| 摘要 |
PURPOSE:To improve tone quality by switching the path of a sound signal to a circuit having proper frequency characteristics at the time of secret talk operation. CONSTITUTION:A mobile equipment 202 makes a telephone call to a subscriber line 203 through a fixed equipment 201 which is connected by radio. For a radio connection in normal mode, signal processing circuits 205 and 211 performs signal processing of a compressor, an expander, preemphasis, deemphasis, etc., according to the communication direction. For a radio connection in secret talk mode, the signal processing circuits 205 and 211 performs a secret talk processing by, for example, frequency inversion. In secret talk mode, switches 216 and 218 are switched to insert tone quality circuits 215 and 217 into a speech circuit respectively. The tone quality circuits 215 and 217 consist of filter amplifier circuits, etc., and are set to frequency characteristics with which a decrease in tone quality in the secret talk mode is compensated. |
