(19)

(11)

EP 0 416 005 A1

(12)

(43) Date of publication: 13.03.1991 Bulletin 1991/11 (21) Application number: 89906383.0 (22) Date of filing: 18.05.1989

(51) International Patent Classification (IPC):  G02F 1/ 035( . ) G02F 1/ 05( . ) G02F 1/ 01( . ) G02F 1/ 21( . ) (86) International application number: PCT/GB1989/000539 (87) International publication number: WO 1989/011675 (30.11.1989 Gazette 1989/28)

(84) Designated Contracting States: AT BE CH DE FR GB IT LI LU NL SE (30) Priority: 18.05.1988 GB 19880011689 (71) Applicant: BT&D TECHNOLOGIES LIMITED Ipswich, Suffolk IP1 5PB (GB)	(72) Inventor: SHAW, Robert, Norman Ipswich Suffolk IP10 0XH (GB) (74) Representative: Roberts, Simon Christopher  BRITISH TELECOM Intellectual Property Unit 13th Floor 151, Gower Street London, WC1E 6BA London, WC1E 6BA (GB)