Microphone
German inventor Johann Philipp Reis designed an early sound transmitter that used a metallic strip attached to a vibrating membrane that would produce intermittent current. Better results were achieved with the "liquid transmitter" design in Scottish-American Alexander Graham Bell's telephone of 1876 – the diaphragm was attached to a conductive rod in an acid solution. These systems, however, gave a very poor sound quality.
The first microphone that enabled proper voice telephony was the (loose-contact) carbon microphone. This was independently developed by David Edward Hughes in England and Emile Berliner and Thomas Edison in the US. Although Edison was awarded the first patent (after a long legal dispute) in mid-1877, Hughes had demonstrated his working device in front of many witnesses some years earlier, and most historians credit him with its invention. The carbon microphone is the direct prototype of today's microphones and was critical in the development of telephony, broadcasting and the recording industries. Thomas Edison refined the carbon microphone into his carbon-button transmitter of 1886. This microphone was employed at the first ever radio broadcast, a performance at the New York Metropolitan Opera House in 1910.
In 1916, E.C. Wente of Western Electric developed the next breakthrough with the first condenser microphone. In 1923, the first practical moving coil microphone was built. The Marconi-Sykes magnetophone, developed by Captain H. J. Round, became the standard for BBC studios in London. This was improved in 1930 by Alan Blumlein and Herbert Holman who released the HB1A and was the best standard of the day.
Dictation machine
Alexander Graham Bell and his two associates took Edison's tinfoil phonograph and modified it considerably to make it reproduce sound from wax instead of tinfoil. They began their work at Bell's Volta Laboratory in Washington, D.C., in 1879, and continued until they were granted basic patents in 1886 for recording in wax.
Thomas A. Edison had invented the phonograph in 1877, but the fame bestowed on him for this invention — sometimes called his most original — was not due to its efficiency. Recording with his tinfoil phonograph was too difficult to be practical, as the tinfoil tore easily, and even when the stylus was properly adjusted, its reproduction of sound was distorted and squeaky, and good for only a few playbacks. Although Edison had hit upon the secret of sound recording, immediately after his discovery he did not improve it, allegedly because of an agreement to spend the next five years developing the New York City electric light and power system.