Electrical Communication - The Single-Button Carbon-Granule Telephone Transmitter

Electrical Communication is a free textbook on the basics of communication technology. See the editorial for more information....

Home Electroacoustic Devices The Single-Button Carbon-Granule Telephone Transmitter


Search the VIAS Library \| Index
The Single-Button Carbon-Granule Telephone Transmitter Many types of telephone transmitters have been developed,⁷ one being shown in Fig. 1. This consists of a circular brass cup partly filled with carefully selected carbon granules. The inside edge of the cup is insulated with a paper ring. In the bottom is placed a highly polished, circular, carbon electrode which is fastened to the cup and serves for a contact with the carbon granules. The opening or top of the cup is partly filled with another circular electrode fastened to a metal plunger which in turn is attached to the diaphragm. The path of the current is through the insulated terminal fastened to the steel bridge, through the damping spring, through the front movable disk, through the carbon granules, and thence out through the fixed carbon disk to a second insulated binding post on the steel bridge. The damping spring is provided to reduce resonance effects in the mechanical portions. The resistance of the transmitter at a current of about 0.1 ampere is about 50 ohms when it is not excited by sound waves.
Home Electroacoustic Devices The Single-Button Carbon-Granule Telephone Transmitter

Last Update: 2011-05-18