APPARATUS AND METHOD FOR DELIVERING POWER TO A CONTACTLESS PORTABLE DATA SOURCE

摘要

A terminal device powers a portable data device by transmitting in two modes of operation. In a first mode of operation, the terminal transmits to the portable data device a power signal at a first level and a data signal using a first modulation format and a first bit rate. In a second mode of operation, the terminal transmits to the portable data terminal a power signal at a second level and a data signal using a second modulation format and a second bit rate. The terminal determines a requirement to change modes of operation, and changes modes in response to changing power requirements of the portable data device.