To handle both TTY and non-TTY calls, you will have two sets of greetings:
A Primary Greeting. Your primary greeting is both a spoken greeting followed by a TTY greeting. The first few seconds of the primary greeting will be a brief voice message, indicating that the caller has reached a TTY mailbox. After that, you will add a TTY message to the same greeting, immediately after the voice recording.
A Secondary Greeting. Your secondary greeting is a spoken greeting only, for callers who are not using a TTY system.
(Contact your administrator and ask to have "multilingual greetings with TTY as the primary call answer language" set up on your system.)