426 BELL SYSTEM TECHNICAL JOURNAL 



of a makeshift basis, in the absence of any comprehensive wavelength 

 plan for this new service. The Commission has recently had under 

 study the setting up of more adequate provisions for ship-to-shore 

 telephone channels, whereby it is hoped a series of frequencies may be 

 designated for telephone service exclusively and whereby there may 

 be established the relation between the telephone and the telegraph 

 frequencies necessary for the avoidance of interference between the 

 two services. Especially is coordination of the two sets of frequencies 

 necessary on the larger vessels, in order that simultaneous telegraph 

 and telephone service may be given without mutual interference. On 

 the larger liners simultaneous use of the radio telephone and radio 

 telegraph service must be provided for. This means that the trans- 

 mitters of both services must keep accurately on their frequencies and 

 be free of spurious components, and that the receivers must be highly 

 selective. It further entails that the transmitting and receiving 

 frequencies in each of the two cases be so coordinated that the trans- 

 mission frequency of one service does not lie too near the receiving 

 frequency of the other, and bespeaks a considerable amount of mutual 

 cooperation between the operating agencies involved. Difficulties of 

 fitting in the two services were encountered in the early work on the 

 Leviathan and, although the problem has not been worked out to final 

 solution, sufficient progress has been made, in cooperation with the 

 engineers of the Radio Corporation of America, to enable the telegraph 

 and telephone services to be conducted simultaneously without undue 

 interference. 



In view of the fact that ships of a number of nations are already pre- 

 paring to give radio telephone service on the transatlantic routes and 

 with the probability of this service also extending to other parts of the 

 world, it would appear to be a matter of importance that the whole 

 question of marine frequency allocations be worked out in the near 

 future not merely on a national but also on an international basis. 



Transmission Results 



The transmission results which have been obtained with the Levia- 

 than on her first trip of commercial service are summarized in Fig. 16. 

 It will be noted that practically continuous 24-hour communication 

 was maintained for distances within 1000 miles of the shore, correspond- 

 ing to two days out. The service at greater distances was more inter- 

 mittent. This was largely due to the fact that during this first trip the 

 effort was concentrated on covering reliably the more important nearer- 

 in distances, and the ship was not prepared to transmit on frequen- 

 cies above 8 megacycles. The service proved to be much in demand 



