TTY, also known as Text Telephone Device or Telecommunication Device for the Deaf (TDD), is a special device required at both ends of the conversation that enables people who are deaf, hard of hearing, or speech-impaired to use the telephone to communicate. TTY works by allowing people to type messages back and forth to one another instead of talking and listening.
don't bother, it would only work when dialing another TTY enabled telephone number. Basically what it does is work like an old dial-up modem works by sending the information over a standard telephone signal, to just send textual information. Yeah, it's essentially texting, but you can't just go and text anyone you want, because technically it still isn't texting. Overall, if you're not deaf or don't actively communicate with deaf people, and don't actually have any other need to use it, don't bother trying to use it