Abstract: The invention relates to an access key (1) for unlocking a motor vehicle, comprising:—a communication interface configured so as to communicate according to an NFC protocol;—a support containing data constituting service provision rights,:—a monitoring circuit (111) able to process a transaction by way of said communication interface (112) on the basis of said data constituting the service provision rights; characterized in that it comprises a housing (106) for receiving a support containing data constituting service provision rights of removable type (2), and in that it comprises a read and/or write interface (113) in the removable support placed in the housing, the monitoring circuit (111) being configured so as to allow an exchange of data between the communication interface and the read/write interface.

Abstract: The invention relates to a signal transmission/reception device (DER) which can cooperate with an antenna device (A) capable of emitting a magnetic field. The invention is characterized in that the device (DER) comprises the following elements for transmission, namely: a power stage (P) for sending a symmetrical square-wave voltage signal (U0) to the input of the antenna device (A) in order to supply same with a current that can be used to generate the emitted magnetic field; and a current measuring stage (C) for measuring the current circulating in the antenna device (A). The invention is suitable for motor vehicles.

Abstract: The invention relates to a signal transmission/reception device (DER) which can cooperate with an antenna device (A) capable of emitting a magnetic field. The invention is characterised in that the device (DER) comprises the following elements for transmission, namely: a power stage (P) for sending a symmetrical square-wave voltage signal (U0) to the input of the antenna device (A) in order to supply same with a current that can be used to generate the emitted magnetic field; and a current measuring stage (C) for measuring the current circulating in the antenna device (A). The invention is suitable for motor vehicles.

Abstract: The invention relates to a method for detecting an identification object in an area (ZO) around an antenna device. The invention is characterised in that it comprises the following steps in which: a calibration signal (S_CAL) is emitted in the direction of the antenna device in order to determine a control power (PR); a functional signal (S_FONC) corresponding to the control power (PR) is emitted in the direction of the antenna device, such that the antenna device emits a pre-determined magnetic field; the magnetic field (Br) received by the identification object, corresponding to the emitted magnetic field, is measured and compared with a nominal magnetic field (B0); and, depending on the result of said comparison, it is determined if the identification object is located inside the area (ZO) around the antenna device. The invention is suitable for motor vehicles.