Voice Encryption for Radios / National Institute of Justice, March 2007
http://www.ojp.usdoj.gov/nij/pubs-sum/217103.htm
"This NIJ InShort fact sheet gives an overview of the weaknesses unencrypted voice transmissions face and outlines how voice encryption helps ensure that voice transmissions are secure and accessible only by authorized personnel. Effective management is crucial to successfully implementing an encrypted voice network, and the fact sheet indicates the differences between managing a small versus a large network."