MDBS-Metering Pulses

MDBS-Metering Pulses


Mobile Data Base Station.


Meridian Digital Centrex. A Northern Telecom abbreviation.


MultiDrop Data Bridge. MDDB. A technique for combining data circuits in a computer environment in which the host machine polls other equipment.


Main Distribution Frame. See Main Distribution Frame.


Medium Dependent Interface.


Modem Developer's Kit. Definition invented, I believe, by Microsoft.


Mobile Data Link Protocol. The Link Layer protocol defined in CDPD networks.


Multiple Data Message Format. See Caller ID Message Format.


Mobile Dialing Number. The originating telephone number of the cellular caller.


Medium-Density PolyEthelyne. A type of plastic material used to manufacture jacketing for cable systems.


Market Driven Quality. An IBM term of the mid-1980s.


Multibank Dynamic Random Access Memory. Memory normally used in video boards that boasts extended performance with high bandwidth and short access times. The MDRAM chip can access several memory banks at a time.


  1. An FCC term for a fixed station operating between 2.15 and 2.162 GHz.

  2. Multipoint Distribution Service.


Message Delivery Service Interoffice. Data link using a 9600 baud modem asynchronous 10-bit character transmission. An obsolete term.


Mean Down Time.


  1. Message Display Unit. See Readerboard.

  2. Multiple Dwelling Unit. Any housing structure that is broken into more than one living area to accommodate multiple "family" units (apartment buildings , condominiums, duplexes, etc.).


Multiple Dwelling Units. Telephony jargon for high-rise apartment buildings. See also Planned Communities.


Mobile Digital Voice Channel. The channel between a mobile phone and a cell site antenna in a digital cellular or PCS environment. The MDVC supports both voice and data transmission, although the allocated bandwidth is designed primarily to support voice. Signaling and control functions take place over separate channels set aside specifically for that purpose.


Metropolitan dense wave division multiplexing. It is DWDM technology which boosts the carrying capacity of fiber optic telecommunication networks. See DWDM.


Mechanical Engineer.


Metropolitan Economic Area. See Metropolitan Statistical Area and MSA.


A system for receiving radio beacon signals and retransmitting them on the same frequency to confuse navigation and cause inaccurate bearings to be obtained by aircraft or ground stations .


The sum of all items divided by the number of items, e.g., for the five numbers 7, 7, 8, 10, and 11, the mean is (7 + 7 + 8 + 10 + 11)/5 = 43/5 = 8.6. The average (also the arithmetic average) and the mean are the same. What's different is the median. The median of a set is the number that divides the set in half, so that as many numbers are larger than the median as are smaller. The median of 7, 7, 8, 10, and 11 is 8. If the set has an even number of elements, the median is the number halfway between the middle pair. the median is widely used as a measure of central tendency. See several Mean definitions below.

Mean Busy Hour

For a telephone line or group of lines or a switch the Mean Busy hour is the 60 minute period where traffic is the greatest.

Mean Deviation

An average of all deviations, plus or minus from the mean. It is occasionally used as a measure of dispersion.

Mean Launched Power

The average power forma continuous valid symbol sequence coupled into a fiber.

Mean Opinion Score

See MOS.

Mean Power Of A Radio Transmitter

The average power supplied to the antenna transmission line by a transmitter during an interval of time sufficiently long compared with the lowest frequency encountered in the modulation taken under normal operating conditions. Normally, a time of 0.1 second, during which the mean power is greatest, will be selected.

Mean Time Between Failure

MTBF. The average time a manufacturer estimates before a failure occurs in a component, a printed circuit board or a complete telephone system. One must check, since MTBFs are cumulative. MTBF was developed and administered by the U.S. military for purposes of estimating maintenance levels required by various devices and systems. Since accurate statistics require a basis of "failures per million hours of operation," an MTBF estimate on a single device is not very accurate; it would take 114 years to see if the device really had that many failures! Similarly, since the MTBF is an estimate of averages, half of the devices can be expected to fail before then, and half after. MTBF cannot be used as a guarantee. Telecommunications systems operate on the principle of "Availability," for which there is a body of CCITT Recommendations.

Mean Time Between Outages

MTBO. The mean time between equipment failures or significant outages which essentially render transmission useless. See Mean Time Between Failure.

Mean Time To Repair

MTTR. The vendor's estimated average time required to do repairs on equipment.

Mean Time To Service Restoral

MTSR. The mean time to restore service following system failures that result in a service outage . The time to restore includes all time from the occurrence of the failure until the restoral of service.

Measured Load

The load that is indicated by the average number of busy servers in a group over a given time interval, usually determined with a scanning device.

Measured Rate

A message rate structure in which the monthly phone line rental includes a specified number of calls within a defined area, plus a charge for additional calls. See Local Measured Service.

Measured Service

Also known as USAGE SENSITIVE PRICING (USP). A local phone company method of pricing used to bill local phone calls. Measured service is often charged on the number of calls, the time of day, the distance traveled and the length of the call. See Local Measured Service.

Measurement Interval

Tc (Time committed). A Frame Relay term defining the interval of time which the carrier uses to measure data rates that burst above the CIR (Committed Information Rate). See also Committed Information Rate.


A slang term for an ambulance.


People. See also Vaporware.


Mobile ECommerce. See 3G.


Multiple Exchange Carrier Access Billing.


Master Event Calendar.


Mercury Exchange Limited Channel Associated Signaling. A family of signaling techniques used by Mercury Communications Limited (MCL), a service provider in the U.K. MELCAS is used for signaling over E&M and FX trunks, for example. See also CAS, E&M, FX, and MCL.


Multiplex Engineering Control Center Activity.


A programmer.

Mechanical Equipment Room

A room serving the space needs for HVAC and other building systems other than telecommunications equipment. These are often special-purpose rooms.

Mechanical Hold

A very basic line-holding mechanism used on simple two- and three-line phones that operated by placing a short circuit or a resistor across one phone line while talking on another. Chief disadvantage was that a call put on hold at one phone could not be taken off hold at another phone. Inexpensive multi-line phones with electronic holds largely replaced mechanical holds in the 1980s.

