A fire alarm which is both inexpensive and simple in construction is shown in the illustration. Its parts are as follows:
A, small piece of wood; B, block of wood nailed to A; S S. two pieces of sheet brass about 1/4 in. wide, bent into a hook at each end; P, P, binding-posts fastening the springs S S, to block B, so that they come in contact at C. W is a piece of wax crayon just long enough to break the contact at C when inserted as shown in the illustration.
When these parts have been put together in the manner described, connect the device in circuit with an electric bell, and place it behind a stove.
Simple Fire Alarm
When the stove becomes too hot the wax will melt at the ends, allowing the springs to contact at C, and the alarm bell will ring. --Contributed by J. R. Comstock, Mechanicsburg, Pa.