A radio-frequency identifier tunable by dielectric inserts (3), includes a fixed part (92) and a key (9), the fixed part (92) of includes an indication element (91) and a decoding device (8), which includes an electrical supply unit (84), an evaluation and control unit (83), a decoding device (82) and a control element (81), herein the decoding device (8) is connected to a receiver (7), which includes an antenna (71), an input amplifier (72) and a block (73) of filters and circuits. The decoding device (8) is further connected with a receiver (6), which includes an antenna (61), an output amplifier (63) and a signal generator (62). The key (9) includes at least one carrier (32) connected with at least one insert (3) having at least one additional dielectric block (20) modified on its surface or at least one opening (200) formed inside the insert (3). The dielectric block (20) includes an additional dielectric block (21).