| 摘要 |
PURPOSE:To limit the number of wirings from a touch sensor to two without regard to the number of keys, and to facilitate wiring operation, by detecting electric resistance generated when a transparent electrode is brought into contact at some key position, and thus detecting the position of the key. CONSTITUTION:When a key al is turned on, a voltage Vl=Cl (C=2IR) is applied to an input of a comparator 10. When an n-scale counter 13 goes up to l, a D-A converter 12 outputs a voltage Vl=Cl and the comparator 11 has a reference voltage Vl=Cl, so the input voltage to the comparator 11 becomes equal to the reference voltage, outputting an output signal S. The output signal S allows an encoder 15 to latch the binary output of the counted value l of the counter 13, and the code which corresponds to the counted value l is encoded to generate the code which corresponds to the key Al. |
