Fiber Optics Illustrated Dictionary - Part 88 potx

Fiber
Optics
Illustrated
Dictionary
poles.
The
top
and
bottom
mounting
surfaces
are
metal,
while
the
layers
of"skirts"
down
the
body
of
the
insulator
are
fabricated
out
of
silicone
rubber
over
a

fibre-glass
core.
Silicone
rubber
is
nonconductive,
light,
water-repellant,
resistant
to
ozone
and
ultravio-
let
degradation,
and
easy
to
fabricate
in
a
variety
of
shapes
and
sizes,
making
it
an
alternative

for
glass
and
ceramic
insulators.
SIM4
Historically one
of
the early desktop
computers,
introduced
over
2
years
before
the
Altair,
but
several
months
after
the
Kenbak
-1,
in
1972,
by
the
Intel
Corporation,

which
was
around
the
same
time
Hewlett
Packard
introduced
the
HP
9830.
The
single-board
Intel
computer
was
based
upon
a
4004
processor
and
was
available
in
at
least
two
models,

the
SIM4-01
and
the
SIM4-02.
The
SIM4-02
could
be
inserted into
an
Intel
MCB4
chassis
and
pro-
grammed
through
a
programmer
card.
See
Altair,
Kenbak
-1,
Micra!.
SIMM
single
inline
memory

module.
Simon A
historically
remarkable
computer
project
described
in
Edmund
C.
Berkeley's book Giant
Brains
or
Machines
That
Think
in
1949
and
in
Radio
Electronics
articles
in
the
early
1950s.
The
name
was

based
on
Simple
Simon.
It
was
basically
a
desktop
logic
calculator
that
could
be
built
for
about
$300
(about
$4000
in
today's
money).
In
his
book,
Berke-
ley
describes
it

as
"

so
simple
and
so
small,
in
fact,
that
it
could
be
built
to
fill
up
less
space
than
a
gro-
cery
store
box,
about
4
cubic
feet."

The
Simon
was
an
electromechanical
assembly
for
performing
different
calculating
experiments,
but
it
can
probably
be
considered
the
first
desktop
comput-
ing
kit
considering
the
size
of
computer
behemoths
at

the
time.
Simon
was
a
papertape
computer
based
on
129
relays
and
a
stepping
switch.
In
Berkeley's
description,
a
two-hole
tape
reader
was
used
to
input
numbers
and
operations
and

a
four-hole
tape
reader
was
used
to
input
instructions,
but
Berkeley
points
out
that
relays
and
other
input
modes
apply
just
as
well.
Problems
were
entered
in
binary
and
answers

were
displayed
on
front
panel
lights
(a
design
aspect
used
by
many
early
microcomputers
until
the
mid-
1970s).
With
assistance
from
William
A.
Porter,
Robert
A.
Jensen,
and
Andrew
Vall,

Berkeley
got
a
basic
ma-
chine
working.
Considering
that
most
people
didn't
know
what
a
computer
was
in
those
clays,
it
is
amaz-
ing
that
Berkeley
wrote
about
"machines
that

think"
in
November
1949
and
published
plans
for
actually
building
the
Simon
in
1950.
Apparently
more
than
400
plans
for
the
Simon
were
sold
over
the
next
de-
cade.
Simon's

little-cousin
successor
was
the
GENIAC,
a
computing
"game
machine"
developed
by
Berkeley
in
the
mid-1950s
with
documentation
by
his
partner
Oliver
Garfield
(until
a
dispute
split
the
name
from
the

technology).
See
Altair;
Arkay
CT-650;
Berke-
ley,
Edmund
C.;
GENIAC;
Kenbak-l;
Simplac.
Simplac A
design
for
a transistor-based
computer
presented
as
a collaborative
progress
report
docu-
mented
by
Edmund
C.
Berkeley
through
Berkeley

862
Enterprises
Laboratory
in
1956.
Milt
Stoller
had
re-
sponsibility
for
the
logical
design
of
the
machine.
The
machine
was
intended
to
have
registers
for
three
bi-
nary
digits.
The

author
is
not
sure
whether
this
com-
puter
ever
came
to
fruition.
Berkeley
had
a
lot
of
in-
terests
in
robotics
and
artificial
intelligence
and
was
always beginning new projects. See Simon,
GENIAC.
Simple Discovery Protocol
SDP.

An
experimental
minimal
request/response
multicast
network
recourse
discovery
protocol
developed
by
Martin
Hamilton.
SDP
payloads
are
application-dependent.
SDP
is
not
intended
for
bulk
data
transfers,
due
to
the
size
of

UDP
packets.
Simple File Transfer Protocol
SFTP.
A
simple
file
transfer
protocol
that
fills
the
need
for
a
specifica-
tion
that
is
easier
to
implement
than
File
Transfer
Protocol
(FTP).
It
provides
file

transfer
capabilities
combined
with
user
access
control,
listing
of
direc-
tories,
traversing
directories,
file
renaming,
and
file
deleting.
In
other
words,
it
incorporates
the
most
com-
mon
and
necessary
functions

ofFTP.
See
RFC
913.
Simple Gateway MonitoringProtocol
SGMP.
De-
veloped
in
the
mid-1980s
and
demonstrated
in
1987,
SGMP
later
evolved
into
Simple
Network
Manage-
ment
Protocol
(SNMP).
Simple
Internet
Transition
SIT.
A

set
of Internet
protocol
mechanisms
for
hosts
and
routers
designed
to
smooth
the
transition
between
IPv4
and
IPv6,
its
successor.
SIT
eases
the
transition
by
supporting
in-
cremental
upgrades
of
hosts

through
upgrading
the
DNS
server
with
support
of
existing
addresses.
SIT
employs
a
number
of
mechanisms
to
achieve
inter-
operability
and
compatibility
including:
•
embedding
of
IPv4
addresses
within
IPv6

ad-
dresses
•
encapsulation
of
IPv6
packets
in
IPv4
headers
for
transmission
through
IPv4
legacy
routers
•
dual
IPv4/IPv6
protocol
stacks
model
for
hosts
and
routers
•
header
translation
for

IPv6
only
routing
topolo-
gies
simple line code
SLC.
A
means
of transmission
through
four-level
baseband
signaling
that
filters
the
baseband
and
restores
it
at
the
receiving
end.
Simple Mail TransferProtocol
SMTP.
A
transmis-
sion

subsystem-independent
electronic
mail
protocol
which
establishes
and
negotiates
communications
between
sender
and
receiver
(or
multiple
receivers)
across
transport
service
environments.
Transmissions
may
be
direct,
depending
upon
the
transport
service,
or

may
pass
through
relay
servers.
When
a
user
mail
request
is
generated,
the
sender-
SMTP
establishes
a
two-way
transmission
channel
to
the
intermediate
or
ultimate
destination-SMTP.
SMTP
commands
are
then

sent
between
the
two
ends.
Once
a
transmission
channel
is
established,
a
lock-
step
negotiation
of
the
transmission
and
identifica-
tion
of
the
recipient
or
recipients
is
carried
out,
and

the
mail
data
sent,
with
a
terminating
sequence
to
indicate
the
end.
When
successfully received, the
© 2003 by CRC Press LLC
recipient
sends
an
OK
reply.
See
electronic mail,
email,
RFC
821.
Simple MulticastRouting Protocol
SMRP.
A
rout-
ing

protocol
from
Apple
Computing,
Inc.
which
is
used
for
AppleTalk
network data
from
applications
such
as
their
QuickTime
Conference,
which
in
tum
is
used
for
videoconferencing,
electronic
whiteboard-
ing,
etc.
Simple Network

Management
Protocol
SNMP.
SNMP
evolved
from,
but
is
not
backwardly
compat-
ible
with,
the
Simple
Gateway
Monitoring Protocol
(SGMP).
Essentially,
SNMP
communicates
manage-
ment
information
between
network
management
sta-
tions
and

the
agents
in
the
network elements
(NEs).
SNMP
was
designed
for
TCP/IP-based
network
en-
vironments and manages nodes
on
the Internet.
SNMP
was
originally
designed
as
an
interim
solution
with
the
intention
that
it
follow

generally
along
Open
Systems
Interconnection
(OSI)
guidelines.
Over
time,
they
were
found
more
different
than
originally
envi-
sioned.
Along
with
MIB
and
SMI,
SNMP
has
been
desig-
nated
by
the

lAM
as
a
full
Standard Protocol
with
"recommended"
status.
The
SNMP
Extensions
work-
ing
group
was
formed
to
evaluate
and
further
develop
the
SNMP
definition, with
the
mandate
ofretaining
its
simplicity.
See

