IC (integrated circuit) A solid state device with
miniaturized discrete active components on a single semiconductor
(International Electrotechnical Commission) A
European organization (headquartered in Geneva, Switzerland) involved
in international standardization within the electrical and electronics
fields. The U.S. National Committee for the IEC operates within
IDE (Intergrated Development Environments) Software platforms for
weighting code and creating new application software.
IDX (Inter-Exchange Carrier) A telecommunications service
provider authorized by the FCC to provide interstate long distance
communications services between LATAs; and authorized by the State
to provide long distance communications services. An InterExchange
Carrier provides, directly or indirectly, interLATA or intraLATA
telephone toll services. May be an individual, partnership,
association, joint-stock company, trust, governmental entity or
corporation engaged for hire in interstate or foreign communication
by wire or radio, between two or more exchanges.
IEEE (Institute of Electrical
and Electronic Engineers) The largest professional organization
for electrical engineers. Membership includes engineers,
scientists and students of electronics and allied fields. Primarily concerned with education and
standardization for computers and communications.
IEEE-488 also referred to as the
general purpose interface bus (GPIB). Most common parallel
format computer interface for simultaneous control of up to 15 multiple
A joint Apple and TI
implementation of the IEEE P1394 SerialBus Standard. It is a high-speed
(100/200/400 Mbits/sec now, with 1 Gbit/s on the horizon) serial
bus for peripheral devices. Supported by Apple, IBM, Intel, Microsoft
and Sony, Firewire supports automatic configuration ("plug
and play") and hot-plugging (live connection/disconnection of peripheral devices while
running without data loss or interruption). It is also isochronous, meaning
that a fixed slice of bandwidth can be dedicated to a particular
peripheral - video, for instance. Fast, inexpensive and reliable
it was originally developed to connect PCs to other PCs or to
peripherals such as digital cameras, camcorders, scanners, etc.
Current applications include automotive, telecom, data acquisition,
aerospace and a host of others. IEEE 1394 carries
all forms of digitized video and audio. A single Firewire interface
can be used for all peripheral interconnections, done
in a daisy-chain topology. See: USB
for a complementary searial buss system.
IETF (Internet Engineering Task Force) A large open
international community of network designers, operators, vendors,
and researchers concerned with the evolution of the Internet
architecture and the smooth operation of the Internet. It is open to
any interested individual.
IIR (infinite impulse-response) filter
A commonly used type of digital filter. This recursive structure
accepts as inputs digitized samples of the audio signal, and then
each output point is computed on the basis of a weighted sum of
past output (feedback) terms, as well as past input values. An IIR
filter is more efficient than its FIR counterpart,
but poses more challenging design issues. Its strength is in not
requiring as much DSP power as FIR, while
its weakness is not having linear group delay and possible instabilities.
IM or IMD (intermodulation distortion)
An audio measurement designed to quantify the distortion products
produced by nonlinearities in the unit under test that cause complex
waves to produce beat frequencies, i.e., sum and difference products
not harmonically related to the fundamentals. For example, two frequencies,
f1 and f2 produce new frequencies f3 = f1 - f2; f4 = f1 + f2; f5
= f1 - 2f1; f6 = f1 + 2f2, and so on. Numerous tests exist, each
designed to "stress" the unit under test differently.
The most popular follow:
IMD The most common IMD measurement. SMPTE standard RP120-1983
and DIN standard 45403 are similar. Both specify a two-sinewave
test signal consisting of a large amplitude low-frequency tone
linearly mixed with a high-frequency tone at ¼ the amplitude of
the low frequency tone. SMPTE specifies 60 Hz and 7 kHz mixed
4:1. The DIN specification allows several choices in both frequencies,
with 250 Hz and 8 kHz being the most common.
- CCIF, Twin-Tone, or Difference-Tone
IMD All these terms refer to the same test and are used interchangeably.
The test specifies two equal-amplitude closely spaced high frequency
signals. Common test tones are 19 kHz and 20 kHz for full audio
bandwidth units. While all combinations of IM distortion products
are possible, this test usually measures only the low-frequency
second-order product falling at f2-f1, i.e., at 1 kHz.
impedance The numerical measure of the complex reaction
to current flow that a general electrical network has when excited
with an ac voltage. Impedance is the AC equivalent of Resistance
on a DC circuit
Induction Whenever a magnetic
field in the region of a conductor is moving, or changing in
magnitude, such that magnetic field lines of flux are moving across
the conductor, an electric current is induced in the conductor.
infrasonic Generating or using
waves or vibrations with frequencies below that of audible sound.
Compare with subsonic - commonly used
(erroneously) to mean infrasonic.
Interface Hardware or Software that forms a link betwene
devices and allows them to communicate with each other.
Internet World wide network of computer systems.
Intranet information available on a private corporate
using the Internet model and HTTP Servers.
interlayer-transfer See: print-through
inverse square law Sound Pressure Level.
Sound propagates in all directions to form a spherical field.
The area of this sphere increases proportionally to the square of
the distance from the center. All of the sound energy is spread
equally over this increasingly large sphere. Thus, as the
distance from the source increases, the sound energy level per square
area decreases. This sound energy is therefore inversely
proportional to the square of the distance, i.e., doubling
the distance quarters the sound energy (the inverse square law),
SPL is attenuated 6dB for each doubling of distance from the
I/O (input/output) Equipment or data used to communicate
from a circuit or system to other circuits or systems, or the outside
IP (internet protocol) IP is the
most important of the protocols on which the internet is based.
Originally developed by the Department of Defense to support
communications between dissimilar computers across a network, IP is a standard describing
software that keeps track of the inter-network addresses for different
nodes, routes outgoing messages, and recognizes incoming messages.
It was first standardized in 1981. See TCP/IP.
IR ( Infrared ) energy in the
region of the
electromagnetic spectrum at wavelengths longer ( lower
frequencies ) than those of visible light, but shorter ( higher
frequencies ) than those of radio waves. In most ways IR radiation
behaves exactly the same as visible light except it is not visible
with the human eye.
ISDN (Integrated Services Digital Network)
A switched (dial-up) high-capacity digital telecommunication
network service based on an international telephone standard
providing for digital connectivity for transmitting audio,
data and video simultaneously over a single line. Bandwidth can be
used to provide multiple standard voice telephone calls, audio or
video conferencing. Comes in two versions see BRI and PRI.
(International Standards Organization or International
Organization for Standardization) Founded in 1947 and consisting
of members from over 90 countries, the ISO promotes the development
of international standards and related activities to facilitate
the exchange of goods and services worldwide. The U.S. member body
is ANSI. [Interesting tidbit:
according to ISO internet info, "ISO" is not an acronym!
It is a derived Greek word, from isos, equal. For example,
isobar, equal pressure, or isometric, equal length.
Take a small jump from "equal" to "standard"
and you have the name of the organization. It offers the further
advantage of being valid in all the official languages of the organization
(English, French & Russian), whereas if it were to be an acronym
it would not work for French and Russian.]
ISP (Internet Service Provider) Private company
providing connections to the Internet using one of several "last
mile" technologies such as 56K dial up modems and DSL.
ITU International Telecomunications Union International body that
sets worldwild telecommunications standards.