Mechanical Loop Test

MLT. Also called Direct-Access Test Unit (DATU) added or built into a central office switch. With MLT a technician can execute tests for shorts, opens and grounds remotely. The technician gets a digital voice, enters a password and is given a series of options. The technician can get results as a digital recording or through an alphanumeric pager. MLT units can send a locating tone as TIP, RING or a combination of both. The unit can short lines and remove battery voltage for testing.

Mechanical Splice

A splice in which optical glass fibers are joined mechanically (e.g., glued or crimped in place) but not fused (i.e. melted) together.

Mechanical Strength

Mechanical strength refers to the capacity of a network element to endure various physical forces. The term commonly is used with respect to transmission media such as coaxial cable, twisted pair, and optical fiber. Mechanical strength includes flex strength, tensile strength, break strength, and bend radius. See those terms for more detail.

Mechanical Stripping

Removing the coating from a fiber using a tool similar to those used for removing insulation from wires.

Mechanized Calling Card Service

MCCS was formerly known as ABC Service. MCCS is a central office switch feature that automatically bills credit card calls made on DDD (direct distance dial) rates without the involvement of an operator.

Mechanized Loop Testing

MLT. The system provides computer control of accurate and extensive loop testing functions in the customer contact, screening, testing, dispatch and closeout phases of trouble report handling. It also provides full diagnostic outputs instead of just pass/fail indications .

Mechanized Loop Test

MLT. A test system that tests the end user's loop, which is comprised of the wires and equipment used to provide dial tone/calling service to that end user .


From MIT's Technology Review, "To improve everything from fuel economy to performance, automotive researchers are turning to "mechatronics," the integration of familiar mechanical systems with new electronic components and intelligent -soft- ware control. Take brakes. In the next five to 10 years, electromechanical actuators will replace hydraulic cylinders ; wires will replace brake fluid lines; and software will mediate between the driver's foot and the action that slows the car. And because lives will depend on such mechatronic systems, Rolf Isermann, an engineer at Darmstadt University of Technology in Darmstadt, Germany, is using software that can identify and correct for flaws in real time to make sure the technology functions impeccably. "There is a German word for it: gr ¢ndlich," he says. "It means you do it really right." In order to do mechatronic braking right, Isermann's group is developing software that tracks data from three sensors: one detects the flow of electrical current to the brake actuator; a second tracks the actuator's position; and the third measures its clamping force. Isermann's software analyzes those numbers to detect faults ” such as an increase in friction - and flashes a dashboard warning light, so the driver can get the car serviced before the fault leads to failure. "Everybody initially was worried about the safety of electronic devices. I think people are now becoming aware they are safer than mechanical ones," says Karl Hedrick, a mechanical engineer at the University of California, Berkeley. "A large part of the reason they are safer is you can build in fault diagnoses and fault tolerance."


Multiple Exchange Carriers Ordering and Design.


In the context of telecommunications, media is most often the conduit or link that carries transmissions. Transport media include coaxial cable, copper wire, radio waves, waveguide and fiber.

Media Access Control

MAC. The real term is Medium Access Control. But some naughty people call it, incorrectly, Media Access Control. See Medium Access Control for a full explanation.

Media Access Control Convergence Functions

MCF. Media Access Control Convergence performs functions or processes which map information received from IEEE 802.2 Layer 2 LLC into a format acceptable to the lower layer medium.

Media Compatible

Usually used to refer to floppy disk media. Even though two different computers (e.g. an AT&T PC 6300 and an Apple IIe) both use 5 1/4 inch floppy disks, the information recorded on them is recorded in a different format and thus, they are not media compatible. You can put one disk in another's machine. But it won't work. You'll get a dumb error message.

Media Filter

A device used to convert the output signal from a token-ring adapter board to work with a specific type of wiring. For example, a media filter can link 16Mbps token-ring network interface cards with unshielded twisted-pair (UTP) wiring, thus saving the expense of additional cable runs.

Media Gateway

A piece of equipment that changes streams of traditional TDM encoded telecom to a single stream of IP (Internet Protocol). There are several advantages to doing this:

  1. You save money. You don't need separate networks.

  2. You save management time. You manage only one network, not several.

  3. Adds, moves and changes should be easier. Moving a phone on an IP network is much easier than moving a conventional TDM PBX phone. See also MGCP.

Media Gateway Controller


Media Gateway Control Protocol


Media Hub

A fancy name for a server which doles out audio, video and photographs to various devices around the house. The idea is the media hub will be connected to the Internet, so it can download movies, songs, photographs, magazines and newspapers for viewing, reading and listening to all around the house.

Media Independent Interface

MII. A part of the Fast Ethernet specification. The MII replaces 10Base-T Ethernet's Attachment Unit Interface (AUI), and is used to connect the MAC layer to the physical layer. The MII establishes a single interface for the three 100Base-T media specifications (100Base-TX, 100Base-T4, and 100Base-FX).

Media Interface Connector

An optical fiber connector which links the fiber media to the FDDI node or another cable.

Media Path

Same as wire run. The means by which telephone signals are conveyed from the Network Interface Jack to the Communications Outlet.

Media Processing

The processing of transactions during a telephone call; these transaction may include fax operations, speech recognition and synthesis, Touch Tone recognition, voice and fax store-and-forward messaging, and the conversion of messages from one format to another (such as from text to voice, or fax to text).

The DM/V-A multifunction and resource series boards provide up to 120 channels of continuous speech processing, conferencing, or other media processing features such as:

  • silence compressed record

  • message storage using G.711 -law or A-law pulse code modulation (PCM) or OKI adaptive differential pulse code modulation (ADPCM)

  • compressed recordings using True Speech, GSM, and G.726 low-bit rate coders

  • automatic gain control (AGC) to automatically adjust the signal level of incoming calls

  • application's ability to dynamically switch sampling rate and coding method to optimize data storage and voice quality

  • sampling rates and coding methods that are selectable on a channel-by-channel basis

  • dynamic adjustment of playback volume

  • detect dual-tone multifrequency (DTMF) to control record and play functions

  • local echo cancellation techniques to improve DTMF cut-through and talk off/play off

  • voice player and recorder resources are linked with the DTMF

  • 240 channels of basic voice and up to 1200 ports in the system

Media Processor

A special microprocessor whose job is to perform processing for multimedia devices, e.g. videophones, audio, computer telephony devices, voice recognition and 3-D, while the computer's main microprocessor (e.g. a Pentium) handled the basic processing and input/output (I/O) processing. Such media processors might have all the characteristics of digital signal processors and then some. See also MMX.

