in industrial process control, an annunciator panel is a system to alert operators of alarm conditions in the plant. multiple back-lit windows are provided, each engraved with the name of a process alarm. lamps in each window are controlled by hard-wired switches in the plant, arranged to operate when a process condition enters an abnormal state (such as high temperature, low pressure, loss of cooling water flow, or many others). single point or multipoint alarm logic modules operate the window lights based on a preselected isa 18.1 or custom sequence.