DMR & Fusion - My notes.
Unlike Fusion the talkgroups on Brandmeister DMR are selected on the radio being used and not changed on the repeater or hotspot being used.
You listen to DMR talksgroups like changing channels on the TV. Everyone watching (listening) to that channel can hear it.
If you're on a channel you don't hear the other channels.
Another TV (repeater) may not have all the channels available.
Not all channels on repeaters are available on hotspots.
Anyone listening to the talkgroup may or may not hear the conversation because of static and dynamic group modes.
Static groups can be setup on your hotspot so they 'listen' on a list of selected talkgroups (channels)
Dynamic talk groups are the talkgroups to select and 'key-into' (curchunking or announcing your callsign) They stay 'active' for 15 minutes after your last PTT in that group. After that you won't hear anything.
Fusion is a different beast. You connect to a server that is on its 'home' talk-room and you can talk to it and all the repeaters using the same home 'room' (channel).
There are many rooms - just like many talk groups.
With Fusion you connect via C4FM and then enter WIRESX mode that allows you to change the room currently active on the repeater.
What this means is that when you change the room - anyone connecting to that repeater now uses the new room you changed to and the 'home' room in not active.
So I call this a one to many relationship because my 'one' room selection effects what 'many' can hear or transmit to.
Imagine talking on 146.640 on the repeater and someone changes the repeater to 145.145 so they can check in on the Net being run on that frequency.
Some fusion repeaters will automatically reset to their designated 'home' room after some period of inactivity. Other repeaters stay on the new room until someone switches it back. So its easy to see how not putting the room back to 'home' causes concern. This is why a hot-spot is all but necessary to use Fusion without making people angry.