When you wish to ring more than 1 device / number at the same time, you will need a Call Group. Call Group allow you to create a list of devices or numbers within a same group and ring them simultaneously. You may manage all your call groups within your Offisky phone system here in this screen.
User Menu >Under Settings, select (Phone System). In the top navigation menu bar, select PBX Base > Call Group List
To reload the current screen, click on the  icon.
To update a call group, click on the  icon.
To create a new call group from an existing one, use the  icon.
To create a new (blank) call group, use the  icon.
To remove a complete call group, use the  icon.
To sort the result list, use the provide feature at the bottom of the screen.
The page switch is located at the bottom of the result list.