Media Server

  1. A media server is a fancy name for a file server on a network which contains files containing voice, images, pictures, video, etc. In short, a media server is a repository for media of all types. Basically they're called media servers because they serve up media to anyone who asks for it, is on the network and is authorized to get it. Media servers are also called file servers.

  2. The IP telephony community refers to a media server as a slave IP call processing and handling device. Several companies make a combination hardware/software tool which, among other things, collects digits, plays announcements, and establishes IVRs (interactive voice response).

Media Service Instance

A logical server providing access to media services (e.g., accessing a datastream, sending and receiving faxes, playing & recording sounds, engaging other VRU services) that can be associated with a call through a Media Access Device. See MediaStreamID.

Media Stream

The information content carried on a call-that is, what actually is transmitted and received over the line, and can, with the necessary hardware, be read and written by a media stream API.

Media StreamID

Allows an association to be established between a given call and Media Services available on a Media Service Instance that can be associated with the call through a Media Access Device. See Media Service Instance.

Media Type

A call's media type describes what type of information the call is carrying, such as data or voice. A computing domain can use this information, for example, to route the call to a more appropriate computing domain, such as a data computing domain for an incoming data call.


The average and the mean are the same. What's different is the median. If you say the median price earnings ratio of the S&P 500 was 15.9, that means that half of all stocks traded below that valuation and the other half traded above it. See Mean for a full explanation.

Mediated Access

A Verizon definition. Mediated access allows CLECs to use Verizon network facilities, switches, and operating systems while prohibiting access to proprietary Verizon databases.

Mediation System

A wireless telecommunications term. A mediation system provides for three functions for transporting data from one device to another. These include protocol conversion, message routing, and store-and-forward processing.


  1. The material on which data is recorded; for example, magnetic type, diskette.

  2. Any material substance that is, or can be, used for the propagation of signals, usually in the form of modulated radio, light, or acoustic waves, from one point to another, such as optical fiber, cable, wire, dielectric slab, water, air, or free space.

Medium Access Control

MAC. The IEEE sublayer in a LAN (Local Area Network) which controls access to the shared medium by LAN-attached devices. In the context of the OSI Reference Model, the MAC layer extends above to the Data Link Layer (Layer 2), and below to the Physical Layer (Layer 1). Within the MAC sublayer are defined Data Link Layer options which specify the basis on which devices access the shared medium, and the basis on which congestion control is exercised. Defined at the Physical Layer are media options such as UTP (Unshielded Twisted Pair) CAT 3, 4, and 5 (Categories of wire); STP ( Shielded Twisted Pair); fiber optic cable; and wireless radio and infrared. Specific IEEE MAC standards are defined for LANs such as CSMA/CD (802.3), Token Passing Bus (802.4), Token Passing Ring (802.5), Metropolitan Area Networks (802.6), and Wireless LANs (802.11). The MAC sublayer works in conjunction with the Logical Link Control Layer of the IEEE model; at this higher level are defined specific LLC conventions such as frame format and addressing.

Medium Attachment Unit

A device used in a data station to couple the data terminal equipment (DTE) to the transmission medium.

Medium Dependent Interface

MDI-X. The physical components of a network interface which handle the electrical or optical connection to a cable. This includes the connector, transceivers, and other physical layer components. MDI-X refers to a physical connection which includes an internal crossover of the transmit and receive signals. All standard repeater ports are MDI-X and are often marked with just an X by the port. Some repeater ports are changeable to a DTE port. In this case, the port is changed to a MDI port for connection to a MDI-X port on another repeater. An example of a DTE port is the connection on a NIC.

Medium Earth Orbit

MEO. Medium (or Middle) Earth Orbit satellites orbit the earth at distances between LEOs and GEOs (Low Earth Orbit satellites and Geosynchronous Earth Orbit satellites). Because MEOs operate at heights greater than LEOs, they have larger footprints, or areas of coverage, so that fewer satellites are needed to provide complete coverage over the earth. The planned Odyssey system, which will have 12 satellites , is one MEO with complete world coverage. See also LEO, MEO, GEO and Geosynchronous.

Medium Frequency

MF. Radio frequencies from 300 KHz to 3000 KHz.

Medium Interface Connector

MIC. In LAN/MAN systems, the connector at the interface point between the bus interface unit and the terminal, termed the medium interface point.


Multiplex Equipment Engineering.

Meet-Me Conference

A teleconferencing term. Meet-Me Conferencing is an arrangement by which you can dial a specific, pre-determined telephone number and security access code to join a conference with other participants. You are automatically connected to the conference through a conference bridge. Conference participants may call in at a preset time or may be directed to do so by a conference coordinator . Meet-Me Conferences may be set up through a teleconferencing service provider, generally with the capability to conference thousands of participants. It also can be provided through a phone system, such as a PBX, key system or hybrid. Some phone systems restrict this to intercom circuits only. In almost all phone systems there is a maximum number of parties that can be connected in such conference at one time.

Meet-Me Intercom Conference

Dial a special number ("access code") and any telephone can join an intercom conference call.

Meet-Me Page

A feature which allows a person to answer an intercom page from any phone in the system.

Meet Point

A location at which the facilities of two carriers connect.

Meet-Point Billing

MPB. The process whereby two or more local exchange carriers jointly provide to a third party the transport element of a Switched Exchange Access Service to a local exchange carrier end office switch. Under this process, each local exchange carrier receives an appropriate share of the transport element revenues , as defined by their effective Exchange Access tariffs.

Meet-Point Billing Traffic

Refers to traffic that is subject to an effective Meet Point arrangement. Also see Meet-Point Billing.


