(19)

(11)

EP 0 452 450 A1

(12)

(43) Date of publication: 23.10.1991 Bulletin 1991/43 (21) Application number: 90916146.0 (22) Date of filing: 02.11.1990

(51) International Patent Classification (IPC):  H03M 1/ 20( . ) H03M 3/ 04( . ) H03M 3/ 02( . ) (86) International application number: PCT/GB1990/001686 (87) International publication number: WO 1991/007017 (16.05.1991 Gazette 1991/11)

(84) Designated Contracting States: DE FR IT NL (30) Priority: 06.11.1989 GB 19890025027 (71) Applicant: PLESSEY OVERSEAS LIMITED Ilford Essex IG1 4AQ (GB)	(72) Inventor: LESLIE, Thomas Coutts Kislingbury, Northampton NN7 4AU (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)