184 BELL SYSTEM TECHNICAL JOURNAL 



adjustment of the transmission conditions of t lie circuit and 



for a diligent maintenance of these adjustments during oper- 

 ation. 



(5) In the experiments in multi-channel operation and in simul- 

 taneous telephone and telegraph transmission from the same 

 vessel, a beginning has been made in one of the most important 

 problems concerned with the early application of radio telephony 

 to the marine service, namely, that of the co-ordination between 

 radio-telegraph and radio-telephone transmission. It is obvi- 

 ous that the general development of the art of selective trans- 

 mission, as well as the entrance of radio telephony, calls for 

 the use of purer carrier waves and of a minimum transmission 

 band in radio telegraphy. 



(G) As regards the important question of wave lengths, the develop- 

 ment has shown that the relatively short waves employed in 

 the experiments are satisfactory up to several hundred miles 

 but that for longer distances longer wave lengths will be re- 

 quired. The difficulty of obtaining for the marine service a 

 wave length sufficiently wide for permitting the handling of 

 any considerable traffic is obvious. The band which can be 

 allocated to this service will naturally be limited by the require- 

 ments of other services; and the intensiveness with which this 

 band can be worked by closing up the frequency spacing be- 

 tween channels is limited by the consideration of intercom- 

 munication between different types of systems and by apparatus 

 expense. 



In general it may be said that the present development has con- 

 tributed to the communication art the means whereby the universal 

 land line telephone system may be extended to ships at sea. The 

 actual giving of such service must await the working out of the econ- 

 omic problems involved and the necessary business and organization 

 arrangements between the communication companies and the steam- 

 ship companies. 



