Computers, Networking: An Ethernet LAN 10 Mbps baseband transmission standard using 50-ohm coaxial cable (RG-58 A/U) with BNC connectors connected to network cards via T-connectors. Unused connections must be terminated using 50-ohm terminators. The maximum cable length is 185 meters. Also called Thinnet.

10Base-5

10Base-36

Computers, Networking: An Ethernet LAN 10 Mbps baseband transmission standard using broadband 50-ohm coaxial cable (RG-58 A/U) with BNC connectors connected to network cards via T-connectors. Unused connections must be terminated using 50-ohm terminators. The maximum cable length is 3600 meters.

10Base-F

Computers, Networking: An Ethernet LAN 10 Mbps baseband transmission standard using fiber-optic cable.

10Base-T

Computers, Networking: An Ethernet LAN 10 Mbps baseband transmission standard using twisted-pair telephone wire.

16:9

Video: The aspect ratio for widescreen DTV video.

1G

Acronym: 1st Generation Wireless

Telephony: A term used to describe analog cellular telephones.

1xEv-DO CDMA: see CDMA, HDR.

1xRTT CDMA: see CDMA, 1xRTT.

2D Mode

Metal Detectors: see Scan, Wide.

GPS Acronym: 2 Dimensional Mode

GPS: A two-dimensional GPS position fix that includes only horizontal coordinates (no elevation). It requires a minimum of three visible satellites.

2G

Acronym: 2nd Generation Wireless

Telephony: A term used to describe digital cellular telephones that use circuit-switched networks.

2.5G

Acronym: 2.5 Generation Wireless

Telephony: A term used to describe wireless telecommunications technology that uses circuit-switched networks to approach the capabilities offered by 3G networks. 2.5G is an interim stage in wireless telecommunications development.

3D Mode

Acronym: 3 Dimensional Mode

GPS: A three-dimensional GPS position fix that includes horizontal coordinates plus elevation. It requires a minimum of four visible satellites.

3G

Acronym: 3rd Generation Wireless

Telephony: A term used to describe digital cellular telephones that use packet-switched networks.

3G 1x: see CDMA, HDR.

300-ohm

Cables: The standard impedance for twin-lead antenna connections found on older antennas and televisions (click here for an illustration).

4:3

Video: The aspect ratio for NTSC video.

4G

Acronym: 4th Generation Wireless

Telephony: A term used to describe the next generation of wireless telecommunications, expected to deliver wireless multimedia content anywhere, anytime and to any device.

5.1 Sound

Audio: A sound encoding method consisting of five full-bandwidth channels (front right, front left, center, rear right and rear left) plus ".1", a limited-bandwidth subwoofer channel.

50-ohm

Cables: The standard impedance for coax computer networking cable (click here for an illustration).

75-ohm

Cables: The standard impedance for coax audio/video cable used between antennas and receivers/television (click here for an illustration).

8 mm

Video: A videotape format used in older and some current camcorders.

802.11

Telephony: The IEEE standard for wireless local area networks (WLAN's).

A: see Ampere.

a-: see atto-.

AAC (.aac)

Acronym: Advanced Audio Coding

Audio: An audio codec developed by the Fraunhofer Institute to create audio files at lower bit rates while maintaining audio quality. Like MP3, it is a form of lossy compression.

AAP

Acronym: Artists Against Piracy

Audio: A coalition of recording artists with the aim to educate the public about the harm that illegal recordings do to artists and the industry.

Absolute Humidity: see Humidity, Absolute

Absolute Temperature Scale: see Temperature Scale, Absolute

Absolute Zero

Measurement, Weather: A hypothetical temperature characterized by a complete absence of heat and defined as 0³ Celsius, or -459.67³ Fahrenheit.

AC

Acronym: Alternating Current

DIY, Electronics: An electrical current which changes the direction of its flow in a regular manner. The number of times that the current cycles per second is called Hertz. Compare to DC.

AC-3^®

Acronym: Audio Coding 3

Audio: A digital audio data compression algorithm used by Dolby^®.

Accuracy

Measurement: The degree of conformity of an indicated value to an accepted standard value, or ideal value.

Actual Pressure: see Pressure, Actual

Acquire

GPS: To find and lock onto GPS satellite signals in order to calculate position.

Active Component: see Component, Active.

Active Filter: see Filter, Active.

Active Noise Reduction: see Noise Reduction, Active.

