While Megaphone allows you to speak to the whole room, there is a function of broadcasting to all rooms at once. This button is only available to admins and hosts and is located at the bottom of the screen.
This feature will be useful when you need to make a short announcement for all participants in all rooms since you cannot get feedback on this channel.
By clicking on this button, you will need to confirm the start of broadcasting. Please note that you will not be able to hear other room members.
When you start broadcasting, your image will be shown in every room and every participant in the upper left corner of the screen.
You can also turn off the camera and only use the microphone for broadcasting.
Then, instead of your image, such a sound wave will be shown.