A New Telephotograph System * 



By F. W. REYNOLDS 



Transmission of photographs over telephone wires was begun com- 

 mercially several years ago, but recent improvements have increased to 1 1 by 

 17 inches the size of photograph that could be transmitted and have made it 

 possible for the picture to give much more information. The new machines 

 used for sending and receiving photographs are described in this paper, and 

 the requirements and control of the wire system necessary to prevent im- 

 perfections in the picture and to permit switching of sending and receiving 

 stations are discussed. 



A TELEPHOTOGRAPH message service between New York, 

 Chicago, and San Francisco was initiated in April 1925 by the 

 Bell System, and was extended during the following two years to five 

 additional cities. Experience in the operation of this service, using 

 equipment previously described,^ indicated that a number of improve- 

 ments were desirable in order to meet more satisfactorily the apparent 

 requirements of this form of communication. Development work 

 was undertaken to effect these improvements, and this paper describes 

 the new equipment and some of the features involved in establishing a 

 leased wire telephotograph network connecting 26 cities as shown in 

 Fig. 1. 



During the eight years of operation of the first Bell System tele- 

 photograph service the performance of the system was observed, 

 analyses made of the material transmitted, and opinions formulated 

 regarding the acceptability of the received pictures. The early 

 equipment required the preparation of the material for transmission 

 as a film transparency in an area not exceeding 4j inches by 6^ inches. 

 This relatively small image field combined with the use of 100 scanning 

 lines per inch and the added photographic operations to prepare the 

 material for transmission were considered as limiting the usefulness of 

 this new service. For example, in transmitting many of the forms of 

 printed matter it was necessary to divide the copy into overlapping 

 sections, to transmit each piece separately and to assemble the sections 

 as a composite picture at the receiving point. Obviously this pro- 

 cedure could not be applied advantageously to a photograph or news 

 picture and therefore the maximum information content of such 

 transmissions was limited by the small size of image field and the 



* Published in Electrical Engineering, September 1936. Presented at A. I. E. E. 

 Southwest District meeting, Dallas, Texas, October 26-28, 1936. 

 1 For all numbered references see list at end of paper. 



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