Abstracts of Technical Articles by Bell System Authors 



Electronics in Telephony} Frank A. Cowan. The historical develop- 

 ment of the use of electronic devices by the telephone system is reviewed, 

 showing how long distance telephony has grown with the increased use of, 

 and improvements in, electronics. The number of telephone repeaters has 

 grown from 16 in 1908 to 123,000 in 1942 and carrier circuit mileage has 

 grown from 2,000 in 1920 to 2,300,000 in 1942, while copper usage per circuit 

 mile has decreased from 400 pounds in 1910 to less than 70 in 1942. 



A transcontinental telephone connection has grown from an open-wire 

 circuit with a total loss, less repeaters, of less than 75 db (1915) to a present 

 day cable circuit operating at carrier frequencies, which may have a total 

 loss of over 10,000 db. The problem of matching enormous amplifications 

 to compensate for huge losses with a precision of one or two db was a 

 difficult one, which was solved by electronic techniques. The amplifica- 

 tion necessary to compensate for the high losses on the cable layout may 

 entail some 200 repeaters utilizing a total of more than 600 vacuum tubes 

 in tandem. The automatic regulation and control of the amplification is 

 accomplished by electronic devices, giving to the present day circuits a 

 stability unequalled in the days before the vacuum tube. 



There is available, except for the War, radiotelephone service to 83 

 foreign countries and overseas areas, and ocean liners at sea, and to boats 

 in coastal and inland waters. 



Such widespread dependence on vacuum tubes has stimulated research 

 and design to achieve long life and a high degree of uniformity, stability 

 and reliability. Among interesting future possibilities are transoceanic 

 cables, the use of higher frequencies providing broader bands and larger 

 numbers of circuits over a given path, and further application of remote and 

 unattended stations. 



Deionization Considerations in a Harmonic Generator Employing a Gas- 

 Tube Switch} William G. Shepherd. A description is given of an 

 experimental investigation of the properties of a thyratron operating as a 

 high-frequency switch in a circuit which permitted the generation of a 

 wide band of harmonics. The experiments indicate that there is an operat- 

 ing frequency below which no difficulties in deionization occur and above 



1 Electronics, March 1943. 



2 Proc. I.R.E., February 1943. 



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