(19)

(11)

EP 0 578 685 A1

(12)

(43) Date of publication: 19.01.1994 Bulletin 1994/03 (21) Application number: 92907532.0 (22) Date of filing: 01.04.1992

(51) International Patent Classification (IPC):  G01K 7/ 32( . ) G01R 33/ 44( . ) G01V 3/ 14( . ) G01N 24/ 00( . ) G01R 33/ 48( . ) (86) International application number: PCT/GB1992/000580 (87) International publication number: WO 1992/017794 (15.10.1992 Gazette 1992/26)

(84) Designated Contracting States: CH DE FR GB IT LI NL SE (30) Priority: 02.04.1991 GB 19910006789 05.03.1992 GB 19920004872 (60) Divisional application: 98121679.9 / 0928973 (71) Applicant: BRITISH TECHNOLOGY GROUP LIMITED London SE1 6BU (GB)	(72) Inventors: SMITH, John, Alec, Sydney London SW19 7QR (GB) SHAW, Julian, David Encinitas, CA 92024 (US) (74) Representative: Cozens, Paul Dennis  Mathys & Squire 100 Grays Inn Road London WC1X 8AL London WC1X 8AL (GB)