RFC
1157.
Simple Raster Grapbics Package
SRGP.
A
low-
level
graphics
package
which
incorporates
features
from
a
variety
ofgraphics
systems
(such
as
GKS
and
PRIGS standards,
The
X
Window
System, Apple
QuickDraw).
SGRP
typically
functions

as
an
inter-
mediate
layer
between
the
applications program
and
the
display
device.
Simple Security
and
Autbentication LayerA
Net-
work
Working
Group-proposed standard
for
provid-
ing
a
quick
method
ofnegotiating
an
authentication
mechanism,
even

if
the
client
has
minimal
knowledge
of
the
system.
See
RFC
2222.
Simple ServerRedundancy Protocol
SSRP.
A
net-
work
protocol
which
provides resiliency
for
LANE
services
onATM-based
local
area
networks
(LANs).
SIMULA object-oriented programming language
designed

by
O.
Dahl
and
K.
Rygaard
at
the
Norwe-
gian
Computing
Centre
between
1962
and
1967.
It
was
intended
for
discrete
event
simulation,
but
gradu-
ally became a general-purpose programming lan-
guage.
SIMULA
was
one

of
the
early
languages
in-
corporating object-oriented
concepts.
A number of
versions
of
SIMULA
have
been
developed over
the
years,
with
compilers
for
specific
systems
such
as
Control
Data
Corporation systems
as
well
as
IBM

360/370
and
UNIVAC
computers.
The
Association ofSIMULA
Users
(ASU),
formally
established
in
1973,
supports
the
development
and
use
of
the
language
and
is
one
of
the
earlier computer
users
groups.
simultaneous voice/data
SVD.

A
number
of
ana-
log
and
digital
techniques
and
standards
which
per-
mit limited use
of
simultaneous voice and data
through
regular
phone
lines
with
computer
voice/data
modems.
These
might
be
considered
medium
level
applications,

since
they
do
not
support
full
realtime
videoconferencing,
but
they
allow
whiteboarding
and
switching between
voice
and
data
as
needed
(alter-
nate voice/data [AVD]).
SVD
is accomplished
through
multiplexing. In analog
SVD,
voice
is
mul-
tiplexed

with
data
in
digital
SVD;
data
and
digitally
compressed
voice
are
multiplexed
into
a
digital
data
stream.
The
ITU
-T
has
established
standards,
draft
standards,
and
specifications related
to
SVD.
These

are
periodi-
cally reviewed
and
updated
to
reflect
improvements
in
modem
technology.
V.61
has
been
specified
for
14,400
bps
standard
for
analog
SVD,
and
V.70
for
28,800/33,600
bps
for
digital
SVD.

simulatorA
software
program,
or
software/hardware
combination
that
models,
reconstructs,
or
mimics
an
environment
or
situation,
which
may
be
real
or
imag-
ined.
Simulators
are
used
in
many
areas
ofscientific
research

to
enact
scenarios;
to
test,
confirm,
or
inves-
tigate hypotheses;
to
compare
or contrast
the
effects
of
various
changes
to
a
system;
or
to
monitor
the
evo-
lution
ofa
system.
Simulators
are

also
popular
in
the
entertainment
industry.
Flight simulators
have
been
developed into interactive, environmental video
games
with
helmets,
moving
seats,
and
more,
to
pro-
vide
a strong emotional/intellectual/tactile experi-
ence.
Virtual
reality simulators
go
a
step
farther,
cre-
ating

3D
effects
which
appear
to
inhabit
the
space
around
the
user,
sometimes
so
convincingly that
the
user
will
duck
to
get
out
of
the
way
ofa virtual
im-
age.
SinclairZX81
The
successor

to
the
ZX80,
the
ZX81
personal
computer
was
introduced
in
spring
1982
and
sold
for
under
$200
(without monitor; it could
be
hooked
up
to
a television
set).
It
sported 8
kbytes
of
~l~~~~~~l~~~:~;~r~iE~:~~~{i~i:;
•

display.
It
was
also
available
as
akit
for
under
$100.
sine waveA
fundamental
waveform
present
in
almost
all
vibratory motion,
which
can
be
represented
as
a
sine curve with periodic oscillations
in
which
the
amplitude
ofdisplacement

at
each
point
in
the
wave
is
proportional
to
the
sine
of
the
phase
angle
of
its
displacement.
In
telecommunications,
the
sine
wave
is
important
in
many
representations, but especially
in
alternating

current
(AC)
circuitry
and
in
represent-
ing
sound.
See
oscilloscope.
sine galvanometerAn
early
current-detecting
instru-
ment
in
which
the
coil
is
rotated until
the
reading
needle
again
registers
zero.
This
type
is

subject
to
interference
from
the
Earth's
magnetic
field.
See
gal-
vanometer.
SINGARS Single Channel Ground
and
Airborne
Radio
Systems.
A
tactical
radio
system.
See
Enhanced
Trivial
FTP.
single line repeaterAmechanism
for
allowing
two-
way
communication

on
a single
line
by
pennitting
the
transmission
to
be
alternately broken
in
one
di-
rection
in
order
to
initiate
or
resume
communication
in
the
other direction.
This
is
accomplished
by
an
ad-

ditional
holding coil
on
each
relay which
can
open
863
© 2003 by CRC Press LLC
Fiber
Optics
Illustrated
Dictionary
or
close
independent
of
whether
the
main
circuit
is
open.
See
half-duplex.
single sideband
Transmissions
created
by
manipu-

lating
frequencies
that
are
selected
from
one
side
of
the
modulation
envelope
ofa
transmission
wave
to
recreate
the
original
baseband
transmission.
Much
of
the
credit
for
the
development
of single sideband
technology,

which
is
essential
to
frequency
division
multiplexing,
belongs
to
John
R.
Carson,
a
mathema-
tician
with
AT&T,
and
later
Bell
Laboratories,
who
mathematically demonstrated
the
relationship
be-
tween
the
information
in

the
sideband
signals
and
the
original
baseband.
Sideband
frequencies
were
not
originally
used
be-
cause
of
problems
with
noise.
Later,
as
technology
improved
and
the
demand
for
airspace
grew,
sideband

transmissions
became
more
interesting,
and
Carson
demonstrated
in
1915
that
one
sideband
could
be
sup-
pressed
from
the
transmission
and
the
other
could
even
be
transmitted
without
the
carrier
wave.

Due
to
its
predictable
characteristics,
the
original
baseband
wave
could
then
be
mathematically
rebuilt
at
the
re-
ceiving
end.
In
a
sense,
this
was
a
type
of
"wave
com-
pression"

accomplished
by
removing
extraneous
and
redundant
information.
The
significant
advantages
included
lower
power
requirements
for
the
transmis-
sion
and
a
narrower
wave
overall
(i.e.,
requiring
less
bandwidth),
leaving
more
room

for
other
transmis-
sions.
See
frequency
division
multiplexing.
single
sign-on
SSO.Anetwork
security
and
manage-
ment
strategy
to
help
reduce
the
number
of
passwords
needed
to
access
a
variety
of
software

and
hardware
resources
on
a
network.
Single
UNIX
Specification
Developed
within
the
Common
Applications
Environment
by
the
X/Open
Company,
the
Single
UNIX
Specification
is
a
collec-
tion
of
documents
which

includes
interface
defini-
tions,
interfaces,
headers,
commands,
utilities,
net-
working
services,
and
X/Open
Curses.
This
specifi-
cation
is
distinct
from
the
AT
&T
licensed
source-code
commercial
product
and
is
intended

as
a
single
stable
UNIX
specification
for
which
portable
applications
can
be
built.
It
provides
vendors
a
means
to
provide
a "branded"
product
and
assumes
voluntary
confor-
mation
to
the
specification.

