| 摘要 |
<p>PURPOSE:To detect the using condition and the coordinate input position of a position indicator without deteriorating the operability of the indicator, by discriminating the using state of the indicator from the phase change of a received signal against a transmitted signal of an antenna coil and at the same time detecting the coordinate input position of the indicator. CONSTITUTION:When an input pen 2 is detached from at tablet surface, a phase difference phi changes about 180 deg. due to the inductance change of a coil 222. Thus a comparator 415 discriminates surely the state of the difference phi=0 obtained when the pen 2 is pressed to the tablet surface from a state other than phi=0 that is set when the pen 2 is detached from the tablet surface. The prescribed threshold voltage +VT is previously supplied to an input terminal set at the other side of the comparator 415. The output of an LPF 414 is compared with the voltage VT. The signal G of anxoutput terminal 416 of the comparator 415 is set at an H level with phi-0 and then at an L level when the difference phi has a change by several tens degree. Therefore, the input of coordinates is possible just by pressing the pen 2 onto a tablet 1 after sending the signal G to a position detecting circuit 3.</p> |
