In HDLC or SDLC, a standard bit pattern(01111110) that begins and ends each frame; it is used for synchronization and identifies a frame to receiving hardware.

• HDLC或SDLC规程中的一种标准的位组合,即01111110,用以标识每一帧的开始和结束,还可用于与接收站硬件同步,并向接收硬件标识到来的帧。