Text telephones, also known as TTY (teletypewriter) devices, are specialized communication tools designed for individuals who are deaf or hard of hearing. They allow users to send and receive text messages over telephone lines, enabling real-time conversations. Users type their messages on a keyboard, and the text is transmitted to the other party's TTY device. These devices often include features like a display screen for reading incoming messages and a built-in printer for hard copies. TTY technology has been largely supplemented by modern alternatives, such as video relay services and text messaging, but it remains an important tool for accessible communication.