(19)

(11)

EP 0 438 406 A1

(12)

(43) Date of publication: 31.07.1991 Bulletin 1991/31 (21) Application number: 89904836.0 (22) Date of filing: 13.04.1989

(51) International Patent Classification (IPC):  H04M 17/ 02( . ) (86) International application number: PCT/GB1989/000379 (87) International publication number: WO 1989/010035 (19.10.1989 Gazette 1989/25)

(84) Designated Contracting States: AT BE CH DE FR GB IT LI LU NL SE (30) Priority: 13.04.1988 GB 19880008716 (71) Applicant: TETREL LIMITED Llantrisant, Mid Glamorgan CF7 8LF (GB)	(72) Inventors: DOCHERTY, Brian Gerard Sketty, Swansea (GB) CHURCHMAN, James Llysworney, South Glamorgan (GB) (74) Representative: Beresford, Keith Denis Lewis, et al  BERESFORD & Co. 2-5 Warwick Court High Holborn London WC1R 5DJ London WC1R 5DJ (GB)