protocol for handling data.) 62/10 Glossary High bit rate Digital Subscriber Line. (Bellcore tech- International Frequency Registration Board. nical advisory for the transmission of high bit rate Interface Unit. (Module interfacing to a crosscon- data over twisted copper lines.) nect within the SDH.) High Definition Television. (New television trans- IGFET Insulated Gate Field Effect Transistor. (A semicon- mission standard.) ductor unipolar transistor with a high input imped- High Frequency. (Radio signal.) ance.) Hong Kong Telecommunications Authority. Intelligent Knowledge Based System. Home Location Register. (Database containing sub- Intermodulation. scriber information in mobile communications.) International Maritime Organisation. HOMUX Higher Order Multiplexer. International Mobile Subscriber Identity. (Personal Harmonically Related Carrier. (Carrier system used number associated with a PCN user's handset, and in cable television.) issued on his SIM. It is the number which the net- High Rupturing Capacity. (Usually refers to a type work uses to identify the mobile.) of electrical fuse used to break large values of cur- Improved Mobile Telephone System. (Analogue rent.) cellular radio standard, superseded by AMPS. North Hypothetical Reference Digital Section. (CCITT American origin.) G.921 for digital circuit measurements.) Intelligent Network. Horizontal Radiation Pattern. (Of an antenna.) INMARSAT International Maritime Satellite organisation. Health and Safety Executive. (UK) INTELSAT International Telecommunication Satellite organisa- Hertz. (Measure of frequency. One Hertz is equal to tion. a frequency of one cycle per second.) INTUG International Telecommunications Users' Group. International Organisation. Input/output. (Usually refers to the input and output International Alphabet 2. (Code used in a teleprinter, ports of an equipment, such as a computer.) also called the Murray code.) Indian Ocean Region. International Alphabet 5. (International standard al- Internet Protocol. phanumeric code, which