| 摘要 |
PURPOSE:To attain uninterruptible switching surely by providing an in-band amplitude deviation detecting circuit and performing line switching from the result of detection of said in-band amplitude deviation detecting circuit. CONSTITUTION:A receiving signal on a common use line inputted from a signal input terminal 1 is inputted to an in-band amplitude deviation operating circuit 4 through plural band characteristic detecting circuits 3 passing frequencies different each other. The power of a receiving signal is detected by a receiving power detecting circuit 5 and inputted to a receiving power operating circuit 6. A line quality discriminating circuit 8 inputs an in-band amplitude deviation I outputted from the in-band amplitude deviation operating circuit 4, a changing speed Iv of the in-band amplitude deviation, a receiving power A outputted from the receiving power operating circuit 6, and a changing speed Av of receiving power or the like, and discriminates the presence of the necessity of switching through a judgment of the overall evaluation of them. |
