Bases support the command post during an incident, by managing essential tasks, primarily coordination and administration of logistical functions in contrast to the command post which is the location of the Incident Commander (IC).
Overall communications are greatly simplified as all participants know to whom they report. Radio traffic to the Incident Commander is limited to necessary members of the command staff.
Since the person filling the Incident Commander post may change several times, it should be apparent why tactical (functional) call signs are required in the ICS. Rampant confusion would ensue if every time the person holding that position changed the radio call to that persons name.
Tactical calls may include Staging Area, Operations, Logistics all of which are FUNCTIONS, hence some call tactical calls 'functional calls' as a manner of explanation. You can imagine the confusion if there were several Engine 1's on the same strike team. Also, it is usual for strike teams to be given a numerical call, such as "Strike Team 71"; and for task forces to be "Task Force 22". (A task force is comprised of up to five dissimilar resources grouped for a specific task. A strike team is five of the SAME type of resource under a strike team leader, such as fire engines, bulldozers, etc.)
Other tactical call examples are: Group organizational elements with a PRIMARY job might such as "Fire Attack C" or "Fire Attack 5th floor" in a multi story incident. Division organization which is responsible for tactical operations within a defined location, may be "Division A"; or geographical such as "East Wing".
The Base location may be "Fairground Base" if located at the local fairgrounds, or "Joiner Base", if at the Joiner High School Football field. The Incident Command post may be at the base but is often elsewhere, and clearly and distinctly identified.
The most important number in the ICS is five (5). This is span of command, and is highly functional, being based on the concept that a leader can effectively manage 5 resources (people, units, etc.) Hence the strike team leader with 5, the sector officer with five strike teams; the division officer with five sector chiefs. In major wildland fires the amount of apparatus can be lined up for miles on a back road headed to the staging area. Without this standardized management system the efficiency that has been obtained with the ICS would have been non existent.
(Some of this summary came from the Jan 2001 "Net Control" of the County of Orange RACES, which quoted an article "Basics of the Incident Command System" in the Dec. 2000 Public Safety Communications by APCO International.)