| 摘要 |
PROBLEM TO BE SOLVED: To always provide a stable speech quality of a technique for switching a side tone level at a connecting time of an extension telephone set to be housed in a key telephone device to a line wire. SOLUTION: This key telephone device comprises a means for measuring a type of a channel housed at a power source supplying time and a side tone level of each channel, and a means for calculating a suitable side tone level for the housed extension telephone set from the measured tone level at each channel and generating the suitable level as a side tone level correcting value. The device transmits the side tone level correction value of the aligned channel in the case of requesting a call from the extension telephone set, corrects the tone level to the side tone level of the connecting channel, and then starts speech connecting. The device further transmits the side tone level correction value of the channel to the off-hook responding extension telephone set in the case of incoming from the channel, corrects the tone level of the extension telephone set to the tone level of the channel, and then starts the speech connecting.
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