1. Dial *983*889*1# to enter TTY full mode (transmit and receive TTY characters).
    device 612/252975.jpg
  2. Dial *983*889*2#  to enter VCO mode (receive TTY characters but transmit by speaking into the microphone).
    device 612/252976.jpg
  3. Dial *983*889*3# to enter HCO mode (transmit TTY characters but receive by listening to the receiver).
    device 612/252977.jpg
  4. Dial *983*889*0# to reset the phone to standard voice speaking and listening mode.
    device 612/252974.jpg