Reis microphone, of about 1861 - 1865
Johann Philipp Reis 1834 - 1874
Consider also the German 100 years anniversary of Reis’ birthday in 1934
"Durch meinem Physikunterricht an der Lehranstalt in Friedrichsdorf veranlaßt, griff ich im Jahre 1860 eine schon früher begonnene Arbeit über die Gehörwerkzeuge wieder auf und hatte bald die Freude, meine Mühen durch Erfolg belohnt zu sehen, indem es mir gelang, einen Apparat zu erfinden, durch welchen es möglich wird, die Funktion der Gehörwerkzeuge klar und anschaulich zu machen; mit welchem man aber auch Töne aller Art durch den galvanischen Strom in beliebiger Entfernung reproduzieren kann". Im Jahre 1861 hat er dann diesem Apparat den Namen "Telephon" gegeben. Er führt dazu aus: "Da die Länge des Leitungsdrahtes jedenfalls ebensoweit ausgedehnt werden darf wie bei direkter Telegraphie, so gebe ich meinem Instrument den Namen "Telephon".
Reis' microphone, showing the voice tube and its membrane section, photo taken by Keith Thrower; Sience Museum catalogue number: 1923-273 PT1
Side view of the Reis microphone (Photo taken by Keith Thrower)
The manner how Reis’ microphone worked, was based on the principle of the human ear. In 1861, Reis gave his microphone system the name: Telephon (is the German word for Telephone). Thus long before Graham Bell came up with his superior telephone system.
Basically, he used a membrane which represented the eardrum. He placed his membrane on top of a soundbox. The alternating air flow originating from the voice tube, could only leave the box via a circular opening in the top of the (cubical) wooden case. This membrane, which is slightly bigger than the circular sound outlet, responded to the air flow fluctuations (vibrations). In the centre of the membrane he placed a contact pin connected onto one side of a battery. A brass-strip resting on top of the centre-pin was mounted as to allow its free movements. The flow of the sound-waves touching the membrane, modulate (alternate) its contact resistance (centre-pin vs brass-strip). The modulated contact current is fed onto an inductor-coil at distance. The bobbin of this coil is placed on a longitudinal metal rod, which is carried between two wooden sound supports (pivots). In my opinion quite cleverly, Reis employed the magneto-striction phenomenon of a metal rod (alternating currents originating from the modulated contact-joint resistance)
Photograph of Reis' sound reproducing module. Photo taken by Keith Thrower, Science Museum catalogue number: 1923-273PT2. (PT2 indicates, that the apparatus consists of two artefacts, 1923 was the year in which these artefacts became subject of the Science Museum Collection)
We can clearly see (notice the dark colour of the centre section of this coil), that the inductor-coil necessitated a rather high current as to generated adequate magneto-striction. The magneto-striction movements* were transferred (picked-up) by the two wooden sound supports, which causes sonic vibrations of the sound-box structure. Reis’ basic idea was, that the sound reproducing module should act like a violin does. Special holes are provided as to allow sufficient sound transfer. The overall sound reproduction is, however, rather poor.
* In a recent article found in the German GFGF magazine "Funkgeschichte" (Nr.176, December 2007, p.179) I found the reference to this phenomenon. It was US citizen C.G. Page who in 1837 discovered: that an electromagnetic rod produced sound when it was connected onto alternating currents. Meant was, owing to alternating EMF
Reis tried to enhance the sound quality, though has failed to solve its fundamental shortcomings. What might have hampered Reis was, that he did not need the money to survive the struggles of live (may be, the time was not yet allowing better solutions), as he was then a teacher (it was more or less a dedicated hobby project). He, nevertheless, gave public demonstrations, even to respected institutions of his times. (regard for more details Reis' obituary, in German language)
Thomas Edison knew already from own experience, how difficult it is to make a bright idea actually work (1 % inspiration and 99 % transpiration).
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