Fiber Optics Illustrated Dictionary - Part 9 ppsx

Fiber
Optics
Illustrated
Dictionary
that
supports
mid-range
speeds
and
the
transmission
of
both
voice
and
data
over
existing
copper-pair
wires.
ADSL
is
becoming
apopular
cost-effective
option
for
faster computer network access (e.g., Internet)
in
households
and

small
businesses.
It
enables
users
to
be
online
virtually
all
the
time
without
interfering
with
the
use
of
the
phone
for
voice
messages
or
having
to
dial
the
service provider
each

time
access
is
desired.
ADSL
services
are
competitive
with
cable
modem.
"Asymmetric"
refers
to
the
discrepancy
between
the
upstream
and
downstream
transmission
speeds.
Most
users
download
far
more
than
they

upload,
so
a
com-
promise
is
established
to
balance cost
and
speed.
Thus,
download
speeds
are
configured
to
be
faster
than
upload
speeds
(e.g.,
640
kbps
versus
8
Mbps).
Installation of
ADSL

service involves installing a
network
interface
device
(NID)
that
houses
a spliner
(a
low-pass
filter)
at
the
subscriber
premises.
Sepa-
rate
lines
run
from
the
splitter
to
the
phone
and
from
the
spliner
to

the
ADSL
remote
transceiver
(some-
what
like
a
traditional
modem)
which,
in
turn,
con-
nects
to
the
computer.
Software
to
handle
communi-
cations
is
installed
on
the
computer.
The
combined

telephone
and
ADSL
signals
travel
from
the
loop
to
the
subscriber
NID
where
the
signal
is
split.
The
tele-
phone
signal
is
then
directed
to
the
phone
set
and
the

ADSL
signal
is
directed
to
the
terminal
unit
(the
re-
mote
transceiver)
where
it
is
processed
and
transmit-
ted
to
a
network
interface
card
(NIC)
installed
in
the
computer.
Much

the
same
happens
in
the
reverse
di-
rection.
Phone
and
ADSL
signals
coming
from
the
subscriber premises
are
sent
to
the
central office
where a splitter sends phone signals
to
the
voice
switching
mechanisms
and
ADSL
signals

to
the
data
network
where
an
Internet
Services
Provider
handles
user
requests
such
as
Internet
access,
Web
hosting,
etc.
Copper
wire
lines
are
not
optimal
for
ADSL,
as
bridge
taps

and
load
coils
on
utility
poles
can
interfere
with
ADSL
signals.
See
Digital
Subscriber
Line
for
a
fuller
explanation.
See
cable
modem,
discrete
multi
tone,
G.lite,
UAWG.
asymmetric transmission A
transmission
channel

in
which
information
flows
more
readily
(faster)
in
one
direction
than
the
other,
or
moves
primarily
in
one
direction
or
the
other
at
anyone
time,
or
in
which
a
greater

volume
of
information
flows
in
one
direction
or
the
other.
There
are
many
instances
in
which
in-
formation
typically
flows
more
in
one
direction
than
another,
as
in
interactive
TV,

where
most
of
the
time
the
user
is
observing
and
not
transmining
but
may
make
an
occasional
request
for
a specific
movie
or
file.
The
medium
itself
may
not
be
inherently

asym-
metric.
For
example,
a
data
upload
over
a
modem
is
primarily
one-way,
but
the
line
capacity
is
two-way,
and
the
direction
can
be
easily
switched
when
upload-
ing.
The

slower
channel,
or
the
one
with
a
lower
vol-
ume
capacity,
may
be
called
the
backchannel.
asymmetrical compression
In
data
compression
techniques,
some
types
of
files
can
be
compressed
faster
than

they
can
be
decompressed
and
some
work
the
other
way
around.
In designing
compression
al-
gorithms,
sometimes
optimization
in
one
direction
or
72
the
other
is
preferred.
In
creating animation se-
quences,
it

is
usually
very
important
that
they
decom-
press
and
play
quickly;
otherwise
the
illusion ofmo-
tion
is
lost.
However,
it
is
usually
not
a
problem
if
the
compression
takes
longer
than

the
decompression
because
the
computer
can
handle
that
while
the
user
is
working
on
other projects.
asymmetrical modem A
modem
designed
to
favor
the
transmission of
the
bulk of
the
data
in
one
direc-
tion

over
the
other.
This
is
appropriate
in
situations
where
most
of
the
communication
is
one-way,
as
in
managing
an
archive
site,
where
downloads
typically
outnumber
uploads
thousands-to-one.
See
Asymmet-
ric

Digital Subscriber
Line.
asynchronous Not synchronous. A
concept
that
ap-
plies
across
many
areas
of telecommunications,
in
which
the
timing
of
the
information
being
received
and
transmined
is
not
predefined
and
may
be
unpre-
dictable,

as
in
many
modem
communications
and
in-
teractive
radio
communications.
This
type
of
commu-
nication
typically
requires
some
means
ofindicating
the
starting
and
stopping
points
of
the
transmission.
There
are

various
schemes
for
handling
this,
from
verbal
cues
("Roger"),
to
start/stop
bits,
and
various
handshaking
signals.
asynchronous balanced mode
ABM.
In
an
Interna-
tional
Business Machines
(IBM)
Token-Ring net-
work,
a service
in
the
logical

link
control
(LLC)
at
the
SNA
data
link
control
level
that
allows
devices
to
send
and
respond
to
data
link
commands.
asynchronous communications interface adapter
AClA.
A
data
formaning device
that
translates sig-
nals
between

the
computer
and
aperipheral
such
as
a
modem.
asynchronous
packet
assembler/disassembler
APAD.
A
mechanism
to
assemble
a
stream
of
bytes
from
an
asynchronous
source
(e.g., a
computer)
into
packets
and
transmit

them
to
a network,
and
vice
versa.
In
terms
of
serving
atranslation
function,
it
can
be
thought
of
as
loosely
working
like
a
traditional
mo-
dem,
which
takes
asynchronous digital signals
from
acomputer

and
modulates
and
demodulates
them
for
compatibility
with
an
analog phone
system.
In
the
case
ofa
PAD,
however,
the
data
is
being
packetized
and
sent
over
an
X.25
network
from
one

or
more
de-
vices
that
are
not
directly
X.25
compatible.
The
ITU-
T
has
defined
more
than
one
standard
for
perform-
ing
these
translation
functions
to
facilitate connec-
tions
with
X.25.

Examples
include:
X,3
basic packet data network assembly/disas-
sembly
X.5
packet
data
network
assembly/disassembly
for
facsimiles
X.29
packet
data
network
assembly/disassembly
control
information
and
user
data
exchange
procedures
X,39
packet
data
network
assembly/disassembly
control

information
and
user
data
exchange
procedures
for
facsimiles
.
See
X
Series
Recommendations.
asynchronous transfer mode
ATM.
A high-speed,
cell-based, connection-oriented, packet transmission
© 2003 by CRC Press LLC
protocol
for
handling
data
with
varying
burst
and
bit
rates.
ATM
is

a
commercially
significant
protocol
due
to
its
flexibility
and
widespread
use
for
Internet
con-
nectivity.
ATM
evolved
from
standardization
efforts
by
the
CCITT
(now
lTU-
T)
for
Broadband
ISDN
(B-

ISDN)
i~
the
mid-1980s.
It
was
originally related
to
Synchronous
Digital
Hierarchy
(SDH)
standards.
ATM
allows
integration
of
LAN
and
WAN
environ-
ments
under
a
single
protocol,
with
reduced
encap-
sulation.

