A New Telephotograph System

T E L E P H O T O G R A P H 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,1 indicated that a number of improvements 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. D u r i n g the eight years of operation of the first Bell System telephotograph service the performance of the system was observed, analyses made of the material transmitted, and opinions formulated regarding the acceptability of the received pictures. T h e early equipment required the preparation of the material for transmission as a film transparency in an area not exceeding 4j inches by 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 m a n y 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.