Identification beacon by the passage of a vehicle in a specified point.

The tag is constituted by a waveguide (1) having a large face (2) having longitudinal slots (3) and doublets distributed along the axis (WW ') of the major face at a rate of one every doublet n longitudinal slots. Each dipole is constituted by two transverse slots (4, 4 ') situated facing a longitudinal slot. The presence of a doublet corresponding to a bit of value 1 and its absence to a value o bit. The longitudinal slots receive a transmitting antenna (A1) radiation having a low frequency and a high frequency; they radiate toward a first receiving antenna (A2) radiation at high frequency; doublets radiate to a second receiving antenna (A3) radiation at low frequency. The antennas are fixed to each other and relative movement with the tag.