When you enable TTY mode, other phone functions may not work correctly. Depending on the phone you have, you may not be able to use SMS or regular voice calls when it's enabled. So, if you don't use a teletypewriter, it makes sense to keep the setting switched off to have access to your phone's full functionality.

What does TTY mean on your phone?

Teletype (TTY) machines are used by people who are deaf or hard of hearing to communicate by typing and reading text. If you have the iPhone TTY Adapter, available at you can use iPhone with a TTY machine.

What does TTY mode do?

When TTY (teletypewriter) settings are enabled, you can use your phone with a TTY device if you're deaf or hard of hearing. ... TTY HCO. Enables HCO (Hearing Carry Over) TTY VCO.