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Publication numberUS2833866 A
Publication typeGrant
Publication dateMay 6, 1958
Filing dateJul 12, 1956
Priority dateJul 12, 1956
Publication numberUS 2833866 A, US 2833866A, US-A-2833866, US2833866 A, US2833866A
InventorsGeorge W Esser
Original AssigneeMc Graw Edison Co
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Voice-controlled dictation-recording system
US 2833866 A
Abstract  available in
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Claims  available in
Description  (OCR text may contain errors)

United Sttes Patent 2,833,866 VOICE-CONTROLLED DICTATION-RECORDING SYSTEM George W. Esser, West Orange, N. J., assignor, by mesne assignments, to McGraw-Edison Company, Elgm, Iil., a corporation of Delaware Application July 12, 1956, Serial No. 597,370

7 Claims. (Cl. 179-1001) This invention relates to improvements in dictationrecording systems in which the starting and stopping of the dictating machine is controlled automatically by the voice signals spoken into the microphone. The invention is particularly applicable to remotely-controlled recording systems and is herein described in connection therewith but without intending any unnecessary limitation thereto.

The advantage of controlling a dictating machine by the voice signals being recorded is that the dictator can direct his full attention to the subject matter of his dictation. A particular advantage of voice-controlled operation arises in connection with remotely-controlled dictation-recording systems wherein a dictator selects an idle machine through a linkage apparaus by a dialing process,

in that when the machine is started and stopped by the voice signals the linking apparatus is greatly simplified. However, to simplify the description, I do not herein show my invention in connection with any dial linkage system. I

A general problem with voice-operated dictation-recording systems is in recording each bit of spoken dictation from the very beginning. In other words, there should be no delay as between the instant the first bit of dictation arrives at the dictating machine and the instant the machine is started. Since there is unavoidable delay in starting the machine by the voice signals, due to inertia and other effects, it has become the practice to delay the transmission of the voice signals for a period at least as great as the delay characterizing the starting mechanism and preferably for a considerably longer delay period. Such transmission delay is accomplished conveniently by using a magnetic recording system operating on a continuously-moving endless record medium to record thereon at one point, pick up therefrom and feed to the dictating machine at a later point, and to erase at apoint between the recorder and reproducer.

When such transmission-delay apparatus is used there is desirably provided a stand-by signal, such as a lowfrequency hum, which is fed back to the dictators re ceiver to apprise him whenever the dictating machine is stopped. Since the telephone-type apparatus has the receiver and microphone connected in the same line, this warning signal is then fed also to the transmission-delay apparatus where it is recorded continuously while the dictating machine is stopped. When the dictating machine is next started responsive to a voice signal spoken into the microphone, the warning signal which stands already recorded on the magnetic record medium of the transmission-delay apparatus is fed to the dictating machine and there recorded in advance of arrival of the voice signal for a period equal to the delay period of the transmission-delay apparatus less the delay period of the starting mechanism. Over the last portion of this hum period equal to the delay period of the starting mechanism, the voice signal appears and is recorded by' the dictating machine with the superimposed hum. For

2 instance, for a transmission delay of 150 milliseconds and a start delay of milliseconds, the dictating machine When started by a voice signal spoken into the microphone will first record the hum' signal for a period of 130 milliseconds, then record the bum and voice signal for a period of 20 milliseconds prior to the recordation of the pure voice signal. This recordation of bursts of .hum signal preceding the voice signal is very annoying and distracting to a transcriber. Of course, to the extent that drop-out of the starting mechanism is delayed at the ends of bits of spoken dictation, the operation is more nearly continuous and bursts of recorded hum are avoided. Practice has shown it desirable not to delay dropout of the starting mechanism by more than 5 seconds. Thus, any cessation in speaking dictation to the microphone for a period of 5 seconds or more would result in a burst of stand-by hum being recorded prior to the voice signal.

It is an object of my invention to provide a simple means for overcoming the aforementioned disadvantages so that none of the stand-by hum signal is ever noticeably recorded on the record of the dictating machine regardless of the duration of any cessation of voice spoken into the microphone.

