US2152470A - Wave signaling system - Google Patents

Description

Magda 28, i939. J. F. FARRINGTON ZSZA'@ WAVE SIGNALING SYSTEM Filed April 18, ,19354 2 Sheets-511661 l ATTORNEY March 28, 1939. J. F. ARRINGTON WAVE SGNALING SYSTEM Filed April 18, 1935 z'sneets-sneet 2 lNVENTOR UIOOOQQOI Patented Mar. Z8, 1939 PATENT OFFICE WAVE sTGNALmG SYSTEM John F. Farrington, Flushing, N. Y., assignor to Hazeltine Corporation, a corporation of Dela- Ware Application April 18, 1935Serial No. 18,949

25 Claims.

My invention relates to wave-signaling systems, and more particularly to such systems including provisions for reducing the effect of transient electrical disturbances, While at the same time favoring the transmission or reception of desired signal waves.

In the use of Wave-signaling receivers of either the space-radiation or wired type, considerable difficulty is often experienced from electrical disturbances or transient pulses of considerable magnitude originating external to the receiver and transmitted to the input terminals thereof along with the signal waves. Such transients may be of natural origin, as lightning discharges, or the like, associated with local thunderstorms or atmospheric disturbances; or such transients may be of artificial origin arising from arcing at leaky insulation points on power transmission lines, from sparking at motors, switches or sliding contacors of electric railways, household or factory electrical equipment, or the like, or from ignition systems of internal combustion engines or other well known sources too numerous to recite.

Such electrical disturbances are usually induced direct-ly on the receiving antenna of a space-radiation system or upon the transmission conductors of a wire system, and, although usually transient in character and of short individual duration, the proximity of their source to the receiver may result in very large amplitudes of such disturbances relative to the intensity of the desired signal. This is particularly true when such a receiver is utilized for receiving waves of 35 widely different intensity, as from remote and local stations. Electrical disturbances, such as previously mentioned, may be regarded as possessing component waves of frequencies to which the receiver is tuned. Therefore the selective 40 circuits of the receiver pass these waves to the final detector where they are converted to audio frequency waves which pass through the audio vcircuits and appear as noise in the output in direct competition with the desired signaling (Cl. Z50-20) received signal waves, such arrangements have necessarily had a time constant sufilciently high to prevent their following the modulation envelope of the signal carrier-wave and. hence, have not ordinarily been suilciently rapid in their operation to reduce the transmission or reproduction of such transient electrical pulses of short duration.

It is an object of my invention, therefore, to provide a wave signal-translating or receiving circuit which shall be substantially free from the undesirable characteristics described above and which will provide satisfactory signal translation or reproduction even in the presence of disturbing lelectrical transients.

It is another object of my invention to provide an improved wave signal-translating or receiving system by means of which electrical transients or pulses received at the input circuit of the system and of comparatively large amplitude relative to the desired signal are substantially suppressed.

It is a further object of my invention to provide an improved wave signal-translating or receiving circuit in which there is included provision for rendering the signal channel substantially inoperative during intervals when the magnitude of an electrical disturbance trans-- mitted thereto exceeds by an appreciable amount a predetermined relationship to the desired signal. l'

It is a still further object of my invention to provide an improved signal-translating or reproducing system subject to the reception of signals of variable intensity including provisions for controlling the amplification characteristics of the system to compensate for such variations in intensity of received signals and liior maintaining the signal at the most favorable level to eect a suppression of disturbing electrical transients.

While my invention is of general application, it is described hereinafter as embodied in a radio broadcast receiver including conventional modulated carrier-wave selecting, amplifying, and signal-detectingcircuits followed by a signal-frequency amplifier. In accordance with my invention, a vacuum tube or tubes of one or more of the translation stages of the system is provided with a control electrode which, for normal or maximum signal strengths, is biased at or near the point of the tube characteristic beyond which the ampliiication of the tube is sharply reduced. A biasing voltage is derived by rectifying input waves either by certain of the active electrodes of the tubes of the system or by auxiliary electrodes or tubes, and this biasing voltage is applied to the control electrode of a noise-controlling tube. The normal bias of this control electrode may consist solely of a fixed bias voltage or a fixed bias plus the rectified voltage just described. In either case the total biasing voltage corresponding to maximum signal strength is just short of providing a cuto of the noise controlling tube. If the total input to the system; that is, the signal plus the disturbing electrical transients as translated or amplified by the system, substantially exceeds the normal maximum signal input to the rectifying means, a voltage derived from the signal wave by rectification, as described, and impressed upon the control electrode is effective to bias the control electrode of the tube to cut off and substantially suppress-not limit-the transfer of the signal and/or noise through the system; that is, to reduce the signal-translation eiiiciency of the system to a very low value. In case the biasing voltage of the control tube consists solely of a fixed bias voltage, no additional rectitled voltage is added thereto until the total input to the system exceeds the normal signal intensity.

