made visible to a manager within describe a large exchange used within a cellular a network management system.) mobile system and connected to the PSTN.) Magnetic Ink Character Recognition. Maximum Usable Frequency. Master International Frequency Register. (Register of allocated international frequencies maintained by the IFRB.) Numerical Aperture. (Measure of a basic parameter Million Instructions Per Second. (Measure of a com- for fibre optic cables.) puter's processing speed.) Negative Acknowledgement. (In data transmission Management Information Tree. this is the message sent by the receiver to the sender Ministry of International Trade and Industry. to indicate that the previous message contained an (Japanese.) error, and requesting a re-send.) Minutes of Telecommunication Traffic. (Measure North American Numbering Plan. (Telephone num- used by telecommunication operators for tariffing bering scheme administered by Bellcore.) purposes.) North Atlantic Radio System. Multi-level Multi-Access protocol. (Multiple access National Aeronautics & Space Administration. technique.) (USA agency.) Man Machine Interface. (Another name for the North American Telecommunications Administra- human-computer interface or HCI.) tion. Monolithic Microwave Integrated Circuit. National Broadcasting Company. (USA.) Managed Object. National Bureau of Standards. (USA.) MODEM Modulator/Demodulator. Device for enabling digi- Network Control Layer. tal data to be send over analogue lines. Network Control Point. Metal Oxide Semiconductor. (A semiconductor National Cable Television Association. (USA trade technology.) organisation representing cable television carriers.) Acronyms 62/13 National Computer Users Forum. Open Area Test Site. (Used for EMC measure- National Destination Code. (Part of numbering sys- ments.) tem.) Optical Carrier. (SONET standard for optical sig- Network Element. nals, e.g. OC-1 at 51.84Mbit/s.) Network Element Function. Optical Character Recognition. (System which can Noise Equivalent Power. read characters by o