Figure E1

Alexander Graham Bell patented the first microphone in 1876. His microphone consisted of a wire which conducted electrical direct current (DC). Audio signals were generated and received by a moving armature transmitter and its receiver, and transmission was possible from both directions.

Bell's second transmitting device was a liquid transmitter. He first demonstrated the device at the Philadelphia Centennial Exposition of 1876. This microphone utilized a variable contact principle to provide a more effective method of electrical signal modulation than his previous microphone design.

Figure E2

Emile Berliner

In 1877, Emile Berliner patented a design based on Bell's liquid transmitter idea. Berliner's device used a steel ball placed against a stretched metal diaphragm. Figure E2 is a diagram of Berliner's microphone design.

Francis Blake

Building on Bell's initial moving armature design, Francis Blake patented a design that used a platinum bead impressed against a hard carbon disc as the variable resistance element. Blake's device fell short of the initial desired frequency range, but became the standard of Bell's telephone system for years because of its efficiency in modulating telephone signals.

Figure E3

After Francis Blake's invention using the platinum bead, Blake then developed a microphone transmitter that used loose carbon granule elements. Figure E3 is a diagram of the device from Blake's original patent. This early microphone design was the precursor to the most widely used microphone type from its invention to the present day; the carbon microphone.

Several examples of early carbon microphones contained in the Steele Vintage Microphone Collection are featured in the gallery below.

Figure E4

Military Microphones

Mr. Steele's collection contains at least one microphone used by the U.S. military during World War II. This later carbon microphone, pictured in Figure E4, is identical to those that were in use by the military for radio broadcasts during the 1940s. This particular model was often referred to as the "candlestick" microphone. Figure E5 is newspaper clipping featuring the Kellogg T32 "Candlestick" microphone being used by a U.S. soldier.