| TCP/IP | Transmission Control Protocol/Internet Protocol, is a suite of communication protocols used to interconnect network devices on the internet. TCP defines how applications can create channels of communication across a network. |
| TDN | True D/N camera has two modes of operation: a day mode and a night mode. The camera switches from day mode (color) to night mode (black and white) by replacing its infrared-cut filter with a clear filter. In night mode, the camera becomes sensitive to near-IR light and is capable of reproducing images even when objects in the scene are not visible to the naked eye. |
| termination block | A terminal block is a screw-type electrical connector where the wires are clamped down to the metal part by a screw. It is a connector which allows more than one circuit to connect to another circuit. |
| test tone | A constant pure sine wave tone or tones played over an audio system to allow critical measurement and adjustment of an audio system both when individual components are being developed and when a complete system is being installed. |
| THD (Total Harmonic Distortion) | Distortion derived from the creation of harmonics (multiples of a base frequency signal) in an audio system adding additional frequency peaks to the output. |
| THD+N (Total Harmonic Distortion plus Noise) | Combination of total harmonic distortion (THD) with noise to achieve a complete figure representing distortions present in an electronic component with lower levels below one percent being preferable (see THD and Noise). |
| THX | THX is a high fidelity audio/visual reproduction standard for movie theaters, screening rooms, home theaters, computer speakers, gaming consoles, car audio systems, and video games. |
| timbre matching | The esoteric philosophy of timbre matching the center channel speaker and front speakers, to create a deeper, more involving experience for music and movies in the home theater environment. |
| timbre | The combination of harmonic frequencies in voices or instruments which give them their characteristic quality. Synonyms: 'Quality', 'Sonority', 'Tone Colour'. |
| TMDS (Transition Minimized Differential Signal) | A transmission scheme for high-speed, serial video data used in HDMI |
| toe-in | Angling a speaker in toward the primary listening position to achieve better imaging and sound quality. |
| Toslink® | A standardized optical fiber connector system. Also known generically as an "optical audio cable" or just "optical cable", its most common use is in consumer audio equipment (via a "digital optical" socket), where it carries a digital audio stream from components such as DVD players, computers, and video game consoles, to an A-V receiver that can decode two channels of uncompressed lossless PCM audio or compressed 5.1/7.1 surround sound such as Dolby Digital or DTS. |
| transformer (audio) | A device that "transforms" the impedance and level from one value to another while breaking the ground-to-ground connection through mutual induction. Used to eliminate or reduce signal hum and R.F.I. (common mode rejection), while providing a means to transform from one impedance and signal level to another. |
| transient | Sudden, sharp signal increase often referring to a sudden increase in sound volume or power. |
| transport | Part of an audio or audio-video playback system which reads the data from a storage medium (typically CD, DVD or laserdisc) but does not decode that data from its digital form into an analog form suitable for audio reproduction (or potentially video reproduction where applicable). |
| transport controls | A set of controls dating back to hardware (mechanical) recorders and players that set the transport in motion and control its action. Modern solid-state and software applications carry forward the concept of transport controls for controlling playback of audio and video tracks. |
| treble | The upper part of the audio frequency spectrum that contains high frequencies. |
| TRS (Tip Ring Sleve) | A three contact phone connector, TRS connectors, where T stands for tip, R stands for ring and S stands for sleeve. |
| TS | A two contact phone connector, TS connectors, where T stands for tip and S stands for sleeve. |
| TVI | Transport Video Interface. An open-platform technology based on Techpoint chipsets that allows analog HD (1080p) signals to travel over coaxial cables. Since TVI is not a proprietary technology, cameras made by one company will work with DVRs made by other companies. |
| TVL | TV Lines of resolution. In surveillance cameras, resolution is the level of detail you can see in an image. In analog CCTV cameras, resolution is measured in horizontal TV Lines (TVL). A higher TVL number, such as 800TVL indicates more detailed image than a low number like 480TVL, but there are other factors such as lens quality, contrast and color, that can be just as crucial. |
| tweeter | High frequency speaker driver used to reproduce frequencies typically above 2,000 to 3,000 Hz all the way up to 20,000 Hz. |
| twisted pair cabling | Cable constructed of twisted wire pairs, each conductor having its own insulation. Most twisted pair cables used in the home, such as Cat 5 and Cat6, include four pairs of wires within an outer insulating sheathing. There are two basic types of twisted pair cables: shielded and unshielded. Most applications in the home use unshielded four-pair cable. |
| two-way speaker | Speaker system with two or more individual drivers covering two frequency sections or bands. |
| UL | Underwriter’s Laboratory, a listing service for electrical and electronic equipment. |
