construct the circuit from resistances^, condensers and induc- 

 tances which might be found in the stockroom. By making 

 electrical measurements, on such a circuit 9 one could quickly 

 make design adjustments simply by turning knobs. Thus the 

 researchers had a computing machine of great flexibility and 

 convenience „ This device „ which was called the "LCR simu- 

 lator , " proved extremely useful as a design aid. 



Much work was done on cemented joints s on types of cement, 

 and on the baking and conditioning procedure „ Dr, Fred Uber 

 noticed that ADP crystals would tolerate the temperatures re- 

 quired for the Chrysler cycle-weld process „ He was thus able 

 to bond the crystals to rubber so that either the rubber or 

 the crystals ruptured before the bond failedc This technique 

 permitted the attachment of crystals directly to the rubber 

 sound window and eliminated the need for the castor oil Such 

 transducers obeyed theoretical predictions much better than 

 those using the castor oil Q Methods were found for strengthen- 

 ing the rubber windows so that such cycle-welded units promised 

 to be as strong as those made otherwise „ 



In addition to NDRC, other agencies, especially those re- 

 sponsible for the continued availability of crystals,, contrib- 

 uted indispensably to the furtherance of transducer engineering. 

 The Brush Development Company before the war had designed and 

 built a number of plants for growing Rochelle salt crystals 

 and had set aside a large stock pile of crystal bars. Thanks 

 in large part to the attitude of Mr, A* L» Williams and Mr, 

 Wo Ro Burwell of that company, the country had a reserve of 

 crystals needed for the heavily increased demands occasioned 

 by war, It was their continued support of fundamental re- 

 search in crystal physics and physical chemistry which led to 

 the introduction of ADP by Dr. Ho Jaffe and his associates „ 

 By the end of the war, the plants of the Brush Development 

 Company and the Bell Telephone Laboratories were turning out 

 a supply of ADP crystals sufficient to meet military require- 

 ments o A pilot plant for the further study and control of 

 ADP was constructed and put into operation by the Naval Re- 

 search Laboratory,, 



Under a direct contract with the Navy, the Bell Telephone 

 Laboratories also engaged in the development of many excel- 

 lent transducers and supplemented this work with studies of 

 fundamental nature „ Under W„ Ho Martin, a group consisting 

 of Ao Co Kellar, W, To Mason, and their associates^ did most 

 valuable work on crystals ? cements, electrodes, oils s rubbers 

 and nearly every other phase of transducer engineeringo 



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