Another object is to provide a very simple and economical means which is effective to suppress the transmission of the stand-by hum signal to the transmission delay apparatus withoutnoticeably impairing the quality or intelligibility of the voice signals recorded by the dictating machine.

Another object is to provide such a suppression means which is frequency-sensitive to afiford a much stronger suppressing effect in the lower frequency spectrum bearing the hum signal than in the upper frequency spectrum bearing the frequencies which impart intelligibility to the voice.

These and other objects and features of my invention will be apparent from the following description and the appended claims.

In the description of my invention reference is had to the accompanying drawings, of which:

Figure 1 is a schematic circuit diagram of a dictationrecording system embodying my invention; and

Figure 2 is a fractional view of a portion of the above circuit diagram modified to illustrate another form of my invention.

For simplification of descriptiommy invention is herein described in connection with a dictation-recording system having a directly interconnected remote dictators station and dictating machine. Such a system may, for example, be of the type disclosed in the pending Somers et al. application Serial No. 247,244, filed September 19, 1951 (now patent number 2,757,238 dated July 31, 1956), and to which reference may be hadasto details.

The present system comprises a dictating machine 10 (fractionally shown) comprising a record support 11 in the form, for example, of a turntable having a center shaft 12 journaled at 13 in the frame 14 of the, machine. The turntable is driven from a driving wheel 15 frictionally riding on the periphery of the turntable. The driving wheel is coupled through a clutch 17 to a motor 18. Connected by gearing 19 to the shaft 12 is a feed screw 20 journaled at its endsin standards 21 on the frame." Mounted for movement across the turntable on a support comprising, for example, a cross rod 22 is a carriage 23. Mounted on this carriage is a'feed nut 24 'engageable with the feed screw to provide a progressive traveling movement of the carriage as the turntable is driven," The carriage carries a recording device 25 engageable with a record 26 on the turntable to describea spiral ICCOIding' trackthereon.

Patented May 6, 1958 dh' fehldte dictatorss'tation 27 is 'provided'with "a hand set 28 of 'the usual telephone type having therein a carbon button microphone 29 and a receiver 30. A commumcation circuit 33 leads to this station through an on-otbstation switeh 35. Connected across the communication circuit at the station is the carbon button microphone-and a resistor 34in parallel as Well as the receiver :lhrcugh a series resistor 31 and blocking coridenser 32; In -the communication -circuit beyond the station is an audio transformer 36 the secondary of which is connected to -the input of an-amplifier system as will appear. Direct current -is provided to the station to eriergiz e the carbonbuttonmicrophone from a'rectifier-filter 37 through-a control relay 38. Alternating current power to the-rectifier filter-is provided from a power sonrcei-ndicated bythe terminals 39.

Normally the station switch '35 is'held open by resting the handpiece on an extension 35a of one pole member of th e switch. When the handpiece is removed, the switch is closed by a spring 40 to start fiow of direct current in the line33 through the relay 38, primary of the transformer 36, microphone 29 and resistor 34 in parallel. The microphone is then energized so that it will provide audio signal current in the communication linc responsive to a voice spoken into the microphone. This audio current is by-vpassed from the relay 38 by a condenserfl. The relay is operated by the direct current in the line when the station switch is closed to operate a switch 4 2 in the. power line 43 leading to the motor 18 so that the motor is started as soon as the handpiece is removed from its support. h y

he audio signals are fedtrom the secondary of the transformer 'Stljto'the input of a line amplifier 44 only diagrammatically shown. In the output circuit of this line amplifier there is -a volume control 45 the movable tap of which is connected to the grid of a voltage amplifier'tjtube l6 comprising the only stage of a recording amplifier. C. voltage is-supplied at a terminal 47 markd B+. This terminal is connected through a paralleled resistor-condenser combination to the screen grid and through a-load resistor 49 to the plate of this tube. A-eircuit leads also from thepla'te serially through a resistor '50, blocking condenser 51 and coil of a recording head 52 to a groundwire 53 of the amplifier stage, the recording head being part of a transmission-delay apparatus T hereinafter'described. From cathode to the ground w'rresa' new; resistors in series,- a resistor 54 of normal value andares'istor 556i above-normal value, the two of which are paralleled by a single condenser 56. As will appearftheies'istor' 55 is provided to reduce thegain of the amplifier tube by overbiasing the grid, but this resistor is shorted ant during operation of the dictating-machine tojrestoi'e the gain to nerinal value.

