| 摘要 |
<p>PURPOSE:To input surely data always by changing the wave height of scanning pulses in stages and making selection of two detecting signals of maximum level possible even when the two detecting signals are obtained at one scan. CONSTITUTION:A discriminating circuit 25 composed of a counting circuit 23 and extracting circuit 24 extracts one maximum level detecting signal or two maximum level detecting signals of nearly same levels from a detecting signal from a comparator 10. Upon receiving the detecting signal, a control circuit 20 controls a driving level switching circuit 31 and changes the wave height of scanning pulses in stages. In this case, the counted value of a counter 7 is sent as coordinate information through a latch circuit 13 by means of the detecting signal when one maximum level detecting signal is extracted, or by means of one detecting signal selected by a comparator 14 when two maximum level detecting signals are extracted. When such an arrangement is used, non-detected area can be eliminated from an expanding key segment and data can be inputted always surely.</p> |
