m - Milli,
M - Mega,
one million (e.g. Mbps or Mbit/s, one million bits per second).
MAC (Media Access
Control) - A media-specific access control protocol within IEEE
802 specifications; currently includes variations for Token Ring, token bus,
and CSMA/CD; the lower sublayer of the IEEE's link layer (OSI), which
complements the Logical Link Control (LLC).
MAC Address -
Hardware address that uniquely identifies each node on a network.
- Contacts which make with new contacts before they break with the
contacts with which they are associated in the rest position of a relay or
Make Contacts - The
contacts of a relay which will be open when the relay is de-energized and
closed when the relay is energized.
MAN (Metropolitan Area
Network) - A network designed to carry data over an area larger than a
campus, such as an entire city and its outlying area.
Manual By-Pass -
The ability to manually switch a standby power system to operate from AC
current only for maintenance purposes.
Master Office - A
central office which acts as parent office for smaller offices and through
which all calls to the smaller offices are routed. Also called
MAU (Media Attachment Unit)
- Device used in Ethernet and IEEE 802.3 networks that provides the interface
between the AUI port of a station and the common medium of the Ethernet. The
MAU, which can be built into a station or can be a separate device, performs
physical layer functions including conversion of the digital data from the
Ethernet interface, collision detection, and injection of bits onto the
maxCR (Maximum Cell Rate)
- The maximum cell rate for an entire path regardless of the number of channels
on the path.
maxCTD (Maximum Cell
Transfer Delay) - Specifies end-to-end cell transfer delay.
Maximum Burst Tolerance
- the largest burst of data that a network device is guaranteed to handle
without discarding cells or packets. Bursts of data larger than the maximum
burst size may be subject to discard.
MBS (Maximum Burst Size)
- In the signaling message, the Burst Tolerance (BT) is conveyed through the
MBS which is coded as a number of cells. The BT together with the SCR and the
GCRA determine the MBS that may be transmitted at the peak rate and still be in
conformance with the GCRA.
Control Center) - The area of the central office used by
the plant personnel to survey system operation, as well as traffic and
alarm monitoring. The center will group reporting devices, data sets and
visual displays in one space. This is the area from which a digital system
would be monitored and controlled within the building. Power alarm
indications which impact on the switching system are often extended into
MCDV (Maximum Cell Delay
Variance) - This is the maximum two-point CDV objective across a link
or node for the specified service category.
MCLR (Maximum Cell Loss
Ratio) - This is the maximum ratio of the number of cells that do not
make it across the link or node to the total number of cells arriving at the
link or node.
MCR (Minimum Cell Rate)
- Parameter defined by the ATM Forum for ATM traffic management. MCR is defined
only for ABR transmissions, and specifies the minimum value for the ACR.
MCTD (Maximum Cell
Transfer Delay) - This is the sum of the fixed delay component across
the link or node and MCDV.
MDF (Main Distribution
frame) - A distribution frame on one part of which terminate the
permanent outside lines entering the central office building and on
another part of which terminate the subscriber line multiple cabling,
trunk multiple cabling, etc.
Membership Scope -
The level of routing hierarchy within which advertisement of a given address is
Message Alert (also called
"call-in-absence" indicator) - A light or other
indicator announcing that a phone call came in, an especially important
feature if the cellular subscriber has voice mail.
Metasignaling - An
ATM Layer Management (LM) process that manages different types of signaling and
possibly semipermanent virtual channels (VCs), including the assignment,
removal, and checking of VCs.
Metasignaling VCs -
The standardized VCs that convey metasignaling information across a
User-to-Network Interface (UNI).
Meter Assembly -
Display of the discharge current and the battery string voltage.
MHz - Abbreviation
for Megahertz, one million Hertz (one million cycles per second).
MIB (Management Information
Base) - The set of parameters that an SNMP management station can
query or set in the SNMP agent of a networked device (e.g., router).
MIC (Media Interface
Connector) - The optical fiber connector that joins the fiber to the
MicroChannel - A
proprietary 16- or 32-bit bus developed by IBM for its PS/2 computers' internal
expansion cards; also offered by others.
Microprocessor - An
electronic circuit, usually on a single chip, which performs arithmetic,
logic and control operations, customarily with the assistance of internal
One-millionth of a second.
Microwave - A term
loosely applied to those radio frequency wavelengths which are
sufficiently short to exhibit some of the properties of light.
Commonly used for frequencies from about 1 GHz to 30 GHz.
- Any of the frequencies suitable for microwave communication. Most common
are the 2 GHz, 4 GHz and 6 GHz bands.
Microwave Radio -
Radio communications using frequencies between approximately 1 GHz and
Identifier) - The message identifier is used to associate ATM cells
that carry segments from the same higher layer packet.
One-thousandth of a second.
MJ - A major alarm
classification, not necessarily a power alarm.