It
does
not
require
a
specific
physical
trans-
port
and
thus
can
be
integrated
with
current
physical
networks.
It
provides Virtual Connection
(VC)
switching
and
multiplexing
for
Broadband
ISDN,
to
enable
the

uniform
transmission
of
voice,
data,
video
and
other
multimedia
communications.
See
Anchor-
age
Accord
for
information
on
acquiring
ATM
tech-
nical
specifications.
See
the
Appendix
for
details
and
diagrams
on

ATM
and
ATM
adaptation
layers.
AT
1.
See
access
tandem.
2.
advanced
technology
3.
AudioTex.
A
commercial
telephony-based
informa-
tion service, offering announcements, messages,
music,
meeting
schedules,
etc.
AT,
PC/AT
Advanced
Technology.
The
common

name
for
a
series
of
80286-based
personal
computers
introduced
by
International Business Machines
(IBM)
in
the
mid-1980s.
This
model
was
released
about
a
year
later
than
the
Apple
Lisa,
at
about
the

same
time
as
the
Apple
Macintosh,
and
about
a
year
before
the
Amiga
1000,
Apple
IIGS,
and
Atari
ST
computers.
This
is
historically
significant
in
the
de-
velopment
of
user

interfaces,
as
most
of
the
compet-
ing
computers
were
evolving
graphical
user
inter-
faces
(GUIs)
and
included
built-in
serial
ports
and
sound
cards,
while
most
of
the
AT
systems
were

text-
oriented
(primarily
MS-DOS),
with
sound
and
vari-
ous
interface
cards
optional.
The
IBM
AT
and
li-
censed
clones
from
other
manufacturers
were
pur-
chased
primarily
by
business
users,
in

part
because
the
IBM
name
was
well
known
in
the
business
in-
dustry,
and
also
because
IBM
had
a decades-old
tradition
at
the
time
of
providing
service
and
repair
options
to

business
owners.
Two
of
the
chief
software
products
used
on
the
AT
were
spreadsheets
and
word
processors.
AT
commands, Hayes Standard
AT
Commands A
very
simple
control
and
reporting
language
built
into
Hayes

Microcomputer
Products,
Inc.
modems,
and
Hayes-command-compatible
modems
from
other
manufacturers. Originally
modems
were
"dumb"
devices;
they
had
no
significant
memory
or
algo-
rithms
incorporated
into
the
device
to
process
com-
mands

or
data
from
the
computer.
Hayes
introduced
"smart"
modems
in
the
early
1980s
that
could
pro-
cess
a
limited
command
set
and
enhance
the
utility
of
modems.
This
instruction
set

has
since
been
in-
corporated
into
almost
every
make
and
model
of
com-
puter
modem,
usually
with
enhancements
by
indi-
vidual
manufacturers.
The
AT
command
set
allows
computer
control
of a

modem
and
provides
a
way
for
the
modem
to
report
information
back
to
the
computer
software.
The
AT
stands
for
"attention"
and
is
a
way
of alerting
the
modem
that
there

is
an
instruction
set
fo
Howing
the
"AT"
which
is
to
be
acknowledged
or
executed.
When
you
run
a
telecommunications
program
through
your
modem,
the
software
is
talking
to
the

modem
with
AT
commands
along
the
path
provided
by
the
serial
cable
that
typically
connects
the
modem
to
the
com-
puter.
If
your
software
can
be
set
to
interactive
mode,

you
can
type
the
AT
commands
directly
to
your
mo-
dem
and
see
what
happens.
The
AT
commands
are
usually
listed
at
the
back
of
the
manual
that
comes
with

a
modem.
Many
modem
manufacturers
have
included
supersets
of
the
basic
Hayes
command
set
to
provide
control
of
proprietary
or
enhanced
features
specific
to
their
products,
so
AT
commands
usually

include
most
or
all
of
the
Hayes
commands,
and
additional
ones
as
well.
AT
commands
fall
into
a
number
of
categories.
There
are
commands
for
querying
the
status
of
the

phone
line,
for
querying
the
status
of
the
modem,
and
for
carrying
out
operations
such
as
dialing,
setting
the
transmission
speed,
setting
the
number
of redials,
setting
the
length
of
wait

periods,
etc.
Modems
contain
a
number
of
registers
in
which
in-
formation
is
stored,
often
in
the
form
ofa
toggle
(true
or
false)
or
integer
setting.
Thus,
setting
the
register

to
zero
signifies
one
thing,
and
setting
it
to
one
or
another
integer,
when
appropriate,
signifies
another.
Thus,
AT
80=0
sets
the
"8' register
to
zero.
Since
register
SO
determines how many rings
to

AutoAnswer,
setting
it
to
zero
effectively
turns
off
AutoAnswer.
AT
SO=l
instructs the modem
to
AutoAnswer
after
it
detects
one
ring.
If
you
are
run-
ning
a
computer
bulletin
board,
or
a

friend
is
calling
to
send
you
a
file
over
the
phone
line,
AutoAnswer
can
be
turned
on
(or
you
can
type
ATA
"attention,
answer"
when
you
hear
the
phone
ring).

Remember
to
set
AutoAnswer
off
when
you
are
finished
trans-
mitting,
or
the
next
voice
caller
may
get
a
nasty
mo-
dem-blast
in
the
ear.
Some
modems
have
enhance-
ments

that
allow
them
to
autodetect
whether
the
in-
coming
call
is
voice
or
data
and
to
react
accordingly
so
this
doesn't
happen.
AT
80=0
M1
DT
555-4321
W
DT
123

attention;
set
autoanswer
to
zero
rings
set
speaker
to
be
on
(M!)
during
establishment
of
call
(so
you
can
hear
dial
tone
and
dialing)
and
off
during
connection
(so
you

don't
have
to
hear
the
modem
sounds)
dial
tone
mode
555-4321
wait
for
dial
tone
dial
tone
mode
123
(to
dial
an
inner
extension,
for
example).
AT
commands
can
be

combined.
You
needn't
type
AT
in
front
of
each
individual
instruction.
For
example,
you
might
wish
to
initialize
your
modem,
and
dial
out
as
a
single
string
of
commands.
73

© 2003 by CRC Press LLC
Fiber
Optics
Illustrated
Dictionary
AT
&T
American
Telephone
and
Telegraph
Company.
A company established almost
150
years
ago
to
cre-
ate
practical
commercial
applications
from
the
early
telegraph
and
telephone
patents
filed

in
the
1870s,
primarily
those
of
Alexander
Graham
Bell
and
Elisha
Gray.
Some
of
the
patents became
the
property of
the
Bell
System,
and
some
served simply
as
competitive
motivation
to
implement
the

new
ideas
and
technologies.
The
American
Telephone
and
Telegraph
Company
(AT
&T)
began
as
a long-distance subsidiary of
the
American
Bell
Telephone
Company
in
1885.
In
1899
the
two
companies
were
again
merged

into
one
un-
der
the
AT&T
name.
In
the
1900s,
AT&T
was
reor-
ganized,
becoming
aholding
company,
the
parent of
the
Bell
companies
and
Western
Electric.
In
the
en-
suing years, several additional reorganizations
oc-

curred,
some
voluntary,
some
mandated
by
u.S. jus-
tice
authorities.
In
the
early
1900s,
there
was
a period
of
substantial
change
in
the
phone
industry,
since
the
original Bell
patents, protected
for
a
term

of
17
years,
were
expir-
ing
and independent companies
were
entering
the
phone
market
in
substantial
numbers.
This
situation
resulted
in
independents
collectively holding
almost
half
of
the
phones
until,
by
1913,
AT&T

was
again
the
majority
holder,
due
to
mergers
and
acquisitions,
and
was
legally restrained
from
acquiring
any
more
independents.
AT&T
was
also
mandated
to
permit
in-
dependents
to
use
the
AT&T

toll
lines.
The
Communications
Act
of
1934
further regulated
the
industry
and
established
the
Federal
Communi-
cations
Commission
(FCC),
which
was
given jwis-
diction
over
the
telephone
and
broadcast industries,
a responsibility
it
still

holds.
In
1956,
the
u.s.
gov-
ernment
and
AT&T
entered
into
an
agreement that
AT
&T
would
offer
only
phone-related services
and
not
engage
in
common
carrier communications
such
as
computer
network
services.

