Augmented Reality brings technology developed for virtual environments into the real world. This approach can be used to provide instructions for routine maintenance and error diagnostics of technical devices. The Rockwell Science Center is developing a system that utilizes Augmented Reality techniques to provide the user with a form of \X-Ray Vision" into real objects. The system can overlay 3D rendered objects, animations, and text annotations onto the video image of a known object, registered to the object during camera motion. This allows the user to localize problems of the device with the actual device in his view. The user can query the status of device components using a speech recognition system. The response is given as an animation of the relevant device module and/or as auditory cues using spatialized 3D audio. The diagnostics system also allows the user to leave spoken annotations attached to device modules for other users to retrieve. The position of the user/camera ...