Actuator

Electronics: The element of a potentiometer that is adjusted to vary the resistance. Actuators are either Rotary (turning) and Linear (sliding).

A/D

Acronym: Analog to Digital

Electronics: A device that converts an analog signal to a digital signal, such as an A/D Converter IC.

A/D Converter

Acronym: Analog to Digital Converter

Electronics: A device that converts an analog signal to a digital signal.

Digital Video: A device that converts analog video information (a photograph or video frame) into a series of numbers that a computer can store and manipulate.

Adapter

Connections: A piece of hardware that allows the user to connect incompatible plugs and/or sockets.

Computer: A piece of hardware that allows the user to connect an input and output port of different types.

Electronics: A device that converts power, such as from AC to DC voltages. The types of adapters are: AC to DC, AC to AC (Foreign, or Travel Adapters), DC to DC (Car Adapters), and DC to AC (Inverters). Also called Converters.

Adaptive Transform Acoustic Coding: See ATRAC.

Address

Plug 'n Power: A House Code on a controller and a Unit Code on a module together make up what is called an address.

ADSL

Acronym: Asymmetric Digital Subscriber Line

Internet: A technology which allows high-speed Internet connections on standard telephone lines (POTS). It is called asymmetric because the data rate when receiving (downstream rate) is different from the data rate when transmitting (upstream rate). ADSL supports upstream data rates of 1.5 Mbps to 9 Mbps, and downstream data rates of 16 to 640 Kbps. Compare to SDSL.

Advanced Audio Coding: See AAC.

Advanced Mobile Telephone System: See AMPS.

Advisory

Weather: A statement that is issued by the National Weather Service for probable weather situations of inconvenience that are not dangerous enough to meet the criteria for a warning, but, if not observed, could lead to hazardous situations. Some examples include snow advisories stating possible slick streets, or fog advisories for patchy fog condition causing temporary restrictions to visibility.

Aerial

Weather: of or pertaining to the air, atmosphere, or aviation.

AFOS

Acronym: Automation of Field Operations and Services

Weather: The computer system that links National Weather Service offices together for weather data transmission.

AH

Acronym: Ampere-Hour

Batteries, Measurement: A measure of battery capacity. A battery rated at one ampere-hour can (under optimum conditions) produce one amp of current for one hour. The higher this number, the longer the battery will deliver useful power.

AIFF

Acronym: Audio Interchange File Format

Audio: A type of file used to store digital sound. This is the most common digital music format on Macintosh^® Computers.

Air

Weather: The mixture of gases that make up the earth's atmosphere. The principal gases that compose dry air are nitrogen (N2) at 78.09%, oxygen (O2) at 20.946%, argon (A) at 0.93%, and carbon dioxide (CO2) at 0.033%. One of the most important constituents of air and most important gases in meteorology is water vapor (H2)).

Air Mass

Weather: An extensive body of air in which the horizontal temperature and moisture characteristics are similar.

Air Test

Metal Detectors: A test performed by passing metal samples of various sizes under the detector's search coil to check target responses. This test is not an accurate indicator of ground depth penetration.

Airtime

Telephony: The amount of time spent talking on a cellular telephone.

Algorithm

Computers, Digital Audio, Digital Video: A structured formula or set of instructions and operations designed to accomplish a particular task.

Alkaline Cell

Batteries: A primary battery cell that delivers more current than a carbon-zinc cell. Also called Alkaline Manganese Cell.

Alkaline Manganese Cell: see Alkaline Cell.

All Call

Communications, Scanners: An message identification code that is programmed to be received and decoded by all users in a communications group. This allows a dispatcher, for example, to communicate with all users at once.

Alligator Clip

DIY: A spring clip on the end of a test lead that allows the user to make a secure but temporary connection.

All Metal

Metal Detectors: A mode or control setting that allows total acceptance of metal targets. Usually associated with ground balance mode.

Almanac

GPS: A data file that contains orbit information on all satellites, clock corrections, and atmospheric delay parameters. It is transmitted by a GPS satellite to a GPS receiver, where it facilitates rapid satellite vehicle acquisition within GPS receivers. Almanac data must be acquired before GPS navigation can begin.

Alphanumeric

Computers: A data format in which the content can contain both letters and numbers, such as F13.

Alphanumeric Memory Dial

Telephony: A cellular telephone memory dialing option option that displays each stored individual's name and telephone number on the handset.

Alternating Current: see AC.

Alternation

Electronics: One half of a cycle of alternating current.

