| Source | IEC 63080:2017, 3.20, modified – In the definition, "communication and interpretation" replaced by "communication or interpretation", "based on observation of the mouth of the speaker" added and "are hard of hearing, or persons who are deaf who may or may not use sign language" replaced by "are deaf or hard of hearing, regardless of whether they use sign language" for conformity with Recommendation ITU-T F.791:2018, 3.21. |