Multi Tech Equipment manual MultiModemISI Hybrid Series, ISIHI-2S 177

Glossary

P

Parameter: 1. A “place holder” in a command that should be substituted with useful information. 2. The list of accept- able values for a given option or command.

Parity bit: An extra bit attached to each byte of synchro- nous data used to detect errors in transmission.

PCB (Printed Circuit Board): A flat board that holds chips and other electronic components. The board is “printed” with electrically conductive pathways between components. The main PCB in a system is called a motherboard and the smaller PCBs that plug into the slots in the motherboard are called daughter boards or cards.

PCMCIA (Personal Computer Memory Card Interna- tional Association): An organization of U.S. and Japanese companies set up to standardize memory cards and other architecture-independent expansion devices. These cards are typically used in laptop computers.

Phase: The timing of a signal based upon the starting point of each cycle in another signal. To be detected, phase requires the comparing of two signals. If the cycle of two signals begin at the same point, they are said to be “in- phase”. In-phase signals add, while out-of-phase signals tend to cancel each other.

Port: A location for input or output data exchange. Comput- ers, muxes, etc., have ports for various purposes.

Print Server: A computer in a network that controls one or more printers. It stores the print image output from all users of the system and feeds it to the printer one job at a time. The print server may be part of the network operating system or an add-on utility.

Program: A collection of computer instructions that tell the computer what to do.

PROM (Programmable Read Only Memory): A permanent memory chip that can be programmed or filled by the customer after the manufacturer has set initial values. Contrast with ROM.

Prompt: A request for information from the PC that provides required input or information.

Protocol: A set of rules that defines how computing devices communicate with each other. The rules governing the transmitting and receiving of data.

PSK (Phase Shift Keying): A modulation technique which establishes two-bit elements, called “dibits” yielding four possible combinations: 00,01,10,11. These element are then represented by 90, 180 and 270 degree angles. PSK produces the appropriate shift in phase relative to the original carrier. Differential PSK replaces this technology because it is less prone to error. Modems using PSK normally operate at 1200 bps.

PSTN (Public Switched Telephone Network): A world- wide public voice telephone network that is used as a telecommunications medium for the transmission of voice, data and other information.

Pulse dialing: One of two methods of dialing a telephone, usually associated with rotary dial phones. Compare with tone dialing.

Pulse-width: Pertaining to a digital signal. Pulse width refers to the duration of one state between clocking signals. Pulse width roughly corresponds to an analog signal’s wavelength.

Q

QAM (Quadrature Amplitude Modulation): A complex method of modulation that establishes twelve phase angles and four amplitudes, designating sixteen possible combina- tions. QAM encodes hexadecimal values (also called quadbits) into one cycle of the carrier. Using a 1800 bps carrier frequency and a 2400 baud signaling rate, QAM provides a 9600 bps modulation speed. However, because it uses amplitude modulation, QAM is susceptible to noise.

Queue: A set of activities that are waiting in chronological order for an action, such as printing, to be performed.

R

Rack: A frame or cabinet into which components are mounted. The industry standard rack is 19” wide and has variable depth and height.

Rackmount: A packaging style available for many types of electronic equipment which enables the installer to mount the equipment in an industry standardized enclosure. The rackmount equipment is fitted with brackets, rather than being packages in its own enclosure. Rackmounting conserves disk and floor space (real estate) and often conserves power outlets.

RAM (Random Access Memory): A computer’s primary workspace. All data must be stored in RAM (even for a short while) before software can use the processor to 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.

MultiModemISI Hybrid Series, ISIHI-2S 177