AV/IT Glossary—27 Days of #AVabc—M


MDF—Short for main distribution frame, a cable rack that interconnects and manages the telecommunications wiring between itself and any number of IDFs. Unlike an IDF, which connects internal lines to the MDF, the MDF connects private or public lines coming into a building with the internal network. For example, an enterprise that encompasses a building with several floors may have one centralized MDF on the first floor and one IDF on each of the floors that is connected to the MDF.


M-Mega—A prefix for one million.

MAAP-Mini Architectural Adapter Plates—Compact mountable metal plates available in hundreds of models offering popular pass-through audio, video, phone, data, power, and control connectors. Active MAAPs are also available for power, control, and long distance signal transmission. Along with mounting options for maximum flexibility in placing connectors and controls within reach, these interchangeable components fit together to create an attractive and completely customizable A/V connectivity solution..

MAC-Media Access Control—The Media Access Control data communication protocol sub-layer provides addressing and channel access control mechanisms that make it possible for several terminals or network nodes to communicate within a multi-point network, typically a local area network (LAN). Access to the media may be spread out over time, or as in Ethernet, a mechanism is developed which allows random access, but provides a method for reattempting use of the media if a collision is experienced.

MAC Address-Media Access Control—A unique hardware number given to devices that connect to the Internet. When your computer or networking device (router, hub, interface, etc.) is connected to the Internet, a table (see “ARP”) relates the device’s IP address to its corresponding physical (MAC) address on the LAN. Also see "ARP."

Macrobending—A term that describes a macroscopic deviation of an optical fiber’s axis from a straight line due to bending, to the extent that optical loss occurs.

Magnetic Deflection—A method of altering the path of an object (such as an electronic beam) with a magnetic field. CRTs have magnetic coils that carry currents that create magnetic fields that control the path of the electron beam. Also called Magnetic focus.

Main Cross-Connect-MC—The central portion of a facility's backbone cabling that provides connectivity between equipment rooms, entrance facilities, horizontal cross-connects, and intermediate cross-connects. It usually consists of a distribution of patch panel.

Main Distribution Frame-MDF—A signal distribution frame that connects lines from the outside and lines on the inside.

Matched-Clad Optical Fiber—A singlemode optical fiber with a cladding of uniform refractive index, favored for being less susceptible to bending and splice losses.

Mathematically Lossless Compression—Allows the exact original data to be reconstructed from the compressed data. Data compacting in mathematically lossless processes is between 2:1 and 3:1. The term lossless is in contrast to lossy compression, which only allows an approximation of the original data to be reconstructed in exchange for better compression rates.

Matrix—An electronic device that accepts and distributes video (and/or audio) signals selected from multiple inputs and multiple outputs.

Matrix Decoder—Produces red, green, and blue from Y, R-Y, and B-Y.

Matrix Mixer—Similar to a matrix switcher, but with additional signal processing features, such as equalization (EQ), compression, and level/gain controls on the inputs and outputs.

Matrix Switcher—A means of selecting an input source and connecting it to one or more outputs. Like a regular switcher, but with multiple inputs and multiple outputs.

Matte White—A screen with a flat, dull surface for even reflection over wide viewing angles.

MATV—Master Antenna Television system; a television system where broadcast programs are received via a master antenna array and then distributed to users over coaxial cable or fiber optic cable.

MAV—The Extron acronym for matrix audio/video (switcher).

MB-Megabyte—A megabyte is actually 1,048,576 bytes, or roughly 1 million bytes.

MBC-Monitor Breakout Cable—A cable used to view a computer signal on a local monitor or terminal while routing the same signal to a new source, such as a data projector or monitor. An MBC provides three connections in the form of a “Y” cable, a “T” cable, or through a buffer in an enclosure box.

MBC Power Connector—Some of the Extron MBC high resolution buffers require power. The miniature power plug attached to some MBC cables plugs into the MBC power jack on the interface.

Mbps-Megabits Per Second—One million bits per second; a unit of measurement for data transmission.

Measurement of Audio Level—In the recording process, audio* level is a critical factor. If is too high, audio distortion* occurs. If it is too low, the signal-to-noise ratio* deteriorates. Thus precise measurement of audio level is essential during recording. A mechanical VU-meter or an electronic LED bar graph meter measures audio level. One of the most effective and fastest methods employs LEDs which change color according to signal level. When the audio level is too high or too low the lamp changes from green to red signaling that a problem has arisen.