AT&T
was
further
re-
quired
to
license Bell patents
for
royalties
to
inter-
ested applicants.
A
number
of
antitrust
suits
ensued
in
the
1970s
charg-
ing
AT&T
with monopolistic practices,
and
there
were
calls
for

divestiture resulting
in
divestiture
pro-
ceedings
in
the 1980s. During this same period,
AT
&T
was
granted
limited permission
to
engage
in
computer-related
services.
While
its
political history
was
undergoing
many
ups
and
downs,
the
researchers
in
the

Bell
Laboratories
provided
an
enormous
amount
ofresearch
and
devel-
opment
in
telephone
technologies, beginning
in
the
late
1800s
and
early
1900s.
AT&T
researchers
devel-
oped
the
first
two-wire
telephone
circuit,
which

is
still
in
use
today,
the
first
practical transistor,
and
many
other
inventions
that
are
in
broad
use.
See
Bell,
Alex-
ander;
Bell Laboratories; Bell
System;
Carty,
John
1.;
Kingsbury Commitment; Modified Final Judg-
ment;
Vail,
Theodore.

AT&T
TeleMedia
Connection A Microsoft
Win-
dows-based videoconferencing product
from
AT&T
Global
Information
Solutions
providing
audio/video,
file
transfer,
and
application-sharing utilities over
ISDN
through
ITU-
TH
Series
and
Q
Series
Recom-
74
mendations standards and encoding techniques.
Atanasoff, John
Vincent
(1903-1995) An

American
physicist
and
inventor
who
developed a
vacuum
tube
calculating device
in
the
mid-1930s that foreshad-
owed
the
famous
ENIAC
computer that
was
opera-
tional
in
the
post-World
War
II
years. In
1939,
with
a
small

grant
from
Iowa
State College,
he
pioneered
the
development
of
a binary
logic
computer called
the
ABC,
or AtanasofI-Berry
Computer,
with
assis-
tance
from
Clifford Berry a recent graduate
in
elec-
trical
engineering.
Unfortunately,
the
War
brought
the

project
to
a
halt.
He
left
his
academic position
to
be-
come
Chief
of
the Acoustics Division
of
the
u.S.
Naval Ordnance Laboratory where
he
worked
on
computing
devices
for
the
Navy
along
with
atomic
testing.

In
the
1950s,
Atanasofftook a
number
of
cor-
porate positions
and
retired
in
1961.
See
Atanasoff-
Berry
Computer;
Berry,
Clifford
E.
Atanasoff-Berry Computer
ABC.
Apioneering
bi-
nary, direct logic computer with a regenerative
memory,
designed
and
built
by
J.

V.
Atanasoffwith
assistance
from
Clifford
E.
Berry.
After
two
years
on
the
drawing
boards,
it
was
prototyped
in
1939.
It
is
significant not only
for
its
historic place
in
the
early
history
of

computers,
but
also
because
it
was
designed
with
aseparation between
memory
and
data
process-
ing
functions. The electricity needed
to
keep the
memory
refreshed,
so
the
information
wasn't
lost,
was
provided
by
rotating
drum
capacitors.

Atanasoff
had
been working
on
the
ideas
that
led
up
to
the
ABC
since
1935
and
related that
the
idea
for
the
ABC
came
to
him
in
aroadhouse
in
1937
after
he

and
his
graduate students had developed a calculator
for
complex
mathematics
manipulation.
Punch
cards,
which
had
been developed
to
store information
for
electromechanical devices
in
the
late
1800s,
were
used
to
enter data
into
the
ABC.
In
1940,
Atanasoff

and
Berry authored
Computing
Machines
for
the
So-
lution
of
Large
Systems
o/Linear
Algebraic
Equations
with
illustrations,
in
preparation
for
a patent appli-
cation
that
was
never
completed
due
to
circumstances
associated with
World

War
ll.
Much
of
the
information aboutAtanasoff's invention
did
not
come
to
light
until
a
long
court battle
in
the
1970s
between Sperry
Rand
and
Honeywell.
Unfor-
tunately,
after Atanasoff left
for
a position
with
the
u.S.

Navy,
the
computer
was
dismantled, without
notifying the inventors. The Ames Laboratory
is
building a working replica
of
this
historic
invention.
See
ENIAC;
Zuse,
Konrad.
Atari Corporation Ahistorically significant
games
and
computer
company
established
in
1972
by
Nolan
Bushnell.
Atari
shipped
the

first computer
game
to
achieve
wide
commercial acceptance. "Pong"
was
a
simple monochrome game with a ball and two
paddles,
a
form
of
electronic
table
tennis
that
became
wildly
popular.
Atari
continued
developing
games
but
also
subsequently introduced a
number
of
microcom-

puters, including
the
Atari
800
and
the
Atari
520ST.
The
520ST had a graphical interface and built-in
MIDI
and
was
competitive
with
the
Amiga
for
the
home
market
in
the
mid-1980s.
© 2003 by CRC Press LLC
ATB
See
all
trunks
busy.

ATCA
See
Antique
Telephone
Collectors
Association.
ATCP
See
AppleTalk
Control
Protocol.
ATCRBS
air
traffic
control
radar
beacon
system.
ATD
1.
asynchronous
time
division.
2.
Attention
Dial.
A
modem
command
from

the
Hayes
set
that
instructs
a
modem
to
dial
the
number
following
the
command.
Often
a T
or
P
will
precede
the
number
to
indicate
whether
to
dial
as
a
tone

or
pulse
signal.
For
example,
Attention
Dial
Tone
would
be
ATDT
555-1234.
3.
advanced
technology
demonstration.
ATDRSS
See
Advanced
Tracking
and
Data
Relay
Satellite
System.
ATEL
See
Advanced
Television
Evaluation

Labora-
tory.
ATG
1.
See
address
translation
gateway.
2.
Art
Tech-
nology
Group
Inc.
An
e-commerce
platform
devel-
opment
vendor.
Athena project,
Project
Athena A project of
the
Massachusetts
Institute
of
Technology
(MIT)
Com-

puter
Science
Lab
begun
in
1984.
The
goal
was
to
take
various
incompatible computer systems,
and
develop
a
teaching
network
that
could
utilize
the
dif-
ferent
resources
of
each
in
a
consistent

manner.
The
development
of
The
X
Window
System
originated
from
efforts
to
provide a graphical user interface
(GUI)
for
Athena.
See
X
Window
System.
ATI
1.
Accelerated
Technology
Incorporated.
A
com-
mercial
supplier
of

realtime
operating
system
(RTOS)
source
code
for
embedded
systems,
based
upon
the
Nucleus
PLUS
multitasking
kernel.
2.
Advanced
Telecommunications,
Inc.
A
commercial
vendor
of
telecommunications-related
system
design,
installa-
tion,
and

training.
ATI
is
one
of
several
firms
associ-
ated
with
Applied
Cellular
Technology.
3.
See
Ad-
vanced
Telecommunications
Institute.
ATIS
1.
Advanced
Travelers
Information
System.
A
forum
of
SAE
International,

an
engineering
society
for
advancing
transportation
mobility.
2.
See
Alliance
for
Telecommunications
Industry
Solutions.
ATM
1.
See
asynchronous
transfer
mode.
2.
See
Au-
tomated
Teller
Machine.
ATM-PON
asynchronous
transfer
mode

passive
op-
tical
networks.
A
type
of
optical
distribution
network,
promoted
as
a
means
to
implement
large-scale,
full-
service
subscriber
telecommunications
services.
See
fiber
to
the
home.
ATM Adaptation
Layer
AAL.

A
layer
in
an
ATM
network.
See
asynchronous
transfer
mode
in
the
Ap-
pendix
for
extended
information
and
diagrams.
ATM cell
The
basic
unit
ofinfonnation
transmitted
through
an
ATM
network.
An

ATM
cell
has
a
fixed
length
of
53
bytes,
consisting
ofa
44-
or
48-
byte
pay-
load
(the information transmitted),
and
a 5-byte
header
(addressing
information)
with
optional4-byte
adaptation
layer
information.
Interpretation
of

signals
from
different
types
of
media
into
a
fixed
length
unit
of
data
makes
it
possible
to
accommodate
different
types
of
transmissions
over
one
type
of
network.
See
asynchronous
transfer

mode;
see
the
Appendix
for
details
and
diagrams.
ATM cell
rate
In
ATM
networks, a concept that
expresses
the
flow
of
basic
units
of
transport
used
to
convey
data,
signals,
and
priorities.
Common
cell

rate
concepts
include
leaky
bucket
and
cell
rate
margin.
See
ATM
Cell
Rate
Concepts
Table.
ATM
endpoint
In
an
ATM
network,
the
point
at
which
a connection
is
initiated
or
terminated.