The time constant of the biasing control circuit just described is preferably suiljiciently small to avoid unnecessary lengthening of the duration of blank" spaces in the chain of reproduced signals, or the program, beyond the interval actually occupied by the undesired electrical disturbances.

In accordance with a further feature of my invention a system as described above is provided with an automatic amplification control arrangement for maintaining the desired signal input to the noise suppressor substantially constant, irrespective o'f the amplitude of the inv coming carrier wave, to enable the system to operate with a m'ost favorable ratio of signal amplitude to that of the disturbing electrical transients.

For a better understanding of my invention, together with other and futher objects and features thereof, reference is Lad to the following description taken in connection with the accompanying drawings, and its scope will be pointed out in the accompanying claims.

Fig. 1 is a schematic diagram of a complete radio broadcast receiver of the superheterodyne type including a schematic representation of a circuit for suppressing electrical disturbances in accordance with my invention; Fig. 2 is a detailed circuit diagram of one circuit arrangement for suppressing electrical disturbances shown schematically in Fig. 1; Fig. 3 is a detailed circuit diagram of a modified form of the system of Fig. 2; while Fig. 4 is a circuit diagram similar to Fig. 3 but modified to provide an output circuit employing only a single tube.

Referring now more particularly to Fig. l of the drawings, there is schematically shown a superheterodyne type of radio broadcast receiver,

embodying my invention in which radio-frequency signal-modulated waves are intercepted by an antenna Il and supplied to a radio-frequency selector and amplifier Ii, the antenna circuit being completed by a ground connection I2. The output of the radio-frequency selector and amplifier Il is impressed upon theinput of an oscillator-modulator II by means of which the radio-frequency currents are converted into signal-modulated intermediate-frequency waves. The intermediate-frequency waves are further amplified by an intermediate-frequency ampliner Il and impressed upon the input of a second detector which is included in a unit 2l. 'I'he unit 20. includes also a conventional'arrangement for deriving a unidirectional voltage variable in accordance with the average amplitude of the received carrier wave and may include, further, any desired number of audio-frequency amplifying stages. The unidirectional voltage developed by the unit 2l may be applied, as indicated, to the radio-frequency ampliiier I4, oscillator-modulator il, and intermediate-frequency amplifier il automatically to control the amplification of these devices to maintain the signal output of the unit 2l within predetermined limits, as is well understood in the art. While such an automatic volume control is effective to maintain the signal output of the unit within predetermined limits, irrespective of the variations in intensity of the received carrier waves, such a control does not effect an exact levelling of the signal. 'I'ne audio-frequency currents developed in the unit 20 are transferred through transformer 2l to the terminals A and B of the noise interference reduction circuit 22. The noise interference reduction circuit which constitutes the present invention will be described more particularly hereinafter, The output terminais A', B of the noise-interference reduction circuit 22 are connected to the power ampliiler by which the audio-frequency signals are further ampliiled and transmitted to the sound reproducer or loudspeaker 2l.

The various portions of the receiver shown in Fig. l, with the exception of the noise-interference reduction circuit 22, may be of conventional type and, since they constitute no part of the present invention, a further description thereof is deemed unnecessary.

Referring, now, to Fig. 2, there is illustrated ay preferred embodiment of the noise-interference reduction circuit indicated at 22 in Fig. l. The terminals, A, B, X, A' and B' correspond with similarly indicated terminals in Pigs. i. Essentially, this circuit consists of a two-stage audiofrequency amplifier comprising a first vacuum tube VTi having an input electrode connected to theinput circuit AB through a manual volume adjusting potentiometer P1 and coupled through a transformer Ti to a pair of vacuum tubes VT: and VI: connected in push-pull relation. The output circuit of the push-pull amplifier comprising tubes VIz and VT: is coupled to the output terminals A', B through a transformer T: and a second manually adjustable volume control potentiometer Pz. The tube VT1 may be of any suitable type, though I have shown a pentode, in which case the amplification control bias from the terminal X may be impressed upon the outer or suppressor grid through a resistance Re and filtering condenser C4 which have a time constant of sumcient magnitude to prevent their following the ordinary variations of signal intensity at the modulation frequency and yet sufficiently small to permit control of the ampliilcation of the tube VT1 without undue time lag. Biasing resistors Rz, Ra and R4 may be included in the cathode circuit of the tube VT1 in conjunction with audio-frequency by-pass condenser Cz. A suitable biasing voltage for the signal input electrode may be derived from these resistors, as shown.

