Book excerpt: The Focal Illustrated dictionary of Telecommunications is an invaluable resource for anyone studying, entering, or already working in the telecommunications industry. * Written by experts with specialist knowledge. * Contains essential data for on-the-job use. * Includes over 6,000 terms, definitions and acronyms. * Has over 350 line drawings. * The most comprehensive reference source of this nature. A Technical Manager for Nortel Networks, Fraidoon Mazda has held various senior technical posts within the electronics and telecommunications industries. He is editor of the Telcommunications Engi.