Alternator

DIY, Electronics: A device that converts mechanical energy into electrical energy (AC power).

Altimeter

Weather, Measurement: An instrument used to determine the altitude of an object with respect to a fixed level, usually sea level.

Altimeter, Pressure

Weather: An aneroid barometer calibrated to indicate altitude in feet instead of units of pressure. It is read accurately only in a standard atmosphere and when the correct altimeter setting is used.

Altitude

Measurement: The measure of a height of an airborne object in respect to a constant pressure surface or above mean sea level.

GPS: The vertical elevation of an object above a surface (as sea level or land) of a planet or natural satellite.

Altocumulus

Weather: A middle cloud composed of flattened, thick, gray, globular masses and primarily made up of water droplets. In the mid-latitudes, cloud bases are usually found between 8,000 and 18,000 feet. Altocumulus clouds have roll-like patches or puffs forming a wavy pattern. Sometimes confused with cirrocumulus clouds, its elements (individual clouds) have a larger mass and cast a shadow on other elements. It may form several sub-types, such as altocumulus castellanus or altocumulus lenticularis.

Altocumulus Lenticularis

Weather: A lentil- or plate-shaped altocumulus cloud generated by the disturbance of horizontal airflow by a prominent mountain range.

Altocumulus Castellanus

Weather:A middle cloud with vertical development that forms from altocumulus clouds. It is composed primarily of ice crystals in its higher portions and characterized by its turrets, protuberances, or crenelated tops that resemble a castle. These clouds indicate instability and turbulence at the altitudes where they occur.

Altostratus

Weather: A middle cloud composed of water droplets, and sometimes ice crystals, in the mid-latitudes. Cloud bases are generally found between 15,000 and 20,000 feet. White to gray in color, it can create a fibrous veil or sheet, sometimes obscuring the sun or moon. It is a good indicator of precipitation, as it often precedes a storm system.

AM

Acronym (Communications, Telephony): Amplitude Modulation

Communications, Telephony: A modulation method that modulates a signal onto a carrier wave so that the amplitude varies according to a characteristic of the signal. Also called MW (medium wave).

Acronym (Computers): Automated Mapping

Computers: The automatic conversion of particular styles in a source document to a corresponding class in HTML documents.

Amateur Radio: See Ham.

American National Standards Institute: See ANSI.

American Society of Composers, Authors and Publishers: See ASCAP.

Ammeter

DIY: A testing device used for measuring current in amps. Also called an Amp Meter.

Ammeter Shunt

DIY: A low-resistance conductor placed in parallel across the ammeter movement to carry most of the current and increase the range of the ammeter.

Amp

Audio, Video: short for Amplifier.

Measurement: short for Ampere.

Ampere

DIY, Measurement: The unit of measurement for current, named for André Marie Ampère, and equal to one coulomb per second.

Amp-hour: See AH.

Ampere-hour: See AH.

Amplifier

Audio, DIY, Video: An electronic device that increases the current, voltage, or power of an electrical (and generally either an audio or video) signal. Specific types of amplifiers are: Audio Amplifiers, Distribution Amplifiers, In-Line Amplifiers, and Signal Amplifiers.

Amplifier, Audio

Audio: An audio component (rated in watts and either stand-alone or within an audio receiver) that amplifies the audio signal.

Amplifier, Broadband: see Amplifier, Wideband.

Amplifier, Distribution

Audio, Video: A device that splits an incoming signal and then amplifies the outgoing signals in order to compensate for a poor signal or signal loss due to splitters, connectors or long cable runs (over 100' for coax).

Amplifier, In-line

Audio, Video: A device with a single input and output that is used in line within a cable run to amplify the signal strength and compensate for a poor signal or signal loss due to splitters, connectors or long cable runs (over 100' for coax).

Amplifier, Operational: see Op-Amp.

Amplifier, Signal

Audio, Video: A device that amplifies a signal to compensate for a poor signal or signal loss due to splitters, connectors or long cable runs (over 100' for coax).

Amplifier, Wideband

Electronics: A device that amplifies a signal over a wide range of frequencies with a flat response. Also called a Broadband Amplifier.

Amplitude

Electronics: The maximum absolute value reached by a waveform.

Amplitude Modulation: See AM.

Amp Meter: See Ammeter.

AMPS

Acronym: Advanced Mobile Phone System

Telephony: The analog cellular FM system currently used in North America. It operates in the 800 MHz band and uses 30 KHz channels. It is used by analog cellular telephones and by digital cellular telephones in areas that the digital cells do not cover.

