Going to take a page out of the Operations reference book and hope it helps.
Chief Officers:
All chief officers and aides report to the command post with their post radios.
The first battalion chielf to arrive is the inital Incident Commander, establishes a command post, and gives the second engine officer a post radio to take to the Fire Sector. The building internal communication system, if there is one, may be used to direct and control evacuation. The IC announces the attack and evacuation stairs, relays information from the dispatcher and the lobby phone system to Operations and Search and Evacuations, stages units in the lobby, controls elevators, and uses the third and fourth engine company chauffeurs to handle occupant calls.
The second battalion chief is the Fire Sector (fire floor and floor above) supervisor and manages the first and second hose lines as well as WCD & HRN operations. Other tasks include controlling ventilation ordered by the Incident Commander, keeping the evacuation stairway smoke free and the attack stairway uncrowded.
The Deputy Chief becomes the Incident Commander; the original IC generally is assigned to assist but may be used in another role. A command radio channel is established when more than one group or sector is operating. The IC ensures sufficient resources are available, checks search status, and develops alternate attack strategy if needed.
Hope this helps if not sorry