电信专业英英词典F-2（在线收听）

　　Focal Length - Distance from the exact center of the dish to the center of the feed.

　　Focal Point - The physical point in space toward which the satellite reflector dish directs the received signal so it can be processed.

　　Format - This is (1) the general makeup and organization of a file, or (2) the arrangement of bits of characters within a group.

　　Forum - This is a section of a website or online service, wherein you can communicate with other forum members about a common subject.

　　Forward - This is the act of redirecting a particular email, an entire email address, or a telephone number.

　　Forward Error Correction (FEC) - The purpose of this element is to add unique codes to the digital signal at the output source so problems can be detected at the signal receiver.

　　Freeware - This is software that is free to use and distribute. Some freeware, though, requires that you don't make any changes or alterations to the code.

　　Frequency - The number of times that a wave or wave-like process goes through its complete cycle per second of time. Frequency is measured in hertz (Hz), which is one cycle per second.

　　Frequency Band - This is a particular band of frequencies in the electromagnetic spectrum, expressed in Hertz, in which satellite signals are transmitted.

　　Frequency Coordination - A process that is implemented to attenuate frequency interference between different satellite networks.

　　Frequency Division Multiplexing - This is an older method of dividing the bandwidth available for transmission into distinct narrow bands for individual transmission channels.

　　Frequency Modulation (FM) - The signal carries the desired information by varying the frequency of the carrier wave.

　　Frequency Shift Keying (FSK) - This is another modulation technique (see Frequency Modulation) used to transmit data. It shifts the frequency above and below the carrier frequency (representing 1 and 0, respectively).

　　Frequency Spectrum - This is a range of frequencies (and is similar to bandwidth).

　　FSK - see Frequency Shift Keying.

　　Full Duplex - This is the same as Duplex and is simultaneous transmission of data in two opposite directions.