+----------------+ +----------------+ +----------------+
| 火警自動警報設備 |-->| 連動切換裝置 |-->| 緊急廣播設備 |
+----------------+ +----------------+ +----------------+
| |
v v
+----------------+ +----------------+
| 手動報警設備 | | 火警警鈴 |
| (火警警鈴) |<---| (暫停鳴動) |
+----------------+ +----------------+