See
asynchronous
transfer
mode.
ATM endpoint address A
location
identifier
func-
tionally
similar
to
a
hardware
address
in
an
ATMARP
environment,
although
it
need
not
be
tied
to
hardware.
See
asynchronous
transfer
mode,

ATM
endpoint.
ATM
Forum,
The
An
international
nonprofit
orga-
nization
founded
in
1991
to
further
the
evolution
and
implementation
of
asynchronous transfer
mode
(ATM)
technology
as
a
global
standard.
The
Forum

provides
educational
information
onATM
and
speci-
fications
and
recommendations
to
the
lTU-T
based
on
standards
of
interoperability
between
vendors,
with
consideration
to
the
needs
of
the
end-user
com-
munity.
The

ATM
Forum
is
a membership-by-fee
group
which
includes
a
number
of
technical
commit-
tees
to
discuss
and
report
on
specific
issues
such
as
signalling,
traffic
management,
emulation,
security,
testing,
and
interfacing.

See
asynchronous
transfer
mode,
UNI.
http:/www.atmforum.com/
ATM
hardware
address
The
individual
IP
station
address.
See
asynchronous
transfer
mode,
ATM
end-
point
address,
Internet
Protocol.
ATM line interface
ALI.
A
device
at
the

physical
layer
enabling
connection
to
a
variety
of
physical
me-
dia
allowing,
for
example,
the
accommodation
of
dif-
ferent
line
speeds.
ATM
Link
Enhancer
ALE.
A
commercial
error-cor-
recting
mechanism

for
satellite
communications
de-
veloped
by
COMSAT.
The
Header Error Control
(HEC)
specified
for
asynchronous transfer
mode
(ATM)
is
suitable
for
transmissions
carried
through
low
error
rate
media
such
as
fiber
optic
cables.

It
be-
comes
inadequate,
however,
in
bursty
transmissions
environments
such
as
wireless
networks,
particularly
those
that
are
satellite-based.
To
compensate
for
this
limitation,
COM
SAT
developed
an
ALE
module
which

is
inserted
in
the
data
paths
before
and
after
the
satellite
modems,
to
isolate
ATM
cells
from
burst
errors.
This
module
allows
selective
interleaving
of
ATM
cells
before
they
are

transmitted
through
the
satellite
link,
thus
providing a
lower
bit error
rate
(BER)
and
an
improved
cell
loss
ratio
(CLR).
See
asynchronous
transfer
mode,
cell
rate.
ATM models
There
are
a
variety
of

types
and
imple-
mentations
of
ATM
networks,
including
Classical
IP,
LANE,
IP
Broadcast
over
ATM,
and
others.
See
asyn-
chronous transfer
mode,
ATM
Transition Model,
Classical
IP
Model,
Conventional
Model,
Integrated
Model,

Peer
Model.
See
Appendix
B
for
details
and
diagrams.
ATM slotA
time
indicator
for
the
duration
of
one
cell,
usually
described
in
microseconds.
It
will
vary
de-
pending
upon
the
cell-carrying

medium.
In
ATM,
one
use
of
the
term
slot
is
to
describe
delay
in
switch
performance.
See
asynchronous transfer mode,
ATM
cell.
75
© 2003 by CRC Press LLC
Fiber
Optics
Illustrated
Dictionary
AIM
switch
processor
ASP. A modular component

from Cisco Systems that provides cell relay, signal-
ing, and management processing functions.
It
in-
cludes an imbedded
IOO-MHz
MultiChannel Inter-
face Processor (MIP) R4600 RISC processor, with
ATM access
to
the switch fabric,
to
provide high call
setup rates and low call setup latencies. It includes
an Ethernet port and dual serial ports.
The ASP works in conjunction with a field-replace-
able feature daughtercard which supports advanced
ATM switch functions, including intelligent packet
discard, dual leaky bucket traffic policing, and avail-
able bit rate (ARR) congestion control mechanisms.
See asynchronous transfer mode.
AIM
traffic
descriptor
A list
of
network traffic pa-
rameters, such as cell rates and burst sizes, and, op-
tionally, a Best Efforts (BE) indicator, within
an

asyn-
chronous transfer mode (ATM) virtual connection.
This information is used
to
determine traffic charac-
teristics and
to
allocate resources. See asynchronous
transfer mode, BEC, cell rate, PCR, SCR.
AIM
Transition
Model
A model lying between the
Classical IP Models and the Peerand IntegratedMod-
els. See ATM models.
AIM
Wireless
Access
Communication
System
AWACS. An ACTS project to support and influence
emerging ATM wireless standards. The project con-
sidered various link level and system level simula-
tions
in
order to research system concepts based on a
19-GHz air interface. It also addressed the feasibil-
ity
of
different modulation schemes and

of
directional
antenna technology. See Advanced Communications
Technologies and Services.
AIMARP
ATM
Address
Resolution
Protocol.
ATMARP
is
the ATM Address Resolution Protocol
(ARP) with extensions
to
support address resolution
in a unicast server environment. ATMARP provides
a means
of
resolving Internet Protocol
(LP)
addresses
to
ATM addresses. ATMARP use
of
public UNI ad-
dresses
or
ATM endpoint addresses is similar to
Ethernet addressing; ATM addresses need not be tied
to

hardware. lnATMARP (Inverse ATMARP)
is
used
AIM
Cell
Rate
Concepts
Abbreviation
Name
Notes
ACR
allowed cell rate A traffic management parameter dynamically managed by
congestion control mechanisms. ACR varies between the
minimum cell rate (MCR) and the peak cell rate (PCR).
CCR
current cell rate
A traffic flow control concept that aids in the calculation
ofER.
The CCR may not be changed by the network
elements (NEs). CCR
is
set by the source
to
the available
cell rate (ACR) when generating a forward RM-cell.
CDF
cutoffdecrease factor
Controls the decrease in the allowed cell rate (ACR)
associated with the cell rate margin (CRM).
CIV

cell interarrival variation
Changes
in
arrival times
of
cells nearing the receiver.
If
the cells are carrying information that must be
synchronized, as
in
constant bit rate (CBR) traffic, then
latency and other delays that cause interarrival variation
can interfere with the output.
GCRA
generic cell rate algorithm
A conformance enforcing algorithm which evaluates
arriving cells. See leaky bucket.
ICR
initial cell rate
A traffic
flow
available bit rate (ARR) service parameter.
The ICR
is
the rate at which the source should be sending
the
data.
MCR
minimum cell rate
Available bit rate (ABR) service traffic descriptor. The

MCR
is
the transmission rate
in
cells per second at which
the source may always send.
PCR
peak cell rate
The PCR
is
the transmission rate
in
cells per second that
may never be exceeded, which characterizes the constant
bit rate (CBR).
RDF
rate decrease factor
An available bit rate (ABR) flow control service
parameter that controls the decrease
in
the transmission
rate
of
cells when
it
is
needed. See cell rate.
SCR
sustainable cell rate
The upper measure

of
a computed average rate
of
cell
transmission over time.
76
© 2003 by CRC Press LLC
on
AIM
networks
supporting penn
anent
virtual
con-
nections
(PVCs).
Inverse Address Resolution Proto-
col
(InARP)
supports
dynamic
address
resolution
en-
abling a
protocol
address
corresponding
to
a given

hardware
address
to
be
requested.
See
asynchronous
transfer
mode
and
the
Appendix
for
a fuller explana-
tion
of
ATM.
See
RFC
1293,
RFC
1577.
atmosphere
1.
Ambience,
mood,
feeling
about a
lo-
cation

or
room.
2.
A gaseous
mass
enveloping a
ce-
lestial
body.
See
atmosphere, Earth's.
atmosphere,
Earth's
The gaseous envelope sur-
rounding
the
Earth which provides breathable
air,
moisture, weather variations, protection
from
the
sun's radiation, especially
the
ultraviolet rays,
and
particles
which
deflect radiant
energy
that

can
be
har-
nessed
for
telecommunications.
Atmospheric
pressure
at
sea
level
is
approx.
14.7
pounds per square
inch,
with
local
weather variations,
and
decreases
some-
what
uniformly
as
altitude increases. Barometers
are
used
to
measure

atmospheric weather,
and
baromet-
ric
altimeters indicate altitude through changes
in
pressures
in
the
atmosphere.
The
atmosphere
has
been divided
into
three
main
re-
gions.
From
the
surface going
away
from
the
Earth,
they are
the
troposphere, stratosphere, and iono-
sphere.

