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
20.19of 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/DigWireless.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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