XVIII ELECTRIC BELL OUTFIT FOR THE COTTAGE The boys asked me what arrangement of electric bells we needed at the cottage and so I gave them this problem to work out by themselves: 1. We want a bell in the kitchen to be rung by a push button at the front door. But there are times when no one is in the kitchen and hence, 2. We want a bell upstairs to make a single stroke whenever the kitchen bell is rung from the front door. 3. We want a floor push under the dining-room table which will cause the kitchen bell to ring a single stroke. 4. We want a push button in the dining-room which will cause both bells to clatter and call people from their beds, from the piazza, the lawn, etc., to their meals. This equipment needs only one battery of two dry cells, two bells, three push buttons and about two hundred feet of wire. It should cost less than five dollars. The boys drew many plans and tried many schemes and at last determined upon the plan shown in Fig. 173. _P_ is the floor push under the dining-room table. When the circuit is closed at this point the current leaves the battery from the carbon pole _c_, passes up and around the magnets of the kitchen bell and back to the zinc pole of the battery _z_ by way of the push button _P_. All other circuits are open. [Illustration: Fig. 173] _P´_ is the push button at the front door. When the circuit is closed at this point the current leaves the battery at _c_, passes up to the right-hand binding post of the kitchen bell and divides, part going through each bell. The portion of the current which goes through the kitchen bell passes around the magnets and through the armature to the left-hand binding post before it can find a path back to the battery. Hence, the kitchen bell clatters. The portion of the current which passes to the upper bell goes around its magnets and finds a path back from the middle binding post to the battery by way of _P´_. Hence the bell upstairs rings with a single stroke.