MMF (Multimode Fiberoptic
Cable) - Fiberoptic cable in which the signal or light propagates in
multiple modes or paths. Since these paths may have varying lengths, a
transmitted pulse of light may be received at different times and smeared to
the point that pulses may interfere with surrounding pulses. This may cause the
signal to be difficult or impossible to receive. This pulse dispersion
sometimes limits the distance over which a MMF link can operate.
MN - (1) A minor
alarm classification, not necessarily a power alarm. (2) A lead
designation connecting between a self-contained alarm circuit and the
office alarm frame signifying a minor audible alarm.
Mobile Telephone -
Radio telephone service provided to vehicles from a broadcast point
located within range of the moving vehicle. The broadcast point in
turn can be connected to the public network so that calls can be completed
to or from any stationary telephone.
Modem - Acronym for
modulator-demodulator. (1) A device that modulates and
demodulates signals, primarily converting digital signals into
quasi-analog signals for transmission and for reconverting the
quasi-analog signals into digital signals; (2) in frequency division
carrier systems, devices that change the frequency of a signal, voice band
on one side, and the carrier frequency with either erect or inverted
sidebands on the other side.
Modular - (1)
Having dimensions which are integral multiples of a unit of length called
a module; (2) in switching equipment, designed and manufactured in
functional modules so that individual modules may be later replaced by
Monitor - A
device for recording or controlling an activity or process.
Mother Board - The
heart of the alarm interface/isolation bay design consisting of diode
sets, relays, terminal strips and lamps which are housed in a
framework intended to be located in the power board line.
MPC (MPOA Clients) -
Edge devices and host terminals running MPOA software.
MPEG (Motion Picture Experts
Group) - An ISO Standards group dealing with video and audio
compression techniques and mechanisms for multiplexing and synchronizing
MPOA (Multiprotocol over
ATM) - An effort taking place in the ATM Forum to standardize
protocols for the purpose of running multiple network layer protocols over ATM.
MPOA Client - A
device which implements the client side of one or more of the MPOA protocols,
(i.e., is a SCP client and/or an RDP client. An MPOA Client is either an Edge
Device Functional Group (EDFG) or a Host Behavior Functional Group (HBFG).
MPOA Server - An
MPOA Server is any one of an ICFG or RSFG.
MPOA Service Area -
The collection of server functions and their clients. A collection of physical
devices consisting of an MPOA server plus the set of clients served by that
MPOA Target - A set
of protocol address, path attributes, (e.g., internetwork layer QoS, other
information derivable from received packet) describing the intended destination
and its path attributes that MPOA devices may use as lookup keys.
MPS - MPOA Servers
ATM Routers running MPOA software.
Statistical Area) - The FCC divided the United States into MSA
markets and Rural Service Area (RSA) markets. There are 306 MSAs in
the United States, all of which now have cellular service.
MSB (Most Significant Bit)
- The highest order bit in the binary representation of a numerical
MTBF (Mean Time Between
Failure) - The average time a manufacturer estimates before a
failure occurs in a component, a printed circuit board or a
MTBO (Mean Time Between
Outages) - The mean time between equipment failures or
significant outages which essentially render transmission useless.
MTSO (Mobile Telephone
Switching Office) - The central switch that controls the entire
operation of a cellular system. It is a sophisticated computer
that monitors all cellular calls, keeps track of the location of all
cellular-equipped vehicles traveling in the system, arranges handoffs,
keeps track of billing information, etc.
MTSR (Mean Time To Service
Restoral) - The mean time needed to restore service following
system failures that result in a service outage.
MTTR (Mean Time To Repair)
- The vendor's estimated average time required to do routine repairs on
MTU (Maximum Transmission
Unit) - The largest unit of data that can be sent over a type of
Mu-Law - The PCM
coding and companding standard used in Japan and North America.
Multicasting - The
ability to broadcast messages to one node or a select group of nodes.
Multi-homed - A
device that has both an ATM and another network connection, typically Ethernet.
multimode fiber -
Type of fiber optic cable with a larger center core than single mode fiber.
Multimode fiber is generally used over relatively short distances.
Multiplexing - A
function within a layer that interleaves the information from multiple
connections into one connection (see demultiplexing).
Multipoint Access -
User access in which more than one terminal equipment (TE) is supported by a
single network termination.
Connection - A Point-to-Multipoint Connection may have zero bandwidth
from the Root Node to the Leaf Nodes, and non-zero return bandwidth from the
Leaf Nodes to the Root Node. Such a connection is also known as a
Connection - A collection of associated ATM VC or VP links, and their
associated endpoint nodes, with the following properties:
1. All N nodes in the connection, called Endpoints, serve as a Root Node in a
Point-to-Multipoint connection to all of the (N-1) remaining endpoints.
2. Each of the endpoints can send information directly to any other endpoint,
but the receiving endpoint cannot distinguish which of the endpoints is sending
information without additional (e.g., higher layer) information.
Multitasking - The
simultaneous performing of two or more tasks by a computer.
MUX (Multiplexer) -
Electronic equipment which allows two or more signals to pass over one