This alarm rings so that callers approaching the door may be seen before they ring the bell and one can exercise his pleasure about admitting . If one has a wooden walk, the alarm is easy to fix up. Take up about 5 ft. of the walk and nail it together so as to make a trapdoor that will work easily. Place a small spring under one end to hold it up about 1/4 in. (A, Fig. 2). Nail a strip of tin along the under side of the trap near the spring and fasten another strip on the baseboard, so that they will not touch, save when a weight is on the trap. Connect up an electric bell, putting the batteries and bell anywhere desired, and using rubber-covered wire outside the house, and the alarm is complete.
Illustration: Alarm Rings When Caller Approaches
When a person approaching the house steps on the trap, the bell will ring and those in the house can see who it is before the door bell rings. --Contributed by R. S. Jackson, Minneapolis, Minn.