great thaanks guys! that helped a lot... it seems like trunked system is a better way to go as far as a radio system is concerned but it seems way more complicated.
I wouldn't make that assumption; it depends entirely on the nature of the operator's function, the number of units he has in the field, and how they are configured in terms of what they do.
The basic difference is easier to understand if you accept that "channel" can have two different meanings.
Logically, a channel is a group of users who have to talk to one another and (in most cases) whom you want to be able to hear what everyone else is saying.
Physically, a channel is a radio path by which the members of the logical group communicate physically.
Before trunked radio came along, the two concepts were linked: for each logical channel you wanted or needed to perform your function, you needed that number of physical channels.
Trunking was designed to solve two problems. First, there simply weren't enough frequencies to give everyone as many physical channels as they wanted. For instance, before trunking, the Massachusetts State Police had a total of 7 physical/logical channels for the whole state. Today, they have over 100 logical channels but only 28 distinct physical channel pairs. Second, the fact of the matter is that, even in public safety, a dedicated physical channel spends most of its time idle. If you pull statistics from a voter, you'll find that your typical Fire Department's main dispatch channel is actually transmitting less than 1% of the time during a 24-hour period, and a typical Police Department's main dispatch channel seldom transmits more than 2-3% of the time. The rest of the time, the channel is idle and not in use, but you can't use its idle time for anything else, because when you need it for your Fire or Police function, you need it right now.
What trunking does is to separate logical channels from physical channels. In its simplest form, an agency might have five repeaters set up. One is dedicated to data; the other four are available for voice. When a member of a logical channel group keys up, the system picks one of the idle voice channels and assigns it for the use of that logical group. A data command causes each radio selected on the logical group to switch to the voice channel for the required communication; when the communication is completed, the radios switch back to the data channel and wait for another command.
Now things get complicated when you decide to set up voted satellite receivers or if you decide to set up a simulcast system, but the basic principles are as set forth above.