A Telecommunications Device for the Deaf (TDD), also known as a Text Telephone (TTY), is a device that allows individuals who are deaf or hard of hearing to communicate over the phone using text. Users type their messages on a keyboard, and the device converts the text into signals that can be transmitted over telephone lines. The receiving party can read the messages on their own TDD or a standard phone if they have access to a relay service. TDDs have been essential in promoting accessibility and inclusion for the deaf community. They enable users to communicate with hearing individuals through a relay operator, who reads the typed messages aloud and types back the spoken responses. This technology has evolved over the years, paving the way for modern communication methods like video relay services and instant messaging.