| 摘要 |
<p>PURPOSE:To accurately identify the use state of a position pointer by providing a transmission antenna coil and a reception antenna coil independently of each other. CONSTITUTION:A multiplexer 702g of a timing circuit 702 outputs a signal A where square waves having frequencies f1-f4 are repeated at intervals of a time 2T, and this signal is not only sent to a phase detector 710 but also converted to a sine wave signal by a reduction filter and is sent to the negative input terminal of an analog switch 704. The negative input terminal is selected while a switching signal B is in a high level, and the other input terminal is selected while it is in a low level; and therefore, a signal D which is outputted or not outputted in the time T appears in the output and is sent to a driving circuit 706 and is sent to a transmission coil 13, and the radio wave where frequencies f1-f4 are repeated at intervals of the time 2T is transmitted from the transmission coil 13 only for the time T. Consequently, a large AC signal is applied to the transmission coil 13.</p> |
