EXTENSION OF THE TELEPHONE SYSTEM TO SHIPS 175 



ordinary radio-telegraph circuit on the other. In regular long distance 

 telephone circuits we have a fixed type of system which is maintained 

 continually in good talking condition and the operators turn the 

 terminals over to the use of the subscribers themselves. On the 

 other hand in a radio telegraph circuit operating between land and 

 vessel the circuit is kept entirely in the hands of skilled operators 

 who have access to the apparatus and who handle the traffic directly 

 between themselves. In no case before have we had the requirement 

 of taking a radio link of varying length, building it up as occasion 



SETTING UP A TELEPHONE CONNECTION 



SUBSCRIBER CENTRAL 



LAND STATION SHIP STATION 



I-600 M. Telegraph Calling 



2- Radio-Phone Trunk Established 



EB — (H 



^-T>- £ 



°^-0 



3- Calling Information Passed 

 4- Land OperatorSets upWireOr cuit 



— {<B- 



-[±D— « 



-D 



5-Land Operator Connects Thru and 

 Ship Operator Talks with Subsc riber 



■m- 



-ED— « 



^^ 



6- Call Completed ShipanaLand 

 Subscribers Talk 





Fig. 21 



requires with wire circuits and, upon call, putting the combined 

 system at the disposal of people experienced only in the use Of the 

 regular telephone. The technical difficulties of the combination 

 system, together with the necessity of coming as close as possible to 

 meeting telephone standards in the quality of talk given, greatly 

 reduce the length of the radio link which can be used for a service 

 as compared with those distances which can be spanned for short 

 periods of time under the most favorable conditions. The effect 

 which the requirement of reliability has in reducing the range of 

 transmission will be appreciated from the discussion of field strength 

 measurements. 