A prefix meaning one million, also represented as an M. A megabit equals one million bits, Megahertz equals one million cycles per second, but Megabyte equals 1,048,576 bytes. See also Megabyte.


One million bits. See Bit.

Megabits per Second

A measurement of speed indicating that one million bits of information travel past one point in the circuit in one second.


MB. A combination of the Greek "mega," meaning "large," and the English "bite," meaning "a small amount of food." A unit of measurement for physical data storage on some storage device ” hard disk, optical disc, RAM memory, etc. The actual definition can be confusing, since there are two measurements. In the metric system, a megabyte is 1,000,000 bytes. In the computer world, things are measured in binary terms ” 1s and 0s. In binary terms, a megabyte is 2 to the 20th power, i.e., 1,048,576 bytes, which is the closest power of two to one million, .i.e. 1024 x 1024. Another way of stating Megabyte is Kilobyte (KB) multiplied by 1,024.A megabyte can be either a decimal (metric) megabyte or a binary megabyte, depending on the context. A decimal megabyte also is called a "millionsbyte" or a "miobyte," and is used to describe capacity in newer ROM BIOS drives. Binary megabytes are used to describe capacity in DOS FSISK, Windows 3.x File Manager, and CMOS setup in older ROM BIOS drives .

Here is a summary of sizes:

MB = Megabyte (2 to the 20th power)

GB = Gigabyte (2 to the 30th power)

TB = Terabyte (2 to the 40th power)

PB = Petabyte (2 to the 50th power)

EB = Exabyte (2 to the 60th power)

ZB = Zettabyte (2 to the 70th power)

YB = Yottabyte (2 to the 80th power)

One googolbyte equals 2 to the 100th power.


MEdia GAteway COntrol. Designated by the ITU-T as H.248, Megaco is a low- level device protocol for interfacing the circuit-switched PSTN (Public Switched Telephone Network) with various packet networks, primarily in support of packet voice. Megaco is an evolution of MGCP (Media Gateway Control Protocol) that expands the range of packet network options to include ATM, in addition to IP-based networks, and that includes simplified provisions for signaling and control for conferencing applications, including voice confer- encing and whiteboarding. Megaco links the Media Gateway (MG) and Media Gateway Controller (MGC) for intradomain remote control of connection-aware or session-aware devices, or endpoints. See also MGCP.


Million Floating point Operations Per Second. A measure of computing power usually associated with large computers. Mega means million. Also known as MFLOPS.


  1. MHz. A unit of frequency denoting one million Hz or one million cycles per second. See Bandwidth and Hertz.

  2. What the Vermonters' Guide to Computer Lingo says you get when you're not careful downloading, which it defines as taking firewood off the pickup truck.


Name for BellSouth's leased T-1 service.


Also known as a multiplex. A collection of different movie theaters in the same building, many playing different movies.


A large server. Possibly a Microsoft-created term. The idea is that people may keep much of their personal and professional information on large servers. The concept is that a person will be able tap into a large central database via the Web to get e-mail, personal schedules, news, weather updates and other information anywhere , anytime . See Server.


British Telecom's brand name for a service of 30 64-Kbps channels (i.e. E-1).


A resistance of 1,000,000 ohms. See Ohm.


Sudden and overwhelming media attention generated when an idea takes off globally. After he coined the term warchalking, London Web designer Matt Jones apologized for not keeping up with his blog "due to festivities arranged before my life got memenuked." This definition came from Wired Magazine.


In the 1930s, Vannevar Bush first wrote of the memex ” a pocket device that sounds very much like a wireless Palm ” in the 1930s. It didn't gain much attention until his seminal 1945 article, "As We May Think," published in the Atlantic Monthly. Here are his words from the article.

"Consider a future device for individual use, which is a sort of mechanized private file and library. It needs a name, and, to coin one at random, "memex" will do. A memex is a device in which an individual stores all his books, records, and communications, and which is mechanized so that it may be consulted with exceeding speed and flexibility. It is an enlarged intimate supplement to his memory. It consists of a desk, and while it can presumably be operated from a distance, it is primarily the piece of furniture at which he works. On the top are slanting translucent screens, on which material can be projected for convenient reading. There is a keyboard, and sets of buttons and levers. Otherwise it looks like an ordinary desk. In one end is the stored material. The matter of bulk is well taken care of by improved microfilm. Only a small part of the interior of the memex is devoted to storage, the rest to mechanism. Yet if the user inserted 5000 pages of material a day it would take him hundreds of years to fill the repository, so he can be profligate and enter material freely . Most of the memex contents are purchased on microfilm ready for insertion. Books of all sorts, pictures, current periodicals, newspapers, are thus obtained and dropped into place. Business correspondence takes the same path. And there is provision for direct entry. On the top of the memex is a transparent platen. On this are placed longhand notes, photographs, memoranda, all sorts of things. When one is in place, the depression of a lever causes it to be photographed onto the next blank space in a section of the memex film, dry photography being employed. There is, of course, provision for consultation of the record by the usual scheme of indexing. If the user wishes to consult a certain book, he taps its code on the keyboard, and the title page of the book promptly appears before him, projected onto one of his viewing positions . Frequently-used codes are mnemonic, so that he seldom consults his code book; but when he does, a single tap of a key projects it for his use. Moreover, he has supplemental levers. On deflecting one of these levers to the right he runs through the book before him, each page in turn being projected at a speed which just allows a recognizing glance at each. If he deflects it further to the right, he steps through the book 10 pages at a time; still further at 100 pages at a time. Deflection to the left gives him the same control backwards ." See also Internet.


  1. A telephone feature that enables the user to store a phone number for calling in the future. For example, while speaking to a Directory Assistance operator, you can put the number she gives you into memory, and then call that number by pushing one or two buttons.

  2. A call center term. A free form field used to store descriptive text or comments. The information in a memo field can be of any length and type.

Memorandum of Understanding

See MOU.


The part of a computer or sophisticated phone system which stores information or instructions for use. Memory comes in many variations. There is memory which is lost when the power is switched off. There is memory which is retained when power is turned off.

