CA1116239A - Two-way voice controlled communication system - Google Patents
Two-way voice controlled communication systemInfo
- Publication number
- CA1116239A CA1116239A CA324,261A CA324261A CA1116239A CA 1116239 A CA1116239 A CA 1116239A CA 324261 A CA324261 A CA 324261A CA 1116239 A CA1116239 A CA 1116239A
- Authority
- CA
- Canada
- Prior art keywords
- transmitting
- circuit
- amplifier
- transistor
- microphone
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
- 238000004891 communication Methods 0.000 title claims abstract description 44
- 230000006854 communication Effects 0.000 title claims abstract description 44
- 230000004044 response Effects 0.000 claims abstract description 10
- 239000003990 capacitor Substances 0.000 claims description 33
- 239000013078 crystal Substances 0.000 claims description 8
- 230000008878 coupling Effects 0.000 claims description 7
- 238000010168 coupling process Methods 0.000 claims description 7
- 238000005859 coupling reaction Methods 0.000 claims description 7
- 230000004913 activation Effects 0.000 claims 2
- 230000005540 biological transmission Effects 0.000 claims 2
- 230000002463 transducing effect Effects 0.000 claims 1
- 230000001681 protective effect Effects 0.000 abstract description 7
- 239000004065 semiconductor Substances 0.000 description 16
- 238000010586 diagram Methods 0.000 description 5
- 238000010276 construction Methods 0.000 description 4
- 230000009977 dual effect Effects 0.000 description 4
- 239000010907 stover Substances 0.000 description 4
- 230000008859 change Effects 0.000 description 3
- WABPQHHGFIMREM-FTXFMUIASA-N lead-202 Chemical compound [202Pb] WABPQHHGFIMREM-FTXFMUIASA-N 0.000 description 3
- 230000003321 amplification Effects 0.000 description 2
- 230000001419 dependent effect Effects 0.000 description 2
- 230000002401 inhibitory effect Effects 0.000 description 2
- WABPQHHGFIMREM-BKFZFHPZSA-N lead-212 Chemical compound [212Pb] WABPQHHGFIMREM-BKFZFHPZSA-N 0.000 description 2
- 239000000463 material Substances 0.000 description 2
- 238000003199 nucleic acid amplification method Methods 0.000 description 2
- 230000001143 conditioned effect Effects 0.000 description 1
- 229920001971 elastomer Polymers 0.000 description 1
- 230000005672 electromagnetic field Effects 0.000 description 1
- 230000005669 field effect Effects 0.000 description 1
- 230000003116 impacting effect Effects 0.000 description 1
- 229910044991 metal oxide Inorganic materials 0.000 description 1
- 150000004706 metal oxides Chemical class 0.000 description 1
- 230000010355 oscillation Effects 0.000 description 1
- 230000005855 radiation Effects 0.000 description 1
- 239000005060 rubber Substances 0.000 description 1
- 239000004576 sand Substances 0.000 description 1
- 230000008054 signal transmission Effects 0.000 description 1
- 230000011664 signaling Effects 0.000 description 1
- 230000005236 sound signal Effects 0.000 description 1
- 229920003051 synthetic elastomer Polymers 0.000 description 1
- 239000005061 synthetic rubber Substances 0.000 description 1
Classifications
-
- A—HUMAN NECESSITIES
- A42—HEADWEAR
- A42B—HATS; HEAD COVERINGS
- A42B3/00—Helmets; Helmet covers ; Other protective head coverings
- A42B3/04—Parts, details or accessories of helmets
- A42B3/30—Mounting radio sets or communication systems
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B1/00—Details of transmission systems, not covered by a single one of groups H04B3/00 - H04B13/00; Details of transmission systems not characterised by the medium used for transmission
- H04B1/38—Transceivers, i.e. devices in which transmitter and receiver form a structural unit and in which at least one part is used for functions of transmitting and receiving
- H04B1/40—Circuits
- H04B1/44—Transmit/receive switching
- H04B1/46—Transmit/receive switching by voice-frequency signals; by pilot signals
Landscapes
- Engineering & Computer Science (AREA)
- Computer Networks & Wireless Communication (AREA)
- Signal Processing (AREA)
- Transceivers (AREA)
- Transmitters (AREA)
- Mobile Radio Communication Systems (AREA)
Abstract
TWO-WAY VOICE CONTROLLED COMMUNICATION SYSTEM
ABSTRACT OF THE DISCLOSURE
A two-way voice controlled communication system for use with a protective helmet. The communication system includes a transmitting circuit which is normally off, and which is voice actuated, and a receiving circuit which is normally on. The transmitting circuit includes a microphone and an electronicswitch which turfs the transmitting circuit on and the receiving circuit off in response to the presence of an output from the microphone, and turns the transmitting circuit off and the receiving circuit on substantially immediately in response to the absence of a microphone output. Thus the system approximates two-way real-time communication by permitting one user of the system to interrupt the speech of another user of the system. The system is designed primarily for far field communication, that is, omnidirectional communication where the spatial positioning of one communication system relative to a second communication system is essentially independent of the distance between the two systems.
ABSTRACT OF THE DISCLOSURE
A two-way voice controlled communication system for use with a protective helmet. The communication system includes a transmitting circuit which is normally off, and which is voice actuated, and a receiving circuit which is normally on. The transmitting circuit includes a microphone and an electronicswitch which turfs the transmitting circuit on and the receiving circuit off in response to the presence of an output from the microphone, and turns the transmitting circuit off and the receiving circuit on substantially immediately in response to the absence of a microphone output. Thus the system approximates two-way real-time communication by permitting one user of the system to interrupt the speech of another user of the system. The system is designed primarily for far field communication, that is, omnidirectional communication where the spatial positioning of one communication system relative to a second communication system is essentially independent of the distance between the two systems.
Description
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- 1011.005BACKGROUND OF THE INVENTION
:' This invention relates generally to a two-way communication - system of the type which may be utilized with a protective helrnet such as the helmet worn by the military, construction workers, factory workers, fire fighters and motorcyclists. ASore particularly, the present invention relates to an improved two-way communication system which approximates tw~way real time communication.
Two-way communication systems are, of course, well known as exemplified by the United States Patent 3,366,880 to Driver, United States Patent 3,968,435 to Stover and United States Patent 3,2g3,074 to Csicsatka. Of these three prior patents, the Stover patent, of course, relates ~o a two-way communication system for use with a helmet.
There are various problems with the two-way communication systems of the prior art. One of the problems has been the need to manually switch the system between a transmit mode and a receive mode. This has been overcome, in part, by voice controlled systems such as that disclosed in the Csicsatka patent referred to above.
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However, prior to the present invention, even voice-controlled communication systems suffer from severe lirnitations. ~`
For example, when such systems are being utilized, the person initially receiving a communication must wait an inordinate amount of time before responding to the person initially speakingO This is because the systems heretofore developed include a substantial delay in switching frorn the transmitmode to the receive mode. As a consequence of the delay, the person initi~lly listening to the conversation must wait, before commencing a response, otherwise the initial portion of the return cornmunicatlon is not received. Thisresults in a very stilted pattern of communication$ between users of these systems.
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:t 1011.005 As a prac~ical example of this delay, a person initially listening cannot interrupt, even at the end oI a sentence, to warn the person speaking of ~; an imminent danger.
We have discovered that it is possible to approach two-way real time communication, simulating actual speech patterns, by providing a system which substantially immediately switches into the receive mode when the user of the system is not speaking. This switching occurs during time intervals between words, during pauses in speech and at the end of sentences and the like to thus permit immediate responses over the communication system.
Another shortcoming of the prior systems is that exemplified by the aforementioned Stover Patent which is designed for use in the near ~ield.
Systems which are designed to operate in the near field are dependent on the spatial relationship between users of the system, as hereinafter explained, and thus provide a significant limitation on the distance over which these systems may be utilized.
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We have determined that such a limitation is not feasible for a two-way communication system and hence our system is predominately designed for use in the far field region.
Thus the present invention overcomes the heretofore described limitations of the prior art by providing a two-way voice controlled communication system which approximates two-way real time cornmunications and which is designed primarily for use in the far field independent of the spatial relationship between users of the system.
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1011.005 SUMMARY OF THE INVENTION
The present invention is directed to an improved two way communication system which is voice actua~ed and which is normally in a receive mode. In response to the voice of the user, the system switches to the transmit mode and, in the absence of the voice of the user, including during short intervals between words and at the end of sentences, the system substantially imrnediatelyswitches back into a receive mode thus permitting the user of the system to hearany interruptions or responses and thus approximating real $ime two-way communications.
The present invention is furthermore designed primarily for far field operation to thus avoid restrictions on the spatial orientation between users of the present system.
