You may be hearing the dispatcher reference the single letter and the number that correspond to the channel assignment within the radio itself (the 'B1' component that you gave in your example) - so that responders know what to actually select when they flip dials on the radio itself - they are physically flipping one dial to "B" and another to "1," hence getting to the right channel (talkgroup).......followed by the dispatcher annunciating the numerical "name" of the talkgroup (fire talkgroup 2 in your example). To avoid confusion, when you read through the database listing for fireground talkgroups (example B1TAC12)....just pay attention to the last two digits....in this case, the talkgroup would be identified as "1-2" on air.
Our database includes the standard fire dept radio channel plan above the actual listing of talkgroup text tags and related ID's....so you can flip through and get an idea of how things are layed out. Here in Balt Co, there is a single dispatch takgroup....and the county is split into 3 sections (East, Central & West)....with each section having its own 'response' talkgroup. There are many other talkgroups set aside for fireground/rescue operations. Quite a learning curve with the 996, if you are jumping up from an 800xlt.
http://www.radioreference.com/apps/db/?sid=189
