LG D415 - Manual (Page 120)

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The M and T marks are recommended by the Alliance for Telecommunications
Industries Solutions (ATIS). The U and UT marks are referenced in Section
20.19 of the FCC Rules.
The HAC rating and measurement procedure are described in the American
National Standards Institute (ANSI) C63.19 standard.
To enter that the Hearing Aid Compatibility rating for your phone is maintained,
secondary transmitters such as Bluetooth and WLAN components must be
disabled during a call.
For information about hearing aids and digital wireless phones Wireless
Phones and Hearing Aid Accessibility
http://www.accesswireless.org/
FCC Hearing Aid Compatibility and Volume Control
http://www.fcc.gov/cgb/consumerfacts/hac_wireless.html
For Your Safety