One of the features that we’ve worked hard to bring to you in 15.5 is G.711 FAX over SIP with T.38 fallback. This long-awaited feature can now allow your PBX to receive FAX transmissions over G.711 as well as the already supported T.38.

As FAX transmissions over T.38 protocol are not supported with all VoIP providers, allowing for FAX over G.711 allows non-T.38 supported providers to transmit FAX using the G.711 audio codec. 3CX accomplishes this with a built-in feature to detect and generate FAX tones within the first 10 seconds of the call. In this initial period, if a FAX tone is detected, 3CX switches over to G.711, otherwise it falls back to T.38.

To enable the G711 fax functionality in 3CX from within the management console go to Settings > Fax Server > Enable G711 to T38 Fallback > OK, as shown in the screenshot below.

Where to get 15.5

You can download the Linux version or the Windows version. Alternatively take it for a spin using our PBX express tool! We’ll configure a brand new PBX for you to try.

Windows: https://downloads.3cx.com/downloads/3CXPhoneSystem15.65073-beta.exe

Linux: Follow this guide – but in “/etc/apt/sources.list.d/3cxpbx.list” update the repository to the BETA Repository “http://downloads.3cx.com/downloads/3cxpbxbeta/ /”. Save and perform “apt-get update” and “apt-get install 3cxpbx” commands. The complete list of commands should look like this:

wget -O- http://downloads.3cx.com/downloads/3cxpbx/public.key | apt-key add –
echo “deb http://downloads.3cx.com/downloads/3cxpbxbeta/ /” | tee /etc/apt/sources.list.d/3cxpbx.list
apt-get update
apt-get install 3cxpbx