| 摘要 |
PURPOSE:To improve the hand free talking by utilizing that a talker utters with sound volume more than a noise level so as to distinguish the voice from the noise. CONSTITUTION:When a reception signal is outputted from a hybrid circuit 5 and passes through a broad band-pass filter 14, a signal at an audible band only is outputted. The signal is averaged for several seconds by a level averaging circuit 16 and the result is given to a level comparator 17 as a noise level of the line. The level is compared with an output of a voice band filter and when the voice band output is larger, an output signal is fed to a level comparator 9 and compared with a surrounding noise level of a level comparator 21. Since the noise is distinguished from the voice in this way, a hand free telephone set is used in an excellent way with a telephone line having much noise or in a room having a large surrounding noise. |
