US2266154A - Thermionic valve circuits - Google Patents

Description

Dec.16,1941. AQ B UMLEIN 2,266,154

THERMIONIC VALVE CIRCUITS Filed March 1, 1940 2 Sheets-Sheet 1 INVENTOR. ALAN DOWER BLUMLE/N ATTORNEY.

THERMIONIC VALVE cmcums Filed March 1, 1940 4 2 Sheets-Shed 2 llnl IIH HIH IIHI INVENTOR. ALA/V DOM ER BL UMLEIN ATTORNEY.-'

PatentedDecl 156, V V

'rnnnmoNic VALVE omcurrs Alan Dower Blumlein, Ealing-liondomlingiand, assignor to Electric & Musical Industries Limx, England, a company of Great Britain ited, Hayes, Middlese Application March 1, 1940, Serial No. 321,616

In Great Britain February 25,1939 1 This invention relatesto thermionic valve cir- It 'isknown tovemploy the properties of delay networks in circuits. for generating electric signal pulses or effecting selection oi pulses of predetermined duration from a mixture of pulses.

'In particular, in the specification of co-pending United States Patent application Serial No. 193,401, now Patent No. 2,211,942, issued August 20,- 1940; it is proposed to use a delay network in an arrangement for separating frame synchronising pulses from line synchronising pulses. The line and .frame pulses are applied to two channels simultaneously and in one channel they are delayed by an amount greater cuits for controlling or producing electric pulses a as used, for example, in television systems. I

s Claims. (01. 178-44) bothin push-pull. By applying a saw-tooth waveform with a sharp leading edge to a delay network across which the two grids are connected, a pulse is formed in the anode circuit having a duration equal to the distance between the tappingson the delay'network. v i H In the preceding arrangements the delay networks are operated with correct terminations so that refiectionless working is obtained. It has .10

been found, however, that in certain cases economy of the length of thedelay network required and in most cases in the number of valvesrequired, can be efiected by a mis-terminating the delay networkso that use is made of the re -flected wave, the present invention having as its I .basis the use of the reflected wave for switching than the duration of a'line pulse but less than that of a frame pulse. The delayed and undelayed pulses are then applied to a hexode valve, a double diode or a double triode circuit, so that an output is obtained only when the pulses overto provide alternative forms of circuit arrangemerit for generating pulses of a required duralap in time, that is to say, at the occurrence of v a frame pulse.

Again, in the specification of co-pending United States Patent application Serial No.

202,452, now Patent No. 2,212,967, issued August 27, 1940, a circuitarrangement is described including. an impulse generator which is started and stopped by control impulses, the starting and stopping pulses originating from a single signal passing along a delay network. In one arrangement a'valve of a multi-vibrator is started into operation when a pulse passing through'a delay network connected across-the valves of the multi-vibrator reachesfa first tapping in the network and is stopped when the same pulse reaches a second tapping, a-square topped wave of the duration determined, by the delay between th tapp s beinggenerated;

Also in the specification of co-pending United States Patent application Serial No.-202,452 it is proposed to. produce a pulse of a shorter width than a controlling pulseby switching on a hex ode valve by the controlling pulse-applied to-its' inner grid and switching the valve off by anega- Further, in the specification of co-pendingderived, being applied to the control grids. An

"output can be taken from either anode or from purposes. The object of the present invention is tio'n and/or for separating mixedpulses and which efiect the economies referred tog.

According to the present invention a circuit arrangement includes a delay network connect-I- ed to a source of pulses and a switching device, said delay network having a termination such that an input pulse is reflected from the-end of trolled by the combined operation of the input the network, said switching device being conpulse and the reflected pulse.

Certain circuit arrangements according to the Y present invention for generating pulses of a re-.

quired durationand/or separating pulses of one 5 duration from pulses of another duration include a delay networkand means for feeding pulses to the delay network which isprovided with a tapping-or tappings from which the required pulses are derived, the-said delay network Bein misterminated at'the end remote from that to which the pulses are iedg'so that a ,pulse, which may be derived from an input pulse whichit is desired to. separate from pulses-ofshorter duration, is

developed by the combinedoperation .ofthe original- .pulse travelling -.down the delay network and 1,45, tive pulse delayed by a network the required time with respect to the first pulse, the delayed pulse being applied to the outer grid of the hexode.

the pulse reflected-from the remote 'end..- 1 One feature of 'thelinventionf con'sistsj'in terminatingthe delay net work at one end by' any substantially equal to thefcharacter-i' impedance istic impedance of the network and said 1111* lay'network is either short-circuited or open circuited fortrequencies in the operating range. In' order that the invention may be: more gpedance may be constituted, byy th'e source of pulses or by the load.- Afurtherifeaturepf the invention consists in arranging that at the end remote from. the source of input pulses,; thedefeet, alternative forms of pulse operated circuits embodying the invention will now be described by way of example with reference to Figures 1 to 4 of the accompanying drawings.