The'iecbr'dir'i'g head 52 ofthe transmission-dela'yappander is'iriouiited in close juiitaposition but not in eoiitact withama'gnetic drum '57 driven continuously by a' hiotor' 58'connected also across the power line 43. Feeding" also 'into this'recording' head is a high-frequency btas'ejnrre'mnaman oscillator 59 according 'to usual pracfiee. 57 is'provided with a peripheral coating of a'pdwde'r'e'dinaghetic material so that it will receive ahd heai' a' ma'g'ne'tic pattern corresponding to the audio 15 fedto the recording head. At about three-quarters turn 'elrduiid the "from the recording head 'a'i'epibd'ulc'ing head' 60 mounted in close juxtaposition but not in" c'oiitac't'with the-drum, and between the two heads thereisan erasii'ig head 62, which may be 'simply'a-b'ar ct iiioii'fitcd lilie'wise'in 'juiitaposition but iibt in ebiitact meat-amine purpose of avoiding contact df'the'he'ads "with'the'beihg to avoid Wear. The ""rbtared'typi'can at about "five revelntiehs per I i e bne revoliition'every 'ZOOjriiillisebdndswith the r lt tear-me transit 'ti'meonthe eon therecordiiig' head to the remaining head is" 21136115130 fitmiseeaad s. "SlfiCe"Vi'Y it"6f'di6tation"spokeniiitc "theniicrophone'is recorded on"the-druni by'therecording head and is not picked up until it reaches the reproducing head, there occurs a millisecond delay in the transmission of all signals to the dictating machine. The function of the erase head 62 is to remove the magnetic pattern constantly ahead of the recording head so that the recording head is enabled constantly to record the signals fed thereto from the recording amplifier 46.

Th'e' voice signalene'rgy from the line amplifier "44 is also fed through a line 63 including a blocking condenser 64 to an input volume-control 54 of a relay amplifier 66. The-movable contact of this control I connectedto the grid of a tube 67. The cathode of=this tubedsconnected through a bias resistor 68 to a ground line 69 and the'plateis conncc'ted'through a load resistfirWll to a terminal 71 marked B+ and designating a source of D. C. plate voltage. Signal current from the plate is fed through a neon bulb 72 to the grid of a second amplifier tube 73. Connected from this grid to the ground line 69 are a resistor 74 and condenser '75 in parallel. As will appear, this resistor-condensercombination operating in conjunction withthe neon bulb 72 provides a dropout delayfor maintaining'the voltage'on the grid'ofthe tube 73 'for a predetermined period after cessation 'of dictation spoken into the microphone. 'Thecathdde of the tube 73'is connected through a resistor'76to the ground line 69 andthe plate is connected through-the coil of-a relay '77 to a-terminal 78 mar'kdB-land designating a source of'-D. C.,-'plate voltage. Associated with the amplifier tube 73 is a secondtube '79 having its cathode connected in cornmori'therc'wi'th andhavlng I its plate connected directly to the B+terrriif1al 7 8. The

of the tube '79 is connectedto the "adjustable'tapo f' a rheostat 8t) connectedl'through' a cut d'o'w'n resistorf8l from-theB-F terminal 78 to the ground line '69. The function of the tube 79 is to adjust the cathode bia'sof the tube 73 according to the positioning of thetap of the 'rheostat 8'0.

