So basically if example L-111 gets a job
Then there's a list of companies who goes to them on a relocate.
First up is L-124 if not available then L-120 next is L-119
But what if all those companies are available IE on another run or OOS Then what do you do?
What if the 4th company that is on the list is L-146 and they have old rig and can't relocate Then what?
What if there is a job a block away from L-111 and the relocator is at the quarters of L-111 and the IC needs a TL or a ladder company ASAP
But certain people don't want that relocator going to a job so instead they call for a TL that's 10 mins or more away at their fire house because they are next on the ticket they have to go and there is a loss of life.
What's going to happen when people question why that company a block away wasn't called in stead they had to wait for the one 10 or more mins away
In an AVL system, an available unit is assigned based on its actual location.
In a non-AVL system, an available unit is assigned (and becomes unavailable) and replaces another unit, making that unit available. The unavailability of the relocator is concurrent with the availability of the relocatee, regardless of how long it takes to happen.
As an example:
If E258 was relocated to E265,
with AVL, E258/265 could be picked for a call anywhere along the way from 258's quarters to 265's quarters.
Without AVL, E258 becomes E265-acting upon assignment. The CAD sees E265 as available and E258 as unavailable. E258/265 may pass occupied firehouses enroute to a call in E265's area, but would not be assigned a block from their own quarters even if they are just leaving.
This is where situational awareness by the Dispatchers is crucial. Situational awareness is not to be confused with discretion.
This is a general explanation of CAD systems. The specifics of FDNY are better explained by others.