47 USC 610 - Telephone service for disabled

(a) Establishment of regulations 
The Commission shall establish such regulations as are necessary to ensure reasonable access to telephone service by persons with impaired hearing.
(b) Hearing aid compatibility requirements 

(1) Except as provided in paragraphs (2) and (3), the Commission shall require that
(A) all essential telephones, and

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(B) all telephones manufactured in the United States (other than for export) more than one year after August 16, 1988, or imported for use in the United States more than one year after August 16, 1988,

provide internal means for effective use with hearing aids that are designed to be compatible with telephones which meet established technical standards for hearing aid compatibility.

(A) The initial regulations prescribed by the Commission under paragraph (1) of this subsection after August 16, 1988, shall exempt from the requirements established pursuant to paragraph (1)(B) of this subsection only
(i) telephones used with public mobile services;
(ii) telephones used with private radio services;
(iii) cordless telephones; and
(iv) secure telephones.
(B) The exemption provided by such regulations for cordless telephones shall not apply with respect to cordless telephones manufactured or imported more than three years after August 16, 1988.
(C) The Commission shall periodically assess the appropriateness of continuing in effect the exemptions provided by such regulations for telephones used with public mobile services and telephones used with private radio services. The Commission shall revoke or otherwise limit any such exemption if the Commission determines that
(i) such revocation or limitation is in the public interest;

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(ii) continuation of the exemption without such revocation or limitation would have an adverse effect on hearing-impaired individuals;
(iii) compliance with the requirements of paragraph (1)(B) is technologically feasible for the telephones to which the exemption applies; and
(iv) compliance with the requirements of paragraph (1)(B) would not increase costs to such an extent that the telephones to which the exemption applies could not be successfully marketed.
(3) The Commission may, upon the application of any interested person, initiate a proceeding to waive the requirements of paragraph (1)(B) of this subsection with respect to new telephones, or telephones associated with a new technology or service. The Commission shall not grant such a waiver unless the Commission determines, on the basis of evidence in the record of such proceeding, that such telephones, or such technology or service, are in the public interest, and that
(A)  compliance with the requirements of paragraph (1)(B) is technologically infeasible, or
(B)  compliance with such requirements would increase the costs of the telephones, or of the technology or service, to such an extent that such telephones, technology, or service could not be successfully marketed. In any proceeding under this paragraph to grant a waiver from the requirements of paragraph (1)(B), the Commission shall consider the effect on hearing-impaired individuals of granting the waiver. The Commission shall periodically review and determine the continuing need for any waiver granted pursuant to this paragraph.
(4) For purposes of this subsection
(A) the term essential telephones means only coin-operated telephones, telephones provided for emergency use, and other telephones frequently needed for use by persons using such hearing aids;
(B) the term public mobile services means air-to-ground radiotelephone services, cellular radio telecommunications services, offshore radio, rural radio service, public land mobile telephone service, and other common carrier radio communication services covered by part 22 of title 47 of the Code of Federal Regulations;
(C) the term private radio services means private land mobile radio services and other communications services characterized by the Commission in its rules as private radio services; and
(D) the term secure telephones means telephones that are approved by the United States Government for the transmission of classified or sensitive voice communications.
(c) Technical standards 
The Commission shall establish or approve such technical standards as are required to enforce this section.
(d) Labeling of packaging materials for equipment 
The Commission shall establish such requirements for the labeling of packaging materials for equipment as are needed to provide adequate information to consumers on the compatibility between telephones and hearing aids.
(e) Costs and benefits; encouragement of use of currently available technology 
In any rulemaking to implement the provisions of this section, the Commission shall specifically consider the costs and benefits to all telephone users, including persons with and without hearing impairments. The Commission shall ensure that regulations adopted to implement this section encourage the use of currently available technology and do not discourage or impair the development of improved technology.
(f) Periodic review of regulations; retrofitting 
The Commission shall periodically review the regulations established pursuant to this section. Except for coin-operated telephones and telephones provided for emergency use, the Commission may not require the retrofitting of equipment to achieve the purposes of this section.
(g) Recovery of reasonable and prudent costs 
Any common carrier or connecting carrier may provide specialized terminal equipment needed by persons whose hearing, speech, vision, or mobility is impaired. The State commission may allow the carrier to recover in its tariffs for regulated service reasonable and prudent costs not charged directly to users of such equipment.
(h) State enforcement 
The Commission shall delegate to each State commission the authority to enforce within such State compliance with the specific regulations that the Commission issues under subsections (a) and (b) of this section, conditioned upon the adoption and enforcement of such regulations by the State commission.