In the past, law enforcement officers rarely had to communicate with officers outside their department. Most departments used one-channel conventional radios to communicate with officers in the field. Since everyone shared the channel, codes were needed to pass concise information with a minimum amount of radio time. However, there was no uniformity in the codes, which made inter-jurisdictional communication difficult.
Agencies now must be able to communicate effectively across jurisdictions, and using plain language helps. The Department of Homeland Security encourages plain language in its National Incident Management System. It encourages (1) law enforcement agencies to commit to a plan and outline the necessary steps, (2) each agency to keep a small subset of agency-specific codes, and (3) the standardization of certain terms (i.e. GTA for grand theft auto).
