| 摘要 |
PURPOSE:To expand a dynamic range and to improve a speech quality by providing a transmitter with a frequency compensation circuit and providing a receiver with a reverse frequency compensation circuit which has the reverse characteristic of the frequency compensation circuit. CONSTITUTION:In the transmitter 101, a compressor 106 compresses the signal level of a sound signal from a band pass filter 105 within a prescribed range to output it to a frequency compensation circuit 107. The higher the high frequency level the signal level of the sound signal is enlarged by the circuit 107, all the frequency components of the output of the circuit 107 become almost uniform and S/N after a secret speech circuit constituted by a scramble circuit becomes constant without regard to the frequency. A receiver 102 demodulates a reception sound signal, releases a secret speech and sends the signal to the reverse frequency compensation circuit 11b. A circuit 116 functions in opposition to the circuit 107, returns the frequency characteristic to that before the compensation to restore the sound signal. Thus, the dynamic range can be enlarged and the speech quality can be improved. |
