DoorBird A8005 Dual-Frequency RFID Transponder Key Fob, 125 KHZ (EM4100) and 13.56 MHz for A1121, D1812, D21x and later, 10 piecesDoorBird A8005 Dual Frequency RFID Transponder Key Fob, 125 KHZ (EM4100) and 13. 56 MHz for A1121, D1812, D21x and later, 10 pieces 10 Pack The elegant dual frequency RFID transponder Key Fob A8005 from DoorBird supports the worlds most commonly used RFID frequencies 125 KHz and 13. 56 MHz. For the frequency range 125 KHz the Key Fob has an integrated antenna and an EM4100 chip. For the 13. 56 MHz frequency range, the Key Fob has an integrated antenna