Memory Administration

MA. A set of functions that provide network system database updates, network system database integrity, network system database security and network system database backup and restoration. Definition from Bellcore (now Telcordia) in reference to its concept of the Advanced Intelligent Network.

Memory Board

An add-on board designed to increase a computer's RAM.

Memory Caching

A technology for increasing hardware performance by storing frequently used sequences of instructions in a memory cache separate from the computer's main memory where they can be more quickly accessed by the CPU.

Memory Call Service

A family of central office based voice messaging services from BellSouth.

Memory Cards

The memory card is a bunch of memory chips crammed into a small plastic cartridge about the size of a credit card and about three times the thickness . It is used in several palmtop computers. As this dictionary was being written, we were awaiting the release of a 16 megabyte memory card. In contrast to flash memory, a memory card requires small batteries, typically the same ones as used in watches . See Smart Card.

Memory Effect

The gradual shorting of a battery's useful life, caused by recharging before the battery is completely discharged. This is a real problem with nickel cadmium batteries, less of a problem with Nickel Hydride and even less of a problem with Lithium ion batteries.

Memory Interface

A PCMCIA definition. The memory interface is the default interface after power up, PCMCIA Hard Reset and PCMCIA Soft Reset for both PCMCIA cards and sockets. This interface supports memory operations as defined in PCMCIA Release 1.0 and later and is used by both Memory Cards and I/O Cards.

Memory Leak

In order to run, a computer program requests chunks of memory from the operating system for itself and for the data it needs. As the program runs, it may make additional requests for memory. If the program is well-written and, therefore, well- behaved, that memory will be explicitly released when the program is closed. A badly written program or a badly written operating system may not release that memory, leaving it in an unusable condition. This may be especially true if the program crashes (i.e., ends unexpectedly), which is common in poorly-written software. This phenomenon is known as a "memory leak," and it's not a good thing. The longer the software runs on your computer, the more and more of your computer memory it uses, and places in an unusable state. Eventually it uses up so much of your RAM memory, it starts using space on your hard drive. Soon, it runs out of hard disk space. Eventually your whole machine freezes . You are forced to reboot, losing all unsaved data in the process. There are two solutions: The first and most obvious is to reboot your computer, i.e. turn it off, wait ten seconds, then turn it on again. Some operating systems handle memory leak much better than others. Windows 2000 and Windows XP handle it much than Windows 95 and 98. There is another solution. See Garbage Collection.

Memory Map

An indication of what type of data is stored where in a computer's RAM memory.

Memory Moments

See Senior Moment.

Memory Protection

The structuring of memory resources in Novell's NetWare 4.0 that guards the NetWare server memory from corruption by NLMs. Memory protection allows you to run NLMs in a separate memory domain called the OS PROTECTED domain. Once you determine the NLM to be safe, you can load it into the OS domain, where it can run most efficiently .

Memory Reserve Power

The operating voltage, generally provided by a battery, which supplies power to the memory modules when your commercial power fails. You should check your memory reserve power before it's too late. You should test it even when you don't need it.

Memory Technology Driver

A PCMCIA card definition. A memory technology driver is a memory device specific software that interfaces to Card Services to mask the details of accessing different memory technologies.


See MicroElectroMechanical System.


See Metro Ethernet Network.


Options displayed on a computer terminal screen or spoken by a voice processing system. The user can choose what he wants done by simply choosing a menu option ” either typing it on the computer keyboard, hitting a touchtone on his phone or speaking a word or two. There are basically two ways of organizing computer or voice processing software ” menu-driven and non-menu driven. Menu-driven programs are easier to use but they can only present as many options as can be reasonably crammed on a screen or spoken in a few seconds. Non-menu driven screens allow more alternatives but are much more complex and frightening. It's the difference between receiving a bland "A" or "C" prompt on the screen ” as in MS-DOS and receiving a menu of "Press A if you want Word Processing," "Press B if you want Spread Sheet," etc. It's very easy to write menus in MSDOS using BATch files. See also Audio Menus and Prompts.

Menu Bar

call center term. The part of the menu system visible as a single row across the top of the display.


Middle (or Medium) Earth Orbiting satellite. MEOs operate much like LEOs (Low Earth Orbiting satellites systems), although in slightly higher orbits. MEOs generally operate at an altitude of around 10,000 kilometers. Continuous global communications services can be achieved with six to 12 satellites. MEOs are capable of supporting both voice and data services. Contrast with GEO, Geosynchronous and LEO. See also Medium Earth Orbit.


Multiplex Equipment Provisioning.


Merced is a 64-bit multichip module jointly developed by Intel with Hewlett- Packard Co. It extends the Intel architecture in both raw speed (one version will reach 600- MHz) and overall performance. Merced will be followed by the two-chip processor called Flagstaff in the year 2000. Flagstaff chips will be the first built using a process that creates much smaller 0.18-micron-wide circuits, which will enable Intel to build smaller and faster chips in greater volume. There will be two versions of Flagstaff, with a choice of 4 Mbytes or 8 Mbytes of secondary cache, according to writer, Tom Davey.

Merchant Silicon

Merchant Silicon is a special microprocessor chip, which is a non- ASIC, commercially available semiconductor chip.

Mercury-Wetted Relay

A relay or switch in which the movable contact of the device makes contact with a pool of mercury. Before solid-state devices, this was common technology for switching dry circuits. See also Dry Contact.

Merging Traffic

The telecommunications, cable, consumer electronic and media conglomerates all vying for access to the same markets. See Siliwood.


A Northern Telecom (now called Nortel) name for a family of PBXs.

Meridian Link

Meridian Link from Northern Telecom enables Meridian 1 Communication Systems (i.e. PBXs and ACDs) to exchange information with host computers and the application software that resides on those computers. This means that the application software can use information such as Automatic Number Identification (ANI) and Dialed Number Identification System (DNIS) to automatically perform a series of routines, such as record look-up.


Lines circling the earth from pole to pole which are used to measure distance (longitude) around the globe.

Meridional Ray

In fiber optics, a ray that passes through the optical axis of an optical fiber. This contrasts with a skew ray, which does not.