Basic
components
within
the
Specification
are
shown
in
the
Single
UNIX
Specification
chart.
See
Unix,
UNIX.
single wire circuitA
transmission
path
used
in
early
telegraph
lines
and
still
used
for
telephone
service

in
some
rural
areas.
The
single
wire
circuit
relied
on
the
conductive
characteristics of
the
Earth
to
ground
the
circuit
and
complete
the
return
path.
single-frequency signaling, SF signaling A tele-
phony signaling system
in
which transmission
is
through

a
single
designated
frequency
such
as
2600
Hz
in
the
U.S.
and
2280
Hz
in
the
U.K.
SF
signaling
tends
to
be
used
in
certain
microwave
transmissions
and
in
two-

or
four-line
wired
networks.
SF
signal-
ing
is
an
in-band
signaling
scheme
in
that
the
signal-
ing
is
transmitted
in
the
same
band
or
channel
as
the
data
or
voice

communications.
When
a
phone
system
is
on-hook,
the
designated signaling
frequency
is
transmitted;
when
it
is
off-hook,
the
frequency
is
in-
terrupted. Variations
in
signals
can
be
produced
within
a
single
frequency

by
varying
the
level
of
the
tones
(as
expressed
in
decibels
-
dB).
In
the
U.S.,
a
high
level
of
-8
dB
and
a
low
level
of
-20
dB
are

stan-
dard
as
these
are
levels
that
can
be
readily
recognized
by
the
electronics
in
a
phone
receiver.
single-mode optical fiber A
single
mode
fiber
optic
transmissions
cable
has
a
relatively
thin
core

acting
as
a
waveguide
such
that
light
is
reflected
and
propa-
gated
at
a
consistent
angle.
A
thinner
core
has
advan-
tages
and
disadvantages
over
multimode
fiber.
Sig-
nals
cannot

be
sent
at
a
multiplicity
of
angles
in
the
tiny
fiber
core,
but
distortion
is
minimized
and
trans-
missions
can
reach longer distances.
Thus,
where
multi
mode
fiber
in
data network installations
is
limited

to
about
2
lan,
single-mode
fiber
can
trans-
mit
to
about
15
lan.
For
other
types
of
transmissions,
Single UNIX Specification - Components
Components
Notes
XPG4 System Calls and Libraries
Internationalized, covering POSIX.1 and POSIX.2
callable interfaces, the ISO C library and Multibyte
Support Extension addendum, the Single UNIX
Specification extension including STREAMS, the
Shared Memory calls, application internationalization
interfaces, and other application interfaces.
XPG4 Commands and Utilities V2
Covering the POSIX.2 Shell and Utilities and a large

number
of
additional commands and development
utilities.
XPG4 Internationalized Terminal Interfaces
Including the new extensions to support color and
multibyte characters.
XPG4 C Language
XPG4 Sockets
See sockets.
XPG4 Transport Interfaces (XTI)
864
© 2003 by CRC Press LLC
longer distances are possible, sometimes
up
to
200
lan.
Signals
are
usually
transmitted
through
single-mode
cables
with
laser
diodes,
in
order

to
get
the
precise
alignment
needed
for
the
fine
filaments,
and
received
at
the
other
end
with
a photodiode
detector.
This
de-
tector
translates
the
signals
back
into
electrical
im-
pulses.

Single-mode
fiber
is
divided
into
two
general
catego-
ries:
non-dispersion-shifted
fiber
(NDSF)
and
disper-
sion-shifted fiber (DSF).
DSF,
in turn,
is
subcategorized
as
zero-dispersion-shifted fiber
(ZDSF) and non-zero-dispersion-shifted fiber
(NZDF).
In
DSFs,
the
core-cladding
has
been
fabri-

cated
to
shift
optimal
dispersion
to
higher
frequen-
cies.
There
are
limits
to
how
much
of
this
type
of
com-
pensation
can
be
implemented,
however,
as
shifting
frequencies
may
interfere

with
other
frequency
"win-
dows"
traveling
in
the
same
lightguide,
as
in
multi-
mode
fiber.
NZDF
is
intended
to
overcome
this
type
of
interference
by
shifting
the
zero-dispersion
point
above

the
range
ofwavelengths
that
have
been
opti-
cally
amplified.
See
multimode
optical
fiber.
sink
1.
A
device
to
drain
energy
from
a
system.
Heat
sinks
are
common
on
devices
or

components
which
run
hot
and
need
to
be
cooled
for
safety
and
to
main-
tain
operating
temperatures.
2.
A
point
where
energy
from
a
number
of
sources
is
directed,
and

then
drained
away.
3.
A
point
in
a
communications
system
where
information
is
directed.
sinter
To
cause
to
become
a
coherent
mass
without
melting,
through
the
application of
heat.
1.
In

fiber
optics,
sintering
of
sooty
deposits
such
that
they
form
a clear
substance
is
part of
the
process
of creating
preforms
from
which
optical
fibers
may
be
drawn.
See
boule,
preform,
vapor
deposition.

2.
In
the
con-
struction
of
multilayer
electronic
components,
sinter-
ing
is
part of a direct-write process developed
by
Sandia
researchers
for
precision printing of
ceramic
and
metallic
substrates
with
an
ink-filled
nozzle
rather
than
traditional
screening

or
etching
processes.
The
direct-write
process
enables
a
high
degree
ofpreci-
sion
and
flexibility
in
the
design
of
the
components.
The
electronic
inks
are
heated
at
low
temperatures
to
evaporate

fluids
and
the
remaining
dried
metal
or
ceramic medium
is
fired
to
sinter the powders.
Ink-written
components
have
potential applications
as
conductors,
voltage
transformers,
radio
frequency
filters,
resistor
networks,
and
other
applications.
Sioussat, Helen Johnson (1902-1995)
Sioussat

was
the
Director
of
the
Talks
and
Public
Affairs
Depart-
ment
of
CBS
radio
from
1937
to
1958.
Her
exten-
sive
correspondence
with
many
of
the
radio
and
tele-
vision

broadcast
pioneers
is
historically significant
and
has
been
preserved
in
the
Library
of
American
Broadcasting
at
the
University of
Maryland
Librar-
ies.
See
Broadcast
Pioneers
Library.
SIPP
Simple
Internet Protocol
Plus.
One
of

three
candidate
protocol
proposals
eventually
blended
into
IPv6
by
the
Internet
Engineering
Task
Force
(IETF).
SIR
See
substrate-incident
recording.
SIS Standardiseringen i Sverige. The Swedish
standards
institute
located
in
Stockholm.
SIT
See
Simple
Internet
Transition.

SITA See Societe Internationale
de
Telecom-
munications
Aeronautiques.
site licenseA
legal
arrangement
granting
specific
use
or
distribution permission ofa copyright
product
to
a specified location,
firm,
or
other
entity.
A
site
li-
cense
is
a
common
method
for
specifying

and
con-
trolling
software
use
and
distribution
within
a
firm,
particularly
if
the
firm
wishes
to
install
the
software
on
a
network
for
access
by
multiple
users
or
on
sev-

eral
user
machines
within
the
organization.
Typically,
software
companies
will
offer
site
licenses
with
the
first
copy
and
installation of
the
product
priced
at
one
level,
and
discount
subsequent
installations.
This

is
common
in
educational
institutions.
For
example,
the
first
copy
might
cost
$1000
and
permit installation
on
up
to
five
machines,
with
subsequent
installations,
in
groups
offive,
at
$200
each.
Network

licenses
typi-
cally
specify
how
many
users
may
simultaneously
ac-
cess
the
software,
and
the
software itselfmay
moni-
tor
and
control
access.
Distribution of
any
sort,
other
than
as
specified by
the
license,

in
most
cases
is
a
criminal
offense.
See
piracy.
Skanova A
wholesale
network provider
within
the
relia
Group,
Skanova
operates
the
largest
broadband
network
services
network
in
Sweden.
skin
1.
Outer protective
layer.

