Multitech MultiModem MT5634ZPX User Manual page 56

ITU-TSS (formerly CCITT): International Telecommunications
Union-Telecommunications Sector; the United Nations
organization that prepares standards ("Recommendations") for
resolving communications issues and problems.
J
No Entries.
K
Key Telephone System (KTS): Phone devices with multiple
buttons that let you select incoming or outgoing CO phone lines
directly. Similar in operation to a PBX, except with a KTS you don't
have to dial a "9" to call outside the building.
Key Service Unit (KSU): A small device containing the switching
electronics for a business key telephone system (KTS).
Key Set: A phone set with several buttons for call holding, line
pickup, intercom, autodialing, etc. Also called a touchtone phone
(Ericsson) and a KTS (Key Telephone Set).
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.
Line Coding: The representation of 1s and 0s on a T1 line. The
two methods of line coding commonly used, B8ZS and AMI, differ
in the restrictions placed on user data. T1 line coding ensures that
sufficient timing information is sent with the digital signal to ensure
recovery of all the bits at the far end. Timing information on the T1
line is included in the form of 1s in the data stream; a long string
of 0s in the data stream could cause problems recovering the
data.
Line Termination (LT): The electronics at the ISDN network side
of the user/network interface that complements the NT1 at the
user side. The LT and the NT1 together provide the high-speed
digital line signals required for BRI access.
Listed Directory Number (LDN): The main number assigned by
the telco; the number listed in the phone directory and also
provided by Directory Assistance. Some devices can have more
than one LDN, such as ISDN devices that have one LDN for voice
and another LDN for data.
Local Area Network (LAN): 1. A computer network located on a
user's premises within a limited geographical area.
Communication within a local area network is not subject to
external regulations; however, communication across the LAN
boundary may be subject to some form of regulation. 2. A LAN
does not use store-and-forward techniques. 3. A network in which
a set of devices are connected to one another for a
communication and that can be connected to a larger network.
Local Access and Transport Area (LATA): A post-divestiture
geographical area generally equivalent to a Standard Metropolitan
Statistical Area. At divestiture, the territory served by the Bell
system was divided into approximately 161 LATAs. The Bell
Operating Companies (BOCs) provide Intra-LATA services.
Multi-Tech Systems, Inc. MT5634ZPX User Guide
Local Exchange Carrier (LEC): The local phone company which
provides local (i.e., not long distance) transmission services. AKA
"telco". LECs provide T1 or FT1 access to LDCs (unless the T1
circuit is completely intra-LATA). Inter-LATA T1 circuits are made
up of a combination of Access and Long Haul facilities.
Local Management Interface (LMI): A specification for frame
relay equipment that defines status information exchange.
Local Loop: A transmission path, typically twisted-pair wire,
between an individual subscriber and the nearest public
telecommunications network switching center. The wires provide
ISDN service, but require an NT1 at the user end and an LT at the
network end. (AKA, "loop" or "subscriber loop".)
Logical Link Control (LLC2): In a local area network, the
protocol that governs the exchange of transmission frames
between data stations independently of how the transmission
medium is shared. The LLC2 protocol was developed by the IEEE
802 commitee and is common to all LAN standards.
Logical Unit (LU): A type of network accessible unit that enables
end users to gain access to network resources and communicate
with each other.
Long Haul: The T1 element that connects to the Access portion of
the long distance company's (LDC's) central office. The LDC is
commonly called the point of presence (POP). Each LDC has a
number of POPs, located throughout the country. The LDC is also
called an IEC (Inter Exchange Carrier).
Long Haul Communications: The type of phone call reaching
outside of a local exchange (LE).
M
Management Information Base (MIB): A database of network
management information used by the Common Management
Information Protocol (CMIP) and the Simple Network Management
Protocol (SNMP).
Megacom: An AT&T service with a normal WATS line (typically
T1) between the customer premise and the AT&T serving class 4
CO are the customer's responibility.
MegaLink: BellSouth's leased T1 service.
Message: Associated with such terms as packet, frame, and
segment. 1. In information theory, an ordered series of characters
intended to convey information. 2. An assembly of characters and
sometimes control codes that is transferred as an entry from an
originator to one or more recipients.
Message Pipe: A pipe that transfers data using a request/data/
status paradigm. The data has an imposed structure which allows
requests to be reliably identified and communicated.
Modem: A communications device that enables a computer to
transmit information over a phone line. It converts the computer's
digital signals into analog signals to send over a phone 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.
Multiplexer (Mux): 1. A device that takes several input signals
and combines them into a single output signal in such a manner
that each of the input signals can be recovered. 2. A device
capable of interleaving the events of two or more activities or
capable of distributing the events of an interleaved sequence to
the respective activities. 3. Putting multiple signals on a single
channel.
Multiprotocol: A device that can interoperate with devices utilizing
different network protocols.
Multithreading: The ability of a software system to be able to
handle more than one transaction concurrently. This is contrasted
to the case where a single transaction is accepted and completely
processed befor the next transaction processing is started.
Glossary
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