Analog

A system that uses a physical change to represent variables. Compare to Digital.

Audio: In analog recordings, the audio signals are represented by physical changes (either electromagnetic alteration of the surface of recording tape or grooves in a vinyl record) and read by an electro-mechanical device that converts the analog information back into audio. Each analog recording has a certain amount of signal loss between the original source and the playback, which makes each succeeding generation of copies less accurate than the original.

Communications: The traditional method of modulating radio signals so that they can carry information. AM (amplitude modulation) and FM (frequency modulation) are the two most common methods of analog modulation.

Telephony: Refers to cellular telephones that use the AMPS cellular telephone system.

AND

Electronics: A logic gate that outputs "True" when both inputs are "True"; otherwise, the output is "False".

Input 1	Input 2	Output
True	True	True
True	False	False
False	True	False
False	False	False

Anemograph

Weather, Measurement: A recording anemometer.

Anemometer

Weather, Measurement: An instrument that measures the speed or force of the wind.

Aneroid

Weather, Measurement: Literally, "without air". In weather, used in reference to an aneroid barometer.

Aneroid Barometer: see Barometer, Aneroid.

Aneroid Capsule

Weather: A thin metal disc that is partially evacuated of air and used to measure atmospheric pressure by measuring the expansion and contraction of the disc.

Angle of View

Digital Video: The amount of a scene that can be recorded by a particular lens. This is determined by the focal length of the lens.

Anode (+)

Batteries: The positively charged pole of an electrochemical cell.

Electronics: The electrode through which a direct current enters a component.

Anomalous Propagation

Weather, Communications: The non-standard propagation of a beam of energy, radio or radar, under certain atmospheric conditions, appearing on weather radar as false (non-precipitation) echoes.

ANSI

Acronym: American National Standards Institute

Electronics: The organization responsible for administrating and coordinating the voluntary standardization system for the private sector in the United States.

Antenna

Audio, Video, Communications: A device that is designed to either recieve, transmit or receive and transmit a wireless signal.

GPS: A device (as a rod or wire), usually metallic, for radiating or receiving radio waves.

Antenna, Broadcast

Video: An antenna that is designed to pick up signals broadcast from a ground-based source, such as for a local television station.

Antenna, Satellite

Satellite: An antenna, a dish and an LNB, designed to pick up signals broadcast from a satellite in geosynchronous orbit.

Anti-aliasing

Digital Video: The process of reducing jaggies (or stair-stepping) by smoothing the edges where individual pixels are visible.

Anticyclone

Weather: A area with relatively high pressure. An area of pressure that has diverging winds and a rotation opposite to the earth's rotation. This is clockwise the northern hemisphere and counter-clockwise in the southern hemisphere. It is the opposite of an area of low pressure, or a cyclone.

Anvil

Weather: The upper portion of a cumulonimbus cloud that becomes flat and spread-out, sometimes for hundreds of miles downstream from the parent cloud. It may look smooth or fibrous, but in shape, it resembles a blacksmith's anvil. It indicates the mature or decaying stage of a thunderstorm.

Appliance Module: See Module, Appliance

Anti-skip

Audio: A feature on CD players which limits the skipping effect caused by physical shock to the player, such as can occur in vehicles or portable units. Anti-skip works by feeding the music into a buffer memory, and then playing the music from the buffer. If a shock causes the laser eye to lose the track momentarily, the music continues to play from the buffer while the laser eye resets to the position it left. Anti-skip is measured in the number of seconds of sound that can be stored by the buffer memory. As the number of seconds increases, the amount of protection also increases. While anti-skip cannot prevent all skipping, it does greatly limit it. Anti-skip is also listed as ASP (Anti-Skip Protection) and Anti-shock.

Appliance Module: See Module, Appliance

Aperture

Digital Video: The maximum size of the hole through which light enters a camera.

Archie

Internet: A program that enables you to search for a particular file on Internet FTP servers by filename.

ARCnet

Acronym: Attached Resource Computer network

Computers: A type of token-ring LAN that allows different types of cables (twisted pair, coaxial and fiber-optic) to be used on the same network. It was introduced by Datapoint Corporation in 1977 and supports data rates of 2.5 Mbps, on up to 255 computers.

ARCnet Plus

Acronym: Attached Resource Computer network Plus

Computers: A new variant of ARCnet that supports data rates of 20 Mbps.

Arm:see Tonearm.