By way of further explanation, the near field is described as that region of the electromagnetic field immediately surrounding the antenna where reactive field predominates. This distance is less than a~ where ~ is defined as the wave length at the transmitting frequency~ In this region, radiation fields predominate and the angular field distribution is dependent upon the distance from the antenna of one such system to the antenna of another such system. This is often referred to as the Fresnel region. Within this region, theangular or spatial orientation between two users of such a system is critical and frequently the signal transmitted by one user cannot be heard by other users of the system purely because of their spatial orientation or location even though they may be a few feet away from the first user of the system.
The far field is that region farther away from the anten~ia where the angular field distribution is essentially independent of the distance from ~he antenna. This is referred to as the Fraunhofer region. In the Fraunhofer region,two users of the system can hear each other regardless of their spatial orientation.
- 1011.005 This becomes of particular importance to ~ire fighters in a building where one fire fighter may be several floors above another fire fighter.
While the distance between them may be only thirty feet, because the two fire fighters are vertically spaced apar~, if a communication systern is operating in the near field region the fire fighters cs)uld not receive the transmitted signals.
whereas there would be no prohlem in receiving such signals if the systems are operated in the far field region.
Thus the present system is designed to primarily operate in the far field or Fraunhofer region contrary to prior art systems such as that disclosed in the aforementioned Stover Patent 3,968,435.
Furthermore, the two-way voice controlled communication system of the present invention is of light weight and rnay be easily contained within a protective helmet.
It is- the primary object of this invention to provide a two-way `~ communication system which overcomes the foregoing limitations and disadvantages and is compact in size and li~ht in weight and readily adapted for mounting upon a protective helmet. `
A further object is to provide a two-way communication system which is normally in a signal receiYing condition but which is automatically conditioned for signal transmission by the voice of the user.
A further object is to provide a comrnunication system of this character which includes an automatic voice activated transmitter not responsive to ambient sound.
A further object is to provide a voice controlled two-way communication system utilizing a ~unnel diode as a phase modulator.
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A further object is to provide a two-way communication system mounted upon a protective helmet where, in one embodiment, a transducer . causes the helmet to vibrate and become an acoustical reproducer or speaker.
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3~3 1011.005 BRIEF DESCE~IPTION OF THE l)RAWIN(;S
The various objects and advantages of the present invention will become apparent upon reading the following detailed description of the inventiontaken in conjunction with the drawings.
In the drawings, wherein like reference numerals identify corresponding components:
Figure 1 is a perspective view of a helmet including the new two way communication system;
Figure ~ is a block diagram of one embodiment of the invention;
Figure 3 is a circuit dia~ram illustrating one embodiment of the invention;
- Figure 4 ls an alternate block diagram of the circuit; and Figure 5 is a diagram of part of the circuit of the present ~` invention.
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DESCRIPTION OF THE PREFERRED EMBODIMENT `
Referring to the drawings which illustrate the preferred embodi- `
ment of the invention, the numeral 10 designates a protecti~e helmet which may be of any desired type such as those worn by firemen, construction or factory workers, military personnel, sand blasters, police, motorcyclists, snowmobilers and sky divers and characterized by a rigid body having protective resilient or cushioning lining 12 and in some cases a chin strap or like secùring means 14.
Upon this helmet is mounted a carrier 16 for the electrical components of the signaling system, which carrier is preferably formed OI resilient sponge rubber or synthetic rubber. A microphone 18 is mounted upon adjustable hinged supporting means 20 carried by an anchor member 22 supported by the helmet and projecting from the protective carrier 16. Except for the microphone and the electrical connections 24 leading thereto, all electricai and electronic components o~ the communication system, including the antenna, may be mounted within and protected by the carrier 16.
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The helmet and carrier construction, and some variations thereof, are described more particularly in U.S. Patent ~oO 4,152,553 issued May 1, 1979.
Figures 2 and 4 are block diagrams of the commu-nication system. In each of Figures 2 and 4, there is illustrated the two-way communication system including the signal transmitting circuitry and the signal receiving circuitry. System which both transmit and receive signals ~ ;
are colr~nonly referred to as transceivers. The signal trans-- 10 mitting portion of the circuitry, in block form, will be explained first~
-~ Microphone 18 is preferably of the noise cancelling type, i.e., the microphone has both sides of its diaphragm exposed so that planar waves such as ambient noise are can-celled out by their impacting against both sides of the micro-phone. Spherical waves, such as those occasioned by the microphone diaphragm being close to the mouth of the person speaking, cause the diaphragm to vibrate and thus transmit signals along lead 24. l~oise cancelling microphones are, of ` 20 course, conventional.
The microphone 18 is connected to a voice responsive ~ ~--~ amplifier 30 having three outputs. One output of the amplifier is connected by a lead 32 to a local osci3Llator 34. A first -;
output from the local oscillator is connected by lead 36 to a tunnel diode 38 with the opposite side of the tunnel diode connected to system ground at 40. The output of the local oscillator 34 is also coupled across a capacitor and then via ;~ lead 42 to a first amplifier 44 and then a second amplifier 46 connected in series with the output of the first amplifier.
Each of the components 30, 34, 38, 44 and 46 is connected to ~ a common ground 40. The output from the second amplifier 46 `
: is connected via lead 48 to a transmitting antenna 50.
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1011.005A second input to the local oscillator 34 is connected by lead 52 -from the collector of a transistor 5l~ which ~ransistor has its emitter coupled to a positive source of potential such as a battery 56.
The secon~ of the three outputs from the amplifier 30 is connected along lead 58 to the base of the transistor 54. A signal on lead 58 tothe base of transistor 54 enables transistor 54 to be conducting and thus power flows from the battery 56 through tram;is~or 54 to each of the ampllfiers and tothe osdllator.
The signal receiving portion of the circuit of the present invention will now be explained. The incoming communication signal is received by an antenna 86 and the incoming signals from the antenna 86 are fed to a preamplifier 84 which also receives an input from the battery 56 through transistor 62 and along lead 66. As is well known, although ~wo antennas 50 and 86 are described, a single antenna may be utilized for both transmitting and recei~ing signals.
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The third output from the ampiifier 30 of the transmitter circuit is coupled along lead 60 to ~he base of transistor 62. Transistor 62 has a positive source of potential connected to its emitter along lead 64. A signal on lead 60 to the base of transistor 62 enables t!ansistor 62 to be conducting and thus power flows from the battery 56 along lead 64~ through transistor 62 to the signal receiving circuit along lead 66.
The battery or source of potential 56 thus provides power to a first oscillator 94, the output of which may be fed through a transistor (shown in Figure 2) and is fed to a iirst mixer 78~ The ou~put of the preamplifier 84 n aybe fed through a transistor tFigure 2) is also connected to the first mixer 78. The output of the first mixer 78 is connected to a second mixer 74.
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1011.005As is conventional with receivers of this type, a second local oscillator 72 is provided and this oscillator also receives power from the battery 56 through transistor 62 and lead 6S. The output of this local oscilla~or 72 is also fed to the second mixer 74.
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The output of the second mixer 74 is fed to an FM deteceor 102 which is also powered by the battery 56 through transistor 62. For the purposes of providing automatic gain control, another input to ~he preamplifier 84 is connected along lead 104 from the FM detector 102. The output of the FM
detector 102 is coupled alon~ lead 105 to an audio amplifier 106 and the output of audio amplifier 106 is connected to a transducer or sound reproducing unit 108. Each of the components 84, 72, 102 and 106 is connected with a common system ground designated 68.
As is conventional, system ~round 68 and system ground 40 are one and the same and are at a negatiYe potential relative to the battery 56. Also as is well understood by circuit designers, the relative polarity of the battery and the system ground may be reversed with suitable changing of the biasing of the components and changing from NPN to PNP transistors.
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Having thus described the transmitting and receiving circuits in block diagram form3 re~erence should now be had to Figure 3 for a detailed ;" explanation of the circuit of the present system. ~-.
Referring to Figure 3, the local oscillator 34 includes a coupling ~`
transformer 110 which receives the signal along lead 32 from thç first output ofthe voice responsive amplifier 30. One side of the secondary o~ transformer 110 `~is connected by capacitor 112 to ground. The other side of the secondary is `~connected through a resistor 114 to the tunnel diode 38. One side of the primary - coil of the coupling transformer 110 is connected throu~h capacitor 116 to lead .:, .i .
52 while the other side Is directly connec~ed to lead 52. The primary of the coil :~
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1011.005 is tapped to provide a signal to the collector of transistor 118. The emitter of transistor 118 is connected through the parallel combination of a capacitor 120 and a resistor 122 to ground. The base of transistor 118 is r:onnected through acrystal element 124 to ground. A capacitor 126 is connected between lead 52 and ground, on the primary side o~ the coil and a voltage divider, comprising resistors 130 and 132 is also connected between lead 52 and groundr The junctionof these resistors, is also connected via lead 128 to the base of transistor 118.
