Alarm shown in ON position in simulator. The Normal OFF is to open SPST switch left of lamp, which is (or 6 volt D.C. buzzer).
Bottom parallel lines is water pipe with water pumped from a river and old steam gauge screwed into water pipe. All has been removed from this gauge except the expansion tube.
Electrical contacts added to steam gauge at tip end of expansion tube and copper screw connector through mica insulator cut out area of side of case. Low water pressure allows expansion tube to make contact with copper screw setting alarm circuit in action.
