BXs, 34/12 SMDS, 42/26 Diffraction, Dispersion from the average, 1/4-5 DQDB MAN (Distributed Queue Double calculations, 6/16-17 Dispersion loss, optical fibres, 53/5-9 Bus MAN), 55/9 see also Electromagnetic waves; Space Distortion, Drop and insert rings/chains, SDH, waves attenuation, 10/9, 10/9-10 42/23-4 Digital Access Signalling System see delay, 10/9 DS (Data Store), APZ subsystem, harmonic, 10/9 32/16-17 Digital audio standards, 57/15 intermodulation, 10/9 DSBSC (Double SideBand Suppressed Digital cordless telecommunications, loss/frequency, 30/5, 30/9 Carrier) modulation, 18/4-6, 18/7, 19/9 49/3-13 non linear, 30/5, 30/9 DSI (Digital Speech Interpolation), 21/9 Digital exchanges, 29/10-11, 31/12-15, phase, 10/9 satellite use, 51/16 32/7-12 quantising, 30/5, 30/9 DSM (Delta Signal Modulation, 19/20 PABXs, 34/4 synchronisation, 10/10 DSN (Derived Services Network), 37/6 Digital filtering, PMR, 46/3 Distributed power plant, 24/11-12 DSN (Digital Switching Network), Digital hierarchy, TDM, 21/5-6 Distribution frames, 33/8 System 12, 32/7,32/8 Digital modulation see Modulation, Distribution, power supplies, 24/13 DSP (Digital Signal Processing), digital Distributions, arrival and departure FDM, 20/19 Digital network signalling, 43/8-11 queues, 3/8-9 modems, 39/6, 39/10 Digital services, transmission planning, Diurnal variation, earth's ionised layers, voice processing, 37/7 30/4, 30/10 DSSS (Direct Sequence Spread Digital signal processing, 2/10 Diversion of calls, Spectrum) coding, 14/12 Digital Signal Processing see DSP cellphones, 47/15 DTE (Data Terminal Equipment), packet Digital signalling, PMR, 46/10-11 PABXs, 34/12 switching, 40/12-13, 54/4, 54/5, 54/7 Digital signals, 10/5 DM (Degraded Minutes), 30/8, 61/9-10 DTI (Department of Trade and Industry) deterministic degredations, 28/5 DM (Delta Modulation), 19/19-20 UK, 22/21-2 eye diagrams, 28/5-6 DMS (Digital Multiplex System), DTM (Digital Trunk Module), System 12, fibre optics, 53/20-2 32/19-24 multilevel, 19/5 Centrex, 35/5 DTMF (Dual Tone Multi-Freque