Function introduction:
The full name of HAC is "Hearing Aid Compatibility", which is a standard for mobile phones to support hearing aid compatibility. Mainly refers to the communication equipment supplier to provide a mobile phone whose radiation has very little interference to the frequency, and can be compatible with hearing aid inductors or microphones.
HAC involves two compatibility coefficients "M" and "T", ("M" is the compatibility for microphone reception; "T" is the compatibility for induction coil reception). The interference of the mobile phone to the hearing aid microphone meets the M4 level, that is, the least interference; the inductance compatibility coefficient reaches the T4 level, that is, the built-in inductance circuit of the hearing aid has the best compatibility with the mobile phone. In addition, in terms of hardware, a coupling coil needs to be added to the traditional receiver (mobile phone wireless reception) .
Supplement:
At present, Xiaomi's phones (including models sold in mainland China, Hong Kong and Taiwan, and overseas) do not support this standard.