United States Patent 15
`5,008,954
`Oppendahl
`Apr. 16, 1991
`[45] Date of Patent:
`
`[11] Patent Number:
`
`[54] VOICE-ACTIVATED RADIO TRANSCEIVER
`{76}
`Inventor: Carl Oppendahl, 27 W. 44th St., #28,
`New York, N.Y. 10035-6645
`
`[21] Appl. No.: 587,602
`[22] Filed:
`Sep. 24, 1990
`
`Related U.S. Application Data
`Continuation of Ser. No. 334,190, Apr. 6, 1989.
`[63]
`[51] Unt. C15 occ eccsccseseseeceeseeseneeenees HO4B 1/44
`[52] US. Che cee ceesccssecceeessetecsneesneens 455/79; 455/89
`
`[58] Field of Search ......:...........08 455/78, 79, 82, 84;
`379/389, 390, 406, 407, 409
`
`[56]
`
`References Cited
`U.S. PATENT DOCUMENTS
`
`4,833,452 S/1989 Currier .....cesscesessstssssessssrseeees 455/79
`
`Primary Examiner—Reinhard J. Eisenzopf
`Assistant Examiner—Edward Urban
`
`ABSTRACT
`[57]
`An improved VOX-activated transceiver has a signal
`
`generator provided in conjunction with the VOXcir-
`cuitry to provide audio tones through the earphone of
`the transceiver to announce the transition to transmit
`mode, or the transition out of transmit mode, or both.
`Bylistening for the tones, the user can be continuously
`apprised of the status of the transceiver. An open mike
`condition (continuous transmission due to continuous
`microphonesignalin excess of the VOX threshold) is
`noted, for example, because the user whose transceiver
`has the open mike will fail to hear the expected tone at
`the beginning or ending of the user’s spoken words.
`Loss ofbattery poweris likewise noted because the user
`will fail to hear the expected tone at the beginning or
`ending of the user’s spoken words.Finally, in transceiv-
`ers having the feature that the VOX circuit is disabled
`for the duration of receipt of a signal above the squelch
`threshold, any resulting transmit starvation will be im-
`mediately apparent becausethe user will fail to hear the
`expected tone at the beginning or ending of the user’s
`spoken words.
`
`8 Claims, 1 Drawing Sheet
`
`ANTENNA
`
`
`
`Page 1 of 8
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`GOOGLE EXHIBIT 1005
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`Page 1 of 8
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`GOOGLE EXHIBIT 1005
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`

`

`U.S. Patent
`
`Apr. 16, 1991
`
`Sheet 1 of 1
`
`5,008,954
`
`ANTENNA
`
`MV
`
`
`
`
`
`TRANSMITTER
`
`RECEIVER
`
`22—T
`
`VOX SENSITIVITY
`
`1)
`
`VOLUME
`
`FIG.4 (PRIOR ART)
`
`26
`
`27
`
`25
`
`24
`
`22
`
`17
`
`FIG. 2
`
`ANTENNA
`
`\I/
`
`FIG. 3
`
`28
`
`31
`
`Page 2 of 8
`
`
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`TIME
`
`FIG. 4
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`Page 2 of 8
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`

`1
`
`5,008,954
`
`VOICE-ACTIVATED RADIO TRANSCEIVER
`
`This application is a continuation of application Ser.
`No. 334,190, filed on Apr. 6, 1989.
`The present invention relates to an improved radio
`transceiver, and particularly to an improved voice-
`activated radio transceiver.
`
`2
`information. If and when a particular VOX-type trans-
`ceiver ofthis type gets “stuck” in transmit mode due to
`a continuing signal in excess of the transmit threshold,
`there is the further problem that for the duration of the
`“stuck” transmit interval, the user of that transceiver
`will be unable to hear anything from othertransceivers
`because the transceiver hearing signals from other
`transceivers requires that the transceiver not be in trans-
`mit mode.
`Another drawback of VOX operationis that the user
`An essential part of any radio transceiver is the ar-
`may not be awareofthe battery having run down,other
`rangement for switching between transmit and receive
`than by noting the prolonged absence of an audible
`modes. With many transceivers, including most ama-
`signal in the earphone.
