LG C800DG User Manual page 159

Hearing devices may also be rated. Your hearing
device manufacturer or hearing health professional
may help you find this rating. Higher ratings mean
that the hearing device is relatively immune to
interference noise. The hearing aid and wireless
phone rating values are then added together. A
sum of 5 is considered acceptable for normal use.
A sum of  is considered for best use.
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 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's
acceptable for normal operation.
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