(19)

(11)

EP 0 551 484 A1

(12)

(43) Date of publication: 21.07.1993 Bulletin 1993/29 (21) Application number: 92916661.0 (22) Date of filing: 03.08.1992

(51) International Patent Classification (IPC):  H04Q 3/ 52( . ) H04Q 11/ 00( . ) H04L 12/ 56( . ) (86) International application number: PCT/GB1992/001439 (87) International publication number: WO 1993/003557 (18.02.1993 Gazette 1993/05)

(84) Designated Contracting States: DE ES FR IT SE (30) Priority: 02.08.1991 GB 19910167502 (71) Applicant: GPT LIMITED Coventry, CV3 1HJ (GB)	(72) Inventors: JEFFREY, Mark, Timothy 71 Jubilee Road Wimborne Dorset BH21 3NH (GB) PROCTOR, Richard, John 28 Diprose Road Wimborne Dorset BH21 3QY (GB) DUTHIE, Peter, John Northampton NN1 5QT (GB) (74) Representative: Branfield, Henry Anthony  The General Electric Company, p.l.c. GEC Patent Department Waterhouse Lane Chelmsford, Essex CM1 2QX Chelmsford, Essex CM1 2QX (GB)