See
ionosphere.
ATN
See
Aeronautical Telecommunications Net-
work.
atomA
fundamental
unit
of
energy
or
matter
(depend-
ing
upon
how
you
look
at
it)
that
is
the
essential
build-
ing
block
of
molecules

which,
in
tum,
are
fundamen-
tal
building
blocks
ofelements.
An
atom
is
chemi-
cally indivisible.
However,
from
a physics point
of
view,
atoms
are
described
in
terms
of
even
smaller
components, including protons, neutrons
and
their

associated electrons.
In
the
weird
and
wild world of
quantum
physics, there
are
even smaller units
of
en-
ergy
called
quarks
and
other
atomic
interactions yet
to
be
fully
understood.
atomic clock
An
instrument devised
in
the
1940s
for

precise
timing
and
synchronization,
it
is
now
particu-
larly
important
in
the
u.S.
Global
Positioning
Sys-
tem
(GPS)
and
many
scientific research applications.
An
atomic
clock
uses
the
frequency associated with
a
quantum
transition between

two
energy
levels
in
an
atom
as
its
reference.
It exploits
the
unique
frequency
characteristics
of
photons in a given transition.
Atomic
clock
is
actually ageneral category
name
for
oscillators
whose
characteristics
are
based
on
quan-
tum

mechanical energy state transitions. Advanced
atomic
clocks
can
be
accurate
to
within fractions
of
a
second
over
hundreds
of
thousands of
years.
Space-
based
atomic
clocks
can
be
designed
to
be
more
ac-
curate than Earth-based atomic clocks
due
to

the
lesser influence
of
the
Earth's
gravity.
Coordinated
Universal
Time
(UTC)
reporting
centers
make
use
of
atomic
clocks
for
establishing
an
inter-
national
time
reference. Atomic
clocks
can
be
used
to
validate satellite

data
for
integrity
and
accuracy
for
use
in
navigational applications. Synchronization
between transmitting
and
receiving telecommunica-
tions
stations
can
be
maintained
by
means
of
atomic
clocks
or
by
a
set
of
less
expensive timing devices
which,

in
tum,
can
derive their timing
from
the
more
expensive atomic
clocks.
In
the
early
1990s,
atomic
clocks
were
improved
with
the
introduction
of
a Hewlett-Packard cesium-beam
clock which
was
more
rugged
and
more
stable
than

previous models.
Europe's Geostationary Navigation Overlay
System
(EGNOS)
is
being designed
to
use
cesium
and
ru-
bidium
atomic
clocks
to
provide System
Time
(ST)
for
calculating precise navigation infonnation
for
GPS-based
land,
marine,
and
air transportation
sys-
tems.
By
using

atomic
clocks
and
GPS
data
from
sat-
ellites, rather than traditional beacon-based
naviga-
tional
methods, accuracy can
be
established within
seven
meters.
Computers that
are
permanently
or
frequently
con-
nected
to
the
Internet will sometimes
be
configured
to
poll
the

U.S.
Naval
Observatory
atomic
clock
to
synchronize their
system
clocks with
the
time
on
the
Navy's
clock.
This
synchronization
is
useful
for
time-
sensitive
file
and
database
management
and
for
time-
critical e-commerce applications

such
as
stock
and
auction transactions. Accurate time-stamp
informa-
tion
is
also
useful
for
computer-based
legal
transac-
tions
and
event tracking.
The
National Institute
of
Standards
and
Technology
(NIST)
sponsors a
Web
site called "A
Walk
through
Time"

that features infonnation
and
illustrations
on
time-keeping through the
ages
and
the
development
of
atomic
clocks.
See
Coordinated Universal
Time,
Datum
Corporation, Global Positioning
System.
/>atomic laser A device or process that
emits
matter
in
the
same
general
sense
as
an
optical laser
stimu-

lates
the
emission ofcoherent pulses
of
light.
Such
a
laser
was
developed
out
of
research
on
Bose-Einstein
condensates
in
the
mid-1990s by
W.
Ketterle
et
al.
at
MIT.
Rather
than
using
mirrors
to

deflect
light
within
an
optical
cavity,
they
used magnetic
fields
to
deflect
matter
in
a magnetic cavity, using sodium atoms,
which
are
magnetically sensitive,
as
the
"ammuni-
tion"
for
the
atomic laser "gun."
As
energy
is
built
up, a pulse
of

coherent matter manages
to
break
through
the
magnetic barrier
in
much
the
same
way
as
pulses
of
light break through
the
semitransparent
mirrors of
an
optical
cavity.
The
system
was
success-
fully
demonstrated
and
described
in

1997.
By
Spring
2002,
the
scientists
had
found
a way
to
emit
a
con-
tinuous stream
of
atoms.
The
potential
for
this
technology
in
terms
ofdesign-
ing
complex crystal lattices, diffraction gratings, cir-
cuit boards
and
other fabrications important
to

the
semiconductor industry
may
be
very
great.
The
sys-
tem
works
in
the
environment
of
a
vacuum,
so
it's
not
quite
as
easy
to
set
up,
but
it
is
fascinating
tech-

nology which will
no
doubt
by
harnessed
in
exciting
ways.
For their discoveries,
the
inventors received a
Nobel
Prize
in
physics
in
2001.
See
laser.
atomic
number
Anumber characteristic determined
by
experimentation, since
the
atom
is
far
too
small

77
© 2003 by CRC Press LLC
Fiber
Optics
Illustrated
Dictionary
to
be
seen
by
any
natural
or
microscopic
means.
This
number
is
used
to
represent
an
element
in
a periodic
table
and
describes
electrons
in

relation
to
the
pro-
tons
in
a
neutral
atom.
ATS
1.
See
Applications
Technology
Satellite
pro-
gram.
2.
Automation
Tooling
Systems.
ATSC
See
Advanced
Television
Systems
Committee.
ATSC Digital TV
Standard
- Examples

Doc.
Date
Description
Al80
Jul
99
Modulation
and
Coding
Requirements
for
Digital
TV
(DTV)
Applications
over
Satellite.
Modulation
and
data
coding
for
satellite
communications
are
defmed
for
a
variety
of

programming
types,
including
video,
audio,
data,
multimedia,
or
others.
It
includes
multiplexed
bit
streams
such
as
MPEG-2.
Al64A
May
00
Transmission
Measurement
and
Compliance
for
Digital
Television
describing
test,
monitoring,

and
measuring
methods.
Al65A
May
00
The
Program
and
System
Information
Protocol
for
Terrestrial
Broadcast
and
Cable,
providing
a
methodology
for
transporting
digital
television
data
and
electronic
program
guide
data

with
an
amendment
on
Directed
Channel
Change
(DCC)
for
program
tailoring.
Al90 JulOl
The
Data
Broadcast
Standard
defining
protocols
for
data
transmission
compatible
with
digital
multiplex
bit
streams
according
to
ISOIIEC

13818-1
(MPEG-2
systems)
standards.
The
standard
encompasses
both
non-
TV
and
TV
programming,
including
Webcasting,
streaming
video,
etc.
Al53B
Aug
01
The
Digital
Television
Standard
for
advanced
television
(ATV)
systems.

