(19)

(11)

EP 0 478 615 A1

(12)

(43) Date of publication: 08.04.1992 Bulletin 1992/15 (21) Application number: 90909155.0 (22) Date of filing: 15.06.1990

(51) International Patent Classification (IPC):  H04S( . ) H04M 3/ 56( . ) H04H 20/ 88( . ) H04S 1/ 00( . ) (86) International application number: PCT/GB1990/000928 (87) International publication number: WO 1990/016136 (27.12.1990 Gazette 1990/29)

(84) Designated Contracting States: AT BE CH DE DK ES FR GB IT LI LU NL SE (30) Priority: 15.06.1989 GB 19890013758 (71) Applicant: BRITISH TELECOMMUNICATIONS public limited company London WC1E 6BA (GB)	(72) Inventors: HOLT, Christopher Ellis Woodbridge, Suffolk IP12 1QJ (GB) MUNDAY, Edward Ipswich, Suffolk IP4 3PA (GB) CHEETHAM, Barry Michael George Liverpool L19 9BQ (GB) (74) Representative: Lloyd, Barry George William, et al  Intellectual Property Unit British Telecom Room 1304 151 Gower Street London WC1E 6BA London WC1E 6BA (GB)