Data and/or command signal transmission device, the device including: - a first signal generator connected to a first antenna arrangement, - a second signal generator connected to a second antenna arrangement, - an oscillator for delivering an oscillating signal, in order to clock the signal generators to control each antenna arrangement, and - a synchronisation circuit connected at least to the first signal generator and to the first and second antenna arrangements (6, 7), the synchronisation circuit being arranged to receive at input a data and/or command modulation signal (S mod) and to control, in a synchronous manner, the first signal generator and the first and second antenna arrangements (6, 7) to perform amplitude modulation on the data and/or command to be transmitted on two amplitude levels by a combination of the signals transmitted by the antenna arrangements, a first stable modulation state on a first amplitude level being defined when the signals transmitted at a defined carrier frequency f0 by the first and second antenna arrangements are in-phase, and a second stable modulation state on a second amplitude level being defined when the signals transmitted at a defined carrier frequency f0 by the first antenna arrangement are 180° out of phase from the signals transmitted at a defined carrier frequency f0 by the second antenna arrangement, characterized in that the synchronisation circuit is arranged to temporarily and dynamically switch the first signal generator for the delivery of signals to the first antenna arrangement at a frequency f1 higher or lower than the carrier frequency f0 in a transition phase from a first modulation state to a second modulation state or vice versa in a synchronous manner on the basis of n signal cycles at the carrier frequency f0 transmitted by the second antenna arrangement and counted in the synchronisation circuit, where n is an integer number, and in that the synchronisation circuit is arranged to adapt, in an inductive or capacitive manner, the resonance frequency of the first antenna arrangement to frequency f1 of the signals delivered by the first signal generator during the modulation state transition phase relative to the resonance frequency determined at the carrier frequency f0 of the first and second antenna arrangements in a stable modulation state. - a first signal generator connected to a first antenna arrangement, - a second signal generator connected to a second antenna arrangement, - an oscillator for delivering an oscillating signal, in order to clock the signal generators to control each antenna arrangement, and - a synchronisation circuit connected at least to the first signal generator and to the first and second antenna arrangements (6, 7), the synchronisation circuit being arranged to receive at input a data and/or command modulation signal (S mod) and to control, in a synchronous manner, the first signal generator and the first and second antenna arrangements (6, 7) to perform amplitude modulation on the data and/or command to be transmitted on two amplitude levels by a combination of the signals transmitted by the antenna arrangements, a first stable modulation state on a first amplitude level being defined when the signals transmitted at a defined carrier frequency f0 by the first and second antenna arrangements are in-phase, and a second stable modulation state on a second amplitude level being defined when the signals transmitted at a defined carrier frequency f0 by the first antenna arrangement are 180° out of phase from the signals transmitted at a defined carrier frequency f0 by the second antenna arrangement, characterized in that the synchronisation circuit is arranged to temporarily and dynamically switch the first signal generator for the delivery of signals to the first antenna arrangement at a frequency f1 higher or lower than the carrier frequency f0 in a transition phase from a first modulation state to a second modulation state or vice versa in a synchronous manner on the basis of n signal cycles at the carrier frequency f0 transmitted by the second antenna arrangement and counted in the synchronisation circuit, where n is an integer number, and in that the synchronisation circuit is arranged to adapt, in an inductive or capacitive manner, the resonance frequency of the first antenna arrangement to frequency f1 of the signals delivered by the first signal generator during the modulation state transition phase relative to the resonance frequency determined at the carrier frequency f0 of the first and second antenna arrangements in a stable modulation state.