A transponder-reader payment system includes a fob including a transponder, and a RFID reader for interrogating the transponder. The system may further include a personalization system for populating onto the fob and RFID reader identifying information and security and authentication keys which may be used during mutual authentication of the fob and the reader and for completing a transaction. In exemplary operation, the fob and RFID reader may be personalized, the fob may be presented to the RFID reader for interrogation, the fob and reader may engage in mutual authentication, and fob identifying information may be provided to the reader for transaction completion. In another exemplary embodiment, operation of the transponder-reader payment system may be controlled by an activation circuit. Further, the fob may be responsive to multiple interrogation signals.