Abstracts of Technical Articles from Bell System Sources. 



A Review of Radio Communication in the Mobile Services.^ Clifford 

 N. Anderson. Developments in radio communication in the mobile 

 services during 1935 have been largely in the nature of gradual im- 

 provement of existing equipments and services. 



In the marine field, the safety-of-life aspect is assuming increased 

 importance. Rearrangements have been made of the frequencies 

 and the schedules of radio beacons to avoid interference thereby mak- 

 ing the system more effective. The improvement of radio compasses, 

 regulations regarding motor lifeboat equipment and public address 

 alarm systems, requirements for radio auto alarms and experimentation 

 with collision prevention equipment are other items on which progress 

 has been made the past year. The development in marine radio- 

 telegraphy has been chiefly along the lines of greater application of the 

 high frequencies. Directional antennas at the shore receiving stations 

 have mitigated the effects of interference. Facsimile transmission of 

 weather maps and press is being tried out. Improvements have been 

 made in radio telephone equipments of various powers and frequency 

 ranges for various types of marine service. A system utilizing ultra- 

 high frequencies was put into operation at Philadelphia during the year. 

 Three commercial stations are in operation in the two-megacycle range, 

 the one at Seattle having been opened this year. 



Radio is an important factor in the operation of modern air lines. 

 Special mention should be made of the important role played by radio 

 in the newly established transpacific service by the Pan American 

 Airways. Improvements have been made during the year in airway 

 beacons and radio compasses; airport traffic control and blind landing 

 systems are being tried out. In addition to the beacon and communi- 

 cation receiver, a small five-watt transmitter has been made available 

 for the use of itinerant flyers in communicating with airports. 



The use of radiotelephony with police cars is the most important 

 application of radio with automobiles. There are two general types 

 of this service, both of which have expanded materially during the past 

 year. One consists of a one-way service from police headquarters to 

 the cars and is usually conducted on a frequency in the range of 1500 

 to 2500 kilocycles. The other is a two-way service generally operating 

 in the ultra-high-frequency range of 30,000 to 40,000 kilocycles. 



' Proc. I. R. E., March, 1936. 



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