So that a user can listen to another, they must go to “My Profile” > “Dual listening” tab. He will be able to view the users he can listen to and the users who can listen to him.
A padlock next to the user's name indicates that you are not responsible for this user and therefore cannot modify dual listening access. This is why the radio buttons will not be clickable.
To start dual listening, the user just needs to click on the “phone” icon. The call then opens automatically in the webphone