Artifacting, Artifact

Digital Video: Distortion or excess noise that is caused by the sensor, the optical system or image processing (such as compression).

Artists Against Piracy: See AAP.

ASCAP

Acronym: American Society of Composers, Authors and Publishers

Audio: A performing-rights licensing organization dedicated to protecting the intellectual-property rights of its members.

ASCII

Acronym: American Standard Code for Information Interchange

Computers: A standard code used to represent English character.

Aspect Ratio

Digital Video: The ratio between the width and height of an image or image sensor.

Asynchronous Transfer Mode: see ATM.

A.T.I.

Acronym: Audio Target Identification

Metal Detectors: A system in which a certain audio pitch identifies the type of metal object located.

ATM

Acronym: Asynchronous Transfer Mode

Networking: An international standard for cell relay in which multiple service types (such as voice, video, or data) are carried in fixed-length (53-byte) cells. The fixed-length cells allow cell processing to occur in hardware rather than software, in order to increase transmit speed. ATM is designed to take advantage of high-speed transmission media such as T3.

Atmosphere

GPS, Weather: The envelope of air surrounding the earth and bound to it more or less permanently by virtue of the earth's gravitational attraction. The divisions of the atmosphere include the troposphere, the stratosphere, the mesosphere, the ionosphere, the thermosphere, and the exosphere. See What is Weather? for an illustration of the atmospheric layers.

Measurement: A unit of pressure, also called the standard atmosphere.

Atmosphere, Standard

Weather, Measurement: As defined by the International Civil Aeronautical Organization (ICAO), a standard atmosphere assumes a mean sea level temperature of 15°C, a standard sea level pressure of 1,013.25 millibars or 29.92 inches of mercury, and a temperature lapse rate of 0.65°C per 100 meters up to 11 kilometers in the atmosphere.

Atmospheric Pressure: see Pressure, Atmospheric.

ATRAC™

Acronym: Adaptive Transform Acoustic Coding

Audio: A digital music file format developed by Sony^®.

Attachment

Internet: A file sent along with an e-mail message so that it can be viewed or saved by the recipient.

Attenuate

Electronics, Audio, Video: To reduce the amplitude of an action or signal.

Attenuator

Connections: A device that reduces signal strength without significantly affecting the signal quality.

atto- (a-)

Measurement: SI unit of decimal measurement, equal to 10^-18 or 0.000000000000000001.

Audio, Analog

Audio: An audio signal from an analog source (NTSC broadcast, VCR, Tape Deck, et al.) that is carried either on a 75-ohm coax cable (along with the video signal), or on one (mono) or two (stereo) audio/video patch cables

Audio ID

Metal Detectors: A feature in metal detectors which uses circuitry to produce a different audio tone for each target's conductivity range -- for example, a low tone for iron, and a high tone for coins.

Audiophile

Audio: An individual who has an intense interest in high-quality audio.

Audio Response: see Target Response.

Audio Target Identification: see ATI.

Audio/Video Patch Cable

Audio: A single-conductor cable with an RCA plug on each end, packaged as either a single cable or as a bundle of two, three or four cables (click here for an illustration).

Autofocus

Digital Video: A system that automatically focuses the camera lens.

Automatic Exposure

Digital Video: A feature where the camera automatically adjusts the aperture or shutter speed or both for the proper exposure.

Automatic Flash

Digital Video: A flash unit with a light-sensitive photocell that determines the length of the flash for proper exposure by measuring the light reflected back from the subject.

Automatic Mapping: See AM.

Auto-ranging

DIY: Used to describe a multimeter that automatically selects the proper range for measurement.

AutoShot™

Video: A feature on RCA^® camcorders that automatically provides focus, shutter speed, iris and white balance.

Auto Tune

Metal Detectors: A feature in metal detectors which uses circuitry to continuously retune the detector's threshold to the initially tuned audio level at a preset rate after drift and/or target rejection.

A/V

Acronym: Audio/Video

Audio, Video: Used to describe audio and video equipment and accessories.

Averaging: See Matrix Metering.

AVI™

Digital Video: A digital video format used by Microsoft^® Windows^®.

AWG

Acronym: American Wire Gauge

Cable: A measurement describing the diameter of a wire. The larger the gauge, the smaller the wire will be. For example, a 12 AWG wire has a larger diameter than a 16 AWG wire. Also called Gauge (GA).

Azimuth

Satellite: The side-to-side (left-to-right) angle setting on a satellite antenna.