This completes the description of the oscillator circuit 34. As may be appreciated, many changes in the details of the oscillator may be made by circuit designers.
The output of the oscillator circuit 34 is coupled to one side of the tunnel diode 38 via lead 36 as prevlously described. The output from the local oscillator is also coupled along lead 36 across a capacitor l34 and then through a lead 42 to the first amplifier 44 which constitutes a multiplier circuit.
In this multiplier circuit lead 4~ is connected to the base of a transistor 136 which transistor has its collector connected to lead 52 through atank circuit in parallel branches; one branch includes an inductance 138 and theother branch includes a pair of capacitors 140. Transistor 136 has its emit$er connected to ground through by parallel branches includin~ a resistor 142 in onebranch and a capacitor 144 in the other branch. In the amplifier circuit 44, thetwo capacitors 140 provide capacitive coupling as follows. A lead 146 is connected to the junction between the capacitors and resistors 150 and 152 provide a voltage divider or biasing between leads 52 and ground. The lead 146 is , coupled to the junction of these two resistors 150 and 152 and a lead 148 is identified as this junction. The lead 52 and ground are also capacitlvely ` connected along lead 154 and a capacitor 156. A lead 158 from the junction of the resistors 150 and 152 is connected to the base of a transistor 160. The collector of transistor 160 is coupled through a parallel circuit to the lead 52. ~
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. . , ; . " , . ~, 1011.005 Specifically, ~his parallel circui~ includes, in one branch, an inductance 162 and, in the other branch, a pair of capacitors 164 to also provide capacitive coupling.
The emitter of the transistor 160 is coupled through lead 166 to ground.
Again to provide capacitive coupling, the junction of capacitors - 164 is defined as lead 168. This lead is also connected to the junction of a biasing or voltage divider network comprising a pair of resistors 172 and 174 having lead 170 de~ined as the junction between the two resistors. The two resistors are connected between ~round and lead 52 and define the input to the second amplifier 46.
A lead 176, connected ~o the junc~ion 17û of resistors 172 and 174, is connected to the base of a transis~or 178. The collector of transistor 178 is connected to lead 52 through a tanlc circuit in which capacitor 180 and inductance 182 are located in parallel branches. The transmi~tin~ antenna 50 is connected to a tap on the inductance 182 by the lead 4~. The emitter of transistor 178 is cormected to ground by a parallel combination of a resistor 184 and a capacitor 186. The common ground for components of the transmitting clrcuit is shown at 4i0. This concludes the detailed circult description of the transmitting portion of the circuit. As may be seen, each of the transistors has its collector coupled through transistor 54 to the source of potential 56. Thus, as ` may be appreciated, when transistor 54 is non-conducting there will be no output : signal from the transmittmg antenna because none of ~he transistors 118, 136, 160 or 178 will be enabled.
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"~ The receiving portion of the circuit will now be explained.
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`, The incoming signal from the antenna 86 is fed to the prearnplifier 84 and specifically to the tap of an inductance 248. The prearnplifier circuit 84 ~;
includes the parallel combination of the inductance 248 and a capacitor 2S0. One junction between these elements is identi$ied as lead 202 which is the system `ground and the other junction between these elements is identified as lead 244.
Lead 244 is coupled through a capacitor 24~ to one gate of a dual gate met I
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~ii oxide semi-conductor 82.
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1011.005 Power from the battery 56 is coupled via lead 66 and throu~h switchi~g transistor 62 and across a voltage divider of resistors 252 and 254 tolead 202 ~ground). The junction of these two resistors is also connected to the same gate of semi-conductor 82. To provide the automatic gain control as previously described, one output from the FM detector 102 is coupled along lead 104 back to the preamplifier circuit 84 and more specifically across a resistor 258 to the other gate of the semi-conduc~or 82. The semi-conductor 82 is connected to the source of power from lead 6~ through the parallel combination of an inductance 23~ and a capacitance 240. Semi-conductor 82 is connected by lead 242 to the lead 202 which is the common ground 68.
The preamplifier circuit 84 is connected to a first mixer 78 by lead 81 and a capacitor 236 from the output of semi-conductor 82. The first mixer circuit includes resistors 208 and 210 connected at their junction 206 to capacitor 236, with resistors 208 and 210 being connected between lead 66 (power) and lead 202 (ground), respectively. The junction 206 between the ` resistors 208 and 210 is also connected to one gate of a second dual gate metal oxide semi-conductor 91. The other gate of this semi-conductor receives a signal` from the oscillator 94 along lead 212. The semi-conductor 91 is connected to ~round through the parallel combination of a resistor 198 and a capacitor 200.
Semi-conductor 91 is also connected to the power source by lead 80 and then through the parallel circuit including the primary coil of transformer 190, in one branch, and a capacitor 194 in the other branch. Power is supplied to a tap on the primary coil. The secondary coil of the transformer 190 is connected by lead76 to the second mixer 74 thus providing the output to the second rnixer.
-- ~irst local oscillator circuit 94 is connected to the battery by lead 66 and transistor 62, and through lead 232 and a capacitor 234 to ground 68. Theoscillator includes a transistor 92 having its base connected to the junction 224 of resistors 226 and 22~ which resistors have their opposite sides connected to .~
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1011.005 ground and the power supply, respectively. The emi~ter of transistor 92 is also connected to the common ground through the parallel combina~ion of a resistor 218 and a capacitor 220. Also coupled to the base o~ transistor 92 is a crystal 230 which is coupled in parallel across resistor 226 to ground. The collector of transistor 92 is connected by three parallel branches to the power supply. A coil 214 is in the first of these branches while capacitors 216 are in each o~ the second and third branches. The output of the local oscillator is tapped from coil 214 and connected by lead 212 to the second gate of the semi-conductor 91 of the first mixer 78.
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A second local oscillator 72, also connected to the battery via lead 66, is controlled by a crystal 188 and is coupled to a second mixer 74.
Second mixer 74 is connected by lead 76 to the output of the first mixer 78. The -output of the second mixer 74 is fed through amplifier 98 and tuning coil 100 to the FM detector 102 which also provides automatic gain control via line 104 back . --to the preamplifier 84.
The output of the FM detector 102 is connected on lead 105 to an audio amplifier 106 whose output is delivered to ~he transducer or speaker element 108 of the receiving set.
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The semi-conductors ~2 and 91 are preferably of the dual gate MOS field effect transistor type. The microphone 18 is of the noise cancelling type which is not activated by ambient sound and is responsive only to the voice of the wearer of the helmet. For this purpose the microphone is mounted by the adjustable support 20 for adjustment to a position close ~o ~he mouth of the wearer of the helmet 10.
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1011.005 In an optional embodiment, the speaker, transducer or receiver 108 may include a vibratory element responsive to a received signal and contacting the material of the helrnet 10 in such relation that the material of the helmet is vibrated and is comparable to the diaphra~m of a conventional speaker.
Thus any received signals are readily heard and distinguished by the wearer of the helmet otherwise a conventional speaker may be used.
The antennas 50 and 86 are elements which may be housed within ` the carrier 16 in any suitable or convenient fashion. The electrical and ` electronic components of the circuit are encapsulated so as to be compact and to fit within cavities in the carrier 16. The carrier is also provided with cavities `~ within which the operating batteries may be mounted.
The tunnel diode 38 is employed9 as by control of the bias (audio . . : '.
signal), to change switching times at radio frequency rates to produce phase modulation. --.. ' ' ' The two-way communication system of the present imention is - normally in the receive mode and is switched into the transmit mode in response ` to the voice of the user. As previously described and as hereinafter explained in greater detail, the system will promptly switch back into a receive mode during .. ~.
pauses in the speech of the user to thus permit a listener to break in on a ; ' conversation and thus provide real tirne two-way communication.
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Having ~hus described the circuit details, the operation will now ~` be explained. The amplifier 30 has a gain control input, as will be described, and has a voltage comparator on its output. The voltage comparàtor changes the ;.
i` state of an internal fli~flop or multivibrator circuit, as hereinafter described, `~ which switches and controls the transmitter and receiver.
