Annunciator

An annunciator is a device or panel used in monitoring and warning systems to convey the status of equipment, processes, or environments. It typically provides visual and sometimes audible indications of normal, warning, and fault conditions. Annunciators may be standalone units, or part of a larger control system such as a programmable logic controller (PLC) or supervisory control and data acquisition (SCADA) system.

In operation, an annunciator receives signals from sensors, relays, or controllers and translates them into human-perceivable alerts. Visual indicators—commonly colored lamps or LEDs—show the affected system, while audible alarms or tones may accompany critical conditions. Modern annunciators often include digital displays, event logs, time stamping, and alarm prioritization, and can route notifications locally or to remote monitoring stations.

Configurations vary: conventional panels use banks of indicator lamps with associated pushbuttons for acknowledgement; modern implementations may be full digital panels or software-based annunciation within HMI systems. Features may include historical logging, maintenance reminders, and integration with fault-tolerant alerting schemes.

Applications are widespread in industrial facilities, power plants, data centers, transportation systems, and aviation cockpits, where rapid awareness of equipment status is essential for safety and reliability. In aviation, the term describes cockpit displays that inform pilots about the status of subsystems.

History and development: annunciators originated with electromechanical alarm panels and have evolved into integrated alarm management tools within modern automation and control architectures.

See also: Alarm system, Indicator, Human-machine interface, SCADA, PLC.