The first dynamic/moving coil microphone was patented in 1874 by Ernst Siemens, but never caught on, as carbon granule mics were adequate for telephone applications and easier to produce. As telephone and radio technology improved, Bell Labs’ Edward Christopher ("E.C.") Wente created the first condenser mic in 1916, offering improved performance, but in a large, fragile package that required a separate power supply.
Wente worked with fellow Bell engineer Albert Thuras to develop the first commercial dynamic microphone, which on its release in 1931, was called the Western Electric 618A Electrodynamic Transmitter. With its thin duralumin diaphragm and new cobalt-steel alloy magnet, the omnidirectional 618A offered high output and a respectable 10kHz bandwidth. With its ease of operation and tough, compact housing, it remained in use for years among P.A., film and broadcast users. It was also the mic of choice for Franklin Delano Roosevelt's famous Fireside Chat radio addresses.
Click here to download a PDF file of the original Western Electric 618A microphone manual.