47 CFR §68.316

A telephone handset is hearing aid compatible for the purposes of this section if it complies with the following standard, published by the Telecommunications Industry Association, copyright 1983, and reproduced by permission of the Telecommunications Industry Association: (A1) EIA Standard RS-464, Private Branch Exchange (PBX) Switching Equipment for Voiceband Applications. (A2) EIA Standard RS-478, Multi-Line Key Telephone Systems (KTS) for Voiceband Applications. (A3) EIA Standard RS-470, Telephone Instruments with Loop Signaling for Voiceband Applications. (A4) EIA Project Number PN-1361, Environmental and Safety Considerations for Voice Telephone Terminals. (A5) Federal Communications Commission Rules and Regulations, part 68, Connection of Terminal Equipment to the Telephone Network. (A6) IEEE Standard, Method for Measuring the Magnetic Field arould a Telephone Receiver. (to be published)