(19)

(11)

EP 0 403 547 A1

(12)

(43) Date of publication: 27.12.1990 Bulletin 1990/52 (21) Application number: 89903766.0 (22) Date of filing: 03.03.1989

(51) International Patent Classification (IPC):  G01R 31/ 02( . ) (86) International application number: PCT/GB1989/000208 (87) International publication number: WO 1989/008850 (21.09.1989 Gazette 1989/23)

(84) Designated Contracting States: AT BE CH DE FR GB IT LI LU NL SE (30) Priority: 08.03.1988 GB 19880005459 (71) Applicant: NETWORK SYSTEMS BUILDERS LIMITED Stanmore, Middlesex HA7 4DW (GB)	(72) Inventor: TODOR, Louis Thames Street London SE10 9DL (GB) (74) Representative: Weston, Robert Dale  c/o PHILLIPS & LEIGH 7 Staple Inn High Holborn London WC1V 7QF London WC1V 7QF (GB)