在查找HAC相关资料的时候找到的关于HAC定义的M/T认证的基础知识。
引用地址：http://www.airfiremobile.com/HAC
Hearing Aid Compatibility
To make sure the deaf and hard of hearing individuals can use digital wireless devices, the Federal Communications Commission (FCC) updated the Hearing Aid Compatibility Act of 1988 ("HAC Act"), passing regulations to increase the number of hearing aid-compatible wireless devices. The FCC has approved standards and passed regulations for digital wireless devise use with hearing aids. The FCC defines Hearing Aid Compatibility (HAC) for wireless devices in terms of two parameters; radio frequency (RF) emissions and telecoil coupling.
Digital technology means more features and improved efficiency—but some digital phones can cause interference for hearing aidusers. When a wireless phone is in communication with its network an electromagnetic field is present around the phone's antenna. During communication with a digital wireless phone this field pulses. It is this pulsing energy that may be picked up by the hearing aid's microphone or telecoil circuitry and is heard as a buzzing sound through the hearing aid.
How will I know if a phone is rated for HAC?
Information about a wireless phone's HAC rating can be found on the feature cards next to the phones on the phone box and in the phone manual.
How will a HAC phone be labeled?
Only phones that meet the minimum rating will be labeled HAC compliant. The package and the display cards will be labeled in with a "M" and/or a "T" and a rating number. If you see a M3, M4 T4 or T3 label on the feature cards or packing then the devices is HAC compliant.
What does the M3 or M4 rating mean?
"M" refers to the devices RF emission level and means the device is intended for use with hearing aids in microphone mode. The higher the M rating the more likely you will be able to use the phone with your hearing aid on the microphone setting. Phones with an M-Rating of M3 or M4 meet FCC requirements and are less likely to generate interference to hearing devices than phones that are not labeled.
What does a T3 or T4 rating mean?
"T" refers to the device's telecoil coupling ability and means the device is intended for use with hearing aids in telecoil mode. The higher the "T" rating number on the phone the more likely you will be able to use the phone with your hearing aid on telecoil setting.
What is a Telecoil?
A telecoil is a small device that is built into some hearing aids for use with the telephone as well as assistive listening devices. Telecoils are very useful for telephone communication because they allow the volume control of a hearing aids to be turned up without creating feedback or whistling. Background noise can be reduced especially when using cell phones in noisy places.
Telecoil users will also want to control backlighting of the display and keypad since these features may also cause interference. Interference from backlighting is not considered when determining a cell phones HAC rating.
Phones and accessories that are Hearing Aid Compatible (HAC) will work with hearing aids that support the telephone switch feature. This is commonly known as the "T-switch" or "T-coil" that is built into the hearing aids. HAC products will only work with hearing aids that have a telephone switch.