The
document
specifies
the
parameters
and
video
encoding
input
scanning
format,
along
with
preprocessing
and
compression
parameters
of
the
video
encoding.
It
describes
audio
encoder
signal
formats,
preprocessing,
and
compression,

as
well
as
the
service
multiplex
and
transport
layer
characteristics
and
specifications.
ATSC
Digital
Television
Standard
ATSC
DTS.
The
78
Advanced Television Systems
Committee
(ATSC)
Technology
Group
on
Distribution
released
the
ATSC

Digital Television Standard in September
1995
(Document
AJ53)
along
with Document
A/54
which
describes
use
of
the
DTS.
The
DTS
is
based
upon
the
ISO/IEC
MPEG-2
Video
Standard,
the
Digital
Au-
dio
Compression
(AC-3)
Standard,

and
the
ISOIIEC
MPEG-2
Systems
Standard.
It
was
part of
an
ongo-
ing
effort
to
upgrade consumer broadcasting pro-
gramming
and
equipment
to
reflect
improvements
in
technology.
The
Digital
Television
Standard
was,
in
large

part,
adopted
by
the
Federal Communications
Commis-
sion
(FCC)
in
December
1996
as
well
as
by
Canada
and
some
Asian
and
South
American countries.
This
influential
document
was
revised
by
the
ATSC

and
released asAJ53AinApri12001.
It
specifies
the
tech-
nical
parameters of
advanced
TV
systems.
Examples
of
standards
include
those
listed
below.
See
Advanced
Television
Standards
Committee.
ATSE
Academy
of
Technological Sciences
and
En-
gineering.

/>ATT
See
Automatic
Toll
Ticketing.
attachment
Something
connected
to
or
with.
In
data
communications, a
note
or
file
that
is
attached
to
the
end
of
an
existing
file
or
other electronic
communi-

cation.
Commonly,
binary
files
are
sent
with
email
messages
as
attachments because
the
message
text
part
of
many
email
systems
cannot
transcribe
or
trans-
mit
8-bit binary
code.
The
system
will convert
the

bi-
nary
attachment
to
a compatible
mode
(e.g., 7-bit
text)
and
reconvert
it
back
to
binary
at
the
destina-
tion.
An
email
binary attachment
allows
you
to
send
apicture,
sound
file,
Adobe
PostScript

document,
or
other nontext transmission
in
conjunction
with
regu-
lar
text.
attachment unitinterface, autonomous unitinter-
face
AUI.
Certain
cables
and
connectors
used
to
at-
tach
equipment
to
Ethernet
transceivers.
Commonly
Ethernet connections
are
made
via a printed circuit
board installed

in
a
slot
in
acomputerwith a
BN
C
or
RJ-45
connector protruding
from
the
computer
for
making
the
connection
to
the
Ethernet
transceiver
and
cable.
The
ANSI/IEEE
standard
802.3
(originally
re-
leased

as
Document 1802.3-1991) defines
an
AUI
physical layer interface called
DB-15
or
DIX.
attack time
The
time
it
takes
for
asignal
or
sound
to
go
from
its
initiation
to
its
full
volume
or
power.
On
a violin,

for
example,
it's
the
time
interval
from
the
moment
the
bow
begins
to
move
and
a
consistent
note
achieves
its
full
volume
and
tone.
The
attack
time
on
an
electronic system

is
the
time
it
takes
from
the
ini-
tiation ofapulse,
signal,
or
power-on
action
until
the
system
reaches
its
intended
activation
threshold,
out-
put,
or
throughput
level.
See
decay
time.
ATTC

See
Advanced
Television
Test
Center.
attempt An effort
to
initiate
or
establish a
commu-
nications connection. In
some
systems
that
are
billed
on
a
flat
rate
or
per-call
basis,
attempts
are
not
billed.
In
other

systems,
such
as
those
that
bill
by
air
time,
the
attempts
are
charged
by
the
minute
or
second
whether
or
not
the
call
is
connected.
© 2003 by CRC Press LLC
attenuation
The
decrease
between

the
power
of
the
initial
transmission
and
its
power
when
received
or
measured
at
specified
points,
usually
expressed
as
a
ratio
in
decibels.
Loss
in
power
can
result
from
dis-

tance,
transmission
lines,
configurations,
faults,
and
weather.
See
absorption,
contrast
with
gain.
attitudeandarticulation controlsubsystem
AACS.
A spacecraft guidance system employed
on
the
Cassini
spacecraft
mission
to
permit
dynamic
con-
trol
of
rotation
and
translation
maneuvers.

The
AACS
uses
star
and
sun
sensors
to
establish
reference
points
for
determining
its
position.
The
main
engine
and
smaller
engines
are
used
for
propulsive
maneuvers.
Sensors
estimate
attitude
and

rate
of
both
the
base
body
and
the
articulated
platforms.
A
series
of
vec-
tors,
kinematically
propagated
in
time,
aids
the
sys-
tem
in
detennining
motion
of
various
bodies
in

rela-
tion
to
the
base
frame.
The
AACS
works
in
conjunc-
tion
with
the
command
and
data
subsystem
(CDS),
which
is
the
main
processor
on
the
craft.
The
CDS
receives

RF
signals
from
Earth
and
sends
informa-
tion
and
control
parameters
to
other
systems,
such
as
the
AACS,
accordingly.
See
Cassini.
atto-(symb. -
a)
Used
as
a
prefix
to
represent
a

very
minute
quantity,
one
quintillionth
of,
10-
18
•
See
femto
ATU
See
African
Telecommunications
Union.
ATU-C
ADSL
transceiver unit-central
office.
A
mo-
dem-like
device
installed
at
telephony
central
offices
to

process
data
communications
received
from
the
subscriber
that
are
then
fOlWarded
through
a
data
net-
work
to
a
subscriber-chosen
data
services
provider.
See
Asymmetric
Digital
Subscriber
Line.
ATU-R
ADSL
transceiver

unit-remote.
A
modem-
like
device
installed
on
the
subscriber
premises
to
process
data
communications.
It
typically
interfaces
between
the
computer
and
a
network
interface
device
splitter.
See
Asymmetric
Digital
Subscriber

Line.
ATV
1.
See
advanced
TV.
2.
See
amateur
television.
ATVEF
See
Advanced
Television
Enhancement
Fo-
rum.
ATVEF Enhanced
Content
Specification A
foun-
dation
specification
developed
by
the
Advanced
Tele-
vision Enhancement Forum for the creation
of

HTML-enhanced television content. It focuses
mainly
on
existing
technologies
rather
than
promot-
ing
new
ones,
laying
out
a
means
for
providing
and
viewing
broadcast
programming
on
the
World
Wide
Web
or
through
specialized
viewing

software
simi-
lar
to
Web
browsers.
It
promotes
the
reliable
trans-
mission
ofa
variety
of
types
of
broadcasts
through
Internet,
cable,
and
land-based
networks
to
comput-
ers,
enhanced
televisions,
and

dedicated
enhanced
TV
consumer
appliances.
The
specification
is
intended
to
encompass
both
one-way
and
two-way
systems
and
both
analog
and
digital
systems.
See
Advanced
Television
Enhancement
Forum,
broadcast
data
trig-

ger.
audible ringing tone An
audible
signal
transmitted
to
the
calling
party
to
let
the
caller
know
that
the
called
number
is
ringing.
See
busy
signal.
audible sound
Sound
waves
that
are
perceived
by

the
ear/brain
ofa particular
species.
Audible
sound
ranges
vary
from
species
to
species,
with
humans
hearing
generally
between
the
ranges
of20
to
20,000
hertz.
The
upper
ranges
tend
to
drop
off

during
the
teenage
years
and
decline gradually throughout a
person's
lifetime.
Illnesses,
very
sudden
loud
noises,
protracted
loud
noises,
and
sustained
low
level
noises
can
have
profound
negative effects
on
a
person's
hear-
ing.

