How Hearing Impaired Telephones Work

Concerts like this KROQ rock concert are one of the leading causes of hearing loss.
Concerts like this KROQ rock concert are one of the leading causes of hearing loss.
© Jeff Kravitz/Film Magic/Getty Images

Blame it on loud rock concerts, workplace noise or heredity, but for many people -- particularly Baby Boomers -- the sound coming through a telephone receiver has become a lot quieter. For others who are deaf or very hard of hearing, the challenge is finding a telecommunications system they can use to connect by phone with the hearing world.

Consider the numbers: About 30 percent of people over age 60 and 50 percent of those over age 85 have hearing loss. And an estimated 10 percent of younger Americans (ages 20 to 69) may have already had their hearing permanently damaged by excessive noise at work, at home or through leisure activities like woodworking, snowmobile riding or playing in a band [source: National Institute on Deafness and Other Communication Disorders].


No matter how severe hearing loss is, hearing-impaired telephones can make phone conversations more pleasant and productive. For example, a phone amplifier can boost the volume on a regular phone, clarify the sound a user hears and filter background noise.

A telecommunications device for the deaf (TDD), also known as a text telephone to telephone typewriter (TTY), can give these individuals the ability to talk with hearing friends and relatives, work effectively in the business world and make use of 800 numbers and other phone services. (A TDD is often called a textphone in Europe or a minicom in the United Kingdom.)

Telecommunications relay services, or telephone relay, connect TDDs to the telephone system. Newer variations -- such as Internet protocol (IP) relay, video relay service and IP captioned telephone service -- can even eliminate the need for a TDD by making use of a computer with Web access [source: Federal Communications Commission].

How do you find out what options are available? And how can you choose the right one? Let's start by seeing how sound amplifiers can help you hear better on a telephone.

How Telephone Amplifiers Work

People with hearing loss can get a special phone or a headset to help them hear on the phone.
People with hearing loss can get a special phone or a headset to help them hear on the phone.
© Thomas Northcut/Getty Images

If you've set the volume on your phone as high as it'll go and voices still sound faint, you may want to consider a device for hearing-impaired telephones called a phone amplifier. Several options are available, including units that attach to a phone line, portable amplifier units and dedicated amplifier telephones, as well as cell phone amplifier systems.

Here's how each of these phone amplifiers works.


Phone line units -- An amplifier like this connects between a phone's handset and base to increase volume. For example, the Ameriphone in-line phone amplifier, which costs about $35, can amplify sound by up to 40 decibels. Like other similar units, it also blocks out feedback and background noise and amplifies specific frequencies to make speech clear and similar-sounding words easy to distinguish. These units usually are small enough to be portable [source:].

Portable amplifier units -- These small devices are handy because you can take them with you to use on almost any landline phone. They are inexpensive ($20 to $30) and easy to attach to the headset without disconnecting and reconnecting phone lines. By turning a dial on the Reizen Portable Phone Amplifier, for example, you can increase volume by up to 30 decibels [source: Harris Communications].

Dedicated amplifier telephones -- Amplifier telephones with added features are available for corded or cordless landline phones. These phones allow you to increase volume by adjusting an amplification dial or button on the phone and, in some cases, also adding volume with a handset boost button.

The ClearSounds CSC50 amplified corded phone, for example, allows an increase of 50 decibels with 40 coming from the phone's amplification system and another 10 decibels from the handset. The $160 phone also offers caller ID and a speakerphone [source: Beltone].

Amplified cordless phones cost more, usually $180 to $280. At the low end, a Clarity amplified 2.4 GHz (gigahertz) cordless phone that costs $180 can amplify sound up to 30 decibels and comes with caller ID and a visual ringer. Additional handsets cost $100 each. A 5.8 GHz Clarity model that costs $280 amplifies sounds up to 50 decibels and adds multiband compression, noise reduction and acoustic echo cancellation [source:].

Another option to consider with a corded phone is an amplified handset that simply replaces the one that came with the phone. Ranging in price from about $50 to $150, amplified headsets like the Walker W60-K-M-00 may be less expensive than replacing the phone [source:].

But perhaps you're looking for a cell phone solution. One of the problems in developing cell phones for the hard of hearing has been that the radio frequency signal from cell phones can interfere with hearing aids, causing buzzing or other noise. However, hearing aids often come with a telephone coil, or T-switch, that acts like an antenna. When the switch is on, the magnetic signals pass from the phone to the hearing aid, allowing the user to receive the phone communication directly through the hearing aid.

Since 2005, the Federal Communications Commission (FCC) has required cell-phone companies to provide several models that are hearing aid compatible when used with the hearing aid on the microphone setting. The FCC also requires that cell phones be rated on a scale of 1 to 4 for the amount of interference they're likely to cause with hearing aids on M (microphone) and T (telephone coil) settings. Phones that are rated M3 or T3 (good) or M4 or T4 (excellent) can be sold as hearing aid compatible. Check for an icon on the phone or its packaging that show its M and T ratings [source:].

