| 摘要 |
<p>PURPOSE:To realize a cordless device and to improve operability by emitting a radio wave from the loop coil of a sense part to a writing tool provided with a turning circuit, receiving it and detecting an induced voltage, and performing such operation for all loop coils in directions of X and Y. CONSTITUTION:In the writing tool, a resonance circuit is constituted of a coil 332 and a capacitor 333, and frequency is set at a prescribed frequency. When the writing tool is held perpendicularly on the writing plane of a blackboard main body, the radio wave excites the coil 332 and generates the induced voltage E. A current that flows on the tuning circuit 33 based on the voltage E causes the coil 332 to emit the radio wave. Since the radio wave excites the loop coil connected to an amplifier 612 in a reverse direction, the induced voltage due to the radio wave from the coil 332 is generated. The induced voltage is sent from a transmission/reception switching circuit 604x to the amplifier 612 only for a reception period, and it becomes a reception signal F, and is sent to a control circuit 601 via a reception timing switching circuit 606 and a detector 608. The circuit 601 computes a voltage value obtained at every loop coil, thereby, the coordinate values of the writing tool in the directions of X and Y can be obtained.</p> |
