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Term
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Description
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H x V
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Aspect ratio in horizontal (H) and vertical (V) dimensions.
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H.323
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A standard approved by the International Telecommunication
Union (ITU) that defines how audiovisual conferencing data
is transmitted across networks. As an example, in theory,
H.323 should enable users to participate in the same conference
even though they are using different videoconferencing applications.
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H2GF
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HiperLAN2 Global Forum
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Half-Duplex Ethernet MAC
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Is the traditional form of Ethernet that uses the CSMA/CD
protocol. With CSMA/CD two or more stations share a common
transmission medium. To transmit a frame, a station must wait
for an idle period on the medium when no other station is
transmitting. It then transmits the frame by broadcasting
it over the medium such that it is "heard" by all the other
stations on the network. If another device tries to send data
at the same time, a "collision" is said to occur. The transmitting
station then intentionally transmits a "jam sequence" to ensure
all stations are notified the frame transmission failed due
to a collision. The station then remains silent for a random
period of time before attempting to transmit again. This process
is repeated until the frame is eventually transmitted successfully.
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Halftone
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Different-sized black dots produced by turning particular
dots on and off during printing, either on a laser printer,
an image setter, or a printing press. The dots repeat in a
regular pattern, creating the illusion of continuous tone.
Color ink jets use their process colors in a similar scheme.
Other colors are produced by laying down patterns of the process
color dots, varying the pattern and ratio of each color. Halftone
dots are not the same as printer dots.
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Hamming Codes
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These are the first class of linear binary codes used for
error correction in long-distance telephony.
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Handheld gaming devices
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Consumer devices used primarily for mobile electronic games
mobile. These rely on DC power as the primary energy source
and include an embedded video display, such as an LCD.
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Hand-off
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The process that occurs when a mobile user travels from one
cell (terminating communications) to another cell (initiating
communications) in a cellular network. With the exception
of CDMA networks, hand-offs normally involve switching from
one pair of frequency to another. Hand-off typically describes
the ability of a wireless network to pass the network connection
of a roaming device from one connection point to another,
without dropping the network connection.
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Handover
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The procedures by which an mobile terminal, due to its own
movement and/or due to changes in the radio environment not
caused by own movement, replaces the current association and
all established connections the mobile terminal has with one
access point to another access point.
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HAVi
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Home Audio/Video interoperability
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HAVi organization
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The HAVi Organization is a not-for-profit association of
leading consumer electronics, software, semi conductor and
computer manufacturers who have joined together to promote
a network architecture for Home Audio Video Interoperability.
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HAVi spec
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The HAVi specification is a consumer electronics (CE) industry
standard that will ensure that digital audio and video devices
that conform to this standard, regardless of manufacturer,
will have complete interoperability when connected via a network
in the consumer's home.
The HAVi specification document can be downloaded from the
Sony external web site: http://www.sony.co.jp/HAVi/
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HAVi-enabled
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Any consumer Electronic (CE) device that is designed and
built to conform to the HAVi specifications for interactivity.
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HDL
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Acronym for Hardware Description Language. Language used
when designing logic. The most common HDLs in use today are
Verilog and VHDL.
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HDL Bencher
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Software tool used to graphically create HDL testbenches
for simulation.
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HDLC
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High-level Data Link Control. It is a bit-oriented synchronous
data link layer protocol developed by the ISO. It specifies
a data encapsulation method on synchronous serial links using
frame characters and checksums.
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HDLC Controllers
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These are devices which perform the HDLC protocol. Some of
the key operations include handling bit oriented protocol
structure and formatting data as per packet switching protocol
defined in the X.25 recommendations of the CCITT. It includes
transmitting and receiving the packeted data serially, while
providing the data transparency through zero insertion and
deletion. These controllers generate and detect flags that
indicate the HDLC status. They provide 16-/32-bit CRC on data
packets using the CCITT defined polynomial, and recognize
the single byte address in the received frame.