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1011.005Because the microphone 18 is of the noise cancelling type which is not responsive to ambient sound, the amplifier 3û and associated circuit elements are normally off or not active, and the transistor 62 is conducting to provide power to the receiver including the amplifier 84, the local oscillators 72 and 94, the mixers 74 and 78, the detector 102, the amplifier 106 and the transducer or speaker element 108~ While transistor 62 is conduc~ing the transistor 54 is not active or functioning and the transmitting section of the circuit is disabled or not in operation. The slgnals received at the receiving antenna 86 feed the transistor (semiconductor) 82 whvse gain is cont`rolled by the FM detector 102. The FM
~- detector 102 contains a capacitor and rectifier which provide a direct current signal proportional to ~he audio level fed thereto at the tuning coil lûO. The output of the transistor (semiconductc>r) 82 feeds the transistor (semiconductor) 91 whose function is to be a first detector. The other signal to the transistor (semiconductor) ~1 is derived from a constant frequency oscillator which is controlled by the crystal 230.
, The output of the transistor (semiconductor) 91 is the difference between that derived from the crystal controlled oscillator 94 and the incoming radio frequency. The output of transistor (semiconductor) 91 is multiplied by a second local oscillator 72 controlled by crystal 188 and produces a difference frequency at 450 kilohertz which is amplified a~ the intermediate frequency amplifier 98.
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`In the preferred form, various elements including the amplifier 30, the local oscillator 72, the crystal 188, the mixer 74, and the intermediate frequency amplifier 98, are cQntained in a chip identified as IC MOA 902. The output of the intermediate frequency amplifier 98 passes through the tuning coil100 to the FM detector 102. The FM detector 102 is contained in a second chip which also contains the amplifier 106 fed by that FM detector and passes the signal to the speaker or transducer 108 which vibrates the helmet. The transducer of the speaker 108 may be either conventional or, if vibrating, of the piezoelectric or the electromechanical type.
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1011.005 Upon energization of the microphone 18, the amplifier 30 is activated ~o energize the transmi~ter circuit by turning on the transistor 54, and simultaneously deactivatin~ the transistor 62 to shut off the receiver. A chip containing the amplifier 30 also includes a fli~flop operating an off-on signal to turn on either transistor 54 or 6~.
The amplified audio signal derived from the microphone 18 is fed through line 32 to the local oscillator 34 and the tunnel diode 38 to change thebias or switch point. The outpu~ of the tunnel diode 38 passes through capacitor134 to amplifier 44 loaded with a tank circ~lit and containing transistor 136 and its associated components. This tank circuit is a multiple of the local oscillation frequency, constituting a multiplier circuit by capacitive coupling. The second amplifier 46, which includes the transistor 178 and associated components3 further boosts the power and cooperates with the amplifier 44 ~o remove unwanted harmonics of the signal delivered to the transmitting antenna 50.
To further illustrate the electronic switchin~ heretofore described with respect to changing into the transmit mode, in response to a signal caused ~ by the voice of the user of the system, and to further explain the substantially "~ immediate switching back into receive mode during pauses in speech to permit real time two-way communication, reference shol~ld now be had to Figure ~.
Figure 5 illustrates, in greater detail, the amplifier circuit 30 with its internal gain control input, voltage comparator and internal flip-flop as previously . ~ mentioned. In understanding Figure 5, it should be remembered that the 5~ objective of this switching circuit is that transistor 6~ should be always enabled, or on, by virtue of a signal on lead 60 except when the user of the system speaks and similarly, transistor 54 should be disabled, or off, by virtue of a low signal or the absence of a signal on lead ~8 except when the user of the system speaks.
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1011.005 The incoming signal from the noise cancellin~ microphone 18 is fed to an automa~ic gain con~rol amplifier 270. This automatic gain control amplifier is established to provide virtually constant audio output regardless of the intensity of the speaking voice, within the normal ranges of the gain control.
This, of course, is conventional. One output from the automatic gain control ampllfier 270 is coupled across a capacitor 271 to the audio output 32 and then to the oscillator 34 and tunnel diode 38 as previously described. The output from the automa~ic ~ain control amplifier 270 is also coupled to a second amplification stage within the arnplifier 30.
Specifically, the output from the automatic gain control amplifier 270 is coupled to the base of a first transistor 272 which has its emitter coupled to system ground and its collector coupled through a resistor 273 to a source ofpositive potential. The collector output of the first transistor 272 serves as the r base in~ut to a second transistor 274 which has its collector coupled ~o the ~" source of positive potential and its emitter coupled through series resistors 275 and 276, respectively, to the system ground. The junction between resistors 275 `~ and 276 is coupled back to the base of transistor 27~.
~ The output from the gain control amplifier 270 is also coupled ;~; across capacitor 271 to the base of a third transis~or 276. The emitter of ~ransistor ~74 is also coupled to the base of transistor 276. lhe collector of transistor 276 is connected to the source of positive potential and the ernitter of 'i transistor 276 is coupled across the parallel circuit of resistor 277 and capacitor 278 to ground.
The output from the transistor 276 is taken Erorn its emitter to the base of the internal fli~flop which controls the transmitter and receiver.
`~ The internal flip-flop includes a first transistor 280 and a second transistor 282 having their emitters interconnected and coupled to ~round. The collector of transistor 280 receives a voltage from the power supply through a resistor 283 .
~, 1011.005 and has its collector coupled as lead 58 ~o the base of transistor 54. Similarly, transistor 282 has its collector coupled through a resistor 284 ~o the power supply and also has its collector coupled, as lead 60, to the base of transistor 62. The internal flip-flop circuit also includes a voltage divider coupled between the power supply and grour~d including resisto~s 285 and 286 having the junction - therebetween coupled to the base of transistor 282.
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The operation of the circuit will now be explained. As previously mentioned, the automatic ~ain control amplifier 270 operates in a conventional fashion to provide a substantially constant audio output on lead 32. Transistors272 and 274 function as conventional amplifiers9 to provide amplification of thesignal and transistor 276, when conducting, charges capacitor 278 and functions as a clipping àmplifier to control the turning on and turning off of transistors 280 and 282. A biasing voltage is provided through resistor 285 and the power supplyto the base of transistor 282 such that transistor 282 is normally on, thus enabling the receive mode by presenting a high signal from its collector to leadi~` 60, and transistor 280 is normally off thus providing a low signal from its , collector along lead 58 and inhibiting transistor 54.
, i~ When the user of the system wishes to speak, the voice is picked up by the microphone 18 and the automatic gain control amplifier provides a signal which is amplified by the transistor 272 and 274 to the base of transistor 276. Transistor 276 conducts and as soon as capacitor 278 charges to a point where the voltage at the base transistor 280 exceeds the bias voltage at the base of transistor 282, the two transistors 2~0 and 282 fli~flop or change their respective states so that transistor 280 conducts and transistor 282 is non-conducting. Transistor 280 conducting provides a signal on line 58 to enable transistor 54 and thus enable the transmitting portion of the circuit~
Simultaneously, transistor 282 is disabled thus removing the enabling signal on lead 60 to transistor 62 to the receive portion of the circuit and thus inhibiting the receive portion of the circuit.
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1011.005 As soon as ~he user of the sys~em stops speaking, even during a brief pause, the signal is removed from the base of the transistor 276 and the ~ . .
signal at the base of ~ransistor 280 is discharged through the RC circuit comprising the resistor 277 and the capacitor 27~. As soon as ~he signal at the base of transistor 280 drops below the biasing voltage a~ the base of the transistor 282, the two transistors fli~flop again with transistor 280 becoming non-conducting, thus disabling the transistor 54, while transistor 282 becomes conducting, thus enabling the transistor 62. This permits a breal< or an interruption in the communication by permitting the person initially listening to interrupt during pauses in speech. We have determined for effective real-time two-way communication the time constant of the RC circuit should be such that the signal at the base of transistor 280 drops to a value below the bias at the base of transistor 282 within the ranE~e of three to ten miliseconds. This provides a sufficiently fast switching to permit interruptions in speech during normal pauses in speech to provide effective real-time two-way communication approaching that which is provided by dual channel systems such as telephony.
Thus the two transistors 280 and 282 function as a flip-flop and the transistors also function as a voltage comparator since transis~or 280 is conducting only when its base voltage exceeds the constant base voltage of transistor 282. Furthermore these transistors 2~0 and 282, in conjunction with resistor 277 and capacitor 278 function as an astable multivibrator by returningto the preferre~ state (transistor 282 on) a desired time interval after removal of the signal from transistor 276. The time interval, of course, is based on the time constant of the RC circuit.
This two-way communication system is crystal controlled, constituting a transceiver or transmitter and a receiver in a single package, and permits operation of the unit within an assigned frequency range.
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1011.005With respect to far field operation, the output or transmitting -frequency is selected in the range of 50 megahertz and thus the wavelength is about 18 feet. Since the near field is defined as less than ~ it appears that at a distance between systems in excess of three feet, the systems will be operating in the far field region.
While the preferred embodiment of the invention has been illustrated and described, it will be understood tha~ changes in the construction may be made within the scope of the appended claims wi~hout departing from the spirit of the invention.
