208 THE BELL SYSTEM TECHNICAL JOURNAL, JANUARY 1951 



portionate efifects and try to share with you the fascination and challenge 

 of this field. 



Chain Feed Carries Springs Through Forming Die. J. D. Thompson^ arid 

 G. W. Rada.2 Am. Mach., v. 94, pp. 86-87, Oct. 2, 1950. 



Punch-Press Tooling Works from Cams, Makes Cams. J. H. Tomlin.^ 

 Am. Mach., v. 94, pp. 106-108, Sept. 18, 1950. 



Abstract — Literally millions of cam-shape combinations are possible in 

 the telephone-exchange contact cams made for Bell Telephone; yet only 

 two punches and two dies do all the work . . . Two cams are cut at a time 

 from same-size master cams in a punch-press setup that allows a switch to 

 a new cam shape in a matter of seconds. 



Construction of Cold-Cathode Counting or Stepping Tubes.* M. A. Town- 

 send.^ Elec. Engg., v. 69, pp. 810-813, Sept. 1950. 



Abstr.\ct — Electronic digital counters are capable of performing at high 

 speeds many of the functions which are performed at low speeds by chains 

 of relays and mechanical stepping switches. Here is described a new principle 

 of tube construction by means of which the position of a glow discharge can 

 be made to step along a row of cold cathodes under the control of input 

 pulses. 



Ferromagnetic Domains.* H. J. Williams.' References. Elec. Engg., v. 69, 

 pp. 817-822, Sept., 1950. 



Abstract — Ferromagnetism is based on the property of domains. These 

 are tiny regions within a magnetic substance. They have this special char- 

 acteristic : most of the elementary atomic magnets contained in a particular 

 domain have their spins oriented in the same direction. Domain sizes and 

 shapes are the result of an attempt of the ferromagnetic system to reach a 

 state that minimizes the magnetostatic, magnetostrictive, domain-boundary, 

 and other energies. 



416A-Tubefor Microwave Relays. K. P. Dowell.^ FM, v. 10, pp. 20-22, 

 Aug., 1950. 



Abstract — For construction of its cross-country microwave relay chain, 

 the Bell System required a 4,000-mc. amplifier tube having a greater gain- 

 bandwidth product than any available at the time. The 41 6A planar triode, 

 shown in Fig. 1, was developed especially for this application. Because of 

 its exceptionally close interelectrode spacing, new techniques were necessary 

 for factory production of the tube. It is the purpose of this paper to show 

 some of the unique operations employed in its manufacture and assembly. 



On the Acoustics of Coupled Rooms.* C. M. Harris' and H. Feshbach. 

 Acoustical Sac. Am., JL, v. 22, pp. 572-578, Sept. 1950. 



* A reprint of this article may be obtained on request to the editor of the B.S.T.J. 



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