n of a signal.) Data Encryption Standard. (Public standard encryp- District Switching Centre. (Part of the switching tion system from the American National Bureau of hierarchy in BT's network.) Standards.) Data Switching Exchange. (Part of packet switched Dispersive Fade Margin. (Used in microwave sys- network.) tem design.) Digital Speech Interpolation. (Method used in digi- Discrete Fourier Transform. tal speech transmission where the channel is acti- Directorates-General. (Departments of the Euro- vated only when speech is present.) pean Commission, usually referred to by numerals, Delta Sigma Modulation. (Digital signal modulation e.g. DGIV.) technique.) Direct Inward Dialling. (PABX feature allowing an Digital Signal Processing. external caller to connect to an extension without Digital Short-Range Radio. first going through an operator.) Digital Subscriber Signalling. (CCIT term for the Dual In Line package. (Integrated circuit packaging. N-ISDN access protocol.) Also known as DIP.) Direct Sequence Spread Spectrum. Deutsches Institue fur Normung. (Standardisation Data Service Unit. (Customer premise interface to body in Germany.) a digital line provided by a PTT.) Dual In line Package. (Integrated circuit packaging. DSX-1 Digital Signal Crossconnect. (Crossconnect used for Also known as DIL.) DS-1 signals.) Draft International Standard. Data Terminal Equipment. (User end of network Data Link Control. which connects to a DCE. Usually used in packet Data Link Service. switched networks.) Degraded Minutes. (Any one minute period with a Department of Trade and Industry. BER exceeding 106, as per CCITT G.821.) Diode Transistor Logic. (An older form of integrated Delta Modulation. (Digital signal modulation tech- circuit logic family.) nique.) Dual Tone Multi-Frequency. (Telephone signalling Direct Memory Access. system used with push button telephones.) Distributed Management Environment. (OSF.) Distributed Transaction Processing. Directory Number. (Of a customer in a switching Digital Termination System. (Local