Broadband Cable Association of Pennsylvania

Glossary - I

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Impedance - Resistance to alternating-current flow.

Impulse Noise - Short bursts of high-level noise such as that resulting from the coupling of transients into a channel. Typical sources of such noises are lightning and transients from switching systems. Impulse noise, which sounds like a click, is not particularly detrimental to voice communications, but it can be detrimental to data communications.

Incremental Related Carriers (IRC) - A method of spacing National Television Systems Committee (NTSC) television channels on a cable television system in which all channels except 5 and 6 correspond to the standard channel plan, used to reduce composite triple beat distortions.

Incumbent Local Exchange Carrier (ILEC) - This term refers to traditional local telephone companies such as one of the Regional Bell Operating Companies (RBOCs) in the United States.

Independent - A TV station that has no exclusive affiliation which obliges it to carry programs from one of the national networks. Individually-owned and operated cable television system, not affiliated with a Multiple System Operator.

Independent Operator - Individually owned and operated cable television system, not affiliated with an MSO.

Inductor - An electronic component designed to provide a controlled amount of inductance.

Infomercial - A commercial, usually 90 seconds or more in length, designed to supply information about a product or service rather than to present a specific sales message.

Inline Package - A housing, for amplifiers or other cable television components, designed for use without jumper cables; cable connectors on the ends of the housing are in line with the coaxial cable.

Interference rejection - Reception of unwanted signals is interference; smart antenna systems reject interference by nulling the unwanted signal through phase shifting; they also reduce interference to other systems by nulling the transmitted signal in the direction of the unintended receiver.

Insertion Loss (IL) - Additional loss in a system when a device such as a directional coupler is inserted; equal to the difference in signal level between input and output of such a device.

Institutional Network - A network that is operated in conjunction with a cable TV system and which is designed to satisfy the needs of schools, businesses, or government.

Integrated Services Digital Network (ISDN) - ISDN is a digital telephone line that can be used for voice, fax, and data communications like a regular telephone line, but can transport data five times faster (or more) than a 28.8Kbps V.34 modem and allow you to talk on the phone to one person while sending data to another.

Interactive Cable - Cable systems that have the technical ability to let subscribers communicate directly from their television sets with a computer at the system headend using special converters and regular cable lines. Viewers are able to order movies and video games, access library information, and request sales brochures and coupons from home.

Interchangeability - The ability to exchange tapes between different manufacturers' videotape recorders with no appreciable degradation of playback image.

Interconnect - Two or more cable systems distributing a programming or commercial signal simultaneously.

Interference - Energy which tends to interfere with the reception of the desired signals, such as fading from airline flights, RF interference from adjacent channels, or "ghosting" from reflecting objects such as mountains and buildings.

Interlacing - The television display format, where horizontal lines of pixels are illuminated in an alternating pattern rather than sequentially.

Intermodulation - In a receiver, an unwanted signal sometimes interacts with the desired signal. The desired signal appears to be modulated by the undesired signal.

Intermodulation Distortion - Form of interference involving the generation of interfering beats between two or more carriers according to the frequency relationship f=n f1± mf2, where n and m are whole numbers (but not zero), with appropriate expansion for additional carriers.

International Organization for Standardization (ISO) - An international standards body, commonly known as the International Standards Organization.

Internet - A series of interconnected local, regional, national and international networks, linked using TCP/IP. The Internet is accessible via telephony wires, HFC networks and by satellite.

Internet Service Provider (ISP) - A company that sells Internet access.

Internet Protocol (IP) - The computer network protocol (analogous to written and verbal languages) that all machines on the Internet must know so that they can communicate with one another. It also is the network layer of TCP/IP which controls the flow of data packets.

IP Address - A 32-bit number that uniquely identifies a computer on the Internet to other host computers, used to route data packets to their intended destination. Displayed in the form of four groups of numbers from 0 to 255 separated by dots (e.g.,

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