Referring to Figure 1 of those drawings, an arrangement is shown for generating a pulse of predetermined duration from an input pulse of longer duration. The arrangement shown might be used, for example, to develop a line synchronising pulse from a line frequency .saw-tooth waveform having a very steep leading edge, or from a pulse of longer duration such as the suppression pulse which normally commences slightly ahead of the synchronizing pulse and terminates slightly after. In Figure 1, a cathode follower valve I having its cathode resistance 2 connected to a negative point in a source of voltage supply feeds through a resistance 3 a delay network 4. The resistance 3, together with the internal impedance of the valve l and resistance 2, constitutes a generator, the impedance of which is sub stantially equal to the characteristic impedance of the delay network 4. Any other suitable form of generator may be used providing its impedance substantially matches the surge impedance of the delay network. The tapping point 5 in the delay network 4 is coupled through a condenser 6 to the control grid of an output valve 1 serving as a limiting device. The pulse required to be generated'can be taken from the anode circuit of the valve 1 at the terminal 8.

In the arrangement shown the valve I is arranged to produce a negative pulse at the terminal 8 on the application of a positive pulse from the valve 1. The condenser 6 and the resistance 9 connected between the control grid and cathode of the .valve 1 ensures that this valve is self-biasing, the time constant of the condenser/ resistance combination being long compared with the duraa valve would be effectively earthed for alternating currents. A pair of valves so connected would form an automatic limiting arrangement for pulse v amplitude.

The operation of the circuit described with reference to Figure 1 is as follows: The saw-tooth waveform or pulse of long duration fed from the valve l enters the delay network in the positive sense and on arriving at the tapping point 5 renders the valve 1 conductive. The pulse travels down the delay network and arrives at the far end which is short-circuited by a link I. The pulse is then reflected from this short-circuited end,

the sense of its voltage being reversed and on again reaching the tapping point 5, it will cancel the efiect-of the original positive voltage applied at this point, switching off the valve 1 and thus terminating the pulse available at the output terminal 8. The reflected pulse will travel on and be dissipated in the internal impedance of the input generator which, as previously indi-' cated, is matched to the surge impedance of the network 4.

The duration of the pulse available at the terminal 8, initiated at the point 5 by the input 7 clearly. understood and readily carried into efpulse and terminated at the same point by the reflected pulse will be substantially equal to twice input pulse by the amount of delay network between the generator and the tapping point. If the V tapping point were removed to the generator, no delay of course would be obtained.

If a saw-tooth waveform input is applied to the network and the long flank of the saw-tooth is uniform, the slow portion of the last reflected pulse will cancel the slow changing portion of the incoming pulse so that a substantially squared pulse will be taken from the point 5 subject to any slope due to the inevitable loss in the delay network. I

The circuit arrangement of Figure 2 illustrates a method of generating two consecutive pulses from a single saw-tooth pulse input. In Figure 2, the input valve l is shown driving the delay network 4 from its anode, a feed resistance ll, coupling condenser 12 and terminating resistance I3 forming in combination a generator, the irnpedance of which matches the surge impedance of the delay network 4. The waveform used by the British Broadcasting Corporation for the television transmission system at present in use constitutes an example of a case in which it is desired to produce two pulses from a saw-tooth. The waveform referred to is described in an article entitled The Marconi-E. M. I. Television System in the Journal of the Institution of Electrical Engineers for December, 1938, and commencing at page 758. In the case of the waveform referred to, two frame synchronising pulses are generated from a s le line frequency sawtooth wave with a steep rising wavefront.

Assuming the input signals to be applied with a quick change from negative to positive and a slow change from positive to negative in the delay network, thetwo valves l4 and I5 are so biased that the valve I4 is normally non-conductive and the valve 15 is conducting. The steep portion of the saw-tooth wave must be of sufficient amplitude after attenuation due to transmission in both directions along the delay network as to be about twice the discriminating bias applied to the valve i4. These valves operate in a similar manner to the pair of valves described in the speciflcation of co-pending United States Patent application Serial No. 269,397 previously referred to. Thus the quick rise of the saw-tooth pulse arriving at valve H from the tapping point It renders this valveconductive and the valve l5 non-conductive. The quick rise on arriving at the tapping point I'I renders the valve [5 conducting and consequently the valve l4 non-conducting, so terminating the first generated pulse. The quick rise is then reflected from the shortcircuiting linkl8 in reverse sense as regards its voltage and on again arriving at the point i! renders the valve l5 non-conducting and the valve l4 conducting. The reflected pulse then arrives at the point l6 rendering the valve l4 non-conducting and the valve 15 conducting and so terminating the second generated pulse. Finally, the reflected pulse arrives at the generator which as previously indicated constitutes a matched terminating impedance and is dissipated. The

double frequency pulse may be obtained from either of the anodes of the valves l4 and l5.

