(19)

(11)

EP 0 500 645 A1

(12)

(43) Date of publication: 02.09.1992 Bulletin 1992/36 (21) Application number: 90916516.0 (22) Date of filing: 13.11.1990

(51) International Patent Classification (IPC):  H03F 3/ 34( . ) H03F 3/ 347( . ) H03F 1/ 30( . ) H03F 3/ 45( . ) (86) International application number: PCT/GB1990/001745 (87) International publication number: WO 1991/007815 (30.05.1991 Gazette 1991/12)

(84) Designated Contracting States: DE FR GB IT SE (30) Priority: 13.11.1989 GB 19890025577 13.11.1989 GB 19890025579 08.10.1990 GB 19900021802 (71) Applicant: BRITISH TECHNOLOGY GROUP LTD London SE1 6BU (GB)	(72) Inventor: BINNS, John Philip Lincoln Cuckfield, West Sussex RH17 5LR (GB) (74) Representative: Gaskin, John Shield  Patents Department British Technology Group Ltd 101 Newington Causeway London SE1 6BU London SE1 6BU (GB)