HP All-In-One and Fax machines are in many home offices and small businesses, including those using VoIP for their sole communications connections. Numerous older HP fax machines offered ways to make the necessary configuration changes to successfully fax over VoIP. These changes are to set the BAUD rate to 9600bps and disable ECM (Error Correction Mode). We have listed the instructions for those who have HP fax machines (or All-in-One machines) and are now choosing VoIP.
These two settings should allow faxes to successfully transmit over VoIP.
Or you may find the following settings appropriate for many later model OfficeJet All-in-One machines.
Note: HP fax machines that offer three speeds are the usually listed as Fast, Medium and Slow. The medium and slow speeds are in order 14,400bps and 9600bps. We suggest always opting for 9600bps for VoIP, as the medium speed of 14,400 in ideal circumstances could allow faxes to successfully transmit, but on days when less than ideal circumstances occur (higher latency, slight packet loss, etc.) they will fail at 14,400bps. Some VoIP connections may always fail at 14,400bps, but transmit with 9600bps.
On HP machines ECM (Error Correction Mode) is defaulted as on. Turning off or disabling ECM will allow faxes over VoIP to continue without a retransmit if small bits of information is missing, which is very typical of data sent over the Internet. You will want to make sure that ECM is disabled.