ABSTRACTS OF TECHNICAL ARTICLES 817 



WicKLiNE* and J. E. Farley*. Elec. Eng., 71, pp. 252-257, Mar,, 

 1952. 



All the means of electrical communication are called into play when a city- 

 wide coverage of an event is to be televised. How telephone and television facil- 

 ities were utilized on the day that Chicago welcomed General MacArthur is 

 explained in this article. 



Echo Distortion in the FM Transmission of Freouency-Division Mul- 

 tiplex. W J. Albersheim^ and J, P. Schafer\ Proc. Inst. Radio Engrs., 

 40, pp. 316-328, March, 1952. 



The composite multiplex signals generated by frequency-division methods 

 long standard in telephone communication can be transmitted by the new trans- 

 continental broad-band FM radio relays. Signal intermodulation by echoes must 

 be minimized. Such intermodulation is investigated in this paper experimentally 

 and analj^tically. Two types of echoes are considered: (1) weak echoes with de- 

 lay's exceeding 0.1 microseconds, caused mainlj' by mismatched long lines; and 

 (2) powerful echoes with delays shorter than 0.01 microseconds, caused by multi- 

 path transmission, and leading to selective fading. By use of random noise sig- 

 nals, the distortion is evaluated as a function of various parameters of the echo, 

 the base-band, and the rf modulation. 



Motion of a Ferromagnetic Domain Wall in FczOa. J. K. Galt , Phys. 

 Rev., 85, pp. 664-669, Feb. 15, 1952. 



Experiments have been made on a sample of FesOi cut from a single crystal 

 in such a way that its ferromagnetic domain pattern includes an individual 

 domain wall whose motion can be studied. This sample has a permeability which 

 is high (about 5000) at low frequencies and drops off rapidly above 1000 cycles. 

 A hysteresis loop and data on wall velocity vs applied field were also taken. 

 The data are discussed in terms of recent developments in the theory of the 

 ferromagnetic domain wall. It appears that this theory explains our data satis- 

 factorily, and that in using it to explain our data we determine some of the 

 fundamental magnetic constants of Fe304. We are also able to gain some insight 

 into domain wall motion in ferrites generally in this way. 



The Drift Mobility of Electrons in Silicon. J. R. Haynes^ and W. C- 

 Westphal\ Phijs Rev., 85, p. 680, Feb. 15, 1952. 



Formulas for the Group Sequential Sampling of Attributes. H. L. 

 Jones*. Ann. Math. Statistics, 23, pp. 72-87, March, 1952. 



Soine Fundamental Properties of Transmission Systems. F. B. 

 Llewellyn^ Proc. Inst. Radio Engrs., 40, pp. 271-283, March, 

 1952. 



The problem of the minimum loss in relation to the singing point is investi- 

 gated for generalized transmission systems that must be stable for any combina- 



' Bell Telephone Laboratories. 



* Illinois Bell Telephone Company. 



