| 摘要 |
PURPOSE:To detect an abnormal call immediately due to simultaneous callings by plural stations by using plural earth stations applying transmission and reception via a communication satellite and setting different frequencies used for the transmission and reception to the same frequency tentatively. CONSTITUTION:For the information communication by plural earth stations via a communication satellite, a frequency F1 is assigned to a transmission line and a frequency F2 is allocated to a reception line normally. An earth station starting calling uses the reception frequency F2 for the transmission line tentatively in the timing 6 to send a cease pulse 1 and a station identification number 2. They are monitored by other earth stations as reception signal pulses 3, 4. In this case, when the other earth stations reach calling simultaneously, the signals 3, 4 cause abnormal reception due to the collision of carriers. When the monitor tells no fault, the transmission frequency is restored to the F1 in the timing 7. Thus, the abnormity due to simultaneous calling by plural stations is detected instantly, the simultaneous calling is prevented and the efficiency in the satellite communication is improved. |
