US1521275A - Telephone headset - Google Patents

Description

Dec. 9 1,521,275

a. w. CARPENTER ET AL TELEPHONE HEADSET Original Fi1ed Jan. 29, 1921 6R0: nu,

Patented Dec. 30,1924.

UNITED STATES PATENT FFIC GLENN W- CARPENTER AND WENDELL L. CARLSON, F SCHENECTADY, NEW YORK.

TELEPHONE HEADSET.

Original application filed January 29, 1921, Serial No. 440,982. Divided and this application filed April 25, 1924. Serial No. 709,050.

To all whom, it may concern:

Be it known that we, GLENN W. CARPEN- Ten and 'WENDELL L. CARLsoN, citizens of the United States, residing at Schenectady,

in the county of Schenectady and State of New York, have invented certain new-and useful Improvements in Telephone Headsets, of which the following is a specification. I Our-invention relates broadly to electromagnetic telephone receivers and more particularly to telephone headsets for use in radio receiver circuits, and has for an object to prevent the deleterious efi'ects caused by ,15 electrostatic, electromagnetic and direct coupling which normally exists between the telephone receiver circuit and other circuits particularly with circuits in multistagepr igh power radio receiving electron tube amplifiers of great sensitivity.

This application is a division of our application Serial Number 440,992 filed J anuary 29, 1921.

Another object of our invention is to shield the telephone cords of the headset from strays or any external electrical disturbances which normally tend to afi'ect a sensitive electron tube amplifier.

Still another object of the invention is to provide a construction of flexible electri-- cally' shielded cord for telephone headsets wherein a shield or braiding of tinsel thread is woven. over'the conductors throughout their length and which may be connected at one end with a low pqtential circuit and at the other end with the telephone receiver casings. v

'Great difliculty has been encountered heretofore when telephone'receivers were used in conjunction with high amplification electron tube apparatus, due to the fact that a coupling exists between the telephone receiver circuit and other circuits in t e apparatus or external circuits. This coupling, insome instances, causes a detuning of the oscillatory circuit, while in other cases it produces oscillations in the tele hone receiver circuit which is commonly own as howling when of an audio frequency. J 4 I i We will now describe in detail our shielded telephone head set which prevents the above described coupling, references be which Figure 1 is a perspective view of the telephone receivers and connecting cords, parts being broken away to more clearly show the construction; Figure 2 is a detail perspective vlew of a portion of the telephonecord, showing an embodiment of the invention in the construction of the cords and arrangement of the conductors therein; and Figure 3 shows a modified construction of the flexible electrical shield surrounding the telephone conductors in accordance with our invention. I j

Our invention contemplates the provision of an extremely flexible metallic tinsel braid woven over the telephone cords on the headset. The tinsel braid may be formed from fine copper wires each of which has a textile core in the wellknown manner of standard stranded electrical conductors, the several textile cores and wound wires bein braided to form a substantially closed flexi le housing throughout the length of the cords. The ends of the shield may also serve as a stay cord to prevent any undue strain being placed upon the conductor itself.

Referring more particularly to the drawings, Fig. 1 is a perspective view of our im-' proved telephone headset in which reference characters 22 designate the insulated conductors which lead to the telephone receivers 3- 3. These conductors may be covered with the usual insulating cotton cord covering 7 "if desired. Surrounding the insulated conductors and the cotton covering, if thelatter is used, is a flexible metallic casin or shield 4. {[he shield 4 is constructed 0 woven tinsel conductors as more fully shown in Figs. 2 and 3, that is to say, flexible metallic conductors braided together. As illustrated in the drawin s, the metallic strands of the shield 4-may e substantially the same as the metallicstrandsof conductors 2- -2 and may be helically wound with a. textile core the same manner as the strands of conductors 2-2 are ordinarily twisted. This flexible casing or shield is directly connected to the telephone receiver casings and headband as indicated at 5-5. The tinsel braiding may be more closely-woven at the points 5-5 where the conductors are brought out of the braiding to provide a conducting strand which may be grounded to the casings of the telephone receivers and which mayalso serve as a stay cord to prevent any undue strain being placed upon the conductor itself. That portion of the shield indicated by reference character 6 may also be more closely woven than the other part of the shield to provide a connection to a' low potential circuit or ground at the same time that it serves as a tie cord for thetelephone conductors. Reference character 8 indicates an insulated protective covering or braiding which is placed over the flexible metallic shield.

In Fig. 3 we have represented a modified form of flexible electrical shield for telephone headsets wherein one of the conductOIs is arranged within the other, the outer conductor being hollow to receive the'inner conductor. That is to say, the shield indicated by reference character 4 in Fig. 3 surrounds but is insulated from an inner conductor 2, the shield 4 serving as one of the conductors.

When a metallic shield is not used with telephone headsets in connection with sensitive electron tube amplifiers, any alternating currentenergy existing in the telephone receiver circuit may by electrostatic or electromagnetic coupling, existing between the conductors and other circuits in the apparatus, cause oscillations to be set up in the amplifier circuits. If these conductors are now enclosed in a metallic shield, which shield is preferably electrically connected with the telephone shells and with a low potential conductor, it is apparent that the shield will prevent the couplings referred to and there fore prevent an effective transfer of energy from the circuit formed by the telephone conductors, thus eliminating this well-known annoying disturbance.

Our invention finds application in all multistage electron tube circuits connected to actuate a responsive device in which the usual reaction must be eliminated employed in connection with either line wire carrier wave systems or in radio systems. By use of the invention many additional stages of amplification may be employed and arranged to function without the inherent reaction of circuits which would occur under normal circumstances.

hat we claim and desire to secure by Letters Patent of the United States is as follows:

1. A telephone headset, comprising in combination a pair of electromagnetic sound reproducing devices, an insulated conductor connecting said devices, a flexible braided shield surrounding said conductor, said shield consisting of woven tinsel conductors and a protecting braid about said shield.

2. A telephone headset, comprising in combination a pair of electromagnetic sound reproducing devices, an insulated conductor connecting said devices, a flexible braided shield surrounding said conductor, said shield consisting of closely woven metallic conductors terminating in stay cords at each end 'for preventing any undue strain being placed upon said insulated conductors.

3. A telephone headset, comprising in combination a pair of electromagnetic sound. reproducing devices, an insulated conductor connecting said devices, a flexible braided shield surrounding said conductor, said shield continuing beyond the ends of said insulated conductor to provide stay cords atthe telephone receiver ends of said insulated conductor, and a tie cord formed by said shield at the opposite end of said insulated conductor opposite said telephone receiver end.

4. A receiver cord comprisin a plurality of insulated conductors, a exible electrical metallic shield surrounding said insulated conductors said shield continuing beyond the ends of said conductors to provide stay cords, and a textile protective braiding about said shield.

5. A telephone headset, comprising in combination a pair of electromagnetic sound reproducing devices, an insulated conductor connecting said devices, an electrostatic shield completely surrounding said insulated conductor, said shield comprising a plurality of flexible braided tinsel con uctors and serving" as a connection separate from said first mentioned connection between said devices. v

GLENN CARPENTER. WENDELL L. CARLSON.

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