| un-balanced line | Two-conductor cable - (center for plus) and (shield for minus). |
| USB (Universal Serial Bus) | A cable easily recognized by the rectangular plugs on each end, is becoming the standard for connecting personal computers to peripheral accessories, such as keyboard, mouse, etc. This cable is rapidly replacing the old-fashioned multi-pin computer cables. |
| user interface | Devices such as push-buttons, volume controls, keypads, and LCD touchscreens that allow control of electronic systems. There are a wide variety of user interfaces available and most can be mounted in the wall or are designed for the table-top or counter. Mobile devices such as smartphones and tablets can also serve as the user interface in some cases. |
| UTC | Up the Coax is a way of programming cameras from a remote location using the coaxial transmission cable. A UTC programmer connects in-line between the camera and the monitor or DVR. |
| UTP | Unshielded Twisted Pair, usually Cat 5e or Cat 6. Can be Plenum-rated or standard. |
| variable audio output | Low level audio output (usually in the form of a RCA connection) which varies in strength with the volume or level of the source component. |
| vertical input | Vertical InputUsually referring to the vertical (Y) input of an oscilloscope that measures an audio, I.F. or R.F. signal source. |
| VHS | Video Home System (VHS) is an obsolete standard for consumer-level analog video recording on tape cassettes. Developed by Victor Company of Japan (JVC) in the early 1970s, it was released in Japan in late 1976 and in the United States in early 1977. |
| VOB | (Video OBbjects) A DVD movie file that contains MPEG video and AC-3 or other audio data. Audio streams for multiple languages are multiplexed together. VOB files have specific file names that start with VTS (Video Title Set) and contain title and section; for example: VTS_01_2.VOB means Title 1, Section 2. VIDEO_TS.VOB is the start of the content and typically contains menus and trailers. |
| volume | Loudness of sound; a subjective sensation dependent on the amplitude of a sound wave or electrical signal, but not linearly related to it. |
| VPN | Virtual Private Network |
| w/ch (watts per channel) | Measurement of power output for each channel in an amplifier. Ratings are different on multi-room amps with all channels driven, vs. two channels driven, etc. |
| watt | Measurement of power derived by multiplying current by voltage; measurement used to quantify the amount of power output by an amplifier. |
| WAV | The format for sound files developed jointly by Microsoft and IBM, and built into Windows 95 which made it the de facto standard for sound on PCs. WAV sound files end with a.wav extension and can be played by nearly all Windows applications that support sound. |
| waveform | A graphical representation of a signal as a plot of amplitude versus time, i.e. the shape of a wave. |
| wavelength | Distance between two points in the same position on a wave in two consecutive cycles (two cycles directly following one after the other). |
| WDR | Wide Dynamic Range. The dynamic range of light levels is the range of visible light from the darkest part of the image to the brightest part that can be captured by a specific camera. A WDR camera's dynamic range must exceed 60 decibels (dB) in width. The human eye can perceive a range measured at 113dB wide; the best CMOS sensors available today can capture a range 130dB wide. This range can be shifted toward the light or dark end of the light spectrum, optimizing the contrast shown in the image for the lighting in the scene. Almost no latency - adjusts immediately. |
| white noise | Broadband test noise where the amplitude has no attenuation as frequency increases. |
| Windows® (Microsoft® operating system) | Operating system designed and produced by Microsoft Corporation. Similar to other operating systems, Windows makes a computer system user-friendly by providing a graphical display and organizing information so that it can be easily accessed. |
| WMA | WMA is a file extension used with Windows Media Player. WMA stands for Windows Media Audio. WMA is both an audio format and an audio codec. WMA was intended to be a competitor for the MP3 and RealAudio audio formats. |
| WMV | Windows Media Video (WMV) is a series of video codecs and their corresponding video coding formats developed by Microsoft. WMV consists of three distinct codecs. The original video compression technology known as WMV, was originally designed for Internet streaming applications, as a competitor to RealVideo. |
| woofer | Speaker driver that handles the low frequency signals of a sound wave. |
| XLR | Multipoint plug used for professional audio equipment |
| Y-connector | Connection that splits a single cable into two so that it may begin from one source with one connection and terminate in two connections on two components (or it may go the other way - two outputs joined to the same input; however, this may not work if both outputs are sending information at the same time). |
| zero crossing | An analog waveform consists of two alternating voltage polarities (positive to negative to positive...etc.). The point where the polarity changes from positive to negative, or vice versa, is called the zero crossing. When looping a wave or editing two waveforms together, this is the ideal location for the splice as the levels of the two waves are both at zero. This eliminates the possibility of clicks or pops created by mis-matched levels, and makes for a smooth sonic transition. |
| zone | In audio terms, a zone is an area in a home, office or other structure to which audio and/or video signals are distributed. |