Mechanical Splice—A splice between optical fibers accomplished by using a mechanical fixture and an index gel, rather than by thermal fusion.

Media Player—A software application used for the playback of audio and video files.

MediaLink™—Extron's MediaLink System is a family of easy-to-use and inexpensive products that work together to control A/V equipment in any small, one-projector classroom, boardroom, or auditorium.

Media Retrieval System—A system in a facility that allows for remote requests of content to be delivered from a headend location.

Megapixel—In digital imaging devices, megapixels define the resolution range when the number of pixels is equal to or greater than 1 million pixels. For example, SXGA is 1280 x 1024, or 1,310,720 pixels. This could be called a 1.3-megapixel device.

Mesecam—Middle East SECAM. A modified SECAM standard (B, G, D, and K) used in several countries in the Middle East.

Messenger Wire—A wire that is used as the supporting element of a suspended aerial cable. This wire may be an integral part of, or external to the cable.

MFTA-Multi-Frequency Termination Adapter—A single termination device with selectable frequencies for different applications.

MHz-Megahertz—One million hertz (cycles per second). Video bandwidth is measured in megahertz.

Microbend—A localized defect in an optical fiber at the core-cladding boundary, caused by mechanical stress that results in sharp, microscopic curvatures in the fiber.

Microbending Loss—Loss in an optical fiber due to sharp, microscopic curvatures, caused by imperfections in fiber coating, cabling, packaging, and installation, such as cinching fibers too tightly with a tie wrap.

Microdisplay—A rear-projection video display based on a fixed-pixel technology such as DLP, LCoS, or LCD.

Micron-μm—A micron, or a millionth (10-6) of a meter.

Microphone Amplication—A microphone is a device which converts sound waves to electrical impulses. High quality microphones usually generate a very low signal level. Low noise*, high fidelity pre-amplification is required to boost the output of a microphone before the signal reaches the main audio amplifier where it is processed as a regular audio signal. Pre-amplifying low level microphone signals may be achieved by precise matching of microphone impedance* and use of low noise electronic amplifying devices. Some microphones (mainly condenser type) need DC power in order to operate (phantom voltage) even before connecting to the amplification circuitry.

Microphone Impedance—In order to obtain the highest quality output signal from a microphone, its internal impedance should be matched to that of a pre-amplifier with exactly the same input impedance. Microphone impedance may vary from a few ohms to several megaohms.

Microphone Sensitivity—A specification that tells how much electrical energy is derived from a specified sound level input.

Mid-Entry—In fiber optics, the opening up of a fiber optic cable mid-span in order to access the fibers inside.

Mid-Range—The range of audio frequencies, 250 Hz to 5000 Hz, to which the human ear is most sensitive. Mid-range frequencies give sound its energy.

Military Tactical Cable—Heavy-duty cable designed for rugged installations in adverse environments.

Mill—A professional video format, utilizing a 1/2-inch metal particle videotape, using component video for recording and playback. The system is being further upgraded to use digital video signals.

Milli-m—Abbreviation for one one-thousandth. Example: 1 ms = 1 millisecond or 1/1000 second.

Millisecond (ms)—One onethousandth (0.001) of a second.

MIMO-Multiple Input Multiple Output antenna technology—In 802.11n. This technology promises to deliver up to 8x coverage and up to 6x speed of current 802.11g networks.

Mini Zipcord—A 2.5 mm diameter fiber optic cable with two jacketed fibers that can be separated.

MIPS-Million Instructions Per Second—The rate at which a computer executes instructions.

Mixer—Device for blending multiple audio sources.

M-JPEG—Motion JPEG or M-JPEG video compression applies the discrete cosine transform to each video frame independently. No temporal compression is applied in MJPEG and no frame interdependence exists as with MPEG compression. Each video frame is encoded as though it is an MPEG I-frame. Editing and random access are easily facilitated in product designs applying MJPEG.

Modal Bandwidth—In fiber optics, the bandwidth-length product, measured in MHz-km, of an optical fiber due to modal dispersion.

Modal Dispersion—In fiber optics, the dispersion of a single optical pulse into various modes which arrive at the light receiving device at different times. This limits the performance of multimode optical fiber.

Mode—A path for light within an optical fiber. Singlemode fiber comprises a single path, while in multimode fiber, there are multiple light paths.

