A fax machine is basically an image scanner, a modem, and a computer printer combined into one device that converts optical images into electrical signals to transmit over communication systems (phone line, internet, etc.). When the fax machine receives the electrical signal, it converts the signal back to an optical format to display or print the original image. This process is called facsimile transmission or faxing.
In the fax relay technique (not supported by CenturyLink) a faxed call over VoIP uses the VoIP device, generally called an analog termination adapter (ATA), to spoof a fax machine on each end of the relay.
Here are some things you should check to make sure your fax machine will work with VoIP.
|Fax machine type||VoIP compatible?||Configuration|
|Group 1 (G1) and group 2 (G2) fax machines||G1—no; G2—can interoperate with G3 machines.||No recommendation—G1 and G2 fax machines are obsolete.|
|Group 3 (G3)||Yes, however, if your G3 fax machine includes super G3, you’ll need to turn it off. If super G3 is on, you transmit faster, and that’s a problem for VoIP.||
Note: You may need to refer to the fax machine manual or check with the manufacturer to find out how to turn off super G3.
|Super group 3 (super G3)||No, in most cases. Super G3 fax machines don’t work well with VoIP, but you can turn off super G3 and try faxing.||
Note: CenturyLink cannot help you turn off super G3 on your fax machine.
|Group 4 (G4)||No, Group 4 fax machines are specifically designed to transmit on 64Kbps ISDN circuits and do not work with VoIP service.||Not applicable.|