352 HOW ELECTRICITY IS USED IN THE HOME 



can be bought for one or two dollars. The cost of opera- 

 tion is about the same as for renewals of batteries in the 

 older systems, but there is no trouble about having to re- 

 new batteries, which as a rule means an interval of time 

 when the bells will not ring. 



The telephone. -- The telephone can almost be called 

 the errand boy of the household. It is one of the big- 

 gest of labor savers. There are a number of complicated 



electrical devices in- 

 volved in the com- 

 plete equipment. 

 The receiver itself 

 has an electromagnet 

 in it and the vibra- 

 tion of an iron disk, 

 somewhat similar to 

 the vibration of the 

 armature of the elec- 

 tric bell, causes sound 

 waves which we hear. 

 A more complete ex- 

 planation of the tele- 

 phone will be given 

 when we study com- 

 munication at a fu- 

 ture time. 



Commercial mo- 

 tors in the home. - 

 The importance of 

 the electric motor in 



the home can well be appreciated when one stops to think 

 of the hard hand labor which is replaced by motor-driven 



Electric control of sewing machine. Find the motor 

 which drives the machine 



