A scheduling service and user interface that is available as a common resource with the Windows 98 operating system. Windows 98 includes Task Scheduler as a Component Object Model (COM) interface. Task Scheduler manages all aspects of job scheduling: starting jobs, enumerating currently running jobs, tracking job status, and so on. The Task Scheduler replaces the Windows 95 System Agent.
A category to which individual television programs are assigned within the Guide database. A theme allows a program episode to be associated with multiple genre/subgenre pairs.
time to live
(TTL) A value in the range 0 through 255 that defines the scope within which multicast packets should be sent over a network using Internet Protocol (IP). The scope is defined in terms of how local or remote a packet's destination is. Each router decrements the TTL by one. When the value reaches a predefined lower limit, the router throws the packet away. Current multicast backbone (MBONE) requirements, available at the ftp://ftp.isi.edu/mbone/faq.txt site, define the following standard scopes: local network, 1; local site, 15; region, 63; world, 127. Other settings may have local meaning; for example, 31 might indicate all sites within a particular organization.
timeslice
A set length of time on a particular television channel. This length of time is independent of the shows displayed during that period. For example, you can define a "Saturday Morning Cartoon" timeslice that runs from 7 A.M. to noon. This timeslice does not correspond to any one cartoon show; instead, it encompasses them all. Timeslices are used by timeslice announcements.
timeslice announcement
Timeslice announcements contain information about an enhancement that enhances the current television channel for a set length of time, or timeslice.
transform filter
A filter that modifies the contents of a stream. Transform filters usually have both input and output pins.
Transmission Control Protocol/Internet Protocol
(TCP/IP) A networking protocol that provides reliable communications across interconnected networks made up of computers with diverse hardware architectures and operating systems. The TCP portion of the protocol, a layer above IP, is used to send a reliable, continuous stream of data and includes standards for automatically requesting missing data, reordering IP packets that might have arrived out of order, converting IP datagrams to a streaming protocol, and routing data within a computer to make sure the data gets to the correct application. The IP portion of the protocol includes standards for how computers communicate and conventions for connecting networks and routing traffic. See also User Datagram Protocol/Internet Protocol (UDP/IP).
transponder
A device on a satellite that receives and amplifies uplink signals in radio frequencies that come from an earth station. Once the signal is received, the transponder redirects it back toward its destination earth station within the particular satellite's footprint. Each transponder is responsible for a small frequency range, and a satellite is typically made up of 10 to 40 transponders. Unlike in traditional broadcast television, each transponder has enough bandwidth to carry multiple television channels, as well as data. Any one transponder might carry anywhere from 10 low-resolution television channels to 2 high-definition television (HDTV) channels, or some combination. See also multiplexer.
transport layer
The fourth of the seven layers in the International Organization for Standardization's Open Systems Interconnection (OSI) model for standardizing computer-to-computer communications. The transport layer is one level above the network layer and is responsible for error detection and correction, among other tasks. Error correction ensures that the bits delivered to the receiver are the same as the bits transmitted by the sender, in the same order and without modification, loss, or duplication. The transport layer is the highest of the three layers (data link, network, and transport) that help move information from one device to another. See alsodata link layer.
trigger
A notification that is sent to a broadcast client at specific times during an interactive television show to change enhancement display on the client. For example, you can use triggers to automatically change the content of an enhancement, as in an advertisement rotator.
Trigger Receiver Control
Windows 98 OSR1 and later: An ActiveX control that resides on the broadcast client and that handles enhancement events such as file transmissions and triggers. This control is provided with Broadcast Architecture.
Windows 98: This version of Broadcast Architecture does not use the Trigger Receiver Control. Instead, it uses the Enhancement control.
tuner
An electronic device that locks onto a selected channel and filters signals such as audio and video from that frequency for amplification and display.
tuning space
A set of nonoverlapping channels that are all available through the same type of physical channel tuner, such as a broadcast receiver card or analog cable tuner. A broadcast client with multiple tuning devices can provide channels from multiple tuning spaces.
twisted-pair cable
A communications medium consisting of two thin, insulated wires, generally made of copper, that are twisted together. Standard telephone connections are often referred to as "twisted pair."