Patent ID: 8174356

Claim:
An access control system comprising at least one access lane which extends in an access direction and is equipped with a plurality of antenna coils juxtaposed in pairs and lined up in the access direction wherein said pairs comprise at least first and second pairs of said antenna coils, said pairs of antenna coils being controlled by reading means adapted to read data from a user-carried transponder, which indicates an access privilege of the user, and said reading means having a transponder coil for coupling with said antenna coils, and said access control system comprising a person detector detecting a user in said access lane in a read transaction and a blocking system which in a basic condition deblocks the access lane allowing passage therethrough by a user and is operable to a blocking condition to block said access lane only in case said person detector detects a user in the read transaction and said reading means detects an invalid access privilege, said blocking system configured to be actuated in dependence on the valid or invalid reading of the access privilege by means of said first pair of antenna coils and/or said second pair of antenna coils, characterized in that the juxtaposed antenna coils of each said pair being excited simultaneously but alternatingly in an in-phase or an oppositely phased operating mode, in that the transponder carried by a user being read by upholding the operating mode which results in the detection of said transponder until the read transaction completes reading of the data from the transponder and the read transaction is terminated, in that said antenna coils each generate an RF field having RF field lines which induce in said transponder coil a voltage to supply power to data storage means in said transponder storing said data and for the transmission of the data between said reading means and said transponder, and in that in the in-phase mode of operation of the antenna coils of one of said pairs of said antenna coils, and with a major surface of said transponder coil being disposed so as to extend along said access direction of said access lane, the power intake of said transponder is maximum whereas in the oppositely phased mode of operation, and with the major surface of transponder coil transverse to said access direction, said transponder coil has a maximum of field lines of said RF field passing therethrough.