E1 - 2.048 Mbps.

E-box - Electronics box ( the main codec box ) of a group videoconferencing system.

Echo-cancellation - Process which attenuates or eliminates the acoustic echo effect on videoconference calls. 

Echo suppression - To reduce echoes in the audio portion of a conference, it silences all sound when on by temporarily deadening the communication link in one direction. Unfortunately, not only the echo is stopped but also the remote end's new speech, which results in clipping.

Encryption - The conversion of data into a form, called a cipher, that cannot be easily understood by unauthorized people. 

End-to-End Digital Connectivity - Signals are in digital form during their entire path through the network.

Ethernet - A commonly used platform for transmitting information across a local area network.  Ethernet is a bus-based topology, nodes are connected to a single cable with terminators at each end. Transmits data at 10 Mbps, 100 Mbps, or gigabit over twisted pair wire or coaxial cable.

FAS - Frame Alignment Signal in H.221.

FCIF - Full-CIF. Another name for CIF.

FEC - Forward Error Correction. Method to prevent/fix bitstream errors.

FECC - Far-End Camera Control.

Fiber Distributed Data Interface ( FDDI ) Network Services ( FNS ) - An all fiber network service that connects subscriber's LANs at their full speeds in select metropolitan areas, via a shared 100 Mbps fiber backbone.

Fiber optic cable - A cable technology that carries light signals over thin glass fiber at unlimited speeds.

Field - One-half of a video frame in the interlaced NTSC or PAL standards. A field contains all of the even or odd lines. In the 30 frames per second NTSC world, each field is displayed at 1/60 of a second intervals. In the PAL world, the interval is 1/50 of a second.

File Transfer Protocol ( FTP ) - The first and the most fundamental way to transfer files to and from remote computer sites. " Anonymous ftp " refers to being able to access public file archives without a password.

Fixed Point - Integer precision arithmetic. Numbers are typically represented by 16 or 32 bits.

Floating Point - Fractional precision arithmetic. Numbers are typically represented by 32 or more bits.

Four-wire circuits - Telephone lines using two wires for transmitting and two wires for receiving offering much higher quality than a 2-wire circuit. All long distance circuits are 4-wire. Almost all local phone lines and analog phones are 2-wire.

Fps - Frames per second ( video ).

Fractional T-1 or T-3 line - A T-1 or T-3 digital phone line in the North American T-carrier system that is leased to a customer at a fraction of its data carrying capacity and at a correspondingly lower cost. A T-1 line contains 24 channels, each with a data transfer capacity of 64 Kbps. 

Frame rate - Frequency in which video frames are displayed on a monitor, typically described in frames-per-second (fps). Higher frame rates improve the appearance of video motion.

Frame relay - A high-speed packet switching protocol used in wide area networks ( WANs ).  Provides service up to rates of 45 Mbps and is suited for data, image, and voice transfer.  Method for sending high-bandwidth data in frames ( not video frames but " blocks " of data ).

Frequency Division Multiplexing (FDM) - Most common method of multiplexing analog signals.

Full-duplex audio - Two-way audio may be captured and reproduced simultaneously. With full-duplex audio, the microphone may capture local audio for transmission while the far end audio may be heard clearly. Interruptions and doubletalk are possible.

Full-motion - In compressed video, picture quality that is generally acceptable to users although not of broadcast quality; typically from 10 — 30 frames per second depending on the bandwidth allocated.