| 摘要 |
A transaction system (10) comprises a terminal (12) and a contactless card (14). The terminal (12) sends power to the card (14) by means of a carrier. Data is modulated onto a tone which is independent of the carrier, and then the carrier is modulated with the data-modulated carrier. On receiving the carrier, the card demodulates the data from the tone. The tone is used to generate a clock which is used to run the card and the data is used to carry out a transaction between the terminal (12) and the card (14).
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