| 摘要 |
PURPOSE: A circuit for selecting a vocal communication mode is provided to selectively use any one of a CVSD(Continuous Variable Slope Delta modulation) mode and a vocoder mode. CONSTITUTION: The circuit has an amplifier(113) for primarily amplifying a vocal signal inputted through a microphone(111), and another amplifier(115) for secondary amplification. A secondary amplified signal is inputted to a CVSD converter(117), while a primarily amplified signal is inputted to a vocoder(119). The CVSD converter and the vocoder encode the vocal signal by different processing methods, respectively. Signals encoded by the CVSD converter and the vocoder are inputted to a switching circuit(121). The switching circuit selects any one of outputs from the CVSD converter and the vocoder depending on an inputted selection control signal. An AGC(Automatic Gain Controller)(123) primarily amplifies a vocal signal output from the switching circuit by a preset gain, and sends a primarily amplified vocal signal to the first input(1) of the first header(127). Another AGC(125) secondarily amplifies the primarily amplified vocal signal, and sends a secondary amplified vocal signal to the first input(1) of the second header(129). Two vocal signals output from two AGC(123,125) are inputted to the second input(2) of the first header(127).
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