- H
- Electronics: see Henry.
- Electronics: see hecto- (h-).
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- Hail
- Weather:
Frozen precipitation that originates in convective clouds, such as
cumulonimbus, in the form of balls or irregular pieces of ice, which
comes in different shapes and sizes. Hail is considered to have a
diameter of 5 millimeter or more; smaller bits of ice are classified as
ice pellets, snow pellets, or graupel. Individual lumps are called
hailstones. It is reported as "gr" in an observation and on the metar.
Small hail and/or snow pellets is reported as "gs" in an observation
and on the metar.
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- Half-Duplex
- Computers: A communication standard where data travels in either one direction or the other, using 100% of available bandwidth.
- Audio:
A soundcard standard that requires that the user either record or
playback audio, as it does not allow simultaneous recording and
playback.
- Telephony: A communication system
in which data travels in either one direction or the other, so that the
user can either listen or talk, but not simultaneously talk into the
telephone and hear the other party.
-
- Half-wave Rectifier: see Rectifier, Half-wave.
-
- Hall Effect
- Electronics: The effect of generating a voltage by applying an external magnetic field perpendicularly to the direction of the current in a semiconductor.
-
Hall Voltage
- Electronics: The voltage generated in a semiconductor by the hall effect.
-
- Halo Effect
- Metal Detectors: An effect caused by the oxidation of certain metals, which creates a metallic "halo" around the object.
-
- Ham
- Communications: Used to refer to the amateur radio service, an amateur radio operator or equipment used in amateur radio. For information on the history of Ham radio, see the ARRL Backgrounder article.
-
- HAN
- Acronym: Home Area Network
- Telephony: A network connecting the computers and digital devices in a consumer's home. Compare to CAN, LAN, MAN, WAN.
-
- Handheld Device Markup Language: see HDML.
-
- Hand Held Metal Detector
- Metal Detectors:
A metal detector configuration whereby the operator holds a shaft or
handle which supports the search coil and control housing. Also called Pole Mount.
-
- Handoff
- Telephony: The automatic channel change that occurs when a cellular user moves from one cell to another.
-
- Hands-free
- Telephony: A feature that permits a driver to use a cellular car telephone without lifting or holding the handset.
-
- Handshaking
- Computers: A set of signals that coordinate the transfer of data from one device to another.
-
- Harmonic
- Audio, Communications: A frequency that is smaller in amplitudeand a multiple of a larger frequency. For example, 880 Hz is the second harmonic of 440 Hz and the third harmonic of 220 Hz.
-
- HDML
- Acronym: Handheld Device Markup Language
- Telephony: A modification of standard HTML designed for use on small screens of mobile telephones, PDA's, and pagers. It is a text-based markup language.
-
- HDR CDMA: see CDMA, HDR.
-
- HDTV
- Acronym: High-definition Digital Television
- Video: A digital video format with either 1080 or 720 lines of resolution, which provides greater detail and clarity. This format is expected to replace the current format in use in the United States (NTSC).
-
- Head
- Metal Detectors: see Search Coil.
- Audio, Turntables: The front part of the tonearm that contains the headshell.
-
- Headphones
- Audio:
An audio device designed to allow the listener to hear music or
conversations without disturbing others. The standard connector is the headphone plug, or phone plug; it can be either 1/4" (6.35 mm), 1/8" (3.5 mm), or 3/32" (2.5 mm), and either stereo or mono.
- Metal Detectors:
Used to prolong battery life, increase your ability to concentrate by
blocking out external noise, and allow you to better hear subtle
differences in discrimination and depth indications.
-
- Headshell
- Audio, Turntables: The removable part of the head onto which the cartridge is mounted.
-
- Heat Index
- Weather: The combination of air temperature and humidity that gives a description of how the temperature feels. This is not the actual air temperature.
-
- hecto- (h-)
- Measurement: SI / Metric unit of decimal measurement, equal to 102 or 100.
-
- Henry
- DIY, Electronics: The basic unit of inductance, named for Joseph Henry. An inductance of 1 Henry generates one volt of potential difference across an inductor in a circuit where the current is changing at a constant rate of one ampere per second.
-
- Hertz: see Hz.
-
- hFe: see B.
-
- High Clouds: see Clouds, High.
-
- High Pressure System
- Weather: An area of relative pressure
maximum that has diverging winds and a rotation opposite to the earth's
rotation. This is clockwise the in northern hemisphere and
counterclockwise in the southern hemisphere. It is the opposite of an
area of low pressure or a cyclone. Also called anticyclone
-
- Hi Fi
- Acronym: High-Fidelity
- Audio: Refers to sound reproduction equipment that reproduces sound as near to the original sound as possible
-
- High Discharge Devices
- Electronics, Batteries: Those devices which draw current from batteries at a high rate, leading to significantly shorter battery life than is experienced with low- to moderate-discharge devices.