The successor to NSFNET, MERIT originally was a statewide IP network operated by the University of Michigan. It also was a substantial regional subnetwork (subnet) of the NSFNET and the Internet. MERIT provides access into the Internet through MAEs (Merit Access Exchanges) located in San Jose (MAE West) and Vienna, Virginia (MAE East); those points of access actually are provided in partnership with MFS Datanet. See MAE.


Most Economical Route Selection. A term used by GTE and some other PBX manufacturers to mean Least Cost Routing. See Least Cost Routing.


Network architecture in which each node has a dedicated connection to all other nodes.

Mesh Connectivity

A Wide Area Network (WAN) term for connectivity over a mesh network, wherein each site is directly connected with every other site. See Mesh Network for a much fuller explanation.

Mesh Network

A leased line network that provides a direct connection between each site and every other site. Through the use of intelligent internetworking devices, such as Nodal Multiplexers in a T-Carrier network, each transmission might be routed over an alternative path should the primary (direct) path between the two sites be either congested or in a state of failure. The advantages of mesh networking include high availability of efficient transmission links of high quality. Through the use of intelligent internetworking devices, network redundancy offers the advantage of network resiliency. The disadvantages of a full mesh include high cost, difficulty of configuration and reconfiguration, and long lead times associated with carrier provisioning. Mesh networks are relatively easy and inexpensive to configure where four or fewer sites must be interconnected ; the cost and complexity increase significantly where more than four sites are involved. As a result, large organizations increasingly tend to favor alternative solutions for voice and data. Such alternatives as Virtual Private Networks (VPNs), Frame Relay, SMDS and ATM offer performance comparable to leased mesh networks, but at lower cost, with greater flexibility of configuration, and without the long lead times.


The Greek prefix meaning the middle.


The relationship between two signals such that their corresponding significant instants occur at the same average rate.


  1. A sequence of characters used to convey information or data. In data communications, messages are usually in an agreed format with a heading which establishes the address to which the message will be sent and the text which is the actual message and maybe some information to signify the end of the message. A Northern Telecom Norstar definition: A message, which appears on the telephone display that informs the recipient to call the person who sent the message. Messages can only be sent within the Norstar system.

  2. The Layer 3 information in the OSI model that is passed between the CPE and SPCS for signaling.

  3. A SCSA definition. The transport container for SCSA requests, replies and events. Assumes a set of conventions for directing the delivery of the message to the proper entity, either a client or service provider. See also SCSA Message Protocol.

  4. A completed call, i.e., a communication in which conversation or exchange of information took place between the calling and called parties.

Message Alert

A cellular phone term, 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.

Message Alignment Indicator

In a signal message, data transmitted between the user part and the message transfer part to identify the boundaries of the signal message.

Message Backbone

A single format message transport system designed for the electronic mail and messaging needs of an entire corporation or enterprise.

Message Center

A centralized place within the corporation where messages are taken and (occasionally) delivered. Message centers are good if they are staffed with competent, motivated people and the various phones in the place have message waiting lights (like they do in hotels). If staffed by talented people, message centers work a lot better than the amateur message takers called secretaries and their part-time short-term replacements .

Message Circuit

A long distance telephone phone line used in furnishing regular long distance or toll service to the general public. The term is used to differentiate message circuits from circuits used for private line service.

Message Customer Record Information System

MCRIS. A system used by Verizon to receive and interpret central office switch usage records.

Message Detail Recording

See Call Detail Recording and Call Accounting Systems.

Message Format

The rules for placing information necessary for an electronic message. The format includes where the heading is and how long it will be as well as other control information.

Message Frame

A SCSA term. A data link layer frame the encapsulates control and signaling data transmitted on the SCbus or SCxbus Message Bus. The form of a Message Bus frame is fully compliant with ISO HDLC UI (Unnumbered Information) Frame specifications. See SCSA.

Message Handling Service

  1. MHS. Software whose primary function is the movement of messages between application programs. MHS was developed by Action Technologies. Novell acquired full marketing and development rights to MHS for NetWare based LANs (local area networks). Under MHS, each application sends messages to the server's \mhs\mail\snd directory. MHS delivers messages to an application by placing them in the application's assigned directory. MHS is most commonly used for e-mail (electronic mail). Various e-mail programs use the MHS format for exchanging e-mail messages. MHS was superseded by GroupWise.

  2. MHS also means the standard defined by ITU-T as X.400 and by ISO as Message- Oriented Text Interchange Standard (MOTIS). MHS is the X.400 family of services and protocols that provides the functions for global electronic-mail transfer among local mail systems.

Message Header

The header before a string of data containing information regarding the destination of the data, usually in a packet in X.25 format.

Message Identifier

MID. When the ATM Adaptation Layer segments higher layer information for transport in a sequence of ATM cells, the MID is a 10-bit field and is used to associate all the cells that carry segments from the same higher layer packet.

Message Integrity

The notion that a message has not been altered and is, therefore, true to its original intent (a.k.a. data integrity).

Message Management

A new term for managing all your voice mail, fax mail and electronic mail. The major concept is to join the control of the devices that produce voice, fax and e-mail through your desktop PC connected over your LAN. For example, you come into work in the morning, turn your PC on, and immediately see a screenful of messages ” one line per message. By clicking on that line with your mouse, your PC would pull up the application that will then let you read or hear your message. The benefit is that you can handle your messages faster and be more discriminating about which ones you pay most and least attention to.

Message Packet

A unit of information used in network communication. Messages sent between network devices (workstations, file servers, etc.) are formed into packets at the source device. The packets are reassembled, if necessary, into complete messages when they reach their destination. A message packet might contain a request for service, information on how to handle the request, and the data that will be serviced. An individual packet consists of headers and a data portion. Additional headers are appended to the data portion as the packet travels through the layers of the communication protocol. Any message that exceeds the maximum size is partitioned and carried as several packets. When the packet arrives at its destination, the headers are stripped off, the message delivered and the request serviced.

