 plc Bell Northern Research Ian Corbett, BSc CEng MIEE Fred Harrison, BSc CEng MIEE BT Laboratories Cellnet Jim Costello Pat Hawker Telecommunications Consultant Formerly IBA Engineering Division David M Davidson D R Heath, BSc PhD CPhys MInstP Northern Telecom British Aerospace LM Davis Graham Hewitt NEC (UK) Ltd ISICAD (UK) Ltd Paul Dyer Mike Hillyard, BSc (Eng) CEng MIEE Northern Telecom BNR Europe Ltd T J Egginton, BEng (Sheffield University) Mark Holker, CEng FIEE MBIM Gandalf Digital Communications Ltd Hiltek Ltd Robert S Ferguson, BSc (Eng) J Hoolan Independent Consultant Dowty Communications Ltd William J Fitzgerald John Holdsworth University of Cambridge Newbridge Networks Ltd List of Contributors P J Howard Clive R Nightingale, Dip.EE CEng FIEE Telecommunications Consultant Formerly Chief Power and Building Services Engineer (BT) Fred Howett Malcolm A Nugent Northern Telecom GN Netcom (UK) Ltd Steve Hurst, BSc CEng Jean R Oliphant Bell Northern Research Rockwell International David L Jeanes Professor A D Olver, BSc PhD CEng FIEE FIEEE Bell Northern Research Queen Mary and Westfield College Edwin V Jones, BSc MSc PhD CEng MIEE S C Pascall, BSc PhD CEng MIEE University of Essex Commission of the European Communities Kanagendra, BTec MBA CDipAF KJell Persson Northern Telecom Europe Ericsson Ltd AC Keene, BSc CEng MIEE M Smouts Trend Communications Ltd Alcatel Bell Telephone Derek Kingaby, BTech CEng John Price Reichle De Massari (UK) Ltd Northern Telecom Europe J A Lane, DSc CEng FIEE FInstP J P Russell Radio Communications Agency Trend Communications Ltd Gary Law, BSc PhD R G Russell, BSc (Hons) CEng MIEE Anderson Consulting Hutchinson Microtel Ltd David Lockstone Michael J Simmonds Bell Northern Research Telindus Ltd C Lorek, BSc (Hons) AMIEE Eur Ing S F Smith, BSc (Eng) CEng FIEE South Midlands Communications Ltd Northern Telecom Europe M D Macleod, MA PhD MIEEE Carolyn Story, BSc (Hons) University of Cambridge Bell Northern Research P J Marnick, BSc (Hons) CEng MIEE R S Swain, CEng MIEE Hutchinson Micr