Creating an “extension” in FreePBX sets up the account details that we will use in our actual extension to connect to the system. Our extension could be a physical VOIP extension (like the Yealink T22P), a softphone for your computer (like Linphone) or an app for your mobile phone (like Zoiper). Whichever it is we create the extension in FreePBX the same way.

1 – Log in to FreePBX and select Applications / Extensions from the menu bar at the top

2 – Ensure “Generic CHAN SIP Device” is selected and click submit

3 – Enter extension details

These are the details you will use in you physical VOIP extension or softphone. You will only need to enter a few of the available options. The rest can be ignored for now.

The extension number is the number extensions will use to call each other and the display name is what will appear when you call another extension.

Scroll down the page and make a note of the “Secret”. This is the password you will use when connecting the extension. Ensure the password is long and complex. You should also change NAT to Yes.

Now scroll down to the bottom of the page and click submit

Finally click Apply Config. Until you do no changes will take effect and your extension will not work

4 – Set up your actual extension

I’m going to use Linphone here, but this could be a physical VOIP handset also. We will need 3 bits of info to set up any extension – the server name or IP, the extension number and the extension password (secret).

In Linphone we go to Preferences and Manage SIP Accounts, where we add a Proxy

Now we enter the SIP details we created in FreePBX. On a SysAdminMan system, instead of entering “doc.sysadminman.net” you would use your server IP address

When you click “OK” Linphone will ask you for the extension password (secret)

If that worked OK you will see Linphone is registered successfully with FreePBX

5 – Make a test call

You should now be able to make a test call from your extension. If you call “*43” you should hear an echo test

6 – Create any other required extensions

You should be able to create any other extensions you need. Once you do these extensions can call each other for free