Anropsomdirigeringssystem

摘要

An interface ( 52 ) is provided between a satellite telephone system ( 4 ) and a cellular telephone system ( 5 ) for allowing calls to a user's cellular telephone to be diverted to a satellite telephone ( 25 ) when the user is unable to use his cellular telephone, for example when on board an aeroplane ( 2 ) fitted with a satellite telephone system ( 20 ). The user inserts a card (which may be the SIM of his mobile phone, or a card compatible with existing satellite telephone equipment) into a suitable reader in the satellite telephone ( 20 ), which causes the satellite ground station's card verification system ( 42 ) to connect to a host cellular network ( 50 ). The host cellular network has an interface unit ( 52 ) which emulates the operation of a normal base station, so that the host cellular system ( 50 ) acts as if the mobile user's terminal is roaming on the host network, but is currently "busy". The interface ( 52 ) also resets the user's existing call diversion instructions so that when the host cellular system ( 5 ) receives a busy tone frome the base station emulator ( 52 ), it routes calls to the directory number of the terminal ( 20 ).