Figure 70. — Reproduction of Berliner's toy 

 drum microphone. The contact was a needle 

 that pierced a drum membrane against which 

 a metal ball rested. {USNM 3og277; Smith- 

 sonian photo ^^Gy.) 



Figure 71. — Drawing from one of Edison's 

 basic microphone patents, showing the use of 

 a semiconductor as one of the microphone 

 contacts. From U.S. patent 474230 (May 3, 

 1892). 



Figure 72. — Patent Office model of one of Edison's basic 

 microphone patents, showing the use of multiple contacts. 

 (USNM 2^2622; Smithsonian photo ^6yyy-A.) 



326 



BULLETIN 228: CONTRIBUTIONS FROM THE MUSEUM OF HISTORY AND TECHNOLOGY 