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HDSL
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High Speed Digital Subscriber Loop. A data protocol which
allows full duplex transmission of 772 Kbps data over twisted
pair up to 20,000 feet.
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HDSL
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High data rate symmetric DSL - T1 or E1 speed achieve via
multiple modems and short distances.
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HDTV
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High Definition Television. Any one of a variety of video
formats offering greater visual accuracy (or resolution) than
current NTSC, PAL, or SECAM broadcast standards. HDTV has
a bandwidth of 300 MHz. HDTV is subjectively comparable to
35 mm film.
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Header
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The five bytes in an ATM cell that supply addressing and
control information, including generic flow control, virtual
path identifier, virtual circuit identifier, payload type,
and cell loss priority.
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High-Pass Filter
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A filter that passes high frequency signals
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HiperLAN
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High Performance European Radio LAN
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HiperLAN2
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Wireless LAN standard for the 5GHz spectrum, based on OFDM,
proposed by HiperLAN2 Global Forum.
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Hold Time
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Timing parameter that specifies the time the inputs need
to be held after a clock edge.
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Home Network
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A local area network (LAN) that connects the PCs in a home
and lets users access the Internet simultaneously, share drives,
share files and printers, and play head-to-head multi-player
games.
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Home Networking
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The vision of home networking includes the complete connection
of devices within the house to the Internet It includes the
broadband access, residential gateway, interconnectivity technologies
and the different information appliances and includes the
distribution of audio, video and data between information
appliances.
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Homebanking
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Homebanking enables consumers to manage all banking directly
from their home, using their PC or their TV set together with
a Set-top Box.
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HomePNA
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Home Phoneline Networking Alliance. An association of 115+
industry-leading companies represented by PC, networking,
semiconductor sectors that was founded by 3Com, AMD, AT&T,
Compaq, Epigram (now Broadcom), HP, IBM, Intel, Lucent Technologies,
Conexant & Tut Systems. Xilinx is a member and an active
participant. This alliance ensures adoption of a single, unified
phoneline networking standard and rapidly bring to market
a range of interoperable home networking solutions.
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HomeRF
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A working group with the goal of enabling the existence of
a broad range of interoperable consumer devices by establishing
an open industry specification for unlicensed, RF digital
communications for PCs and consumer devices in and around
the home.
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Homeshopping
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Home or Teleshopping enables consumers to choose and order
goods directly from their home, using their PC or their TV
set together with a Set-top Box.
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Host
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A computer to which an expansion device attaches. When a
LAN card is installed in a PC, that PC is the host to that
adapter. It is also a time sharing computer accessed via terminals
or terminal emulation.
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Hot Pluggable/ Insertion
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Users can add or remove 1394 devices with the bus active
and there is no need to reset the bus.
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Hot-Swapping
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Attaching or removing peripherals with a simple 'Plug &
Play.' Hot swapping allows not to shut down and restart the
PC. The PC automatically detects the peripheral and configures
the necessary software. It is a useful feature for users of
multi-player games & notebook PC users who want to share
peripherals.
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HP PCL
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Hewlett-Packard Printer Control Language. The most popular
and widely emulated Escape Code printer language. PCL is available
in several variants including PCL 3 , 4, 5 and 6, each of
which provides more facilities than the previous variant.
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HPGL
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Hewlett-Packard Graphics Language, a vector graphics language
used by Hewlett-Packard plotters and commonly output by CAD
software. Some laser printers emulate HPGL to allow their
use with CAD packages.
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HSSI
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High Speed Serial Interface
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HSTL
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Acronym for High-speed Transceiver Logic. It is a high-speed
memory standard commonly used for QDR memory.
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Hub
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Hub connects high-performance stations/devices to Ethernet
local area networks and provides high-performance inter-LAN
connectivity using switching technology. Hub is a repeater
with fault detection functionality.
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Hz
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Hertz, Cycles per second. Used as the international unit
of frequency. It was named after Heinrich R. Hertz, a German
physicist.
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