Glossary :: M-R
MARITIME SATELLITE SERVICE (MSS) – The satellite telecommunications service designed for communications between ships on the high seas and coastal Earth Stations which are connected to the switched telephone network.
MARK – A condition of a transmission line in which the current is flowing, equivalent to a binary 1.
MASTERGROUP – A frequency division multiplexing of 10 supergroups, totaling 600 telephone channels.
MASTERGROUP MULTIPLEX – A frequency division multiplexing of 3 mastergroups, totaling 1800 telephone channels.
MEAN TIME TO FAILURE – The average time for which a system operates without a fault.
MEAN TIME TO REPAIR (MTTR) – The average time it takes to correct a malfunction of a system.
MEASURED USE – A telecommunication service which charges by the actual time used by the customer.
MESH NETWORK – A network configuration in which each node is connected with every other one. Also called multipoint-to-multipoint.
MESSAGE SWITCHING – The telecommunications technique which receives, temporally stores, and then transmits a message as the network becomes available. It does not establish a connection between sender and receiver as in circuit switching.
METEOROLOGICAL SATELLITE SERVICE – An earth exploration satellite service for meteorological purpose.
MICROTERMINAL – A very small Earth station, often called a VSAT.
MICROWAVE – The portion of the electromagnetic spectrum above 1 GHz in frequency.
MOBLIE EARTH STATION – An earth station in the mobile satellite service intended to be used while in motion or during halts at unspecified points.
MOBLIE EARTH SERVICE – A radio communications services between mobile earth stations and one or more space stations, or between mobile earth station by means of one or more space stations. This service may also include feeder links necessary for its operation.
MODEM – A modulator combined with a demodulator.
MODULATION – A process of having a signal change the characteristic(s) of another (usually higher frequency) wave.
MOST ECONOMICAL ROUTING SCHEME – A system in which the network attempts to send a message first via the least expensive and so on until a connection is made.
MULTIPOINT – See Multipoint.
MULTIPLE ACCESS – Any technique which allows many users to access a given transmission facility.
MULTIPLEXER – A device which allows several signals to use the same communication channel.
MULTIPLEXING (MUX) – The combining of separate signals in a way that allows one communication channel to carry them all. Multiplexing may be done by dividing up space, frequency, time, or encoding technique.
MULTIPOINT DISTRIBUTION SERVICE – A one-way microwave radio service from a central hub to several receiving stations.
MULTIPOINT-TO-MULTIPOINT – A network configuration in which each node is connected with another. Also called a mesh network.
MULTI-SATELLITE LINKS – A radio link between a transmitting earth station and a receiving earth station through two or more satellites, without any intermediate earth station. A multisatellite link comprises one uplink, one or more satellite-to-satellite links and one downlink.
MUX – Multiplexer
NAK – Negative acknowledgement. A signal sent by a receiver to a transmitter to indicate that a message was received incorrectly.
NATIONAL TELECOMMUNICATIONS AND INFORMATION ADMINISTRATION (NTIA) – An agency of the U.S. Department of Commerce which manages government use of the electromagnetic spectrum and advises the government on telecommunications.
NOISE – Any unwanted contribution to a signal. May be natural or interference from other signals.
NOTICE OF INQUIRY – A FCC request for outside comments and proposal on some matter under consideration.
NOTICE OF PROPOSED RULEMAKING – A FCC request for comments on proposed regulations or on existing regulations proposed for change.
NUMBERING PLAN AREA – A scheme for numbering geological areas within the U.S. and Canada to allow direct dialing. Each 3-digit area code is of the form ABC, where A is any number, B is either 0 or 1, and C is any number.
OCCASIONAL-USE TRANSPONDER – A satellite transponder that is rented on a periodic, typically hourly, basis.
ONLINE – The mode of a system in which input to and output from a processing facility are communicated directly to and from the input and output devices.
OPEN SKIES POLICY – The 1971 FCC decision to allow private domestic services by communications satellites.
OPEN SYSTEMS INTERCONNECT REFERNCE MODEL (OSI) – A layered network architecture proposed by the ISO to coordinate telecommunications standards.
OPTICAL FIBER – See Fiber Optics.
ORBIT – The path, relative to a specified frame of reference, described by the center of mass of a satellite or other object in space subjected primarily to natural forces, mainly the force of gravity.
OSIREFERENCE MODEL – See Open System Interconnect Reference Model.
PACING – A technique for regulating the flow of information in a network.
PACKET – A unit of data to be transmitted over a packet network.
PACKET ASSEMBLY AND DISASSEMBLY (PAD) – The device or process of splitting a data message into packets for transmission over packet network.
PACKET SWITCH – A switch in a packet network that receives an incoming packet, examines the address, and forwards it to the next node it the network.
PACKET SWITCHING – The system of sending packets of data through a network with mesh topology. No physical path is established between sender and receiver, and various packets of one message may travel different paths to be reassembled at the receiving end.
PAL – Phase Alternation by Line; the color television broadcast standard for the U.K., West Germany, and many other nations.
PARALLEL TRANSMISSION – A system in which bits making up a character are sent simultaneously along several channels.
PARITY – An error detection technique in which an extra bit is added to the bits of an encoded character so that the character sent over a transmission line contains either an even number (even parity) or an odd number (odd parity) of 1’s.
