Mixin functionality is only available in Pro subscriptions.
Mixins are useful for larger company setups with multiple dashboards. Let's say you have a big company, with the head quarters managing the main dashboard and a number of other offices managing their own dashboards from which they play their channels. With mixins, HQ can periodically interrupt playback of all channels of all offices and have those channels play HQ's mixin channel instead. This is particularly useful, for example, in a scenario where playback of advertisements or HQ messages is mandatory in the office channels.
Let's say you fill in 600 seconds, then playback of the other channels will be interrupted every 10 minutes. The mixin channel will play exactly once: so once it is played, it will not start from the beginning again.
Only one channel can be set as a mixin channel.
When a channel is set a as a mixin channel, an icon will be displayed beneath the playback address to indicate that that channel is set as a mixin channel.
On the other dashboards, a note is shown in the Channels panel to indicate that channel playback will be interrupted by a mixin channel every X minutes and for Y seconds.
In summary, mixins are a way to do a mandatory push of content from HQ to all other dashboard. Other dashboard users cannot opt out.
There are two more voluntary ways of sharing content with other dashboards: