A

ActiveX control

A reusable software component that can add specialized functionality to Web sites, desktop applications, development tools, and interactive video programs. These controls typically provide user interface elements, such as buttons. ActiveX controls were previously known as OLE custom controls or OCXes.

Address Reservation Service

(ARS) A service that maintains a database of what Internet Protocol (IP) addresses are available to broadcast head end applications and which addresses have been reserved by head-end applications.

Address Resolution Protocol

(ARP) The protocol that maps Internet Protocol (IP) addresses to the physical hardware addresses of specific networks. This protocol operates at the level of network operating systems and is not generally accessible to applications.

ADSL

See Asymmetrical Digital Subscriber Line.

Advanced Power Management

(APM) 1. A software interface defined by Microsoft and Intel that operates between hardware-specific power management software, such as that located in a computer's basic input/output system (BIOS), and the operating system's power management driver. 2. An abridgment of the title of the APM BIOS Interface Specification.

analog television tuner card

A type of broadcast receiver card that receives and processes analog video signals.

analog video

Video transmitted by an analog signal, such as an NTSC, PAL, or SECAM transmission.

announcement

In IP multicasting, content providers send out short announcements on a well-known multicast address and port. The announcement contains information about an upcoming broadcast and tells clients where to listen to receive the data. Broadcast Architecture announcements use the SAP/SDP format defined by the Internet Engineering Task Force (IETF)and incorporated in the ATVEF specification.

announcement filter

In the Announcement Listener, one of a collection of Automation servers that implement the IBroadcastFilter interface. An announcement filter distinguishes between announcements that are of interest to a particular broadcast client's user and those that are not. Multiple filters can exist for different kinds of data; for example, in Broadcast Architecture, Internet channel broadcasting and enhancements each have their own filters.

Announcement Listener

A operating-system service that receives announcements of upcoming data. Using Announcement Listener, the broadcast client can filter incoming data at the network interface (that is, at the broadcast receiver card) so the client only receives data of interest.

APM

See Advanced Power Management.

application layer

The seventh and highest layer in the International Organization for Standardization's Open Systems Interconnection (OSI) model. The application layer contains the signals sent during interaction between user and application and that perform useful work for the user, such as file transfer. See also data link layer, transport layer.

ARP

See Address Resolution Protocol.

Asymmetrical Digital Subscriber Line

(ADSL) A technology that allows data to be sent over ordinary twisted-pair telephone lines at T1 trunk-line speeds, currently up to 1.544 megabits per second, and to be returned at a current rate of 16 kilobits per second. ADSL provides a bidirectional voice signal while data is sent.

ATVEF

The Advanced Television Enhancement Forum. An industry group that has proposed a standard for the formatting and delivery mechanisms of television enhancements, announcements and triggers. Broadcast Architecture provides native support for sending and receiving ATVEF-compliant enhancements.