Cable television performance must periodically be upgraded to meet new requirements. The application of digital devices and techniques to provide improved security, multichannel audio and other features is described. Basic cable equipment functions, reasons for selecting digital techniques, audio and video multiplexing, constraints encountered, functional blocks developed, encryption, synchronization and overall performance obtained are reviewed. The outcome is a system which provides audio with stereo or bilingual capability. Furthermore, the digitized and encrypted audio is transmitted on the same carrier as the video signal.