| 摘要 |
PURPOSE:To prevent the deterioration the sound volume, the articulation, etc. of a remote controller, by setting a tone signal for control at a low band frequency and at the same time inverting the frequency spectrum of an audio signal to be transferred so as to reproduce again both the audio and control tone signals at the receiving side. CONSTITUTION:An audio input signal is modulated with a subcarrier given from the 1st subcarrier oscillator 3 and through a balanced modulator 2 of the transmitting side 21. The low-side band signal component is extracted out of a modulated wave signal through an LPF4, and a part of the low-frequency component is deleted through an HPF5. Both the output of the HPF5 and a control tone signal supplied from a control signal oscillator 6 are applied to a buffer amplifier 7, and the transmitting signal is sent to a single transmission line 25. This signal is applied to a balanced demodulator 11 of the receiving side 22, and at the same time the subcarrier given from a subcarrier oscillator 10 is applied to the demodulator 11. Then the output of the demodulator 11 is applied to an LPF12 to reproduce the audio signal. At the same time, a signal is applied to a wave detector 9 via a BPF8, and a control tone signal is delivered from the detector 9. In such a way, the deterioration of the sound volume, the articulation, etc. can be avoided for a remote controller. |
