Samsung SGH-S275DAATFN - Manual (Page 119)

Health and Safety Information 114
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 added together to indicate how usable they are
together. For example, if a hearing aid meets the M2 level rating and
the wireless mobile device meets the M3 level rating, the sum of the
two values equals M5.
Under the standard, this should provide the hearing aid user with
normal use while using the hearing aid with the particular wireless
mobile device. A sum of 6 or more would indicate excellent
performance.
However, these are not guarantees that all users will be satisfied. T
ratings work similarly.