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Annex A
GUI Graphical User Interface: The use of pictures rather than just words
to represent the input and output of a program. A program with a
GUI runs under a windowing system and has a screen interface
capable of displaying graphics in the form of icons, drop-down
menus and a movable pointer. The on-screen information is usually
controlled / manipulated by a mouse or keyboard.
HDTV
High Definition Television.
HPA High Power Amplifier: Used in the signal path to amplify the
modulated and up-converted broadcast signal for feeding to the
uplink antenna.
HSYNC
Horizontal (line) SYNCs.
HTTP HyperText Transfer Protocol. The fundamental protocol used on the
Internet for transmission of WEB pages and other data between
servers and PCs
HU
Height Unit
Hub A device in a multi-point network at which branch nodes
interconnect.
ICAM Integrated Conditional Access Module: Embedded in the IRD and
responsible for descrambling, plus packet filtering and reception. It
also contains the physical interface to the subscriber’s viewing card.
ICMP Internet Control Message Protocol. ICMP messages, delivered in IP
packets, are used for out-of-band messages related to network
operation or mis-operation
IGMP
Internet Group Management Protocol. IGMP is a protocol used to
manage multicasts on the Internet. For a host (receiver unit) to
receive a multicast, it needs to transmit IGMP "join" messages on
the right format. Three versions exist. IGMPv2 is common today but
IGMPv3 is the next step.
IDU
Indoor unit
IEC
International Electrotechnical Committee.
IF Intermediate Frequency: Usually refers to the 70 MHz or 140 MHz
output of the Modulator in cable, satellite and terrestrial transmission
applications.
Interframe Coding Compression coding involving consecutive frames. When
consecutive frames are compared, temporal redundancy is used to
remove common elements (information) and arrive at difference
information. MPEG-2 uses B and P frames, but since they are
individually incomplete and relate to other adjacent frames, they
cannot be edited independently.
Intraframe Coding Compression coding involving a single frame. Redundant
information is removed on a per frame basis. All other frames are
ignored. Coding of a macroblock or picture that uses information
only from that macroblock or picture. Exploits spatial redundancy by
using DCT to produce I frames; these are independent frames and
can be edited.
EN/LZT 790 0005 R1A
A-8