I thought the beeps heard are just an attention signal. There is always two beeps for all calls, so how they be for different calls? Also if the dispatch calls the station ahead of time why bother with the radio dispatch, just tell them where to go on the phone.
stations get alerted several ways.
1)Printers are activated via a Land line, which is only able to receive messages from the department and dispatch center.
2)The CAD in the rigs.
3)The station tones and radio tone out. If the station has the "Xmas tree" on the wall or hanging from the ceiling then CAD is hooked into that for apparatus specific alerting. If the department doesn't use that method then the tones are set off when their specific tones get dropped.
it gets broadcast on the radio for several reasons....its a back up, the units out in the field hear the call go out, maybe the units being dispatched aren't at the station. several times here in Sacramento the CAD has gone down..and all units have to voice ALL traffic over the radio, in fact it happened just the other day for about 20mins.