lead signaling -Method of
signaling using dual connection ports
""M""). When a signal reaches a
switch, it enters through the E lead. Switches send
signals out through the M lead.
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.
Connectivity - Signals
are in digital form during their entire path through the
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
Fiber optic cable - A cable technology that
carries light signals over thin glass fiber at unlimited
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
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 ).
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.