| 摘要 |
PURPOSE:To perform accurate switching, by storing depressing information when a manual switching button is depressed and making the depression information effective when the phase difference between carrier waves of an existing system and a spare system is almost zero. CONSTITUTION:When the operator depresses a manual switching button 21 for manual test, an FF circuit 22 stores it and gives the output of logical 1 to an AND gate 23. Further, carrier waves CN, CE are obtained from sampling point N, E of the carrier waves and given to wave shaping circuit 24N, 24E. Thus, a sinusoidal wave is converted into a rectangular wave. The rectangular wave pulse is given to differentiation circuits 25N, 25E and a differentiation pulse is obtained at the rise. The pulse is set and reset to an FF circuit 26 to obtain a pulse width signal corresponding to the phase difference of the carrier wave from an output Q of the FF circuit 26. When the phase difference is not existed, the pulse width is zero. In the process of zero, a triangle wave is obtained via an integration circuit 27 and compared with a comparator 28 having a threshold value Vr to output depression effective information 23-2. |
