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Troubleshooting Faxing over VoIP

Communication Errors

There are some other things that you will want to check, especially if you are still experiencing communication errors. Some fax machines, especially Brother, have an Overseas Mode, which can be enabled before a VoIP Mechanic will help make your fax machine usable over VoIP.fax. This setting makes temporary changes to the fax tones to accommodate noise and static and should be set before each outgoing fax. Check for the following:

  • Use a direct connection from the IAD to the fax machine. Try removing any splitters and other devices in that line. Some devices may interfere with the fax transmission, such as, answering machines and caller IDs. Try enabling Overseas Mode.
  • Change the resolution setting to Standard, rather than super fine. This limits the amount of packets that need to be transmitted.
  • If your fax machine is not connecting to the receiving fax machine try disabling or clearing any stutter tones that may be present on the line. Many VoIP providers use a stutter tone to notify the user of new voicemail. These stutter sounds will confuse the fax machine.
  • Try to set the CHG Tone MIN Count setting.
  • Try plugging in the power adapter cord directly into a wall socket, rather than a power strip or surge protector.
  • Try placing a DSL filter in reverse position between the ATA and the fax machine.

Phone Off the Hook Fax Messages 

Check the following potential reasons for an off the hook message. (Always assure your VoIP line is connected to “Line in” and any telephone is connected to the phone line.

  • A phone connected to the fax machine (or the same phone line) is using the line or the handset is not cradled properly.
  • A credit card machine or modem is accessing the line.
  • An alarm device or other electronic device is using the phone line.
  • Telephone Answering Machine using the phone line. 

To locate the source of the issue it is best to disconnect any phones or other devices that are using the same VoIP phone line one at a time.  Check the fax machine’s display after disconnecting each phone or device and if the message clears after disconnecting a particular phone or device from the line, that is where the problem rests.  Check your alarm device as well and make sure that is is not using or still connected to the line.  You can eliminate all premise equipment by connecting the fax machine directly to the VoIP ATA to see if the message clears.

Troubleshooting a Cisco/Linksys ATA

There are some configuration settings which can be made inside the Cisco/Linksys ATA which will help faxing.  The first step in configuring these settings would be to access the Linksys PAP2t or other Linksys ATA device itself and have access to the Advanced Settings.  Some VoIP providers may “lock” the device, in which case you may not have the ability to make these advanced fax adjustments.

Typically, faxing can be disrupted or act negatively to silence suppression and  to echo cancelling techniques, so these variables would want to be disabled in many cases, as well to packet loss, which can quickly cause a fax to fail. 

  • Access your ATA device and click “Switch to Advance View”
  • Next, choose the Line that is being used for faxing.
  • Look for “Network Settings” and set “Network Jitter Level” to “Very High”.
  • Next, go to the “Audio Configuration” section.
  • Set Silence Supp to No (default setting).
  • Set Echo Supp Enable to No.*
  • Set Echo Canceller to No.*
  • Set FAX Passthru Method to NSE.
  • Set FAX Passthru Codec to G711u.
  • Set Use Pref Codec Only to Yes.
  • FAX Disable ECAN to Yes.*

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