A TTY (Text Telephone) modem or sometimes referred to as a TDD (Telecommunication Device for the Deaf) modem is a special device that lets people who are deaf, hard of hearing, or speech-impaired use the telephone to communicate. This is accomplished by allowing them to type messages back and forth to one another instead of talking and listening. A TTY is required at both ends of the conversation in order to communicate directly. To use a TTY, you set a telephone handset onto special acoustic cups built into the TTY (some TTY models can be plugged directly into a telephone line). Then, type the message you want to send on the keyboard of the TTY. As you type, the message is sent over the phone line, just like your voice would be sent over the phone line if you talked. You can read the other person's response on the text display of the TTY.
If you don't have a TTY, you can still call a person who is deaf, hard of hearing, or speech-impaired by using the Telecommunications Relay Service (TRS). With TRS, a special operator types whatever you say so that the person you are calling can read your words on his or her TTY display. He or she will type back a response, which the TRS operator will read aloud for you to hear over the phone. Toll free TRS services are available 24 hours a day, 365 days a year.
