Digital Mobile Radio
What its all about.
DMR is a commercial standard digital radio format providing voice communication as well as networked connections. The amateur variants of this are Fusion/Dstar etc.
As well as channels for receive and transmit for each repeater there are "Talk Groups" which you can think of as "radio nets" however these are all on the same repeater and are cross connected to other repeaters via the internet.
So for example Talk group 475 (abbreviated from full number) is used for general chat. If you call "475" on GB7SS your audio will also be transmitted via other repeaters with that talk group. So we have effectively a talk group which covers a very large area, like a super repeater.
The upshot of this is that there is Always someone ON and getting a QSO or chat is pretty easy using a handheld in most cases to your local DMR Repeater.
For more info on DMR the links below will help: