The Stone Coherer has two small steel plugs between which are placed loosely packed carbon granules.

In the carbon chamber were carbon granules loosely pressed against a carbon button in front.

The vapors are absorbed by the carbon granules.

When the engine is started, the canister is purged by opening a switch and drawing fresh air over the carbon granules.

The diaphragm's vibrations rapidly compress and uncompressed carbon granules, changing their resistance.

He used a spark coil for creating waves and a mass of carbon granules for detecting them.

Later, carbon granules were used between carbon buttons.

The Hunnings transmitter provided multiple contacts between the diaphragm and a chamber containing loosely packed carbon granules.

A microphone - In the past, telephone microphones have been as simple as carbon granules compressed between two thin metal plates.

In a modern phone there is an electronic microphone, amplifier and circuit to replace the carbon granules and loading coil.