I

ICP

Independent content provider. See content provider.

infrared

(IR) Defines a spectrum of electromagnetic radiation with frequencies in the spectrum less than those of visible light. Remote control units usually communicate with home televisions and VCRs by using infrared signals.

integrated receiver/decoder

(IRD) A subscriber terminal, such as the set-top box used for satellite television systems. In the case of Broadcast Architecture, the IRD is the broadcast receiver card.

Integrated Services Digital Network

(ISDN) A type of phone line used to enhance data transmission speed. Data can be transmitted over ISDN lines at speeds of 64 or 128 kilobits per second, whereas standard phone lines generally limit modems to top speeds of 20 to 30 kilobits per second. An ISDN line must be installed by the phone company.

interactive television

The combination of a video program and multimedia enhancement elements such as hypertext links, graphics, text frames, sounds, and animations.

interlacing

A video display technique, used in current analog televisions, in which the electron beam refreshes (updates) all odd-numbered scan lines in one field and all even-numbered scan lines in the next. Interlacing takes advantage of both the screen phosphor's ability to maintain an image for a short time before fading and the human eye's tendency to average subtle differences in light intensity. By refreshing alternate lines, interlacing halves the number of lines to update in one screen sweep. An alternative video display technique, used in computer monitors, is progressive scanning. In progressive scanning, the image is refreshed one line at a time.

Internet channel broadcasting

A technology to gather and redistribute Web content. Applications that use Internet channel broadcasting package a series of Web sites or channels and deliver them to broadcast clients at regular intervals.

Internet channel broadcasting is similar to the subscription model in Internet Explorer 4.0 and later. In both subscription models, a user subscribes to Web content that is then periodically updated in the user's cache. The models contrast in how they distribute subscribed-to content. Internet Explorer uses a pull model, in which the user's Web browser schedules periodic downloads of subscribed content. Such a download is a one-to-one transmission of data that uses a standard Internet connection.

In contrast, Internet channel broadcasting multicasts content to all users simultaneously, and client applications receive only channels to which users have subscribed. Such a broadcast is a one-to-many transmission of data that can occur over any transport medium that supports Internet Protocol, including a local area network, vertical blanking interval, and satellite.

Internet Channel Client

A component of the Windows 98 operating system that receives broadcast updates of Web sites that the user has subscribed to and stores the updated files in the Web browser cache. The client extends the Internet Explorer subscription model to a one-to-many broadcast architecture. See also Internet channel broadcasting.

Internet Protocol

(IP) The primary network layer of Internet communication, responsible for addressing and routing packets over the network. IP provides a best-effort, connectionless delivery system that does not guarantee that packets arrive at their destination or that they are received in the sequence in which they were sent. See also Transmission Control Protocol/Internet Protocol, User Datagram Protocol/Internet Protocol.

IP

See Internet Protocol.

IP multicast address assignment

The process by which transient Class D Internet Protocol (IP) multicast addresses are allocated. Each address must be assigned uniquely across the system for a specific time period. Once that time period elapses, the address returns to the available pool. In Broadcast Architecture, these addresses are used to identify data streams being broadcast, both at the head end and in broadcast client systems in the home.

IR

See infrared.

IR/D

See integrated receiver/decoder.

ISDN

See Integrated Services Digital Network.