. As an example of the timing of the pulses in the arrangement shown in Figure 2, it is convenient to consider the synchronising pulses of the waveform in the Marconi-E. M. I, television system previously referred to. These pulses are required to be each of approximatelyf40 micro-seconds duration separated by intervals of micro-seconds. The delay between the tanning for the 1 valve l5 and the short-circuited end of the delay network should therefore be 5 micro-seconds and the delay between the two tapping points l6 and II should be 40 micro-seconds. The amount of delay between the generator and the tapping point It is determined by the relative phase of the input pulses and the required be- I ginning of the first frame pulse. Alternatively, I instead of generating the pulses, the generation may infact, consist of the intervals between the pulses and in this case the delay required between the tapping point l1 and the short-circuited end of the delay network would be micro-seconds, the delay between the tappings l8 and I1 being 10 micro-seconds. The delay between the generator and the tapping point l6 would be that required between the start of the quick rising portion of the saw-tooth and the end of one of the frame pulses.

In the arrangements described with reference to Figures 1 and 2 it has been assumed that the quick travelling portion of the input pulse represents a positive rise, but the arrangements are equally applicable to a pulse changing rapidly from positive to negative. If such a pulse is required with the arrangement of Figure 2, it will be necessary to interchange the standing biasing potential applied to the control grids of the valves l4 and II.

Referring again to Figure 1, if the short-circuiting link ill at the end of the delay-network is omitted, the network, thus being open circuited at the end remote from the generator, the arrangement may be used to eifect separation of addition of a synchronising pulse occurring simultaneously in the forward and reflected waves, the valve 1 will serve to give an output which represents the frame synchronising pulses, thus aoting as a limiting device. m general, with H such an arrangement no delay network would a be included between the generator and the connection to the control grid of the valve I.

Referring again to Figure 2, if the total delay of the network 4 is equal to half the frequency of the applied saw-tooth, the reflected: saw- .tooth exactly neutralises the voltage appearing across the input from the generator assuming 0 no loss occurs in the delay network so that the generator delivers purely current and no voltage.

In these circumstances it is not theoretically important to ensure that the surge impedance of the delay network and the internal impedance 15 of the generator are matched, but in'practice,

an approximate match is desirable in order to -allow for loss in the delay network and any error of matching of the exact delay and the voltage of the applied saw-tooth.

Figure 3 of the drawings shows a further application of the reflecting delay line to the ,pro- -duction of an observation pulse. The television waveform already mentioned includes after every line synchronising pulse a periodmf at least 5 micro-seconds at an amplitude representing black. Similarly, following the frame frequency pulse there is a longer black period,

so that there is always a minimum 5 microseconds following the end of any synchronising pulse. It may be required to observe the amplitude of the 5 micro-second, black period either for. the purpose of automatic volume'control or for example, as described in the specification of co-pending United States patent application Serial No. 69,831, new Patent No. 2,224,134, issued December 10, 1940, for the purpose oi reestablishing the D. C. or fixing the black level as described, for example, in the specification of co-pending- United States patent application Serial No. 40,532, now Patent No. 2,190,753, issued February 20, 1940. For any ofthese purposes a switching pulse is required, capable of operating observation or fixing devices during the 5 micro-seconds black period. Such a pulses of long duration from those of shorter switching n ab y may begin sligh ly f er duration. Thus, for example, assuming signals the beginningof t e 5 m c -se o s black including vision signals, line synchronising puls nod and end Just before the end of the 5 microof 10 micro-seconds duration and frame synseconds black Permdthe switchlng'pulse having chronising pulses of 40 micro-seconds duration dufation of say 4 micro'seconds- The circuit are applied to the input so that the synchronis- 0f Flgule shOWs a Suitable means Obtaining ing pulses are present in delay network in the this Pulsepositive direction, and assuming further that the The combined signal with synchronising pulses ,de1ay between the tapping point 5 and the in the positive sense and picture signals negamote end of the delay network is greater than 5 five, 15 to separating Valve w h is selfmicro-seconds, for example, 10 micro-seconds, biasing and Operates as described in the specifithen the largest positive pulses arriving at the cation coi'pending United States p nt apgrid of the valve 1 will be those due to the frame Pncatmn. r 720,205, w Patent synchrbmsing pulses which appear first at 2,252,746, issued August 19, The separate Y grid of the valve 1 as a forward travelling wave synchronising Signals ppear in the anode cirand are reflected from the open end of the de- 0. W11? across t 3 3 which matches he lay network, re-appearing at that grid. in addi- Surge impedance of he d ay network 4. This ti as a reflected wave, t giving a double syn. delay network is short circuited at th far end chronising amplitude at the grid due to the frame by the link "I- At the i -3 Va microecond synehronislng'pulgeg, Li synchronising pulses after the beginning of the delay network, a lead will appear at the grid of valve I due to the foris taken to t rid of a further valve 2|.

