The working of this device is based on the miscellaneousations undergone by the electrical resistance of contact between the carbon granules with the miscellaneousation in pressure on them.
The granules are contained in a capsule between the irregular surface of a block of carbon and the elastic membrane, it too carbon, and protected by a fine metal net.
The miscellaneousable pressure on the membrane, when it is made to vibrate by the incident sound wave, produces strong, but gradual miscellaneousations in the contact resistance between the particles and thus of the overall resistance of the microphone. The consequent miscellaneousations in power cause the membrane in the receiver to vibrate and repeat the oscillations of the transmitter membrane, thus reproducing the sound that generated the vibrations.
The microphone with carbon granules, by producing strong miscellaneousations in the power supply, gave a first solution to problems of transmission over long distances.
When, due to distance, the resistance of the line was strong, a transformer was used and the microphone was connected to the primary with the accumulator in series and the transmission line to the secondary.