The second stage of the noise-reducing circuit comprises a unique form of push-pull amplifier, including vacuum tubes VT: and VTi. Again, these tubes may be of any suitable type, but when of the pentode type, as shown, the input circuit comprising the secondary winding of the transformer Ti may be, connected to their inner control electrodes. This winding is mid-tapped in a conventional manner and connected to ground through a circuit comprising a resistance R and a condenser C in parallel and proportioned as described in more detail hereinafter. A resistance Rv may be connected across the secondary winding of T1 to obtain a substantially fiat frequency-gain characteristic within the operating limits of the circuit. The control of the tubes VTz and VTa for the reduction of the interfering electrical disturbances may be eiected through the outer or suppressor grids, which are connected to ground through the circuit R-C. Positive voltages for the tubes VT1, Vlz and VT: may be supplied from any suitable source, indicated as +B, through resistors R1 and Rs, respectively, shunted by audio-frequency by-passing condensers C1 and C3, respectively. AA bleeder resistance Re may be connected between the cathodes of the tubes VT2 and VTw and the mid-point of the primary winding of output transformer T2 for the purpose of maintaining supply voltages to the tubes substantially independent oi' the anode current of the push-pull amplifier.

Disregarding the circuit R-C for the moment and assuming suitable bias voltages to be supplied to the control and suppressor grids of the tubes VTz and V'I'a, the above-described circuit operates as a conventional two-stage audio-irequency amplier in which variations in the intensity of the signal translated through the amplier circuit, due to variations in intensity of the received carrier wave, are minimized by the amplification control bias applied` through the terminal X to the tube VT1 of the first stage. It will be noted, however, that the cathodes of the tubes VTz and VTs are connected to ground through the biasing resistor R4 so that the signal input grids of these tubes are normally maintained at negative voltage, with respect to their cathodes, by the amount of the voltage across the resistance R4. The values of resistances R2, R3 and R4 are so chosen that the magnitude of the bias voltage across resistor R4 is greater than the maximum value of the signal input to the tubes VTz and VTa under normal operating conditions. With such an arrangement the signal input electrodes of the tubes VTz and VTa are maintained continuously negative so that no grid currents flow in their respective circuits.

Upon the occurrence of an electrical transient or disturbance oi considerable magnitude relative to the desired signa?, theinstantaneous ampli- .tude 'of the voltage input to the inner or signal grids of the tubes VTz and VT: becomes greater than the bias voltage of the resistor R4 with the result that a rectified current flows in the circuit RC, developing a bias voltage across resistor R which is impressed upon the outer or suppressor grids of the tubes VTz and VTa, which may be termed the control electrodes. 'I'he normal biasing voltages of the several control electrodes of the tubes VTz and VTa are so selected that these tubes are normally and constantly eilicient in the transfer of received signals but operate near their cutoi value for normal maximum signal intensity. Therefore, any increase in the bias voltage impressed upon the control electrodes of the tubes VTz and VT; operates instantaneously to cut off these tubes or to reduce materially their amplication and, thus, substantially to reduce the signal-translation efficiency of the circuit and to suppress not only the electrical transient or disturbance but the signal as well. Because o1' this complete suppression of the signal, it is desirable that the bias on the contrfl lelectrodes of the tubes VT: and VT: be dissipated quickly after cessation of the electrical transients or disturbances. To this end the time constant oi.' the circuit RC is made small, and may be, for example, of the order of .001 second. It is also desirable that this time constant shall be suiliciently small to allow the noise suppression control to follow the modulation envelope to ensure rapid response to audio-frequency disturbances. In certain instances the condenser C may be completely omitted without impairing the operation of the circuit.

