Clipper uses an NXP Semiconductors MIFARE DESFire (MF3ICD40) or MIFARE DESFire EV1 (MF3ICD41) integrated circuit to manufacture the card. The card operates on the 13.56 MHz range putting it into the Near Field Communication category (rather than RFID, as is commonly misconceived). Because the card uses NFC technology, any NFC-enabled device can read the serial number, travel history, and current balance on the card. However, data cannot be written to the card without the proper encryption key, preventing unauthorized access to funds on the card. The former Translink cards, while still functional on the fare system readers, do not conform to MIFARE and are unreadable by 13.56 MHz readers.