Firefighting jargon includes a diverse lexicon of both common and idiosyncratic terms.
Furthermore, a department may change a definition within its SOP, such that one year it may be RIT, and the next RIG or RIC.
The variability of firefighter jargon should not be taken as a rule; some terms are fairly universal (e.g. stand-pipe, hydrant, chief).
But keep in mind that any term defined here may be department- or region-specific, or at least more idiosyncratic than one may realize.
Also, an antiquated term for an alarm system which predated telephones, where boxes were located on street corners in urban areas and connected to the nearest fire station.