(19)

(11)

EP 0 413 803 A1

(12)

(43) Date of publication: 27.02.1991 Bulletin 1991/09 (21) Application number: 90904394.0 (22) Date of filing: 01.03.1990

(51) International Patent Classification (IPC):  G08B 13/ 14( . ) G08B 21/ 24( . ) G08B 13/ 26( . ) (86) International application number: PCT/GB1990/000321 (87) International publication number: WO 1990/010280 (07.09.1990 Gazette 1990/21)

(84) Designated Contracting States: AT BE CH DE DK ES FR IT LI LU NL SE (30) Priority: 01.03.1989 GB 19890004690 (71) Applicant: MARCONI ELECTRONIC DEVICES LIMITED Lincoln LN6 3LF (GB)	(72) Inventors: HARDEN, Paul Wiltshire SN3 6ND (GB) GREEN, Paul, Michael Wiltshire SN2 1DH (GB) (74) Representative: Hoste, Colin Francis  The General Electric Company p.l.c. GEC Patent Department Waterhouse Lane Chelmsford, Essex CM1 2QX Chelmsford, Essex CM1 2QX (GB)