ABSTRACTS OF TECHNICAL ARTICLES 597 



Recent Improvements in Loading Apparatus for Telephone Cables} S. G. 

 Hale, A. L. Quinlax, and J. E. Ranges. Through the use of improved ma- 

 terials, manufacturing techniques, and designs, a series of exchange-area 

 loading coils has been provided which is equivalent electrically to the super- 

 seded types but requires one-third less copper and has considerably smaller 

 overall dimensions. Similarly, 3-coil toll cable loading units have been pro- 

 vided with a saving of one-half in both copper and core material, with a 

 small sacrilice in electrical behavior as compared with superseded types. 

 The reduced size of the new coils and units, together with improved assem- 

 bly arrangements, made possible a 65 per cent saving in the volume and 

 weight of the cases housing them. 



The Coaxial Transistor} Winston E. Kock and R. L. Wallace, Jr. 

 The success of the earlier types of transistors led to the exploration of other 

 forms of similar ampliliers, one of which is the coaxial transistor. A descrip- 

 tion of its construction, characteristics, and many advantages is contained 

 in this article. 



Paralleled-Resonator Filters? J. R. Pierce. This paper describes a class of 

 microwave filters in which input and output waveguides are connected by a 

 number of resonators, each coupled directly to both guides. Signal com- 

 ponents of different frequencies can pass from the input to the output 

 largely through different resonators. This type of filter is a realization of a 

 lattice network. An experimental filter is described. 



.4 Broad-Band Microwave Relay System between Ne-iV York atid Boston} 

 G. N. Thayer, A. A. Roetken, R. W. Friis, and A. L. Durkee. This 

 paper describes the principal features of a broad-band microwave relay 

 system which has recently been installed between New York and Boston. 

 The system operates at frequencies around 4,000 Mc and provides two 

 two-way channels, each accommodating a signal-frequency band extending 

 from 30 cps to 4.5 Mc. Noise and distortion characteristics are satisfactory 

 for the transmission of several hundred simultaneous telephone conversa- 

 tions or a standard black-and-white television program. 



Growing Crystals of Ethylene Diamine Tartrate} A. C. Walker and G. T. 

 KoHMAN. The need for a synthetic piezoelectric crystal to relieve the critical 

 quartz supply situation has resulted in the development by the Bell Tele- 

 phone Laboratories of a new organic salt crystal, ethylene diamine tartrate, 

 which is being used in place of quartz in telephone circuits. 



This crystal is grown from a supersaturated aqueous solution of its salt 

 by an entirely new method known as the constant temperature process. It 



^A.I.E.E. Transactions, v. 67, pt. 1, pp. 385-392, 1948. 



6 Electrical Engineering, v. 68, pp. 222-223, March 1949. 



^ Proc. I. R. E., V. 37, pp. 152-155, February 1949. 



^Proc. I. R. E.—Waves and Electrons Section, v. 37, pp. 183-188, February 1949. 



'A.I.E.E. Transactions, v. 67, pt. 1, pp. 565-570, 1948. 



