FreelyCall supports T.38 and G711 Audio mode fax. You just need to add your SIP settings to your device/software, and purchase a recharge card from FreelyCall and you’re ready to send faxes

Fax from Web
Upload a PDF file, put the destination fax number you want to send the fax to in E.164 international format, then submit

Fax with Fax Machine

If you are using a fax machine which supports T.38 or a classical fax machine connected through a SPA3102 to FreelyCall, you should have no issue sending faxes.

To make sure your faxes succeed, you need to change some settings in your SPA3102 to optimize it for fax sending:

1- Line 1 tab

Network Jitter Level: very high.

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.

2- Sip tab

Rtp Packet Size: 0.020

Fax from your computer
You can install a software on your PC/Mac to send faxes using T.38 or g.711 audio mode fax.  Note that many destinations do not support T.38 mode yet, so it’s important to keep your software settings flexible to use both available mode. To get started,

1- Get a FoIP (Fax Over IP) software. Software reported to be working include:

2- Sign up with FreelyCall to get your SIP  user/password/domain

3- add the SIP details to your software.

4- start faxing!

Fax with Asterisk
If you are using a PBX such as asterisk, here’s a few steps to help you get started sending faxes from asterisk through your FreelyCall trunk.

1- get a ‘free fax for asterisk’ license for free from digium here: http://www.digium.com/en/products/software/fax-for-asterisk
2- you will receive 2 emails from the digium, the instructions in the 2nd point to this URL: http://downloads.digium.com/pub/telephony/fax/README just follow exactly what it tells you, and you should have fax sending working
3- the .tif file to use should be fax compatible. the best way to create one is to use ghostview, passing along a pdf which will output the tif.

     gswin64c.exe -q -sDEVICE=tiffg3 -r204x98 -dBATCH -dPDFFitPage -dNOPAUSE -sOutputFile=faxtest.tif faxtest.pdf

4- to test from asterisk CLI without creating a callfile, try:
     originate SIP/phone-number@freelycall application sendfax /root/faxtest.tif,fzd

Once above is working, you can choose from a wide range of applications to send/receive faxes from your desktop.