PURPOSE: To increase the kinds of privacy call keys and to improve the performance of privacy call by providing a transmission section composed of a constant envelope processing section, an envelope detection section, a modulation section and a band split section or the like and a reception section composed of a band split section, a demodulation section, a decoding section and an envelope decoding section or the like.
CONSTITUTION: An input voice signal is subjected to a constant envelope processing by the constant envelope processing section 1 of a transmission section 6 to be a frequency information signal and to be amplitude information signal through the detection of an amplitude envelope at an envelope detection section 2. The frequency information signal is subjected to band split so as to form an idle band according to privacy call key information at a band split section 4. Moreover, the amplitude information signal is modulated by a modulation section 3 so as to be inserted in the idle band according to the privacy key information and added to the output of the section 4 at an adder section 5. Furthermore, a reception section 11 receives a privacy call signal and the amplitude information and the frequency information signals are decoded from the band split by the band split section 7 via a demodulation section 8 and a decoding section 8 according to the privacy call key information, an envelope decoding section 10 multiplies both amplitude and frequency signals and the voice signal is decoded. Thus, the number of privacy call keys is increased to improve the performance of the privacy call.
AKIYAMA RYOTA
HASEBE TAKAYUKI
AZUMA MITSUHIRO
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