H-I0-A | B | C-Cn | Co-Cz | D | E | F-G | H-I | J-L | M | N-O | P-Q | R | S | T | U-Z
0-A | B | C-Cn | Co-Cz | D | E | F-G | H-I | J-L | M | N-O | P-Q | R | S | T | U-Z
- H: Symbol designation for
magnetic intensity & henry. Also See Henry
Duplex: (HDX) Transmission in either direction at a time; i.e. the two
communication DTE's cannot transmit simultaneously.
Exchange of predetermined signals between two devices establishing a
connection. Usually part of a communications protocol.
Physical equipment (as opposed to "software" or the computer
- Harness: An arrangement of wires & cables usually with many
breakouts, which have been tied together or pulled into a rubber or plastic
sheath, used to interconnect an electrical circuit.
- HDLC: See High-level Data Link Control
- HDMI: See High-Definition Multimedia Interface
- HDTV: See High-Definition Television
- HDX: See Half Duplex
- Head End: A passive component in
broadband transmission networks that translates 1 range of frequencies
(transmit) to a different frequency band (receive); allows devices on a single
cable network to send & receive signals without interference.
Auxiliary information preceding a transmission block.
- Headroom: The
amount by which a cable ACR exceeds 10 dB. The TIA/EIA 568B Standard states a
minimum of 10 dB of ACR is required for Category 5
- Heartbeat: Ethernet defined SQE signal quality test
- Height Level Language Applications
Programming Interface: (HLLAPI) An IBM API.
- Helical Scan: Storage method that
increases media capacity by laying data out in diagonal
- Henry: (H) A practical unit of inductance that will produce a
voltage drop of one volt when the current changes at the rate of one ampere per
- Hertz: (Hz) A term replacing cycles per
second for frequency. It distinguishes electromagnetic waveform energy; number
of cycles, or complete waves that pass a reference point per second,
measurement of frequency by which one Hertz equals 1 cycle per
- Heterogeneous Networks: Networks composed of hardware &
software from multiple vendors usually implementing multiple
- Hierarchical Backbone: A backbone with more than one layer
in the overall network architecture. Each layer can be either distributed or
- High-Definition Multimedia Interface:
(HDMI) An interface used for High Definition TV. Typically connects from video
sources like DVD players or Blue-Ray players to display screens. Digital audio
is included in the HDMI interface.
Television: (HDTV) Higher resolution TV, typically 1080 horizontal lines.
Substantially higher than NTSC or PAL television. Typically transmitted as
- High-level Data Link Control: (HDLC) An
ISO protocol for X.25 international communications.
- HLLAPI: See Height Level Language Applications Programming
- Home Page: Also knows as Web Page or Web Site. Conveys
information with graphic, text & now multimedia Capabilities. Usually the page
- Home-Run Cabling: A distribution method in which
single cables are run directly from the horizontal cross-connect to each
telecommunications outlet. This is also known as star topology.
Count: A field in the header of OP packet which counts the number of
routers through which the packet has been forwarded. When hop count reaches a
specified maximum value, the packet is discarded.
- Horizontal Cabling:
The wiring/cabling between the telecommunications outlet/connector & the
- Host: A computer attached to a network. It
typically refers to a multi-user computer but may be any addressable node on a
- Host Computer: The primary controlling computer in a multiple
computer system. the term is normally used for relatively more powerful or
- Hot Swappable: The process or replacing a module or
subassembly component in an electronic device without requiring a power off
situation to occur.
- HTML: See Hypertext Markup
- HTTP: See Hyper-Text Transport
- Hub: The communications center of a network or cabling
system. Star topology
- HUM: A term used to describe the 60- or 120
cycle per second noise present in the sound of some communications equipment.
Usually hum is the result of undesired coupling to a 60 cycle source or to the
defective filtering of 120 cycle ripple output of a rectifier.
- Hyper-Text Transport Protocol: (HTTP) The Method of
transferring web page data over the internet.
