THE CARBON BUTTON. 



17 



Though all these processes tend to impair the delicacy of the button, 

 it is still far superior to a button made of any other substance. 



The first application made of the carbon button was in the tele- 

 phone. The arrangement of the apparatus is shown in Fig. 4. The 

 carbon button, E, is placed between two platinum plates, D and G, 

 which are in the circuit of a battery, as shown by the figure. Upon 

 the upper platinum, D, is placed an ivory plate, C. A piece of rubber 



a a Iron 



' vJndkiMlibir 

 clrciy 

 pPlalim 

 ZCtirbcn 

 (aPlatinaScmi 



<4 



j 



c_ 



J) 



Fig. 4. 



tubing, B, connects the ivory with the vibrating diaphragm, A A. All 

 this is inclosed in a hard-rubber case with suitable mouthpiece and 

 adjusting apparatus. The vibrations of the diaphragm communicated 

 through the rubber cause variations in the pressure upon the carbon, 

 and corresponding variations in the strength of the current which 

 traverses the wire. At the receiving station an instrument similar 

 to the one already described, invented by Gray, may be used. 



At first the diaphragm was made so delicate that it continued to 

 vibrate an appreciable time after the cause which set it in vibration 

 ceased to act, at least long enough to cause an interference in articu- 

 lation due to the mingling of successive vibrations. The object of the 

 piece of rubber was to dampen the vibrations of the diaphragm, or to 

 bring the diaphragm quickly to rest after it has been set in motion by 

 a sound. The rubber was found to be somewhat tardy in its action ; 

 at best the sound emitted was muffled. The rubber had the additional 

 disadvantage of becoming somewhat flattened with use, thus necessi- 

 tating readjustment. Experiments were then made to find something 

 which would bring the diaphragm to rest more quickly than the rub- 

 ber could, and for that purpose a thin spiral metallic spring was sub- 



VOL. XVII. 2 



