In this paper, three useful scrambling and descrambling systems are introduced. The technique, security and cost requirement of each system will also be discussed. Digital line shuffle is the most up-to-date digital scrambling method. Random baseband frequency inversion and channel transfer is a simple and practical scrambling method. Addressable traps is a simple control method which is suitable for cable systems in hotels and apartment complexes. In this paper, the principles and the addressing methods of these systems are introduced The most advanced system we have developed utilize digital random encoding methods and employ ASIC decoders. These systems have large addressing capability up to 16.5 million and a very fast addressing speed of 5,000 subscribers per second. We will compare these three systems in terms of their technique, security and system cost, such that the service provider can select the system most suitable for his use.
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