| 摘要 |
PURPOSE: To switch the mode to a waiting mode only when the radio wave state is bad and is not suitable for speaking. CONSTITUTION: The reception level is detected by a detection circuit 25 at each time point of a prescribed period. In the speaking mode, reception levels at plural prescribed time points to the latest time point are stored in a storage circuit 33. If the reception level reaches a prescribed value at the latest time point, a muting circuit 22 is turned off. If it doesn't reach the prescribed value at the latest time point, the muting circuit 22 is turned on, and the speaking mode is continued until the number of reception levels which don't reach the prescribed value out of reception levels stored in the storage circuit 33 exceeds a prescribed proportion. When it exceeds the prescribed proportion, the speaking mode is switched to the waiting mode. |