Mode Field Diameter-MFD—A measure of the spot size or beam width of light propagating in a singlemode optical fiber. Usually this is 20% larger than the diameter of the core.

Mode Filter—A device that removes higher-order modes in multimode fiber.

Modem-Modulator/Demodulator—A device that puts information on a carrier signal and transmits it over a (phone) network. The same device receives such signals and demodulates, or separates the information from the carrier. A modem connects computers with other communication devices through ordinary phone lines.

Modular A/V Controller—An A/V controller built with interchangeable modules for upgrading to future technologies.

Modular Connector—Connector used with 4, 6, or 8 pins. Common modular connectors are RJ-11 and RJ-45.

Modulation—The process of adding an information signal to a carrier frequency to allow it to be transmitted. Thus, the carrier is modulated by the information signal, as in a modem.

Moiré—A pattern resulting from a combination of other patterns. In video, this is usually an undesirable pattern caused by an unwanted signal interfering with the desired signal. This may appear as a wavy motion.

Momentary Contact—A non-latching contact closure that lasts as long as it is held in place.

Momentary Switch—A switch that returns to its normal circuit condition when the actuating force is removed.

Monitor—(1) A TV that receives a video signal directly from an external source, such as a VCR, camera, or separate TV tuner to produce a high-quality picture. (2) A video display used with closed circuit TV equipment. (3) A device used to display computer text and graphics.

Monitor/Receiver—A TV having RF tuning circuits to receive broadcast signals for viewing.

Monoblock—A power amplifier with only one channel.

Monochrome—One color, usually interpreted as black and white. In computer CRTs, it is any single color with black.

Monochrome Composite Output—Provides a monochrome video output with combined horizontal and vertical sync for composite video with all the shades of the computer’s monochrome, 8-, 16-, or 64-color display adapter card output signal.

Monochrome Signal—A video signal having one color, usually a black and white signal, or sometimes the luma portion of a composite or component color signal.

Monophonic—Uses input from all microphones and relays them from the electronic control system to the loudspeakers using a single path or channel.

Morphing—A digital special effect carried out between two or more images, where the images are merged and transformed, one into the other. The images may be human faces or any other objects. The effect is widely used in video and in the movies, and requires much processing power.

Motorized Masking—A projection screen in which a motor-driven black drop moves into position over the screen to create different aspect ratios.

Motorized Screen—A projection screen that retracts by motor drive into a housing when not in use.

Motion Artifacts—Visible defects in a displayed image resulting from motion of objects within the image.

MP3—A perceptual coding format that reduces the number of bits required to represent a digital audio signal. Shorthand for MPEG-1 Audio Level 3.

MPEG-Moving Picture Experts Group—A standards committee under the auspices of the International Standards Organization working on algorithm standards that allow digital compression, storage and transmission of moving image information such as motion video, CD-quality audio, and control data at CD-ROM bandwidth. The MPEG algorithm provides inter-frame compression of video images and can have an effective compression rate of 100:1 to 200:1.

MPEG-1—Video compression. A video encoding method that reduces the bit rate needed to represent the video signal to 1.4Mbps. Provides poor picture quality.

MPEG-2—The second generation standard for video compression of audio and video applying the discrete cosine transform. The standard includes a combination of lossy video and audio compression methods which permit storage and transmission of movies using currently available storage media and transmission bandwidth. Commonly used for digital television transmission, DVD, and other similar equipment.

MPEG-4—A patented collection of methods defining compression of audio and visual (AV) digital data. Uses of MPEG-4 include compression of AV data for web (streaming media) and CD distribution, voice (telephone, videophone) and broadcast television applications. MPEG-4 absorbs many of the features of MPEG-1 and MPEG-2 and other related standards, adding new features such as (extended) VRML support for 3D rendering, object-oriented composite files (including audio, video and VRML objects), support for externally-specified Digital Rights Management and various types of interactivity.

MPEG-7—A content representation standard developed by the Motion Picture Experts Group for visual and scene motion recognition, for information search purposes.

MPLS-Multiprotocol Label Switching—A mechanism in high-performance telecommunications networks which directs and carries data from one network node to the next. MPLS makes it easy to create “virtual links” between distant nodes. It can encapsulate packets of various network protocols.

