Abstract: A device for the bi-directional transmission of data between a master system and a slave system uses a single transmission antenna and a single reception antenna each tuned to the same frequency; the master system comprises first data transmission circuits for transmitting first data to the slave system by modulating an electromagnetic signal at the frequency; detection circuits for detecting, during the transmission of the electromagnetic signal, variations in electrical characteristics of the master system induced by a modulation of the impedance of the slave system as a function of second data to be transmitted from the slave system to the master system; and restoring circuits for restoring the second data on the basis of the detected variations; and the slave system comprises reception circuits connected to the reception antenna for restoring the first data; a rectifier circuit connected across the reception antenna for rectifying an electrical signal induced in the reception antenna by the electromagneti