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BELL SYSTEM TECHNICAL JOURNAL 



large planes which carry a radio operator and on another channel by 

 radio telephone with the smaller planes. 



Two-way communication has the great and obvious merit of per- 

 mitting a pilot to discuss the weather outlook with an airport meteor- 

 ologist, to consider alternative landing places in view of such factors 

 as his remaining fuel supply or the direction of wind, and to decide 

 if necessary on a change in landing place and to be assured of arrange- 

 ments there for the care of his passengers and mail. It seems reason- 



FiG. 1. The Whippany Radio Laboratory. 



able, therefore, to predict that operators of air transport fleets will 

 require two-way communication with their planes in flight, although 

 taxi services and private owners without ground organization along 

 the airway may, in general, be content with a public one-way broad- 

 casting service. 



Whether one-way or two-way communication is desired for plane- 

 to-ground use it appears that radio telephony as distinguished from 

 telegraphy will be essential. Radio telegraphy requires on board the 

 plane the individual attention of a special radio operator for sending 

 and receiving. Although very large multi-engined passenger planes 

 will certainly carry a relief pilot in flight, it is doubtful whether good 