MTBF-Mean Time Between Failures—A basic measure of reliability for repairable items. It can be described as the number of hours that pass before a component, assembly, or system fails. Also (MTBR) Mean Time Between Repairs.

MTP—Extron’s acronym for it’s Mini Twisted Pair line of products.

MTS-Multichannel Television Sound—One of the first stereo sound systems developed for television. MTS consists of two independent singles each carrying a discrete channel. One channel provides stereo sound by providing left/right channel difference signals relative to transmitted mono audio track. The second carrier carries the Secondary Audio Program (SAP) which is used for a second language or for Descriptive Video, a descriptive commentary for the vision impaired.

MTU (Maximum Transfer Unit)—Each network has a maximum transfer unit or MTU, the maximum size for an Ethernet frame payload. Typically the MTU for a network is 1500 bytes. Routers break up data segments into two or more segments if the MTU is smaller than the payload in an Ethernet frame.

Multiburst—A video test signal composed of sinusoidal bursts of increasing frequencies, mainly used for frequency response testing and alignment of video equipment.

Multicast—Multicast addressing is a network technology for the delivery of information to a group of destinations simultaneously using the most efficient strategy to deliver the messages over each link of the network only once, creating copies only when the links to the multiple destinations split. A single stream is sent from the source to a group of recipients.

Multichannel Power Amplifier—A power amplifier with more than two channels, usually five or six.

Multichannel Sound—Sound reproduction using more than two channels feeding more than two loudspeakers.

Multidistribution—Simultaneous duplication of one signal source to many tapes. In the analog video world - during multi-distribution - a video processor* can be connected between the video source and the distribution amplifier* to enhance the copies or the monitor images.

Multimedia—Hardware and software that merge video, computer graphics and multi-channel sound in one interactive session. Multimedia can simultaneously display several live video scenes in small windows on one computer screen, and control the position and shape of the windows using a computer mouse and keyboard. Retrieval of music and other audio signals and of video scenes recorded on a computer hard disk, for educational, presentation and production purposes are only some of the applications made possible by multimedia, which creates a single computer-video-audio entertainment center. Nowadays the name is linked to everything related to graphics/video and audio production and entertainment.

Multimeter—A multipurpose test instrument with a number of different ranges for measuring current, voltage, and resistance.

Multimode Fiber-MMF—An optical fiber that allows for the propagation of more than one mode or light path. It is commonly used with LED light sources for shorter distance links.

Multi-Pass Transform—Multi-pass transforms return to a data set to carry out a process. Multi-pass transforms are often capable of supporting greater compression ratios, but use a greater amount of time to process the data.

Multipath—In FM-radio or television transmission, interference caused by the signal traveling two or more paths to travel between transmitter and receiver. Multipath is caused by mountains or buildings that reflect the radio or TV signals; the receiving antenna picks up the directly broadcast signal along with the signal after it has been delayed by the reflections. Multipath introduces audible distortion in FM tuners, and in television transmission is seen as “ghosting” in the picture. Multipath can cause HDTV receivers to pick up no usable signal.

Multiple Termination Plug-MTP—A small form factor, SFF plug for multiple fibers.

Multiplexing—The process used by the combiner to put together a number of modulated signals.

Multipoint—When more than two locations are connected for a videoconference using a bridge. Usually multipoint switching is done by video-follow-audio, such that the person speaking is automatically seen by the other conference site(s).

Multi-Purpose Transform—A multi-purpose transform is capable of converting more than one type of input format. The PURE3 codec is a multi-purpose transform in respect to its ability to process both video and computer graphic inputs which are different with respect to resolutions, color space, and color information.

Multi-Rate SDI—The capability to support multiple SMPTE serial digital interface standards, including SMPTE 424M (2.97 Gbps 3G-SDI), SMPTE 292M (1.485 Gbps HD-SDI), and SMPTE 259M (270 Mbps SDI).

Multiroom—A feature on some A/V products that lets you listen to two different sources in two different rooms.

Multiscan Monitor—A monitor (mainly for computer use) which synchronizes on different sync frequencies, allowing the use of different graphics formats on a single monitor, provided the graphics card used is able to do so. Multiscan monitors (sometimes called Multisync or Multifrequency monitors) are able to cope with many different graphics formats, and thus became the preferred choice of most PC users. Digital LCD monitors, can operate in many different sync frequencies, but the best image is obtained at a specific resolution and scan rate, known as its "native resolution".

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