AV/IT Glossary—27 Days of #AVabc—T




HDBaseT—HDBaseT, promoted and advanced by the HDBaseT Alliance, is a consumer electronic (CE) and commercial connectivity standard for transmission of uncompressed high-definition video (HD), audio, power, home networking, Ethernet, USB, and some control signals, over a common category (Cat5e or above) cable with a standard connector (8P8C, often "RJ45").


t.120—CCITT standard for digital computer data interchange videoconferencing.

Tap—A fiber optic coupler with two outputs, the second of which, part of the incoming light is tapped off into another fiber.

TBC-Time Base Corrector—A device used to rectify the results of distorted sync* pulses which are due to mechanical faults (tape transport, tape stretch, etc.). TBCs are also used to synchronize two video sources to allow mixing. In the past, CCD* technology was used to move or alter a video signal in an analog* memory chip which was suitable for simple analog synchronization. However, CCDs had very limited memory capabilities. Therefore, digital TBCs are now common. They usually break down the video signal into its components. This is extremely flexible as it permits storage of a full frame or more in a digital memory device (RAM type chips). They operate in full bandwidth with 8 or more bit conversion schemes and are suitable for professional applications. In the digital domain a similar process is used, named reclocking, which restores stability of a digital signal by restoring the original clock signals and fixing the jittering signal with a stable time base.

TCP-Transmission Control Protocol—A method (protocol) used along with the Internet Protocol to send data in the form of message units between computers over the Internet. While IP takes care of handling the actual delivery of the data, TCP takes care of keeping track of the individual units of data (called a packet) that a message is divided into for efficient routing through the Internet.

TCP (Transmission Control Protocol)—A connection-oriented protocol designed to provide a reliable end-to-end data delivery over an unreliable internetwork.

TCP/IP-Transmission Control Protocol/Internet Protocol—The communication protocol of the Internet. Computers and devices with direct access to the Internet are provided with a copy of the TCP/IP program to allow them to send and receive information in an understandable form.

TCP/IP Model—A set of communications protocols used for the Internet and other similar networks. It is named from two of the most important protocols in it: the Transmission Control Protocol (TCP) and the Internet Protocol (IP). The eight functions of the OSI model have been combined into only four layers in the TCP/IP model.

Tee Coupler—A T-shaped fiber optic coupler with one input and two outputs.

Telecine—A device that converts film movies to video. The main problem in film-to-video conversion is the frame rate. In film movies it is 18 or 24 frames per second, which does not match the video frame rate of PAL or NTSC. For good conversion, interpolation and other techniques are used in the telecine device. In advanced telecine machines, film movie is sampled digitally and converted to video, frame after frame, in real-time. One of the most popular digital systems used in professional telecine machines is called flying-spot, which allows almost transparent conversion to video. The digital process is called pull down*.

Telecommunications—An electronic method of transmitting information from one location to another over a telephone network.

Telecommunications Closet—An enclosed, secure space for housing telecommunications equipment, cable terminations, and cross connects.

Teleconferencing—A meeting between people at two or more locations who can communicate by audio and/or visual devices often via telephone and/or closed-circuit television.

Telepresence—A set of technologies which allow a person to feel as if they were present, to give the appearance that they were present, or to have an effect, at a location other than their true location. Telepresence solutions include the delivery of audio, video, data and computer graphic information over IP networks using video over IP encoders and decoders.

Teleprompter—A device used in news casting for displaying large text on a partially transparent screen where the reader can look at the camera and read the text from the screen placed in front of the camera. In old systems, one person read the news, while the other rolled a transparent, long message banner in front of the camera. In modern Tele-prompter devices, the user does it with a mirrored computer screen that, in most cases, he controls himself.

Teletext—A service provided by some TV broadcasting stations, which transmits latent data information alongside the video signal. In order to retrieve the teletext information and display it on the screen, the TV receiver is equipped with a teletext decoder. The data information is usually encoded and inserted in the vertical-blanking interval. Corrupted teletext information often causes image instability and picture roll because it effects the video syncs.

Telnet—A computer network utility available on most PCs that allows the computer system to communicate with one of its remote users or clients. A user who wishes to access a remote system initiates a Telnet session using the address of the remote client. The user may be prompted to provide a user name and password if the client is set up to require them.

Temporal—Relating to the sequence of time or to a particular time.

