| 摘要 |
PURPOSE:To transmit a subsignal without sacrificing the transmission of a main signal by selecting and transmitting either first or second frame synchronization bit string different with each other making conform to the bit '1' of '0' of the subsignal. CONSTITUTION:At a terminal station 11 side, a first frame synchronization bit string(F1) generating part 21 and a second frame synchronization bit string(F 0) generating part 22 are provided, and the F1 or the F2 is attached on the main signal M at a frame synchronization bit string insertion part 23. A selection part 20 selects the output of either the generating part 21 or 22 corresponding to the bit '1' or '0' of the subsignal S. A terminal station 12 at a reception side is provided with a frame synchronization detecting part 24, and detects the F1 or the F0 in the frame synchronization bit string while making the main signal M pass as it is, and sends the bit '1' or the '0' to a monitoring device 14. In such a way, it is possible to transmit the subsignal S by superposing on the non-transmission information part of the main signal M to the reception side. |
