Faxing via VoIP Compatibility Issues

Please note that we can not guarantee that it is going to work with all fax
machines.
Here is the procedure:

For free IP to IP faxing, both the sender and receiver need to be Globalink
members and have their fax machines attached to IP analog telephone adapters
(ATAs).

In order to send a fax to a PSTN (traditional) fax machine, you will need to
have at least a Premium 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 minimum of 64Kb/s in both
directions to be reliable, but we recommend more than 90Kb/s.

Globalink Tech Support