Temporal Resolution—A measurement of elements occurring in time. Example: the temporal resolution of video may be 50 or 60 frames per second.

Ten Bit (10 Bit)—An expression used to describe a digital data stream of 10-bit width. A ten-bit digital word can have 1024 steps or values. Digitizing video at 10-bit resolution is acceptable for most broadcast specifications, as the 1024 recovered steps accurately represent the digitized signal. When an 8-bit stream of data is used, only 256 steps are recoverable.

Tensile Strength—The maximum force that a material can withstand before deforming or stretching.

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—1. 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. For video signals, termination impedance is typically 75 ohms; for sync signals, it is usually 510 ohms. 2. A connector at the end of a cable.

Termination Switch—A load device, usually a 75-ohm resistor, connected by a switch to a video transmission line to terminate the line. For a video signal be correctly transmitted without losses, proper impedance is essential at the end of the line. In many video-processing devices, a termination switch is therefore included as a standard feature. When the termination switch is in the Hi-Z position, the video signal is not terminated but looped to the next station. The signal can thus be transmitted in parallel through a number of devices. The termination switch terminates the final device.

Termination Tools—Tools used in the preparation and installation of connectors on cables or optical fibers.

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 enclosed connector, making it easy to install. In fiber optics, an optical plug used to fully terminate the optical path so no light is reflected back toward the source.

TFT—A Thin Film Transistor LCD panel. A type of LCD flat panel display screen in which each pixel is controlled by one to four transistors. The TFT technology provides the best resolution of all the flat panel techniques, but it is also the most expensive. TFT screens are sometimes called active matrix LCDs.

TGA/TARGA—A graphics file format initially developed for use with Truevision Targa/Vista graphics boards. This file format, with its variations, supports up to 32 bit formats. The images in the file can be either uncompressed or compressed with RLE (Run Length Encoding) compression format, and the file structure is very simple, reliable and suitable for file transfer and exchange between various computers.

THD-Total Harmonic Distortion—The amount of internally generated noise in a receiver that varies from the ideal sound wave. Since the perfect audio wave is physically impossible, the variation from the ideal wave is the percentage referred to as THD.

THD+N-Total Harmonic Distortion plus Noise—THD+n is a specification that includes both harmonic distortion of the sine wave and non-harmonic noise. THD+N tells the user what amount of hum, noise, and interference has been added to the audio signal by the equipment through which it is passing.

Thin Client—A computer or a computer program which depends heavily on some other computer (its server) to fulfil its traditional computational roles.

Third Octave—A term that refers to frequencies spaced three octaves apart. For example, the third-octave above 1 kHz is 8 kHz. Third-octave filters, typically in a bank between 20 Hz and 20 kHz, are useful because they have a good correlation to the subjective response of the human ear. Filtering broad spectrum pink noise through a third-octave filter is often used to characterize acoustical systems, such as loudspeakers, or for the measurement of absorption or damping of acoustical materials.

Three-Chip DLP—A DLP-based video display in which the image is created by three separate DMDs, one each for the three primary colors of red, green, and blue. Three-chip devices project the three colors simultaneously. All LCD and LCoS displays use three panels. Contrast with single-chip DLP in which the three primary colors are projected sequentially.

Three-Phase Power—Alternating current electrical power supplied by three current carrying conductors, each offset by 120 degrees from one another. A fourth conductor, a neutral, is used as the return conductor. This type of power is used for commercial and industrial applications.

Throw Distance—The length of the projection beam necessary for a particular projector to produce an image of a specified size.

THX—Originally part of Lucasfilm, Ltd., THX embodies a series of certification programs for equipment, software, production environments, and presentation venues with the objective of delivering optimum sound and video.

THX-Certified—An A/V product that correctly implements the THX technologies and meets stringent technical performance criteria for film-sound reproduction.

THX Surround EX—Original name for Dolby Digital EX.

Tiff—A widely used graphics file format for PC and Macintosh computers. This file format supports from monochrome up to 24-bit color and supports RGB through CMYK formats. Despite its popularity, the format is quite complex, and Tiff files created by one computer may be unreadable by another.

Tight Buffered Cable—A fiber optic cable for indoor use in which the buffer coating tightly surrounds the cladding for extra protection and provides color-coded identification.

Timbre—The tonal quality or characteristic of a sound.

Timbre Matching—A THX technology that ensures sounds arriving from the listener’s sides have the same timbres as sounds arriving from the front, in order to ensure smooth panning of sounds.

