You can find a list of local police scanner frequencies for many agencies at RadioReference.com, according to its website. RadioReference.com also provides a list of other radio frequencies, including businesses, airports and emergency services.
When searching for local police frequencies on RadioReference.com, choose Databases at the top of the home page. From there, select your state and municipality on the map or choose from the options listed underneath the map. Choose from state, frequency or FCC license. When you search each individual location page, you find specific frequencies listed underneath the map. You can also choose Live Audio to hear the Internet rebroadcasts of certain frequencies.
There are many different types of communication systems used by police and other emergency officials, so you may need different types of scanners, notes Scanner Master Corporation. Generally, the three main scanner systems used are trunking analog, digital and analog. Basic FM and AM signals are picked up by conventional analog scanners, as well as amateur radio stations and police frequencies. Racing frequencies, air frequencies, excluding military, and railroad frequencies can also be picked up by conventional analog scanners. The more complicated analog signals are picked up by trunking scanners. Digital frequencies are picked up by digital scanners.