The relay 77 has a switch 82 connected in the circuit 83 of a clutch-operatingsolenoid841connected'irlechanically to the clutch '17'as designated diagrammaticallyby the line'SS. This solenoid may be connected across the D.-C.-soiirce'from the're'ctifier filter 37. "When'the dictator-speaks into the microphone 29' to providean audio signal in the communication clrcuit'33abovea preset threshold level exceeding any likely no'isele'vel, the audio signal is fed through the transformer "36 and line amplifier 44' to' the'relayampli'fi'er 66. In thi's'relay amplifier the signal is 'first amplified byithe amplifier stage 67 and 'is then through the'neon' tube 72to' the gridbf'thes'tage 73. The neon tube'r'equlres "about'60 vdl'tsa'cr oss' it"to'render'it conductive butth'e majo'rportionbf this voltage is providedconstarltlyby' the D. C. plate voltage source 71; 'When the signal voltage is fed to the iel'a'y amplifier the peaks thereof from the plate of the tube67 will add to thenormalp'late' voltage to override the threshold voltage on the neon tube and cause the p'e'alfrs to 'be fed to the grid of the tube '73. The tube 73 is biased by the associated tube'79 to provide censtann a preset level o'f'plate 'curreritthroughhhe relay coil 77 which is however insufiici'e'nt to opera'te the rela Typically, this constant current supply may be 2 ma. and the relay may operate at Shea. 'lnresponse' to the: signal voltage peaks fed through" the neontube'to the grid of thetub'e 73fthe condenser "751's charged and the grid voltage 'is 'builtup to increase the plate current tothe valuerequ'i'r'ed to"(:{p'tzr'atethe'relay- When the relay" o erates the' contacts 82 thereof are closed to causethesol'er'io'id 84' to enga e the "clutch 17and""start the dictatingmaehine. Through proper 'adjustment'of the rheostat "65' and bias control rheostat- 80," 'thefrelay will operateiimespense tc' dictationjspoken't'into -the"hiicrothe relay will typically be delayed by to 30 milliseconds.

The audio signals fed from the line amplifier 44 through the recording amplifier 46 to the recording head 52 are there recorded on the magnetic drum 57, then picked up by the reproducing head 60 and fed through the amplifier 61 to the recording device 25 of the dictating machine. Because of the delayed transmission of the signal energy to the dictating machine being much greater than the delay in the operation of the starting relay 77, the dictating machine will be started before the audio signals arrive to assure that each bit of dictation is recorded from the very beginning.

Whenever the dictator stops speaking into the microphone, the voltage across the neon tube falls and the tube becomes immediately non-conductive. The charge on the condenser 75 is then captured except for its discharge through the associated resistor 74. The time constant of the circuit 7475 is so set in combination with the bias setting on the tube 73 that the tube 73 will maintain a current for about five seconds sufiicient to maintain the relay 77 operated after the feed of signal energy to the tube 73 ceases. Thus, interruptions in the voice spoken into the microphone 29 for periods not in excess of about five seconds will not cause the dictating machine to be stopped.

In voice-controlled systems of the character herein described it is desirable to provide a signaling means to apprise the dictator as to Whenever the dictating machine is stopped. This is particularly important because it warns the dictator whenever he speaks in too low a voice into the microphone as well as when the system is out of adjustment to prevent him from continuing to speakdictation with the misimpression that the machine is operating. In order that a positive signal will be given to the dictator it is desirably fed through the communication line 33 to the receiver 39. Such signal is derived preferably from the A. C. power line 43 through a rectifier 86 and a condenser 87 to a voltage cut-down transformer 88, the purpose of the rectifier being to break up the 60- cycle voltage into higher frequency components, and of the condenser 87 to reduce also the voltage level. From the transformer 88 the hum signal is fed to the receiver 29 through a line 89 to the audio transformer 36 serially including a pair of contacts 90 of the relay 77. The contacts 90 are closed when the relay is not operated and opened to cut off the signal the instant the relay is operated. Since the hum signal appears in the system only when the dictating machine is stopped, it is referred to as a stand-by signal.

