RU1771085C - Combined microphone - Google Patents

Description

1

(21) 4878156/10

(22) 07.08.90

(46) 10.23.92. Bull. Number 39

(75) P.Ya. Oceania and B.D. Balanovsky

(56) Coming from A.V. Radio broadcasting and electroacoustics .- M: Radio and communications, 1989, p. 87-88. (54) COMBINED MICROPHONE

(57) Use: relates to transducers of acoustic vibrations into electric ones, in particular to condenser-type electric microphones (sensors). SUMMARY OF THE INVENTION: The electronic converter is made in the form of a symmetric transistor multivibrator, in which the capacitors of the base circuits of the first and second transistors are formed by the first and second capacitors, respectively. 4 ill.

The invention relates to transducers of acoustic vibrations into electric ones, in particular to condenser-type electric microphones (sensors), in which a sound wave acts on their sound-receiving element - a membrane.

The purpose of the invention is to improve noise immunity.

This goal is achieved by the implementation of an electronic transducer in the form of a symmetric transistor multivibrator.

The drawing shows a schematic diagram of a microphone.

The combined microphone contains a generator assembled on transistors 1 and 2, discharge circuits 3-4-5 and 6-7-8, load resistances 9 and 10 in the collector circuits. In the generator feedback circuits, capacitors 3 and 6 of the capacitive differential sensor 11 are installed together with quartz resonators 4 and 7. Between the collectors of transistors 1 and 2 is connected

load 12 - speaker (telephone or audio amplifier).

When the sound wave P acts on the rotor (membrane) of the capacitors 3 and 6 in the feedback circuits, their capacitance changes, which will lead to a change in the half-periods of the multivibrator. The nature of the change in capacitance will correspond to the change in pressure of the sound wave on the rotor of the capacitors of the microphone sensor. In this case, the average values of the currents flowing through each transistor (1-2) are proportional to the pulse durations on the transistor collectors. The same currents create varying voltages at the collector loads 9 and 10, the law of which corresponds to a change in the pressure on the rotor of the microphone sensor from the sound wave. At a load 12 connected to the collectors of transistors 1 and 2, a useful audio information signal will be generated. Harmonics in the range of sound frequencies from the operating frequency of the multivibrator will be filtered quart

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4 and 7 and will not get to the load of the 12 multivibrator, since the excitation of the multivibrator will occur only at the resonant frequencies of the quartz, which lie beyond the frequency range of the useful (sound) information.

Thus, by abandoning the microphone amplifier and eliminating the need for shielding the feeders, a structurally simple low-cost, high-quality microphone with high operational characteristics and an uncritical power supply was obtained. Due to the sufficient output power, the multivibrator circuit can also be applied in

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Editor

Compiled by P. Oksanich Tehred M. Morgenthal

cadech of anode modulation of radio transmitters.

Claims (1)

SUMMARY OF THE INVENTION A combined microphone comprising two capacitors, each of which is formed by movable and fixed plates connected to an electronic converter, characterized in that, in order to increase noise immunity, the electronic converter is made in the form of a symmetric transistor multivibrator, in which the capacitors of the base circuits of the first and second transistors are formed by the first and second capacitors, respectively. - (Jo l // «« CczasowssB ig, 5 . / R1 tg f „a- r4l tfJ / S 5FV / 4 Proofreader M. Andrushenko