INDUCTIVE LOADING FOR TELEPHONE FACILITIES 203 



tributed to the more favorable crosstalk-performance, along with other 

 process improvements. (Refer to Fig. 10, page 186.) 



The improved crosstalk-performance above discussed, which was achieved 

 in the development of the PB-type permalloy-core phantom loading units, 

 previously described, was maintained in the commercial production of the 

 smaller-size M-type molybdenum-permalloy core loading units which super- 

 seded the PB-type loading units, and in the present standard MF-type 

 loading units. (Refer to Fig. 12, page 192.) 



It seems improbable that additional improvements in loading unit cross- 

 talk-performance will be needed in the future, in view of the trend during 

 recent years of restricting voice-frequency phantom-group loading to short- 

 haul facilities. 



A more comprehensive account of the successful struggle to control cable 

 crosstalk in loaded toll cables is given in a 1935 Bell Telephone Quarterly 

 article^^ by Mr. M. A. Weaver. An A.I.E.E. paper,^ previously referred 

 to, includes considerable additional information on the crosstalk-reduction 

 work on the loading coils, up to 1926. 



Bibliography 



1. George A. Campbell, "Collected Papers," A.T.&T.Co., New York, 1937. Introduc- 



tion by E H. Colpitts; see also "Three Early Memoranda on Loading," page 10. 



2. M. I. Pupin, "Wave Transmission over Non-Uniform Cables and Long Distance Air 



Lines," Trans. A.I.E.E., Vol. XVII, 1900, p. 445. Also, Pupin U. 5. Patent Nos. 

 652,230 and 652,231, June 19, 1900. 



3. George A. Campbell, "On Loaded Lines in Telephonic Tvdinsmission"— Philosophical 



Magazine, March 1903 (reprinted in Reference No. 1, based entirely on 1899 the- 

 oretical studies and experiments). 



4. Vaschy, La Lumiere Electrique, Jan. 12, 1889. 



5. O. Heaviside, "Electromagnetic Theory," Vol. 1, 1893, p. 441. 



6. B. Gherardi, "Commercial Loading of Telephone Circuits in the Bell System," 



Trans. A.I.E.E., Vol. XXX, 1911, p. 1743. 



7. Roger B. Hill and Thomas Shaw, "Hammond V. Hayes: 1860-1947," Bell Telephone 



Magazine, Vol. XXVI, Autumn 1947, pp. 150-173. 



8. Thomas Shaw and William Fondiller, "Development and Application of Loadmg for 



Telephone Circuits," Trans. A.I.E.E., Vol. XLV, Published in Bell System Tech- 

 nical Journal, Vol. V, April 1926, pp. 221-281. 



9. Thomas Shaw, "The Conquest of Distance by Wire Telephony," Bell System Tech- 



nical Journal, Vol. XXIII, October 1944. 



10. W. Fondiller and W. H. Martin, "Hysteresis Effects with Varying Superposed Mag- 



netizing Forces," Trans. AJ.E.E., Vol. XL, 1921. 



11. B. Gherardi and F. B. Jewett, "Telephone Repeaters," Trans. AJ.E.E., Vol. XXX- 



VIII, Nov. 1919. , ^. , . 



12. R. S. Hoyt, "Impedance of Loaded Lines and Design of Simulatmg and Compensat- 



ing Networks," B.S.T.J. April 1923. . ^ ^ ^ 



13. Buckner Speed and G. W. Elmen, "Magnetic Properties of Compressed Powdered 



Iron," Trans. AJ.E.E., Vol. XL, 1921, p. 596. . . r- i. 



14. A. B. Clark, "Telephone Transmission Over Long Cable Circuits, Trans. AJ.E.E., 



Jan. 1923; B.S.T.J., Jan. 1923; Electrical Communication, Feb. 1923. 



15. H. S. Osborne, "Telephone Transmission Over Long Distances," Trans. AJ.E.E., 



Oct. 1923; Electrical Communication, Oct. 1923. ^ , , „. . „ 



16. A. B. Clark and R. C. Mathes, "Echo Suppressors for Long Telephone Circuits, 



rm«5..4./.E.E.,Junel925,p.618. . » r c t r v.i i 



17. G. A. Campbell, "Physical Theory of the Electric Wave Filter, B.S.T.J. Vol. 1, 



Nov. 1922. 



