How to use TTY mode on iOS and Android

“Teletypewriter” (TTY) or “Text Telephone” mode, also called Telecommunications Device for the Deaf (TDD), is an integrated text-to-audio communication system designed specifically for people who are deaf, hard of hearing, or have a speech impairment so they can still make and receive regular phone calls.

Through a TTY relay service, TTY only works on a TTY-compatible device by displaying typed messages back and forth on screen over a phone line instead of speaking. Many modern smartphones, including latest iOS and Android phones, have this feature built inside them.

The live practical is as when you type your message, a relay operator reads it aloud to the hearing person on the other end, and types back their spoken reply for you to read. However, you should not mistakes it for Real-Time Text (RTT) mode because they're a little bit different. RTT transmits text character-by-character during an active call.

Meanwhile, you have to manually activate TTY on your smartphone app and if you wish to connect it to any dedicated hardware devices with a keyboard, your phone will serve as the display screen while the external hardware is featuring a small display. But it's important to note that modern smartphones built with TTY are designed to eliminates the reliance on a landline and external hardwares.

What is needed to use TTY on phone

Here are things that must be put in place to use TTY and these things are what set TTY apart from RTT because no hardware is needed to use RTT, it sends characters instantly as you type them. But for TTY to work properly on a smartphone, your smartphone must have an in-built feature that supports the TTY, a service provider that supports the feature, and a headphone jack for hearing.

An old physical TTY machine

TTY machines are computers built to feature a keyboard and a visual text display screen. You can also connect your smartphone to either a specialized external TTY machine or a digital relay service but that's not compulsory because modern smartphones now have everything it takes to use TTY, including display screen, keyboard, speaker (or headphone), and a standard landline, digital VoIP line, or a compatible mobile network.

However, it's important to note that if your TTY machine doesn't have support for Bluetooth, then you'll be needing an adapter to connect your phone to the machine. If the TTY device is physically plugged into your phone (via the adapter), the software side is simple. All you need to do is just go-to your phone settings, under accessibility, and turn on TTY mode in the settings.

How to activate TTY

Follow these steps to manually activate Text Telephone on your phone:

Android

• Open your phone “Settings” and go-to “Accessibility.” In some Android phone, you may not see the accessibility settings directly on the settings page, all you need to do is just use the search bar to search for it. 
  
• Under accessibility, look for Text Telephone or related wordings. On my phone, it's regarded as “Text-To-Speech Output.” 
  
• You can begin setting up to your preference by adjusting the sliders. You can tap “Play” to see how it'll look in real-time and you can use the reset button to start all over again. 
  
• To activate the TTY, tap the settings icon at the top right corner and toggle the buttons based on your preferences. 
  
• You can use the “Install voice data” to select your preferred language. You can toggle on “Use Wi-Fi only” to use the Google TTS options, and you can also choose between off, conservative, and aggressive as option for “Language Detection.”

iOS

The iPhone TTY activation is very straightforward. Unlike Android that the procedure vary across phone brands, all you need to do on an iPhone is just to open the iPhone Settings app, navigate to Accessibility, select “RTT/TTY”, and toggle on the Software or Hardware options. Once turned on, you can start customizing your settings as by tapping Relay Number to change the default 711 operator number.

You can also toggle on “Send Immediately” if you want characters transmitted as you type them rather than after you finish a message. You can as well turn on “Answer All Calls” so incoming calls are automatically accepted as RTT/TTY.

Meanwhile, if you're to be setting up your TTY using the Hardware Connection, plugging in an external TTY machine using an official Apple headphone adapter will be very much needed.

Final Notes

Once TTY mode is activated, the text content of your call will be displayed on your screen. The other person doesn't need (or mandatory) to have TTY enabled on their end, the TTY users can simply place the calls through telecommunications relay services, where a communication assistant relays text to voice or voice to text as needed.

Here are some TTY options:

Option	What It Means	Best Suited For
TTY Full	Both caller and recipient communicate through text, either via a TTY device or a telecommunications relay service operator	People who find it difficult to hear and speak (the Deafs).
TTY HCO (Hearing Carry Over)	The user listens directly to the caller's natural voice but replies via text using the TTY setup	people who can hear properly but have difficulty speaking
TTY VCO (Voice Carry Over)	The user speaks normally, and the recipient's response comes back as text on the display	People who can speak but have difficulty hearing
TTY Off	Default setting; disables TTY mode and treats the call as standard audio-to-audio communication	People who don't need TTY assistance.

Notably, many TTY feature will see today in modern smartphones are regarded as RTT. The legacy TTY machine is old and the protocol is what is integrated into today's digital landscape. You can still experience the legacy TTY by connecting your TTY-enabled device to a TTT hardware.

There's also another option called the “Video Relay Services.” These services are also a good option that allows the primarily usage of sign languages to communicate. The good part of it is that each call you make through the platform remains encrypted, also depends on the platform you're using to make the call.