A TTY is a telephone which is specially outfitted for users who are deaf or hard of hearing. The “TTY” stands for “teletypewriter,” and the term is sometimes used to describe teletypes in general. TTY systems allow people who are deaf and hard of hearing to make calls to each other, and with the assistance of relay systems, users can also communicate with people who do not have TTY systems.

Essentially, a TTY system allows the user to place a phone call and then communicate through written text, rather than spoken communication. TTY systems include a telephone handset which is attached to a keyboard; each key makes a specific tone which can be read by the handset. The handset communicates those tones to a receiver on the other end of the line, and the receiver interprets the tones and generates a line of text.

Obviously, when someone places a call with a TTY system, they need to be certain that the recipient also has TTY. If the recipient has no TTY receiver, he or she will pick up the phone and hear a series of tones. In a situation where someone with a TTY system needs to call someone without one, or vice versa, a telephone relay service is used. The relay service can read typed messages to callers who can hear, and turn spoken messages into TTY text for deaf and hard of hearing callers.

Because most people can potentially speak much more quickly than they can type, TTY systems can be very clumsy. Frequent users typically develop a set of abbreviations, such as “GA” for “go ahead” to indicate that someone is done typing, or “sk” for “stop keying,” indicating that someone plans to end the conversation. People also heavily abbreviate words rather than writing them out to make the conversation go more quickly, and they tend to use TTY systems for quick communications rather than leisurely chats.

The main problem with TTY systems is that users must be able to type rapidly and accurately. Some deaf and hard of hearing users are also accustomed to using sign language, which has a different grammatical system than their written language. This can cause some confusion when using a TTY system. TTY systems also rely on things like flashing lights or vibration to alert deaf and hard of hearing users to incoming calls, and it is possible to miss a call if someone only lets the phone ring a few times, which can be very frustrating.