| 摘要 |
The circuit comprises a mode selection switch (SW1) which selects a hands free mode, privacy mode, and tone mode, a central processing unit (1) which controls the input and output of an analog switching units (5) (8), a tone generating unit (10), and a switching unit (Q1) that correspond to each mode, detecting the status of selection of the mode selection switch (SW1), a first analog switching unit (5) which connects telephone lines with a speaker processing unit (6), a hand set unit (4) which is connected with the first analog switching unit, a speaker phone processing unit (6) which processes the signals of a speaker phone, a microphone (7) which inputs the voice signal of an user to the speaker phone processing unit, a switching unit(Q1) which controls the supply of the voice signal inputted to the microphone, a second analog switching unit (8) which selectively supplies the input signals of the speaker phone processing unit and the tone generating unit to a speaker, a speaker (9) which outputs the signals inputted from the second analog switching unit.
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