Most single phase alternating-current electrical outlets in the world supply power at 210–240 V or at 100–120 V. A transformer or autotransformer can be used; (auto)transformers are inherently reversible, so the same transformer can be used to step the voltage up, or step it down by the same ratio.
mˈoʊst sˈɪŋɡəl fˈeɪz ˈɔːltɚnˌeɪɾɪŋkˈɜːɹənt ᵻlˈɛktɹɪkəl ˈaʊtlɛts ɪnðə wˈɜːld səplˈaɪ pˈaʊɚɹ æt tˈuːhˈʌndɹɪd tˈɛn tˈuːhˈʌndɹɪd fˈoːɹɾi vˈiː ɔːɹ æt wˈʌnhˈʌndɹɪd wˈʌnhˈʌndɹɪd twˈɛnti vˈiː. ɐ tɹænsfˈoːɹmɚ ɔːɹ ˌɔːɾoʊtɹænsfˈoːɹmɚ kæn biː jˈuːzd; ˈɔːɾoʊ tɹænsfˈoːɹmɚz ɑːɹ ɪnhˈiəɹəntli ɹᵻvˈɜːsᵻbəl, sˌoʊ ðə sˈeɪm tɹænsfˈoːɹmɚ kæn biː jˈuːzd tə stˈɛp ðə vˈoʊltɪdʒ ˈʌp, ɔːɹ stˈɛp ɪt dˌaʊn baɪ ðə sˈeɪm ɹˈeɪʃɪˌoʊ.