Why won't my product answer to a distinctive ring?

• The DRPD (Distinctive Ring Pattern Detection) setting is off by default.
  
  Follow these steps to enable DRPD:
  1. Press the Setup button.
  2. Press the or button to select Fax Settings, then press the button.
  3. Press the or button to select Reception Settings, then press the button.
  4. Press the or button to select DRPD, then press the button.
  5. Press the or button to select ALL, then press the button.
  6. Press Setup to exit the menu.