| 摘要 |
PURPOSE:To shorten the stop time of the repeating operation to improve the data transmission efficiency by providing a gate circuit, which operates the exclusive OR between outputs of tone detecting parts to obtain an output signal, and a control part which generates a control signal switching a switch circuit when ouputs of tone detecting parts are lower than a prescribed level. CONSTITUTION:Outputs from band pass filters 11 and 11' and rectifying detectors 12 and 12' in two systems I and II which are switched by a changeover switch 21 are outputted to an EX-OF circuit 22, and the changeover switch 21 is driven by the output of an FF circuit 23 operated by the output of this circuit 22. For example, the tone connected to the system I (side A) is subjected to frequency detection by the band pass filter 11 and is subjected to envelope detection by the rectifying detector 12, and signal '1' is outputted at an output point C. When the succeeding time different in phase is inputted to the system I, the signal at the point C is '0' because the synthetic envelope is reduced at a point B, and consequently, an output point E of the EX-OR circuit 22 is '0', and the output of the circuit 23 is inverted, and the changeover switch 21 switches the system I to the system II. |
