Multi-Tech MultiModem ISIHI-2S, Руководство пользователя

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172 MultiModem ISI Hybrid Series, ISIHI-2S
Glossary
C
CAD (computer aided design - pronounced “kad”): A
computerized system used to design products. CAD
systems are high speed workstations or PCs that use CAD
software and input devices, such as graphic tables and
scanners.
Callback security: A security feature available in some
intelligent modems that stores phone numbers. When
activated, the user calling the secured modem must furnish
a recognized password and then provide a code that
corresponds to one of the stored phone numbers. When
these security measures are met, the secured modem
hangs up on the caller and dials the appropriate number to
establish a data communications link.
Capacitor: An electronic device that stores an electrical
charge. It comes in varying sizes for use in anything from
power supplies to the tiny cells in dynamic RAM chips.
When the device is powered down, it’s capacitors lose their
charge.
Carrier signal: An analog signal with known frequency,
amplitude and phase characteristics used as a transport
facility for useful information. By knowing the original
characteristics, a receiver can interpret any changes as
modulations, and thereby recover the information.
Character set: One of a number of coding schemes which
uses binary digits to represent characters, numbers,
punctuation, and/or control characters. Common character
sets are ASCII, ANSI, and EBCDIC.
Checksum: A control field found in synchronous data
packets which contain the results of the error control
algorithm used.
Chip: Also called integrated circuits (IC), they are squares
or rectangles that contain from a few dozen to a few million
electronic components.
CHKDSK (pronounced “check disk”): An external DOS
command that reports free memory and disk space.
CHKDSK must be run directly from DOS or within a batch
file.
Circuit: Any closed path through which electrical current
can flow.
Circuit-switched Network: A technology used by the
PSTN that allocates a pair of conductors for the exclusive
use of one communication path. Circuit switching allows
multiple conversations on one talk path only if the end-users
multiplex the signals prior to transmission.
Circuit switching: The temporary connection of two or
more communications channels using a fixed, non-share-
able path through the network. Users have full use of the
circuit until the connection is terminated.
Clipboard: An electronic holding place for the most recent
cur or copy made from a document. Whatever is on the
clipboard can be pasted into the current document. Only
one item may be on the clipboard at a time. When new copy
is sent to the clipboard the existing copy is eliminated.
When you shut down your computer, whatever is on the
clipboard is lost.
Clock: A timing signal generated by an oscillating circuit
that is used to synchronize data transmissions.
Command: An instruction that tells a computer to begin,
continue, or end a specific operation.
Command mode: One of two states of an intelligent
(programmable) device. The mode in which commands can
be issued to alter operating parameters.
Communications Server: Also known as the Async
Gateway, it is a PC equipped with the appropriate hardware
and software package so it can function as a gateway
between a LAN and its modems or host connections.
COMx Port: A serial communications port on a PC.
CONFIG.SYS file (pronounced “config dot sis”): A text
file that contains configuration commands used when you
start your computer. Commands in the CONFIG.SYS file
enable or disable system features, set limits or resources,
and extend the operating system’s purpose by loading
device drivers.
Cooked data: A term used in UNIX communications to
identify the UNIX command-line data transmitted. This type
of data is noted for a reduction in effective throughput
because it has to be processed, or “cooked” prior to trans-
mission. Compare with raw data.
CPU (central processing unit): The computing part of the
computer. It is made up of the control unit and the ALU
(arithmetic logic unit). The CPU, clock and main memory
make up a computer. When you turn on your computer, an
electrical signal follows a permanently programmed path to
the CPU to clear the leftover data from the chips’ internal
memory registers.
CRC (Cyclic Redundancy Check): A field used in
packetized data that contains two 8-bit BCCs (Block Check
Characters) as the binary result of an algorithm performed
on the data bits in the packet. A CRC is used for error
detection by many synchronous protocols.
CTS (Clear To Send signal): With communications be-
tween modems, an RSs-232 signal sent from the modem to
the DTE that indicates it is ready to accept data. Contract
with RTS.
D
DAA (Data Access Arrangement): The circuitry to isolate
any device from phone lines and their associated equip-
ment.
Daisy-chain: A method of connecting multiple devices in a
series, one after another.