Fade - This is a reduction in the received signal. It is caused by absorption, refraction, or reflection.

　　Fax - This is a shortening of Facsimile, and it refers to one fax machine sending a digital representation of a hardcopy over the phone lines to be received and printed out by another fax machine.

　　FCC - see Federal Communications Commission

　　F/D - the ratio of antenna's focal length to the antenna's diameter. If there is a greater F/D it means there is a shallower dish.

　　FDM - see Frequency Division Multiplexing.

　　Feature - This term refers to any of the tasks that a particular piece of equipment can perform or carry out.

　　Feed - this (1) describes the physical feed system of the antenna, and (2) describes the actual signal transmission of the data or information from the distributors.

　　Feedback - This occurs when part of the output signal returns to the input side of the electronic device.

　　Federal Communications Commission (FCC) - This is the government agency that regulates all interstate communications that originate within the United States. The FCC has no intrastate authority.

　　Field - This refers to the particular location of a piece of data within a record (which is within a file of a database).

　　File - This term refers to any intended collection of data with similar characteristics. A file could be anything from a document to a component of a computer program.

　　Filter - This is a device which allows a particular spectrum (range of frequencies) to pass through it but prohibits (attenuates) all others from passing.

　　Firewall - This is a system of both software and hardware, and it has purpose of limiting the vulnerability of a computer or set of computers from outside attack (i.e., hacking).

　　Flash - This is a function on a telephone or other phone device that rapidly hangs-up and reconnects the telephone line.

　　Flag - In programming, this is a variable that is used to relay when a particular condition of the program has been met.

　　Flow Control - This is a method of controlling the transfer of information (messages, characters, etc.) between a network's data points.

　　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 electromagneticspectrum, expressed in Hertz, in which satellite signals are transmitted.

　　Frequency Coordination - A process that is implemented to attenuate frequencyinterference between different satellitenetworks.

　　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 carrierfrequency (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.

　　补充：

　　FAQ - An acronym for Frequently Asked Questions. FAQs are online documents that list and answer the most common questions on a particular subject.

　　Federal Excise Tax - A 3% tax mandated by the federal government imposed on all telecommunications services including local, long distance and wireless bills.

　　Federal Subscriber Line Charge - This is a charge paid by consumers implemented by the Federal Communications Commission (FCC). It is intended to recover some of the costs associated with a customer's local telephone line to access the interstate long distance network. It helps keep interstate long distance rates low. You pay this charge whether or not you actually make long distance calls.

　　FCC - Federal Communications Commission. A United States government board made up of five presidential appointees that has the authority to regulateinterstate telecommunications, as well as international communications that originate or terminate in the U.S.

　　File Transfer Protocol (FTP) - A common method for sending and/or receiving files between Internet sites using a login system. Publicly accessed FTP sites are often called anonymous FTPs.

　　Firewall - A combination of hardware and software used to separate a LAN into two separate parts for security reasons.

　　Frequency - A certain "size" of radio wave: The rate at which the electric and magnetic fields of a radio wave vibrate per second.

　　FTTP (Fiber to the Premises) - A fiber-optic network that connects directly from the carriernetwork to the user premises. Another fiber-optic network is FTTC (Fiber to the Curb) that connects from the carriernetwork to the curb, and from there to the premises by copper wire or coaxial cable.

　　Facilities Based Private Switched Network Services

　　Facilities Based Private Switched Network Services is a private network for which LECs and IXCs dedicate physical switching and transmission facilities for the exclusive use of a particular customer.

　　Fast Packet

　　Fast Packet is a term referring to a number of broadband switching and networking paradigms. Implicit is the assumption of an operating environment that includes reliable, digital, broadband, nearly error free transmission system.

　　FCC Federal Communications Commission

　　The FCC is a board of commissioners empowered by the U.S. Congress to regulate all interstate and international communications, as well as use of the radio frequency media.

　　FDDI

　　fiber-distributed data interface

　　FDL

　　facility data link

　　FDM

　　frequency division multiplexing

　　FEP

　　front-end processor

　　FIPS

　　Federal Information Processing Standard

　　Foreign Exchange (FX)

　　FX is a service that provides a circuit(s) between a user station, a PBX, or a Centrex switch, and a central office other than the one that normally serves the caller.

　　Frame

　　In time division multiplexing systems, Frame is a sequence of time slots each containing a sample from one of the channels carried by the system. The frame is repeated at regular intervals, (normally the sampling rate used in analog-to-digital conversion processes for signals being multiplexed) and each channel usually occupies the same sequence position in successive frames.

　　Frame Relay

　　Frame relay is a network interface protocol defined in CCITT Recommendation 1.122 "Framework for additional packet mode bearer services," as a packet mode service. In effect it combines the statistical multiplexing and port sharing of X.25 packetswitching with the high speed and low delay of time division multiplexing and circuit switching. Unlike X.25, frame relay implements no layer 3 protocols and only the so-called core layer 2 functions. It is a high-speed switching technology that achieves ten times the packet throughput of existing X.25 networks by eliminating two-thirds of the X.25 protocol complexity The basic units of information transferred are variable length frames, using only two bytes for header information. Delay for frame relay is lower than for X.25, but it is variable and larger than that experienced in circuit switched networks. This means that currently frame relay is not suitable for voice and video applications where excessive and variable delays are unacceptable.

　　Frequency

　　Frequency is acoustic waves and electrical signals might be made up of only a single tone, like a single note on a piano. In this case the signal waveform is made up of repeating identical "cycles" and is said to be of a single frequency, equal to the number of cycles that occur in one second of time. In communications, frequency was traditionally expressed in cycles per second, but is now expressed in hertz (Hz), still equal to one cycle per second. Thus, one thousand cycles per second is equal to one thousand hertz, or a kilohertz (kHz).

　　Frequency Division Multiplexing (FDM)

　　FDM divides the frequency bandwidth (spectrum) of a broadband transmission circuit into many subbands, each capable of supporting a single, full time communications channel on a non- interfering basis with other multiplexed channels. FDM multiplexing is generally suitable for use with analog carriertransmission systems.

　　FSS

　　fully separated subsidiary

　　FTAM

　　file transfer access & management

　　Full Duplex

　　Full duplex is a transmission path capable of transmitting signals in both directions simultaneously.

　　FX

　　foreign exchange
关键字:电信专业英英词典
生词表: