About the author JOHN A. C. BINGHAM received a BSc from Imperial College, London, in 1956, and an MSEE from Stanford University in 1961. He has worked for twenty years in data transmission--primarily concerned with the telephone network. In 1972 at Vadic Corporation, he invented the VA3400, the first full-duplex 1200 bit/s modem, which ushered in a new era of high-speed, full-duplex data transmission. Until 1985, he was manager of the Advanced Development department of Racal-Vadic, a Milpitas, California subsidiary of Racal Electronics PLC, specializing in modems and multiplexers. He is a senior member of the IEEE, has written about thirty technical papers, and holds five U.S. patents. He is currently an independent consultant, interested in extending the principles of data transmission to other fields, such as magnetic recording.