If amplification isn't enough, you may want to consider a TDD, TTY, text phone or minicom. Go to the next page to find out how TDDs work.

TTY and TDD Technology

Technology lets people with hearing problems make phone calls over their computer like in this early IBM version.
Technology lets people with hearing problems make phone calls over their computer like in this early IBM version.
© Somos/Veer/Getty Images

TTY technology gives the deaf and hard of hearing a text-based system for communicating over phone lines among themselves or with hearing individuals. Starting in the 1960s, hearing -impaired telephones that used this technology made the deaf and hearing impaired less isolated. Whether you call them TTYs, TDDs, textphones or minicoms, these devices now have four million U.S. users.

Here's how TTY works. The TTY unit itself resembles a laptop computer with a keyboard, a display screen and a modem. The user types his message, and the letters are converted into electrical signals that travel over the phone line. When the message reaches its destination, the signals are converted back into letters that appear on the receiving TTY unit's display screen or are printed out. A flashing light on the unit or a vibrating wristband alerts the recipient that a message has arrived. Some units also have answering machines [source:].


TTY owes its existence to a deaf scientist named Robert Weitbrecht. He developed an acoustic coupler in 1964 that allowed a TTY unit to be connected to a telephone. Early TTY units were large and cumbersome. By 1967, only 25 TTY stations were available, but by 1969 that number had increased to 600.

As electronic technology advanced, so did TTY. The units became smaller, less expensive and more readily available. TTY developers have used digital technology to bring computers and TTY units together. While TTY units are analog, software and a voice-capable modem with digital signal processing allow computers to talk directly to TTYs [source: Gallaudet University].

But changing technology has begun to threaten the existence of TTYs. E-mail, text messaging, instant messaging, e-paging and electronic faxing can be done from a computer with Internet access -- and without TTY. Add a Web camera and voice over Internet (VoIP) technology, and two deaf people can even sign to each other in real time.

With the arrival of BlackBerry mobile devices, iPhones and other smartphones, texting and IMing can be done almost anywhere. Picture phones with video allow signed messages to be recorded and sent, and vibrating phones make it easy for a deaf person to know when a message has arrived.

Is there still a place for TTY? Definitely among people who have used it for years and are more comfortable with it than with newer computer and mobile technology. And an argument can be made for keeping a simple TTY unit at home for emergencies. Like corded landline phones, TTYs rely on the telecommunications grid, rather than electricity, for power. So if electrical power is out in your area, you can still send and receive messages with your TTY unit.

Finding a TTY unit is easy. If you use a search engine like Google for the acronym "TTY," you'll see companies that sell these units for $250 to $600. Gallaudet University, which provides higher education for the deaf and hard of hearing, also provides a list of vendors of TTY unit, modem and software manufacturers.

With just TTY units and the phone system, people who are hard of hearing can communicate with each other. But using TTY to communicate with hearing individuals requires the use of the free Telecommunications Relay Service or related telephone relay services. Find out more on the next page.

How Relay Services Work

Relay services let callers use an assistant who transfers messages back and forth.
Relay services let callers use an assistant who transfers messages back and forth.
© Somos/Veer/Getty Images

If you don’t have a TTY unit or TDD, you can use a telephone relay service to communicate by phone with someone who is deaf or hard of hearing. Telephone relay services are required by the Americans with Disabilities Act, with services in English and Spanish, and regulated by the FCC. And while this variation on hearing-impaired telephones started as something like a translation service, variations like IP relay make more use of electronic technology.

The national Telecommunications Relay Service (TRS) is free and available 24 hours a day, seven days a week, to handle voice-to-TTY and TTY-to-voice calls. Various relay providers offer services in each state.


Here’s how the TRS works. The person placing the call accesses TRS from any TTY or standard phone by calling 7-1-1. The caller is connected to a communications assistant who relays communication between the caller and the recipient. A hearing caller, for example, speaks the message to the assistant, who types and relays it to the deaf recipient, who reads it on his TTY display screen. The recipient responds with a typed message, which the assistant reads to the hearing caller [sources: Occupational Safety and Health Administration and Gallaudet University].

The TRS can handle calls from computers via IP relay, as well as from TTYs. IP relay allows users to communicate using a computer and modem rather than a TTY unit. The IP relay starts with the caller’s computer or mobile device and goes to the IP relay center, which usually is accessed from a Web page.

There the call goes to a communication assistant, who sends the message on through the switched telephone system, converting it to either text or spoken word, depending on whether the recipient can hear. There is no extra charge for IP relay calls.

IP relay offers the advantage of being available through any device with Internet access. Also, transmission may be faster, and users can make multiple calls, have conference calls or browse the Web while on a call [source: FCC].

The newest addition is video relay service. It goes a step further by adding visuals to the conversation. This requires a high-speed Internet connection. Once that's established, a sign language interpreter reads the signed communication from the hard-of-hearing caller and speaks the message to the hearing recipient on the phone.

Gallaudet University provides information about both IP and video relay services.

For lots more information about hearing impaired telephones and related topics, check out the links on the next page.