(19)

(11)

EP 0 394 425 A1

(12)

(43) Date of publication: 31.10.1990 Bulletin 1990/44 (21) Application number: 89912268.0 (22) Date of filing: 26.10.1989

(51) International Patent Classification (IPC):  G01S 13/ 91( . ) (86) International application number: PCT/GB1989/001275 (87) International publication number: WO 1990/004795 (03.05.1990 Gazette 1990/10)

(84) Designated Contracting States: BE DE FR GB IT NL SE (30) Priority: 26.10.1988 GB 19880025106 (71) Applicant: THE MARCONI COMPANY LIMITED Stanmore Middlesex HA7 4LY (GB)	(72) Inventor: JONES, Michael, Arthur Radlett Hertfordshire (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)