Abstract: The invention relates to a device for detecting (CAPT) the presence of an object, that comprises at least one detection member (EA, EB) to which is associated a physical value that varies based on the environment in which said detection member (EA, EB) is located. The invention is characterised in that the physical value provides a variable reference level corresponding to the absence of an object and in that it further comprises a saving device (LOG IC) for saving, upon the emission of a low-frequency signal, a value of the reference level measured before the emission of said low-frequency signal.

Abstract: The invention relates to a device for detecting (CAPT) the presence of an object, that comprises at least one detection member (EA, EB) to which is associated a physical value that varies based on the environment in which said detection member (EA, EB) is located. The invention is characterised in that the physical value provides a variable reference level corresponding to the absence of an object and in that it further comprises a saving device (LOGIC) for saving, upon the emission of a low-frequency signal, a value of the reference level measured before the emission of said low-frequency signal.

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.