See
audio,
sound.
audio
Pertaining
to
sounds,
primarily
those
within
range
of
human
perception,
from
frequencies
of
about
20
to
20,000
hertz
(the
upper
range
especially
tends
to
diminish
as

people
get
older).
The
comfortable
hearing
range
varies
in
loudness
from
a
few
decibels
to
about
80
decibels.
At
volumes
near
and
above
160
decibels,
permanent
hearing
damage
is
almost

cer-
tain.
Sudden
loud
sounds,
frequent
exposure
to
loud
sounds,
or
even
long-term
exposure
to
medium
level
sounds
can
damage
the
sensitive
structures
associated
with
hearing.
The
types
of
sounds

most
commonly
used
for
com-
munication
are
speech
and
music.
Most
hearing
is
done
with
the
ears,
although
some
people
augment
their
understanding
of
auditory
information
by
read-
ing
lips

or
sensing
physical
vibrations
through
their
fingers
or
bodies.
Helen
Keller
was
known
for
"lis-
tening"
to
symphonies through a sensitive
sound
board
placed
in
the
symphony
hall
under
her
chair.
Many
deaf

or
hard-of-hearing
people
use
their
fin-
gertips
pressed
against
the
larynx
ofa
speaker
to
aid
in
sensing
auditory
vibrations.
While
humans
can
hear
a
broad
range
of
frequencies,
not
all

these
frequencies
are
used
in
human
speech.
We
can
detect
pitches
up
to
about
18,000
to
20,000
hertz
but
don't
utter
sounds
that
high
in
conversation.
Thus,
telephone
and
other

speech
circuits
typically
are
not
designed
to
transmit
the
full
hearing
range
of
frequencies
and
will
be
optimized
for
the
frequencies
associated
with
the
information
being
transmitted.
See
acoustic.
AudioMsual

Service Specific Convergence Sub-
layer
AVSSCS.
A
multimedia
convergence
protocol
for
transmitting
video
over
AAL5
using
available
bit
rate
(ABR)
services.
There
is
a particular
focus
on
supporting
MPEG
over
ATM
as
ATM
has

become
a
dominant
networking
medium
and
MPEG
is
a
widely
supported
video
format.
ATM
is
capable
of
support-
ing
simultaneous
video
and
other
data
transmissions.
See
asynchronous
transfer
mode,
MPOA.

AudioApplications ProgrammingInterface
AAPI.
A
library
of
functions
designed
to
facilitate
the
de-
sign
of
audio
applications.
The
functions
can
be
called
by
compatible
applications
programs
in
order
to
in-
teract
with

audio
servers.
Thus,
the
conversion,
play-
back,
or
recording of
audio
can
be
accomplished
without
each
aspect
of
the
application
being
written
from
the
ground
up
(Le.,
without reinventing
the
wheel).
Most

operating
systems
now
have
AAPIs
available
for
developers.
Audio Engineering Society
AES.
Since
1948,
the
AES
has
been
promoting
and
fostering
the
develop-
ment
and
advancement
of
audio
technologies.
The
AES
Standards

Committee
contributes
information
79
© 2003 by CRC Press LLC
Fiber
Optics
Illustrated
Dictionary
and
technical expertise that supports national
and
international
audio
standards
development.
The
Au-
dio
Engineering
Society
Historical
Committee
(AES
HC)
researches, collects,
and
preserves historical
in-
formation

and
artifacts related
to
audio
history.
AES
publishes
the
Journal
of
the
Audio Engineering
So-
ciety
and
various
papers
and
conference
proceedings.
/>audio frequency
AF.
A
spectrum
of
wavelengths
that
can
be
heard.

For
humans
this
is
from
about
30
hertz
up
to
about
20
kilohertz,
although
the
upper
level
de-
clines
to
about
16
to
18
kilohertz
by
adulthood.
Audio Interchange File Format
AlFF,
Audio

IFF.
AIFF
is
a
widely
used
audio
file
storage
and
exchange
format descended
from
Interchange File Format
(IFF).
IFF
is
a
flexible,
multiplatform
means
of
digi-
tally
encoding
avariety of
types
ofmedia-related
in-
formation

(not
just
sound).
IFF
was
developed
in
the
mid-1980s
by
Electronic Arts
and
Commodore-
Amiga.
In
1985,
the
format
quickly
became
standard
on
the
Amiga
computer.
Later variations of
the
con-
cept
and

the
file
format
were
ported
to
other
platforms
to provide compatibility
with
Amiga
files.
While
TIFF,
JPEG,
and
BMP
have
now
superseded
IFF
for
the
exchange
of
image
files,
the
Audio
Inter-

change
File
Format concept
has
survived
and
mi-
grated
to
other
platforms
and
has
been
adapted
by
Apple
Computer,
Inc.
as
the
standard
audio
file
for-
mat
for
Macintosh
systems.
AlFF

facilitates
the
data
storage
and
transmission of
monaural
(mono)
and
multichannel
sound
samples
using
a
chunky
format.
On
the
Macintosh,
it
is
stored
in
the
data
fork.
AlFF
is
also
supported

on
a
number
of professional workstations, including
Avid
Tech-
nology
and
Silicon
Graphics
(SGl),
and
has
further
been
adopted
as
a
standard
audio
format
by
the
Open
Media
Format
Interchange
(OMPI)
group.
The

origi-
nal
IFF
format
is
documented
in
the
Amiga
ROM
Kernel manual, Appendix
H.
Details
of
Apple
Computer's
AIFF
are
available
from
Apple
Devel-
operTechrUcalSupport.
Audio Messaging
Interchange
Specification
AMIS.
An
analog
telephony

protocol
that
facilitates
the
exchange
of
voice
mail
messages
among
users
on
voice
mail
systemsfromdifferentvendors.AMIS
specifications
were
released
in
the
early
1990s.
Not
all
the
features
of
commercial
voice
mail

systems
can
be
directed
through
AMIS.
Depending
upon
the
im-
plementation,
AMIS
may
not
permit broadcasting
to
multiple
users
on
another
system,
and
there
may
not
be
a
full
complement
of

confirmation
messages
avail-
able
from
the
other
systems.
A
number
of
commer-
cial
products
implementing
AMIS
systems
or
inter-
facing
with
AMIS
systems
have
been
developed
by
large
vendors
such

as
Toshiba
and
Lucent. Active
Voice
Corporation
claims
to
be
the
first
voice
pro-
cessing
systems
manufacturer
to
incorporate
AMIS
standards
into
its
products.
See
Voice
Profile
for
In-
ternet
Mail.

audio tape A
type
of
magnetic
storage
medium
used
for
audio
recordings.
Most
audio
tapes
are
small,
so
they
can
be
used
in
portable
tape
decks
or
car
stereos,
80
with
playing

times
ranging
from
10
to
120
minutes.
Common
music
tapes
are
30,
45,
or
60
minutes
per
side
for
a double-sided
tape.
Some
audio
tapes
are
designed
as
a continuous
loop
with

the
tape
ends
fused
for
continuous
playing.
Video
tapes
are
some-
times
used
as
high
quality
audio
tapes.
Eight-track
tape
cartridges were introduced
in
the
early
1960s
and
were
popular
for
a

few
years.
Cas-
sette
tapes
were
introduced
soon
after eight-tracks
and
eventually
superseded
them.
By
the
1980s,
video
tape-based
audio
recording approached
CD
sound
quality.
Computers
in
the
late
1970s
and
early

