Specifications

MultiModem ISI Hybrid Series, ISIHI-2S/2U 181
Glossary
manipulate the data. Before a PC can do anything useful, it
must move programs from disk to RAM. When you turn it
off, all information in RAM is lost.
rebootRestarting your PC by turning off the power and
then turning it back on, or by pressing Alt, Ctrl,, and Del
keys at the same time. Warm boot=Ctrl+Alt+Del (soft boot)
or Cold boot=Power switch (hard boot).
repeaterA device that amplifies or regenerates the data
signal in order to extend the distance of the transmission.
This can be used with both analog and digital signals and is
used extensively in long distance transmission to keep
signals from losing their strength.
resolutionIndicates the number of dots that make up an
image on a screen or printer. The more dots, the higher the
resolution, and the finer and smoother the images can
appear when displayed at a given size.
RJ-11An industry standard interface used for connecting a
telephone to a modular wall outlet; comes in 4- and 6-wire
packages.
RJ-45An 8-wire modular connector for voice and data
circuits.
ROM (read only memory)A memory chip that permanently
stores instructions and data. Its contents are created at the
time it is manufactured and cannot be altered. ROM is used
to store control routines in PCs and peripheral controllers.
It is also used in plug-in cartridges for printers and video
games. A set of ROM chips contains the basic input/output
system (BIOS).
RS232-CAn EIA standard for a serial interface between
computers and peripheral devices (modem, mouse, etc.). It
uses a 25-pin DB-25, or a 9-pin DB-9 connector. The
RS232 standard defines the purposes, electrical characteris-
tics and timing of the signals for each of the 25 lines.
RTS (request to send)With communications between
modems, an RS232 signal sent from the DTE to the modem
requesting permission to transmit. Contrast with CTS.
S
scannerA hardware device that can read a photograph or
other piece of artwork and transforms it into a collection of
dots that can be stored as a bit-mapped file on a hard drive.
It then can be manipulated into various software programs
and placed electronically in a page layout program.
SDLC (Synchronous Data Link Control)In IBMs SNA
networks, this is the primary data link protocol.
serial portThe connector on a PC used to attach a serial
device (a device that needs to receive data one bit after
another), such as a mouse, printer or modem. It consists of
a 9- or 25-pin connector that sends data in sequence. Serial
ports are referred to as COMx ports, where x is 1 to 4
(COM1 through COM4). A serial port contains a conver-
sion chip called a UART, which translates between internal
parallel and external serial formats.
serverA computer that provides disk space, printer access,
or other shared services, to computers over a network.
softwareThe set of instructions that make computer
hardware perform tasks. Programs, operating systems,
device drivers and applications are all software.
spoofingA command recognized by modems which have
been manufactured specifically for use within the UNIX
UUCP (UNIX to UNIX Copy) facility. Spoofing is the
process of transparently disabling the g protocol used by
UUCP and substituting the modems own error correction
protocol for data integrity. The process spoofs the UNIX
host into transmitting data faster than normal because
acknowledgments are actually sent by the modem instead of
the remote UNIX computer.
spooling (simultaneous peripheral operations online)
Overlapping a low-speed operation with normal processing,
such as printing a file or document in the background while
creating a new document in the foreground.
SPX (Sequenced Packet Exchange)A data transport
protocol developed by Novell used for interprocess
communications. It guarantees that an entire message
arrives intact and uses the NetWare IPX protocol as its
delivery mechanism.
switch lineIn communications, a physical channel estab-
lished by dynamically connecting one or more discreet
segments. This connection lasts for the duration of the call
after which each segment may be used as part of a different
channel. Contrast with leased line.
switched networkA network in which a temporary
connection is established from one point via one or more
segments.
synchronous transmissionThe transmission of data, which
involves sending a group of characters in a packet. This is a
common method of transmission between computers on a
network or between modems. One or more synchronous
characters are transmitted to confirm clocking before each
packet of data is transmitted. Compare to asynchronous
transmission.
T
T1 transmissionA standard transmission speed of
1.544Mbps that may be used in its full bandwidth or as
narrower channels called fractional T1 carriers.
TCM (trellis coded modulation)An error correction
method that allows the receiving modem to tell if a signal
element is in error, based on the value of the preceding
signal elements. Each signal element is assigned a coded
binary value representing the elements phase and ampli-
tude.
terminalThe screen and keyboard device used in a
centralized computing environment for interactive data
entry. Terminals have no box, which is to say they have no
file storage or processing capabilities.
terminal emulationAllows a PC to access a mainframe
computer by generating and accepting data like a dumb
terminal.
thresholdA value or condition which, when reached,
triggers an event.
toggleAlternate back and forth between two states.