Feb19-TTY_TDD Blog Post Main Image

TTY and IVR: What You Need to Know

It’s critical for all people to be able to communicate with other. For non-hearing individuals there are several options that allow them to communicate with hearing people using traditional telephony infrastructure.

This post will briefly explain what TTY is and how it works. We’ll also discuss how IVR can accommodate the needs of non-hearing people.

TTY Hardware

A teletypewriter (TTY) or telecommunications device for the deaf (TDD) are devices that enable the deaf or hard-of-hearing to use a traditional telephone. These units first appeared in the late 1960s and resemble a computer that hooks up to the phone line. They have a keyboard for input and a screen to display messages.

At a basic level, these devices allow non-hearing people to send text messages to each other over the PSTN.

If non-hearing people need to communicate with hearing people, TTY devices allow them to do that as well – with a bit of extra help.

Telecommunications Relay Service

A telephone relay service is pretty straightforward. Individuals using a TTY device call a relay service where a hearing person using a TTY machine answers the call. The relay service assistant reads the messages from the non-hearing caller to the hearing caller. When the hearing caller responds, the assistant types the reply into the TTY machine and send them to the non-hearing caller.

In the United States, telephone relay services are mandated by the Americans with Disabilities Act. There is a national Telecommunications Relay Service (TRS) that operates 24/7/365, with support for both English and Spanish. Nowadays, the TRS can also handle communications over IP as well as the PSTN. Private relay services also exist.


Whether you’re a company that already offers TTY service or if you need to add TTY service to meet the needs a customer or vendor, you have options when it comes to IVR.

First of all, here at Plum our IVR technology does not integrate with TTY technology directly. For non-hearing individuals to use an IVR they would need to make use of a relay service. This in itself is not an issue. But if you have an IVR application already the issues that TTY/TRS callers will likely run into are time outs.

Because there is an inherent delay in TTY communications, the default caller response time threshold will time out before the right information is input. In order to accommodate TTY callers, you will need to lengthen the response time window.

You can easily do this with Plum Fuse by simply cloning your app and adjusting the timeout threshold in the appropriate modules.

Plum Voice customers can contact our 24/7 support line for additional questions when navigating IVR and TTY interfaces.

For more information, or to sign up for a free trial of our IVR development products, contact us today.