MABAS - Mutual Aid Box Alarm System is just that a standard way for requesting mutual during a incident. Each fire department uses Box Cards that have the alarm levels and type of incident so when they get to a scene instead of trying to figure who int eh area has what and request they just give out a card number and dispatch can page out agencies off of that card, this saves a lot of time talking on the radio and finding resources. The MABAS channel can be for several things relating to Mutual Aid, however it is most likley for outside agencies to answer the page on.