Quick question...why can scanners monitor systems withotu affiliating, but radios cannot? Security feature due to the transmit ability?
Mostly affilating lets the system know the radio is there to receive traffic. In a system with multiple "zones", this can be used to only send traffic to those sites that have a radio "attached" that will use the traffic - instead of wasting channels with traffic nobody will hear. For example:
A north zone and south zone with north and a south dispatch TGs. In a split system, normally each zone would only have the appropriate TG. But if a north car drives south and needs to follow their north TG traffic, affilating tells the system to send the north TG to the south zone sites.
A scanner can not affilate, so in a system such as the example above, a user who scans a south zone site would normally never hear the north TG. That TG could come "alive" one day when a north car drives south. This is a common configuration on large (i.e. statewide) systems. Usually there is some type of timer that will time out the affilation if the system has not heard from the radio in X minutes/hours.
With some brands of radios it is quite possible to follow a trunked system without affiliation. Of course, you will only hear the traffic that is present on those sites...you have no ability to force traffic.
Not all systems are setup this way...some systems just send all traffic to all sites...i.e. if the system is small. Then affiliating is far less important.
Disclaimer: The above is a general description and it varies from vendor to vendor and configuration to configuration.
