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Glossary

Term Description

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.

HSSI High Speed Serial Interface: A differential ECL serial interface standard

developed by Cisco Systems and T3plus Networking primarily for use in

WAN router connections. It is capable of speeds up to 52 Mbit/s with

cables up to 50 feet in length. While HSSI uses 50-pin connector physically

similar to that used by SCSI-2, it requires a cable with an impedance of

11 Ω (as opposed to the 75 Ω of a SCSI-2 cable).

IEC International Electrotechnical Committee.

IF Intermediate Frequency: A frequency, commonly 70/140 MHz, to which a

carrier frequency is shifted as an intermediate step in transmission or

reception. The intermediate frequency is created by mixing the carrier

signal with a local oscillator signal, resulting in a signal at the difference

frequency.

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.

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.

ISDN Integrated Services Digital Network: The basic ISDN service is BRI (Basic

Rate Interface), which is made up of two 64 kbit/s B channels and one 16

kbit/s D channel (2B+D). If both channels are combined into one, called

bonding, the total data rate becomes 128 kbit/s and is four and a half

times the bandwidth of a V.34 modem

(28.8 kbit/s).

The ISDN high-speed service is PRI (Primary Rate Interface). It provides 23

B channels and one 64 kbit/s 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 kbit/s. In

Europe, PRI includes 30 B channels and one D channel, equivalent to an

E1 line.

ISO International Standards Organisation.

ITU-R International Telecommunications Union - Radiocommunications Study

Groups (was CCIR).

ITU-T International Telecommunications Union - Telecommunications

Standardisation Sector (was CCITT).

B-6 SBM75e Series Modulator Installation and Operation Manual

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