Since the hum signal is fed into the same line as that leading from the microphone, it will be recorded by the transmission-delay apparatus T during stand-by Although the hum signal must have a level below the threshold level of the audio signals required to start the machine, else it would operate the relay to start the machine, it will nevertheless be recorded at an audible level by the transmission-delay apparatus T. Accordingly, there will occur the following sequence starting with the instant a voice signal is spoken into the microphone above the threshold level required to start the dictating machine: During the first 20 milliseconds representing the delay in the operation of the relay 77, the dictating machine re- I mains stopped but the voice signal is recorded on-the drum 57 together with the hum signal; for the next 130 milliseconds the dictating machine will receive and record only the hum signal; for the next 20 milliseconds it will receive and record both the voice signal and the hum signal; and thereafter it will receive and record the pure voice signal without any superimposed hum signal. Thus, each time the dictating machine is started it will record a burst of hum signal ahead of the voice signal.

By my invention I eliminate effectively the recordation of the signal hum by the dictating machine without impairing the quality or intelligibility of the recorded voice signals. In accordance with my first embodiment shown in Figure 1, this is accomplished by reducing the gain of the recording amplifier 46 the instant the dictating machine is stopped so that during stand-by the hum signal recorded by the transmission-delay apparatus 56 is at such low level that when picked up by the reproducer 60 and fed to the dictating machine it is there recorded at a level below the threshold of audibility. However, the instant the dictating machine is started the gain of the recording amplifier 46 is restored to normal.

simply by adding the resistor 55 in the cathode circuit of this amplifier and providing the relay 77 with another set of contacts 91 which are connected to short the resistor when the relay is operated to start the machine and to reintroduce the resistor when the relay drops out to stop the machine.

Since the level of the voice signal required to operate the relay 77 is necessarily greater than that of the hum signal in order that the hum signal will not itself ever be effective to operate the relay 77, the voice signal will override the hum signal and be recorded on the drum 57 at a level above the threshold of audibility; nevertheless, until the relay 77 is operated the voice signal will be recorded at a subnormal level. Thesequence of results now obtained with my invention following the instant a dictator speaks into the microphone to start the machine is therefore as follows: the voice signal is recorded on the drum 57 from the start at a subnor'mal but still audible level but the hum signal is recorded below the level of audibility, and as soon as. the relay is operated the hum signal is cut out and the gain is restored to normal. This results in the dictating machine never recording the humsignal at an audible level but during the first 20 milliseconds or thereabout, representing the delay period in the operation of the start relay 77, the voice signal will be recorded at a subnormal but still audible level. Experience has shown that this'slight reduction in the level of the recording of the voice signal during the first'instant,

transmission-delay apparatus 56 is reduced by introducing an attenuating element in the line instead of reducing the gain of the recording amplifier 46. Preferably, the attenuating element is a condenser 92 connected in the line as between the line amplifier 44 and the volume control 45, there having been already a blocking condenser 45a in this line .as shown in Figure 1. However, the condenser 92 has a much smaller capacity than that of the condenser 45a, being typically about one-tenth of the value of that condenser. Moreover, the particular value of the condenser is chosen in relation to the resistance of the volume control 45 so that the condenser 92 will attenuate substantially the hum frequencies in the lower audio spectrum and will have little attenuating effect on the frequencies in the higher audio spectrum which impart intelligibility to the voice. There is accordingly only the resistor 54 in the cathode circuit of f the amplifier tube 46 since this amplifier is now to operate always with normal gain. The contacts 91 are however-now connected across the condenser 92. The result is that when the relay 77 drops out to stop the dietating machine the condenser 92 is introduced into the Such control over the gain of the amplifier 46 is accomplished the entire frequency spectrum of the voice during the initia'h instantaneonsizperiodzequah -tontheisdelay periodiiofi thesta'rfingamechanism; there is' inowthe advantage-that F it is on1y'-the'*lower portion of the audio-spectrum that is reeordedat s'ubnormal level:td'suppress the hum-'si'gnal.- In otherzwords; wh'en a dictator-speak'sdnto the micro-=- phone to -start the machine; the-5 higher fr'equency com ponents which impart intel'li'gibili-tyvto the voic'e are re cordedfat normal lveh-fr'om the-starti 'I-he embodiments" ofmy-iriventi'on hereiriparticularly shown' and' described -are intendedto -be -illustrative=-and not linlitative-of 'my'invention'since the same are subjectto -changes and-modiiications 'with'ont departure *fromflthe a scopeofmyinvention; which fendeavorto express-"ac-' cording *tothe following'claimsr 1. Iri a. dictation-'recording systenr 'includin'gp dictat ing machine and .a dictators transducer.the'combination of control meansjfor starting and stopping saidridictating machine; an audidcircnit "fo'rconnecting said transducer to ,s'aidmachine; an electrically-operable device connect edi to said andio circuit and operated lbyaudiosignals therein produced by dictationlspoken .into .said' transducer 1 forroperat-in'g said-control means to start position; means controll'edJby said..electrically operable means fdr feeding, a. warning, signaL -.into saidjtaudio cir'cuit t'o apprise the dictator lwhenrsaid 'control 'means is tin-tstop posi'tion; and tmeans ,for causing thetsignal' energyin. said taudio circuit to said dictating machine to beat a.red1iced1e1vel. when .=said control means .isfin stop positi'on;

