An identification tag is formed with a single microcircuit. The microcircuit includes an optical transceiver, a radio transceiver, both connected to a memory storing an identification code. At least one of the transceivers operates in receive mode, and at least one of the transceivers operates in transmit mode. The identification code is transmitted by the transceiver operating in the transmit mode in response to receiving a predetermined signal by the transceiver operating in the receive mode.