(19)

(11)

EP 0 273 921 A1

(12)

(43) Date of publication: 13.07.1988 Bulletin 1988/28 (21) Application number: 87902646.0 (22) Date of filing: 06.05.1987

(51) International Patent Classification (IPC):  G06F 17/ 14( . ) G06F 7/ 552( . ) (86) International application number: PCT/GB1987/000297 (87) International publication number: WO 1987/007053 (19.11.1987 Gazette 1987/25)

(84) Designated Contracting States: DE FR IT NL (30) Priority: 07.05.1986 GB 19860011124 (71) Applicants: GEC-MARCONI LIMITED Rochester, Kent ME1 2XX (GB) THE SECRETARY OF STATE FOR DEFENCE London SW1A 2HB (GB)	(72) Inventors: SPREADBURY, David, John Herts WD6 4LG (GB) CURTIS, Thomas, Edgar Weymouth Dorset DT4 0ED (GB) (74) Representative: Keppler, William Patrick  The General Electric Company, p.l.c. GEC Patent Department Waterhouse Lane Chelmsford, Essex CM1 2QX Chelmsford, Essex CM1 2QX (GB)