Passive access authorization system unauthorized access avoiding method for motor vehicle, involves carrying out question-answer dialog with interrogation and response field intensities modified relative to another set of intensities

摘要

The method involves transmitting an interrogation signal (20) with an intensity (Fc1) of an interrogation transmission field via a vehicle side transmission-reception installation (14) towards a transponder (22) during a question-answer dialog. A response signal (28) with an intensity (Fr1) of a response transmission field is transmitted from the transponder towards the installation. Another question-answer dialog is carried out with interrogation and response transmission field intensities which are modified relative to the intensities (Fc1, Fr1).