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Glossary
IP Internet Protocol: The IP part of TCP/IP. IP implements the network
layer (layer 3) of the protocol, which contains a network address and
is used to route a message to a different network or sub-network. IP
accepts packets from the layer 4 transport protocol (TCP or UDP),
adds its own header to it and delivers a datagram to the layer 2 data
link protocol. It may also break the packet into fragments to support
the Maximum Transmission / Transfer Unit (MTU) of the network.
I-picture; I-frame Intracoded Picture/Frame: A picture / frame, which is coded using
purely intracoding with reference to no other field or frame
information. The I frame is used as a reference for other
compression methods.
IPPV Impulse Pay Per View: One-time events, purchased at home (on
impulse) using a prearranged SMS credit line.
IRD Integrated Receiver Decoder: The Receiver with an internal MPEG
Decoder, which is connected to the subscriber’s TV. The IRD is
responsible for receiving and de-multiplexing all signals. The unit
receives the incoming signal and if CA is active, decodes the signal
when provided with a control word by the viewing card. Domestic
IRDs are also known as Set-Top Units or Set-Top Boxes.
IRE Institute of Radio Engineers: No longer in existence but the name
lives on as a unit of video amplitude measurement. This unit is 1%
of the range between blanking a peak white for a standard
amplitude signal.
ISDN Integrated Services Digital Network: The basic ISDN service is BRI
(Basic Rate Interface), which is made up of two 64 kbps B channels
and one 16 kbps D channel (2B+D). If both channels are combined
into one, called bonding, the total data rate becomes 128 kbps and
is four and a half times the bandwidth of a V.34 modem (28.8 kbps).
The ISDN high speed service is PRI (Primary Rate Interface). It
provides 23 B channels and one 64 kbps D channel (23B+D), which
is equivalent to the 24 channels of a T1 line. When several channels
are bonded together, high data rates can be achieved. For example,
it is common to bond six channels for quality videoconferencing at
384 kbps. In Europe, PRI includes 30 B channels and one D
channel, equivalent to an E1 line.
ISO
International Standards Organisation.
ISOG
Inter-union Satellite Operations Group.
ITS Insertion Test Signal: A suite of analogue test signals placed on
lines in the VBI. Also known as VITS.
ITT
Invitation To Tender.
ITU-R International Telecommunications Union - Radiocommunications
Study Groups (was CCIR).
ITU-T International Telecommunications Union - Telecommunications
Standardization Sector (was CCITT).
EN/LZT 790 0003/2 R1A
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