A
skin
is
often
used
to
isolate
conductive
materials
and/or
to
provide
insu-
lation
and,
sometimes,
identification
through
the
use
ofcolored
or
marked
skins.
skin antenna
An
antenna
used
on
aircraft,

in
which
a
region
of
the
metal
craft
is
delineated
and
isolated
on
its
edges
by
insulating materials.
skin effect
In
electricity,
asituation
in
which
the
cur-
~?l~:~::r~;~:~~:Eini~~~~~
[_
penetration
to
the

core
of
the
wire.
It
may
increase
the
effective resistance
in
long
wires
and
interfere
with
transmissions
in
the
high
frequencies
used
in
broadcast
transmissions.
skinning
Stripping
an
outer protective
layer.
This

is
commonly
done
with
wires
to
expose
the
conductive
material
within
in
order
to
make
a
connection.
skip distance
The
distance
traveled
by
a reflected
radio
wave
from
the
transmitter
to
the

point
at
which
it
reaches
the
Earth's
surface
or
the
receiving
antenna.
This
distance
is
affected
by
the
frequency
of
the
wave,
the
angle
at
which
it
passes
into
the

ionosphere,
and
various
atmospheric
characteristics
and
conditions.
See
ionospheric
wave,
radio.
skip selection
In
computer
software
applications,
a
selection
that
halts
the
current process,
or
lets
it
fin-
ish
in
the
background,

and
allows
the
user
to
continue
to
the
next
menu
or
activity without
waiting.
In
au-
tomated voice or
tone
systems, especially menu-
driven
touchtone
phones,
a
key
press
that
allows
con-
tinuing
to
the

next
selection,
menu,
or
local
phone
number
without waiting
for
completion
of
the
cur-
rent
message.
skip zone
See
zone
of
silence.
865
© 2003 by CRC Press LLC
Fiber
Optics
Illustrated
Dictionary
SKIPJACK
The
name
ofa

symmetric
encryption
al-
gorithm
which
is
the
basis
of
the
Escrowed
Encryp-
tion Standard
(EES)
incorporated
into
the
Clipper
chip.
SKIPJACK
can
be
used
to
encrypt a
TELNET
stream.
It
has
also

been
described
for
use
in
conjunc-
tion
with
FTP
Security
Extensions
and
Key
Exchange
Algorithm
(KEA)
to
provide
for
mutual
authentica-
tion
and
the
establishment of
data
encryption
keys.
See
Clipper

chip,
RFC
2773,
RFC
2951.
skunkworks
colloq.
Afacility
in
which clandestine
or
time-pressured activities
take
place
in
an
environ-
ment
which
is
closed off
to
increase
security.
Gov-
ernment
operations,
sensitive
research,
and

high-tech-
nology
design
often
operate
in
environments
that
are
without
sunlight
or
adequate
ventilation,
and
in
which
the
participants
are
working long hours (without
much
free
time
for
personal hygiene).
One
of
the
most

famous
skunkworks
was
a
Lockheed-
Martin research "lab" established by Clarence
"Kelly"
Johnson
in
a
small
desert facility scraped
to-
gether
from
salvaged
materials.
It
was
a
tight,
intense,
jet
aircraft
research
and
engineering
operation
dubbed
the

Skonk
Works
after
an
AI
Capp
cartoon
moonshine
operation,
while
its
official
name
became
the Ad-
vanced
Development
Projects
(ADP)
division. Later
the
name
was
changed
to
The
Skunk
Works
and
the

lab
was
moved
to
a
location
northeast of
Los
Ange-
les,
California.
The
term
is
more
than
an
amusing
historical
name;
it
is
also
at
the
heart
of
some
of
the

significant disputes
about
domain
names
on
the
Internet. Lockheed
owns
the
service
mark
for
The
Skunk
Works
and
initiated
lawsuits
in
the
mid-1990s
against
Network
Solutions,
Inc.
for
registering variations of
the
name
on

the
be-
half of
parties
other
than
Lockheed.
It
was
decided
at
the
time
that
a
domain
registrar supplies a service
rather
than
a product
and
that
NSI
was
thus
not
li-
able
for
contributory infringement against

the
mark.
sky maps
Charts
of
the
electromagnetic radiation
in
the
radio
frequencies
emanating
through
space
and
around
Earth.
Much
pioneer
work
in
this
area
was
conducted
in
the
1930s
and
I

940s
by
Grote
Reber,
an
amateur
radio
operator,
using
a
home-built
32-foot
parabolic antenna.
Cosmic
frequencies
can
some-
times
be
detected
when
the
ionosphere
is
temporarily
affected
by
the
burn
ofaspacecraft

or
deliberate
seed-
ing
with
elements
such
as
barium.
The
phrase
is
also
generically
used
to
describe
im-
ages
of
the
sky
as
humans
see
it
looking
up
from
Earth

with
or
without
telescopes.
Some
interesting utilities
on
the
Web
now
enable
users
to
enter a location
and
date/time
to
calculate
and
display a
sky
map
that
can
be
printed
or
downloaded.
John
Walker

provides
ac-
cess
to
"Your
Sky"
free
on
his
Fourrnilab
site.
See
radio
astronomy.
/>sky
wave
See
ionospheric
wave.
SkyBridge A
medium
Earth
orbit
(MEa) satellite
system
from
Alcatel
providing commercial satellite-
based
networking

solutions
to
service
providers.
Sky-
Bridge
was
established
in
1997.
In
March
200
I,
Sky-
Bridge
announced
that
it
would
also
be
implementing
broadband communications services through
866
geostationary satelli
tes.
SkyCell Communications Limited
An
Indian cel-

lular
services provider incorporated
in
1992.
It
is
the
first Indian cellular company
to
receive company-
wide
ISO
900
I certification.
SKYCELL
An
American
Mobile Satellite Corpora-
tion (AMSC) satellite telephony communications
service providing coverage
for
the
North American
continent and nearby islands, catering
to
mobile
workforces, traveling executives,
and
government
agencies.

The
company
also
offers a continent-wide
regional dispatch service providing digital broadcast
capabilities
to
up
to
10,000
mobile
users.
Skynet A U.S. domestic communications satellite
service
purchased
in
1997
from
AT&T
by
LORAL
Space
&Communications,
Ltd.
Skynet
originated
in
the
Echo
satellite

and
Project Telstar efforts
in
the
1960s. Telstar 5 was launched 2 months after
LORAL's acquisition
and
positioned
at
97°
west.
Soon
after,
Satmex
was
merged
into
the
firm,
form-
ing
the
LORAL
Global
Alliance.
Orion
Network
Sys-
tems,
Inc.

was
acquired
in
spring
1998.
Telstar 6
was
lawlched
in
March
1999
at
93°
west;
Telstar
7
was
launched
in
September
1999
at
129°
west.
It
has
been
called
the
most

powerful communications satellite
in
Telstar history
and
has
been
joined
by
further satel-
lites
later
named
Telstar
10
and
12.
Skynet
provides
news,
television broadcasting,
dis-
tance learning, videoconferencing,
and
other data
transmission services
to
about
85%
of
the

populated
regions
of
the
world.
SL
Symbol
for
left-hand slant polarization (lTD).
SL
Mail Acommercial
SMTP
and
POP3
mail
server
daemon
for
Windows
NT
4.0
from
Seattle
Lab,
Inc.
slamming Areprehensible
trade
practice
in
which a

long-distance supplier switches aperson's long-dis-
tance service without
his
or her explicit informed
consent.
In
the
early
1990s,
some
companies
did
this
by
phoning potential subscribers
and
having
them
verifY
their
name
and
address
over
the
phone
and
then
signing
them

up
without actually
asking
for
consent.
Since
that
time,
more
stringent customer consent
is
required before a
change
in
the
service
can
be
initi-
ated,
and
the
customer usually
must
initiate
the
re-
quest,
or
the

company
making
the
change
must
ob-
tain
written authorization
or
outside
verification.
SLAR
See
side-looking airborne
radar.
slave
I.
A subsidiary structure, system, process, or
device
which
takes
direction
or
data
from
a
master.
Many
computer peripherals
are

slave
devices.
2.
In
programming,
slave
processes
are
sometimes
used
to
gather
and
report information
to
amaster controlling
process.
3.
In
communications circuits, slave
con-
soles,
subsidiary switching centers,
and
substations
are
often
used
to
supply

low-density populations
or
workstations
some
distance
from
the
main
control-
ler
or
switching
center.
slave server
In
distributed
networks
using
domain
name
systems,
a
slave
is
an
authoritative
server,
iden-
tified
in

the
name
server's register,
which
retrieves
zones
using
zone
transfer.
See
stealth
server.
sleeve
A covering
to
protect cables,
bars,
and
other
© 2003 by CRC Press LLC
long
narrow
components.
A
sleeve
helps
keep
out
dirt,
air,

and
moisture
and
may
provide
electromagnetic
shielding.
The
term
is
used
for
shorter
lengths
of
pro-
tective
shielding.
A
longer
length,
that
protects
a
span
of
wire
or
fiber
optic

cable,
is
more
often
called
a
jacket. A
sleeve
is
used
for
identification
(e.g.,
color
coding)
or
to
protect
fragile
sections
such
as
areas
where
the
jacket
has
been
opened
(e.g.,

for
splicing
cable).
Sleeves
are
often
made
ofplastic,
though
flexible
metallic
sleeves
may
be
used
to
provide
additional
strength
or
electromagnetic
shielding.
Plastic
sleeves
are
sometimes designed
so
that they will shrink
around
the

covered
component
when
exposed
briefly
to
heat
to
further
ensure
a
tight
seal.
Some
have
a
resin
adhesive
coating
on
the
inside
to
ensure
good
con-
tact.
Transparent
sleeves
can

facilitate
inspection
of
ajoint
after
the
sleeve
has
been
installed.
See
cable,
fusion
sleeve.
slide contactA
small
sliding
ball
or
tab
attached
to
a
thin
rod
that
acts
as
a
contact

mechanism
on
a
tuning
coil.
Tuning
coils
were
used
in
early
radio
sets
to
se-
lect
a
frequency.
A
radio
might
come
with
several
tuning
coils
for
selecting
various
frequencies,

as
de-
sired.
See
tuning
coil.
SLIP
See
Serial
Line
Interface
Protocol.
SLM
1.
See
spatial
light
modulator.
2.
System
Load
Module.
slot
1.
In
programming,
a
time
or
data

