Wire Transmission System for Television^ 



By D. K. GANNETT and E. I. GREEN 



Synopsis: This paper deals with the transmission problems which were 

 met and solved in connection with providing wire circuits from Washington 

 to New York for the television demonstrations which took place on April 7, 

 1927, and following. For transmission of the television images a single 

 transmission channel was set up combining the frequency ranges usually 

 assigned to telegraph, telephone and certain carrier channels. The special 

 line requirements were met so successfully that the television images 

 transmitted from Washington were indistinguishable from those trans- 

 mitted locally. 



Introduction 



A SYSTEM of television, to be worthy of the real meaning of the 

 name, must be capable of operation over a considerable distance. 

 Spanning this distance, there must be a connecting medium suitable 

 for faithfully transmitting the television currents. This paper de- 

 scribes how the connecting medium was provided between Washington 

 and New York for the recent television demonstrations,- by adapting 

 to this purpose existing wire facilities of the Bell System. 



Fortunately, wire facilities of the type which were available between 

 Washington and New York had been utilized for some time to transmit 

 simultaneously many telephone and telegraph messages, involving a 

 frequency range more than ample for the television requirements, 

 so that the transmission characteristics of the lines throughout the 

 necessary range of frequencies were well known. The matter of 

 providing a suitable channel to carry the television currents consisted, 

 therefore, in throwing together the frequency ranges which had hereto- 

 fore been utilized for providing a number of separate telephone and 

 telegraph channels. In addition to providing this very wide band 

 communication channel it was necessary to apply special distortion- 

 correcting networks so that the overall channel would possess proper 

 characteristics and also to take care to avoid introducing disturbances 

 due to such things as line irregularities, noise, etc. 



Due to the perfection of the transmission methods which were 

 utilized, it was found that when the circuit was first established, in 

 accordance with the requirements which had been deduced, the 

 television images transmitted from Washington were indistinguishable 

 in quality from those transmitted locally, this result being secured 



1 Presented at the Summer Convention of the A. I. E. E., Detroit, Mich., June 

 20-24, 1927. 



2 "Television," H. E. Ives; "The Production and Utilization of Television 

 Signals," F. Gray, J. W. Horton and R. C. Mathes; "Synchronization in Television," 

 H. M. Stoller and E. R. Morton. 



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