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Safety
Hearing devices may also be
rated. Your hearing device
manufacturer or hearing health
professional may help you find
this rating. Higher ratings mean
that the hearing device is
relatively immune to interference
noise. The hearing aid and
wireless phone rating values are
then added together. A sum of 5
is considered acceptable for
normal use. A sum of 6 is
considered for best use.
In the above example, if a hearing
aid meets the M2 level rating
and the wireless phone meets
the M3 level rating, the sum of
the two values equal M5. This is
synonymous for T ratings. This
should provide the hearing aid
user with “normal usage” while
using their hearing aid with the
particular wireless phone.
“Normal usage” in this context is
defined as a signal quality that is
acceptable for normal operation.
The M mark is intended to be
synonymous with the U mark.
The T mark is intended to be
synonymous with the UT mark.
The M and T marks are
recommended by the Alliance for
Telecommunications Industries
Solutions (ATIS). The U and UT
marks are referenced in Section
20.19 of the FCC Rules. The
HAC rating and measurement
procedure are described in the