US 2535063 A
Description (OCR text may contain errors)
Dec. 26, 1950 w. s. HALSTEAD 2,535,063
COMMUNICATING SYSTEM Filed May '5, 1945 3 Sheets-Sheet 2 INSERT EARPIECE OR OTHER TRANSDUCER WORN 1 ON HEAD OUTPUT AMPLIFIER INPUT TNORMAL RECEIVE M 45 so v 49 7- I I q 39 PRESS-TO-TALK T 42 4s CORRECTION INPUT I FILTER 1OUTPUT TO INTERCOMMUNICATION CIRCUIT 4| 4&
WILLIAM S. HALSTEAD INVENTOR TORNEY HALSTEAD Dec.- 26, 1950 COMMUNICATING SYSTEM Fild May 3 19 3 Sheets-Sheet 3 FIG. 4A
TRANSMIT WILLIAM S. HALSTEAD INVENTOR RECEIVE ATTORNEY Patented Dec. 26, 1950 umro STATES ATENT orrice ooMMuNIcATING SYSTEM William S. Halstead, Purchase, N. Y., assignor, by mesne assignments, to Farnsworth Research Corporation a corporation of Indiana Application May '3, 1945, Serial No. 591,742
2 Claims. 1
This invention relates to systems for two-way electrical communication where a single trans-- ducer functions both as transmitter and as receiver.
In two-way electrical communication systems, it has hitherto been the usual practice to employ two separate transducers, one transducer being usually placed at, or within auditory range. of the ear of the operator, this transducer serving to convert the received electrical signals into acoustical energy, which latter will then act upon the physiological hearing organs of the operator. The other transducer was usually placed in proximity to the operators mouth, and was elit rayed to pick up speech as it issued 'dire'ctlyfroin the mouth, and to convert the acoustical energy into e1ee trieai signa s.
In some instances it has been proposed to em ploy a single transducer capable of functioning alternatively in both senses, i. e. to convert elcc trical energy into reproduced sound and to conv'ert sound energy into electrical wave forms; The use of a single transducer has suffered, inter alia; from the disadvantage that such instrument. if placed sufficiently close to the mouth to act as a transmitter, could not, in this position, act with equal efficiency asa receiver. One proposed solution for this difiiculty was to alter the position of the transducer from a position adjacent the mouth to one adjacent the ear, whenever re ception was initiated, and to make-Ia reverse movement of the transducer, whenever transmission was initiated. Such alteration of the position of the transducer either demanded that the operator employ his hand to effect such movement, or else that he move his head from one position to another, in order to approximate the desired portion of his headto the transducer. Either one of these species of movement demanded attention on the part of the operator, which often prevented him from accomplishing other needful duties and very frequently the movements of the operator were not strictly or properly coordinated, when changing from a transmitting to a receiving position, or the received signals were often lost in part, because, at the moment of reception, the transducer would be located either near the mouth of the operator, or would be in transit to or from his ear.
The present invention overcomes the above recited difiiculties and. yet allows the employ-mentof a single transducer. This is accomplished by permanently locating such transducer either par tial-ly within or closely adj acent the ear. In such location, the transducer functions somewhat as a telephone receiver of the well known hearing aid type. When acting as a transmitter; the transducer, remaining in the same position, picks up the auditory vibrations which are present within the ear or in the bone structure adjacent the ear, or from both such sources.
One object of this invention is to provide a two-way, or lei-lateral transducer which may be carried or worn by an individual user in an unobtrusive manner, and which transducer will act without alteration of position when change of the function performed is made, from transmission to reception, or Vice versa.
Another object of this invention is to provide a bi-lateral transducer which is so constructed and located with respect to the person of the operator that it functions as an ambient noise reducing microphone during periods of transmission, and as a similar sound discriminatory receiver during periods of reception.
A further object of this invention is to provide a single transducer which may be more or less permanently worn by an operator and which may function alternatively for either transmission or reception, without requiring the employment of the operators hands and without any substantial interference with, the freedom of movement of the operator.
Yet. another purpose of this invention is to provide, as a single unit, a complete radio transmitter and receiver, having a single transducer, which unit will be highly portable and may be worn upon the person of the operator and which will incorporate therein all essential elements, including an antenna.
