GreatCall Jitterbug5 User Manual page 190

interference, you may not be able to use a rated mobile device successfully.
Trying out the mobile device with your hearing device is the best way to evaluate
it for your personal needs.
M-Ratings: Wireless mobile devices rated M3 or M4 meet FCC requirements and
are likely to generate less interference to hearing devices than mobile devices
that are not labeled. M4 is the better/higher of the two ratings. M-ratings refer
to enabling acoustic coupling with hearing aids that do not operate in telecoil
mode.
T-Ratings: Mobile devices rated T3 or T4 meet FCC requirements and are likely
to generate less interference to hearing devices than mobile devices that are
not labeled. T4 is the better/higher of the two ratings. T-ratings refer to enabling
inductive coupling with hearing aids operating in telecoil mode.
Hearing devices may also be rated. Your hearing aid manufacturer or hearing
health professional may help you find this rating. Higher ratings mean that the
hearing device is relatively immune to interference noise.
Under the current industry standard, American National Standards Institute
(ANSI) C63.19, the hearing aid and wireless mobile device rating values are
Health and Safety 181