TTY (Teletype), also known as TDD (Telecommunications Device for the Deaf), is a communication tool designed for individuals who are deaf, hard of hearing, or have speech impairments. It allows users to send and receive typed messages over traditional telephone lines. The basic components include a keyboard for typing and a screen or printer to display incoming messages. Communication happens in real time, typically with each person taking turns to type and read.
The technology works by converting typed characters into audio tones that travel across phone lines to another TTY device. The receiving device decodes these tones and displays the message. For calls between a TTY user and someone without a TTY, a relay service can be used. In this case, an operator reads the typed message aloud to the hearing person and types back their spoken response for the TTY user.
TTYs have been in use since the 1960s and were a breakthrough in accessible communication. Though many users now prefer newer options like text messaging, video relay services, or real-time text (RTT), TTY remains relevant in some settings. Federal regulations, such as the Americans with Disabilities Act (ADA), still require support for TTY on many business phone systems to maintain accessibility compliance.
For businesses, especially those in healthcare, government services, or customer support, TTY compatibility ensures communication remains accessible to all users. Maintaining TTY support is often a part of broader compliance strategies and reflects a commitment to serving diverse communication needs.
TTY technology originated in the 1960s as a solution to bridge communication gaps for individuals who are deaf or hard of hearing. The early systems adapted mechanical teletype machines, originally used by news services and military operations, to function over standard telephone lines. This innovation gave the Deaf community a new way to communicate independently and directly.
One of the key pioneers in this space was Robert Weitbrecht, a deaf scientist who developed an acoustic coupler that allowed teletypewriters to connect to regular telephones. His invention laid the foundation for TTY as a consumer-accessible tool. By the 1970s and 1980s, TTY devices became more compact, affordable, and widely used in homes, schools, and government offices.
As the technology matured, relay services were introduced. These allowed TTY users to communicate with people who didn’t have a TTY device. A specially trained operator would serve as a bridge, reading typed messages aloud and typing spoken responses. This service greatly expanded communication possibilities and was later mandated by the ADA in 1990.
In recent years, advances in digital communication—such as SMS, email, video calling, and RTT—have largely replaced TTY for most users. However, TTY support remains embedded in many business and government systems to meet legal requirements and to serve users who still rely on the technology. While its usage has declined, TTY continues to represent a key milestone in accessible communication.
TTY devices communicate by sending and receiving text over traditional telephone lines. Each device includes a keyboard for typing messages and either a screen or a small printer to display the incoming text. The process happens in real time, meaning users take turns typing and reading, much like a text-based conversation.
When a user types a message, the TTY converts each character into a series of audio tones. These tones are transmitted over the phone line to the receiving TTY. The receiving device decodes the tones and converts them back into text that the user can read.
For calls between a TTY user and someone without a TTY device, a relay service can be used. In this setup, the TTY user connects to a trained operator through a relay center. The operator reads the typed message aloud to the hearing person, then listens to the spoken response and types it back to the TTY user.
TTY communication relies on a standardized protocol known as Baudot, which uses specific tone patterns to represent letters, numbers, and punctuation. Though slower than modern texting, this system has proven reliable over traditional phone networks and continues to function on many legacy systems.
To initiate a TTY call, both users must have access to compatible equipment, or use relay services. Most modern business phone systems include TTY support features, such as TTY-compatible handsets or settings that enable tone transmission. This keeps the system accessible for those who still rely on the technology.
TTY technology plays a key role in meeting accessibility standards for businesses and service providers. Under the Americans with Disabilities Act (ADA), organizations that offer phone-based services are required to provide equivalent access for individuals who are deaf, hard of hearing, or speech-impaired. TTY is one of the approved methods to meet this requirement.
The ADA mandates that public and private entities offering telephone communication must be reachable through TTY or a relay service. This applies to sectors like healthcare, government, education, financial services, and any business with customer-facing phone systems. Not meeting these requirements can lead to non-compliance penalties and limit access for a portion of the population.
Telecommunications Relay Services (TRS), funded and regulated by the Federal Communications Commission (FCC), were created to support TTY users. TRS centers use trained operators to relay messages between TTY users and standard phone users. These services must be available 24/7, at no extra cost to the user.
While newer tools like real-time text (RTT) and video relay services are gaining ground, TTY remains a recognized and supported method under current federal regulations. For this reason, many phone systems—especially in healthcare, government, and public-facing businesses—maintain TTY compatibility as part of their accessibility and compliance frameworks.