| 摘要 |
PURPOSE:To suppress an echo signal due to the fluctuation of an echo path characteristic by using a retrieval signal for the 1st echo canceller at the initial setting and using a transmission signal for the 2nd echo canceller so as to estimate the fluctuation of the echo path characteristic from the initial setting. CONSTITUTION:The retrieval signal generated from a retrieval signal generating circuit 104 becomes a transmission signal at the initial setting, the echo canceller 107 uses the retrieval signal to estimate the echo path characteristic and the estimated echo path characteristic of the echo canceller 107 is fixed. When no reception signal exists and only the transmission signal exists, a transmission signal detection circuit 106 sends a control signal to the echo canceller 108 to correct the estimated echo path characteristic and the estimated echo path characteristic of the echo canceller 108 is fixed in other cases. Thus, the echo signal generated at the start of conversion and the howling in a 2-way repeater using an echo canceller are prevented.
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