.iHSTR.iCTS or nr.u. svsi r.M ti.ciimc.ii. ririMs 340 



drawn attention to the prol)lenis involvcti in obtaining hiKh ciiiality 

 in systems for the electrical transmission and reprodiirtion nf sound. 

 This pa|HT gives the general re(|uiremenls fur such systems, dis-» 

 cusses briefly the factors to be consiileretl in design and operation 

 and indic.ites to what extent the tlesirixl results can be obtained witli 

 the means now available. 



It was pointed out in this paper that broadcasting stations and 

 connecting lines can be made practically perfect but that most of 

 the loud s|)eaking apparatus now extensively used for reproduction, 

 causes tlistortion. At the time of reading this paper the authors 

 demonstrated a lalmralory model of a new loud speaker of unusual 

 design. This apparatus reproduces all frequencies from the lowest 

 to the highest of the audible range with approximately equal facility. 

 This results in reproduced music which the ear can scarcely dis- 

 tinguish from the original. 



Telephone Transformers.^ \V. I.. Casper. After outlining the 

 varied sets of conditions which ditTerent types of telephone trans- 

 formers must meet, this paper discusses the design and construction 

 of transformers to handle efficiently the range of frequencies ordinarily 

 present in speech. Two winding transformers only are dealt with, 

 and the three most common impedance combinations of the two cir- 

 cuits connected by the transformer are considered; namely, both 

 circuits comprised of resistances, one circuit a resistance, and the 

 other a positive reactance, and one circuit a resistance and the other 

 a negative reactance. 



The efficiency with which energ\- is transmitted is measured b\- 

 comparison with an ideal transformer, and the transformer is studied 

 by supposing it replaced by an equivalent T network. The varia- 

 tion of transformer losses with frefjuency is discussed and charac- 

 teristic curves are shown for transformers of ditTerent mutual im- 

 pedances. Characteristics are also given showing the operation 

 of the in-put transformer associated with the vacuum tube. 



The mechanical construction of the common battery repeating 

 coil, telephone induction coil, and of certain types of transformers 

 for vacuum tulje circuits, are shown. These transformers are all 

 constructed so as to give the desired accuracy of speech transmission 

 under their respective circuit conditions. 



Radio Telephone Signalinii — Lmc Frequency System.- C S. De.m- 

 AREST. M. L. .Almqcist and L. M. Cle.ment. The system described 



'Journal of the .American Institute of Electrical Kneineers, Vol. XLIII. p. 197, 

 1924. 

 » Journ. -A. I. E. E. Vol. 43. p. 210, 1024. 



