B. How Does a TTY Work?
Before further discussion of the requirements for emergency communications services under Title II of the ADA, let’s do a quick review of how TTYs work. This information is important in order to understand this chapter’s discussion of equipment.
A TTY is a device that is used with a telephone to communicate with persons with hearing disabilities or speech disabilities. To communicate by TTY, a person types his or her conversation, which is then read on a TTY display or a computer display by the person who receives the call. Both parties must have a TTY or a computer with a TTY modem and related software to communicate. The computer equipment must be compatible with the code used by TTYs and capable of translating between the TTY code and the computer code.
Most TTY devices transmit the information typed through the telephone line in an electronic code called Baudot. When it reaches the receiving TTY, the code is translated back to characters. Computers with TTY modems generally operate in American Standard Code for Information Interexchange (ASCII), an electronic “language.” Thus, computers must have an ASCII/Baudot modem and related software in order to translate Baudot sent from TTYs.
9-1-1 or another number?
9-1-1 is a universal emergency number, but it may not be the number used in your area. If your locality has emergency communications services but uses different emergency numbers, such as a seven-digit number, you are still required to comply with Title II’s requirements for emergency communications.
The only real difference is the options for TTY users. Localities that use 9-1-1 are prohibited from requiring TTY users to call a different number.2 However, entities that do not use 9-1-1 may have a separate line for TTY users. If a separate line is used, access must be as direct as and equal to access for voice callers. Wherever the emergency numbers are listed, the TTY number must be listed as prominently as the voice number.
2 See Department of Justice Americans with Disabilities Act Title II Technical Assistance Manual II - 7.300 (1993). See www.ada.gov/taman2.html for the text of the Technical Assistance Manual.
When a standard TTY is used, communications can only occur in one direction at a time. In other words, the two people involved in the conversation must take turns sending and receiving. A person sending a communication by TTY indicates that he or she has finished transmitting by typing the letters “GA,” which stand for “go ahead.”
Baudot Format
I heard that there is more than one type of TTY code. Does Title II require that telephone emergency service systems be compatible with all codes used for TTY communications?
No. Currently, telephone emergency services must only be compatible with Baudot format.
How do you know when it’s a TTY call?
-
Some TTYs emit a recorded spoken announcement to the call taker that a TTY call is being received. For example, the announcement may state: “HEARING IMPAIRED CALLER. USE TTY.”
-
TTY callers may press TTY keys to emit audible tones and more quickly notify the call taker that a TTY call is being placed.
-
You may not know you have a TTY call unless you query the line with a TTY. Often, the TTY call will be perceived by the call taker as a silent, open line call. This is because the caller’s equipment does not recognize that the call has been answered until the call taker sends a TTY response.
A History of Hang-ups
Historically, many people who used TTYs have not had confidence in the accessibility of emergency communications services. Silent, open lines have commonly been treated as hangups even though silence may indicate there is a TTY caller on the line. The number of TTY calls each PSAP receives may increase over time because the ADA is making 9-1-1 and other emergency services more accessible to people who use TTYs.
User Comments/Questions
Add Comment/Question