Multi Tech Equipment ISIHI-2S manual 176

Glossary

LRC (Longitudinal Redundancy Check): An error check- ing method that generates a parity bit from the specified string of bits on a longitudinal track. In a row and column format such as on magnetic tape, LRC is often used with VRC, which creates a parity bit for each character.

M

Macro: A series of keystrokes, commands, and/or menu selections that have been recorded and assigned a key or key combination. When those keys are pressed, the macro is executed from beginning to end.

Magnetic Disk: A non-volatile computer storage device that uses one or more magnetic-coated disk platters that can be recorded over and over again. Hard disks, minifloppies (5-1/ 4”) and microfloppies (3-1/2”) are examples of magnetic disks.

Mainframe: A large, powerful computer used to centralize a data processing environment. It has hundreds of gigabytes of storage space. It uses a frond end processor to connect directly to the communications channels that interconnect terminals and computers.

Megabyte: One million bytes, when describing a data rate. 1M of disk space may actually mean 1,048,576 bytes.

Mid-range computer: A term coined by IBM, referring to any of their Advanced Business Systems computers. This product line was originally called their mini-computers, but as the number of supported users approached mainframe capabilities, the term “mid-range” caught on.

MI/MIC (mode indicate/mode indicate common inter- face): A user definable feature that defines various combi- nations of edge or level detection in Originate or Answer mode, with the Ring Indicator (RI) pulse enabled or dis- abled.

Mnemonics: A term assigned to a complex idea, value, or list of information which is found to be representative of that information. Computer commands are almost entirely mnemonics. Mnemonics are used as memory aids for people.

MNP (Microcom Networking Protocol): A family of communications protocols from Microcom that have be- come de facto standards for error correction and data compression.

MNP Class 3&4: The de facto error correction standard from Microcom.

MNP Class 5: The most widely used data compression scheme before V.42bis took hold. MNP5 offers “2-to-1” data compression.

MNP Class 7: MNP’s “3-to-1” data compression scheme. MNP7 never became a de facto standard because of V.42bis “4-to-1” compression.

Modem: A communications device that enables a computer to transmit information over a telephone line. It converts the

computer’s digital signals into analog signals to send over a telephone line and converts them back to digital signals at the receiving end. Modems can be internal and fit into an expansion slot, or external and connect to a serial port.

Modulation: The process of encoding information from one signal (called the source) into another (called the carrier) by modifying some characteristic(s) of the carrier. It is often used in telecommunications when one type of signal must be converted for transmission over an otherwise incompat- ible medium.

Multiplexer (mux): A device that merges several signals into one composite signal for transmission over a single medium or channel. A de-multiplexer (usually built into a mux) reverses the process at the receiving end.

N

NAK (Negative Acknowledgment): Communications code used to indicate that a message was not properly received or that a terminal does not want to transmit. Contrast with ACK.

Network: A group of computers connected by cables or other means and using software that enables them to share equipment, such as printers and disk drives to exchange information.

NIC (Network Interface Card - pronounced “nick”) : A printed circuit board that provides the physical and electrical connection between a PC and a network device (like a file server) via a network media (like Arcnet UTP).

Node: Any point within a network which has been assigned an address.

Normal mode: In modem operation, this refers to a mode of operation without error correction active.

O

OCR (Optical Character Recognition): The recognition of printed characters and subsequent translation into charac- ter code for use on a computer. OCR systems can recog- nize many different fonts, as well as typewriter and com- puter-printed characters. Advanced OCR systems can recognize hand printing.

Off-hook: The condition of a device which has accessed a phone line (with or without using the line). In modem use, this is equivalent to a telephone handset being picked up. Dialing and transmission are allowed, but incoming calls are not answered.

OS (Operating System): The master control program that runs a computing system. It is the first program loaded when the computer is turned on, and its main part is called the kernel and resides in the memory at all times.

176 MultiModem ISI Hybrid Series, ISIHI-2S