`teur and citizens’ band radios, the switching into trans-
`Yet another drawback of VOX transmission switch-
`mit mode is accomplished by the user pressing a “trans-
`ing is evident, as discussed below,in the case of certain
`mit” button. Such an arrangement, called “push-to-
`transceivers having a combined microphone and ear-
`talk”, gives the user an unequivocal
`indication of
`phone. Such a transceiver picks up the user’s speech by
`whether the transceiver is in transmit mode or receive
`conduction through the earphone,andoffers the feature
`mode. If the button is pressed, the transceiveris in trans-
`that there is no requirement of a microphonepositioned
`mit mode, and uponthe release of the button, the trans-
`at or near the mouth. Anotherfeature of such a micro-
`ceiver goes into receive mode.
`phonearrangementis that it may beless susceptible to
`Another technique for controlling the switching of a
`ambient noise than a microphone of the type that re-
`transceiver between receive and transmit modes,
`in-
`ceives air-transmitted sound energy from a position
`stead of using a push-to-talk button, is the use of voicé
`near the mouth. A VOX-equipped transceiver with
`actuation. This technique,called “VOX”, used circuitry
`combined microphone and earphone offers a hands-
`to monitor the signal level from the microphone. When
`free, unobtrusive communications capability.
`the signal level exceeds a predetermined threshold, the
`But in a transceiver having combined microphone
`transceiver switches to transmit mode. Later, the signal
`and earphone,design consideration must be given to the
`level will be found to have dropped below a threshold
`problems that might arise due to close proximity of the
`(which may or may not be the same as the previously
`microphone and earphone. It would be undesirable, for
`mentioned threshold), and when the below-threshold
`example,
`if received signals provided to the user
`condition persists for longerthan a predeterminedinter-
`through the earphone were picked up by the micro-
`val, the transceiver switches back to receive mode. The
`phone, thus triggering a change to transmit mode. One
`usual (or at least the desired) result when VOX is em-
`way to avoid that difficulty is to provide a ‘“‘squelch”
`ployedis that the transceiver switches to transmit mode
`circuit on the receiver, so that only received signals
`when the user speaks, and returns to receive modeafter
`exceeding a set threshold are passed to the earphone.
`the user has finished speaking.
`While VOX operation has the advantagethat the use
`Signals
`that
`are
`fainter
`than the threshold are
`“squelched”, i.e. are not provided to the audio amplifier
`can be handsfree, that is, that one need not have one’s
`that drives the earphone. The transceiver thus has two
`handsfree for pressing the PTT button,it can also have
`modes, often termed ‘“‘quiet mode” (during which the
`disadvantages.
`receiver is active but is not providing a signal to the
`One disadvantagerelates to the user’s potential inabil-
`earphone) and “receive mode” (during which the
`ity to recognize an “open mike” condition. For exam-
`squelch threshold has been exceeded andasignalis
`ple, the transmit thresholdappropriate foronesituation,
`45
`being provided to the earphone). The transceiver is
`such as a quiet room, may be inappropriate for another,
`configured so that the VOXcircuit (which monitors the
`_ Such as a noisy room. Where the ambient noise levelis
`signal level at the microphone) is only enabled in quiet
`high, the ambient noise byitself, reaching the micro-
`mode. Stated in the converse, the VOX circuit is dis-
`phone, may reach the transmit threshold and cause the
`transceiver to enter transmit mode. This will result in
`abled wheneverthe received signal exceeds the squelch
`threshold.
`unwanted transmission of the modulated carrier, which
`In a transceiver of the type just described, the reli-
`at the very least has the drawback of needlessly con-
`ance on VOXactuation thus has the severe drawback
`suming power from the powersupply, typically a bat-
`tery. The unwanted transmission has the further draw-
`that there can be “transmit starvation”. During the
`entire time that a strong signal (in excess of the squelch
`back offilling the channel and thus interfering with
`other transceivers that would transmit on the channel.
`threshold) is being received, the user will not be able to
`cause the transceiver to switch to transmit mode by
`Finally, there is the problem that information not in-
`talking. This occurs because the VOXcircuit is disabled
`tended for transmission may be transmitted anyway.
`whena received signal exceeds the squelch threshold.
