| 摘要 |
PURPOSE:To detect which contact is in ON state on a deyboard by connecting switches and a detecting circuit by a lead wire and making different the level of resistance of a closed circuit which is formed when those switches are turned on. CONSTITUTION:Switches 4-1-4-7 are connected to a D/A converter 6 with a lead wire 7 so that the resistance value of the wire 7 is different for each switch when it is turned on. Therefore, the voltage applied between input terminals of the converter 6 goes to high potential difference in order of switches closer to the input terminal of the converter 6, i.e., from the switch 4-1 through 4-7 in case either one of those switches is turned on or all switches are turned off. Therefore, the converter 6 gives an A/D conversion to the input voltage which is different by the switch that is turned on or the fact that any of those switches is not turned on. Then the converter 6 codes and outputs the signal showing which switch is turned on. |
