Multitech MT5634HD16 User Manual page 71

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 wish 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 character
code for use on a computer. OCR systems can recognize
many different fonts, as well as typewriter and computer-
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.
P
Parameter:
1. A "place holder" in a command which should be
substituted with useful information.
2. The list of acceptable values for a given option or
command.
Parity bit: An extra bit attached to each byte of synchronous
data used to detect errors in transmission.
CommPlete Communications Server
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
International 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.
Computers, 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 worldwide
public voice telephone network that is used as a
telecommunications medium for the transmission of voice,
data and other information.
Glossary
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