"opening"
into
which
other
processes
or
data
can
be
inserted.
2.
A
physical opening for connectors or wires/cables
which
is
typically
narrow
and
rectangular.
The
slots
on
the
back
ofa
computer
allow
external
connection
access

to
peripheral
cards
such
as
serial,
graphics,
or
network
interface
cards
(NICs).
See
slot
types.
3.
In
building
structures,
an
opening
that
may
be
built
into
a
wall
or
floor

in
order
to
enable
cables
to
be
fed
through
the
building.
slot types
Most
computers
and
switching stations
have
slots
into
which
electronics
peripheral
cards
can
be
inserted.
In
order
for
third-party

suppliers
to
be
able
to
develop
options
for
consumers,
a
number
of
standards
have
been
adopted
for
the
shape
and
elec-
trical
configuration
of
these
slots.
Most
of
these
slots

are
long,
narrow-edge
card
configurations,
with
two
to
six
slots
in
the
typical
desktop
computer.
Many
computers
will
accommodate
two
different
card
for-
mats.
The
software
drivers
for
the
cards

inserted
into
these
slots
are
sometimes
supplied
on
diskettes,
to
be
loaded
on
the
system,
and
are
sometimes
supplied
in
hardware,
on
chips
on
the
actual
card.
Some
of
the

more
common
card
slot
types
include
PCI,
ISA,
ESA,
ZORRO,
and
PCMCIA.
SlottedALOHA
See
ALOHA.
slotting
In
setting
up
a
network,
the
assignment
ofa
circuit
to
available
channel
capacity.
slow scantelevision, slow scan

TV
SSTV.
A
type
of
black
and
white
TV
signal
which
can
function
within
a
narrow
spectrum,
similar
to
single-sideband
trans-
missions
for
voice.
SSTV
has
been
used
since
the

late
1950s
by
amateur
television
and
radio
operators
to
send
series
of
images
over
radio
frequencies.
SSTV
can
be
viewed
on
a
television
set
with
a
scan
con-
verter
or

on
a
computer
monitor
with
the
appropriate
interface.
In
the
U.S.,
SSTV
uses
frequencies
ranging
from
about
3.845
to
145.5
MHz
to
transmit
a
series
ofim-
ages
which
can
be

captured
through
a
dedicated
sys-
tem
or
through
a
computer
linkup.
Interface
circuits
for
setting
this
up
are
in
the
hobbyist
price
range.
Hicolor mode can provide color images
up
to
320
x
240
in

thousands
of
colors.
Even
higher
reso-
lution
640
x
480
24-bit
images
(millions
of
colors)
can
be
transmitted,
but
they
take
7
or
8
minutes,
com-
pared
to
low-resolution
black

and
white
images
that
take
only
7
or
8
seconds.
Radio
broadcasting
is
regulated
throughout
the
world;
those
interested
in
SSTV
technology
will
have
to
be
licensed,
usually
for
voice

grade
channels,
by
local
regulatory
authorities.
A
related
techno
logy
is
amateur
TV
(ATV)
which
re-
fers
to
fast
scan
amateur
television.
See
amateur
tele-
vision.
SLP
See
Service
Location

Protocol.
SLR
1.
send
loudness
rating.
2.
single
lens
reflex.
Sm
symb.
samarium.
See
samarium.
Small
Computer
System
Interface
SCSI
(pron.
sCllZzi).
A
standardized
interface
specification
which
provides a
means
for

the
central processing unit
(CPU)
and
main
circuitry
on
the
motherboard
to
com-
municate
with
computer
devices
that
are
interfaced
to
the
system.
This
requires
standardization
of
elec-
trical
circuitry
and
data

protocols
because
peripheral
devices
are
manufactured
by
many
different
compa-
nies.
One
of
the
most
common
of
these
formats
is
SCSI,
which
is
widely used
to
interconnect
hard
drives,
scanners, cartridge drives, digitizers,
CD-

ROM
drives,
and
more.
The
SCSI
standard
is
approved
by
the
American
Na-
tional
Standards
Institute
(ANSI),
and
several
en-
hanced versions
have
appeared (variously called
SCSI-2,
extended
SCSI,
SCSI-3,
wide-SCSI,
etc.)
SCSI

typically consists of a
SCSI
controller
on
a
motherboard
or
a
peripheral
card,
which
is
terminated
and
usually
designated
as
zero
or
six,
depending
upon
the
system
and
one
or
more
peripheral
devices,

set
to
SCSI
ill
number
zero
through
five
or
one
through
six,
depending
upon
which
one
is
reserved
for
the
motherboard,
and
terminated
at
the
end
of
the
last
device.

The
devices
can
be
hooked
up
end-to-end,
that
is,
daisy-chained.
Each
SCSI
controller
can
chain
up
to
seven
devices,
with
the
motherboard
or
main
con-
troller
counting
as
one.
The

cable
for
SCSI
devices
is
either
a
50-pin
edge
connector
or
a
25-pin
D
con-
nector
(or
a
hybrid
cable
with
an
edge
connector
at
one
end
and
pin
connector

at
the
other).
SCSI-3
cables
are
wider.
Only
one
device
can
be
assigned
to
each
SCSI
ill.
Conflicts
or
lack
of
termination
will
cause
failure
to
recognize
a
device
or

spurious
errors.
Many
systems
expect
CD-ROM
devices
to
be
set
to
ill
3,
although
there
is
no
inherent
reason
why
ill
3
has
to
be
assigned
to
only
this
type

of
device.
Scanners
often
default
to
SCSI
ill
4.
The
ill
number
will
determine
the
priority
867
© 2003 by CRC Press LLC
Fiber
Optics
Illustrated
Dictionary
setting
for
loading
the
device,
thus
boot
disks

are
usu-
ally
assigned
a
number
closest
to
the
number
of
the
controller.
In
other words,
if
the
controller
on
a
motherboard
is
zero,
then
the
boot
hard
drive
should
probably

be
set
to
one
and
a
relatively
low-use
tape
drive
to
five
or
six.
SCSI
ill
settings
are
sometimes
on
the
outside
of
the
device,
with
a
thumb-turn
switch
or

DIP
switch,
and
sometimes
on
the inside, with
DIP
switches or
jumpers.
Termination
is
accomplished either
by
placing a
physical
terminator
in
one
of
the
cable
connection
slots,
by
setting
DIP
switches,
or
by
setting

jumpers
inside
the
device.
Automatic
termination
is
available
on
some
devices,
which
means
that
if
the
device
senses
that
it
is
the
last
device
in
the
chain,
it
will
ter-

minate
automatically.
These
types
of
automatic
ter-
minators
are
sometimes
specific
to
the
slot.
There
will
be
two
slots
on
the
back
of
most
SCSI
devices
so
that
they
can

be
chained.
Take
care
to
follow
instructions
for
which
one
to
connect
if
the
device
is
last
in
the
chain
and
intended
to
terminate
automatically.
Most
SCSI
devices
can
only

work
with
cables
up
to
about
6
feet
in
length,
and
3
feet
or
shorter
is
gener-
ally
recommended.
Newer
Fibre
Channel
Standard
technologies
can
support
longer
connection
lengths,
allowing

