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 RadioShack Consumer Electronics Glossary: U

 
µ-
Measurement: SI / Metric prefix "micro-", equal to 0.0000001 units.
 
UHF
Acronym: Ultra High Frequencies
Communications: The frequency band between 300 MHz to 3000 MHz.
Video: Broadcast channels 14 through 69 (inclusive).
 
UHF Loop
Video: An on-set antenna specifically for picking up UHF channels.
 
UL
Acronym: Underwriters Laboratories, Inc.
Underwriters Laboratories Inc. (UL)Standards: Underwriters Laboratories Inc. (UL) is an independent, not-for-profit product safety testing and certification organization. UL has tested products for public safety for over a century. Each year more than 17 billion UL Marks are applied to products worldwide. UL is not affiliated with (Linker) and does not endorse the Web site. The UL mark (shown to the right) is found on the same types of products as the CSA mark (Canada) and the CE mark (European Union).
 
Ultra-cardioid
Ultra-cardioid Polar Pattern Audio: A unidirectional microphone pickup pattern (or polar pattern) that has the highest sensitivity at 0°, and minimal sensitivity between 90° and 120°, with slight sensitivity at 180°.

Compare to Omnidirectional, Cardioid and Hyper-cardioid.

Ultra High Frequency: see UHF.
 
Ultrasonic
Communications, Audio: Frequencies higher than the human ear can hear, or higher than 20,000 Hz.
 
Ultraviolet
Weather: Electromagnetic radiation that has a wavelength shorter than visible light and longer than x-rays.
 
UMTS
Acronym: Universal Mobile Telecommunications Services
Telephony: The European term for 3G cellular systems based on the IMT-2000 standard.
 
Unbalanced
Audio: A circuit that uses a single conductor and a shield for connection. Unbalanced lines are more susceptible to line noise and interference. Compare to Balanced Line.
Balanced Line Illustration Unbalanced Line Illustration
Electronics: A circuit with a single branch.
 
Underexposure
Digital Video: A picture that appears too dark because not enough light got to the imaging system.
 
Underwriters Laboratories: see UL.
 
Unidirectional
Audio: A microphone which is designed for an improved signal to noise ratio over omnidirectional microphones. Unidirectional, or directional, microphones have a either a cardioid, hyper-cardioid or ultra-cardioid polar pattern.
 
Uninterruptible Power Supply: see UPS.
 
Uniform Resource Locator: see URL.
 
Unipolar
Electronics: A transistor in which only one of the charge carriers (either the negative or the positive) is involved in the transistor action. Junction transistors and insulated gate field-effect transistors are unipolar transistors.
 
Unit Code
Plug 'n Power: One of two code dials on a receiver (module). There are sixteen unit codes available, 1 - 16 When the corresponding number switch on a transmitter (controller) is pressed, any modules set to the same unit code will respond.
 
United States Weather Bureau: see .USWB
 
Universal Time Coordinate: see UTC.
 
Unity Gain: see Gain, Unity.
 
Universal Mobile Telecommunications Services: see UMTS.
 
Universal Serial Bus: see USB.
 
Unsharp Masking
Digital Video: A process by which the apparent detail of an image is increased; generally accomplished by the input scanner or through computer manipulation.
 
Uplink
Satellite: The act of sending data from an earth station up to a satellite, or data that is sent from an earth station up to a satellite.
 
Upload
Computers: To transfer data or programs from your computer or device to another computer or device. The opposite of Download.
 
URL
Acronym: Uniform Resource Locator
Internet: The address of a website, that usually starts with http://.
 
UPS
Acronym: Uninterruptible Power Supply
Electronics, Computers: An AC device with a large, rechargeable battery, that is connected between the AC outlet and a device to switch on and provide battery power to the device in the case of a power outage.
 
Upwind
Weather: The direction from which the wind is blowing. Also the windward side of an object. The opposite of the downwind or leeward side.
 
USB
Acronym: Universal Serial Bus
Computers: A high-speed port found on digital photography devices and newer computers, that allows much faster transfer speeds than a serial or parallel port.
 
USWB
Acronym: United States Weather Bureau
Weather: the official name of the National Weather Service prior to 1970.
 
Use (or Usage) Life
Batteries: A rating that describes how long a particular battery will last in a particular device.
 
UTC
Acronym: Universal Time Coordinate
Weather: one of several names for the twenty-four hour time which is used throughout the scientific and military communities. Other names for this time system are Zulu (Z) and Greenwich Mean Time (GMT)
 
UV
Acronym: UltraViolet
Communications, Electronics: The electromagnetic radiation band between visible light and x-rays.
 
UXGA
Digital Video: An image resolution of 1600 x 1200 pixels.

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