As an iPhone user, you may have noticed the "TTY" option in the settings menu. Whether you realise it or not, this is a very important accessibility feature that allows hearing-impaired individuals to use their iPhones to communicate with others. Even if you don't think you'll ever need it, it is important to understand how it works.
TTY, or Text Telephone, is an accessibility feature that allows deaf and hearing-impaired individuals to use the telephone. With TTY, users at both ends use a special TTY machine to type messages back and forth. These messages are sent over the phone lines just like sound, allowing both parties to communicate effectively. To use TTY, each person must have a TTY machine connected to his phone.
TTY is an important iPhone feature because it makes it possible for deaf and hearing-impaired users to use the iPhone with their TTY equipment. Without the TTY feature, individuals with hearing disabilities would not be able to use the iPhone effectively. To connect the iPhone to a TTY machine, users must purchase an Apple iPhone TTY adaptor, which connects the two devices with a single cable.
To activate TTY on an iPhone, you must turn the feature on by swiping the on/off switch beside "TTY" in the Settings menu. The option is not located with the other accessibility features, and is instead located under the "Phone" heading. After turning on TTY on your iPhone, you can connect your phone to your TTY equipment and begin using the service.
You can't begin using TTY on your iPhone until you have a TTY machine. These machines have a keyboard so you can type your message to the recipient at the other end of the phone line. This equipment is necessary for all TTY users -- whether or not they have a hearing impairment. If you are not hearing-impaired and want to communicate with a hearing-impaired, TTY user, you must use the Telecommunications Relay Service. This toll-free service allows you to "speak" through a TTY-trained operator who will transcribe your message and relay messages back to you.