What is Annunciator?

Annunciator is usually an electrical device used to signal different events. For e.g. in a food court, you can have a token number. The token number for any order which is ready for service is usually flashed on a display board to notify. Another popular example is the extensions phones in hotels. The room number is flashed on the reception board. The device can be automated one also. For example fire alarms can notify a central monitoring system to show which room has caught fire.