from the centre of the turns an important parameter to obtain an efficient reading is that the value of the component h must have a value greater than or equal to a threshold value h 1 the latter determining the minimum distance to be maintained between the reader and the smart card assuming that this distance is 5 cm that is to say a convenient distance to take the reading the threshold value h 1 corresponds to the horizontal straight line shown in fig4 as we can see the value h 1 is respected over a large interval l that extends on either side of the large turn 26 on the other hand in the absence of the small turn the value h 1 will be reached only over an interval 1 which will not provide a sufficiently efficient reading while the turns may have a rectangular shape while remaining concentric for the implementation of the invention it turns out that the circular shape is the one that suits best to obtain good reading efficiency with rectangular turns the operator must maintain the handle of the reader in a position parallel to the smart card on the other hand with turns having a circular shape and thus being radially symmetrical it is obvious that the position of the reader handle does not make much of a difference for the reading as even if the handle is not parallel to the card the circular turns always produce the same electromagnetic field lines to obtain the best efficiency possible it is important that the ratio between the diameter of the large turn and the diameter of the small turn remains.