It isdesirable that full wave rectification of the input wave shall take place in order that a control voltage shall be available to block out noise, regardless of its polarity. The use of the push-pull amplifier circuit also prevents generation of an appreciable voltage wave'in the secondary winding of the transformer T2 due to cutting off of the anode currents by the noise suppression control.

The suppression of the disturbing electrical transients is most effective when the amplitude of the normal maximum signal is held only slightly less than the magnitude of the bias voltage across the resistor R4, that is, the bias of the signal input grids of the tubes VTz and VTs, this relation corresponding to a maximum ratio of signal to disturbing transient. Therefore, it is important that changes in the amplitude of the incoming modulated carrier wave impressed on the receiver shall not produce appreciable change in the amplitude of the signal applied to the grids of noise suppressor tubes. By the application of the automatic amplification control bias through the terminal X to the control electrodes of the tube VT1, the levelling oi the signal intensity normally accomplished in the radio-frequency portion of the receiver is supplemented to minimize variations in signal intensity as applied to the control electrodes of the tubes VT: and VTa. If the levelling of the signal input to the pushpull stage comprising the tubes V'I'z and VTs approaches the ideal; that is, is suiciently 'close to constant level for practical purposes, 'within the normal operating limits of the system, the potentiometer P1 may be set permanently so thata 100% dependent upon the percentage imodulaticiirof` the particular station being received.

In the arrangement of Fig. 2, the electrodes utilized to control the suppression of electrical transients or disturbances are normally biased by a fixed voltage of such magnitude as to operate the tubes in the push-pull stage near the cutoff. No additional biasing voltage is supplied to these control electrodes until the amplitude of the signal input to the tubes V'I'z and VT; exceeds the bias across the resistor R4, and grid rectiiication takes place. In the arrangement of Fig. 3, on the other hand, the fixed negative bias applied to the conrol electrode for suppressing electrical transients is supplemented continuously by an additional biasing voltage varying with the amplitude of the input to the terminals AB and, when the sum of these two bias voltages exceeds a predetermined value, the tubes V'Iz and VTs operate to cut off the transmission of a signal.

In the arrangement of Fig. 3 this latter result is effected either by means of an auxiliary rectifying tube or, as shown, by auxiliary electrodes of a duplex amplifying and rectifying tube VT4 replacing the tube VTi of l'ig. 2. In this case also the transformer T1 of Fig. 2 is replaced by transformer T: having a tertiary winding connected to the rectifying electrodes of the tube VT4 in circuit with the resistance R and condenser C across which is developed the supplemental biasing voltage applied to the suppressor grids of the tubes VT: and VTs. With this arrangement the bias of the signal input electrodes of the tubes VT: and VT: is not critical and they may be connected to any suitable point in the biasing voltage divider Rz, Ra, Ra in accordance with the desired operating characteristics of the system.

The operation of the apparatus of Fig. 3 is similar to that of Fig. 2 described above, with the exception that the electrical constants of the circuit are so chosen that, under normal operating conditions, the xed negative bias applied to the suppressor grids of the tubes VT: and VT: plus the rectined biasing voltage appearing across the resistor R, corresponding to maximum signal input, operates the tubes VT: and VT: just short of their cutoff point. Under such conditions, the occurrence of electrical transients or disturbances causes an increased rectied bias to appear across the resistor R. which, with the fixed negative bias described, operates the tubes VT: and VT: beyond their cutoi! point to suppress the electrical transient.

'I'he same factors determine the selection of constants of the resistor R and condenser C and/or the omission ot the condenser C, as apply to the circuit of Fig. 2 described above. With the exception that the biasing resistors Rz and R: are in the common cathode circuit of the tubes VT: and VT: rather than in that of the tube in the rst stage, the remainder of the circuit is similar to that of Fig. 2 and its principles of operation are the same.

'Ihe circuit of Fig. 4 is similar to that of Fig. 3 with the exception that the second stage is modified in such a way as'to secure the advantages oi a push-pull amplifier in the suppression of electrical transients by means of a single tube VT. The screen and anode circuits of the tube VTs, shown as pentode type, are connected in push-pull relation with the output transformer T2. A resistor R and condenser C are preferably included in the anode circuit to balance the screen and anode circuits and prevent distortion in the push-pull output circuit. In this case also the biasing voltage effective to suppress electrical transients is applied to the inner control grid of the tube V'Is. which is normally used as a signal input grid, while the signal input circuit from the transformer T: is connected to the outer or suppressor grid. 'I'he operation is otherwise similar to that of the circuit of Fig. 3.

