Primary responsibility for calls for police service are seven operations divisions based on geographical subdivisions of the city. Each operations division is commanded by a deputy chief of police. The divisions are designated Central, Northeast, Southeast, South Central, Southwest, Northwest and North Central and operate from facilities which are referred to as substations. Each operations division's geographical area is further subdivided into sectors which are composed of beats, each of which is normally patrolled by a uniformed officer or officers in a marked squad car. Calls for service are received primarily through the city's 9-1-1 system which is answered by a city-operated emergency communications center. Each substation also has an investigative unit with detectives who are assigned cases of burglary and theft which are committed within the area covered by their division.