T-1

   A digital channel that communicates at a rate of 1.544 million bits per second.

T-3 (DS-3)

   A digital channel which communicates at a significantly faster rate than T-1 (44,736 kbit/s).

Telecourse

   A video-based course which uses a fully integrated package of video instruction combined with instructional support materials (for example, a textbook, a student study guide, and a faculty resource guide). Telecourses are delivered in a variety of ways, including television broadcast.

Telecommunications

   The science of information transport using wire, radio, optical, or electromagnetic channels to transmit receive signals for voice or data communications using electrical means.

Telephone Relay Service

   Telephone Relay Services (TRS) link people using a standard (voice) telephone with people using a device called either a Text Telephone (TTY) or Telecommunications Device for the Deaf (TDD). This device generally consists of a keyboard and display screen. Calls are routed through a communications operator who has both sets of equipment and who acts as the intermediary between callers.

Teleport/Uplink Station

   The dishes, receivers, transmitters and other equipment on the ground that is needed to send and receive satellite signals.

Teleweb

   A course which merges a telecourse (see above) with the internet, providing the addition of online content, instructional/learning activities, resource links, and instructor and student interaction.

Text Equivalent

   Text content that describes information on the screen that’s contained in graphic, Flash, or other multimedia files. Text equivalent is often provided using captions, ALT text, or transcripts. The alternate text must convey the same function or purpose for the user with a disability as the non-text content does for others.

Text-to-Speech Software

   Text-to-Speech software is used to convert words from a computer document (e.g. word processor document, web page) into audible speech spoken through the computer speaker. This differs from screen reader technology because it doesn’t read any system information or alternative text descriptions.

Text Transcript

   A text description of information contained in audio files.

Transmission Control Protocol (TCP)

   A protocol which makes sure that packets of data are shipped and received in the intended order.

Transmitter

   An electronic device consisting of oscillator, modulator and other circuits which produce a radio or television electromagnetic wave signal for radiation into the atmosphere by an antenna.

Transponder

   A combination receiver, frequency converter, and transmitter package, physically part of a communications satellite. Transponders have a typical output of five to ten watts, operate over a frequency band with a 36 to 72 megahertz bandwidth in the L, C, Ku, and sometimes Ka Bands or in effect typically in the microwave spectrum, except for mobile satellite communications. Communications satellites typically have between 12 and 24 onboard transponders although the INTELSAT VI at the extreme end has 50.

TTY

   Most deaf people use a device called a TTY (also known as a TDD), which is a simple keyboard that connects to a telephone, often through an acoustic coupler. When two people communicate via TTY, each sees what the other is typing.

TWT (Traveling-wave tube)

   A microwave tube of special design using a broadband circuit in which a beam of electrons interacts continuously with a guided electromagnetic field to amplify microwave frequencies.

TWTA (Traveling-wave-tube-amplifier)

   A combination of a power supply, a modulator (for pulsed systems), and a traveling-wave tube, often packaged in a common enclosure.