The B46 External Annunciator is an optional module that uses audio and LEDs to show System Trouble, Power, and Battery status through a knockout on select enclosure doors. System overview The B46 is an optional module that provides external module LED and sounder status when installed in a supported enclosure. The module has 3 LEDs (System Trouble, Power, and Battery) which illuminate through the B46 LED cover. The LED cover snaps into a knockout in the enclosure door.