T/R

Transmit/Receive.

T.P

Telephony Tap - A device that channels specific amount of energy out of the main distribution system to a secondary outlet.

Tape Wrap

A spirally applied tape over an insulated or uninsulated wire.

TC

Telecommand (control of a satellite).

TDA

Tunnel Diode Amplifier (early type of LNA).

TDF

French DBS satellite system.

TDM (2)

Turner/Demodulator (i.e., indoor Unit). often referred to as the receiver.

TDM (1)

Time Division (or Domain) Multiplex.

TDMA

Time Division Multiple Access.

Tear Strength

The force required to initiate or continue a tear in a material under specified conditions.

Teletext

Broadcast Videotex An on-screen text information service transmitted in digital formal using spare lines in the VBI of a TV signal.

Teletex

A textual data transmission system, linking word processing terminals.

Television Receive-only (TVRO)

A satellite system that can only receive but not transmit signals.

Telex X

Nordic DBS satellite system.

Telex

A telegraphic text transmission system, linking teleprinters.

Tensile strength

The pull stress required to break a given specimen.

Thermal Noise

Random, undesired electrical signals caused by molecular motion, known more familiarly as noise.

Three-axis stabilization

Type of spacecraft stabilization in which the body maintains a fixed attitude relative to the orbital track and the earth's surface. The reference axes are roll, pitch, and yaw, by nautical analogy.

Threshold

A minimal signal to noise input required to allow a video receiver to deliver an acceptable picture.

Threshold Extension

Techniques for reducing the CNR value at which threshold effects occur.

Thruster

A small rocket engine used during routine station keeping activities.

TI

Terrestrial Interference. Interference to satellite reception caused by ground-based microwave transmitting stations.

Tilt

The uneven attenuation of a broadband signal as it travels through a coaxial cable. In general, attenuation increases as signals frequency increases.

TM

Telemetry. Satellite status data transmission.

TOC

Technical Operations Center.

Torus

Parabolic Torus geometry of multiple beam antenna. Reflector has a circular profile along the orbital arc, and a parabolic profile across the are.

Trace

The movement of the electron beam from left to right on a television screen.

Traffic

The telecommunications signals passing through a transmission channel, especially telephony, data.

Transfer orbit

A highly elliptical orbit which is used as an intermediate stage for placing satellites into geostationary orbit.

Transmission Cable

Two or more transmission lines. If the structure is flat, it is sometimes called Flat Transmission Cable to differentiate it from a round structure such as a jacketed group of coaxial cables.

Transmission Line

Structure providing a (usually low-loss) pathway for a radio-frequency signal. In satellite communications, usually coaxial cable or waveguide.

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 pick up signals transmitted from earth, translates them into new frequencies and amplifies them before retransmitting them back to ground. 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.

Trap

An electronic device that attenuates a selected bank of frequencies in a signal. Also known as a notch filter.

Tray

A cable tray system is a unit or assembly of units or sections, and associated fittings, made of metal or other noncombustible materials forming a rigid structural system used to support cables. Cable try systems (previously termed continuous rigid cable supports) including ladders, troughs, channels, solid bottom trays, and similar structures.

Triaxial Cable

A cable construction having three coincident axes, such as conductor, first shield and second shield all insulated from one another.

Truncation

Loss or outermost side frequencies of an FM signal due to filtering. Shows as "tearing" effect of noise on video transients, sharp vertical edges.

TT & C

Tracking, Telemetry, and Command (or Control)

TTC&M

Tracking, Telemetry, Command and Monitoring. A satellite's controlling Earth Station.

TV-SAT

German DBS satellite system.

TVRO

A television receive-only earth station designed only to receive but not to transmit satellite communications.

TWT

Traveling - Wave Tube.

TWTA

Traveling - Wave Tube Amplifier.