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POPULAR SCIENCE MONTHLY 



the other, press the upper one steadily while pushing the lower one. If the line 

 is not being used, your bell will ring every time you press the lower knob. 

 If the line is in use, your bell will not ring. As soon as you hear the op- 

 erator, give him your name and the name of the person to whom you wish to 

 speak; then replace the telephone on the hook. When the person called for is 

 connected with your wire, your bell will ring. Be sure, on removing the tele- 

 phone again, to turn the hook switch as before, unless notified by the central 

 office to turn in an opposite direction. When you are notified by the central 

 office that a person wishes to speak to you, keep the telephone at your ear, as 

 the person will be ready to speak as soon as you are notified. 



Owing to the rapidity with which improvements and modifications 

 in equipment appeared during the first five years, rarely did the sub- 

 scribers in any two exchanges have the same type of instruments, the 

 newer exchanges having the later types except where the most rigid 

 economy was practised. Yet it often happened that when the patrons 

 in one town learned that the subscribers in an adjoining town had a 

 later type of instruments, the local owners were given no rest until 

 up-to-date instruments were installed, even though the equipment 

 declared to be antiquated and obsolete had been in use only from 

 twelve to eighteen months. 



UN £ 



Fig. 28. 



