Importance

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Abstract

A telecommunications system operable to connect terminal devices for exchange of data has control devices (ST, GST), an accessory control device (HS), and a memory (SP). The control devices effect addressed connections via hierarchical coupling fields (KF) to which terminal devices (T, PC, VP) and/or transmission lines (VL) are coupled, each by two user channels and one signalling channel. Routine transmissions to and from a telephone apparatus (T), computer (PC) or the like are effected by connection addressing codes transmitted on the signalling channel. For special functions or transmissions, a unique code is inserted in the signalling data, which causes the control device (GST, ST) to pass the signalling data to the accessory control device (HS). The accessory control device replaces the unique code with a connection addressing code if the terminal is authorized, and returns the signalling information to the control device, where it effects the desired connection. The memory (SP) stores data not used in switching, such as 'telephone book' listings, usage data, authorizations and the like. When a transmission involves a change in redundantly stored data in the memory and in the terminal device memories, the control devices and/or terminal devices locate and update all occurrences of the data. The system connects special functions to the exchange, without interfering with basic switching functions.

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First Claim