Multi Tech Equipment ISIHI-2S manual 178

Glossary

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 perma- nently 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 the 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 character- istics and timing of the signals for each of the 25 lines.

RTS (Request To Send signal): 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 can then be manipulated into various software programs and placed electronically in a page layout pro- gram.

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 conversion 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 the acknowl- edgments are actually sent by the modem instead of the remote UNIX computer.

Spooling (Simultaneous Peripheral Operations On-line): 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 commu- nications. 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 established 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 comput- ers on a network or between modems. One or more syn- chronous 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.

178 MultiModem ISI Hybrid Series, ISIHI-2S