Most local jurisdictions (towns, cities and counties), and special districts (schools and hospitals) have the umbrella configuration in which the DPS is simply a joint administration of several distinct agencies. They may share administrative support staff and back-office functions, but sworn personnel remain specialized and have particular responsibilities (that is, the police continue to arrest people and the firefighters concentrate on firefighting and EMS functions).
However, a minority of jurisdictions have a Department of Public Safety model which provide primary and direct responsibility for all emergencies. In these unique organizations, all full-time sworn personnel are cross-trained as police officers, firefighters and/or EMTs, and can respond to emergencies in any capacity. Although it is more expensive to hire, train, and retain such personnel, they have a clear advantage in terms of their flexibility. Public Safety Officers can respond as first responders to many rapidly evolving situations rather than waiting for the arrival of other specialized personnel.