| 摘要 |
PURPOSE:To transmit digital message data and video data with good efficiency, by using one of transmission lines as a digital line and another as an analog line also serving as the digital line respectively in double loop connection constitution. CONSTITUTION:Since photoelectric conversion section 1'b and electrooptic conversion section 2'b connected to a spare transmission line Lb are constituted with elements which can transmit analog signals and the sections are connected to a device 7 via video selector switches 8, 9, video data ID can be transmitted via the switches 8, 9. In moving pictures among the data, at a system normal state, switches 5, 8, 9 are controlled by using the fact that the line Lb is vacant and an analog base band signal can be transmitted. At system failure, since switches 3, 4, 5 are controlled for the line Lb to transmit a digital message data DD, the moving picture data is disconnected from a station ST. The moving picture data is digitally transmitted as still pictures through digital coding. |
