7H BELL SYSTEM TECHNICAL JOURNAL 



employed between the two cities. These circuits were, for the most 

 part, in open wire although approximately 13 kilometers of specially 

 loaded cable were necessary at the ends in entering the cities. By 

 means of a separate talking circuit a person at one end of the system 

 could talk to, as well as see, a person at the other end. Systems of 

 approximately twice the detail and also systems adapted to the view- 

 ing of larger scenes such as athletes in action have since been developed 

 and demonstrated. 



Time Service 



Arrangements have been made in many parts of the country to 

 furnish subscribers who desire it, accurate information as to the time 

 of day. A subscriber wishing the information asks for or dials a 

 particular number assigned for this purpose and is connected either 

 to an operator who advises him individually as to the time or is 

 switched across a bus-bar to which is connected the amplified speech 

 of an operator repeating at fifteen second intervals the exact time 

 of day. In the present development of this service it is the practice 

 to localize in one place the time service for an entire exchange area. 



By-Products 



Certain interesting and important by-products of the telephone 

 development work justify a brief mention. Three arts separate from 

 the telephone art have been radically changed by such by-product 

 developments. These include submarine telegraphy, phonographs 

 and motion pictures. 



The changes in submarine telegraphy have resulted from develop- 

 ment by the Bell Laboratories of the materials known as " permalloy " 

 and " perminvar " which have unusual magnetic properties at low flux 

 densities. Submarine cables so loaded can transmit approximately 

 10 times as many words per minute in one direction as compared to 

 cables of the same weight as previously constructed. As such loaded 

 cables are not duplexed the effective increase in speed of transmission 

 is approximately five times. 



Development work in connection with the faithful recording and 

 reproduction of sound has greatly improved phonographs and their 

 records. The "Orthophonic Victrola" is an example of such devel- 

 opment. 



An extension of this work led to the development of the "talking " 

 motion picture. The systems known under the names " Vitaphone " 

 and "Movietone" followed from this work. Great interest has been 

 aroused in such systems in the amusement field in the United States, 



