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What is a TTY Phone?
Deaf / HoH

What is a TTY Phone?


Despite the emergence of instant messaging and text-based delivery apps, much of our daily lives are still dependent on phone calls. For the deaf community, this poses an obvious problem: voice-based communication systems are not an option for everybody.

Fortunately, communication problems can usually be fixed with a little bit of technology. That said, teletypewriters or TTY phones allow text-based messages to be sent via the phone line which is especially helpful for people with hearing impairments.

A Little Background on TTY

A TTY device or Text Telephone, originally developed for typewriter users, allows the transmission of text-based messages along phone lines – essentially, a precursor to modern-day text messages for landlines.

The system is equipped with a QWERTY keyboard and a small screen. Depending on the model, this may be hooked directly to the phone line or attached to a normal handset through a small acoustic cup (usually located at the side).

For individuals to send text messages back and forth, you will need a TTY at both destinations so each party can read what the other has written. Because most people who are not hearing-impaired do not have a TTY at home, some other alternatives have been developed.

Upgrades to TTY Phones

There are two main methods that bridge the gap between traditional phones and TTY devices.

First came TRS or Telecommunications Relay Service. Often provided by Ultratec, the original developers of TTYs, this type of service relies on a human operator who reads all incoming text messages to the receiver who doesn’t have a TTY. In addition, they also type all verbal responses to be read by the hearing impaired party.

Nowadays, text-to-speech technologies have improved significantly. This has led to the creation of CapTel technology. A CapTel, or Captioned Phone, offers a combination of text and voice-based communication, all in one device.

These are traditional phones with an attached screen, which converts all incoming spoken words into easily readable chunks of texts. These are approximately the same size as TV subtitles and often slide down the screen at a similar speed. CapTels are generally the first-line recommendation for people with partial hearing loss, who are able to talk back, but would either miss parts of the conversation or ask for repetition.

What Other Alternatives Are Out There?

In the U.S., hearing-impaired people can also access a variety of federally-funded relay services that can supplement or completely replace the need for a TTY phone.

Voice Carry Over Services (VCO)

This is a type of relay service that offers one-way captions. In this service, the tty phone for the deaf user can speak directly to the other person, but anything that is said back will be transformed into text by a communications assistant.

Speech-to-Speech Services (STS)

This foregoes text altogether and relies on a communications assistant to repeat everything said at a higher volume or a slower speed. Therefore, it is usually only effective for people who are mildly hearing impaired (hard of hearing).


This is an add-on service meant to improve normal TTY functions by automatically letting a call recipient know that they are getting a phone call from a hearing-impaired person. This keeps the recipient from simply hanging up, thinking they are getting prank-called or getting poor reception, which can be especially troublesome when calling 9-1-1 or any emergency service, where every minute is precious.

Each of these programs or technology require either an extra piece of equipment or a live communications assistant to help navigate the calls. This means that anything said or heard will be slightly delayed, and this delay is further compounded by call waiting times, typing speed, and many other factors.

For completely voice-free, instant emergency calls, Rescu offers a unique service: to contact first responders in your area and dispatch them immediately, with just a few taps of your fingers. It is easy to use and will shave minutes off 9-1-1 response times!

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