Time Base Corrector—Video tape recorder (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 that 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 videotape 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.

Time Division Multiplexing-TDM—A digital transmission scheme where the channel is divided into two or more time slots or subchannels, such that the subchannels are taking turns in the bit stream. Multiple digital signals are multiplexed into a serial digital stream. The serial digital stream is transmitted to the receiver where it is de-multiplexed into the individual digital signals

Time Domain—A means of representing a signal on a graph of amplitude (usually on the vertical axis) versus time (usually on the horizontal axis). An oscilloscope produces a time domain representation of a signal.

Time Shifting—Recording a television or DBS program for later playback.

Tint—A relative measure of the amount of white in a given color.

Titling—The superimposition of text on video footage. Titles are added to a video scene during or after the production. Sophisticated titling devices allow the user to prepare text and graphics in various sizes, fonts and colors which are later inserted, one-by-one, at the appropriate times and places. An entire feature film can be titled in this fashion. Many video cameras* either include built-in titlers or permit externally-produced titles to be mixed with the image produced by the camera while shooting.

TMDS-Transition Minimized Differential Signaling—An all-digital video transmission standard developed by Silicon Image, Inc. TMDS is the core technology used in DVI - Digital Visual Interface and HDMI - High Definition Multi-media Interface.

Toggle—To switch between alternate states. For example, between on and off, or caps and lower case.

Toggle Switch—A switch having two positions or two states. When an activating force is applied, the state changes.

Tonal Balance—Relative levels of bass, midrange, and treble in an audio component or audio presentation.

Toneburst—A group of short duration audio frequencies, from 20 Hz to 20 kHz, used to evaluate the behavior of a listening environment in response to loudspeakers. Toneburst is used to identify room reflections caused by resonance or standing waves. Also see "Room mode."

TOSLINK—An optical fiber connection standard for digital audio developed by Toshiba. TOSLINK is very commonly used for audio output from Compact Disc and DVD players, as well as some game consoles. A generic name, “EIAJ optical,” is sometimes used to describe this standard.

Total Harmonic Distortion (THD)—A measure of all the harmonic distortion components (i.e., second harmonic, third harmonic, etc.) produced by an audio device, expressed as a percentage of the fundamental signal. Called “total” because it is the sum of all the individual harmonic-distortion components created by the component.

Total Internal Reflection—The total reflection of light as it reaches a boundary between two optical media at an angle of incidence greater than the critical angle.

Touch Panel—A control panel with a flat surface (usually with graphic divisions or buttons) that functions as a switch or control. Also called a “touch screen.”

Touchpanel—A control panel with a flat surface (usually with graphic divisions or buttons) that functions as a switch or control. Also called a "touch screen."

TP-Twisted Pair—Cable that uses small twisted pairs of wires in a common jacket/sheath to transmit and receive network or telephone signals; can be either shielded (STP) or unshielded (UTP). The Extron product family includes twisted pair transmitters, twisted pair receivers, and twisted pair cabling.

Tracking—A method of controlling the mechanical position of the video head over the recorded material on video tape. Due to small differences in alignment of head-to-tape position in different VCRs, it is sometimes necessary to re-adjust the tracking control on one VCR when playing a tape that was recorded on another. Nowadays, most VCRs have an automatic, digital tracking system and no user intervention is required.

Transceiver—A device that can operate as a transmitter, receiver, or both.

Transcoder—An electronic device designed to convert one signal type to another, and vice-versa. For example, the Extron YCS Transcoder both decodes composite video into S-video, and encodes S-video into composite video.

Transducer—In audio, a device to convert sound to electrical energy or vice versa. Microphones and loudspeakers are two type of transducers. Microphones convert sound into electrical energy; loudspeakers convert electrical energy back into sound.

Transform—A transform is a method applied to convert a data set from one domain to another. The rationale for transforming the data into a new domain is typically to make handling and processing the information easier. One common example is the RGB to YUV color space transformation. Imagery collected from the real-world using sensors in done so in an RGB color space. The RGB information is then transformed to a component YUV domain allowing independent processing of luminance and color information.

Transformer—A transformer is used to bring voltage up or down in an AC electrical circuit. A transformer can be used to convert AC power to DC power. There are transformers all over every house, they are inside the black plastic case which you plug into the wall to recharge your cell phone or other devices.

