DE617796C - Speech head for the reproduction of phonetic transcription recorded in longitudinal magnetization - Google Patents

Description

GERMAN EMPIRE

ISSUED ON
AUGUST 28, 1935

REICH PATENT OFFICE

PATENT LETTERING

JYe 617796 CLASS 42 g GROUP 10 oi

P 66508IXj42 g Date of publication of the patent grant: August 8th

General Electricity Society in Berlin *)

Patented in the German Empire on November 26, 1932

The invention relates to a headset, i. H. a device to the magnetic Convert the recording of sound waves into electrical vibrations. This conversion is done by using the phonetic carrier moves under or past the pole edges of an iron circle with the lowest remanence, the alternating magnetic fields entering the iron circle from which they then converted into electrical currents by electromagnetic induction in a wire coil will.

Fig. Ι represents a speech head that is used to pick up phonetic transcription, their magnetic Polar axes lie in the band plane, an embodiment, as one has both so far used for recording as well as playback, ι is the iron circle, 2 is the wire spool, 3 and 4 the pole edges with a narrow gap S for recording and playback effective place. 6 denotes that which is guided over the pole edges 3, 4 in closest contact tape to be magnetized.

Although such a device is eminently suitable for recording, ie for generating a magnetization 8 that is proportional to the sound curve 7 (Fig is to be reproduced in their form and in their strength exactly according to the recording.

Example " ₃₅

A tone of 3000 Hertz is to be reproduced at a tape speed of 6oomm / sec. The width ί of the gap S is ¹ Z ₁₀ mm. The gap 5 covers a half-wave 1 (Fig. 3), and the recorded magnetic moment M is no longer an ordinate 8, but the sum of all ordinates established at infinitely small intervals.

naten:

»
i8o °

45

_ _ti = Vsinada.

If you want to pick up a very low tone with the same gap 5, about 100 Hertz, whose half-wave length on the band 6 is equal to 3 mm, i.e. 30 times as long as that of 3000 Hertz, one would only use an area integral over this sound curve 9 180: 30 equal to 6 degrees of arc with a correspondingly small change in field strength obtained, d. H. the lower notes turn strongly disadvantaged, which the experiment also confirms. on the other hand but if a tone of 6000 Hertz, curve 10 (Fig. 3), would not be reproduced at all, since the magnetizations of the two half waves, their direction indicated by the arrows

*) The patentsitcher has given as the inventor:

Frits Pfleumer in Dresden.

is designated, cancel in the iron circle ι. The reproduction would be with three half-wave trains appear weak again for each gap, only to disappear again with four half-wave trains etc.

In general, for a given slit width £ for any half wavelength λ on band 6:

M = J l / sin ada = K ·] / (τ - c

In Fig. 4 this equation is shown on an abscissa X , on which the half-wavelengths and frequencies of the magnetogram are plotted in logarithmic graduation. This curve has a maximum value at the half-wave length equal to the slit width, drops sharply to the left for the low tones, sinks to zero to the right for the half-wave length, reappears at ¹ Z ₃ half-wave length, disappears again at ^x / ₄ half-wave length, and so on The curve is confirmed by measurements with a satisfactory accuracy.

If all tones of the scale audible to the human ear are to be perceived as loudly during playback, then according to the known law, their amplitudes A (Fig. 5) must be inversely proportional to their number of vibrations, i.e. directly proportional to the recorded half-wavelength X the area integrals over 180 degrees of arc are then proportional to A ² . For playback, however, it must be remembered that at least in the case of recording media with a recording layer made of magnetizable powder, the internal resistance of the tape 6 is far greater than the resistance of the iron circle 1 (Fig. 1), the former is therefore only used for the calculation . It is again proportional to the half-wave length λ and under the condition that A is proportional %, also proportional to the amplitude A. If one calculates the strength of the magnetization flowing into the iron circuit, which results in a proportional EMF of the speech current, then this is magnetic Moment divided by the magnetic resistance equal to the area integral above divided by the magnetic resistance, therefore proportional ^ ³ : A equals: A, that is, a reproduction proportional to the recorded sound curve is obtained for all half-wavelengths if the magnetic moment of each wave is greater than 180 Integrated arc degrees.

One headset with such an integrator, which automatically integrates any half wave up to a limit value over 180 degrees of arc, without overlaying (inter To have reference) phenomena is the subject of the invention.

The invention consists in that one (Fig. 6) or both (Fig. 7) sensing poles 13 of the iron core 1 parallel to the gap between them, which in a known manner is placed transversely to the running direction of the voice tape, are scrolled, useful in such Width that the longest audible half-wave is more than 180 degrees from the Foliation is achieved.

Figs. 8, 9 and 10 show the theoretical prerequisites for the creation of integration.

In diagram 8, the sine curve 7 on the left is developed by rotating the vector V. The area integration is replaced here by summing the directional elements V, ie by constructing the parallelograms of forces, where the resultant R. (V tmemdlich thought small;) your circle K. runs through. The points 90, 180, 270, ⁰ that belong together are noted on the curve M and the construction circle K. M is the perpendicular component to V according to the rules of the vector diagram. According to the above equation, when integrating over "180 degrees of arc - ,, - because S = X, M = K- ^ V ₃ is equal to the largest resultant R _{1 is} equal to the diameter of the -Kreises-iT »The position of R ₁ only applies to the point in time shown, where the zero point of the sinusoidal curve 7 coincides with the pole edge 3. If one wants to extend this process over time, that is to say to determine which values M _{1 are used} to deliver the If the EMF of the speech current passes through, one must rotate the ordinate Y with the construction circle K and the values of R fixed there in accordance with the movement of the band 7 by O , as indicated by the dashed arrows be large M and whichever direction the resultant R in the construction circle has, extends over time, M will always be a sine curve - in the rectangular coordinate system - if the generating curve 7 was a sine curve,

Fig. 9 shows that with this arrangement the resultant ^ of the magnetomotive forces automatically find their way. searches in the iron circle, ie every half-wave automatically flows through the iron circle ι summed up to the maximum value M. The feathered arrows represent the direction of magnetization, the ordinates V ng the strengths of the magnetization, and M again over its integral. 180 degrees of arc. Where the opposing magnetizations meet on a leaf 14 of the peeled pole, they flow in the direction of the arrow into the iron circle 1, 3.

