388 AUSTIN: CRYSTAL CONTACT DISTURBANCE PREVENTER 



galvanometer during a period of 10 seconds being taken as the 

 atmospheric reading. 



The disturbance preventer is more effective in the case of 

 strong interfering signals than against atmospheric disturbances, 

 as it is quite possible to read signals of twenty times audibility 

 thru disturbing signals of many hundred times audibility on 

 the same wave length. The best results are obtained with loose 

 coupling and with a considerable amount of inductance in the 

 antenna, with a series condenser if necessary, and the disturb- 

 ance preventer contact shunted across only that part of the in- 

 ductance which acts as the primary of the receiving transformer. 



TABLE II 



An increase of the effect may be obtained by throwing the 

 circuit out of tune to the loud signals by placing disturbance 

 preventers across the capacity or across other portions of the 

 inductance, and also in the secondary circuit. But in gen- 

 eral, except under extraordinary circumstances, these introduce 

 complications in handling which are out of proportion to their 

 benefit. 



Fairly good results have been obtained also with a contact of 

 carborundum with other crystals. These combinations however, 

 while more stable under extremely powerful disturbances, in 

 general do not fall low enough in resistance , to give as satisfac- 

 tory results as the silicon-arsenic. I wish to express my indebt- 

 edness to my assistant. Chief Electrician Mineratti in the latter 

 portions of this work. 



