| 摘要 |
PURPOSE:To improve the supervisory function, by supervising the synchronizing signal included in the video signal besides the pilot signal and by combining supervisory results of both signals. CONSTITUTION:The video signal transmitted from transmission part 1 through the video signal transmission line (line 2 and realy 3) is received by terminal unit 4, and existence of the synchronizing signal and level properness are detected by synchronizing signal supervisory part 5, and existence of the pilot signal is detected by pilot signal supervisory part 6. In this case, if normalcy detection signals are transmitted from synchronizing signal supervisory part 5 as well as pilot signal supervisory part 6, no abnormal alarm output is transmitted from alarm terminal ALM because these signals pass through AND 7 and inverter 8. Meanwhile, if one or both of the pilot signal and the synchronizing signal are not received normally, the output of AND 7 is low-level and is inverted by inverter 8, and abnormal alarm is output from alarm terminal ALM. |