ward wave, but the contribution due to the fort nn n f he ynchronising pulse the ward wave will have ceased by thetime the conpotential at the anode of the valve l9 drops tribution due to the reflected wave returns to the n atively and a negativ wave is propagated generator from the open end of the network. 310118 the delay n w k nd reflected s D081- If the valve 1 is biased automatically or othere Wave, which, ivin b k a h n de. wise only to pass the pulserepresentative of th cancels the original negative voltage across the resistance 20. The valve 2| is so biased that it is unaffected by the negative pulse. At the end of the synchronising pulse however, when the anode current of the valve I9 is cut 01!, a positive wave travels down the delay network applying a positive voltage to the grid of valve 2|. The wave travels down the delay network and is reflected as a negative wave by the termination l0, travelling backwards along the delay network, cancelling the positive voltage on the grid of the valve 2|, and finally cancelling the positive voltage on the anode of the valve I9. If the delay from the anode of the valve |9 to the grid of the valve 2| is V; micro-second, the positive pulse of the grid of the valve 2| will start micro-second after the pulse on the anode of the valve 20. If the remainder of the delay is 2 micro-seconds, there will be a positive pulse of 4 micro-seconds duration on the grid of the valve 2| until the returning wave cancels the positive pulse. The valve-2l may be biased in the same manner as the valve l9, or in the alternative manner shown in the flgure.

and the cathode is connected through a high resistance 23 to a source of negative potential. A condenser 24 shunts the resistance 23 to ground. The'resistance is so proportioned that the current passed by the valve 2| during each eilective pulse, charges the condenser positively and sufllcient to maintain the cathode at such a potential as to pass a required current through the valve. As it is possible to obtain quite large signals on the grid of this valve, a further resistance 25 is inserted between the condenser and th cathode to reduce the slope of the valve, so that small irregularities on top of the wave do not produce large irregularities in the output signal of the valve 2|. Alternatively, two valves as described in the specification of co-pending' United States patent application Serial No. 269,397 may be employed to give a limiting action so that the amplitude of the output wave is unaffected by slight variations in amplitude of the wave arriving from the delay network.

Consideration of the circuit shown in Figure 3 will make it clear that the connections of the anode of the valve i9 and the control grid of the valve 2| may be interchanged. If such an interchange of connections is effected it will be seen that the delay network 3 is not fed from a source of signals having an impedance equal to its characteristic impedance but is in fact feeding into such an impedance.

Figure 4 shows a further application of the reflecting delay network to a television receiver. The basic principle is as described with reference to the modified form of Figure 1 shown in Figure 3. Television signals from, for example, an amplifler following the rectifier of a receiver are fed in at the terminal 28 with the picture signals in the positive sense and the synchronising signals negative. The D. C. is re-established by means of a diode valve 21 and leak resistance 28 as described in the specification of co-pending United valve 29. With these voltages. the currents through the valve would alter by 1 m. amp. for synchronising signals and 2% m. amps. for picture signals, apart from quick impulse changes due to the inevitable capacity to ground of the cathode of valve 29. Coupled to the cathode of this valve is the cathode of the line separating valve 32. The grid of this valve is maintained at a potential such that when its catrode is at say 60 volts, the valve will pass 2 111. amps. Between the cathodes of the valve 29 and the valve 32 are arranged a condenser 33 and resistance 34,-

' whose function is to bias the cathode of the valve 32 automatically so that it passes 2 m. amps. during synchronising signals and is cut oilior other amplitudes. In the example given, if the synchronising'signals occupy about. 10% of the The grid is connected through a leak resistance 22'to ground States patent application SerialNo. 720,205 previously referred to. The anode of the diode 21 is held at a suitable positive potential, which for ray tube are taken by the lead 3|. The potentiometer 30 may have a value, for example, of 5000 ohms and the incoming signals may be such that there are 5 volts of synchronising signal and 12% volts of picture signal on the cathode of the picture period, the average current to the cathode of the valve 32 will be 0.2 111. amp., so that the resistance should, with the 40 volts difference of cathode potential, be some 200,000 ohms, which may be shunted by a condenser of microfarad or more. synchronising signals appear on the anode of the valve 32, and a capacity connection, not shown, from the anode resistance 35 may pass these signals to the line synchronising generator.

