms, this describes transmission methods where two or more signals share the same carrier.  In more popular terminology, broadband is taken to mean high-speed data transmission.