Scramblers and shift register generators (SRG) have been used for decades in the shaping of digital transmission signals and in generating pseudo-random binary sequences for transmission applications. In recent years more attention has been paid to this area than ever before due to the change of today's telecommunication environment. This publication presents the theory and applications of three scrambling techniques - Frame Synchronous Scrambling (FSS), Distributed Sample Scrambling (DSS) and Self Synchronous Scrambling (SSS) with an emphasis on their application in digital transmission. Based on the authors' research over the past ten years, this is the first book of its kind.