Abstract: Common definition of system engineer’s work is “executing an interdisciplinary process to ensure that customer and end user’s needs are satisfied”. In Russia such job position is not widespread, besides there is an ambiguity associated with the Russian term, so this was an innovation of Motorola to create in St.Petersburg Software Development Center a team of system engineers who participate in developing software for a Digital TV device. The role of system engineers is receiving market requirements as an input, and providing developers, testers and software architects with clear and unambiguous technical requirements and design specifications, including use cases and feature description for the entire system. The paper shows how these goals can be achieved in the framework of 3-level model for requirements development with reusability principles to be followed. Theoretical considerations are illustrated by examples of how it was applied in a cable TV environment.