| 摘要 |
PURPOSE:To prevent occurrence of step out in frame synchronism in devices of the same order group and lower order groups when circuit changeover is performed, by performing the circuit changeover by comparing the phase difference between changeover signals added in parallel to a transmitting terminal. CONSTITUTION:In the case of a control signal causing an equipment failure of control signals sent to signal lines 8 and 9 from a control circuit 1072, circuit changeover is performed irrespectively of phase of the signal lines 8 and 9. In the case of another control signal causing deterioration in circuit quality, radio transmission lines 301 and 302 are faulty due to fading, etc. In this case, the phase difference between signals on the signal lines 2 and 3 is monitored by a phase difference monitoring circuit 203 and a phase difference signal is sent to a signal line 10. While the phase difference between the signals on the signal lines 2 and 3 is adjusted by phase adjusting circuits 2041 and 2042, the phases of the signal lines 2 and 3 do not always match to each other in the case of circuit quality deterioration. When the phase difference signal on the signal line 10 and a changeover controlling signal which causes circuit quality deterioration occur on the control line 8 and the phases of both the signals match to each other, the circuit is switched by a switching circuit 202. |
