Hearing-impaired people use devices called TTYs, or tele-typewriters, to make and receive calls on their home phones. The conversations are similar to the millions of exchanges that take place every day between users of instant messaging applications. The letters typed into the machine are turned into electrical signals. When the signals reach their destination, they are converted back into letters, which appear on a display screen.
TTYs continue to work on most of today's landline telephone networks, which use analog equipment to convert sound into electricity. However, the estimated 4 million TTY customers can't use the same devices when coupled with a cell phone, which uses a digital network to ferry calls and data.
The Federal Communications Commission gave wireless carriers untilto make it possible for the hearing impaired to use a cell phone and a TTY. The carriers will be subject to disciplinary action if they miss the deadline; the commission will determine fines.
On Wednesday, Sprint PCS said it has begun offering that capability, free of charge, on its network. Representatives for three other wireless carriers--AT&T Wireless, Verizon Wireless and Cingular Wireless--all expressed confidence Wednesday that they would meet the upcoming deadline. Other carriers could not be immediately reached for comment.
"We're actually a little bit ahead of the game," said Amy Schiska, a Sprint PCS spokeswoman.
To use the Sprint PCS service, the hearing impaired have to buy special phones. The Sprint PCS lineup includes a half-dozen phones ranging in price from $100 to $300, according to a Sprint PCS spokesman. They will also have to buy mobile versions of a TTY, the spokesman said.
Judy Harkins, professor of communication studies at Gallaudet University in Washington, D.C., said the technology needed to meet the mandate breaks up the TTY signals into ones the digital networks can understand. Once the signals travel across the cellular carriers' networks, they are "unmasked" and returned to the signals the TTY can understand, she said.
Many hearing-impaired people use some form of wireless device capable of sending and receiving text, such as Research In Motion pagers. But they have proven to be a less-than-adequate substitute, Harkins said, particularly when trying to reach emergency services such as police or fire personnel.
"Pagers can't call 911," she said.