TWO-WAY TELEVISION 



By Hi'jiuERT E. Ives 

 Electro-Optical Research Director, Bell Telephone Laboratories 



[With 6 plates] 



Ever since the initial demonstration of television both by wire and 

 by radio at Bell Telephone Laboratories in 1927, experimental work 

 has been steadily pursued in order to learn the problems and the 

 possibilities of this newest branch of electrical communication. The 

 latest development to be demonstrated is that of two-way television 

 as an adjunct to the telephone. As a result of our development 

 work, there is now ^ set up an experimental and demonstration system 

 between the headquarters building of the American Telephone & 

 Telegraph Co. at 195 Broadway and the building of the Bell Tele- 

 phone Laboratories at 463 West Street, New York City, 2 miles 

 away. This system makes it possible to experiment with a method 

 of communication in which the parties engaged not only speak with 

 each other but at the same time see each other. Study of this 

 system will serve to give information on the importance of the 

 addition of sight to sound in communication and will give valuable 

 experience in handling the technical problems involved. 



In principle the 2-way television system consists of two complete 

 systems of the same sort as those used for 1-way transmission in the 

 demonstration from Washington to New York City in 1927. In 

 place of a scanning disk and set of photo-electric cells at one end 

 for generating the television signals and a single disk and neon lamp 

 at the receiving end for viewing the image, there are in the 2-way 

 system two disks at each end and a bank of photo-electric cells 

 and a neon lamp at each end. One of the disks, which in the sys- 

 tem as constructed, is of 21-inch diameter, serves to direct the scan- 

 ning beam from an arc lamp onto the face of one of the parties 

 to the conversation. Three banks of photo-electric cells, making 12 

 in all, are arranged at either side and above the person's face and 

 serve to pick up the reflected light and generate the television signals. 



* Reprinted by permission from a pamphlet Issued by the Bell Telephone Laboratories. 

 »Apr. 9, 1930. 



297 



