ABSTRACTS OF TECHNICAL ARTICLES 685 



1. For a particular BaO + SrO filament, the conductivity C was 

 given by 



1.73 X lO^ 0.62 X 10< 



1.71 X lO^e T +5.55 X IQ-^e t 



2. The current is proportional to the voltage only so long as the 

 current is small; otherwise the products of electrolysis alter the 

 conductivity. 



3. Polarization currents are caused by the Ba and O which are pro- 

 duced by electrolysis. These currents decrease rapidly even at tem- 

 peratures near 500° K., thus showing that Ba and O diffuse at low tem- 

 peratures. 



Recent Developments in the Operation of Overseas Radio Telephone 

 Service} F. A. Cowan. This paper outlines the status of the present 

 overseas radio telephone services from the United States, discusses the 

 disturbing factors affecting each type of circuit, and outlines the reasons 

 why short waves have come to be considered the probable medium for 

 future extensions. The causes of lost circuit time to these services are 

 given in their order of magnitude as: adverse atmospheric conditions, 

 operating adjustments, radio interference, line and equipment troubles, 

 and unclassified causes. Adverse atmospheric conditions have been 

 partially overcome by the use of directive transmitting and receiving 

 antennas and automatic gain devices on the radio receivers. These 

 arrangements, however, do not eliminate the lost time caused by mag- 

 netic disturbances directly in the radio path or by the phenomena 

 known as selective fading. Magnetic disturbances usually affect 

 radio transmission over an appreciable period and a chart is included 

 which shows the average manner in which they affected the available 

 circuit time for the year 1930. The time required for operating adjust- 

 ments which include such items as line-up and talking tests, changing 

 wave-lengths, etc., will always be a factor but improvement will un- 

 doubtedly come with equipment development and experience. Line 

 and equipment troubles are almost insignificant by comparison with 

 the other causes of lost time and are made so by careful design and 

 maintenance and the provision of spare units. A chart is included 

 which shows for the month of August 1930 a comparison of lost circuit 

 time, by causes, between the European and South American radio 

 circuits. A chart is also included which shows the results of frequency 

 measurements made over the month of August 1930 on the 21420 kc. 

 transmitting frequency from the WLO transmitter at Lawrenceville, 

 New Jersey. It is of interest to note that at no time during the month 



' In abridged form, Elec. Engg., July, 1931. 



