This article tells you how to modify a give-away RFID reader so it can read MIFARE ISO 14443 cards. Alternatively you can either modify an existing BSI reader or use the information obtained from reverse engineering to build the entire reader yourself. These readers use two different types of IC, and we provide circuit diagrams for each type. Finally, we describe a reader with no special components for use with RFID devices compliant with the ISO 15963 standard.