The invention relates to a device and a method for recognizing call numbers in order to establish a connection from a line-switched network to a packet-switched network. Said device comprises a unit (1) for detecting a selected string of digits as a selected call number (TNe), a unit (2) for storing a plurality of authorized call numbers (TNx), a comparator unit (3) for comparing the selected call number (Tne) to the plurality of stored call numbers (TNx), and a unit (4) for converting the selected call number into an associated IP address (IP-A) as soon as the comparator unit (3) detects that the selected call number (TNe) matches one of the stored call numbers (TNx).