Still another object of this invention is to provide a bi-lateral transducer adapted to lie positioned adjacent the ear of the operator and to be connected to the transmitting and receiving apparatus proper by a composite conductor, which conductor functions both to lead speech frequency currents to and from the transducer, and at the same time functions as a radiative and receptive antenna.
A yet further object of this inventionis to provide a transmitting and receiving unit for use in an intercommunications system, for esample on an aircraft, in which a single transducer is employed at, or adjacent the operator's ear, and in which, due to such location, the transducer will function satisfactorily in a milieu of relatively high ambient noise level, even though such level be sufficiently high to cause difficulties when transmission microphones of conventional types are employed.
Another purpose of this invention is to employ, in two-way electrical communication systems, a transducer which is located partly within the ear of the operator and which operates as a transmitter partly by picking up relatively high frequency sounds transmitted to the operators ear via the Eustachian tube, and partly by picking up relatively low frequency speech vibrations transmitted to the transducer via the bone structure in or adjacent the operators ear.
Another purpose of this invention is to provide a bi-lateral transducer fitted with a rubber cushion or the like so that when it is inserted as far as possible within the ear, such cushion will effectively seal off and reject extraneous sound waves, arising from sources external to the operator.
Other purposes and advantages of this invention will be seen from the following specification and from the drawings hereunto afiixed.
In the drawings:
Fig. 1 is a block diagram of a portable two-way radio telephone unit employing a single trans ducer according to this invention.
Fig. 2 shows one embodiment of a two-way radio telephone, utilizing the circuit of Fig. 1, as worn upon the person of the operator.
Fig. 3 is a block diagram of another embodiment of this invention, constituting a single twoway station of a wire intercommunication system.
Fig. 4A shows the bi-lateral transducer of this invention located partly within the ear and illustrating the operation of the transducer as a transmitter, and
Fig. 4B is similar to Fig. 4A, but shows the transducer functioning as a receiver.
Theblock diagram of Figure 1 illustrates the arrangement of units employed in the radio communicat ons system of the invention, including a miniature portable receiver H, a portable transmitter l2, and an audio-frequency input correction filter Hi having high-pass frequency characteristics, all of which are preferably combined in the form of a transceiver 32, having a multicontact switch It to shift from the normal or receive position, to the transmit position. A transducer I8 is provided for use as an ear hone during reception and as a microphone during transmission. The transducer may be-either the insert earphone type as shown or one of the well-known bone conduction type, not illustrated, the insert type being placed inside the ear and in the case of the bone conduction type, worn behind the ear, as is common practice in connection with hearing aids.
The antenna 29 is combined with the transducer conducting lead wires 2! into a single flexible cable provided with suitable insulating material, 2|, having a low dielectric constant and separating the inner transducer conductors 2i from the outer metallic braided antenna con-.
ductor 20, and also an outside layer, 25 of insulating material forming a protective coating around the antenna conductor 2t (Fig. 4A)
In the normal or receive position, movable contact 23 of switch l5 connects to contact 2d, which in turn connects the antenna circuit to the radiofrequency signalinput circuit of receiver Ii. Movable contact 26 connects the transducer E8 to contact 2'5, which in turn connects to the audio-frequency output circuit of receiver 15. The circuit from transducer 3 to receiver H is completed by means of a common ground conall) nection. Spring 25 holds the switch it in the normal or receive position.
When the switch It is moved to the transmit position, movable contact 23 connects the antenna 20 to the contact 28, which in turn connects the antenna 28 to the radio-frequency output of transmitter l2. When in the transmit position, the movable arm 25 of switch it; connects the transducer l8 to the lower contact 25, and thence through the audio-frequency correction filter l4 to the signal input circuit of transmitter I2.
The single transducer [8 thus normally functions as a receiver earphone during stand-by periods, and'as a microphone when transmitting, without need for the operator to move the transducer from ear to mouth, and without requiring the use of the operators hand in holding a microphone to the mouth, as has been common practice in the past. When transducer is, of the insert" type, is employed in the above-described manner, it has the added advantage of effecting a material reduction in outside noises, this result being obtained largely by virtue of the properties of the bone structure of the operators head, which structure has pronounced sound absorbing qualities to external noise and causes great attenuation of any sound wave energy which may reach the diaphragm of the transducer from sources external to the wearer of the transducer.
