Applies to radiotherapy simulators: - that use diagnostic X-ray equipment to simulate physically a therapeutic radiation beam, so that the treatment volume to be subjected to irradiation during radiotherapy can be localized, and the position and size of the radiotherapy radiation field can be confirmed; - intended exclusively for radiotherapy simulation as a prelude to intended radiotherapy, and not for any other purpose such as general diagnostic examinations. Establishes requirements to ensure the ionizing radiation safety and enhanced mechanical and electrical safety of radiotherapy simulators; it identifies geometrical parameters that are critical for the accurate simulation of a radiotherapy treatment. Cancels and replaces the first edition published in 1993 and its amendment 1 (1996).