AT&T yesterday accused T-Mobile and Sprint of violating federal rules that require wireless networks to be compatible with technology for people with hearing and speech disabilities.

AT&T says T-Mobile and Sprint began offering Wi-Fi calling on smartphones without seeking a waiver from the Federal Communications Commission's TTY (teletypewriter) rules. TTY devices for deaf and speech-impaired people can be used in conjunction with cell phones, and the FCC requires wireless networks to be able to transmit 911 calls made using TTY devices.

Although TTY devices do not operate reliably over Wi-Fi, T-Mobile and Sprint "have been offering Wi-Fi calling services for a significant period of time, well over a year on Android devices and for months on iOS devices," AT&T wrote in a letter yesterday to FCC Chairman Tom Wheeler. "Neither of those carriers has approached the FCC to request a waiver of the TTY rules" and are thus "offering those services in apparent violation of the Commission's rules."

AT&T is itself now seeking a temporary waiver of the rules in order to provide Wi-Fi calling. The waiver would be temporary because AT&T is preparing an RTT (real-time text) service to replace TTY and petitioned the FCC to amend its rules to allow RTT in place of TTY. But FCC decisions take time, and AT&T wants to be able to offer Wi-Fi calling in competition with Sprint and T-Mobile now. AT&T says it intended to offer Wi-Fi calling beginning on September 25, but wasn't able to.

"Because the Commission has not granted AT&T's waiver petition, we are not in a position to provide Wi-Fi calling services to our customers even while our competitors provide those services in defiance of the Commission's rules," AT&T wrote.

Sprint declined comment when contacted by Ars yesterday. T-Mobile hasn't responded. (UPDATE: T-Mobile told Ars that it "is in full compliance with the FCC rules and supports TTY," but did not say if it supports TTY on Wi-Fi calling. "We have no knowledge of the network configuration or planned service offerings that drove AT&T to seek the requested waiver," T-Mobile also said.)

An FCC spokesperson declined comment on AT&T's claim that T-Mobile and Sprint are violating the rules.

"It is true that providers of telecommunications, including VoIP and wireless, must make their service accessible to people with disabilities, including access to TTY," FCC spokesperson Mark Wigfield said. "We are reviewing AT&T’s request of a waiver of the TTY requirement, which, as I understand it, would be for the period until they can roll out a substitute technology."

T-Mobile has supported Wi-Fi calling since 2007 but has promoted it more heavily lately.

AT&T said in its letter to Wheeler that it has been trialing an RTT system that is superior to TTY and demonstrated it to "the disability community's advocacy groups, industry participants, and FCC staff."

Disability advocates want RTT to be implemented quickly, but "no one expressed opposition to a temporary waiver of existing TTY rules for the reasonable timeframe outlined in the waiver petition," AT&T wrote.

Consumer advocacy groups who work on behalf of deaf people told the FCC that they "generally support" AT&T's waiver request as long as it's limited in duration. The groups praised AT&T's efforts to advance RTT technology, saying that it will maintain the ability to transmit text character by character, "allowing for conversational, real-time communication," but without suffering "the reliability and transmission issues that impact TTY when operating on an IP network."

TTY allows deaf and speech-impaired people to type messages to each other over the phone network, using devices with keyboards. For calls between a disabled person and a non-disabled person, a Telecommunications Relay Service (TRS) operator "relay[s] the text of the calling party in voice to the called party, and convert[s] to text what the called party voices back to the calling party," according to the FCC.

Many TTY users have switched to newer technologies, but TTY is "still used by many people who are deaf or hard of hearing; particularly by people who do not have access to available, affordable broadband and Internet access," according to the National Association of the Deaf. "TTYs also continue to play an important role by providing direct access to 9-1-1 emergency services."

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