The Telecommunication Device for the Deaf (TDD), also known as a TTY (Text Telephone), 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 transmits the text to another TDD or a relay service, which converts the text to voice for hearing individuals. TDDs are equipped with a display screen that shows the typed messages, making it easier for users to read and respond. This technology has significantly improved accessibility for the deaf community, enabling them to connect with others and access services that rely on telephone communication.