| 摘要 |
<p>Apparatus for delivering power to and communicating with a data-storing device (4), e.g. a token, in a contactless manner includes a resonant circuit (6) arranged for inductive coupling with the device. The values of the components are selected to give a relatively constant power transfer over the possible range of distances between the inductances (36, 8). Communications from the device resulting in changes in the token impedance are detected by sensing current changes in the resonant circuit. The power transmitted by the resonant circuit is limited to prevent excessive power damaging devices whose characteristics are such that they may be damaged by higher power levels. Devices which require higher levels can send a signal which results in the limit being bypassed.</p> |
