User Organization Responsibilities for the Government Emergency Telecommunications Service and Wireless Priority Service [open pdf - 488KB]
From the Introduction: "The Government Emergency Telecommunications Service (GETS) and Wireless Priority Service (WPS) support national leadership; Federal, State, local and tribal governments; and other authorized national security and emergency preparedness (NS/EP) users. GETS provides priority access and prioritized processing in landline networks, and WPS provides the same in all nationwide and several regional cellular networks. GETS and WPS are intended to be used in an emergency when the landline or wireless networks are congested and the probability of completing a normal call is reduced."
U.S. Department of Homeland Security: https://www.dhs.gov/