As in the arrangement of Fig. 2, the potentiometer P1 in the circuits of Fig. 3 and Fig. 4 is ordinarily permanently adjusted so that the maximum signal input is effective to operate the tube or tubes of the nnal audio-frequency amplifying stage, in which electrical disturbances or transients are suppressed, substantially at the cutoff point, while the manual volume control of the receiver is effected primarily by the potentiometer Pz.

In each of the above arrangements it is preferable, for best operation of the transient suppression circuit, that no limiting action on the transients or noise pulses shall occur at the receiver preceding the push-pull amplifier in which the control is effected. The transformer ratios, the operating voltages on the several electrodes of the tubes, and the signal input amplitude are preferably suitably chosen with this point in mind.

While my invention has been described as embodied in a circuit arrangement utilizing particular types, of tubes with particular arrangements and connections of control electrodes. it is to be emphasized that these particular arrangements of tubes and electrodes are of no material significance and that any. equivalent tubes. either single or duplex, or any equivalent electrode connection may be employed in the practice of my invention. Furthermore, while the biasing voltages applied to the control electrodes, to determine the operating characteristics of their associated tubes and circuits and to limit the grid rectification in the circuit of Fig. 2, are shown as being derived from biasing resistors in the space current paths of the tubes. it will be apparent that these voltages may be derived from batteries or any other suitable source of direct voltages. Also, while my invention has been described as applied to the audio-frequency portion of a radio receiver, it is obvious that it may be used in connection with thel radio-frequency or intermediate-frequency portions of such a receiver by choosing appropriate values for the circuit elements. Similarly, it may be applied to signal-translating systems forming a portion of a wire communication system operating at either audio or carrier frequencies for the reception or transmission of wave signals.

While I have described what I at present consider the preferred embodiments of my invention, it will be obvious to those skilled in the art that various changes and modifications may be made therein without departing from my invention, and I, therefore, aim in the appended claims to cover all such changes and modifications as fall within the true spirit and scope of my invention.

What is claimed is:

1. vIn a wave-signaling system, a signal-translating stage having signal input and output circuits and normally efilcient in the translation of input signals, means for controlling the amplitude of the desired signal input thereto to maintain the maximum amplitude thereof near and below a predetermined critical value, rectier means coupled to said input circuit and having a time constant such that it follows substantially instantaneous variations in amplitude of the input current, a source of biasing voltage connected in circuit with said rectifier means in opposition to the rectified voltage developed thereby, whereby rectification takes place only when the amplitude of the input current exceeds said predetermined value. and means for reducing the efficiency of said signal-translating stage in response to the output of said rectifier means.

2. In a wave-signaling system, a signal-translating stage having signal input and output circuits and including a vacuum tube having a plurality of electrodes, means for controlling the amplitude of the desired signal input thereto to maintain the maximum amplitude thereof near and below a predetermined critical value, and means coupled to said input circuit for deriving therefrom a biasing voltage variable with the total current in said input circuit and for applying the same to an electrode of said tube, said means having a time constant auch that said biasing voltage is responsive to the instantaneous amplitude above said predetermined value of the input current.

3. In a wave-signaling system, a signal-translating stage having signal input and output'circuits and including a vacuum tube having a plurality of electrodes including input and output electrodes, means for controlling the amplitude of the desired signal input thereto to maintain the maximum amplitude thereof near and below a predetermined critical value, said translating stage including rectifier means vcoupled to said input circuit, a parallel connected resistor and condenser included in the direct-current circuit of said rectiiier and having a time constant suiiiciently small that the direct voltage thereacross approximately follows the envelope of the signal input to said input circuit, and a circuit for impressing the direct voltage of said rectifier means upon a control electrode of said vacuum tube, the operating voltages of the electrodes of said tube being so related that the gain thereof is substantially reduced only for values of said direct voltage corresponding to amplitudes of input current in excess of said predetermined value.

