In order to send a fax to a PSTN (traditional) fax machine, you will need to have at least a Premimum Membership account as well as an ATA device such as Cisco ATA 186 or Sipura connected to your fax machine.

One other important factor when faxing over VoIP is the quality and speed of your Internet connection. Since fax data cannot be compressed, the G711u/a CODEC must be used. This codec requires a minumum of 64Kb/s in both directions to be reliable, but we recommend more than 90Kb/s.