A radiofrequency identification device (RFID) featuring an antenna (10) connected to a chip designed to be affixed to an object to be identified by a remote reader transmitting to the identification device electromagnetic signals received by the antenna and containing the data allowing the identification as well as the supply voltage (V.sub.DC) of the device, the antenna transmitting in return to said reader signals provided by the chip by retromodulation by means of a switch (22) in the chip whose open or closed position defines the digital identification data transmitted by the device. The chip features a variable impedance (30) connected in series with the switch to the terminals of the antenna and a means for detecting (32) the supply voltage to adjust the impedance value so that this supply voltage is always greater than a predetermined value (V.sub.threshold) below which the device can no longer transmit digital identification data.