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.

A TTY (teletypewriter) is a device that helps people who are deaf, speech-impaired, or hard-of-hearing use a phone to communicate. While TTY devices were initially designed for landline phones, they are used today with both landlines and cell phones.