720 BELL SYSTEM TECHNICAL JOURNAL 



Because of the advantages to be obtained in circuit operation from 

 closer voltage regulation and because of the higher cost of manual 

 attendance, automatic regulators for machines and batteries will be 

 used more extensively. Further attention will be given to the auto- 

 matic operation of power plants, successfully accomplished for private 

 branch exchanges and small offices. 



Entirely automatic power plants for large ofltices could, it is believed, 

 be developed without great difficulty somewhat along the lines of the 

 automatic substations in use by some of the power and traction com- 

 panies. These should, in general, require attention only periodically 

 for cleaning, replacing worn parts, adjusting," etc., except during a 

 failure of equipment or some other abnormal condition which would be 

 indicated by an alarm. Since full automatic control would probably 

 cost more than that requiring a limited amount of supervision, a study 

 is required to determine how nearly automatic the equipment should 

 be made for offices where an attendant will be required in any case for 

 some of the equipment. 



As for machines generally, the tendency will be towards greater use 

 of more nearly commercial designs, construction and finish, eliminating 

 as many as possible of the special features formerly necessary but not 

 now required with changed conditions and the supplementary appa- 

 ratus which recent developments have made available. 



A more extended use of filters in power plant circuits may be 

 expected. 



In the direction of power supply, efforts have for some time been 

 applied with some measure of success toward increasing the reliability 

 of the service from outside, which work usually consists of cooperation 

 with the electric supply companies in investigating conditions under 

 which independent duplicate power services can be secured. The 

 securing of reliable duplicate services permits elimination of a local 

 emergency generating plant such as the engine-generator sets. As 

 these efforts become more successful and the public service systems 

 increase in extent and in reliability with the increase in interconnection, 

 it should be found possible to reduce the amount of storage battery 

 reserve in telephone power plants. Experimental introduction of low- 

 voltage alternating-current networks similar to the direct-current 

 networks used in the central parts of some large cities is being watched 

 with interest and some installations are in progress. Although this 

 might be classed as one electrical system, the safeguards against failure 

 and the duplication of equipment is often such as to warrant entire 

 dependence upon this power without a separate emergency source in 

 the building. 