2.; Irina! dictationrrecording system inclndi'ng a ..dibtat-. inggmachinet andia ;dictators microphone and-lreceiver: thewombinationof. tantaudio circuit for connecting said; microphone and receiventto said ;.dictating; machine, saidI. audios circuit including-. serial1y therein-ta transmission delay; device for retarding the transmission: .ofsall signals to fedt'to said .dictating machine-tfby apredetermined:periodp means responsive to voice fenergy spoken: into-said micro-.- phone :for a starting said= xdictating. machine within' a. PIPE--- determinedv time-tdelayperiod ;less than; said -.first-men tioned period; and means operatively coupledwith said starting means for :feeding; a. warning sign'al tot-said tl'fi'v ceiver :when said dictating-machine. .is i stopped .cand-z for concurrently reducingg then-level-wofe said warning signal fed .toksaid ;transmission-delay device-- 3; Inna dictation-recording system" including asdic-tat ing gmachinehaving ,:a revolvable: :record support, an rem-- cord-:cooperable ztranslatingidevicarandtdrive means for t causinggthe-l translating -;device Ox scan: asrecord on said supportnthe combination ofaadictator s :statiomincluding, a receiver and microphone; an: audio-icircuitfor-connect ingsaidiimicrophonew and .receiveratoai said; dictatinggames."- chine including ans amplifiermand :transrnission-delay device;;. said:zdelay device.- comprisingi;awmoving endless, 55

magnetizable record member --and recording, reproducing andt.;erasingr;heads positioned therea-long-in sequence whereby energy: fed to ;said rEdictating J machinewviaisaidt. delay device is delayedzby thettransit time of thesmagnetic" record tnnemberxfromntthe :recordingi, headn-to the reprosducingaheadfia start 'stopmelay for said:drive means nor-- mally-inxstop iPOSiiZlOlI-Jfifld operablecto start-i position by; signals: in; said audio icircuittlnpon i .elapse.-.of-. a--p1;edeter-. minedi delay period following tithe ;:instant t Ithe dictator:

speakssin'to .said :microphone; said-r1 delay period-.-.being-.;65

lessizthant said transit ztime in said; transmissions-delay; device whereby said 'clriye'means'tis started before audio 5 attennatingrelement inTs'aid-Jaudiocircuit beyond. the point where the warnin'g signal isi fedrthereinto' and means cont-L trolled i byi s'a'id: start-stop relay -:for shorting out saidnat tenua'ting e'lement whenrsaidrelay is in start position;

6." The-combination setforthllin claim-5 wherein'lsaid attenuating element isa condenser iserially 'connected ini said audiocircuit i andwherein said warning isi'gnal is composed of frequency components in theloweraudi'o spectrum, said' conde'nser having =a -value' adapted to at tenu'ate' substantially the transmission of the loweraudio frequency-componentsiand to transmit without substantial att'enuation the' higher audio frequency components,

