| 摘要 |
PURPOSE:To obtain a simultaneous talking system immune to a transmission line loss by providing a frequency converting circuit of a voice signal. CONSTITUTION:A voice signal entering from a transmitter 3 is given to a middle tone emphasis band pass filter 4, where it is processed into a frequency and converted into a frequency from the 1st local oscillator 8 at a summing frequency mixing circuit 5a at the outside of an audible frequency once. Further, a subtraction frequency mixing circuit 6a subtracts a frequency from the 2nd local oscillator 9 and restores it into the voice band frequency. The voice signal shift frequency is decided by the difference between the 1st local oscillation frequency and the 2nd local oscillation frequency. The shifted voice signal is synthesized with a data code through a spurious elimination filter 7a, a hybrid transformer 14a, a high pass filter 13 for separating a data code and connected to a transmission line 16 by a hybrid transformer 14b. The signal is demodulated in the reception system with an opposite path to the transmission system. The frequency of a data code transmission circuit 11 and a data code reception circuit 12 is set to the shifted voice frequency band.
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