Explaining the theory of a "trunked radio system" is far easier than implementing it on a scanner.
As you know this refers to a system where the Control, or Base, Station locks onto the mobiles and they skip freqs together on every transmission according to encoded info prefacing the voice transmission.
(Oh, I'm sure I'll be corrected and rightly so, no doubt. Just trying to keep it simple and general- he said in a pre-emptive defensive action.)
Before Austin TX went APCO 25 digital, I worked for an evening to get the Pro91 to trunk and only got Water Works and other ho-hum stuff. Blew it off and went back to Conventional where the action was.
Now I run Pro-96 for the most part. Programed with Win96, and it trunks the APCO here like a mother... (Also OK for EDACS on LCRA, Lower Colorado River Authority, coms.)
APCO 25 is also a trunked system but it's far more complex and digital. You didn't mention what your scanner is. If it's an RS then it MUST be Pro96 or base 2096 to do digital.
Say, that's a good question! What scanner have you, Sir?
I see you also don't mention your 10-20. What system do you want to trunk??
You may want to look at what systems are in use in your area before you worry much about trunking. What's your area-of-interest?
73's
Jon