The Contactless Chipcard Interface(CCI) is the air interface of contactless chipcards. It is used for bidirectional communication between the RFID card or radio tag and the RFID reader. In addition, the CCI interface is used to supply the passive contactless smart card with power.
On the RFID card, the CCI interface is formed by two coils. In conjunction with capacitors, these coils act as oscillating circuits that are tuned to the radio frequencies. The supply voltage is generated by rectifying the carrier signal of the RFID reader. The supply voltage is 5 V with a power of up to 100 mW.