1980s
used
large magnetic
tape
spools
and
small audio tapes
(e.g.,
cassette
tapes)
for
recording
data.
Various
types
of
magnetic
tape
systems
(e.g.,
DAT)
are
still
used
for
data
backups.
As
CD
players become

less
expen-
sive
and
more
prevalent
they
provide higher quality
sound
reproduction
than
most
tape
systems
and
a
less
volatile alternative
to
data
tape
backups.
audio-follow-video AFV
In
many broadcast
sys-
tems,
audio
and
video

are
recorded and/or transmit-
ted
separately.
In
AFV,
the
audio
signals
are
automati-
cally routed together with their associated video
signals
audio-on-demand
AoD.
Audio
services
provided
to
auser
on
request.
AoD
is
one
of
the
earliest services-
on-demand
(SoD)

systems
implemented
in
the
tele-
communications
industry.
In
the
days
of operator-
managed
telephone
services,
imaginative
service
pro-
viders
realized
they
could
place
a
phone
at
the
switch-
board center near a
radio
or

gramophone player
and
play
music
for
the
subscriber
on
request.
It
was
an
unsophisticated
system,
but
the
concept
was
timely,
and
the
idea
is
now
implemented
with
digitally
au-
tomated technologies
in

the
form
of video-on-de-
mand,
and
other custom request services.
See
ser-
vices-on-demand, video-on-demand.
AudioGram DeliveryServices
ADS.
A
Nortel
sub-
scriber telephone service
option
that
enables
callers
who
get
a
busy
signal
or
no
answer
to
their
ring

to
leave
a
message
that
will
be
delivered
to
the
callee
at
a later scheduled
time.
Essentially it's a
phone
line
answering machine
service.
audiographics A multimedia
network
communica-
tions
system
suitable
for
distance learning,
in
which
remote

computer
screens
are
shared
as
a conference
and
lecture
interactive
medium
for
dynamically
shar-
ing
images,
video,
and
text.
Electronic Classroom,
written
by
Robert
Crago
for
the
Macintosh,
is
an
ex-
ample

of
this
type
of application,
designed
to
work
over
public switched telephone
networks
(PSTNs).
Audiographics
is
sometimes
called
telematics.
Some
people
like
to
make
a
distinction
between
audiograph-
ics,
which
is
the
transmission of still images

and
sound,
and
videoconferencing,
the
transmission of
motion
video
and
sound.
With
improvements
in
tech-
nology,
the
distinction
is
blurring.
See
whiteboard-
ing,
electronic; videoconferencing. .
audiometer, sonometer
An
instrument
for
measur-
ing
hearing acuity invented

by
Alexander
Graham
Bell.
Bell's
use
of
the
Audiometer
to
test
hearing
was
© 2003 by CRC Press LLC
reported
in
October
1884
in
the
DeafMute
Journal.
At
the
April
1885
meeting
of
the
National

Academy
of
Sciences,
Bell
is
reported
to
have
demonstrated
his
Audiometer
devised
from
two
flat
coils
of
insulated
wire
adjusted
with
graduated
distances
such
that
elec-
trical cutrent
from
an
armature

between
magnetic
poles
was
passed
through
one
coil
(interrupted
by
a
rotating
disk),
while
a
phone
was
attached
to
the
other
coil.
Thus,
the
current
could
be
used
to
control

the
intensity
of
the
sound,
and
the
responses
of
the
chil-
dren
being
tested
could
be
recorded
and
analyzed.
About
10%
of
the
students
tested
with
this
early
in-
strument

were
found
by
Bell
to
be
hard
of
hearing
in
their
better
ear.
While
the
Audiometer
was
initially
used
to
test
hu-
man
hearing,
many
of
the
components
developed
for

the
audiometric
industry
(speakers,
jacks,
amplifiers,
tone
generators,
transmission
components,
etc.)
have
since
been
adapted
for
telecommunications
devices
and
testing
systems
(P.A.
systems,
telephony
com-
ponents,.
transmission
line
testing
equipment,

etc.).
Audiometers
have
become
very
sophisticated
since
their
invention
by
Bell,
and
the
term
has
become
ge-
neric
to
a
wide
variety
of
audiometric
instruments.
Commercial
audiometers
now
commonly
include

keyboards,
internal
digital
storage
for
saving
hun-
dreds
of
audiograms,
programmable
functions,
and
serial
interfaces
for
connecting
to
computers.
Audion
& Electron
Tube
Controlling
Grid
grid
The triode electron tube (left), developedfrom the
Fleming valve by Lee de Forest,
is
one
of

the most
significant inventions in electronics history. The third
element, a controllinggrid, added by de Forest to the
two-element Fleming valve, enabled the
flow
of
elec-
trons, from the cathode to the anode, to be controlled.
Electron tubes are now more streamlined and so-
phisticated than the original Audion electron tube
which resembled a lightbulb with a plate, filament,
andgrid inside and two wires running out the top.
Audion An
extremely
significant invention of
the
early
1900s,
evolutionarily
descended
from
simple
flame
detectors,
that
led
to
the
three-element
vacuum

electron
tube
patented
by
American
inventor
Lee
de
Forest.
The
Audion
was
a tantalum lamp with a
mostly
evacuated
glass
globe
sealed
around
a
filament
and
plate.
A
simple
wire
bent
in
a
zigzag

pattern
be-
came
a
grid,
providing
control
over
the
flow
of
the
electrons
from
the
filament
to
the
plate
in a
way
that
had
not
been
previously
possible.
Thus,
electron
tubes

could
be
used
to
amplify
signals,
not
just
rectify
them,
as
in
the
Fleming
oscillation
valve
upon
which
de
Forest's
Audion
was
based.
This
triode
electron
tube's
control
grid
represented

breakthrough technology
which
de
Forest
sold
to
AT
&T
at
the
bargain
price
of
$50,000.
It
was
used
for
decades
throughout
the
electronics
industry
until
it
was
superseded
by
the
transistor

for
most
consumer
applications.
Repeater
devices
based
on
the
Audion
enabled
long-distance
telephony.
Interestingly,
like
many
inventions
through
history,
the
inventor
himself didn't
understand
the
detailed
mathematics/physics
behind
why
the
Audion

worked,
creating
problems
in
manufacturing.
The
only
way
to
know
if
the
tube
was
good
was
to
test
it,
and
the
sensitivity
varied
from
tube
to
tube.
Edwin
4rmstrong
was

one
of
the
few
early
scientists
to
grasp
some
of
the
physics
associated
with
the
Audion's
functioning.
He
authored
an
article
in
Electrical
World
in
Decem-
ber
1914,
explaining
the

action
of
the
Audion
and
how
it
could
be
more
effective if
more
gases
were
removed
from
the
bulb
in
manufacturing.
The
term
Audion
was
originally
trademarked
but
has
become
generic

for
three-element
tubes.
See
de
F
or-
est,
Lee;
Edison
effect;
electron
tube;
flame
detec-
tor;
Fleming
oscillation
valve.
Auditory Research
Laboratory
ARL.
A
lab
at
McGill
University
in
Montreal,
Canada

specializing
in
the
study
of
the
perceptual
organization
of
sound.
augerA
tool
designed
for
boring,
or
a
bit
that
fits
into
a
drill
designed
to
make
large
bore
holes,
which

can
be
used
for
wiring
installations.
Augustine, Saint A philosopher
who
authored
De
civitate Dei
(The
city
of
God)
in
428
AD.
This
im-
portant
record
of
western
knowledge
includes
historic
observations
of
magnetic

phenomena.
AUI
See
Attachment
Unit
Interface.
AUP
See
Acceptable
Use
Policy.
aural
Heard
or
perceived
through
the
ear;
auditory.
See
acoustic,
sound.
aurora
Solar
flare,
anuclear effect
from
the
sun
that

can
sometimes
be
seen
by
its
influence
on
the
Earth's
upper
atmosphere.
The
ionization
that
results
causes
the
undulating
light
shows
we
know
as
the
aurora
bo-
realis
and
aurora

australis.
Aurora 1A
regional
communications
satellite
in
geo-
stationary
orbit
over
Alaska.
AUSEAnet
The
Australian-Asian
network
which
supports
multination
VLSI
project
communications
of
the Assocation
of
Southeast Asian Nations
(A
SEAN)
for
sharing
project

information
among
par-
ticipating
countries.
Australian CommunicationsAuthority
ACA.
The
governing
body
of
Australia
responsible
for
regulat-
ing
telecommunications
and
radiocommunications,
including
the
management
of
the
radio
frequency
spectra
and
the
National

Numbering
Plan.
ACA
also
81
© 2003 by CRC Press LLC