Telephotography 



In 1925 the Bell System inaup;urated between a limited number of 

 points a service for the transmission of photographs by wire. Such a 

 system involved the use of telephone circuits, the band of frequencies 

 required for successful transmission being approximately 800-1,800 

 cycles. This service was discontinued in 1933 because of lack of 

 commercial demand. 



At the present time the Bell System is providing to one of the press 

 associations special circuits for their use in transmitting photographs 

 with apparatus owned by them. The type of apparatus used for this 

 circuit is a Bell System development, and represents a marked advance 

 over the earlier apparatus, transmitting pictures at a higher speed and 

 requiring a band of frequencies of approximately 1,200-2,600 cycles. 

 Within the band of frequencies used for the picture transmission a very 

 high degree of equalization of attenuation and velocity of transmission 

 is required. This involves the use of apparatus designed specifically 

 for this service which is associated with regular telephone repeaters. 

 It also requires special attention on the part of the operating forces. 



Other Special Services 



The Bell System gives an extensive private line telephone service. 

 The requirements for circuits for this service are similar to those for 

 telephone message service and do not require any special discussion. 



Also, the toll plant of the Bell System is from time to time used in 

 a limited way for other special services. The private line telegraph 

 service and teletypewriter exchange service are not discussed here, 

 being outside the scope of this statement. 



Toll Operating Methods 



Operating Method Defined 



By "toll operating method" is meant the process by which a toll 

 call is received, recorded, completed and timed. This process is 

 referred to as " handling the call." It relates, for the most part, to the 

 routine and procedure of handling the call, although it must conform 

 to the type of equipment provided, the trunking method involved and 

 the arrangement of the plant. During the development of the 

 telephone business many different toll operating methods have been 

 used, but in the following only the five are described which at various 

 times have come into general use and by which the vast majority of all 

 toll calls have been handled. Such questions as the following are 

 involved in the toll operating method: 



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