| 摘要 |
A telephone having a line input, a line output, a handset microphone, and a handset speaker also includes a first soft mute circuit coupling the handset microphone and the line output and a second soft mute circuit coupling the line input and the handset speaker. The telephone is operated in a first mode and can change modes only after muting one or both soft mute circuits, changing mode, and then operating in the second mode only after unmuting the circuits. The muting may be momentary or prolonged, depending upon the particular mode of operation. An additional soft mute circuit is used in a speakerphone.
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