Sharp ROUVO V Manual page 13

Using RTT or TTY
Real-time text (RTT) is a feature that can make it easier for
customers to carry on a live conversation through text (or text
and simultaneous voice) during a call, with each text character
transmitted immediately as it is typed. Unlike text telephony (TTY),
there's no need for a separate device. The person you are calling
must have either RTT or TTY enabled on their device for the text
capability to work.
If your device instead uses TTY and TDD (Telecommunications
Device for the Deaf) technology that allows similar text-based
communications by telephone, you must have a TTY-compatible
phone and be in the TTY mode to place or receive calls.
For additional information, visit the Verizon Accessibility Resource
Center at verizon.com/accessibility
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.