T

TCO
Total Cost of Ownership; a way of accounting for the maintenance and other in-life costs of an installation, on top of the basic cost of purchasing the equipment.

TCP/IP
Transmission Control Protocol / Internet Protocol; a protocol used in the Internet to provide reliable communications over potentially unreliable links.

TDM/TDMA
Time Division Multiplex / Time Division Multiple Access; a system commonly used in large star topology networks.

TDMA
Time Division Multiple Access; A method by which a number of sites can share a single carrier frequency by transmitting at different times. As the sites do not always co-ordinate their transmissions sometimes two or more sites will transmit simultaneously (a collision). A reliable communications protocol is used to recover the lost data when this occurs.

Teleport
A, usually large, facility used to communicate with the satellite.

TVRO
Television Receive Only

Terrestrial
Pertaining to an Earth based system

Three axis stabilised satellite
A system for stabilising the body of a satellite. Typical three axis stabilised systems deploy large surface area 'wings' covered in solar panels to gather power.

Tracking
Moving an antenna such that the satellite remains in full view and the signal received from the satellite is maximal.

Transceiver
A transmitter and receiver combined in one unit

Transmitter
A device that takes the output from a modem, translates it up in frequency to the uplink frequency, and amplifies the signal prior to launching it into the antenna. The Transmitter incorporates the HPA.

Transponder
The functional unit in a satellite. The satellite normally carries several transponders as its payload. Each transponder comprises a frequency translator and an amplifier to convert the uplink signal into the downlink signal and boosting it before re-transmission to the Earth.