I have managed to accomplish this through the GUI - if anyone is interested here are the notes i've written for my team to add a secondary extension to our Yealink phones in order for us to create a ring group so that we can call a group of phones based on their physical location and not by the user logged into them:
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Everything in bold should be your own input, in this example I am setting up a ring group for an IT support technicians phone, hence the names :
On 3cx admin go to the extension page and add a new extension number
https://
SERVERNAME.3cx.co.uk:5001/#/app/extensions
General Tab
Extension
0003 (this is going to be the secondary extension number)
First Name
IT Support
Last Name
Desk 3
Options Tab
Check the Hide this extension from 3CX company phonebook and 3CX Apps
On the phone provisioning tab under authentication, make note of:
ID
Password
Click OK to save, important to do this first before continuing!
On 3cx admin go to the phones page and search for the physical phone you want to add a secondary extension to. (https://
SERVERNAME.3cx.co.uk:5001/#/app/phones)
Make note of the IP, start a new webpage tab and browse to the IP address. The username will be
admin and if you click on the phone extension itself (under https://
SERVERNAME.3cx.co.uk:5001/#/app/phones) the password will be found under phone provisioning->options-> Phone Web Page Password
Login to the phones direct IP webpage and go to the account tab
Select Account 2 under register
Line active set to enabled
Set the label (in this instance it’s going to be
Group | IT Support)
Display Name
IT Support
Register Name ((https://
SERVERNAME.3cx.co.uk:5001/#/app/phones) ID under the new extension->phone provisioning->authentication)
Username
The secondary extension number you created in the first step
Password ((https://
SERVERNAME.3cx.co.uk:5001/#/app/phones) Password under the new extension->phone provisioning->authentication)
Server Host
SERVENAME.3cx.co.uk
Server Expires
120
Click confirm
Finally, still on the direct IP phones webpage go to the Settings page->configuration-> and export CFG Configuration File
Save this file to a (secure) folder, it will save as the mac address name. It may be required for an easy restore if the firmware of phone is ever updated.
You can now add this new secondary extension to a ring group
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Hope this helps someone, somewhere, someday