A warning device located inside a signal box or dispatch center that sounds when a train occupies a specific track circuit or trips a treadle. It gives the operator or dispatcher an immediate audible heads-up that traffic is entering their territory, prompting them to line switches and clear signals before the train has to slow down.
Heard on the job
The annunciator just dropped for the eastbound main, so get that crossover lined up.
Insider tip
Experienced dispatchers rely on the specific tone of different annunciators to know which track a train is on without even looking at the board.