[A] Control System [requires:] 1. a set of measurable signals to know the performance, 2. another set of measurable signals to influence the evolution of the system in time, 3. and a third set which is not measurable but disturb[s] the evolution. 'What are Control Systems?' by Wikibooks is licensed under CC BY-SA 3.0 / Original sentence separated into numbered points Title? 'What are Control Systems?' Author? Wikibooks – linked to profile page Source? 'What are Control Systems?' – linked to original source page License? CC BY-SA 3.0 – linked to license deed Modification? Original sentence separated into numbered points