If you want to keep up with what is happening right now in your town or city, a trunking scanner is the best tool to have. These devices are used by radio enthusiasts and everyday people who want to be able to listen in to police and fire communications. Depending on where you live, a trunking scanner (as opposed to a standard police scanner) may be required to hear emergency channels.
A trunking scanner works differently than conventional radio systems. In an ordinary system, channels are designated and assigned to different functions and departments. With trunking scanners, any department can use any available frequency and they are identified by what is known as 'talkgroup ID's'.
A communication picked up by the scanner can be matched to the right department if you know the talkgroup ID's of each. Of course, listening to local communications for long enough will give you plenty of time to determine who uses which ID's in your area. Another way to get this type of information is to check online lists of Trunking ID's.
Filtering out what you want to hear is as easy as programming your Talkgroups in to ID banks. You can then have the scanner only relay information on those specific channels. For organizational purposes, you can even create sub groups within groups. You should try to separate the departments in to banks and the specific groups beneath them. If you did this, you would have things like Police, Fire, Animal Control, and so on. Within them you could have separate channels for state and city police, dispatch and other specifics.
If you are shopping for a trunking scanner, you should be prepared to pay 0 or more. Uniden is the most popular manufacturer of these devices with their TrunkTracker line and Radio Shack also makes their own line of devices. You will have the option of purchasing a hand-held model or a desktop model, both do the same thing but one is portable.