Siemens Aktiengesellschaft

Gerhard Lechner

Helmut Rau

Dirk Weiler

Eckard Sch&ouml;ttle

In accord therewith, at least one identification number (PIID) for identifying a private network (PISN) for access to a first private branch exchange (PBX,) to a subscriber (BS) who was registered and a mobile subscriber telephone number (MSISDN) that was sent into the public mobile radio telephone network (PLMN), is stored in the public mobile radio telephone network (PLMN). A routing number (PRIN) is offered in the mobile radio telephone network on the basis of the incoming mobile subscriber telephone number (MSISDN) and is checked with reference to the stored identification number (PIID) as to whether the call destination lies in the area of a private branch exchange (PBX,) of the same private network (PISN) to which the first private branch exchange (PBX,) belongs. When this is the case, routing information (RIN) that define the call destination are sent&mdash;after clear down of the call in the public mobile radio telephone network&mdash;to the first private branch exchange (PBX,) that subsequently sets up the connection to the call destination in the private network (PISN) on the basis of the received routing information (RIN).

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Vienna, Austria

Gerhard Lechner