Currently available Set-Top-Boxes (STBs) are mainly used for digital TV reception. The User Interface (UI) and the UI dialog of such a device usually focus on its technological aspects and to a large degree ignore the needs of the user. The impact is that the user quite often is unsatisfied when interacting with the device. Recent UI design approaches [9][10] are proving that the focus should be put on the tasks that the user can perform with a STB rather than its underlying technical capabilities. However, modern design approaches both for the STB UI as well as its underlying system architecture can be incorporated into a complete system design with reasonable effort. This paper presents the architecture of the “d-box”, a STB being used for broadcasting TV services as well as future interactive services like internet, home-shopping etc. in Germany. The layered software architecture employs a Java Virtual Machine offering a high degree of independency of its underlying hardware. E...