| 摘要 |
The circuit includes a microprocessor (1) for performing overall controls, and a function selecting means (2) for selecting function modes. A DTMF (dual tone multi-frequency) decoding means (3) decodes incoming DTMF signals into 4-bit signals, and first and second switching means (SW1,SW2) selectively supply the inputted signals to a speaker (b) or to the DTMF decoding means (3). Second switching means (SW3,SW4) selectively supply the data signals of a hand set (f) to a microprocessor or to a telephone set, and third switching means (SW7,SW8) selectively supply the output data of the microprocessor and a telephone set (e') to a hand set (f').
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