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Digital Radio

Some new radio systems use digital voice transmission in order to improve sound quality and to provide immunity from interference. These radios digitize the voice signal by converting it into binary data before transmitting it. The receiving radio then turns this digital data back into a voice signal. A person listening to such digital signals without the correct decoder will simply hear loud noise. Some police, fire, local government, and even business radio systems are starting to use these digital protocols. The most common digital protocol, or format, is called APCO Project 25 Digital Voice Modulation, often referred to simply as APCO-25. Digital protocols like APCO-25 may be used with either conventional or trunked radio systems. Fortunately, there are now scanner radios available that can receive APCO-25 digital voice modulation, listed in Category 5: Digital Trunking Scanners. Other digital formats and digitally encrypted signals currently cannot be monitored on any radio scanners.  Fortunately, few departments use these other digital formats. 

If any of the police, fire, or other services you would like to hear in your area use the digital APCO-25 format, regardless of whether the system is in conventional or trunked mode, you will need a police scanner in Category 5.  For more information on digital scanners, please see the page on picking a digital scanner.  For a side-by-side table comparing models, please see Category 5: Digital Trunking Scanners.  Please note that all Category 5 scanners can also monitor analog conventional and analog trunked systems.  If some departments in your area use analog systems and others use digital, a Category 5 scanner will be able to monitor both.  

Trunked Radio Systems
Skip Ahead to Part 4: Table of Listening Topics and Scanner Categories
Part 3A: Land Mobile Radio Systems

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