Fax Machine Settings for VoIP Faxing
Learn about common configurations for a fax machine to send and receive faxes over VoIP.
Written by Adrian Angwenyi
Updated at November 27th, 2023
Table of Contents
Analog Vs VoIP Faxing
Analog Faxing
Faxes have historically been sent over copper wires using sounds (analog faxing). The sounds are converted back into data by the fax machine receiving the fax. If there is data loss during the transmission of an analog fax, the receiving fax machine has to terminate the transmission. This results in delays since the fax would need to be sent again.
✔ Using analog faxing is recommended for organizations that depend on sending long, multi-page faxes that should be kept secure.
For casual fax users, VoIP faxing can be a cost-effective, more convenient fax solution.
Faxing Over VoIP
VoIP faxing allows you to conveniently send faxes from your computer without the hassle of printing out a document and feeding it into a fax machine to be sent. Unlike with analog faxing, a physical, dedicated phone line is not required to send a fax over VoIP as a fax's data is transmitted wirelessly over the internet.
✔ VoIP faxing also opens up the possibility of sending faxes using your email and other web applications.
To have your fax machine send faxes using VoIP, you will need…
- A fax machine that has had its settings configured for VoIP services.
- An Analog Telephone Adapter (ATA) for faxing connected and registered to your fax machine.
- An extra phone number that has been routed and configured for faxing with your fax ATA.
To make the switch over the VoIP for faxing, contact our technical support department to explore your options.
Fax Machine Settings to Adjust for VoIP Faxing
G711 or a Non-Compressed Codec
Make sure that your VoIP fax connection (the line you use for faxing) is set to G711, which is a non-compressed codec. G729 uses compression which will make faxes fail. If your VoIP provider has what may be called a "Bandwidth Saver" setting, then this setting would be a compressed codec. Make sure this setting is not enabled. You may have to talk with tech support for your VoIP service who will verify what type of codec your connection uses and to make sure your connection is set for G711.
Baud Rate
Slow the transmission speeds on the fax machine settings. Both the Tx and Rx settings. This is called the BAUD rate of the fax machine. The best and fastest setting should be 9600 bps.
Enable Auto-Answer
To make faxing over VoIP more automated, auto-answer needs to be turned on in the fax machine's settings. If auto-answer is disabled, then each fax would need to be manually answered on the fax machine.
Disable ECM (Error Correction Mode)
ECM is usually on by default on most fax machines. This setting needs to turned off.
Why Should ECM be Disabled?
Fax machines (also multi-function machines) set ECM as a default to on. This setting causes the receiving fax machine to analyze the received data frames and detect any data that may be corrupted. Any noise, lost packets, or poor signal strength can cause part of the transmission to be lost which then triggers a retransmit signal to be sent until an error-free frame is received. This causes retransmits more often over VoIP due to some packet loss, latency or jitter which exists on an Internet connection. These retransmits increase the call duration, quickly adding to the instability of the fax, requiring additional retransmits which then cause a failure with a communication error reported by the receiving fax machine.
Disabling ECM, will result in the receiving fax machine to accept a transmission with some frames that may have bits of information missing, but still resulting in a completed fax, which should be of acceptable quality.