DE353644C - Differential circuit to control the amplitudes of high-frequency, undamped oscillations in the rhythm of acoustic oscillations - Google Patents

Description

GERMAN EMPIRE

ISSUED MAY 23, 1922

REICH PATENT OFFICE

PATENT LETTERING

- M 353644 CLASS 21 a GROUP 25

Joseph Massolle in Berlin-Grunewald, Hans Vogt in Berlin-Wilmersdorf and Dr. Joseph Engl in Berlin-Grunewald.

Differential circuit to control the amplitudes of high-frequency, undamped Vibrations in the rhythm of acoustic vibrations.

Patented in the German Empire on March 4, 1919 .

For converting acoustic vibrations into electrical characteristics of the same type So far, body microphones have been used almost without exception. These give to small ones S amounts of energy relatively good transfers

of acoustic vibrations (speech, etc.). However, they have their own noises which are particularly noticeable when amplified.

The present invention provides a

853644

Circuit that allows high frequency energy in the rhythm of acoustic vibrations naturally influence au.

The tube R (Fig. I) generates high-frequency oscillations of constant amplitudes in a high-frequency circuit 6 ". Coupled with this circuit are two circuits D ₁ and D ₂ , called differential circuits, which are completely identical electrically. They both take ίο from the feed circuit 6" the same amount of energy. If the electrical quantities of D ₁ and D ₂ are completely identical, the "current phases" are: "he circles in resonance; but their effects on the coupling circle K cancel each other out, since they are shifted from one another by 180 ° (Fig. 3a). If the equality of the circuits D ₁ and D _{2 is} disturbed, then the current phases get a shift from one another, the difference of which is transferred to the circuit Jf. By changing the capacitance of D ₁ and D ₂ in the opposite direction, for example, the current phases of both circuits are shifted in opposite directions. Shifts to do a phase + 90 ^0, the other by -90 °, so their effects are the same directed to K and are added to the resultant R _b in Fig. 3b. The capacitive change required for this is small, so that the change in the frequency of the circles is insignificant is borrowed. Such capacitive changes can be brought about by a capacitor, one of which is designed as a membrane; is so that he follows the rhythm of the acoustic ^; Oscillations follows and its capacity changes periodically accordingly. The effect of the differential circuits is not disturbed by the one-sided connection of their capacitors! (Fig. 2). This type of connection offers the following advantages: the capacitors can be designed to act on both sides, in that the membrane forms the common plate for both capacitors, as can be seen in FIG. The advantage here is that the membrane is relieved of electrostatic attractive forces 1 and can therefore be made so easy that it follows the acoustic oscillations absolutely. If the difference circles are set so that their effect on circle K when the membrane is at rest is Nu !! in K causes the high-frequency amplitudes to increase and decrease again, while these amplitudes may only increase and decrease once. For the purpose of voice transmission, etc. It is therefore necessary to detune the circles before so that their current phases .are moved from the start by 90 ⁰ (labb. 3c). The current curve of the circle K then corresponds to the resultant R _c in the idle state, the energy of which is half as large as the resulting energy under phase equality according to Fig. 3b. The changes in capacitance of the microphone at maximum acoustic amplitudes are such that the phase shift is maximally between 0 ° and 180 ° ptirl (Figs. 3a and 3b). The amplitude of the high-frequency energy of the circle K is then controlled by the acoustic effects between zero and a maximum.

Claims (3)

Patent Claims: r. Differential circuit - for controlling the amplitudes ^{1 of} high-frequency, undamped oscillations in the rhythm of acoustic oscillations for the purposes of recording, playback and remote transmission, characterized in that two normally electrically completely identical circuits, which are fed equally strong by a high-frequency energy source and in differential coupling to a third circuit act, are influenced by acoustic oscillations in such a way that current phase shifts occur in opposite directions in both circuits, the resulting effect of which is transferred to the coupling circuit. 2. Differentialscihaltunig according to claim i, characterized in that for purposes of lifelike transmission the acoustic oscillations in the correct pitch the two circles beforehand to half of the maximum phase shift be brought so that the amplitude of the coupling circle at maximum Change oscillates between zero and a maximum. ' 3. Differential circuit according to claim i, characterized in that the Influence on the two circles of difference expediently done by a double-acting capacitive microphone in such a way that one through the acoustic 'The membrane caused the two capacitors of the differential circuits to vibrate opposite changes. For this t sheet of drawings.