| 摘要 |
A key signal scanning apparatus of a complex telephone comprises: a keypad having plural row ports, plural column ports, and plural keys for generating a key signal in accordance with pressing of a key by a user; a main microprocessor which operates by externally supplied power for supplying a timing signal to the row ports of the keypad by using row output ports, for receiving the key signal from the column ports of the keypad by using column input ports, for detecting a key pressed by the user by scanning the received key signal, and for outputting a dialing signal corresponding to the scanned key; a sub microprocessor which operates when power is not supplied from an external source for outputting a dialing signal generated according to the key signal inputted from the row ports and the column ports of the keypad; a first separator circuit for cutting off current flow to the row output ports of the main microprocessor from the row ports of the sub microprocessor; and a second separator circuit for cutting off current flow to the column ports of the sub microprocessor from the column input ports of the main microprocessor when power is not supplied from the external source. The present invention can scan the key signal without reciprocal influence when external power is supplied and not supplied by provision of a separator circuit between the main microprocessor scanning the key signal when external power is supplied and the sub microprocessor scanning the key signal when external power is not supplied.
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