电信专业英英词典B-1（在线收听）

　　B-Mac - This is a method of transmitting and scrambling television signals; the are time-multiplexed with a digital burst that contains digitized sound, video synchronizing, authorization, or information.

　　Backdoor - A way of getting into a guarded system without using the required password.

　　Backlog - The amount of work in process in the factory; it is usually expressed in terms of sales (sales backlog) or satellites (satellite backlog).

　　Backslash - This is the character "\".

　　Backspace - This is the command that causes the cursor on your screen to move back one space, and it can or cannot delete characters.

　　Band Pass Filter - A circuit that will allow signals within a desired frequency band to pass through but prohibits signals outside this frequency band from penetrating.

　　Bandwidth - The range of frequencies, expressed in hertz (Hz), that can pass over a given transmission channel (thus, determining the rate at which information can be transmitted). In satellite based systems a larger bandwidth of 17.5 to 72 MHz is used to spread the television signal; this helps to prevent interference.

　　Baseband - The basic direct output signal, which is in an intermediate frequency base and is obtained directly from a television camera, satellite TV receiver, or video recorder.

　　Baud - The rate of data transmission; it is based on the number of signal elements transmitted in a second. The term comes from the scientist J. M. E. Baudot.

　　BBS - This is an acronym for Bulletin Board Systems, which typically allow users to leave messages for other users.

　　Beacon - Relatively low-power carrier transmitted by a satellite, allowing the controlling engineers on Earth to monitor telemetry data or track the satellite.

　　Beamwidth - The angle or conical shape of the beam that the antenna projects. Since larger antennas have narrower beamwidths, they can pinpoint satellites in space or in dense traffic areas on the earth with more precision.

　　Bell 103 - This is an AT&T specification for a modem at speeds of up to 300 bps (bits per second). This is the most common standard for modems in PCs.

　　Bell 201 - The AT&T standard for 2400 bps modems.

　　Bell 202 - The AT&T standard for 1800 bps modems.

　　Bell 208 - The AT&T standard for 4800 bps modems.

　　Bell 209 - The AT&T standard for 9800 bps modems.

　　Bipropellant - Propellants are the fuel used in satellite propulsion systems. Bipropellant means that two fuels are used.

　　BISYNC - This refers to bisynchronous transmission.