| 摘要 |
PURPOSE:To prevent malfunction of a multiple pushing state by providing a canceling circuit to a selector to select one out of a group of reception lines to switch it and at the same time to fix other reception lines at a fixed potential, respectively. CONSTITUTION:An electrostatic capacity type keyboard consists of a control means 1, a drive circuit 3, a variable capacity switch matrix 5, a selector 7, an amplifier 10 and a discriminator 12 and decides an ON or OFF state of a key. Here a canceler 24 is added to the selector 7 to fix a reception line at a fixed potential. Thus the AC signal is impressed to a scan line from the circuit 3 and other scan lines are set at a high impedance level, respectively. At the same time, the selector 7 selects a single reception line and delivers it. Then the selector 7 actuates the canceler 24 with the reception control signal 8 and sets other reception lines at the ground levels. This prevents such malfunction where the AC signal sneaks in owing to the multiple pushes of a key.
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