SCSI
devices
to
be
centralized
in
an
opera-
tions
room
or
wiring
closet.
SCSI
controllers
are
standard
in
many
consumer
and
workstation
computer
systems,
including
Macintosh,
Amiga,
server-level
ffiM-licensed
desktop

comput-
ers,
NeXT,
Sun,
SGI,
some
HP
systems,
and
DEC.
Most
of
these
systems
include
an
internal
SCSI
con-
troller
(for
up
to
six
hard
drives
and
internal
CD-ROM
drives,

etc.)
and
an
external
SCSI
controller
(for
up
to
six
scanner,
printer,
external
CD-ROM,
external
hard
drive
devices,
etc.).
Thus,
a
total
of
12
devices
can
easily
be
daisy-chained
to

these
systems
without
any
modifications
to
the
operating
system
or
the
hard-
ware,
other
than
perhaps
adding
a
software
device
driver
and
cabling.
In
the
author's
experience,
SCSI
is
a good format. The inexpensive 8-year-old

Motorola
68040-based
computer
used
for
the
illus-
trations
for
this
dictionary
has
two
SCSI
connectors
(internal
and
external)
with
eight
SCSI/SCSI-2
de-
vices
attached
(scanner,
tape
drive,
cartridge
drive,
six-disc

CD-ROM
drive,
and
four
different
kinds
of
hard
drives).
These
are
chained
to
the
two
control-
lers
and
worked
together
the
first
time
they
were
con-
nected
without
any
compatibility

problems.
SCSI
drives
are
incorporated
in
mirroring
and
redun-
dancy
combination
drive/backup
systems
such
as
re-
dundant
array
ojinexpensive
disks
(RAID)
systems.
These
drives
can
be
conveniently
hot-swapped
in
and

out
ifa
drive
fails
and
needs
to
be
replaced,
with
the
information
rebuilt
by
the
controller
and
software
when
the
new
drive
is
installed.
For
consumer
desktop
Intel-based, IBM-licensed
computers
that

come
standard
with
IDE
drives,
a
SCSI
controller
card
can
be
added
to
the
system
to
accommodate
SCSI
devices.
However,
on
this
type
of
system,
it
is
important
to
detennine

whether
appro-
868
priate
device
drivers
are
available
for
the
peripheral,
that
there
is
no
contention
with
the
IDE
drive,
and
also
that
any
appropriate
IRQ
issues
are
settled.
Small Scale Experimental Machine Nicknamed

"Baby,"
this
historic
computer
was
developed
in
the
mid-1940s,
based
upon
tube
memory,
a
form
of
ran-
domly
accessible
data
stored
in
a
Williams-Kilburn
cathode-ray
tube.
Baby
was
a
binary

small-endian
system
that
supported
32-bit
words
and
a
main
ran-
dom
access
storage capability of
32
words,
which
could
be
extended
to
8192
words.
It
used
several
tubes
for
different
functions,
including

a
storage
reg-
ister
that
is
still
used
in
modern
computers,
the
"ac-
cumulator,"
a
couple
of
instruction
tubes,
and
a
tube
for
displaying
the
contents
of
the
other
tubes.

A
simple
keyboard
was
used
to
set
the
bit
sequences.
The
project
was
undertaken
by
T.
Kilburn
and
G.
To
o
til
1
with
equipment
support
from
the
Telecommu-
nications

Research
Establishment
(TRE).
The
system
was
initially
used
in
1948
for
mathematical
calcula-
tions
that
were
laborious
to
execute
by
hand.
See
Williams-Kilburn
tube,
Manchester
Mark
1.
small vocabulary In
speech
recognition,

it
has
been
found
that
software
can
be
designed
to
recognize
a
variety
of
voices,
without
special
training
of
the
sys-
tem,
if
the
total
vocabulary
of
the
recognition
is

kept
small.
These
small
vocabulary
systems
work
well
in
specific
environments
such
as
stock
buy/sell
systems.
While
definitions
of
small
vary,
recent
systems
of
this
type
typically
recognize
200
or

fewer
words.
Smallhouse, Charles "Chuck" An
amateur
radio
enthusiast (callsign
WA6MGZ
[now
W7CS])
who
contributed
substantially
to
the
first
three
OSCAR
sat-
ellites'
design
and
construction.
See
OSCAR.
Smalltalk
An
object-oriented
computer
exploration
and

development
language
developed
through
the
Xerox
Corporation
in
the
1970s.
It
was
evaluated
by
four
Xerox-selected
companies
in
1980,
before
be-
ing
broadly
distributed.
By
the
mid-1980s,
commer-
cial
versions

of
Smalltalk-80
were
being
released
for
a
variety
of
platforms
including
mM
licensed
per-
sonal
computers
and
Apple
II
systems.
Smalltalk
has
been
favored
by
developers
working
in
object-ori-
ented

programming
environments
and
artificial
intel-
ligence
applications.
See
Palo
Alto
Research
Center.
SMAP
See
Service
Management
Access
Point.
SMART
Self-Monitoring,
Analysis,
and
Reporting
Technology.
A preventive
system
implemented
in
data
protection

schemes
such
as
RAID
which
uses
predictive
failure
analysis
to
anticipate
possible
fail-
ures.
Impending
problems
are
communicated
to
the
controller,
which
signals a
warning
so
that
faulty
drives
may
be

examined
or
replaced
prior
to
any
fail-
ure
which
might
occur.
See
redundant
array
of
in
ex-
pensive
disks.
Smart
Card
A
compact,
thin
card
with
embedded
data.
It
may

contain
a
microprocessor,
memory,
or
both.
It
typically
resembles
a
plastic
credit
card.
Ear-
lier
Smart
Cards
incorporated
a
magnetic
strip,
but
more
recent
cards
may
include
a
set
of

contacts
em-
bedded
in
the
card.
There
are
various
ways
to
categorize
Smart
Cards.
© 2003 by CRC Press LLC
Some
require
contact
with
a
sensor
and
some
are
read
without
direct
physical
contact.
A

contact
sensor
can
consist
of a
reader
with
a
slot
or
a
sensing
surface
upon
which
the
card
is
placed.
Slot
sensors
generally
require
that
the
card
be
swiped
across
the

surface
to
register
the
information.
Basically
the
card
is
being
scanned
for
information.
Contactless
cards
typically
incorporate
tiny
wireless transmitters
and
may
in-
clude
an
antenna
to
increase
the
transmission
range

of
the
signal.
There
are
also
hybrid
cards.
For
ex-
ample,
a
wireless
transmitter
may
be
included
for
opening
entranceways
at
a
worksite
while
a
second
contact
surface
may
be

used
to
transmit
more
detailed
information
about
the
person
holding
the
card
when
it
is
swiped
through
a
card
reader.
The
common
standard
for
Smart
Cards
is
in
the
ISO

7816
series.
A
number
of
financial
agencies
have
agreed
upon
a
common
specification
for
communi-
cations
between
Smart
Cards
and
Smart
Card
read-
ers,
similar
to
the
serial
communication
that

occurs
between.
computers
and
computer
peripherals.
This
makes
it
possible
to
exchange
virtually
any
type
of
data
between
readers
and
cards
and
increases
the
pos-
sibility
of
programmable
universal
cards

for
the
con-
venience
of
users.
The
downside
of
universal
cards
is
that,
if
they
are
stolen,
a
great
deal
of
information
may
be
in
the
wrong
hands.
However,
various

encryp-
tion
and
other
security
measures
are
being
developed
to
help
protect
Smart
Card
users
against
theft.
The
cards
can
also
be
categorized
on
the
basis
of
the
types
of

data
contained
on
the
card
(information
or
algorithms)
and
whether
they
are
reprogrammable
(write
once,
read
many
(WORM)
or rewritable).
Since
a
Smart
Card
is
somewhat
like
a
tiny
floppy
disk

or
a
very
tiny
computer,
the
range
of
uses
to
which
it
can
be
applied
is
exceptionally
broad.
It
could
not
only
facilitate
telephone
access
for
travel-
ers,
but
could

potentially
keep
track
of
where
and
when
the
calls
were
made.
This
information
is
valu-
able
for
corporations
logging
sales
transactions,
for
example,
and
keeping
records
for
the
taxation
depart-

ment.
A
Smart
Card
could
also
help
present
and
track
prescriptions,
employee
purchases,
medical
histories,
allergy
shots,
pet
vaccination
histories,
automobile
histories,
and
much
more.
Smart
Card
application
interfaces
have

been
introduced
by
a
number
of
de-
velopers
and
a
lot
of
interest
in
programming
Smart
Cards
with
Sun's
Java
language
arose
in
the
late
1990s.
It
is
likely
that

