US1484509A - Microphone transmitter - Google Patents

Description

Patented l lg t.

Una ares? PATENT @Fldlltilgo HENRY G. REACH, OF BROOKLYN, NEW YORK, ASSIGNOR T ELECTEIEGAJL INDUSTRIES MANUFACTURING 00., OF NEW YORK,

N, Y., A CORPORATION @Ii' NEW? YORK.

MICROPHONE TRANSMITTER.

Application filed June 22, .1920. serial Ito. $90,898.

' To all whom it ma concern:

Be it known that I, HENRY G. LEACH, a citizen of the United States, and a resident of Brooklyn, in the county of Kings and State of New York, have invented certain new and useful Improvements in Microphone lransmitters, of which the following is a specification.

. The invention relates to telephone transmitters of the microphone type employing electrodes composed of a carbon or like diaphragm and a mass of globular conducting material general] in the form of a pluralityof carbon pe lets suitably retained. It has been found that transmitters of this type, while particularly sensitive to sounds of acertain pitch, do not respond so well to pitches ranging considerably. These transmitters, also, have a tendency to howl or whistle; and it is the object of the present invention to provide a microphone transmitter in which this tendency is greatly diminished, if not entirely obviated, and a diahragm which will respond and give a clarirange of pitch.

The nature of the invention will best be understood when described in connection with the accompanying drawings, in whichi Fig. 1 is a plan view with portions of the cover and diaphragms removed.

Fig. 2 is a partial vertical section thru the transmitter.

Fi 3 is a partial vertical section ofthe supp ementaryg diaphragm and retainer therefor. I

Similar characters of reference designate corresponding parts thruout the several to views.

Referring to the drawings, 10 designates a suitablecasing provided with a removable screw cap or cover, 11 having centrally disposed openings 12 therein thru which aerial sound waves may freely enter. Within the casing is designed to be included the microphonic transmitting elements comprising two electrodes, for example a carbon dia phragm 13 whose central portion rests over ed tone to sounds comprised in the normal and makes contact with a plurality of globular carbon pellets 14 arranged in a suitable supporting member 15 having circularly disposed conical cavities 16, for example. As is well understood, vibrations imparted to the diaphragm 13 will serve to vary the electrical resistance between the two electrodes and thereby the current flowing in an external circuit (not shown).

As heretofore noted, however this type of transmitter possess certain inherent disadvantages, due principally to the fact that the aerial sound waves impinge directly on the diaphragm 135 and, in accordance with the present inventlon, a supplementary diaphragm is provided to prevent this action, the sound waves bein received directly by said supplementary iaphragm. For example, a diaphragm 20 composed preferably of silk or other meshed material or a membrane, and which has been pre ared or impregnated with a suitable me ium serving to stretch the same taut and substantially fill the interstices thereof, may be mounted in predetermined spaced relationship over the spacing and both diaphragms being hel by the cap 11 to the casing 10.

There is thus provided an air cushion between the two diaphragms; and furthermore, the sound waves are excluded from-direct action on the dia hrs. 13 which is afiected solely by the vibrations of the diaphragm 20 transmitted thereto thru the said air cushion. No violent concussions are thereby permitted to act upon the resistance varying members and a clarified tone is obtained and whistling and howling eects greatly diminished.

Various media may be employed for the supplementary diaphragm 20, but I have found Japanese silk impregnated with collodion to be very efiective for this purpose; and also a distance of fifteen one-thoutilt tilt

sandths of an inch between diaphragms to intermediate air cushion and consisting of afi'ord a suitable air cushion. Japanese silk impregnated with collodion I claim: v stretching the same. 10 In a telephone transmitter of the charac- Signed at New York in the county of New 5 ter set forth and including a resistance vary- York and State of'New York this 21st day ing diaphragm; a supplementary diaof June A. D. 1920. phragm separated therefrom to provide an HENRY G. LEACH.

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