| 摘要 |
PURPOSE:To smooth the progress of a conference by providing a means informing the present line closing state to a multi-function telephone set connected to a private branch exchange so as to allow the operator of the multi-function telephone set to recognize the present line closing state. CONSTITUTION:At the time of a caller of a telephone set 13b utters something, its voice signal is sent to a private branch exchange 11, inputted to a trunk 42b, subjected to 2/4-wire conversion and an output signal toward a channel switch 43 is inputted to a voice detector. Whether or not the voice is discriminated in the voice detector depending on the sound pressure level and the duration time of the input signal and when the voice is discriminated, a line signal corresponding to its extension telephone set is outputted to a data transmission/ reception circuit only when the voice signal continues. The channel control circuit sends information of a line number corresponding to the extension telephone set participating in the conference talking timewise and voice detection is applied from the object line. Thus, even when >=2 persons make a call at the same time, a line state display lamp lights in red from green color according to the length of respective speech.
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