Importance

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Abstract

In a private network where PBXs (1, 2) are connected through a primary rate interface (47, 48) to an ISDN network (45), one of the PBXs has routing data for virtual tie trunks for signaling and speech transmission, respectively, to be established via the ISDN to a distant PBX (2), and channel status data indicating their set-up or clear-down state according to time of day and calendar day. The stored data is periodically accessed, and depending on the contents of the channel status data, a call setup or clearing message is sent from the PBX (1) to the ISDN to set-up or clear-down the virtual tie trunks. On receipt of a response from the distant PBX, busy/idle status of the virtual tie trunks is changed according to the accessed channel status data. In response to a request from a user station, a path is established therefrom to the virtual speech tie trunk and a call setup message is sent direct to the distant PBX through the virtual signaling tie trunk.

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First Claim