A key to such communication are devices that interconnect diverse radio systems and allow responders from different organization to communicate during an operation. These are known as "interoperability" devices. Delaware has three large command units in service that are intended to operate together in responding to a major disaster. Each unit mirrors the others, and during a major disaster response can establish a combined unified command center. Each unit contains a SynTech RIOS (Radio InterOperability System). Johnson County, KS, developed a mobile command center from Farber Specialty Vehicles. Although facilitating a unified command was the primary goal of the unit, interoperability was an important secondary goal. The radio equipment includes an ACU-1000, which has been effective in connecting diverse radio systems in the field. Fairfax County, VA, recently held a mobile communications vehicle rally that involved nearly 12 local command units acting as they would during an actual combined deployment. The highlight of the rally was an interoperability exercise in which each of the trucks demonstrated its communications capabilities, with attention to how interoperability could be improved. True operational interoperability, as exemplified by the modern command vehicles described in this article, consists of being able to use all forms of communication--radio, satellites, cellular, microwave, and audio-video--within and outside the vehicle in order to conduct command and control for all agencies involved in an operation.