510 THE BELL SYSTEM TECHNICAL JOURNAL, MARCH 1953 



This paper presents the results of a theoretical and experimental study of a 

 waveguide matching technique which allows a directional coupler to be located 

 any distance away from the discontinuity causing the original mismatch and a 

 broad-band match to still be obtained. 



Design curves are included which give the required coupling coefficient of the 

 directional coupler and the power loss for a given initial mismatch and desired 

 vswr reduction. Experimental confirmation of the theory is also presented. 



New General-Purpose Relay for Telephone Switching Systems. A. C. 

 KellerI. Elec. Engg., 71, pp. 1007-1012, Nov., 1952. Monograph 2034). 



This new general-purpose electromagnetic relay, called the AF type is a wire 

 spring relay. With variations providing slow release or marginal characteristics, 

 it is known as the AG and AJ relay, respectively. It provides improved perform- 

 ance at lower cost. 



Spherical Model of a Ferromagnet. H. W. Lewis^ and G. H. Wannier^ 

 Letter to the Editor. Phys. Rev., 88, pp. 682-683, Nov. 1, 1952. 



In order to interpret the properties of the tetragonal crystal ND4D2PO4 

 (deuterated ADP) a thermo-dynamic treatment has been developed which re- 

 lates the observed crystal structure change and the dielectric constant change 

 at the transition temperature to the appearance of spontaneous polarization. 

 For an antiferroelectric crystal, the average spontaneous polarization is zero, 

 being oppositely directed for adjacent layers, but the square of the spontaneous 

 polarization is large. This results in quadratic strain components which cause a 

 change in the crystal structure below the transition temperature. It is shown 

 that the change observed is consistent with an antiferroelectric arrangement 

 with one of the a axes being the antiferroelectric axis. The dielectric constants 

 in all three directions suffer a large drop below the transition temperature. 



Piezoelectric^ Dielectric, and Elastic Properties of NDiD^POi {Deuter- 

 ated ADP). W. P. Masoni and B. T. Matthias^. Phys. Rev.y 88, pp. 

 477^79, Nov. 1, 1952. (Monograph 2036). 



Transistors in Our Civilian Economy. J. W. McRae^ I.R.E.j Proc, 40, 

 pp. 1285-1286, Nov., 1952. 



/. R. E. Editor's Note: At relatively long intervals there appear on the tech- 

 nical and industrial horizons devices of such broad scope and major significance 

 that they profoundly affect the fields of their use. One of these epochal develop- 

 ments is the transistor, which bids fair to take its place beside the electron tube 

 as one of the foundation stones of future communications and electronics. 



It is accordingly timely and suitable that certain of the probable future in- 

 dustrial uses and effects of the transistor should be here analyzed in a guest edi- 

 torial by an engineer especially qualified for this task, and who is a Fellow and 

 Director of the Institute, and a Vice President of Bell Telephone Laboratories. 



* Bell Telephone Laboratories. 



