TELEPHONE SYSTEM OF THE UNITED STATES 27 



selectors, makes possible economies in interofifice trunks and a reduc- 

 tion in the number of selectors involved in completing a connection 

 in a large exchange. The selection may be either to a dial office or 

 to a manual office reached direct or through a tandem switchboard. 

 Figure 19 illustrates the apparatus for five senders. A switchroom 

 in a typical panel office is shown in Fig. 20. 



Buildings 



The buildings in the Bell System at present number about 6,000, 

 excluding those occupied by the Western Electric Company. All of 



Fig. 21 — Telephone office in the residential district of Silver Spring, Maryland. De- 

 signed for small manual switchboard with a present capacity of 2,200 lines. 



the larger and many of the smaller are owned by the telephone com- 

 panies. The range in size of the buildings is illustrated by Fig. 21 

 showing a small building for a single manual switchboard with a present 

 capacity of 2,200 lines, and Fig. 22 showing a headquarters office 

 and equipment building in a large city. This building has 66,000 

 square meters of floor space, in the lower 9 floors has space for dial 

 equipment to serve 100,000 telephones, and in the upper floors in- 

 cludes offices for 5,000 people. Figures 23 and 24 further illustrate 



