TTY stands for “teletypewriter.” It was initially developed for people with hearing or speech difficulties to communicate over traditional telephone networks. TTY devices translate typed text into electronic signals sent across the telephone network and retranslated to text at the other end.

TTY stands for TeleTYpewriter. It allows for people who are hard of hearing or deaf to receive and send text messages over phone lines. It works by converting tones to text that the receiver can understand. The sent text is then converted to tones and back again into a text.