B channel

The ISDN channel that carries 64Kbps of data; also known as a bearer channel.

back door (backdoor)

An opening left in a program application (usually by the developer) that allows additional access to data. Typically, these are created for debugging purposes and aren't documented. Before the product ships, the back doors are closed; when they aren't closed, security loopholes exist.


A small fluorescent lamp placed behind or below an LCD display to provide light.


A copy of files stored in a location other than where they originally came from.

backup policy

Rules that dictate what information should be backed up and how it should be backed up.


In communications, the difference between the highest ...

Get CompTIA A+ Complete Study Guide now with the O’Reilly learning platform.

O’Reilly members experience books, live events, courses curated by job role, and more from O’Reilly and nearly 200 top publishers.