| 摘要 |
PURPOSE:To obtain the signal identification circuit strong in mechanical vibration and without no characteristic change under environmetal conditions, by using a resonance circuit, phase shifter and phase detection circuit constituted with active elements and surely separating adjacent two signals. CONSTITUTION:A control signal for audio multiplex broadcast switching for TV is fed to an input terminal 10 and this control signal is fed to a broad band amplifier 12 of a resonance circuit 11 constituted with active elements and a transmission zero point filter 13. The resonance point of the amplifier 12 is taken as the center frequency of two control signals, negative feedback is made to the amplifier 12 with the filter 13, and the signal having the phase difference corresponding to the frequency difference is fed to a phase detection circuit 15 from the circuit 11. Further, the control signal is fed to a phase shifter circuit, and the signal having the phase difference of 180 deg. is output from the output of the circuit 14 and fed to the detection circuit 15. Further, the output from the circuit 14 is compared for detection with the phase difference corresponding to the frequency difference from the circuit 11, and two control signals are accurately separated from the output terminals 17,18 of the switching circuit 16. |
