EXTENSION OF THE TELEPHONE SYSTEM TO SHIPS 181 



niinal, New York City station ot the Radio Corporation, and the 

 telephone at our Deal Beach, New Jersey, station. The telegraph 

 transmitter was of the continuous wave, vacuum tube type manu- 

 factured by the General Electric Company. The telephone and 

 telegraph sets used individual antennas on the ship. 



Altho certain apparatus difficulties were experienced aboard the 

 vessel because of the short notice at which the tests were made, 

 nevertheless the tests were successful and demonstrated that a tele- 

 phone set can be made to operate simultaneously with a suitable C. W. 

 (continuous wave) telegraph transmitter. The final solution of this 

 problem of simultaneous operation, however, will undoubtedly require 

 further work in co-ordinating the two types of systems, in order to 

 permit them to be operated on wave lengths relatively close together. 

 During the tests, the wave lengths were widely different, the telegraph 

 operating on about 2,100 meters and the telephone on about 375 

 meters. The work done at Deal Beach in the development of multi- 

 plex telephone operation, where three telephone channels were oper- 

 ated in the vicinity of 400 meters and a fourth channel was operated 

 for telegraphy at 600 meters, demonstrates that it should be feasible 

 to operate telephone and telegraph channels simultaneously on closely 

 adjacent wave length bands. However, in determining wave length 

 allocations, these limiting factors will have to be considered: first, the 

 greater susceptibility of the telephone to interfering noises, such as 

 beat tones, and second the fact that the telephone requires two bands 

 one for each direction of transmission and that these bands are re- 

 quired to be spaced a little apart in frequency. It is obvious that 

 by controlling both types of channels from the same station they 

 can be better co-ordinated in respect to frequency and general service 

 use than if operated from separate stations, so that combined tele- 

 phone-telegraph shore stations present interesting possibilities for the 

 future. 



Another method of operation, and one which requires fewer wave 

 lengths, is that of superimposing the telephone and telegraph channel 

 on the same carrier wave after the general manner of compositing 

 long distance telephone lines with telegraph. This can be done by 

 combining the two channels on one circuit as is done in wire practice 

 and then modulating the combined channels upon the radio carrier. 

 At the receiving end both channels can be detected simultaneously 

 and then the channels separated by composite sets or filters. This 

 method is mentioned to show the ultimate possibilities of combined 

 operation and is not put forward as one which is sufficiently practical, 

 all things considered, for use in the art of the immediate future. 



