Category:Microphones in the 1870s

Media in category "Microphones in the 1870s"

The following 4 files are in this category, out of 4 total.

• 
  Bell liquid telephone transmitter 1876.png 843 × 1,290; 302 KB
  
• 
  Bells first wall telephone 1877.jpg 406 × 710; 39 KB
  
• 
  Condensateur d'Aepius.jpg 247 × 238; 37 KB
  
• 
  Gray-telephone-notebook.gif 605 × 362; 64 KB