Samsung Galaxy Note 9 User Manual page 114

Apps
TTY mode
A teletypewriter (TTY) is a telecommunications device that allows people who are
deaf, hard of hearing, or who have speech or language disabilities to communicate by
telephone.
1. From
Phone, tap
2. Tap Other call settings > TTY mode.
3. Tap TTY Off, TTY Full, TTY HCO, or TTY VCO.
More options > Settings.
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