| 摘要 |
PURPOSE:To maintain normally the sequence of discramble even when the input of an external frame synchronizing signal is interrupted by ensuring the self-synchronization of a PN series generator. CONSTITUTION:The specific state of a shift register array in the PN series generator 1 is detected by a gate circuit 6, the output of the gate circuit 6 and a frame synchronizing signal 2 inputted externally are ORed to preset the PN series generator 1 by an OR gate 7. In selecting the interval between the specific state and the preset state of the shift register in the PN series generator 1 to be detected by the gate circuit 6 equal to the frame synchronization, even when the external input of the frame synchronization signal 2 is interrupted due to any fault, the self-synchronization of the PN series generator 1 is taken and the PN series generator 1 is not run away. A scramble signal 4 inputted externally and a PN series signal 8 are ORed exclusively by an exclusive OR gate 3 and the discramble is executed by a correct sequence. |