- Hypermedia: The
Combination of hypertext & multimedia in an online
- Hypertext: A type of text that allows embedded "links" to
other documents. Clicking on or selecting a hypertext link displays another
document or section of a document. Most World Wide Web documents contain
- Hypertext Markup Language: (HTML) a
tagging language used to create web pages used on the World Wide
- HZ: See Hertz
- I: A symbol used to
- I/O address: See Input/Output
- IANA: See Internet Assigned Numbers
- ICEA: Insulated Cable Engineers
- ICMP: See Internet Control Message
- Icon: A graphic symbol.
- IEC: See Innovative Electronics & Computing or International Electrotechnical Commission.
- IEEE: See
Institute of Electrical & Electronic Engineers
802.3: The physical layer standard specifying a LAN with a CSMA/CD access
method on a bus topology (e.g. Ethernet).
- IEEE 802.4: The physical
layer standard specifying a LAN with a token passing method on a bus topology
- IEEE 802.5: The physical layer standard for a LAN with a
token passing access method using a ring topology.
- IF: See Intermediate Frequency
- Impedance: The total
opposition a circuit offers to the flow of an alternating current at a
particular frequency. A combination of D.C. resistance & reactance, or in other
words, the friction or back pressure. Impedance is measured in ohms.
Consistency is met when speed (frequency) increases.
- Impedance Match:
A condition whereby the impedance of a particular circuit cable or component is
the same as the impedance of the circuit, cable, or devices to which it is
- Impedance Matching Transformer: A transformer designed to
match the impedance of one circuit to that of another
- Impulse Noise:
Pulse or pulses appearing at the output point of a data link, which were not
transmitted at the input point. Impulse noises are usually caused by external
electrical sources, such as lighting.
- Index of Refraction: The ratio
of light velocity in a vacuum to its velocity in a given transmitting
- Inductance: A property of a conductor or circuit which
resists a change in current. It causes current changes to lag behind voltage
changes & is measured in henrys.
- Induction: The phenomenon of a
voltage, magnetic field, or electrostatic charge being produced in an object by
line of force from the source of such fields.
Standard Architecture: (ISA) The popular architecture for 1980s and early
1990s personal computer buses, such as the IBM PC,XT, & AT.
Transfer: Synonymous with data transfer. Information is a broader term than
data. Information includes: voice, graphics, & other types of
- Initial Handshaking: A commonly used term for a sequence in
data transfer. During initial handshaking, the two communicating DTE's may
exchange identities & confirm that they can transfer data.
- Innovative Electronics & Computing: (IEC) . Answering all of
your Interface Questions and Cable needs. IEC has a full line of Cable
Assemblies, Switches, Networking Equipment, Tools & Test Equipment & so much
- Input: A signal (or power) which is applied to a piece of
electric apparatus or the terminals on the apparatus to which a signal or power
- Input-Output Controller: (IOC) A
sub-unit in a computer or attached to a computer that manages the movement of
data between the computer & the input & output devices (I/O devices), such as,
keyboards, video display units & printers.
- Input-Output Program: A
program that manages the movement of data between the computer & the input &
output devices (I/O devices).
Address: (I/O address) Starting address for data input &
- Insertion Loss: The loss caused by the inclusion of a splice,
connector or other such component in a system.
- Inside Wiring: In
telephone deregulation, the customer's premises wiring; the wiring inside of a
- Institiute of Electrical & Electronic
Engineers: (IEEE) A standards making organization.
- Insulation: A
material having good dielectric properties which is used to separate close
electrical components such as cable conductors & circuit components.
- Integrated Service Unit: (ISU) A single device that
combines the functions of both a CSU & a DSU.
- Integrated Services Digital Network: (ISDN) The ideas
behind the need for an ISDN is that there are growing consumer requirements for
digital services over long distances, demands placed on the telephone
- Inter-Character Gap: During asynchronous start-stop
transmission, the interval of time between the stop bit of one character & the
start bit of the next character.
