In telecommunications, a self-synchronizing code is a line code in which the symbol stream formed by a portion of one code word, or by the overlapped portion of any two adjacent code words, is not a valid code word.
A self-synchronizing code permits the proper framing of transmitted code words provided that no uncorrected errors occur in the symbol stream.
External synchronization is not required.
High-Level Data Link Control (HDLC) and Advanced Data Communication Control Procedures (ADCCP) frames represent self-synchronizing code words.