Telephone Relay Systems make it possible for the hearing impaired, and the speech impaired, to converse by telephone. State governments establish and fund the services, which are provided via Relay Centers and managed by telecommunications companies on a contractual basis. System users must have a keyboard equipped with a Teletypewriter, called TTY (T-T-Y), or a Telecommunications Device for the Deaf, known as TDD (T-D-D). The user first dials an 800-number at the Relay Center, where a calling assistant calls the person with whom the system user wishes to communicate. Then the user types a message onto the keyboard, which the calling assistant receives and voices to the called party. In turn, the calling assistant types the called party's voice response back to the caller. People who can hear also may use the system by dialing the 800-number and telling the CA (C-A) the area code, telephone number and name of the person they want to reach. As the conversation is being relayed, the non-system user talks as though speaking directly to the system user. The Relay Service shouldn't be used to call from one relay service to another. Those calls may be dialed directly without the assistance of the Relay Center. For more information about Telephone Relay Systems, contact a hearing professional.