The audio-frequency filter M is inserted in the transmitter input circuit in order to attenuate thepreponderant low frequencies of the human voice, as such voice or voice vibrations exist within the structure of the ear or on the surface of the skull. Without the filter, which attenuates the lower voice frequencies and permits the high frequencies topass unimpeded from the transducer microphone, the quality of the voice signals as impressed on the signal input circuit of the transmitter would be such as would cause seriously distorted or unintelligible voice signals at receiving points, with little if any of the higher frequencies above several hundred cycles being evident in the reproduced voice signal. By the use of the correction filter, however, the highfrequency attenuation caused by the acoustic properties of the physical structure of the ear and head may be corrected or compensated, since the filter may be designed greatly to reduce or substantially to eliminate all frequencies below 200 cycles, and to pass without material attenuation all frequencies above several hundred cycles. As a further aid in this directionythe speech input circuit of the transmitter may be designed to effect pre-emphasis of the higher audio frequencies in the voice frequency spectrum, thus causing additional discrimination in favor of the higher audio frequencies, which latter are required in obtaining a high degree of intelligibility of voice reproduction. It is obvious that a special transducer having a diaphragm which is responsive to the higher audio frequencies and relatively non-responsive to the low audio frequencies, which latter exist in the structure of the head, can also aid in increasing I intelligibility of the voice signals.
It may be seen from the drawing of Figure 2 that the radio-telephone shown schematically in Figure 1 may be worn by an operator 3 I, the transducer l8 being in the form of an insert earpiece fitted into theear of the user, and the combined antenna and transducer cord 26, 21 extend ing downward fromthe earpiece to the combined transmitter-receiver unit 32, which latter may be carried in a'pocket of the operator's clothing, as indicated, worn on a belt (not illustrated), or otherwise suitably suspended. The transmitreceive switch I6 provides means for shifting the transceiver from the normal or receive, to the transmit position.
In the diagram of Figure 3, the transducer l8, similar to that shown in Fig. 1, is used in connection with wire telephone transmission, such as that employed in an aircraft. This type of embodiment includes a line amplifier 35, a correction filter l4, similar tothat shown in Figure 1, in combination with a multi-contact switch 49, this switch providing means for shifting the equipment from the normal or receive p osition, to the talking or transmitting position. Transducer l8 functions alternatively as an earphone or a microphone, depending upon its connection through switch 49 to the output circuit or input circuit, respectively, of amplifier 35, and is worn on the head of the user, as previously described.
In the normal or receive position, movable arm 36 of switch 49 connects the transducer 8 to contact 31, which latter in turn connects to contact 38 and thence through movable arm 39 to the output circuit of amplifier 35. The intercommunication circuit, or line, having terminals 48, connects through line 4| to contact 42 and ground, and thence from contact 42 through movable arm 43 to the input circuit of amp ifier 35, thereby completing the receiving circuit from line 4| to the transducer l8. In the embodiment shown in this figure, all circuits have a common ground connection, as indicated by conventional symbo s.
When switch 49 is in the press-to-talk position, transducer l8 functions as a microphone, in the manner described in connection with Fig. 1. When switch 48 is in the above-mentioned position, transducer I8 is connected through movable arm 36 to lower contact 45, thence through the correction filter l4 to lower contact 45, and throu h movable arm 43 to the input c rcuit of am lifier 35. The output circuit of amplifier 35 connects to movable arm 38, of switch 49 and thence to low r contact 41, which latter connects as shown, to the inter-communication line 4| and termina s 48 which latter can connect with a line extending to one or more inter-communication units of the type shown in Figure 3, or of other suitable ty es.
In the same manner as that described in Fig. 1. the transd cer I 8 functions as a receiver earphone when receiving, or as a microphone when V talking, without any need for the operator to hold a microphone to his mouth or to move the transducer l8 from ear to mouth, the correction high-pass filter l4 being used to overcome the obiectional preponderance of low frequencies present in the bone structure of the head, when talking. Inasmuch as the transducer I8, when in the form of an insert earphone, is sensitive principally to voice energy transmitted through the bone structure of the head and passages of the ear, such as the outer ear passage known as the external auditory means. and is relatively insensitive to ambient noise originating outside of the head, a marked discrimination in favor of the operators voice is obtained. The system is thus well-adapted for use in aircraft where high ambient noise levels are present.
