What Is TTY Mode on Cell Phones?

By Dan Stone

Cellular phones have all sorts of accessibility features that can make the device easier and more practical to use. TTY Mode, also known as Text Telephone or Teletypewriter for the Deaf, is one accessibility feature designed to help people who are deaf, hard-of-hearing or speech impaired communicate over a phone call. When a phone uses TTY Mode, it behaves similarly to how it does when sending and receiving text messages, except it uses an actual phone call connection to transfer data.

About TTY Devices

While smartphones and cellular phones can carry TTY information over the phone network, the phones themselves are not TTY devices. When the phone is in TTY mode, it is compatible with TTY devices using an adapter or audio in/out connector. The TTY device is a terminal that includes a keyboard and a text display mechanism. The data sending TTY device digitally encodes the text and transmits the information over the phone line with a modem. The receiving TTY device decodes the message and displays the text. Some TTY devices have a built-in phone whereas others are designed to dock with an existing phone.

Turning on TTY

A wide range of cellular phones feature TTY mode; however, it is not turned on by default and the option's menu location varies between devices. Generally, you can find the TTY mode toggle in the device's settings menu. You can enable TTY mode on an iPhone by opening the "Settings" menu, selecting "Phone" and sliding the switch next to TTY to the on position. On some Android devices you can enable by opening the "Settings" app, selecting "My Device," choosing "Call," tapping "TTY mode" and selecting the TTY mode. You can enable TTY on other Android devices by opening the phone app, tapping the options icon, choosing "Settings," selecting "Call," tapping "Additional Settings," pressing "TTY Mode" and selecting the TTY mode.

Starting a TTY Call

To start a call over TTY on a cellular phone with TTY enabled, connect the phone to the TTY device and call the other number with the phone, just as in a normal phone call. Once the phone has established the connection with the other line the TTY devices can begin communicating with each other. Both devices used in the phone call need to support TTY for the service to work.

TTY Related Services and Uses

TTY Relay Services allow people with TTY devices to call people without TTY devices by dialing 711. Relay services work by having an operator read aloud the text sent from the TTY device user and typing what the non-TTY device user says. TTY devices are still relevant even with text messaging because they work with emergency services like 911, which may not be able to receive text messages. The American Speech-Language-Hearing Association recommends TTY devices as a communication alternative for people who have hearing aids to work around feedback caused by the hearing aid getting too close to the phone.