Multi Tech Equipment ISIHI-2S manual 172

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.

172 MultiModem ISI Hybrid Series, ISIHI-2S