The teletypewriter (TTY), invented in 1964, allowed deaf individuals to communicate over the phone network by transmitting text messages. TTYs used a modified Baudot code to encode characters and were later supported by relay services, where operators facilitated communication between TTY users and those with regular telephones. While TTY technology is less prevalent today due to advancements like SMS and the internet, it played a crucial role in improving accessibility for the deaf and hard of hearing community.