MACHINE Sir ITCHING TELEPHONE SYSTEM 89 



plant of a big city, is a large one. It is impracticable to introduce it 

 all at once. Its introduction must be effected gradually and this is 

 accomplished by using it for growth and such replacements as are 

 necessary, later extending its use as conditions warrant. 



The fundamental engineering studies which have to be made and 

 which must precede the manufacture and installation of the equip- 

 ment for a machine switching office are, in all important respects, 

 the same as those which must precede the manufacture and installa- 

 tion of the equipment in a new manual office. They involve a careful 

 study of the telephone needs of the area, with a view to determining 

 ultimately the quantities of the different kinds of arrangements neces- 

 sary to give the service. This requires a study of the commercial 

 requirements at the time when the equipment should be cut over and 

 for several years thereafter. Data must be collected as to the prob- 

 able rates of calling, the average duration of the calls and the amount 

 of trunking to and from other offices. 



With these data available, the size and arrangement of the trunk 

 groups on the selector frames, the number, grouping and type of 

 selectors and senders required, and the size of the power plant can be 

 determined. From this the cabling arrangement can be worked out, 

 and suitable floor plans prepared. 



Manufacturing specifications can then be prepared in accordance 

 with which the equipment of the office is manufactured and installed. 

 Before the equipment is cut into service, the various arrangements are 

 thoroughly tested individually, and when in proper condition the 

 whole is checked up by making complete operation tests. 



If time and space permitted, it would be of interest to discuss the 

 methods of actually cutting the equipment into service, and the 

 comprehensive program which is worked out for the training of the 

 employees who are to handle the equipment and advising the public 

 which is to use it. All these matters are of the utmost importance, 

 and must be carried out systematically in order that there may be 

 no reactions on the general service at the time of the cut-over. 



