IMAGE TRANSMISSION SYSTEM 469 



early use. At the present time, however, the terminal apparatus is 

 complex and bulky, and requires the services of trained engineers to 

 maintain and operate it. In addition to the cost of the terminal 

 apparatus there is the unescapable item of a many-fold greater trans- 

 mission channel cost. Because of the wide transmission bands re- 

 quired for the television images, the inherent necessity for a television 

 channel in each direction, and the extra channels for synchronizing 

 and signalling, the total transmission facilities used in this demonstra- 

 tion are those which could, according to current practice, carry about 

 fifteen ordinary telephone conversations. It is to be expected, of 

 course, that development work will result in some increase in the 

 efficiency of the transmitting channels and in simplifications of the 

 terminal apparatus. It is conceivable, therefore, that our present 

 conception of the cost of the whole system may ultimately be materially 

 changed. 



