This AGENDA internal command is used to preload an external stream a few minutes before the scheduled broadcast, and the broadcast will start only when the station generating the stream sends a special metadata or a DTMF code. In fact, it is possible to configure an external flow so that it goes on air when a code xx arrives and goes off air when another code xx arrives
If the broadcaster does not use MB STUDIO, it will have to tell you the metadata text or the DTMF code to use. In the "Returns to air..." box enter the code that starts the connection and in the "Off air ..." box enter the code that put the connection off air
If the broadcasting station generates the stream with MB STUDIO you do not have to write anything in these boxes, the connection will go on air automatically when the broadcasting station broadcasts an object in whose properties the "End split" flag is turned on
And the connection will go off air automatically when the broadcasting station broadcasts an object in whose properties the "Start split" flag is turned on
In the agenda you need to specify the optional parameter index:
index=xx where xx is the index number of the external stream you want to broadcast. 
you can also add the following optional values separated by semicolons ;
timeout=xx where xx is the number of seconds after which the external stream will be played even if the expected metadata or code has not been received. Example: if the agenda command is scheduled at 11:57 and I set a timeout of 240 seconds (4 minutes) the external stream will be anyway on air no later than 12:01
agc=x automatic volume control 0=default 1=disabled 2=soft 3=standard 4=high
Example:
index=33 broadcasts the external stream with index 33
index=87;timeout=600 broadcasts the external stream with index 87 and if the expected metadata or code does not arrive, forces the broadcast after 10 minutes
index=45;timeout=300;agc=0 broadcasts the external stream with index 45 and if the expected metadata or code does not arrive, it forces the broadcast after 5 minutes and uses the default configuration of the automatic volume control
This system therefore allows you to broadcast a single program among many connected radio stations and possibly make commercial breaks with your own local advertising.
Keep in mind that when the external stream goes off the air, MB STUDIO actually remains connected to the external stream in the background and continues to listen to any metadata or DTMF codes and indicates this on the screen:
If you don't plan to reconnect to the flow you should disable it or via a "Terminate Connection" event
or via Agenda
