32 BELL SYSTEM TECHNICAL JOURNAL 



buildings which adequately, economically and comfortably house the 

 equipment and personnel — both initially and throughout the useful 

 life of the building — and which at the same time are outstanding and 

 attractive, appropriate to their surroundings and a continuing source 

 of satisfaction to the communities in which they are erected. 



The initial size of a building is determined by the costs and rate 

 of increase in space requirements, with due regard to the service 

 reactions caused by extensions of the building which is being used for 

 operating purposes. As a result of these considerations central ofifice 

 buildings are usually designed with a capacity of about twice the 

 initial requirements. In many cases space provided for later exten- 

 sions of equipment is used temporarily for office space. Possibilities 

 of future extensions of the buildings are provided for either by buying 

 more land than is required for the initial building, thus making pos- 

 sible lateral extensions, or by providing strength in the steel frame- 

 work for future vertical extensions. The possibility and type of 

 future extensions must, of course, also be taken account of in the 

 architectural design. 



Floor plans have been developed representing for typical conditions 

 the best arrangements of the various types of central office equipment 

 both manual and dial. The use of these uniform floor plans greatly 

 facilitates the engineering, manufacture and installation of the equip- 

 ment, and results in savings of both time and money. A uniform 

 floor plan applying to a step-by-step dial office is illustrated in Fig. 25. 

 The relative location of the different frames and aisle space as well 

 as the unit size of the frames is fixed but the number of frames is 

 varied to meet the requirements of individual cases. 



Except for the smallest buildings, non-combustible construction is 

 used, a steel or reinforced concrete frame and brick or stone curtain 

 walls being employed. The very small buildings, except where severe 

 fire exposures are encountered, are of frame or brick and joist con- 

 struction. 



Rural Service 



Surrounding the larger cities and towns there is in general a sparsely 

 settled district developed on a multi-party basis. Service is given 

 on common battery lines where the distances are not too great and 

 either semi-selective or code ringing is used. These lines usually 

 serve not more than six or occasionally eight parties and the common 

 battery signaling requirements limit the range to about se\'en or eight 

 kilometers. 