4. In a wave-signaling system, a signal-translating stage having signal input and output circuits and including a vacuum tube having input and output electrodes and an axuiliary control electrode, sources of operating voltages for said electrodes, said sources being so proportioned that an increase of the operating voltage of said auxiliary electrode beyond its normal value effects a sharp reduction in the gain of the tube, and means comprising a rectier coupled to said input circuit and including a parallel-connected resistor and capacitor in the direct current path thereof for deriving therefrom a biasing potential and for applying the same to said auxiliary electrode, said means having a time constant such that said biasing potential is dependent upon the instantaneous amplitude of the input current, whereby the translation eiciency of the system is sharply reduced when said instantaneous amplitude exceeds a predetermined value` 5. In a wave-signaling system, a signal-translating stage having signal input and output circuits and including a vacuum tube having input and output electrodes and an auxiliary control electrode, said input electrode being connected to said input circuit, a source of constant bias voltage for said input electrode whereby current iiows in its associated circuit only for amplitudes of input voltage exceeding a predetermined value, impedance means in the circuit of said input electrode traversed by any rectified current therein, and means for impressing the direct voltage developed thereacross on said auxiliary electrode, whereby the translation eiliciency of the system is reduced when the instantaneous amplitude of the input current exceeds said predetermined value.

6. In a wave-signaling system, a signal-translating stage having a signal input circuit norvalue, means responsive to the` amplitude of the desired signal input to said vstage for maintaining the maximum amplitude thereof near and` below the predetermined critical value, and` means for increasing the bias beyond said critical value upon the occurrence of an electrical transient at said input circuit.

7. In a wave-signaling system, a signal-translating stage having a signal input circuitV nornally subject to disturbing electrical transients and an output circuit, means for controlling the amplitude of the desired signal input thereto to maintain the maximum amplitude thereof near and below a predetermined critical value, said signal-translating stage being normally eilicient in the translation of currents from said input circuit to said output circuit, full-wave rectier means for deriving from said input circuit a biasing voltage dependent upon the instantaneous amplitude of currents therein, and,v means for reducing the efiiciency of said translating stage only for biasing voltages corresponding to input currents exceeding said predetermined value, whereby said reduction is eilected substantially instantaneously irrespective oi polarity of said transient or said signal.

8. In a wave-signaling system, an input circuit, an output circuit, a pair of vacuum tubes each having a plurality of electrodes including input and output electrodes interconnected with said input and output circuits, respectively, to form a push-pull signal-translating stage, said translating stage including means coupled to said input circuit for deriving therefrom a biasing voltage dependent upon the instantaneous amplitude of the currents therein, and means for applying said biasing voltage with like polarity upon corresponding electrodes of said pair of tubes whereby the efiiciency of said translating stage is reduced only for control voltages corresponding to input currents exceeding a predetermined amplitude and whereby disturbing impulses due to the sudden interruption of the space currents of said tubes are balanced out.

9. In a signal-modulated carrier wave receiving system, means for selectively admitting and amplifying desired signal waves, means for detecting said amplified signal Waves, a signal-reproducing device, a signal-translating stage interconnecting said detecting means and said device, means for controlling the amplification of said amplifying means in inverse relation to the average intensity of the received carrier signal Waves to maintain the maximum amplitude of the desired signal input to said translating stage near and below a predetermined critical value, and means responsive to the instantaneous amplitude of the total current in the input circuit of said signal-translating stage for suppressing the translation of all currents through said signaltranslating stage only when the instantaneous amplitude of the input current thereto exceeds said predetermined value.

10. In a wave-signaling system including a signal-translating stage having input and output circuits, the method of receiving and translating desired signals having a wide range of amplitudes while suppressing disturbing electrical transients associated with said signals, which comprises variably amplifying the received signais and transients to raise any average amplitude of the desired signal to the same predetermined level, normally translating said amplified signals from said inputcircuit to said output circuit at constant eili'ciency and substantially suppressing the translation of all signals and transientsfrom said input circuit to said output circuit ,when the instantaneous amplitude of combined signals and transients exceeds said prede- J tensity of the received carrier wave, controlling Ylil said amplification in accordance with the magnitude of said biasing voltage to maintain the average amplitude of said audio-frequency currents substantially constant, amplifying said audio-frequency currents, deriving from said signal waves and transients a biasing voltage de; pendent upon the instantaneous value of said audio-frequency currents, and reducing'the am-j; pliflcation in one of said amplifying steps substantially to zero for values of said last-mentioned biasing voltage corresponding to instantaneous amplitudes of said audio-frequency currents substantially exceeding said constant amplitude.

l2. In agwave-signaling system, an input circuit. an output circuit, a pentode vacuum tube amplifier, said input circuit being connected to the suppressor grid of said tube. the anode and screen grid of said tube being connected in pushpull Yrelation to said output circuit, means coupled to said input circuit for deriving therefrom a biasing voltage dependent upon the instantaneous amplitude of the currents therein, and means for applying said biasing voltage to the signal grid for reducing the emciency of said translating stage lonly for biasing voltages corresponding to input currents exceeding a predetermined amplitude.

