114In the above example, if a hearing aid meets the M2 level rating andthe wireless phone meets the M3 level rating, the sum of the twovalues equal M5. This is synonymous for T ratings. This shouldprovide the hearing aid user with "normal usage" while using theirhearing aid with the particular wireless phone. "Normal usage" in thiscontext is defined as a signal quality that is acceptable for normaloperation.The M mark is intended to be synonymous with the U mark. The Tmark is intended to be synonymous with the UT mark. The M and Tmarks are recommended by the Alliance for TelecommunicationsIndustries Solutions (ATIS). The U and UT marks are referenced inSection 20.19 of the FCC Rules.The HAC rating and measurement procedure are described in theAmerican National Standards Institute (ANSI) C63.19 standard.Other Medical DevicesIf you use any other personal medical devices, consult themanufacturer of your device to determine if it is adequately shieldedfrom external RF energy. Your physician may be able to assist you inobtaining this information. Switch your phone off in health carefacilities when any regulations posted in these areas instruct you todo so. Hospitals or health care facilities may be using equipment thatcould be sensitive to external RF energy.
