We asked someone who is familiar with amateur stuff about this today:
a lot of amateur DMR repeaters that are specifically Motorola branded (MOTOTRBO) are set up as IPSC (IP Site Connect) systems (1 master repeater, up to 15 slave repeaters nearby with low latency network connections to the master).
IPSC systems are used exactly the same as they are in non-amateur LMR use: all repeaters have the same output, and you can configure radios to vote scan, also known as roam.
Whatever gets inputed on one repeater is transmitted on all: that includes any call, private or group, and any group (there is also RAS, but this is a separate discussion).
Some of those group calls can be networked - and to make that happen, masters are interconnected through bridges, which have a whitelist of groups and configuration to pass through to all the masters.
What is very interesting is the way amateur repeaters are configured with many groups. Since these are not trunking systems, there is no concept of system dimensioning. So to prioritize group calls, bridges have use timer based priority.
It looks like the rule amateur bridges follow is that priority is given to group calls that affect less repeaters. So lets say you have a system that allows 1 (World Wide) and 3 (North America) on time slot 1 of all the repeaters.
- radio A is using 1 on your local repeater system.
- radio B comes up and starts using 3 on the same system.
- when 3 is no longer used, the 3 timer expires and 1 can be used again.
Because North America is less repeaters than World Wide, radio B's use of 3 trumps radio A's use of 1.
Go to nedecn.org, and on the left menu, click Talk Groups and Talk Group Pyramid. The lower the group call is in that time slot, the less it inconveniences the entire system, and thus the more priority it has.