`Where the communications channel
`is full duplex
`The drawbackof“transmit starvation”is exacerbated
`(e.g. one channel is used for transmit and another for
`by the problem that the user may not be aware that
`receive) the abovementioned problems of unnecessary
`power consumption, domination of the transmission
`talking is not accomplishing the switch to transmit
`mode. As mentioned above, when a PTT button is
`channel, and unwanted transmission of information may
`pushed,
`there is an unambiguous indication that the
`arise. With many transceivers, however, the communi-
`cations channel is not full duplex, that is, a single chan-
`transceiver is in transmit mode. But in VOX mode,
`nel is used both for transmission and reception. With
`there will generally be no indication of a successful
`such transceivers, each of the transceivers transmits on
`voice-activated switch to transmit mode, and thus no
`that channel and each ofthe transceivers (when not in
`clue that an attempt to switch to transmit mode was
`unsuccessful.
`transmit mode) monitors that channel for receiving
`
`BACKGROUND OF THE INVENTION |
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`3
`The combined result of the abovedescribed draw-
`backs is that communication between two users can be
`frustrating if both are using VOX transceivers with
`combined microphone and earphone. One user may
`happen to cause an open mike condition, due to (say)
`allowing headgear to rub against the microphone/ear-
`phone andcontinuously exceeding the VOX threshold.
`The other user will be unable to transmit because the
`received signal, continuously exceeding the squelch
`‘threshold, will disable the VOX circuit for that user. In
`typical hands-free applications, such as skiing, bicy-
`cling, and the like, the transceiveris in a pocket or pack,
`so that even if there are indicator lights showing the
`modes(receive, quiet, and transmit) the users will not be
`' able to see them. Thusthefirst user will be unaware that
`she is causing the open mike condition, and the second
`user will be unaware that her spoken words are not
`being received by thefirst user.
`It is an object of the present invention to provide an
`improved transceiver in which users are unlikely to
`unknowingly cause “open mike” conditions.It is a fur-
`ther object of the invention to provide an improved
`transceiver in which a user will become immediately
`aware of the condition if unable to transmit. It is yet
`anotherobjectof the invention to provide an improved
`transceiver in which the user will more promptly learn
`of loss of battery power.
`
`SUMMARYOF THE INVENTION
`
`In the improved transceiver of the invention, signal
`meansare provided in conjunction with VOX circuitry
`to provide audio signals, typically tones, through the
`earphone of the transceiver to announcethetransition
`to transmit mode,orthe transition out of transmit mode,
`or both. By listening for the tones, the user can be con-
`tinuously apprised of the status of the transceiver. An
`open mike condition (continuous transmission due to
`continuous microphonesignal in excess of the VOX
`threshold) is noted, for example, because the user whose
`transceiver has the open mike will fail to hear the ex-
`pected tone at the beginning or ending ofthe user’s
`spoken words. Loss of battery poweris likewise noted
`because the userwill fail to hear the expectedtone at the
`beginning orendingofthe user’s spoken words.Finally,
`in transceivers having the feature that the VOX circuit
`is disabled for the duration of receipt of a signal above
`the squelch threshold, any resulting transmit starvation
`will be immediately apparent because the user will fail
`to hear the expected tone at the beginning or ending of
`the user’s spoken words.
`
`DESCRIPTION OF THE DRAWINGS
`
`The invention will be disclosed with reference to a
`drawing, in which
`FIG. 1 showsa functional block diagram of a VOX-
`operated transceiver according to the priorart;
`FIG.2 shows a perspective external view of a typical
`VOX-operated transceiver with combined microphone
`and earphone;
`FIG. 3 showsa functional block diagram of an im-
`proved VOX-operated transceiver according to the
`invention,including a rising/falling edge detectcircuit;
`and
`FIG.4 shows the inputs and outputsofthe rising/fall-
`ing edge detect circuit.
`
`Page 4 of 8
`
`5,008,954
`
`4
`
`DETAILED DESCRIPTION OF THE
`INVENTION
`
`FIG. 1 showsa functional block diagram of a VOX-
`operated transceiver, of which a typical example is the
`Radio Shackcat. no. 21-404 transceiver. In such a trans-
`ceiver, received signals from the antennagoto the re-
`ceiver 12, and the signal level received at the receiver is
`provided to a squelch circuit 13. At such time as the
`signal level exceeds the squelch threshold, the squelch
`circuit 13 provides a gating signal to switch 14 and to
`VOX circuitry as discussed below. Presence of the
`gating signal turns on switch 14, providing the received
`audio signal to amplifier 15 and thus to the speaker16.
