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 electro
magneticspectrum, 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
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