AUSTIN: CRYSTAL CONTACT DISTURBANCE PREVENTER 387 



some in radiotelegraphic receiving, and in the spring of 1909 very 

 encouraging results were obtained from a tellurium-aluminum 

 contact placed around the primary of the receiving transformer. 



It was found however, that in actual service, while occasionally 

 remarkable results were obtained in cutting out disturbances, 

 the tellurium-aluminum contact was too unstable to be depended 

 upon. Silicon in contact with metals was found to be less 

 sensitive than the tellurium contact and also too unstable for 

 practical use. Iron pyrites, zinkite, galena, and many other 

 crystals have been tried at various times and unsuccessful ex- 

 periments were also made with the Lodge-Muirhead mercury 



TABLE I 



coherer, several other types of coherers, with vacuum valves 

 and the electrolytic detector. It has recently been found that 

 silicon in contact with certain crystals, especially with metallic 

 arsenic, of which the dark colored impure variety is the best, 

 forms a practical device for leading strong disturbances to earth 

 without interfering with the reception of the regular signals. 



Table I shows the detector galvanometer deflections with the 

 disturbance preventing circuit in and out, the antenna being 

 excited by a tuned buzzer circuit with different degrees of close- 

 ness of coupling. , 



Table II shows the relation between tuned buzzer circuit 

 signals and natural atmospherics, the maximum throw of the 



