Hughes' phone
Hughes' telephone is an electro-acoustic telephone developed by David Edward Hughes .
functionality
The telephones from Bell , Siemens , Gower and Ader can be used both as transmitters and receivers, but the magnetoelectric currents generated in them are weak and not suitable for overcoming greater line resistances; For this reason, special feeding devices operated with galvanic induction currents, which transmit speech sounds even over great distances, are often used, so-called microphones .
These are based on the fact that loose contact points in a circuit , when exposed to changing pressure, cause changes in the line resistance and thus also the current strength . They consist of one or more pieces of coal that are in contact with one another or with a metallic membrane.
The sound waves that hit the points of contact cause vibrations in an electrical current conducted through the contact, the curves of which correspond exactly to the sound vibrations. These electrical vibrations are converted back into sound vibrations in a telephone serving as a receiving device and are heard as a precise reproduction of what has been said into the microphone.
As the inventor of the microphone is Hughes to look at the apparatus two Resonanzbrettchen AB under a right angle are fixed to each other; on one of these are the pieces of coal CC and the carbon rod d, which is movably embedded in depressions of the same .
The coal pieces are connected to the circuit of a battery . If you speak against the board B , the resistances at the contact points change and electrical vibrations arise, which propagate through the line and reproduce the spoken sounds in a switched-on telephone. Usually the primary coil of an induction coil is connected to the circuit of the battery and the secondary coil, made of thinner wire, is connected to the line.
At about the same time as Hughes, Edison constructed his co-based carbon phone . The number of microphones specified by later inventors is very large. In the German Reich Telegraph Administration, however, only microphones from Blake , Berliner and Ader were used in limited numbers.
More telephones and microphones
- Bellscher telephone
- Siemens telephone
- Gowerscher telephone
- Blake's microphone
- Berlin microphone
- Microphone from vein
See also
Elisha Gray - co-inventor of the telephone
literature
- Grawinkel: Textbook of Telephone and Microphone (2nd edition). Berlin 1884
- Wietlisbach: Telephony technology . Vienna 1886