Fig. 10 shows that the resultant R

are parallel to each other over 180 degrees of arc if the zero points of the generating sinusoids coincide with the pole edge 3, i.e. if a shift L between the largest and smallest half-wave is canceled or generated, which remains inaudible to the human ear, every half-wave remains The above statements are precisely proportional to their strength.

The headset described therefore has the property of making a sound recording that always consists of a summation of any set of sinusoids, again in to decompose their individual sinusoids, d. H.

¹ S the theoretically required integration of the magnetomotive forces over 180 degrees of arc to be taken from each and to send them into the iron circle 1 and through the wire coil 2 to generate the EMF of the speech current, so that this again faithfully represents the composite sound curve.

For phonetic carriers where the magnetized base is made of iron or steel powder exists, the present device still has the significant advantage that it has the Powder grains metallic conductive at the moment of passage through the speaking head summed up and thereby considerably reduces the magnetic resistance of the tape at the moment of passage. The advantage such writing bases exist in addition to their easy divisibility and assemblability in that - that the magnetized powder grains due to the air resistance between them do not influence each other, opposite wave trains therefore do not demagnetize. Their disadvantage so far was their high magnetic resistance, which causes a considerable gain.

Fig. 11 shows the contact of the powder surface of the phonetic carrier 6 with the interface of the pole leaves 13. The lower part of Fig. 11 shows that even if only a very small fraction of the granules 15 come to lie on the column 16, they do the conclusion from 3 to M can be a metallic magnetic one if the gaps are of the order of magnitude of the grains. The phonetic carrier 6 is usually allowed to run with its powder surface directly on the surface of the foliage 13 in order to come as close as possible to this conclusion. So that the blades 13 do not cause any background noise, they are pressed together strongly with non-magnetizable spacers 17 and pressing plates 18 and the surface is machined by turning and polishing until it is mirror-like.

According to Fig. 12, the device according to the invention can also be used for those speech heads whose pick-up poles are on both sides of the tape. According to the above, this device is of considerable value only for steel strip. For integration over a half wavelength, it is sufficient if only one pole is scrolled. The flapping of both poles has for both uses, the one-sided or two-sided decrease, compared to the single-pole only the effect that the slight displacement L 'between short and long waves is increased to L ₁ (Fig. 10).

Fig. 13 represents a particularly effective one Embodiment of the inventive concept. Here the coil 2 sits just below the Gap 5 directly on the peeled pole 13. Because this is made of the thinnest sheet metal or Films, up to 0.01 mm, are produced against each other by a very thin coat of paint are isolated, this pole has a strong tendency to scatter. For this reason it is advantageous to in order to use all lines of force for the coil 2, this close to the take-off point 3, 5, 13 and the lower contact area between 1 and 13, where the Lines of force penetrate the foliage transversely, extending it as far as possible.

Speech heads often tend to make running noise if, for whatever reason, the iron path 1 has picked up remanent magnetism. The reason is that belt 6 is no longer the only generator of the magnetic oscillations, but also the now existing magnetic moment of the iron path r in connection with the change in resistance between belt 6 and the take-off point, which is always produced by running. With powdered writing floors, there is the additional effect of powdering, uneven spreads and paper, etc. In order to suppress these harmful effects, in a further development of the invention, an iron path 19 is also placed on the other side of the leaf pole 13, which, however, in order to avoid interference, does not lie close to 13 as shown in FIG Conclusion by air. Since the resistance of this inference is significantly smaller than that of a powder-coated tape over 3.5 »13, the lines of force of these harmful noises are closed via the airway without penetrating the coil 2. This inference also protects the coil from interference from external stray fields F from high-voltage devices such as drive motors, mains anodes, etc. The single-pole leafing has the advantage that the gap 5 can be made more precisely than with the two-pole (Figs. 7 and 12). The core 1 is screwed to the press plates 18 and ground in at the gap surface 5,

while the flaky pole 13 does not allow grinding, the ground pole 3 is only pressed on.

In Fig. 13, the Eisenweg covers 1 as well as Gap S and pole 13 only half the width between Back plate 18 and run-up edge 21. These The device is intended for double recording on one strip, there and back. The plate between ι and 21 is omitted for simple meetings.

Claims (3)

Patent claims: i. Talk head for playback of recorded in longitudinal magnetization Phonetic transcription with a gap placed transversely to the running direction of the speaking tape merged poles, characterized in that one or both poles (3, 13 in Fig. 6, 9 or 13, 13 in Fig. 7, ao 12) of the speaking head are scrolled parallel to the gap. 2. speaking head according to claim 1 with only one scrolled pole, characterized in that that the scanning coil (2) sits directly under the scanning gap (5) on the peeled pole (13). 3. Talk head according to claim 1 and 2, characterized by a magnetic Inference (19 in Fig. 13) showing the perturbation lines of force closes over the sensing coil (2). 1 sheet of drawings Correction sheet for Patent 617,796 class 42g Group 10/01. On page 1, lines 45-48 and on page 2, lines 9-15, the letter V (capitalized Latin Vau) must be used in the formulas instead of the root sign \ l.