| 摘要 |
PURPOSE:To prevent erroneous collation of an information code string while frames are in out-of-synchronization by dividing the information code string into two parts, inserting check bits consisting of two bits between the divided codes, and inverting the logical values of the check bits alternately in each frame. CONSTITUTION:A frame is constituted of a frame synchronizing bit F, an information code string I1-IK consisting of K bits, the check bits C1, C2, and an information code string of N-K bits; and the logical values of the check bits C1, C2 are alternately inverted. If out-of-synchronization is generated in case of comparing the information code strings between the succeeding two frames and deciding the correctness/incorrectness of the information code strings, unmatching is detected at the existence of the check bits C1, C2, so that overlock errors which may be generated in the period from the generation of out-of-synchronization to its detection can be removed. |
