The decoder interface has, for quite some time, been viewed as an important technology for cable -- first for consumer-friendly deployment; then by force of law; now a critical requirement for the deployment of High Definition Television (HDTV). This paper describes how HDTV (and SDTV) digital transmission needs the decoder interface -- and what obstacles lie ahead. In the focus of cable technology over the years, the "last mile" has always been a critical hurdle to overcome. In the cable deployment of HDTV to digital TV's the critical technology hurdle has become the "last six-inches." The specifics of digital interfaces such as 1394 "FireWire" are discussed as are business requirements such as digital copy protection.