TTY stands for "teletypewriter," a device initially created to allow individuals with hearing or speech impairments to communicate by sending typed text over standard telephone lines. In modern smartphones, TTY mode replicates this functionality, enabling text-based communication during a voice call. A TTY device must be connected to the computer to interpret the modified audio otherwise you might experience poor audio quality. Using TTY mode in a conference call may also cause audio quality issues. TTY mode is turned off by default. ^{androidauthority.com}+1 ^{1 2}