A conductor loop (antenna) is surrounded by a magnetic field. This field is continuously in an electromagnetic field. Beyond a certain distance, the electromagnetic field to separate from the antenna starts and propagates as an electromagnetic wave in space. At this distance – calculated as lambda / 2pi – Speak of the far-field. Until the removal of lambda / 2pi an inductive coupling between reader and transponder is possible. This area is referred to as the near field. Distance and near field are thus dependent on the distance.