7. In a dictation-recording system including 'a -dictat' ing 'machinehavin'g a recording circuit 'anda drive-mecha= nis'm; ,and a dictators station including a =-handpiecepro= vidd with a' receiver and l a 1 microphone: the combina'etion of-an* audio circuit for connecting said microphone to said recording circuit; said andio circuit inchidiiig seria'lly' therein a transmission-delay gdevice comprising a continuously-moving; endless magnetic" record member 0 andfarecordi'ng "head; reproducing 'head anderase *head' spaced"sequentially therea-long for 'recordingconstantly signals fromsaid. microphone and de'layin'g'the transmis sionlthere'of'by the time of transit of the record member from the recording headto the'reproducin'g 'head; an electromagnetic start-stop device for said drive 'mechanism;.means including-an amplifier for connecting said" microphone to said fstart-stop devicefor. operating the device to start position responsive to voice energy spoken into-said microphone above a given threshold'leve'lfthei operationnof said device being, characterized by'a' delay" substantially Iessthanthetransit time characterizing Jsai'd transmission. device; means controlled by said start-stop devicefor. -.fe'eding a warning signal into said "audio circuit. aheadiofi said transmission-delay device for reproduction by said receiver to apprise the dictatortwhen saiddrive mechanism is stopped, said warning" signal being recordedrbysaid.transmission-delay".devic'e while said drive mechanism is-stopped and/being tfed toand'recordedtb'y saidtdictatingsmachine for annoment ahead of. the.arrival of a voice signahinitiating operation ofIsaid to "depress the :warning signals. recordedwby .the transmission-delay.;,device;to 'a 'level below the'threshold ofnandibility; while-asaidi'drive :mechanism is stopped and for..-

restoringijthe 'levelz .of. the \signals recorded" by, said trans-t missionsdelay deviceto normal while said drivetmechw bio-references cited.

Non-Patent Citations
1 *None
Referenced by
Citing PatentFiling datePublication dateApplicantTitle
US2994746 *Sep 19, 1957Aug 1, 1961Mc Graw Edison CoAutomatic recording machine
US3014991 *Jun 10, 1958Dec 26, 1961Mc Graw Edison CoDiscriminatory control network for recording systems
US3028454 *Apr 20, 1959Apr 3, 1962Kohorn Henry VonSelective recording of continuous information
US3132213 *Jan 30, 1961May 5, 1964Dictaphone CorpAutomatic volume control system for a dictating machine and the like
US3243250 *Mar 5, 1964Mar 29, 1966Hauser RaimundArrangement for the recording and reproduction respectively of sound films
US3253689 *Apr 7, 1964May 31, 1966Jack M ThompsonInsurance vending machine
US3647985 *Jun 22, 1970Mar 7, 1972IbmTone-actuated dictation systems with voice buffer option
US7575789Jun 29, 2005Aug 18, 2009E.I. Du Pont De Nemours And CompanyCoated pipes for conveying oil
US7871684Jul 9, 2009Jan 18, 2011E. I. Du Pont De Nemours And CompanyCoated pipes for conveying oil
US8211497Oct 27, 2009Jul 3, 2012E. I. Du Pont De Nemours And CompanyProcess for forming a nonstick surface on the interior surface of a pipe
US8383199Jul 9, 2009Feb 26, 2013E. I. Dupont De Nemours And CompanyProcess for lining the interior surface of a metal pipe for conveying oil
US8685493Jun 1, 2012Apr 1, 2014E I Du Pont De Nemours And CompanyProcess for forming a non-stick surface on the interior surface of a pipe
US8776837Feb 21, 2013Jul 15, 2014E I Du Pont De Nemours And CompanyCoated pipes for conveying oil
U.S. Classification369/14, 369/60.1, 369/47.42, 369/29.1
International ClassificationH04M1/64
Cooperative ClassificationH04M1/64
European ClassificationH04M1/64