Multi-Tech Systems MTA128ST-USB - Manual (Page 89)

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Glossary
MTA128ST-USB
IRQ (interrupt request)—The notification a processor
receives when another portion of the computer’s hardware
requires its attention. IRQs are numbered so that the
device issuing the IRQ can be identified, and so that IRQs
can be prioritized.
ISA (Industry Standards Architecture)—Pronounced ice-a.
The classic 8- or 16-bit architecture introduced with IBM’s
PC-AT computer. Due to speed constraints, IBM later
introduced a restructured Micro Channel Architecture with
a 32-bit bus and increased addressing capabilities.
ISDN (Integrated Services Digital Network)—International
telecommunications standard for transmitting voice, video
and data over a digital communications line.
ITU-T (formerly CCITT)—International Telecommunications
Union–Telecommunications Sector; the United Nations
organization that prepares standards for resolving
communications issues and problems.
L
LAPB (Link Access Procedure Balanced)—Based on the
X.25 Layer 2 specification. A full-duplex, point-to-point, bit-
synchronous protocol commonly used as a data link control
protocol to interface X.25 DTEs. LAPB is the link
initialization procedure that establishes and maintains
communications between the DTE and the DCE.
LAPD (Link Access Protocol for the
D-Channel)—Based on the ISDN Q.921 specification. A
full-duplex point-to-point bit-synchronous link-level protocol
for ISDN connections; different from LAPB in its framing
sequence. Transmission is in units called frames, and a
frame may contain one or more X.25 packets.
link optimization—An ISDN feature that permits only user
data to open the communications link and keeps
administrative packets from opening the link. A cost saving
feature that ensures that remote connections are not
unnecessarily utilized.
local loop—A transmission path, typically twisted-pair
wire, between an individual subscriber and the nearest
public telecommunications network switching center. Also
called the subscriber loop.
LT (loop termination)—A device, similar to an NT1, that
terminates the local loop at the carrier’s central switching
office. The LT provides the interface to the ISDN U
reference point. Contrast ET (exchange termination).
M
ML-PPP (Multilink PPP)—An open standard for inverse
multiplexing, allowing two 64 bps ISDN B channels to be
multiplexed into one 128 Kbps link.
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 USB port.
MSN (Multiple Subscriber Number) - Allows a caller to
specify an individual terminal adapter when more than one
unit is connected to your network terminator. An MSN
consists of a base address and a subaddress. If you
assisgn a base address only, the unit accepts any
incoming call with the same base address, regardless of
whether a subaddress is included. If you assign a base
address and a subaddress, the unit only accepts calls that
match both the base address and the subaddress.
multilink—In point-to-point protocol, literally many links. A
procedure used to route data packets over many links for
increased bandwidth (e.g., two B-channels on a single BRI
for 128 Kbps).
mux (multiplexer)—A device that merges several signals
into one composite signal for transmission over a single
medium or channel. A demultiplexer, built into most muxes,
reverses the process at the receiving end.
N
nailed connection—A permanent or dedicated circuit of a
previously switched circuit or circuits.
nailed-up circuit—A semi-permanent circuit established
through a circuit-switching facility for point-to-point
connectivity.
NAK (negative acknowledgment)—A 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.
NI-1 (National ISDN-1)—A physical standard to make all
compliant ISDN lines appear the same. With ISDN-1
installed, additional costs are not incurred when changing
from prestandard ISDN to standard ISDN. Most RBOCs
now are moving to ISDN-1.
NI-2 (National ISDN-2)—A physical standard subsequent
to NI1. When tested and deployed, NI-2 will provide
additional features and enhanced plug and play
capabilities.
node—Any point within a network that has been assigned
an address.
NT (network termination)—Devices that form the boundary
between customer premise equipment and telephone
company equipment. Two types of NTs are used: NT1 and
NT2.
NT1 (Network TerminationType 1)—An interface device
used in the BRI portion of ISDN to connect four-wire (S/T)
ISDN devices to the two-wire (2BIQ U) IDN. It provides
basic rate access in a 2B+D format with two 64 bps
channels for voice, data, and video communications. It also
provides one 16 Kbps channel for packet-mode signalling,
low-speed data and telecommunications services at the
OSI Layer 1 level. Similar in function to a DSU/CSU
device.
NT2 (Network TerminationType 2)—A device at the
customer premise (user) side responsible for the ISDN
network connection and for functions such as multiplexing
and switching (may be an intelligent device).
NTE (network terminating equipment)—A set of ISDN
functions residing at the boundary of the IDN and the
subscriber.
NUI (network user identification)—A unique alphanumeric
number provided to dial-up users to identify them to
packet-switched networks world-wide. The number is used
for network access and billing.