High-discharge devices include (but are not limited to) the following:
Digital Cameras, CD Players, MP3 Players, CB Walkie-Talkies and FRS
radios, Portable Televisions, Handheld Video Games, Portable Audio
Systems (Boomboxes). See the Premium vs. Standard Batteries page for more information.
-
- High-pass Filter: see Filter, High-pass.
-
- Hip Mount: see Body Mount.
-
- Hoarfrost: see Frost.
-
- Hole
- Electronics: The absence of electrons in a semiconductor material, giving that material a positive charge.
-
- Horn-loaded
- Audio: A horn-loaded driver couples a standard speaker driver (tweeter, midrange or woofer)
to a physical "horn". The horn enhances the amount of air moved by the
speaker driver from the usual amount moved by the driver itself to a
much larger movement of air at the mouth of the horn. Horn-loaded
drivers are significantly more efficient than standard enclosures
(either closed or vented).
-
- Home Automation
- Plug 'n Power: Remote or automatic control of home appliances.
-
- Hot Rock
- Metal Detectors: A rock which contains a higher concentration of non-conductive ground minerals than the surrounding matrix to which the detector is balanced. A metallic (positive) response will be heard in the motion and non-motion modes, and a null or negative drop in threshold is heard in the all metal ground balance mode over these rocks.
-
- Hot Shoe
- Digital Video: A connector generally found on the top of a camera that lets you attach a flash unit and trigger it in sync with the shutter.
-
- House Code
- Plug 'n Power: The master code for a Plug 'n Power system. There are sixteen house codes available A - P. Whichever house code a controller is set to, all modules
set to the same house code will respond to it. Up to sixteen
independent systems can be installed in a home by setting controllers
and modules to different house codes.
-
- HTML
- Acronym: HyperText Markup Language
- Internet: The markup language used in a file on the World Wide Web that indicates how the text and images are to be displayed by a browser.
-
- Hub
- Computers, Networking: A device which has jacks for multiple cables (from PC's, servers, etc.) and which retransmits the signals from one device to all other devices on the hub.
-
- Hue
- Video: The wavelength of the base color. The addition of saturation or intensity allows the base color, such as red, to appear as a range of colors, such as dark brown, bright red and pink.
-
- Humidity
- Weather:
The amount of water vapor in the air. It is often confused with
relative humidity or dew point. Related terms: absolute humidity,
relative humidity, and specific humidity
-
- Humidity, Absolute
- Weather:
A measurement of humidity equal to the ratio of the mass of water vapor
to the total volume of the air. Usually expressed as grams per cubic
meter (g/m3).
-
- Hunting
- Digital Video: A problem which occurs in an autofocus system, where it has trouble finding the focus in an image so that the system moves in and out of focus continuously, "hunting" for the correct focus point.
-
- Hurricane
- Weather:
A tropical cyclone with sustained winds of 74 miles per hour (65 knots)
or greater in the north atlantic ocean, caribbean sea, gulf of mexico,
and in the eastern north pacific ocean. This same tropical cyclone is
known as a typhoon in the western pacific and a cyclone in the indian
ocean.
-
- Hurricane Warning
- Weather:
A formal advisory issued by forecasters at the national hurricane
center when they have determined that hurricane conditions are expected
in a coastal area or group of islands within a 24 hour period. A
warning is used to inform the public and marine interests of the
storm's location, intensity, and movement.
-
- Hurricane Watch
- Weather:
A formal advisory issued by forecasters at the national hurricane
center when they have determined that hurricane conditions are a
potential threat to a coastal area or group of islands within a 24 to
36 hour period. A watch is used to inform the public and marine
interests of the storm's location, intensity, and movement.
-
- HVAC
- Plug 'n Power: Heating, Ventilation and Air Conditioning. These systems include thermostats that can controlled by Plug 'n Power products and are an important part of home automation.
-
- Hygrograph
- Weather: An instrument that records a hygrometer's measure of water vapor.
-
- Hygrometer
- Weather: An instrument that measures the water vapor content of the atmosphere. See also psychrometer
-
- Hyper-cardioid
- Hyperscan
- Communications: A high-speed scan method available on some scanners.
-
- Hypertext Markup Language: see HTML.
-
- Hz
- Acronym: Hertz
- DIY, Electronics: The unit of frequency equal to one cycle per second, named for Heinrich Hertz.
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