Casio GzOne User Manual page 186

How will I know if my hearing aid will work with a
particular digital wireless phone?
You'll want to try a number of wireless phones so that you can decide
which works the best with your hearing aids.
You may also want to talk with your hearing aid professional about the
extent to which your hearing aids are immune to interference, if they
have wireless phone shielding, and whether your hearing aid has a
HAC rating.
For more information about hearing aids and digital wireless
phones:
• FCC Hearing Aid Compatibility and Volume Control
http://www.fcc.gov/cgb/dro/hearing.html
• Hearing Loss Association of America
http://www.hearingloss.org/learn/cellphonetech.asp
• CTIA
http://www.accesswireless.org/hearingaid/
• Gallaudet University, RERC
http://tap.gallaudet.edu/voice
Teletypewriter (TTY) Devices
You can use an optional teletypewriter (TTY) device with your phone
to send and receive calls. You must plug the TTY device into the
phone's headset connector and set the phone to operate in one of
three TTY modes.
A TTY is a communication device used by people who are hard of
hearing or have a speech impairment. TTY does not work from mobile
phone to mobile phone. Use a TSB-121 compliant cable (provided
by the TTY manufacturer) to connect the TTY device to your phone.
Your phone has a 2.5mm jack. Set the phone to Medium volume level
for proper operation. If you experience a high number of incorrect
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