Smart
Cards
will
become
a
ubiquitous
part
of
daily
life,
replacing
many
of
the
paper
notepads
and
"dumb"
cards
now
used
by
con-
sumers
and
professionals.
Smart
Card
history
The

essential concept of
the
Smart
Card
was
patented
in
1974
by
K.
Arimura
in
Japan
and
R.
Moreno
in
Europe.
In
the
1980s
and
1990s,
Smart
Cards
came
into
common
use
for

many
types
of
financial
transactions,
mobile
communica-
tions
devices,
long-distance
phone
services,
and
au-
thorized
entry
systems.
Smart Card Industry Association
SCIA.
A
trade
association
supporting
and
promoting
the
develop-
ment,
utilization,
and

understanding
of
Smart
Card
technologies.
/>SMASH Project A
project
dedicated
to
developing
mass
storage
devices
for
multimedia
applications
for
home
use.
This
is
intended
to
promote
commercial
offerings
of
video
services
to

the
home,
with
part
of
the
goal
of
SMASH
to
provide
a
labeling
algorithm
system
in
the
storage
system
to
provide
vendor
copy
protection.
Thus,
data
on
the
storage
device

can
be
set
so
that
it
can
only
be
stored
or
copied
once.
SMASH
seeks
to
develop
realtime
labeling
methods
for
compressed
video.
Common
schemes
for
this
in-
clude
spatial

or
discrete
cosine
transform
(DCT).
The
SMASH
Project
also
introduces
two
new
realtime
labeling
techniques
that
can
be
used
in
conjunction
with
MPEG-l
or
MPEG-2
format
video
information.
See
watermark.

SMAS Switched Maintenance Access
System.
A
legacy
telephony
network
system
from
Anritsu
Com-
pany.
The
older
systems
(e.g.,
cross
bar
access
sys-
terns)
are
gradually
being
updated
or
phased
out.
SMATV Satellite
Master
Antenna

Television.
A
sat-
ellite
communications
distribution
system
designed
to
send
transmissions
to
hotels,
motels,
apartments,
etc.
Since
these
are
sent
mainly
to
commercial
estab-
lishments,
they
are
often
used
as

marketing
leaders
or
as
pay-per-view
revenue-generators.
5MB
See
Server
Message
Block
protocol.
5MB
ProjectA
project
for
preserving
the
history
of
the
Server
Message
Block
(SMB)
protocol
while
pri-
mary
materials

are
still
available.
The
first
definition
ofNetBlOS
was
released
by
ffiM
in
a
Technical
Ref-
erence
in
1984.
By
the
late
1980s,
5MB
File
Sharing
Protocol
extensions
were
being
published

