First you have to tell the scanner what type of trunking system
(Motorola I, Motorola II, EDACS.) you're listening to.
There are a few very good introductory explanations of trunking
systems on the web. (I worked in the two-way field for many years,
but I started scanning trunked systems knowing less than you do.)
The trunking system was programmed into everything

I know that the locals
are using MotorolaII...