| 摘要 |
The key scan circuit of a telephone system includes a central processing unit for generating key scan data, receiving response data and sensing a key input state, a key pad for receiving the key scan data and generating prescribed response data according to a key depressed state, a diode array for transmitting the key scan data to the key pad and suppressing momentary current generated from the key pad from being applied to the central processing unit, and a buffer for receiving and buffering the response data generated from the key pad, thereby improving the speed of a scanning operation.
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