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- 1011.005BACKGROUND OF THE INVENTION
:' This invention relates generally to a two-way communication - system of the type which may be utilized with a protective helrnet such as the helmet worn by the military, construction workers, factory workers, fire fighters and motorcyclists. ASore particularly, the present invention relates to an improved two-way communication system which approximates tw~way real time communication.
Two-way communication systems are, of course, well known as exemplified by the United States Patent 3,366,880 to Driver, United States Patent 3,968,435 to Stover and United States Patent 3,2g3,074 to Csicsatka. Of these three prior patents, the Stover patent, of course, relates ~o a two-way communication system for use with a helmet.
There are various problems with the two-way communication systems of the prior art. One of the problems has been the need to manually switch the system between a transmit mode and a receive mode. This has been overcome, in part, by voice controlled systems such as that disclosed in the Csicsatka patent referred to above.
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However, prior to the present invention, even voice-controlled communication systems suffer from severe lirnitations. ~`
For example, when such systems are being utilized, the person initially receiving a communication must wait an inordinate amount of time before responding to the person initially speakingO This is because the systems heretofore developed include a substantial delay in switching frorn the transmitmode to the receive mode. As a consequence of the delay, the person initi~lly listening to the conversation must wait, before commencing a response, otherwise the initial portion of the return cornmunicatlon is not received. Thisresults in a very stilted pattern of communication$ between users of these systems.
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:t 1011.005 As a prac~ical example of this delay, a person initially listening cannot interrupt, even at the end oI a sentence, to warn the person speaking of ~; an imminent danger.
We have discovered that it is possible to approach two-way real time communication, simulating actual speech patterns, by providing a system which substantially immediately switches into the receive mode when the user of the system is not speaking. This switching occurs during time intervals between words, during pauses in speech and at the end of sentences and the like to thus permit immediate responses over the communication system.
Another shortcoming of the prior systems is that exemplified by the aforementioned Stover Patent which is designed for use in the near ~ield.
Systems which are designed to operate in the near field are dependent on the spatial relationship between users of the system, as hereinafter explained, and thus provide a significant limitation on the distance over which these systems may be utilized.
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We have determined that such a limitation is not feasible for a two-way communication system and hence our system is predominately designed for use in the far field region.
Thus the present invention overcomes the heretofore described limitations of the prior art by providing a two-way voice controlled communication system which approximates two-way real time cornmunications and which is designed primarily for use in the far field independent of the spatial relationship between users of the system.
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1011.005 SUMMARY OF THE INVENTION
The present invention is directed to an improved two way communication system which is voice actua~ed and which is normally in a receive mode. In response to the voice of the user, the system switches to the transmit mode and, in the absence of the voice of the user, including during short intervals between words and at the end of sentences, the system substantially imrnediatelyswitches back into a receive mode thus permitting the user of the system to hearany interruptions or responses and thus approximating real $ime two-way communications.
The present invention is furthermore designed primarily for far field operation to thus avoid restrictions on the spatial orientation between users of the present system.
By way of further explanation, the near field is described as that region of the electromagnetic field immediately surrounding the antenna where reactive field predominates. This distance is less than a~ where ~ is defined as the wave length at the transmitting frequency~ In this region, radiation fields predominate and the angular field distribution is dependent upon the distance from the antenna of one such system to the antenna of another such system. This is often referred to as the Fresnel region. Within this region, theangular or spatial orientation between two users of such a system is critical and frequently the signal transmitted by one user cannot be heard by other users of the system purely because of their spatial orientation or location even though they may be a few feet away from the first user of the system.
The far field is that region farther away from the anten~ia where the angular field distribution is essentially independent of the distance from ~he antenna. This is referred to as the Fraunhofer region. In the Fraunhofer region,two users of the system can hear each other regardless of their spatial orientation.
- 1011.005 This becomes of particular importance to ~ire fighters in a building where one fire fighter may be several floors above another fire fighter.
While the distance between them may be only thirty feet, because the two fire fighters are vertically spaced apar~, if a communication systern is operating in the near field region the fire fighters cs)uld not receive the transmitted signals.
whereas there would be no prohlem in receiving such signals if the systems are operated in the far field region.
Thus the present system is designed to primarily operate in the far field or Fraunhofer region contrary to prior art systems such as that disclosed in the aforementioned Stover Patent 3,968,435.
Furthermore, the two-way voice controlled communication system of the present invention is of light weight and rnay be easily contained within a protective helmet.
It is- the primary object of this invention to provide a two-way `~ communication system which overcomes the foregoing limitations and disadvantages and is compact in size and li~ht in weight and readily adapted for mounting upon a protective helmet. `
A further object is to provide a two-way communication system which is normally in a signal receiYing condition but which is automatically conditioned for signal transmission by the voice of the user.
A further object is to provide a comrnunication system of this character which includes an automatic voice activated transmitter not responsive to ambient sound.
A further object is to provide a voice controlled two-way communication system utilizing a ~unnel diode as a phase modulator.
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A further object is to provide a two-way communication system mounted upon a protective helmet where, in one embodiment, a transducer . causes the helmet to vibrate and become an acoustical reproducer or speaker.
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3~3 1011.005 BRIEF DESCE~IPTION OF THE l)RAWIN(;S
The various objects and advantages of the present invention will become apparent upon reading the following detailed description of the inventiontaken in conjunction with the drawings.
In the drawings, wherein like reference numerals identify corresponding components:
Figure 1 is a perspective view of a helmet including the new two way communication system;
Figure ~ is a block diagram of one embodiment of the invention;
Figure 3 is a circuit dia~ram illustrating one embodiment of the invention;
- Figure 4 ls an alternate block diagram of the circuit; and Figure 5 is a diagram of part of the circuit of the present ~` invention.
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DESCRIPTION OF THE PREFERRED EMBODIMENT `
Referring to the drawings which illustrate the preferred embodi- `
ment of the invention, the numeral 10 designates a protecti~e helmet which may be of any desired type such as those worn by firemen, construction or factory workers, military personnel, sand blasters, police, motorcyclists, snowmobilers and sky divers and characterized by a rigid body having protective resilient or cushioning lining 12 and in some cases a chin strap or like secùring means 14.
Upon this helmet is mounted a carrier 16 for the electrical components of the signaling system, which carrier is preferably formed OI resilient sponge rubber or synthetic rubber. A microphone 18 is mounted upon adjustable hinged supporting means 20 carried by an anchor member 22 supported by the helmet and projecting from the protective carrier 16. Except for the microphone and the electrical connections 24 leading thereto, all electricai and electronic components o~ the communication system, including the antenna, may be mounted within and protected by the carrier 16.
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The helmet and carrier construction, and some variations thereof, are described more particularly in U.S. Patent ~oO 4,152,553 issued May 1, 1979.
Figures 2 and 4 are block diagrams of the commu-nication system. In each of Figures 2 and 4, there is illustrated the two-way communication system including the signal transmitting circuitry and the signal receiving circuitry. System which both transmit and receive signals ~ ;
are colr~nonly referred to as transceivers. The signal trans-- 10 mitting portion of the circuitry, in block form, will be explained first~
-~ Microphone 18 is preferably of the noise cancelling type, i.e., the microphone has both sides of its diaphragm exposed so that planar waves such as ambient noise are can-celled out by their impacting against both sides of the micro-phone. Spherical waves, such as those occasioned by the microphone diaphragm being close to the mouth of the person speaking, cause the diaphragm to vibrate and thus transmit signals along lead 24. l~oise cancelling microphones are, of ` 20 course, conventional.
The microphone 18 is connected to a voice responsive ~ ~--~ amplifier 30 having three outputs. One output of the amplifier is connected by a lead 32 to a local osci3Llator 34. A first -;
output from the local oscillator is connected by lead 36 to a tunnel diode 38 with the opposite side of the tunnel diode connected to system ground at 40. The output of the local oscillator 34 is also coupled across a capacitor and then via ;~ lead 42 to a first amplifier 44 and then a second amplifier 46 connected in series with the output of the first amplifier.
Each of the components 30, 34, 38, 44 and 46 is connected to ~ a common ground 40. The output from the second amplifier 46 `
: is connected via lead 48 to a transmitting antenna 50.
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1011.005A second input to the local oscillator 34 is connected by lead 52 -from the collector of a transistor 5l~ which ~ransistor has its emitter coupled to a positive source of potential such as a battery 56.
The secon~ of the three outputs from the amplifier 30 is connected along lead 58 to the base of the transistor 54. A signal on lead 58 tothe base of transistor 54 enables transistor 54 to be conducting and thus power flows from the battery 56 through tram;is~or 54 to each of the ampllfiers and tothe osdllator.
