The Mode tab allows you to select the Fax-only or Voicemail mode for your phone line. When the Fax-only mode is selected (e.g. for a phone line that represents a DID number), every incoming call to this number will be answered with “start fax” tones, indicating that it will only receive fax messages. Thus the phone line will serve as a dedicated fax line, emulating the behavior of a legacy fax machine. When the Voicemail mode is selected for the phone line, this allows a caller to leave a voice message which can be listened to later.