Dispatchers 3rd Alarm

[fltpara16]

I know this may have been explained before on this forum, but I cannot find the thread.  I was reading in the most current WNYF an article about a collapse at a fire on Jennings Street in 1974.  In this article, it is referenced that when additional assistance was requested, a dispatchers 3rd alarm was transmitted.  Can anyone explain what constitutes a dispatchers 3rd (or other) alarm? 

 

[68jk09]

An Alarm not ordered by the IC but rather transmitted by the Boro Dispatcher because the amount of Units special called is the equivalent of the next higher Alarm.

 

[fltpara16]

Thanks Chief.

 

[wfd444]

In the days of run cards did dispatchers also hit a higher alarm if there were not enough assigned units to equal the companies required? because of units out on other jobs? instead of available ?