The ANSI standard for hearing aid compatibility contains two
types of ratings:
•
M-Ratings: Rating for less radio frequency interference to
enable acoustic coupling with hearing aids.
•
T-Ratings: Rating for inductive coupling with hearing aids in
telecoil mode.
Not all phones have been rated. A phone is considered hearing
aid compatible under FCC rules if it is rated M3 or M4 for acoustic
coupling and T3 or T4 for inductive coupling. These ratings are giv-
en on a scale from one to four, where four is the most compatible.
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