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 American National Standards Institute (ANSI) C63.19 standard.
For information about hearing aids and digital wireless phones
FCC Hearing Aid Compatibility and Volume Control
http://www.fcc.gov/cgb/dro/hearing.html
Gallaudet University, RERC
http://tap.Gallaudet.edu/DigWireless.KS/DigWirele
ss.htm
Hearing Loss Association of America [HLAA]
http://www.hearingloss.org/learn/cellphonetech.asp
The Hearing Aid Compatibility FCC Order
Safety
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