The signal receiving portion of the circuit of the present invention will now be explained. The incoming communication signal is received by an antenna 86 and the incoming signals from the antenna 86 are fed to a preamplifier 84 which also receives an input from the battery 56 through transistor 62 and along lead 66. As is well known, although ~wo antennas 50 and 86 are described, a single antenna may be utilized for both transmitting and recei~ing signals.
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The third output from the ampiifier 30 of the transmitter circuit is coupled along lead 60 to ~he base of transistor 62. Transistor 62 has a positive source of potential connected to its emitter along lead 64. A signal on lead 60 to the base of transistor 62 enables t!ansistor 62 to be conducting and thus power flows from the battery 56 along lead 64~ through transistor 62 to the signal receiving circuit along lead 66.
The battery or source of potential 56 thus provides power to a first oscillator 94, the output of which may be fed through a transistor (shown in Figure 2) and is fed to a iirst mixer 78~ The ou~put of the preamplifier 84 n aybe fed through a transistor tFigure 2) is also connected to the first mixer 78. The output of the first mixer 78 is connected to a second mixer 74.
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1011.005As is conventional with receivers of this type, a second local oscillator 72 is provided and this oscillator also receives power from the battery 56 through transistor 62 and lead 6S. The output of this local oscilla~or 72 is also fed to the second mixer 74.
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The output of the second mixer 74 is fed to an FM deteceor 102 which is also powered by the battery 56 through transistor 62. For the purposes of providing automatic gain control, another input to ~he preamplifier 84 is connected along lead 104 from the FM detector 102. The output of the FM
detector 102 is coupled alon~ lead 105 to an audio amplifier 106 and the output of audio amplifier 106 is connected to a transducer or sound reproducing unit 108. Each of the components 84, 72, 102 and 106 is connected with a common system ground designated 68.
As is conventional, system ~round 68 and system ground 40 are one and the same and are at a negatiYe potential relative to the battery 56. Also as is well understood by circuit designers, the relative polarity of the battery and the system ground may be reversed with suitable changing of the biasing of the components and changing from NPN to PNP transistors.
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Having thus described the transmitting and receiving circuits in block diagram form3 re~erence should now be had to Figure 3 for a detailed ;" explanation of the circuit of the present system. ~-.
Referring to Figure 3, the local oscillator 34 includes a coupling ~`
transformer 110 which receives the signal along lead 32 from thç first output ofthe voice responsive amplifier 30. One side of the secondary o~ transformer 110 `~is connected by capacitor 112 to ground. The other side of the secondary is `~connected through a resistor 114 to the tunnel diode 38. One side of the primary - coil of the coupling transformer 110 is connected throu~h capacitor 116 to lead .:, .i .
52 while the other side Is directly connec~ed to lead 52. The primary of the coil :~
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1011.005 is tapped to provide a signal to the collector of transistor 118. The emitter of transistor 118 is connected through the parallel combination of a capacitor 120 and a resistor 122 to ground. The base of transistor 118 is r:onnected through acrystal element 124 to ground. A capacitor 126 is connected between lead 52 and ground, on the primary side o~ the coil and a voltage divider, comprising resistors 130 and 132 is also connected between lead 52 and groundr The junctionof these resistors, is also connected via lead 128 to the base of transistor 118.
This completes the description of the oscillator circuit 34. As may be appreciated, many changes in the details of the oscillator may be made by circuit designers.
The output of the oscillator circuit 34 is coupled to one side of the tunnel diode 38 via lead 36 as prevlously described. The output from the local oscillator is also coupled along lead 36 across a capacitor l34 and then through a lead 42 to the first amplifier 44 which constitutes a multiplier circuit.
In this multiplier circuit lead 4~ is connected to the base of a transistor 136 which transistor has its collector connected to lead 52 through atank circuit in parallel branches; one branch includes an inductance 138 and theother branch includes a pair of capacitors 140. Transistor 136 has its emit$er connected to ground through by parallel branches includin~ a resistor 142 in onebranch and a capacitor 144 in the other branch. In the amplifier circuit 44, thetwo capacitors 140 provide capacitive coupling as follows. A lead 146 is connected to the junction between the capacitors and resistors 150 and 152 provide a voltage divider or biasing between leads 52 and ground. The lead 146 is , coupled to the junction of these two resistors 150 and 152 and a lead 148 is identified as this junction. The lead 52 and ground are also capacitlvely ` connected along lead 154 and a capacitor 156. A lead 158 from the junction of the resistors 150 and 152 is connected to the base of a transistor 160. The collector of transistor 160 is coupled through a parallel circuit to the lead 52. ~
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. . , ; . " , . ~, 1011.005 Specifically, ~his parallel circui~ includes, in one branch, an inductance 162 and, in the other branch, a pair of capacitors 164 to also provide capacitive coupling.
The emitter of the transistor 160 is coupled through lead 166 to ground.
Again to provide capacitive coupling, the junction of capacitors - 164 is defined as lead 168. This lead is also connected to the junction of a biasing or voltage divider network comprising a pair of resistors 172 and 174 having lead 170 de~ined as the junction between the two resistors. The two resistors are connected between ~round and lead 52 and define the input to the second amplifier 46.
A lead 176, connected ~o the junc~ion 17û of resistors 172 and 174, is connected to the base of a transis~or 178. The collector of transistor 178 is connected to lead 52 through a tanlc circuit in which capacitor 180 and inductance 182 are located in parallel branches. The transmi~tin~ antenna 50 is connected to a tap on the inductance 182 by the lead 4~. The emitter of transistor 178 is cormected to ground by a parallel combination of a resistor 184 and a capacitor 186. The common ground for components of the transmitting clrcuit is shown at 4i0. This concludes the detailed circult description of the transmitting portion of the circuit. As may be seen, each of the transistors has its collector coupled through transistor 54 to the source of potential 56. Thus, as ` may be appreciated, when transistor 54 is non-conducting there will be no output : signal from the transmittmg antenna because none of ~he transistors 118, 136, 160 or 178 will be enabled.
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"~ The receiving portion of the circuit will now be explained.
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`, The incoming signal from the antenna 86 is fed to the prearnplifier 84 and specifically to the tap of an inductance 248. The prearnplifier circuit 84 ~;
includes the parallel combination of the inductance 248 and a capacitor 2S0. One junction between these elements is identi$ied as lead 202 which is the system `ground and the other junction between these elements is identified as lead 244.
Lead 244 is coupled through a capacitor 24~ to one gate of a dual gate met I
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~ii oxide semi-conductor 82.
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1011.005 Power from the battery 56 is coupled via lead 66 and throu~h switchi~g transistor 62 and across a voltage divider of resistors 252 and 254 tolead 202 ~ground). The junction of these two resistors is also connected to the same gate of semi-conductor 82. To provide the automatic gain control as previously described, one output from the FM detector 102 is coupled along lead 104 back to the preamplifier circuit 84 and more specifically across a resistor 258 to the other gate of the semi-conduc~or 82. The semi-conductor 82 is connected to the source of power from lead 6~ through the parallel combination of an inductance 23~ and a capacitance 240. Semi-conductor 82 is connected by lead 242 to the lead 202 which is the common ground 68.
The preamplifier circuit 84 is connected to a first mixer 78 by lead 81 and a capacitor 236 from the output of semi-conductor 82. The first mixer circuit includes resistors 208 and 210 connected at their junction 206 to capacitor 236, with resistors 208 and 210 being connected between lead 66 (power) and lead 202 (ground), respectively. The junction 206 between the ` resistors 208 and 210 is also connected to one gate of a second dual gate metal oxide semi-conductor 91. The other gate of this semi-conductor receives a signal` from the oscillator 94 along lead 212. The semi-conductor 91 is connected to ~round through the parallel combination of a resistor 198 and a capacitor 200.
Semi-conductor 91 is also connected to the power source by lead 80 and then through the parallel circuit including the primary coil of transformer 190, in one branch, and a capacitor 194 in the other branch. Power is supplied to a tap on the primary coil. The secondary coil of the transformer 190 is connected by lead76 to the second mixer 74 thus providing the output to the second rnixer.
-- ~irst local oscillator circuit 94 is connected to the battery by lead 66 and transistor 62, and through lead 232 and a capacitor 234 to ground 68. Theoscillator includes a transistor 92 having its base connected to the junction 224 of resistors 226 and 22~ which resistors have their opposite sides connected to .~
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1011.005 ground and the power supply, respectively. The emi~ter of transistor 92 is also connected to the common ground through the parallel combina~ion of a resistor 218 and a capacitor 220. Also coupled to the base o~ transistor 92 is a crystal 230 which is coupled in parallel across resistor 226 to ground. The collector of transistor 92 is connected by three parallel branches to the power supply. A coil 214 is in the first of these branches while capacitors 216 are in each o~ the second and third branches. The output of the local oscillator is tapped from coil 214 and connected by lead 212 to the second gate of the semi-conductor 91 of the first mixer 78.