`The volumelevel provided at the speaker 16 is adjust-
`able by the user through volumecontrol 17.
`Speechorother audio presentat the microphone 18is
`amplified by amplifier 19. The VOXcircuit 20 monitors
`the output of amplifier 19 and (if not disabled by the
`squelch gating signal) will generate a transmit control
`signal at line 21 when the outputof amplifier 19 exceeds
`the VOX threshold. The VOX threshold may be ad-
`justed by the user by VOXsensitivity control 22.
`The transmit control signal, when asserted, disables
`receiver 12 and enables transmitter 23. Though not
`shown explicitly in the figure, some circuitry, such as
`the RF oscillator, may be shared between the transmit-
`ter and receiver. The transmitter and receiver typically
`Operate at 49 Mhz on oneof the channels authorized by
`the Federal Communications Commission for unli-
`censed, low-power communications. The power supply
`and on/off switch are not shown,norare optional push-
`to-talk arrangements. Thecircuit designs and physical
`layout of components required for such transmitters and
`receivers are well known. The amplifiers 19 and 15 are
`old, as are the VOX 20 and squelch 13 circuits.
`is
`A typical commercially available transceiver
`shown in an external view in FIG. 2. Microphone 18
`and speaker 16 are both contained within earpiece 24;
`the microphone 18 is preferably of the electret-con-
`denser type dueto its small size and weight. A flexible
`cord 25 carries shielded signals to the microphone and
`speaker of earpiece 24. The shield of cord 25 acts as an
`antenna as well. Case 26 contains the balance of the
`transceiver, and permits user access to VOX sensitivity
`control 22 and volume control 17, as well as to on/off
`switch 27.
`In the improvedtransceiver of the invention, a rising-
`/falling edge detect circuit and audio oscillator are
`provided as shown in FIG.3, providing the beneficial
`features of the invention.
`The function of the transceiver in receive modeis as
`described above in connection with theprior art trans-
`ceiver, with received signals from antenna 11 detected
`and amplified by receiver 12 and supplied to squelch
`circuit 13 and to switch 14, and thence to amplifier 15
`and speaker 16.
`to
`The function of the transceiver with respect
`speech or other audio inputs to microphone 18is largely
`as described above, insofar as the inputs are amplified
`by amplifier 19 and provided to transmitter 23 and an-
`tenna 11. However, the transmit control signal 21 is
`provided not only to transmitter 23 and receiver 12 but
`also to rising/falling edge detector 28. Upon detection
`of a rising or falling edge, the detector 28 sends an
`enabling pulse to audio oscillator 29. The output of
`audio oscillator 29 goes to amplifier 15 and thence to the
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`5
`speaker16, thus alerting the user ofa transition to trans-
`mit mode or out of transmit mode.
`FIG. 4 showsin greater detail the input and output
`signals of detector 28. Its input shown byline 30 is the
`transmit control signal 21. Its output shown by I!ne 31
`is the enabling signal to audio oscillator 29. Eachtransi-
`tion ofline 30 gives rise within the detector 28 to a pulse
`of predetermined width as shownbyline 31.
`The output of audio oscillator 29 is shown as con-
`nected directly to the input of amplifier 15, but depend-
`ing on the output characteristics of switch 14 and the
`input characteristics of amplifier 15 the connection may
`‘preferably be capacitively coupled or coupled through
`a switch that is controlled by the enabling output of
`detector 28.
`The audio tone provided at speaker 16 in response to
`the transition into or out of VOX modeis preferably
`quite brief in duration, on the order of a few millisec-
`onds. Brevity of the tone minimizes its intrusiveness
`when generatedas the userstarts talking. Furthermore,
`if the microphoneis integrally mounted with the ear-
`phone, care must be taken that the tone annunciating
`the transition out of transmit mode doesnotitself trig-
`ger the VOX circuit back into transmit mode. Thetypi-
`cal VOX circuit goes into transmit mode onlyafter the
`above-threshold input has remained above the thresh-
`old for some time, at least a few tens of milliseconds.
`Keeping the tone quite brief will thus keep it from trig-
`gering a spurioustransition into transmit mode.
`Another way to keep the end-of-transmit mode tone
`from retriggering the VOX circuit is to put a switch in
`the audio path between amplifier 19 and VOX circuit
`20, with the switch controlled by the output of detector
`28, so that the microphoneis disabled during the brief
`time the toneis present.
