| 摘要 |
PURPOSE:To avoid a wrong detection of a depression of a key, caused by a noise, by outputting an output corresponding to a depression of a key, extending over a scanning period of plural times from an input voltage holding circuit. CONSTITUTION:When a scanning signal Vd is sent out again from a driver 4 to X0 of a line 1, if a C00 key is depressed continuously in advance, an input signal Vi is amplified by an amplifier circuit and inputted to an anode of a diode 11. In case when the input signal is larger than a forward voltage of the diode, the input signal passes through the diode 11 and a capacitor 14 is further charged. When the scanning signal Vd is sent out by a necessary continuous number of times, an output voltage V0 is obtained in an output of a voltage follower circuit 15, and it is a sufficient potential for detecting a depression of a key by a keyboard controlling circuit 17.
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