28 CFR Part 36 Nondiscrimination on the Basis of Disability by Public Accommodations and in Commercial Facilities NPRM (2008 Title III NPRM)

(ii) A public accommodation that offers a customer, client, patient, or participant the opportunity to make outgoing telephone calls on more than an incidental convenience basis shall make available, upon request, public telephones equipped with volume control mechanisms, hearing aid compatible telephones, or text telephones (TTYs) for the use of an individual who is deaf or hard of hearing, or has a speech impairment.