Patent ID: 7369036

Claim:
A method comprising information exchange between an interrogator device (DI) and a plurality of transponder devices (E 1 , E 2 ), each of which is equipped with a different binary identification code and is located in the magnetic field of the interrogator device, whereby the interrogator device transmits RF signals intended to interrogate the transponder devices on the presence of a bit or of a group of bits in their identification code and in which the transponder devices transmit a response signal indicating whether or not this bit or group of bits is present, characterized in that it consists, at the beginning of the interrogation sequence, of modifying the duration of the response signals and/or the form of the response signals (S r ) transmitted by each transponder device according to the ratio between the signal transmitted by the transponder device and the ambient electromagnetic noise, said method comprising: a) determining the signal-to-noise ratio between the signal transmitted by the transponder device and the ambient noise; b) determining, from this signal-to-noise ratio, a parameter relating to the duration of the response signal from the transponder device or a parameter relating to the waveform of the response signal from the transponder device: c) integrating this/these parameter(s) in the interrogation signal transmitted by the interrogator device; d) receiving the interrogation signal by the transponder device and recording this/these duration and/or form parameter(s); and e) transmitting a response signal by the transponder device during the duration recorded in d) and/or according to the form recorded in d).