[The following “Prospectus” of instructions was drawn up by Reis to accompany the Telephones which were sold by Herr Wilh. Albert of Frankfort. The author of this book is in possession of original copies, of which a number are extant. The “Prospectus” was also reprinted in its entirety at page 241 of Professor Pisko’s book ‘Die neueren Apparate der Akustik,’ published at Vienna in 1865.]
TELEPHON.
Each apparatus consists, as is seen from the above illustration, of two parts: the Telephone proper, A, and the Reproduction apparatus [Receiver], C. These two parts are placed at such a distance from each other, that singing, or the tones of a musical instrument, can be heard from one station to the other in no way except through the apparatus itself.
Both parts are connected with each other, and with the battery, B, like ordinary telegraphs. The battery must be capable of effecting the attraction of the armature of the electromagnet placed at the side of station A (3-4 six-inch Bunsen’s elements suffice for several hundred feet distance).
The galvanic current goes then from B to the screw, d, thence through the copper strip to the little platinum plate at the middle of the membrane, then through the foot, c, of the angular piece to the screw, b, in whose little concavity a drop of quicksilver is put. From here the current then goes through the little telegraph apparatus, e-f, then to the key of station C, and through the spiral past i back to B.
Fig. 29.
If now sufficiently strong tones are produced before the sound-aperture, S, the membrane and the angle-shaped little hammer lying upon it are set in motion by the vibrations; the circuit will be once opened and again closed for each full vibration, and thereby there will be produced in the iron wire of the spiral at station C the same number of vibrations which there are perceived as a tone or combination of tones (chord). By imposing the little upper case (Oberkästchen) firmly upon the axis of the spiral the tones at C are greatly strengthened.
Besides the human voice (according to my experience) there also can be reproduced the tones of good organ-pipes from F—c' and those of a piano. For the latter purpose A is placed upon the sounding-board of the piano. (Of thirteen triads (Dreiklänge) a skilled experimentor could with all exactness recognise ten).