Importance

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Abstract

The invention relates to a method for call establishment, wherein the home location register (HLR) of a cellular radio system stores information on whether a subscriber (CPP) is located within the service area of its home private branch exchange (PBX), the call to the subscriber is routed to a first mobile services switching center (GMSC), the first mobile services switching center requests (101) the home location register (HLR) to provide routing information of the subscriber, if the subscriber (CPP) is located within the service area of its home private branch exchange, the home location register sends (202) to the first mobile services switching center for comparison a roaming number having a certain correspondence with the telephone number of the subscriber, if said correspondence between the roaming number and the telephone number of the subscriber exists, the first mobile services switching center sends (203) to a second mobile services switching center (MSC) an indication of the fact that a call is to be routed to the subscriber and that the subscriber is located within the service area of its home private branch exchange (PBX), the second mobile services switching center (MSC) does not perform the mobility management functions pertaining to normal connection establishment in the system and sends (204) a connection establishment request to the private branch exchange of the home location area of the subscriber, which performs the necessary mobility management functions (215, 216, 217, 218) and establishes (119) a connection between the subscriber (CPP) and the second mobile services switching center.

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First Claim