(Above and below) A couple of diagrams illustrating David Edward Hughes' carbon microphone

In 1886, Thomas Edison refined the carbon microphone into his carbon-button transmitter and it was employed at the first ever radio broadcast, a performance at the New York Metropolitan Opera House in 1910.

Did you know?
>> David Edward Hughes designed the first printing telegraph system in 1855. In less than two years a number of small telegraph companies, including Western Union in early stages of development, united to form one large corporation – Western Union Telegraph Co. to carry on the business of telegraphy on the Hughes system. In Europe, the Hughes Telegraph System became an international standard.

>> Hughes also stumbled upon what would later be known as the first working radio communication system in 1879, when he discovered sparks would generate a radio signal that could be detected by listening to a telephone receiver using his new microphone design as a detector. Using trail-and-error experiments, he developed his spark-gap transmitter and receiver into a working communication system. Eventually he could demonstrate the ability to send and receive Morse code signals out to a range limited to 500 yards (460 m). Hughes demonstrated his invention in the presence of prominent attendees, which included, Sir William Crookes, Sir William Henry Preece, William Grylls Adams, and James Dewar.

>> David Edward Hughes invented the induction balance, which was later used in metal detectors.