`;
`Many users of VOX equipment develop the habit of
`prefacing each instance of speech with ‘‘ahhh” or some
`other sound to trigger the VOX prior to the time the
`wordsare actually spoken; this reduces the problem of
`the user’s first syllable being cut off due to less-than
`instant VOX switching. Such usersare unlikely to mind
`the start-of-transmission alerting tone. But for those
`whofind thestart-of-transmission alerting tone distract-
`ing or annoying, it may be preferable to configure de-
`tector 28 only to generating its enabling pulse at the end
`oftransmission. For other users, the end-of-transmission
`pulse may bethe most distracting, and it may be prefera-
`ble to configure detector 28 only to generating its en-
`abling pulse at the beginning of transmission.
`I claim:
`1. Ina transceiver of the type having a transmit mode,
`a receive mode, and a squelched mode, and wherein the
`transceiver enters receive mode uponreceipt of a signal
`having a strength greater than a predetermined squelch
`threshold, and wherein the transceiver enters transmit
`mode by voice activation of a voice activation means
`having a triggering time, and wherein the audio signal
`received by the receiver portion of the transceiver is
`conveyed to the user by speaker means, the improve-
`ment wherein is provided:
`sound pulse generation means responsiveto the voice
`activation for generating a momentary alerting
`sound audible to the user and conveyedto the user
`by the speaker means, said sound pulse generation
`means generating the momentary alerting sound at
`about the time whenthe transceiverenters transmit
`mode,
`the duration of said momentary alerting
`
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`5,008,954
`
`6
`sound being less than the triggering time of the
`voice activation means,
`whereby the user is alerted that the transceiver has
`entered transmit mode, and wherebythe user will
`be made aware of loss of power or of spurious
`continuous transmission.
`2. The transceiver of claim 1 wherein the transceiver
`has a microphone and the microphoneis integrally
`mounted with the speaker means.
`3. In a transceiver of the type having a transmit mode,
`a receive mode, and a squelched mode, and wherein the
`transceiver enters receive mode uponreceiptof a signal
`“having a strength greater than a predetermined squelch
`threshold, and wherein the transceiver enters transmit
`mode by voice activation of a voice activation means
`having a triggering time, and wherein the audio signal
`received by the receiver portion of the transceiver is
`.conveyed to the user by speaker means, the improve-
`ment ‘wherein is provided: sound pulse generation
`meansresponsive to the voice activation for generating
`a momentary alerting sound audible to the user and
`conveyed to the user by the speaker means, said sound
`pulse generation means generating the momentary
`alerting sound at about the time when the transceiver
`leaves transmit mode, the duration of said momentary
`alerting sound being less than thetriggering time of the
`voice activation means,
`wherebythe user is alerted that the transceiver has
`left transmit mode, and wherebythe user will be
`made awareof loss of poweror of spurious contin-
`uous transmission.
`4. The transceiver of claim 3 wherein the transceiver
`has a microphone and the microphone is integrally
`mounted with the speaker means.
`§. In a transceiverof the type having a transmit mode,
`a receive mode, and a squelched mode, and wherein the
`transceiver enters receive mode uponreceiptofa signal
`having a strength greater than a predetermined squelch
`threshold, and wherein the transceivers enters transmit
`mode by voice activation of a voice activation means,
`and wherein the audio signal received by the receiver
`portion of the transceiver is conveyed to the user by
`speaker means, the improvement wherein is provided:
`sound pulse generation means responsiveto the voice
`activation for generating a momentary alerting
`sound audible to the user and conveyed to the user
`by the speaker means, said sound pulse generation
`means generating the momentaryalerting sound at
`about the time whenthetransceiver enters transmit
`mode, the sound pulse generation means further
`comprising meansfor disabling the voice activation
`meansfor the duration of said momentaryalerting
`sound,
`wherebythe user is alerted that the transceiver has
`entered transmit mode, and wherebythe user will
`be made aware of loss of power or of spurious
`continuous transmission.
`6. The transceiver of claim 5 wherein the transceiver
`has a microphone and the microphone is integrally
`mounted with the speaker means.
