Final answer:
A TTY is a device that allows hearing-impaired individuals to communicate over the telephone.
Step-by-step explanation:
A TTY (Text Telephone) is a device that allows hearing-impaired individuals to communicate over the telephone.
It contains a keyboard or a similar input device, a display, and a modem. The person using the TTY types a conversation, which is then transmitted as text to a receiving TTY. The receiving TTY converts the text back into sound, which can be heard by the receiving party on the other end of the phone call.
Therefore, the statement that a TTY is a device for hearing-impaired patients is true.