13. In a wavefsignaling system, an input circuit, an output circuit, a pentode vacuum tube ampliiler, said input circuit being connected to the suppressor grid of said tube, the anode and screen grid of said tube being connected in pushpull relation to said output circuit, means for equalizing the currents in the anode and screen grid circuitsJ auxiliary rectiner means coupled to said input circuitand having a time constant such that it follows substantially instantaneous variations in amplitude of the input current, and means for applying the output of said rectifier means as a bias to the signal grid of said tube for reducing the emciency of said translating stage only for biasing voltages correspondingto input currents exceeding a predetermined amplitude.

14. A wave-signaling system, comprising a plurality of cascade-connected signal-translating stages each including input and output circuits,

the hrst of said input circuits being normally sub- Ject to the desired signals having a wide range of amplitudes and to disturbing electrical transients, one of said stages other than the nrst comprising a vacuum tube having a plurality'of electrodes including input and output electrodes coupled respectively to its associated input and output circuits. said tube beingcof a type effective substantially tocut oi! the transmission of signals upon the btasing of one of said electrodes in excess of a critical value, means responsive to the desired signal input to the system for maintaining the signal input to said one of said stagessubstantially constant, and means including full wave rectiner means coupled to the input circuit of one of said stages other thanthose following said one of send stages and responsive to the instantaneous amplitude of the total inputfcurrcnt in the as` sociated input circuit for normally biasing said one of said electrodes near said critical value and for increasing the bias thereof beyond said critical value upon the occurrence of an electrical transient in said system.

15. In a wave-signaling system, a signal-translating stage comprising input and output'circuits and a vacuum tube having a plurality of electrodes including input and outputelectrodes coupled respectively to said input and output circuits, said' tube being of a type effective substantially to cut ofi.' the translation of signals upon the biasing of one of said electrodes in excess of a critical value, impedance means comprising a parallel-connected resistor nand capacitor connected to impress a bias voltage on said one of said electrodes, and means including a full wave rectiiler coupled to said input circuit for developing a bias voltage across said impedance means variable with theY instantaneous amplitude of the total current in said input circuit and which exceeds said critical value upon the occurrence of an electrical transient in said input circuit.

18. Method of reducing the effects of parasitic disturbances in a signaling system, includiigia."

circuit the conductivity of which dependsupon the maintenance of an electron stream between elements in said system, which comprises impressing static affected signal waves upon said system, continuously rectifying the components of all amplitudes of a portion of said waves, and utilizing the rectified components thereof to concomitantly vary the conductivity of said circuit responsive to the receipt of waves of a desired amplitude and to interrupt the conductivity of said circuit for periods correspondingsubstam tially to the'actual duration of parasitic components having an amplitude greater than a certain predeterminedY value.

17. In a signaling system, the combination with asource of signal energy, a circuit the conductivity of which depends upon the maintenance of an electron stream between elements in said circuit and means for impressing signal energy from said source upon said circuit, of means for instantaneously controlling said electrcn stream in accordance with the amplitude oi the energy impressed upon said circuit from said source, said means comprising a non-signal bearingcelectrode in the path of said stream, a device connected between said source and said circuit for converting a portion of said energy of all amplitudes into a potential capable of increasing the conductivity of said electron stream in response to signal intensities below a predeterminedmmaximum, and into a potential capable of interrupting the conductivity of said electron i. stream in response to intensities above said maximum, and a conductive connection for said potentials from said ldevice to said non-signal bearing electrode. l

i8. In a signaling system, a normally operative electronic repeater, means for impressing static affected bearing waves upon said repeater, means forrectifying at least a portion of al1 of said waves. 'and means-responsive to rectified static components of said waves of an amplitude greater than a predetermined value for disabling said repeater for periods corresponding substantially to the actual duration of said components.

