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Priority claimed from GB878720389Aexternal-prioritypatent/GB8720389D0/en
Priority claimed from GB878721667Aexternal-prioritypatent/GB8721667D0/en
Application filed by British TelecommfiledCriticalBritish Telecomm
Priority claimed from EP88307978Aexternal-prioritypatent/EP0307122B1/en
Application grantedgrantedCritical
Publication of ATE75069T1publicationCriticalpatent/ATE75069T1/en