Transformation—A change or alteration. In the context of still image compression, a picture frame is input as a fixed resolution of rows and columns of pixels and a transformation into a frequency domain applying the Discrete-Cosine Transform.

Transformer Taps—A transformer is a simple device that “transforms” electricity from one voltage to another. Transformers are added to conventional, 8 ohm loudspeakers to adapt them for use in constant voltage, multi-speaker distributed audio systems. The transformers are “tapped”, that is, designed with several different output points, to allow for different output wattages from the 70 V or 100 V constant voltage input. Taps are typically spaced at 2x increments, for example, 2 watts, 4 watts, 8 watts, 16 watts, etc.

Transient Disturbance—A momentary variation in power such as a surge, spike, sag, blackout, noise, or other type of transient.

Transistor—An electronic component that acts as a valve, or switch, allowing one signal (voltage or current) to control another.

Transmit-Tx—In fiber optics, the light source, such as an LED or laser.

Transmissive Technology—Any display device that creates images by allowing or preventing light to pass.

Transmitter—A device that converts from one signal type to another for transmission.

Transponder—A combination of a transmitter and a receiver on a satellite. Geostationary satellites that are used for TV program transmissions worldwide have several transponders, each operating independently. The transponder allows bi-directional communication with earth stations. DTV uses satellite transponders.

Transport Stream—A defined package for delivering data. Transport Streams are multiplexes of audio, video and other content which are usually broadcast over-the-air, although they can be streamed over IP networks too.

Treble—High audio frequencies, generally the range from 3kHz to 20kHz.

Trigger—A signal, typically TTL level, that is transmitted in order to synchronize two or more instruments.

Tri-Level Sync—A sync level scheme developed for HDTV in which the sync line first goes low, then transitions high while going through the reference voltage level, and then drops back down to the reference voltage. The transition of the positive-going sync signal through the reference voltage is the sync trigger.

Triple-Action Switching™—A process in which the RGB signal is muted during the switching, until the projector has time to sync up to the new image. This way, when a switch is made, viewers don't see the image scrambling that occurs until the projector syncs up. Instead, they see the image go blank and then the new image appears already synced up. This provides a professional appearance for presentations.

TRS-Tip, Ring, Sleeve—A three-conductor design of a phone connector that can be terminated as balanced or unbalanced.

True Color—A graphics format of various resolution schemes which displays 24 bit (16.7 million colors) or even 32 bit color information. This format, perfectly suitable for video, displays “true color” on computer and video screens (after appropriate conversion). In order to display “true color”, the graphics card of the computer must have enough RAM installed (at least 1-2 Mbytes - depending on the required resolution).

TS-Tip, Sleeve—A two-conductor design of a phone connector used for an unbalanced circuit.

TTL—1) In electronics, Transistor-to-Transistor Logic. A digital signal, usually 4-5 volts peak-to-peak with a distance limitation is 6-10 feet (1.8-3.0 meters). Signal splitting is acceptable. TTL signals are either on or off, and are characteristic of low resolution computers (CGA/EGA). 2) In network video streaming, Time to live. Multicast streaming traffic is typically programmed with a TTL value indicating the number of router hops that are permissible for the packet.

Tunable Laser—A laser in which its central wavelength can be varied or optimized as desired for a particular application.

TVL-TV Line—A resolution specifying the amount of black and white alternating lines that can be displayed in horizontal or vertical directions. It can be applied to both continuous media video devices (B/W CRT, three-gun CRT projector) and fixed pixel video devices (LCD, DLP, plasma). It’s generally different from the pixel counts of a fixed pixel video device.

TVRO-Television Receive Only—A term describing a local or home antenna system.

Tweeker—A small screwdriver for making sensitive adjustments to audio/visual and other electronic equipment. An Extron specialty.

Tweeter—A loudspeaker designed to reproduce high-pitched or treble sounds in the range of 4Hz to 20 kHz.

Twisted Pair—Any number of wires that are paired together and twisted around each other; can be shielded or unshielded.

TWo-t(2t) Pulse—A sine-squared test pulse for video equipment measurement, with its frequency characteristics covering the Bandwidth of the signal. The Distortion of this pulse created by the video amplifier or processor is measured in "K" units or factor, and should be as close to zero as possible. This test signal easily detects the non-linearity of video devices which results in spurious effects, signal overshoots, ringing etc, due to Group Delay effects.

Leave a comment

Please note, comments must be approved before they are published