19. Method of reducing the effects of parasitic disturbances in a signaling system, including a normally operative electronic repeater, which comprises impressing staticy affected bearing waves upon said repeater, simultaneously and continuously rectitying the components of all amplitudes oi.' aportion of said waves and utilizing the rectified components thereof to disable said repeater for periods corresponding substantially to the actual duration oi' parasitic components having an amplitude greater than a certain predetermined value.

20. In a signaling system,` the combination with a source of signal energy, a translating cir- 'cuit the conductivity of which depends upon the maintenance of an electron stream between elements in said circuit and means tor impressing signal energy from said source upon said circuit, of means for interrupting said electron stream when the energy impressed upon said circuit from said source exceeds a predetermined intensity, said means comprising a non-signal bearing electrode in the path of said stream, a device connected between said source and said circuit for converting a portion oi' said energy of all amplitudes into a potential proportional to said energy. said potential beingcapable of interrupting said electron stream when said energy exceeds a predetermined value and a conductive connection for said potential from said converter to said non-signal bearing electrode, said device for converting a portion of said energy into a potential proportional to said energy being independent of the operation or the nonoperation of said translating circuit.

2l. In a signaling system, a normally operative electronic repeater, means for impressing static affected bearing waves upon said repeater, means for Vrectifying a portion of all of said waves, and means responsive to rectied parasitic components of said waves of an amplitude greater than a certain predetermined value for disabling said repeater for periods corresponding substantially to the actual duration of said components.

22. In a signaling system, a thermionie tube having at least two grids disposed between a cathode and an anode, a signal input circuit connected between the cathode and that one of the two grids remote from said cathode, means for rectifying the components of all amplitudes of a portion of the input circuit energy and means for continuously impressing upon the grid adjacent to the cathode a biasing potential proportional to the input circuit energy and oi.' such a value as to substantially block the ilow of electrons between said cathode and said anode only at such times as the input circuit energy exceeds a certain predetermined value.

23. Method of reducing the eiiects of static disturbances in a signaling system. including a control tube the conductivity of which dependsl upon the maintenance of an electron stream between elements of said tube, which comprises impressing static affected bearing waves upon said system, continuously rectifying the components of all amplitudes of at least a portion of said waves.. and utilizing the rectiiied components thereoi' to concomitantly vary the conductivity of said control tube responsive to the receipt of waves of a desired amplitude and to interrupt the conductivity oi.' said control tube for periods corresponding substantially to the actual duration of components having amplitude greater than a predetermined value.

24. A method of reducing the eilects oi static disturbances in a signaling system that includes a controlled tube whereof the conductivity depends upon the maintenance oi an electron stream between elements oi said tube, which comprises continuously rectifying, independently of a constant applied voltage, all amplitudes of at least a portion of the energy being transmitted through the system, applying said rectified energy to produce a voltage drop that is linearly proportional to the amplitude of said energy before rectification, and applying said voltage drop to the electron stream in said tube`to interrupt the conductivity of said tube for periods corresponding substantially to the duration of components of said alternating current having amplitude greater than a predetermined value.

25. A method of reducing the effects oi' static disturbances in a signaling system that includes a controlled tube whereof the conductivity depends upon the maintenance of an electron stream between elements oi said tube, which comprises continuously deriving a rectified current immediately from all the components of at least a half-wave of an alternating current. said rectied current thus having characteristics identical with the utilized portion of said alternating current, applying said rectified current to produce a drop in voltage that is directly proportional to the amplitude of said alternating current, and applying said voltage drop to the electron stream in said tube to interrupt the conductivity of said tube for periods corresponding substantially to the duration of components of said alternating current having amplitude greater than a predetermined value.

JOHN F. FARRING'ION.

CERTIFICATE OF CORRECTION.

nuxit ne. 2,152,1470. Maren 28, 1 959.

yJomx F. FARRINGTON.

It lis hereby certifiedl that error appears in the print-ed specification4 of the above numbered patent requiring correction as follows: Page 2, second column, line )42,'1'01 Wigs. reed Fig.; page 5, second column, line 39, for the word "electrodes"4 read electrode; pege 6, second column, line 66; page 7, first column, lines 1 and g5; and second column, line 6, claims 18, 19, 21, and 25 respectively, fior "bearing" read signal; andthat the said Letters Patent should be reno with this correction therein that the same may conform to the record of the case in the Patent Office.

'signed and sealed this 6th day or June. A. n. 1959.

Henry Van Arsdale (Seal) Acting4 Commissioner of Patente.

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