TTY stands for "TeleTYpewriter."
A teletypewriter is basically a keyboard with a small screen and a
couple of cups that the ends of an (old fashioned) phone handset
sets down into.
It is occasionally called a TDD, which stands for "Telecommunication
device for the Deaf."
Some government types tried to call it a TT (text telephone) for a while, but
it never caught on. (chuckle)
But here in the Deaf community, we call it a TTY.
TTY
For more information see the TTY
discussion page.
You can learn
American Sign Language (ASL) online at American Sign Language University ™
ASL resources by Lifeprint.com © Dr. William Vicars