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@RaleighGuy said, the best way to know what you want to hear is to listen for awhile until you know which channels they use for what you want to hear about. But, I think the channels you want are the ones labeled Law Dispatch, Law Tac, and Law Talk, Fire Dispatch, Fire-Tac, and Fire-Talk, and EMS Dispatch, EMS-Tac, and EMS-Talk. Do you also want to hear the channels used for incidents when multiple agencies have to talk to each other, such as a pursuit or major fire? If so, those are labeled Interop and Emergency Ops.