Verizon eTalk Manual page 15

Real-time text (RTT) information
Real-time text (RTT) is a feature that can make it easier for customers
with hearing or speech impairments to carry on a conversation through
text. RTT is available on eTalk.
With standard text messaging, you have to compose an entire message,
hit Send and then wait for a reply. But with real-time text, each character
is transmitted immediately as it's typed. So it's as if you're having a
conversation "in real time." Since there's no delay between sending and
receiving messages, and because you can talk and text simultaneously
over the same connection, RTT can feel like a more natural form of
communication than TTY or text messaging.
Unlike TTY, there's no need for a separate device. As long as your Verizon
Wireless phone supports RTT, you can send and receive real-time text
using only your smartphone. (Note: lf the person you're calling does not
have RTT or TTY enabled on their device, the call will be voice only.)
Hearing aid compatibility information
This phone has been tested and rated for use with hearing aids for some
of the wireless technologies that it uses. However, there may be some
newer wireless technologies used in this phone that have not been tested
yet for use with hearing aids. It is important to try the different features of
this phone thoroughly and in different locations, using your hearing aid or
cochlear implant, to determine if you hear any interfering noise. Consult
your service provider or the manufacturer of this phone for information on
hearing aid compatibility. If you have questions about return or exchange
policies, consult your service provider or phone retailer.