TELEVISION IVES 301 



This loud sj)eaker is of the moving coil type with a small piston 

 diaphragm. 



In any system such as that described, the microphone is not capable 

 of distinguishing between the sounds from the local speaker or from 

 a speaker at the remote end of the circuit reproduced locally by the 

 local loud sjjeaker. If the sounds from the local loud speaker 

 should be impressed upon the local microphone in sufficient magni- 

 tude, " singing " would result, and the system be no longer operable. 

 To prevent this the microphone and the loud speaker are installed 

 in carefully chosen positions and the inner surfaces of the sound- 

 proof booths are specially treated to prevent as much as possible 

 the reflection of sounds from the walls into the microphone. Under 

 these conditions, the attenuation of sounds transmitted is of about 

 the same magnitude as would be experienced if the listener were, 

 say, 10 or 12 feet away, but in the same room. This acoustic illusion 

 of distance is in harmony with the visual appearance of the television 

 image. 



In addition to the television synchronizing and acoustic circuits, 

 others are provided for signaling and monitoring purposes. Matters 

 are so arranged that an operator can see both the outgoing and in- 

 coming image, and by means of movable lens and prism systems 

 can insure that the scanning beam is properly directed to correspond 

 to the height of the observer, and that the magnifying lens in front 

 of the receiving disk directs the image to the observer's eyes. 



Operating arrangements are made so that the two parties to the 

 conversation, after taking their positions in the booths, do not see 

 or hear each other until adjustments are made, whereupon the 

 operators expose the images and connect the talking circuits simul- 

 taneously. The experimental service is arranged on an appointment 

 basis. The two parties to the conversation, having arranged with 

 attendants at the two stations for their time, proceed to the respective 

 booths, where they are ushered into chairs in position before the 

 photoelectric cells and instructed as to the operation of the system. 

 Immediately the attendant closes the booth door, the operators make 

 the necessary adjustments; and the simultaneous sight and sound 

 communication is carried on until, upon the parties leaving their 

 chairs, the connections are interrupted. 