Message Rate

A method of billing local phone calls that varies from one place to another. Phone calls are billed as "message units." Message units are a combination of length of call and distance of the call. In a city like New York you might buy "basic" phone service and be entitled to 50 "message units." That may mean you can call the local pizza house for under 5 minutes 50 times. Or it may mean that you can call from Manhattan to the Bronx 25 times ” assuming each call is two message units.

Message Register Leads

Terminal equipment leads at the interface used solely for receiving dc message register pulses from a central office at a PBX so that message unit information normally recorded at the central office only is also recorded at the PBX.

Message Registration

A phone system feature that records the number of message units incurred by each phone. Useful in hotels which bill local calls by message units.

Message Retrieval

The ability of a fax machine to store material already transmitted so it can be retransmitted.

Message Signal Unit

Signal unit of CCS that carries a message corresponding to the information part or packet of the HDLC frame plus a message transfer part corresponding to the HDLC frame header.

Message Store

An X.400 electronic mail term: A staging point, similar to a post office, in which messages are temporarily held for later transmission to one or more recipients.

Message Switch

A message switch is another term for an electronic mail gateway, which is a LAN application that fetches messages from one electronic mail system, translates them to the format of another electronic mail system, and then sends them to the "post office" of that other system. The post office is the public entry point ” the place you put mail you want the other system to receive.

Message Switching

A technique for receiving a message, storing it for a while and then sending it on. Message switching is normally used when the desired recipient is not there. The message switch will keep attempting delivery, freeing the calling party to handle other work. Unlike voice phone calls no direct connection is made in message switching between the incoming and outgoing messages. Each message, like a Western Union telegram, contains a destination address and is recipient through intermediate nodes. Each node along the way receives the message, stores it briefly , and then passes it on to the next node. Message switching is a forerunner of what is now called packet switching. Only difference is that message switching had no fixed message length.

Message Switching Network

A public data communications network over which subscribers send primarily text messages to one another.

Message Telecommunications Service

MTS. The regulatory term for long distance or message toll voice service. Misnamed. Actually there's nothing "messagey" about this service. This is a 100% switched telephone service (which can, obviously, be used for voice, data, video or fax).

Message Telephone Service

MTS. Official designation for tariffed long-distance, or toll, telephone service. See Message Telecommunications Service.

Message Toll Voice Service

See Message Telecommunications Service.

Message Transfer

MT. The carriage of information between parties using computers as intermediaries. It is one aspect of message handling.

Message Transfer Agent

An X.400 electronic mail term: Software usually residing in a LAN server or host computer that moves messages between senders and recipients.

Message Transfer Part

MTP. The part of SS7 signaling node that is used to place formatted signaling messages into packets, strip formatted signaling messages from packets, and send or receive packets.

Message Unit

  1. The charge for one unit of local telephone service. How many message units you will find on your bill is a function of how many calls you made, how far the calls traveled, what time of the day or night you called and for how long you talked.

  2. In IBM Corp's Systems Network Architecture, the portion of the data within a message that is passed to, and processed by, a specific software layer.

Message Unit Detail

MUD. A service offered by local telephone companies in which they give you a report listing the phone number of all local calls made from each of your billing numbers. The billing number may be the main number for a PBX or the individual extensions if Centrex service is used. MUD reports are usually available to a telephone company customer at additional cost. MUD reports generally have to be requested in advance. Some telephone company central offices cannot generate MUD reports. When available, MUD reports may not be in machine processable form.

Message Waiting

A light on the phone or some letters or characters on the phone's display indicating there's a message waiting somewhere for the owner of the phone. That message might be with a special message center (as in a hotel or a larger company), with the operator or with a computer attached to the phone system or with someone else in the company. Message waiting lights are incredibly useful at hotels. It's amazing more companies don't use them also.

Message-To-Slave Directory Propagation

In electronic mail on a local area network, message-to-slave directory propagation is a way of updating user addresses where changes in the master post office are sent to the slaves, but changes in the slave post offices are not sent to the master.

Messages Roses

French term for pay telephone pornographic messages. What the English call phone sex lines.


One-to-one communication. Messaging comes in several flavors (not all implemented as yet), including text messaging, audio messaging and video messaging. See also Instant Messaging.

Messaging Application Programming Interface

MAPI. A set of calls used to add mail-enabled features to other Windows-based applications. See MAPI.

Messaging Enabled Applications

MEA. This term defined by the Electronic Messaging Association, Arlington, VA. Applications that directly access the messaging service as a way of addressing and transporting information to and from objects on a network. Messaging Enabled Applications differ from Mail Enabled Application because they do not require electronic mail to successfully navigate the network. They may or may not have their own directory and also have the ability to directly access Directory Services. For example: A student requests a class via electronic mail to the education system. The education system automatically schedules the student (this an electronic mail enabled application).

Messaging Middleware

Lets applications communicate and exchange data via asynchronous messages and queues.


  1. A piece of heavy metal cabling attached to a pole line to support aerial phone cable. See also Hard Cable and Messengered Cable.

  2. See Windows XP Real Time Communications.

Messengered Cable

Messengered cable is similar to jacketed cable, but includes an integral steel "messenger wire" to provide mechanical support. Messengered cable is intended for aerial installation without strand . See Hard Cable for a much bigger explanation.


Multibutton Electronic Telephone for an old phone system called AT&T Horizon.


Change, or transformation. From Greek.


In broadband ISDN, some future User-to-Network interfaces may be point-to-multipoint configurations. The devices on this interface may each generate signaling messages directed to the broadband (ATM) switch. In point-to-multipoint configurations, a separate, independent, virtual channel for signaling is required between the network and each of the devices on the multipoint interface, so the switch will always know who sent the message. The meta-signal channel is a pre-established management channel which will be used to establish the point-to-point signaling virtual circuits between the network and each of the individual devices on a multipoint interface. ( narrowband ISDN's Basic Interface uses a similar process on the D-channel called the TEI assignment.) The meta-signaling channel will operate on virtual circuit 1 within each virtual path. Meta- signaling is not required on point-to-point interfaces, because the switch is only communicating with one device! In those cases, the signaling protocol (q.93B) will operate on virtual 5.

