| 摘要 |
<p>PURPOSE:To adjust a tuning frequency without using a measuring instrument by providing a switch which arbitrarily selects one of a detection mode and an adjustment mode. CONSTITUTION:A mode changeover switch 722 is connected to the side of the adjustment mode, namely, a pulse width detector 717, and a position pointer, for example, a marker is held on a writing face in a blackboard body so that it can be used, and the front end of a pen body is brought into contact with the writing face to set a switch 251 to the operating state, and then, a radio wave is transmitted and received among a transmission coil 13, a reception coil 14, and a coil 252 of a tuning circuit 25. If the capacity value of a variable capacitor 254 of the tuning circuit is so controlled that a LED 727 emits light, the tuning frequency coincides with the frequency of an AC signal.</p> |
