(19)

(11)

EP 0 273 918 A1

(12)

(43) Date of publication: 13.07.1988 Bulletin 1988/28 (21) Application number: 87901593.0 (22) Date of filing: 17.03.1987

(51) International Patent Classification (IPC):  G01D 5/ 353( . ) G01D 5/ 26( . ) G01B 11/ 00( . ) G01D 5/ 30( . ) (86) International application number: PCT/GB1987/000182 (87) International publication number: WO 1987/005689 (24.09.1987 Gazette 1987/21)

(84) Designated Contracting States: AT BE CH DE FR GB IT LI LU NL SE (30) Priority: 17.03.1986 GB 19860006550 (71) Applicant: PLESSEY OVERSEAS LIMITED Ilford Essex IG1 4AQ (GB)	(72) Inventors: DAKIN, John, Philip East Wellow Southampton Hants (GB) BATCHELLOR, Charles, Robert Romsey Hants (GB) (74) Representative: Nicholson, Ronald, et al  Intellectual Property Department The Plessey Company plc 2-60 Vicarage Lane Ilford Essex IG1 4AQ Ilford Essex IG1 4AQ (GB)