ABSTRACTS OF TECHxNICAL ARTICLES 209 



Computation of Control Limits for p-Charts Whe7i the Samples Vary in 

 Size. 11. L. JoNES^ Ind. Quality Control, 8, pp. 26-27, Sept., 1951. 



The Design of Switching Circuits. W. Keister^, A. E. Ritchie^, and 

 S. H. Washburn^. N. Y., Van Nostrand, 1951. 556 pp. (Bell Telephone 

 Laboratories Series) . 



This is the first published textbook in its field. It presents, first, the funda- 

 mental design principles of switching circuits composed of discrete-valued 

 switching elements. Most of the discussion concerns two-valued elements, with 

 greatest emphasis placed on electromagnetic relays. Chapters cover basic circuit 

 paths, the logical interpretation of retiuirements, and the techniques of con- 

 structing networks to fulfill these requirements. The symbolic methods of 

 Boolean algebra and its application to the design of combinational and sequen- 

 tial circuits is covered. Later chapters cover various unifunctional circuits such 

 as selecting, connecting, translating, counting, and lockout. Final chapters dis- 

 cuss methods of sjoithesising unifunctional cncuit building blocks into larger 

 circuits and systems. 



Measurement of the Elastic Constants of Silicon Single Crystals and 

 Their Thermal Coefficients. H.J. McSkimin^ W. L. Bond^ E. Buehler\ 

 and G. K. Teal^. Letter to the Editor. Phys. Rev., 83, p. 1080, Sept. 1, 

 1951. 



Interest in the properties of sihcon single crystals arising from their use as 

 semiconductors has led us to make measurements of the elastic constants of 

 two single crystals. Measurements of velocities of propagation for both shear 

 and longitudinal waves were made in the crystals as described in a recent paper 

 by McSkimin. Frequencies in the range 8-12 mc/sec were used. 



The three independent elastic constants were evaluated, a density of 2.331 

 (measured by pycrometer) being used. Data and formulas used are summarized 

 in Table 1. Two crystals were measured — as indicated — with data obtained 

 from the larger one being used to determine the elastic constants. Check meas- 

 urements were made for the smaller crystal; and despite the less accurate "pulse 

 overlap" technique used for two of the measurements, velocity agreement to 

 within 0.15 per cent was obtained. 



Both crj'stals were of a high degree of crystalline perfection as shown by 

 etching and X-ray tests. 



Domain Wall Relaxation in Nickel. W. P. Mason^ Letter to the 

 Editor. Phys. Rev., 83, pp. 683-684, Aug. 1, 1951. 



Phase Transitions in Ferroelectrics. B. Matthias^ National Research 

 Council, Comm. on Solids. Phase Transformations in Solids. Ed. by 

 R. Smoluchowski, J. E. Mayer, W. A. Weyl. N. Y., Wiley, 1951. 660 pp. 



iBell Tel. Labs. 

 5 111. Bell Tel. Co 



