768 THE BELL SYSTEM TECHNICAL JOURNAL, MAY 1957 



of ])reakdo\vu voltage versus the i)roclu('t of gas pressure and anode 

 distance. 



A tube is described which uses these principles to achieve a high gain 

 over a useful operating life of 4,000 hours, and which has a negative re- 

 sistance to audio fretiuency signals superimposed on the dc operating 

 current. Fast switching is obtained by an auxiliary photoelectric cathode 

 formed by making an electrical connection to a barium getter flash. 

 Satisfactory tube operationg has been obtained for continuous operation 

 for times which are ecjuivalent to 20 to 40 years of intermittent operation 

 in switching systems. 



ACKNOWLEDGEMENT 



The author is indebted to many members of the gas tube and switching 

 systems development groups at Bell Telephone Laboratories. Among 

 these special mention should be made of A. D. White who originated the 

 cavity hollow cathode and V. L. Holdaway, B. T. McClure, A. M. Wit- 

 tenberg and C. Depew who made important contributions to the success- 

 ful development of the tubes. 



BIBLIOGRAPHY 



1. M. J. Druvvestevn and F. M. Penning, Rev. Mod. Phys., 12, p. 97-102, 1940. 



2. Ibid., page 105. 



3. R. N. Varney, Phys. Rev. 93, p. 1156, 1954. 

 4 RcfBrcncG 1 p. 139. 



5. M. A. Town'send, W. A. Depp, B.S.T.J., 32, pp. 1371-91, 1953. 



6. Reference 1, p. 116. 



7. F. G. Hevmann, Proc. Phys. Soc, 63, Sec. B, 1950. 



8. H. L. Von Gugelberg, Helvetica Physica Acta, 20, pp. 307-340, 1947. 



