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Glossary of Terms

Glossary of Terms

T.120
A standard for audio-graphics exchange. While H.320 does provide a basic means of graphics transfer, T. 120 will support higher resolutions, pointing and annotation. Users can share and manipulate information much as they would employ if they were in the same room though they are working over distance and using a PC platform. T. 120 will allow audio bridge manufacturers to add graphics to their products in support of a wide range of applications. This type of image is fairly easy to capture with compressed video because there is very little motion in a talking head image and most occurs in facial expression and torso movement.
T1
The transmission bit rate of 1.544 millions bits per second. This is also equivalent to the ISDN Primary Rate Interface for the U.S. The European T1 or E1 transmission rate is 2.048 million bits per second.
T3 Channel (DS-3)
In North America, a digital channel which communicates at 45.304 Mbps.
Tagged Image File Format
Graphics format used primarily for scanned images that are generally not incorporated into the host document but instead are "tagged" for printing when the host document is printed.
TBC
For Time-Base corrector; a device used to stableize and synchronize multiple video signals, as in a video studio where the output of a videotape recorder must be dissolved to a live on-camera shot.
TDMA
Time division multiple access. Refers to a form of multiple access where a single carrier is the shared by many users. Signals from earth stations reaching the videoconference consecutively are processed in time segments without overlapping.
TELCO
Generic term for telephone company. Can refer to an Interexchange Carrier or to the Local Exchange Carrier.
Telecommunications
An electronic method of transmitting information from one location to another over a telephone network.
Teleconference
A meeting of geographically separated people who may have two-way audio, video, and text communications often via telephone and/or closed-circuit television.
Television
The technical equipment and events involved in creating television productions. The picture portion of a television broadcast.
Terminal
A device typically having a keyboard and display that is capable of sending text to and receiving text from another device, a network, etc.
Termination
A load, or impedance at the end of a cable or signal line used to match the impedance of the equipment that generated the signal. The impedance absorbs signal energy to prevent signal reflections from going back toward the source. In the video industry, termination impedance is typically 75 ohms.
Terminator
A device that provides termination for a signal line, or several signal lines, at the end of a cable. Usually a close-tolerance resistor for each signal, a terminator is often mounted in its own connector making it easy to install.
Test Generator
See Signal Generator.
TFT
Acronym for Thin Film Transistor; technology used with LCD screens, also known as Active Matrix.
Thin Film Transistor
A technology used to make Active Matrix LCD panels wherein each imagesel has its own transistor switch. See "Active Matrix".
Throw
The distance from projector lens to screen.
TIFF
Acronym for Tagged Image File Format.
Time Base Corrector
VTR playback circuitry used to smooth out the wavering edges of a video image.
Time Base Error
Slight errors in the line-to-line position of video information which occur between recording and playback. At the time of playback, these appear as serrations, tending to make the edges of the image waver.
Time Base Generator
A sync generator which puts a clock signal on the video tape to refer to for precise horizontal lock-up of an image.
Time Code
A digital or binary code used to label each frame of a video signal. This is very useful for editing the video since the time code is in the form of hours, minutes, seconds and frames.
Tint
See "hue", A relative measure of the amount of white in a given color.
Toggle
To switch over to an alternate state - from on to off, for example.
Toggle Switch
An electronically charged circuit holding either of two states - on or off, for example. The state does not change until the circuit is directed to the alternate state.
Touch Panel
A control panel with a flat surface (usually marked off) that functions as switches or controls. May also be called "touch screen".
Touchscreen
A display screen that acts as an input device by responding to the touch of the user.
Trace
The visible shapes drawn on a CRT by the movement of the electron beam. Trace lines are also known as video lines on a CRT.
Transducer
A device that converts a specific physical quantity such as sound, pressure, strain, or light intensity into an electrical signal.
Transistor to Transistor Logic
Digital type signal, usually 4-5 volts peak-to-peak. Distance limitation is 6-10 feet. Signal splitting is acceptable. TTL signals are either "ON" or "OFF" and is characteristic of low resolution computers (CGA/EGA).
Transmissive Overhead Projector
A type of overhead projector that has its light source in the base of the unit rather than in the upper lens housing (as in a reflective overhead projector).
Transmitter (Tx)
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.
Transport Protocol
Reliable and effifient end-to-end transport service between user process.
Trigger
The circuit that initiates a horizontal sweep on an oscilloscope and determines the beginning point of the waveform.
Tripple Super Twist Nematic
Color LCD technology which involves stacking 3 monochrome LCD's (cyan, magenta, yellow), using a subtractive color process involving gray scale algorithms to produce a full spectrum of colors. (Triple Super Twist Nematic).
TSTN
Acronym for Triple Super Twist Nematic.
TTL
Acronym for Transistor to Transistor Logic.
Tweak
To adjust or fine-tune.
Tweeker
A tiny screwdriver for making sensitive adjustments to audio visual and computer equipment.
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