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VoIP Fax off hook problem

Troubleshooting Phone Off Hook fax message

Some faxing issues can be caused by other issues that are not directly related to transmitting the fax over VoIP.  We include troubleshooting these issues, like an Off Hook message, as they can be experienced by VoIP users and in some cases, like integration issues between VoIP and alarm lines,  can be caused by a consequence of using VoIP.


If you fax over a VoIP line and see a message Phone Off Hook this could be the result where the VoIP line is not open.  Typically this issue results from having a telephone receiver off hook (the handset is lifted) somewhere in the premise and the telephone line is open.  With VoIP setups there can be additional issues, especially with alarms that have seized the line, but due to signaling failures are unable to release the line.

Look at the following possibilities for an Off Hook message:

  • 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.



Always make sure that your VoIP line is connected to Line in and any telephone is connected to the phone line (Marked usually with a phone emblem).



Step by step, solve off hook issue

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.