If you have up to 20-30 lines or more you can ask people to mute their phones when not talking.
If their phone does not have a mute button, they can mute/unmute their lines by pressing ∗ 6
I need more control
You can forcibly mute all lines by pressing ∗ 5
There will now be no background noise.
Your participants cannot unmute themselves.
If you would like the participants to be able to talk such as for a question and answer session, you should press ∗ 4
You should now tell your participants that if they have a question/want to talk they should press ∗ 6