- Interactive Processing: Describing
time-dependent (real-time) data communications; a user enters data & waits for
response from the destination before continuing; also, conversational; contrast
with batch processing.
- Interchange Code: A set of unambiguous rules
specifying the way in which data may be represented.
Provides for the direct connection of individual cables to another cable or to
an equipment cable without a patch cord.
- Interface: The boundary
between hardware & software components of a network.
Disturbances of an electrical or electromagnetic nature that introduce
undesirable responses into other electronic equipment.
- Intermediate Frequency: A frequency to which signal is
converted for ease of handling. Receives its name from the fact that it is an
intermediate step between the initial & final conversion or detecting
- International Electrotechnical Commission:
(IEC) is an international standards organization that prepares and publishes
International Standards for all electrical, electronic and related
technologies. Some of their standards involve connectors for power (IEC320)
like the ones found on our M1303
- International Standard: An ISO standards document that has
been approved in final balloting.
Standards Organization: (ISO) An organization of 89 member countries
(founded in 1946) responsible for setting world standards in many electronics
areas. Members of the ISO are the national standards organizations of the
- International Telegraphic Union -
Telecommunications Standards Sector: (ITU-TSS) The replacement organization
for the CCITT.
- Internet: Made up of millions of smaller connected
networks. It is the largest computer network. Founded by the United States
Department of Defense. It was created for a fail safe computer system in case
of a nuclear attack. Expansion for popular use took place in the
- Internet Address: (IP Address) This is a 32
bit hardware independent address assigned to hosts using the TCP/IP: protocol
- Internet Assigned Numbers Authority: (IANA)
The central registry for various Internet protocol parameters, such as port,
protocol & ent4erprise numbers, & options, codes & types.
- Internet Control Message Protocol: (ICMP) A part of IP that
handles error & control messages. It is used by gateways & hosts to report
problems with the datagram to the original source. ICMP also has an echo
request/reply feature used to test whether a node is alive or dead.
- Internet Protocol: (IP) TCP/IP protocol governing packet
- Internet Relay Chat: (IRC) a means of
communicating with others over the internet, in Real Time via Text
- Internet Service Provider: (ISP) A
company that maintains a network that is linked to the internet via a dedicated
communication line, usually a high-speed link known as a T1. An ISP offers use
of its dedicated communication lines to companies & individuals. Using a modem,
you can dial up to a service provider whose computers will connect you to the
- Internet Society: (ISOC) A non-profit,
professional organization that supports the technical evolution of the Internet
& stimulates the interest of members of the scientific & academic communities,
industry, & the public regarding technology & the applications of the
- Internetwork: The ability to operate & exchange information
in a heterogeneous network.
- Internetwork Packet
Exchange: (IPX) NetWare protocol similar to IP.
The use of linking devices such as gateways, bridges & routers to connect
network systems of same or varied configurations.
The ability of two computers to communicate & exchange information with each
- Interprocess Communications: (IPC) A
protocol for data exchange between applications or threads.
- Interrupt Request: (IRQ) The method by which hardware
devices request processor attention.
- Inverted Backbone: A distributed
backbone in which a LAN is used for the backbone but it is physically contained
in a small area, , i.e. an equipment room. This is usually found in token ring
environments where 2 port bridges are connected to a 16MB backbone ring in the
- IOC: See Input-Output
- IP: See Internet Protocol
Address: See Internet Address
- IPC: See Interprocess Communications
- IPX: See Internetwork Packet Exchange
- IRC: See Internet Relay Chat
- IRQ: See Interrupt Request
- IRS: Ignition radiation
- ISA: See Industry Standard
- ISDN: See Integrated Services
- ISO: See International Standards
- ISOC: See Internet
- Isolation: The ability of a circuit or component to
reject interference, usually expressed in dB.
- ISP: See Internet Service Provider
- ISU: See Integrated Service Unit
- ITU-TSS: See International Telegraphic Union - Telecommunications Standards
Sector The replacement organization for the CCITT.