PASSIVE SENSOR – A measuring instrument in the earth exploration satellite service or in the space research service by means of which information is obtained by reception of radio waves of natural origin.
PAY-PER-VIEW (PPV) – A system whereby a cable or DBS customer can order individual programs, such as films or sporting events, either immediately or for some specific later time.
PERIOD (OF A SATELLITE) – The time elapsing between two consecutive passages of a satellite through a characteristics point on its orbit.
PERSONAL EARTH STATION (PES) – M/Acom term for a microterminal.
PHASE MODULATION – The technique of changing the phase of a carrier wave in response to changes in state of a signal.
POINT-TO-POINT – A network in which two nodes are connected by a signal dedicated line not used by any other nodes.
POLORIZATION – A technique designed to increase the capacity of satellite transmission channels, whereby satellite transponder frequencies are reused by altering the shape or position of transmitted signals. An example is linear polarization, in which half the signals are beamed horizontally and half vertically without any resulting interference.
POLLING – A means of regulating communications on a channel by sequentially asking each node if it has any traffic to send.
PRIME FOCUS – The point where a lens or mirror brings collected waves to a focus. A type of satellite dish with the feed placed in front of the dish at the prime focus.
PRIMARY STATION – The station of a datalink that controls the transmission of data.
PRIVATE AUTOMATIC BRANCH EXCHANGE (PABX) – An automatic telephone exchange located on the user’s premises and connected to the public telephone network.
PRIVATE AUTOMATIC EXCHANGE (PAX) A dialup telephone exchange which provides private telephone service to an organization but is not connected to the public telephone network.
PRIVATE BRANCH EXCHANGE (PBX) – A manual or automatic telephone exchange located on the user’s premises connected to the public telephone network.
PROPAGATION DELAY – The time it takes for a signal to go from a sender to a receiver.
PROTECTED-USE TRANSPONDERS – A satellite transponder for which the common carrier guarantees that, should the transponder fail, transmission will be switched over to another transponder. Such a switch may preempt nonprotected transponder use on the second transponder.
PROTECTION RATIO (RF) – The minimum value of the wanted-to-unwanted signal ratio, usually expressed in decibels, at the receiver input, determined under specified conditions such that a specified reception quality of the wanted signal is achieved at the receiver output.
PROTOCOL – The standards and rules which govern the exchange of information between parts of a network.
PROTOCOL CONVERTER – A device which converts the protocol used by one device in a network to the protocol used by another device or another device or another network.
PTT – Post, Telephone, and Telegraph authority; the government body which, in most countries, controls the operation of all postal and telecommunications services.
PUBLIC DATA NETWORK – A public network designed for the transmission of data.
PUBLIC SWITCHED NETWORK – A circuit switched network available to the public.
PULSE AMPLITUDE MODULATION (PAM) – A modulation scheme whereby the strength of the modulating signal controls the amplitudes of a series of pulses.
PULSE CODE MODULATION (PCM) – A modulation scheme whereby the strenght of the modulating signal is expressed by a digital code.
PULSE MODULATION – Any modulation scheme in which the modulating signal is carried by a series of pulses. Includes pulse amplitude, pulse duration (pulse width), pulse position, and pulse code techniques.
RADIO FREQUENCY INTERFERENCE (RFI) – Interference with a receiver by a signal inadvertently generated at one near the wavelength that the receiver is attempting to receive. The Federal Communications Commission establishes RFI standards for electronic devices (such as video games ) to minimize this interface.
RADIO LOCATION – Radiodetermination used for purposes other than those of radio navigation.
RADIO NAVIAGATION SATELLITE SETVICE – A radiodetermination satellite service used for the purpose of radio navigation. This service may also include feeder links necessary for its operation.
RADIO SPECTRUM – The portion of the electromagnetic spectrum within which frequencies can be generated and detected by electronic currents. Signals on such frequencies can be propagated through space.
RADIOETERMINATION – The determination of the position, velocity and/or other characteristics of an object, or the obtaining of information relating to these parameters, by means of propagation properties of radio waves.
RADIOETERMINATION SATELLITE SERVICE (RDSS) – A satellite telecommunications service intended to provide navigation and message service to mobile users on land.
REALTIME – A term used to describe any system which operates such that input, processing, and output take place over a short period of time and without any long delays or storage of input or of intermediate or final results.
REFLECTING SATELLITE – A satellite intended to reflect radio communications signals.
REGIONAL ADMINISTRATIVE RADIO CONFERENCE (RARC) – Policymaking meetings of the ITU which consider issues for one or two regions.
REGIONAL CENTER – A Class 1 office in the telephone network, controlling sectional centers.
REGIONAL HOLDING COMPANY – The seven regional companies which own the local Bell operating companies (RBOC’s).
REPEATER – Any device which receives signal and repeats it to parts of a network farther down the line, usually amplified or restored to proper shape and intensity. On a communications satellite, a transponder.
RESPONSE TIME – The time it takes for a device to react to some input to it.
RING NETWORK – A network configuration in which the primary station polls each terminal in the network in order, to determine if the terminal has traffic for transmission.
ROUTING – The path, or the assignment of a path, for traffic through a network.
RS232C – A very popular physical level data communication standard, useful for distances up to about 50 feet and bit-rates up to about 20 kbps.