What is the primary purpose of a TTY device?

The primary purpose of a TTY (Text Telephone or Teletypewriter) device is to facilitate communication for individuals who are hearing impaired. TTY devices allow users to send and receive text messages over phone lines, enabling those who cannot hear to communicate effectively with others via traditional phone services. This technology was developed to bridge communication gaps for the deaf and hard-of-hearing community, ensuring they have equal access to telephone communication.

In contrast to the other options, a TTY is specifically designed for text communication rather than audio playback for the visually impaired or as a relay for emergency information. While it can also serve as a backup for traditional phones in some contexts, its primary function remains centered around providing a means for hearing-impaired users to communicate through text.