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A second local oscillator 72, also connected to the battery via lead 66, is controlled by a crystal 188 and is coupled to a second mixer 74.
Second mixer 74 is connected by lead 76 to the output of the first mixer 78. The -output of the second mixer 74 is fed through amplifier 98 and tuning coil 100 to the FM detector 102 which also provides automatic gain control via line 104 back . --to the preamplifier 84.
The output of the FM detector 102 is connected on lead 105 to an audio amplifier 106 whose output is delivered to ~he transducer or speaker element 108 of the receiving set.
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The semi-conductors ~2 and 91 are preferably of the dual gate MOS field effect transistor type. The microphone 18 is of the noise cancelling type which is not activated by ambient sound and is responsive only to the voice of the wearer of the helmet. For this purpose the microphone is mounted by the adjustable support 20 for adjustment to a position close ~o ~he mouth of the wearer of the helmet 10.
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1011.005 In an optional embodiment, the speaker, transducer or receiver 108 may include a vibratory element responsive to a received signal and contacting the material of the helrnet 10 in such relation that the material of the helmet is vibrated and is comparable to the diaphra~m of a conventional speaker.
Thus any received signals are readily heard and distinguished by the wearer of the helmet otherwise a conventional speaker may be used.
The antennas 50 and 86 are elements which may be housed within ` the carrier 16 in any suitable or convenient fashion. The electrical and ` electronic components of the circuit are encapsulated so as to be compact and to fit within cavities in the carrier 16. The carrier is also provided with cavities `~ within which the operating batteries may be mounted.
The tunnel diode 38 is employed9 as by control of the bias (audio . . : '.
signal), to change switching times at radio frequency rates to produce phase modulation. --.. ' ' ' The two-way communication system of the present imention is - normally in the receive mode and is switched into the transmit mode in response ` to the voice of the user. As previously described and as hereinafter explained in greater detail, the system will promptly switch back into a receive mode during .. ~.
pauses in the speech of the user to thus permit a listener to break in on a ; ' conversation and thus provide real tirne two-way communication.
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Having ~hus described the circuit details, the operation will now ~` be explained. The amplifier 30 has a gain control input, as will be described, and has a voltage comparator on its output. The voltage comparàtor changes the ;.
i` state of an internal fli~flop or multivibrator circuit, as hereinafter described, `~ which switches and controls the transmitter and receiver.
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1011.005Because the microphone 18 is of the noise cancelling type which is not responsive to ambient sound, the amplifier 3û and associated circuit elements are normally off or not active, and the transistor 62 is conducting to provide power to the receiver including the amplifier 84, the local oscillators 72 and 94, the mixers 74 and 78, the detector 102, the amplifier 106 and the transducer or speaker element 108~ While transistor 62 is conduc~ing the transistor 54 is not active or functioning and the transmitting section of the circuit is disabled or not in operation. The slgnals received at the receiving antenna 86 feed the transistor (semiconductor) 82 whvse gain is cont`rolled by the FM detector 102. The FM
~- detector 102 contains a capacitor and rectifier which provide a direct current signal proportional to ~he audio level fed thereto at the tuning coil lûO. The output of the transistor (semiconductc>r) 82 feeds the transistor (semiconductor) 91 whose function is to be a first detector. The other signal to the transistor (semiconductor) ~1 is derived from a constant frequency oscillator which is controlled by the crystal 230.
, The output of the transistor (semiconductor) 91 is the difference between that derived from the crystal controlled oscillator 94 and the incoming radio frequency. The output of transistor (semiconductor) 91 is multiplied by a second local oscillator 72 controlled by crystal 188 and produces a difference frequency at 450 kilohertz which is amplified a~ the intermediate frequency amplifier 98.
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`In the preferred form, various elements including the amplifier 30, the local oscillator 72, the crystal 188, the mixer 74, and the intermediate frequency amplifier 98, are cQntained in a chip identified as IC MOA 902. The output of the intermediate frequency amplifier 98 passes through the tuning coil100 to the FM detector 102. The FM detector 102 is contained in a second chip which also contains the amplifier 106 fed by that FM detector and passes the signal to the speaker or transducer 108 which vibrates the helmet. The transducer of the speaker 108 may be either conventional or, if vibrating, of the piezoelectric or the electromechanical type.
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1011.005 Upon energization of the microphone 18, the amplifier 30 is activated ~o energize the transmi~ter circuit by turning on the transistor 54, and simultaneously deactivatin~ the transistor 62 to shut off the receiver. A chip containing the amplifier 30 also includes a fli~flop operating an off-on signal to turn on either transistor 54 or 6~.
The amplified audio signal derived from the microphone 18 is fed through line 32 to the local oscillator 34 and the tunnel diode 38 to change thebias or switch point. The outpu~ of the tunnel diode 38 passes through capacitor134 to amplifier 44 loaded with a tank circ~lit and containing transistor 136 and its associated components. This tank circuit is a multiple of the local oscillation frequency, constituting a multiplier circuit by capacitive coupling. The second amplifier 46, which includes the transistor 178 and associated components3 further boosts the power and cooperates with the amplifier 44 ~o remove unwanted harmonics of the signal delivered to the transmitting antenna 50.
To further illustrate the electronic switchin~ heretofore described with respect to changing into the transmit mode, in response to a signal caused ~ by the voice of the user of the system, and to further explain the substantially "~ immediate switching back into receive mode during pauses in speech to permit real time two-way communication, reference shol~ld now be had to Figure ~.
Figure 5 illustrates, in greater detail, the amplifier circuit 30 with its internal gain control input, voltage comparator and internal flip-flop as previously . ~ mentioned. In understanding Figure 5, it should be remembered that the 5~ objective of this switching circuit is that transistor 6~ should be always enabled, or on, by virtue of a signal on lead 60 except when the user of the system speaks and similarly, transistor 54 should be disabled, or off, by virtue of a low signal or the absence of a signal on lead ~8 except when the user of the system speaks.
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1011.005 The incoming signal from the noise cancellin~ microphone 18 is fed to an automa~ic gain con~rol amplifier 270. This automatic gain control amplifier is established to provide virtually constant audio output regardless of the intensity of the speaking voice, within the normal ranges of the gain control.
This, of course, is conventional. One output from the automatic gain control ampllfier 270 is coupled across a capacitor 271 to the audio output 32 and then to the oscillator 34 and tunnel diode 38 as previously described. The output from the automa~ic ~ain control amplifier 270 is also coupled to a second amplification stage within the arnplifier 30.
Specifically, the output from the automatic gain control amplifier 270 is coupled to the base of a first transistor 272 which has its emitter coupled to system ground and its collector coupled through a resistor 273 to a source ofpositive potential. The collector output of the first transistor 272 serves as the r base in~ut to a second transistor 274 which has its collector coupled ~o the ~" source of positive potential and its emitter coupled through series resistors 275 and 276, respectively, to the system ground. The junction between resistors 275 `~ and 276 is coupled back to the base of transistor 27~.
~ The output from the gain control amplifier 270 is also coupled ;~; across capacitor 271 to the base of a third transis~or 276. The emitter of ~ransistor ~74 is also coupled to the base of transistor 276. lhe collector of transistor 276 is connected to the source of positive potential and the ernitter of 'i transistor 276 is coupled across the parallel circuit of resistor 277 and capacitor 278 to ground.
The output from the transistor 276 is taken Erorn its emitter to the base of the internal fli~flop which controls the transmitter and receiver.
`~ The internal flip-flop includes a first transistor 280 and a second transistor 282 having their emitters interconnected and coupled to ~round. The collector of transistor 280 receives a voltage from the power supply through a resistor 283 .
~, 1011.005 and has its collector coupled as lead 58 ~o the base of transistor 54. Similarly, transistor 282 has its collector coupled through a resistor 284 ~o the power supply and also has its collector coupled, as lead 60, to the base of transistor 62. The internal flip-flop circuit also includes a voltage divider coupled between the power supply and grour~d including resisto~s 285 and 286 having the junction - therebetween coupled to the base of transistor 282.
. .
The operation of the circuit will now be explained. As previously mentioned, the automatic ~ain control amplifier 270 operates in a conventional fashion to provide a substantially constant audio output on lead 32. Transistors272 and 274 function as conventional amplifiers9 to provide amplification of thesignal and transistor 276, when conducting, charges capacitor 278 and functions as a clipping àmplifier to control the turning on and turning off of transistors 280 and 282. A biasing voltage is provided through resistor 285 and the power supplyto the base of transistor 282 such that transistor 282 is normally on, thus enabling the receive mode by presenting a high signal from its collector to leadi~` 60, and transistor 280 is normally off thus providing a low signal from its , collector along lead 58 and inhibiting transistor 54.
