Transmitter: The AC100 telephone had a carbon granule type transmitter with provision for rotating it to prevent compacting of the granules. |
The carbon granule microphone was standard for telephones for over 100 years until recent times. It developed from the work of Prof. David Hughes who realised that any system of loose contact could be used as a microphone, which then converts sound waves into an undulating electrical current for transmission to a distant receiver. Carbon granule microphones have been superseded by electret microphones which are capable of higher quality speech and with less noise. |