Meta Tag

A meta tag is an optional HTML tag that is used to specify information about a Web document to search engines crawling the Internet. The Meta Tag appears in the <head> portion of a Web page. Search engines use "spiders" to index Web pages by reading the information contained within the meta tag's code. An HTML or Web page author uses these tags to help his or her page get noticed or "come up" when an Internet surfer queries a search engine for a particular key word or topic. The meta tag can also be used to specify an HTTP or URL address for the page to "jump" to after a certain amount of time. This is known as Client-Pull. This means a Web page author can control the amount of time a Web page is up on the screen as well as where the browser will go next. Here's the HTML syntax for search engine indexing:

 <HTML> <HEAD> <TITLE>Technology Investor Magazine</TITLE> <META NAME="keywords" CONTENT="Technology, eCommerce, Investing, Investor, Stocks,"> <META NAME="description" CONTENT="This is a magazine about investing in technology stocks."> </HEAD> <BODY></BODY> </HTML> Here's the HTML syntax for Client-Pull: <HTML> <HEAD> <TITLE></TITLE> <META HTTP-EQUIV="REFRESH" CONTENT="30;URL=gothere.html"> </HEAD> <BODY></BODY> </HTML> 

This code makes the Web page "refresh" or change to the URL specified in 30 seconds.


Stealing the contents of another site's HTML meta tag and using it on your web site because that will place your site higher in a search engine's results. In other words, when people go to find look for something relating to what you do, they will find your site faster than your competitor's.

Metal Oxide Varistor

Metal Oxide Varistor. A voltage dependent resistor which absorbs voltage and current surges and spikes. This low-cost, effective device can sustain large surges and switch in 1 to 5 nanoseconds. It is used as a surge protector and suppressor . It often the first electronic component that electrons coming in on an incoming phone line hit. Many trunk boards inside PBX are protected by MOVs. If the voltage or current is high, it will blow the MOV, thus protecting the remaining the far more valuable devices on the board.

Metal Tape

Recording tape coated with iron particles and noted for its wide dynamic range and wide frequency response.

Metallic Circuit

A circuit completely provided by metallic wire conductors, and not containing any carrier, radio or fiber and in which the ground or earth forms no part.

Metallic Voltage

A potential difference between metallic conductors, as opposed to a potential difference between metallic conductor and ground.


Metallization is necessary if composites are to be used in antenna applications. Antennas are mainly metallized with copper or gold. Composite systems that lend themselves to metallization are those epoxy and thermoplastic composites with Kevlar, glass or carbon fiber reinforcement.

Metallized Fiber

Basically metallized fiber is a fiber strand with a thin coating of metal all around it. The idea of metallized fiber is to cut down on the leakage of the light signal or signals being carried inside the fiber.


See Desktop Metaphor.


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

An ATM term. The standardized VCs that convey metasignaling information across a User-Network Interface (UNI).

Metcalfe's Law

Named after Robert N. Metcalfe. Metcalfe's Law states that the value of a network ” defined as its utility to a population ” is V=A*N*N+B*N+C where V is the value and N the number of users of a network. The value of a network grows with the square of the number of its users. Often, for small N, the COST of a network exceeds its VALUE. This means there is a critical mass phenomenon in networks. Therefore, small pilots of some networks might fail where a larger operational network might succeed wildly. It's tough getting them started, but then BAM! off they go. A simple example: One telephone is useless. Two telephones are better, but not much. Only when a good proportion of the population has a telephone does the network gain the power to change the society. Some people estimate that a totalitarian government cannot survive even one telephone per hundred people. Metcalfe's Law pertains most especially to computer networks, as Bob Metcalfe is the co- inventor of Ethernet, the first LAN (Local Area Network), which was standardized as 802.3. According to many observers, the Internet owes its extraordinary growth and impact to its ability to harness both Metcalfe's Law and Moore's Law (which says that computing power and capacity double every 18 months, while costs drop by half). See also Connectivity Law, Data Dialtone, Ethernet, and Moore's Law.

Meteor Burst Communications

Communications by radio signals reflected by ionized meteor trails.


  1. The metric unit of length, equivalent to 39.37 inches. An instrument for measuring quantities of length. According to the NIST (National Institute of Standards and Technology), the origins of the meter go back to the 18th century, when there were two definitions. Christian Huygens, an astronomer , proposed that a meter would be the length of a pendulum having a period of one second. That definition failed, as the force of gravity varies slightly over the surface of the earth, which affects the period of the pendulum. The successful definition was that of one ten-millionth of the length of the earth's meridian along a quadrant (one-fourth of the circumference of the earth). The French Academy of Sciences made this decision in 1791.

    The French, with typical French arrogance (unlike Americans, of course), therefore defined the meter as one ten-millionth of the length of the meridian from pole to equator, through Paris. Despite the fact that this measurement was off by a whopping 0.2 millimeters because of the flattening of the earth due to its rotation, this definition stuck. Over the years, the definition was refined considerably. According to the International System of Units (SI), the current definition of a meter is the length of the path traveled by light in a vacuum during a time interval of 1/299,792,458th of a second.

  2. A device which measures network traffic along some parameter, which typically is temporal (e.g., the duration of a connection or session), quantitative (e.g., number of data packets), or qualitative (e.g., the level of conformance of a packet or packet stream to a pre-defined traffic profile) in nature. The meter commonly will retain in memory traffic statistics based on those measurements, and upload them to a centralized network management or other support system on command.

Metered T-1

See Fractional T-1.

Metering Pulses

In virtually all foreign countries , periodic pulses are returned from the distant exchange to the exchange (central office) of the calling number. These pulses determine the cost of the call, local or long distance. Typically, all pulses cost the same. However, the farther you call, the quicker the pulses come. This system contrasts to the North American long distance billing scheme which typically charges a certain amount for the first minute ” no matter how much of the minute is actually used in conversation. After the first minute in the U.S., conversations are billed in one minute increments . Overseas pulses can be as short as three or four seconds (especially for international calls).

Newton[ap]s Telecom Dictionary
Newton[ap]s Telecom Dictionary
ISBN: 979387345
Year: 2004
Pages: 133 © 2008-2017.
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