Figures 4A and 4B illustrate the cross section of a human ear and its adjacent area, and also show the application of transducer unit I8 to the car,
forthe dual purpose of transmitting and receivmg.
In Fig. 4A is shown the transducer |8 in position to function as a microphone. The soft rubber cushion |8A serves two purposes, first to provide comfort and ease of wearing for the operator, and secondly, to effectively seal off and reject substantially all extraneous sound waves from sources external to the wearers ear. The ear insert section IBB, shown in simple form, may be of a size and shape to fit the individual ear. This insert piece provides a protective housing for the microphone l8 diaphragm, and also contains an unobstructed passageway or cavity, through which, sound waves or vibrations, or the combination of 'both, may proceed, in order to exert a driving force upon the diaphragm of the microphone l8.
This actuation of the microphone I8 is dependent upon the sum of various effects created in the ear and its surrounding area during the time when an individual is speaking. There is utilized the combined effect of sound waves that are present in the internal auditory area, coupled with skull conduction vibrations, or pressures due to acoustic resonances, in order to take advantage of all media for sound transmission.
The sound travels in the direction of the transducer unit l8, as shown by arrows in Fig. 4A, and the consequent diaphragm displacement within transducer l8 results in the generation of an electrical output, which latter is then fed through the twin conductors 2| to correction high pass filter M, for low frequency attenuation.
Fig. 4B represents the identical transducer l8 unit serving as a receiver earphone. Its operation in this casein no essential way deviates from that of the typical hearing aid phone, and its constructional aspects are, in all respects, similar to hearing aid type reproducers. Audio frequency signal energy is applied to the conductors 2| of the earphone cord, which conductors are connected to the reproducing system of transducer l8, and the consequent sound waves are impressed upon the wearer's auditory nerves via the usual inter-aural acoustical path. The direction of sound travel is indicated by the arrow shown in Fig. 4B.
The previously described methods of sound pickup and reproduction, for use in conjunction with the portab e two way radiotelephone system, such as that shown and described in Figs. 1, 2 and 3, may also be practiced when using a bone conduction type transducer and suitable correction high pass filter, as previously mentioned.
What-is claimed as new and desired to secure by Letters Patent of the United States, is:
1. A combination transmitter-receiver, including a transmitter proper, a. receiver proper, a transducer adapted to be positioned adjacent the entrance of the ear of an operator, a cord alternatively leading low frequency energy to and from said transducer, a layer of relatively low dielectric material surrounding said cord, a layer of conductive material embracing said dielectric layer and functioning as antenna means, switching means connecting said transducer alternatively to the input of the transmitter proper and to the output of the receiver proper, said switching means simultaneously connecting said antenna means alternatively to the output of the transmitter proper and to the input of the receiver proper, said combination also including speech frequency corrective means connected between said transducer and the input of said transmitter proper, whereby the distortion of acoustical energy reaching said transducer via the ear is compensated.
2. In a communication system of the type described, including an earphone adapted to be situated at the entrance of the ear, a combination telephone cord and antenna, comprising a twin conductor extending to said earphone and conducting speech frequency currents thereto and therefrom, an antenna formed as a metallic cylinder surrounding and coaxial with the mean centre of said twin conductor, and an insulating material of low dielectric constant substantially filling the space between said conductor and said antenna.
WILLIAM S. HALSTEAD.
REFERENCES CITED The following references are of record in the 'file of this patent? Number I 15 Number 8 UNITED STATES PATENTS Name Date Pridham Oct. 19,1920 Fox 1 Oct. 9, 1934 Johnson June 16, 1936 Ballantine June 28, 1938 Ballantine June 28, 1938 Koch Feb. 28, 1939 Cover June 2, 1942 V Perlman May 18, 1943 Hansell June 1, 1943 Olson Feb. 8, 1949 FOREIGN PATENTS Country Date Germany Oct. 6, 1919