`7. In a transceiverof the type having a transmit mode,
`a receive mode, and a squelched mode,and wherein the
`transceiver enters receive mode uponreceiptofa signal
`having a strength greater than a predetermined squelch
`threshold, and wherein the transceiver enters transmit
`mode by voice activation of a voice activation means,
`and wherein the audio signal received by the receiver
`
`Page 5 of 8
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`

`5,008,954
`
`7
`portion of the transceiver is conveyed to the user by
`speaker means, the improvement whereinis provided:
`sound pulse generation means responsive to the voice
`activation for generating a momentary alerting
`sound audible to the user and conveyed to the user
`by the speaker means, said sound pulse generation
`means generating the momentaryalerting sound at
`about the time whenthe transceiver leaves transmit
`‘mode, the sound pulse generation means further
`comprising meansfor disabling the voice activation 10
`
`5
`
`8
`meansfor the duration of said momentaryalerting
`sound,
`whereby the user is alerted that the transceiver has
`left transmit mode, and whereby the user will be
`made awareof loss of poweror of spurious contin-
`uous transmission.
`8. The transceiver of claim 7 wherein the transceiver
`has a microphone and the microphoneis integrally
`mounted with the speaker means.
`+ *
`*
`
`®
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`
`
`UNITED STATES PATENT AND TRADEMARK OFFICE
`CERTIFICATE OF CORRECTION
`5,008,954
`Page 1 of 2
`
`:
`
`PATENTNO.
`
`DATED
`
`: April 16, 1991
`
`INVENTOR(S)
`
`: Oppedahl
`
`It is certified that error appears in the above-identified patent and thatsaid Letters Patentis hereby
`corrected as shown below:
`
`Title page should be deleted to appear as per attached Title page.
`
`Signed and Sealed this
`
`Sixteenth Day of March, 1993
`
`Attest:
`
`Attesting Officer
`
`
`STEPHEN G. KUNIN
`
`Acting Commissioner of Patents and Trademarks
`
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`

`Page 2 of 2
`
`5,008,954
`Patent Number:
`[11]
`United States Patent (15)
`
`
`[45] Date of Patent:Oppedahl Apr. 16, 1991OEtentApr.10,
`1991
`[54] VOICE-ACTIVATED RADIO TRANSCEIVER
`generatorprovided in conjunction with the VOXcircuit-
`[76]
`Inventor: Neaeeedahh27WathSt ff
`transceiver to announcethe transition to transmit mode,
`ry to provide audio tones through the earphone of the
`or the transition out of transmit mode, or both. By
`[21] Appl. No.: 587,602
`listening for the tones,
`the user can be continuously
`apprised of the status of the transceiver. An open mike
`[22] Filed:
`Sep. 24, 1990
`Related U.S. Application Data
`condition (continuous transmission due to continuous
`microphonesignal in excess of the VOX threshold) is
`[63]
`Continuation of Ser. No. 334,190, Apr. 6, 1989,
`noted, for example, because the user whose transceiver
`has the open mikewillfail to hear the expected toneat the
`[S0]) Unt, Checeeeessesstenscasesee HO04B 1/44
`[52] U.S.Ccccccsesesseeseeees 455/79; 455/89
`beginning or ending ofthe user's spoken words. Loss of
`[58]
`Field of Search... 455/78,79, 82, 84;
`battery poweris likewise noted because the userwillfail
`379/389, 390, 406, 407, 409
`.
`.
`to hear the expected tone at the beginning or ending of
`[56]
`References Cited
`the user’s spoken words. Finally, in transceivers having
`U.S. PATENT DOCUMENTS
`the feature that the VOX circuit is disabled for the
`duration of receipt ofa signal above the squelch thresh-
`4,833,452
`S$/1989 Currier oo.ccccccsscceccccoosssss, 455/79
`wiganyresultingtransmitstarvation will beimmediately
`Primary Examiner—Reinhard J. Eisenzopf
`apparent becausetheuser will fail or hear the expected
`Assistant Examiner—Edward Urban
`tone at the beginning or ending of the user's spoken
`[57]
`ABSTRACT
`words.
`An improved VO¥-activated transceiver has a signal
`8 Claims, 1 Drawing Sheet
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`
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`ANTENNA
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`SPKR
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`|-—1?
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`VOLUME
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`
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`TTDOereels
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`‘OSCILLATOR -
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`28
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`22—1 VOX SENSITIVITY
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`Page 8 of 8
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