by
Micro-
soft.
/>SMDS
See
Switched
Multi-Megabit
Digital
Service.
~~~t~~f:~ri~::::::
:e:::~i:~
::~~
::~
II
play
distortion
in
which
the
image
is
blurred
and
ap-
pears
stretched
in
the
horizontal
direction.

2.
Low-
level
frequency
distortion
in
an
audio
signal.
3.
In
digital
imagery,
distortion
of
details
resulting
from
sampling
frequencies
or
compression
algorithm
com-
promises,
so
transitions
which
normally
would

be
sharp
and
crisp
in
the
original
image
exhibit
blurring
or
smear.
smectic liquid crystal
SLC.
The
molecules
of
nem-
atic
liquid
crystals
have
a
certain
amount
of
orienta-
tion
order
but

generally
lack
position
order.
At
cer-
tain
transitional
temperatures,
these
materials
may
acquire
a
certain
amount
ofpositional
order,
called
the
smective
phase.
Thus,
the
material
has
some
of
the
properties

of
liquids,
but
tends
to
form
somewhat
positional
layers,
resulting
in
a
two-dimensional
nem-
atic
liquid
crystal.
Depending
upon
the
tilt
and
light-
directing
properties
of
the
smectic
liquid
crystals,

they
may
be
subdivided
into
different
types.
If
the
SLCs
are
encouraged
to
form
a
chiral
orienta-
tion
resulting
in
a
helical
orientation
(as
in
the
Schadt
Helrich
effect)
they

can
be
selectively
used
to
modu-
late
light
to
tum
it
on
or
off.
This
form
ofliquid
crystal
has
faster
response
time
869
© 2003 by CRC Press LLC
Fiber
Optics
Illustrated
Dictionary
and
better

contrast
ratio
than
nematic
crystal
displays.
See
nematic liquid crystal, Schadt-Helfrich effect.
SIMIME
Secure
Multipurpose Internet Mail Exten-
sion.
An
IETF
working group (inherited
from
the
Sf
MIME
Consortium) Internet messaging standard
for
the
transmission ofsecure network communications.
Unlike
PGPIMIME,
SIMIME
public
keys
are
distrib-

uted via
X.509
digital certificates.
SIMIME
can
sup-
port
12S-bit
encryption, although
not
all
implemen-
tations will
use
the
fulll2S bits.
See
PGPIMIME.
SMPTE
See
Society ofMotion Picture
and
Televi-
sion
Engineers.
SMPTE Registration Authority
SMPTE
RA.
A
for-

mat
and
specification authority
for
technologies
re-
lated
to
the
motion picture
and
television industries.
For
example,
the
SMPTE
RA
is
approved
by
IEC
and
ISO
for
the
registration ofMPEG-related
format
iden-
tifiers.
See

Society ofMotion Picture
and
Television
Engineers.
SMPTE time code Astandard developed
by
the
So-
ciety
of
Motion Picture
and
Television Engineers
which provides synchronization
for
information
re-
corded
on
audio
and
visual video
tapes.
SMPTE
time
code digitally encodes hours, minutes, seconds,
and
frames.
SMPTE
time

code
is
recorded
onto
audio tracks
and
video
tracks
as
follows:
in
audio
as
Longitudinal
time
code
(LTC);
in
video
as
Vertical
interleave
time
code
(VITC).
A
time
code
word
consists of

SO
bits
(zero
or
one)
per video
frame,
with 2400 bits per second corre-
sponding
to
30
frames
per second
for
North Ameri-
can
TV.
In
Europe,
2000
bits
per second corresponds
to
the standard of
25
frames
per second.
See
drop
frame,

Society ofMotion Picture
and
Television
En-
gineers.
SMR
See
Specialized Mobile
Radio.
SMRP
See
Simple Multicast Routing Protocol.
SMS
I.
See
Service Management System.
2.
See
Short Message Service.
SMS/800 Acentralized interactive computer system
dedicated
to
coordinating network services related
to
toll-free
SOO/S76/etc.
numbers. These
are
managed
in

a central database-equipped mainframe computer
from
IBM
that updates locally deployed databases.
Access
is
through
dialup,
Internet,
and
dedicated
con-
nections
with
various security systems
in
place
to
re-
strict
access
to
authorized users.
The
SMS/SOO
sys-
tem
supports a 24-hour-a-day, 7-day-a-week public
service.
Within

the
SMS/SOO
system, a Responsible Organi-
zation
(Resp
Org)
is
an
entity authorized
to
manage
and
administer atoll-free number customer using
the
SMS/SOO
system.
Bell
Operating
Companies
(BOCs)
administer
the
SMS/SOO
system under
the
SOO
Ser-
vice
Management System Functions
Tariff.

The
SMSfSOO
system
tracks
the
availability of
all
toll-
free
numbers
and
permits
Resp
Orgs
to
access
the
database
to
search for available numbers
and
to
change
the
status of existing numbers. The North
American Numbering Plan
(NANP)
Administrator
issues instructions
to

carriers
for
making toll-free
870
numbers available or unavailable.
Resp
Orgs
are
as-
signed a
logon
ID
code
from
a
BOC
and
must
meet
certain certification requirements. Logon
ill
requests
are
processed
by
the
SMSfSOO
Management
Team
in

New
Jersey.
Numbers
are
obtained
by
Resp
Orgs
from
acommon
pool, with specific
SOO
number requests honored
based
upon
availability
on
a first-come, first-served
basis at
the
time
the
request
is
received
in
the
SMSI
SOO
Reservation

Queue.
Specific numbers may
be
reserved
for
a potential subscriber
for
up
to
45
cal-
endar
days.
If
the period expires,
the
number
is
des-
ignated a spare. A
Resp
Org
may
reserve
up
to
2000
numbers,
or
up

to
7.5%
of
the
total available num-
bers,
whichever
is
greater. Certain numbers
are
re-
served
for
special purposes (e.g., hearing impaired)
and
are
considered Closed.
Resp
Orgs
are
limited
to
a maximum
of
up
to
3%
of available numbers that
are
reserved

at
any
given
time.
Resp
Orgs
must
be
willing
and
able
to
provide troubleshooting assistance
and maintenance personnel. There
is
a customer
record administration charge
for
each toll-free num-
ber assigned
or
reserved.
Hoarding
of
toll-free numbers
by
Resp
Orgs
is
ex-

pressly
forbidden
within
the
Federal Communications
Commission
(FCC)
Tariffguidelines.
Acquiring
more
numbers
than
are intended
for
immediate
use
by
a
subscriber,
or
the
sale
of
a toll-free number
for
an
additional
fee,
contravenes
the

FCC's responsibility
to
promote
the
fair allocation
and
orderly
use
of
toll-
free
numbers.
The
SMSfSOO
Software Support organization pub-
lishes the
Service Management System (SMS)/800
Mechanized Generic Interface Specification
(SR-
4592
-
Feb.
200
I).
See
SOO.

SMS/800 history
The
SMS/SOO

system originated
in
1967,
when
AT&T
introduced
an
inward
Wide
Area
Telecommunications Service
(INWATS)
for
business
subscribers who wanted
to
purchase bulk calling
to
enable customers
to
reach them
from
a wide geo-
graphic region.
In
19SI, computerization made
it
practical
to
introduce acentralized database

for
man-
aging national services
such
as
SOO
numbers
and
to
assign parameters
to
specific numbers. This,
in
turn,
made
it
possible
to
make
the
service
more
flexible
and
powerful.
At
about
the
same time, smaller com-
panies

and
competing phone carriers
were
comput-
erizing their customer databases.
When
the
Judge Greene divestiture proceedings
led
to
the
breakup
of
the
Bell
System
in
1984,
SOO
ser-
vices
were
required
to
be
opened
up
to
competitors.
This necessitated

the
development
of
more
sophisti-
cated software
to
handle
the
management
of
data-
bases
from
Bell Operating Companies
(BOCs)
and
independent competing carriers.
Number portability
soon
became
an
issue,
with
so
many competing phone carriers
now
offering
SOO
services.

In
1991,
the
Federal Communications
Com-
mission (FCC) mandated that
SOO
numbers must
be
able
to
be
moved among carriers according
to
the
carrier selection of
the
subscriber.
By
the
mid-1990s,
SOO-number
designations were
© 2003 by CRC Press LLC
running
out,
due
to
the
increasing

demand.
As
a
re-
sult,
additional
prefixes
were
released,
to
be
assigned
as
the
need
arose.
See
SMS/800.
SMS/SOO
Management TeamA
team
of
administra-
tors,
consisting
ofa
representative
from
each
of

the
regional
Bell
Operating
Companies
(RBOCs),
re-
sponsible
for
SMS/800
services.
The
team
is
head-
quartered
in
New
Jersey.
SMS/SOO
Mechanized Generic Interface
MGI.
A
means
to
interface
with
the
SMS/SOO
centralized

to11-
free
number
database.
The
MGI
facilitates
the
trans-
fer
of
number
and
customer
record
administration
between
the
SMS/800
and
Responsible
Organization
(Resp
Org)
computer
system
over
a
network
connec-

tion.
It
is
a
two-way
interface
delivered
over
a
five-
layer
protocol
model.
The
transport
service
is
sup-
ported
over
the
physical,
packet,
and
link
layers
for
error-free
communication.
The

user
program
layer
(UPL)
supports
specific
applications
messages.
Before active status
on
the SMS/800 system
is
granted,
the
MGI
must
be
put
through
four
test
phases
to
confirm
data
communications
integrity
per
spe-
cific

field
and
laboratory
testing
requirements.
A
test-
ing
logon
ill
is
assigned
for
the
test
period
of
about
4
months.
Once
access
is
authorized,
an
active
login
ill
code
is

assigned.
See
SMS/800.
SMTP
See
Simple
Mail
Transfer
Protocol.
Sn
Symbol
for
tin
(AN
50).
SNA
See
Systems
Network
Architecture.
SNA Control Protocol
SNACP.
A
protocol
which
handles
the
configuration
and
enable/disable

func-
tions
at
the
ends
ofapoint-to-point
link.
Subdivided
into
two
protocols
that
independently
negotiate
SNA
with
or
without
LLC
802.2.
Similar
to
Link
Control
Protocol.
See
See
RFC
2043.
SNACP

See
SNA
Control
Protocol.
snakeA
cabling
aid
consisting
ofa
flexible,
long,
thin
cord
of
metal
or
plastic
used
to
feed
wire
and
cable
through
conduit
or
through
structures
(ceilings,
walls,

attics,
etc.)
where
space
is
tight,
or
access
is
limited.
See
birdie.
SNAP
See
SubNetwork
Access
Protocol.
snap-hookA
loop-shaped
connector
with
a
normally
closed
hook
that
can
be
opened
to

add
objects
to
the
hook
with
the
hook
snapping
closed
automatically
after
insertion.
Snap
hooks
may
be
locking
or
non-
locking.
Rock
climbers
are
familiar
with
a
number
of
types

of
snap
hooks
and
similar
hooks
are
used
by
workers
who
climb
utility
poles
or
towers
to
do
in-
stallations
or
maintenance/repair.
Snap
hooks
are
also
handy
for
slinging wire bundles
and

hanging
up
equipment
that
needs
to
be
securely
held.
Contrast
with Jhook.
sneakcurrents
Low-level
undesired
currents
which
seep
into
circuits
and
may,
if
continued
long
enough,
cause
damage.
Sneak
currents
are

those
which
do
not
cause
immediate
harm
and
are
not
sufficient
to
trig-
ger safety
mechanisms
such
as
normal
fuses
and
breakers.
Sneak
currents
can
result
from
causes
such
as
worn

sheaths
and
insulators,
incorrect
wiring,
tem-
porary
contact
due
to
settling,
etc.
See
sneak
fuse.
sneakfuse A
special
low-level
current
detection
fuse
specifically
designed
to
trigger
if
sneak
currents
are
detected.

See
sneak
currents.
Snell, Willebrord
(1580-1626)
A
mathematician
and
astronomer
from
the
Netherlands,
who
succeeded
his
father
as
a
mathematics
professor
at
the
university
of
Leiden.
Snell
established a variety of
methods
for
measuring

the
Earth,
establishing
some
of
the
basic
tools
of
geodesy.
He
further
refined
basic
principles
of
light
and
predicted
how
light
rays
would
act
in
an
environment
such
as
a

glass
rod.
In
1703,
C.
Huygens
published
Dioptrica
in
which
he
refers
to
Snell's observations
about
refraction
made
in
1621.
For
a
time,
R.
Descartes
was
thought
to
be
the
originator of

the
mathematics
of
refraction,
but
it
appears
he
got
his
information
from
Snell.
The
explanation of
the
phenomenon
came
to
be
called
Snell's
law.
Snell's
observations
were
important
be-
cause
refractive

behavior
is
nonlinear
and
thus
not
easy
to
measure
or
mathematically
describe
unless
the
relationships
are
understood.
See
refraction,
Snell's
law.
Snell's lawA
description
of
the
relationship
between
the
angle
of

incidence
and
the
angle
of
refraction
in
propagating
radiant
energy
when
it
encounters
a
ma-
terial
of
differing
density.
This
relationship
was
ver-
bally
described
by
Willebrord
Snell
in
1621.

In
1658,
Fermat
showed
how
Snell's
law
was
generalizable
to
any
propagating
radiant
energy
traveling
through
any
medium.
See
absolute
refractive
index;
Brewster's
angle;
refraction;
Snell,
Willebrord.
Snell's
Law
ofRefraction

Snelldescribed
how
propagatingradiantenergy
(I)
refracts when it encounters a medium
of
higher den-
sity
(R).
The energy is benttoward the surface normal
of
the medium such that the angle
of
incidence (a)
andtheangle
of
refraction
(13)
remain in constantpro-
portion to one another in terms
of
the sines
of
the
angles.
SNI
See
Subscriber
Network
Interface.

sniffer
1.
colloq.
nose.
2.
A
synthetic
or
electronic
substitute
for
a
nose,
such
as
a
chemical
testing
kit
used
for
drug
detection
and
identification
by
the
U.S.
Customs
service.

3.
Autility
for
peeling
or
ferreting
out
information,
such
as
particular statistics
from
a
log
file.
4.
A
network
traffic
monitoring
tool
used
for
diagnostics
and
sometimes
unauthorized
snooping.
871
© 2003 by CRC Press LLC