Dynamic Non-Hierarchical Depolarisation, due to ice crystals, 6/20 jitter, 28/13-16 Routing, 5/11-12 DEPSK (Differentially Encoded Pulse noise, 28/3-4 DNIC (Data Network Identification Code Modulation), 19/10 pair cables for, 15/5 Code), 29/15 Design, software, 25/3-4, 25/5-8 switching systems, 31/8, 31/12-15 Dolby TM sound system, 8/15 Detectors, telephone networks, 29/10-12, 44/13 Domains, optical fibre signals, 53/14-21 wave shaping, 28/4-5 continuous and discrete, 2/7 photometry, 7/3 Dimensioning, for grade of service, time and frequency, 10/7 Deterministic channels, 4/7 29/16-19 Doppler effects, Deterministic signals, 10/7 DIN (Deutsche Institut fur Normung), ionosphere, 9/6-7 Developing countries, 22/21 sound, 8/4 telecommunications industry, 11/12 Dipoles, radiation from see Radiation DOTAC (Department of Transport and Deviation from the average, 1/4 Dirac delta function, 2/16 Communications) Canada, 22/26 Direct Dial In see DDI DFB (Distributed Feedback lasers), 53/11 Double current signalling, 34/8 DFM (Dispersive Fade Margin), Directives, EEC, 11/8 DPCM (Differential Pulse Code millimetre systems, 50/9-10 Directivity, antenna, 6/11 Modulation), 19/17-19 DFSK (Differential Frequency Shift Director equipment, telephone exchanges, information theory, 4/12 31/10, 31/11 Keyed) modulation, 52/6 video transmissions, 57/11, 57/14, DFT (Discrete Fourier Transform), 2/8-9, Directory services, EDI, 38/6 57/24-5 Dirichlet condition, 2/4 2/10, 20/19 DPN-100 packet switching, 54/15 Dirichlet kernal, 2/16 DG XIII (Directorate General XIII) of DPNSS (Digital Private Network Discontinuities in a medium, 6/4 EEC, 22/15 Signalling System), 34/5, 34/9-10, 37/7 Discrete channels with memory, 4/9-11 ISDN, 44/12 Diagnostics, modems, 39/12 Discrete domain, 2/6 DPSK (Differential Phase Shift Keying), Dial, telephone, 31/5 Discrete memoryless channels, 4/6-9 19/9-10 Dibit phase shift keying, modems, 39/4 Discrete sequences, sampling, 2/7 DQDB (Distributed Queue Double Bus), Diesel driven supplies, 24/4 Discriminating ringing, PA