Future Nine Corporation FAQ

ID #1004

The short answer is yes, you can.

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The long answer is that Voice over IP as a whole does not support fax well at this point. The settings below will work MOST of the time, but not all the time. Please understand that while we encourage you to try and use fax with our service, we cannot guarantee it will work. If fax is very important to you we recommend keeping a basic PSTN phone line for this purpose.

To maximize fax success with our service:

1. Set your codec to g711u (ulaw). Fax will NOT work with any of the lower bandwidth codecs.

2. Set your RTP Packet Size to 0.020, or even 0.010.

3. Make sure you have plenty of free bandwidth available to avoid interruptions.

4. Disable ECM on your fax.

5. Decrease the transfer speed on your fax to 9600 bps or lower. Different faxes have different ways to do this, some of them call it "Overseas mode".

6. Put a DSL filter between your fax and your Analog Telephone Adapter.

7. Try to avoid faxing long documents. Try to fax pages in bunches of 2-3 at most to maximize chances of success.

8. You will want to disable echo cancelation. Some adapters like most Sipura models (PAP2, SPA series, etc.) have a "FAX Disable ECAN" mode which will automatically disable this when it detects a fax being sent. If your adapter does not support this, we recommend you keep echo cancelation on when making voice calls, but turn it off manually when faxing. Another option would be to set Line 1 with settings ideal to voice, and Line 2 with settings ideal for fax.

9. Disable Silence Suppression while faxing.

10. Set FAX Codec Symmetric to No.

11. Set FAX Passthru Method to ReINVITE.

12. Set FXS Port Input Gain and FXS Port Output Gain to -3.

13. Set your Jitter Buffer to Extremely High, and Jitter Buffer Adjust to NO. Faxes don't care if there is a delay on the line, all they care about is getting a consistent data stream. Jitter buffer does just that. :)

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Following the above settings you will maximize your chances of faxing over IP, but unfortunately this is not a guarantee that it will succeed. We wish you the best of luck though, happy faxing!

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One more note: we have discovered that some of our vendors support voice better, while some of them support fax better. If you are trying to fax to a number which is a dedicated fax, you have completed all the steps above, and after repeated tries it is still not working - please email us with the number you are trying to send to, and we will override that number to go through a provider who supports fax better.

 

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