, i~ When the user of the system wishes to speak, the voice is picked up by the microphone 18 and the automatic gain control amplifier provides a signal which is amplified by the transistor 272 and 274 to the base of transistor 276. Transistor 276 conducts and as soon as capacitor 278 charges to a point where the voltage at the base transistor 280 exceeds the bias voltage at the base of transistor 282, the two transistors 2~0 and 282 fli~flop or change their respective states so that transistor 280 conducts and transistor 282 is non-conducting. Transistor 280 conducting provides a signal on line 58 to enable transistor 54 and thus enable the transmitting portion of the circuit~
Simultaneously, transistor 282 is disabled thus removing the enabling signal on lead 60 to transistor 62 to the receive portion of the circuit and thus inhibiting the receive portion of the circuit.
.
1011.005 As soon as ~he user of the sys~em stops speaking, even during a brief pause, the signal is removed from the base of the transistor 276 and the ~ . .
signal at the base of ~ransistor 280 is discharged through the RC circuit comprising the resistor 277 and the capacitor 27~. As soon as ~he signal at the base of transistor 280 drops below the biasing voltage a~ the base of the transistor 282, the two transistors fli~flop again with transistor 280 becoming non-conducting, thus disabling the transistor 54, while transistor 282 becomes conducting, thus enabling the transistor 62. This permits a breal< or an interruption in the communication by permitting the person initially listening to interrupt during pauses in speech. We have determined for effective real-time two-way communication the time constant of the RC circuit should be such that the signal at the base of transistor 280 drops to a value below the bias at the base of transistor 282 within the ranE~e of three to ten miliseconds. This provides a sufficiently fast switching to permit interruptions in speech during normal pauses in speech to provide effective real-time two-way communication approaching that which is provided by dual channel systems such as telephony.
Thus the two transistors 280 and 282 function as a flip-flop and the transistors also function as a voltage comparator since transis~or 280 is conducting only when its base voltage exceeds the constant base voltage of transistor 282. Furthermore these transistors 2~0 and 282, in conjunction with resistor 277 and capacitor 278 function as an astable multivibrator by returningto the preferre~ state (transistor 282 on) a desired time interval after removal of the signal from transistor 276. The time interval, of course, is based on the time constant of the RC circuit.
This two-way communication system is crystal controlled, constituting a transceiver or transmitter and a receiver in a single package, and permits operation of the unit within an assigned frequency range.
_19_ . . , :
'' ' ~3.~,~Z~
1011.005With respect to far field operation, the output or transmitting -frequency is selected in the range of 50 megahertz and thus the wavelength is about 18 feet. Since the near field is defined as less than ~ it appears that at a distance between systems in excess of three feet, the systems will be operating in the far field region.
While the preferred embodiment of the invention has been illustrated and described, it will be understood tha~ changes in the construction may be made within the scope of the appended claims wi~hout departing from the spirit of the invention.
'~
', ' ` ~.
~ ~.
-20 `
Claims (14)
- The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:-1011.005 1. In a two-way voice controlled communication system including a transmitting circuit having a noise cancelling microphone, signal amplifying means connected to said microphone and transmitting antenna means; a receiving circuit including receiving antenna means, signal amplifying means and signal transducing means connected thereto, said receiving circuit being normally enabled and said transmitting circuit being normally disabled, the improvement comprising:
said signal transmitting circuit including switching means coupled to both said transmitting circuit and said receiving circuit, said switching means responsive to the presence of an output signal from said microphone for enabling said transmitting circuit and disabling said receiving circuit;
said switching means further responsive to the absence of said output signal from said microphone for substantially immediately disabling said transmitting circuit and enabling said receiving circuit so that the system will receive signals even during short duration absences of transmissions thus providing two-way real-time voice controlled communication. - 2. The invention as defined in Claim 1, wherein said switching means includes a voltage comparator means for enabling and disabling the transmitting and receiving circuits.
- 3. The invention as defined in Claim 1, wherein the switching means of the transmitting circuit includes gain control means at its input to maintain substantially constant audio output and a voltage comparator means at its output for enabling and disabling said transmitting and receiving circuits.
- 4. The invention as defined in Claim 1, and two transistors each controlling activation of one of said transmitting and receiving circuits by selectively coupling power thereto in response to said switching means.
- 1011.005 5. The invention as defined in Claim 1 wherein said switching means includes a flip-flop for controlling said transmitting and receiving circuits.
- 6. The invention as defined in Claim 2, wherein the response rate of said voltage comparator means prevents activation of the transmitting circuit by a single sharp impulse from the microphone.
- 7. The invention as defined in Claim 1, wherein the transmitting and receiving circuits are contained in a single package, and crystal means in said package controls the frequency range in which the system operates.
- 8. The invention as defined in Claim 1, wherein said transmitting circuit includes a tunnel diode for frequency modulation and frequency multiplication.
- 9. The invention as defined in Claim 1, wherein the transmitting circuit includes a first amplifier responsive to said microphone, a second amplifier and a tunnel diode interposed between said first and second amplifiers.
- 10. The invention as defined in Claim 1, wherein the transmitting circuit includes a first amplifier responsive to said microphone, a local oscillator connected to the output of said first amplifier, a second amplifier loaded with a tank circuit having selected correlation to the frequency of said oscillator, and a tunnel diode connected between said first and second amplifiers for both frequency modulation and frequency multiplication.
, - 11. The invention as defined in Claim 9, wherein the transmitting circuit includes a third amplifier connected to the output of the second amplifier and cooperating with said second amplifier to boost power and remove unwanted harmonics in said transmitting circuit.
- 1011.005 12. The invention as defined in Claim 9, wherein a capacitor is interposed between said tunnel diode and said second amplifier.
- 13. The invention as defined in Claim 1 wherein said transmitting and receiving circuits each include means for selecting the frequency for transmission and reception, said frequency selected for primarily far field operation.
- 14. The invention as defined in Claim 1 wherein said transmitting antenna means and said receiving antenna means are separate antennas.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US909,685 | 1978-05-25 | ||
| US05/909,685 US4166978A (en) | 1976-09-07 | 1978-05-25 | Two-way voice controlled communication system |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1116239A true CA1116239A (en) | 1982-01-12 |
Family
ID=25427662
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA324,261A Expired CA1116239A (en) | 1978-05-25 | 1979-03-27 | Two-way voice controlled communication system |
Country Status (8)
| Country | Link |
|---|---|
| JP (1) | JPS54154212A (en) |
| BR (1) | BR7901085A (en) |
| CA (1) | CA1116239A (en) |
| DE (1) | DE2920834A1 (en) |
| FR (1) | FR2427014A1 (en) |
| GB (1) | GB2021902B (en) |
| IT (1) | IT1116191B (en) |
| MX (1) | MX145103A (en) |
Families Citing this family (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB2271247B (en) * | 1992-10-05 | 1997-02-19 | Motorola Israel Ltd | A radio telephone for a vehicle |
| DE9409319U1 (en) * | 1994-06-08 | 1995-07-06 | Berlin, Florence, Genf | Transceiver |
| US8224286B2 (en) * | 2007-03-30 | 2012-07-17 | Savox Communications Oy Ab (Ltd) | Radio communication device |
-
1979
- 1979-02-16 MX MX176628A patent/MX145103A/en unknown
- 1979-02-16 BR BR7901085A patent/BR7901085A/en unknown
- 1979-03-27 CA CA324,261A patent/CA1116239A/en not_active Expired
- 1979-05-22 IT IT49130/79A patent/IT1116191B/en active
- 1979-05-23 FR FR7913223A patent/FR2427014A1/en not_active Withdrawn
- 1979-05-23 DE DE19792920834 patent/DE2920834A1/en not_active Withdrawn
- 1979-05-24 GB GB7918120A patent/GB2021902B/en not_active Expired
- 1979-05-25 JP JP6408379A patent/JPS54154212A/en active Pending
Also Published As
| Publication number | Publication date |
|---|---|
| IT1116191B (en) | 1986-02-10 |
| FR2427014A1 (en) | 1979-12-21 |
| JPS54154212A (en) | 1979-12-05 |
| DE2920834A1 (en) | 1979-11-29 |
| GB2021902A (en) | 1979-12-05 |
| MX145103A (en) | 1982-01-05 |
| BR7901085A (en) | 1979-11-20 |
| IT7949130A0 (en) | 1979-05-22 |
| GB2021902B (en) | 1982-08-25 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |