ʌntˈɪl ðɪ ˈɜːli twˈɛntifˈɜːst sˈɛntʃɚɹi, ðɛɹ jˈuːs wʌz lˈɪmɪɾᵻd baɪ ðə kəmplˈɛksᵻɾi ʌv dɪzˈaɪnɪŋ ænd kəntɹˈoʊlɪŋ ðˌɛm.
Until the early twenty-first century, their use was limited by the complexity of designing and controlling them.