Owing to the fact that during the synchronising signals the valve 32 absorbs some 2 m. amps, which would normally flow to the valve 29, the current change due to the synchronising signals -is increased from 1 m. amp. to about 3 m. amps,

ence to the modified form of Figure 1, to give an extra positive amplitude only for frame synchronising pulses which continue for long enough to allow the reflected wave to add to the undelayed wave. The signals so obtained are passed to the valve 31 whichmay be'self-biasing as described in the specification of co-pending United States patent application Serial No. 720,205.

An alternative biassing arrangement is shown in Figure 4, the grid leak 38 of the valve 31 being taken to the same source of potential as the grid of valve 29, so that when the valve 31 passes about 2 m. amps, its cathode will be positive in the order of volts. The cathode is fed by the high resistance 39 from earth, designed to pass the necessary mean current which for 8 frame synchronising pulses occurring every 50th of a second each effectively 20-micro-seconds long, is about 16 micro-amperes requiring a cathode resistance of'3.5 megohms. The cathode condenser 40 which stores this positive bias is shown connected to the anode decoupling condenser ll of the valve 29, so that any variations of H. T. voltage which are operative to change the grid potential, will also change the cathode potential. The decoupling condenser 4|, may be of 2 micro-farads and the cathode condenser 40 of the valve 31 may be for example -1 microfarad. The high cathode resistance provides in effect a D. C. reestablishment differing from the type described in the specification of co-pending United States patent application Serial No. 720,205 previously referred to, in that the cathode current itself is used to build up the necessary bias. Separate frame synchronising impulses may be taken from the anode of the valve 31.

' The delay networks shown may be of any known micro-seconds.

form having the necessary number of sections to give the required sharpness of pulse. The coils of adjacent sections may be coupled together for example to give an improved uniformity of delay characteristic. 7 M-derived sections adjacent to the terminations. As the delay is not constant for all frequencies; and is in error for frequencies approaching the cut-off, it may be found advisable to shunt the The delay networks may have stroke is half a line out of step relative to the I T line scanning as compared with the other frame return stroke and the: effects of interaction between the line and frame circuits are not the same for two frame scans. The interaction is usually due to stray couplingswhichare aifected by the relatively large voltages and ,currents occurringin the line scanning circuit during the rapid return stroke-and as these currents are varying rapidly, inductive stray couplings are easily affected by them. The back coupled voltages operate either to trip the frame scanning circuit slightly earlier in one frame scan than the other, or they may delay the tripping of the frame scanning circuit. Such an effect corre frame pulse'not coincident with the line there will be a delay of 30 micro-seconds before the beginning of the next line pulse. It isthereforenecess'ary to provide a blocking oscillator orother relaxation device which will complete .its quick stroke in less than 30micro-seconds so; that the charging of the saw-tooth condenser or other reactanceis completed beforethe beginning of the next line return. This can-be effected by-the ordinary blocking oscillator valve by using an eflicientvalve of high slope and a blocking oscillator transformer of, for example,

twice the number of turnsnormally employed for a line blocking oscillator. By using a valve} with high slope sufficient charge can be accumulated in a sufi'iciently large condenser to allow this blocking, oscillator to work .at' frame fre-' quen'cy with an active period considerably shorter than. 3.0 micro-seconds. Broadly speaking, the

circuit following this condenser. is operating linearly so that it does not rectify small induced voltages from the linescanning circuit and the arrangement should permit perfect interlacing Y to be obtained despite'small cross couplings.

Modifications in detail may, of course, be effected in carrying out the invention and, for example, while reference has been made to limiting devices constituted by thermionic valves having a control grid or electrode, it will be understood that other forms-of limiting device may be employed, such for example as a diode valve.

Again, while inthe description of Figure 3 reference has been made to the use of a pair of sponds to a slight delay or advance of the eifective frame synchronising pulse in alternate frame ing valve of. the saw-tooth generator. If during the period of such a discharge a line scan voltage is induced in the discharging circuit, this voltage may alter the potential to which the condenser is discharged, thereby spoiling the interlace. In severe cases the displacement may amount to several line widths although the frame timing is perfect.

Assuming it can be arranged that the whole process of tripping the frame scanning circuit and developing the quick portion of the frame deflecting saw-tooth occurs for both the frames during a portion of the forward stroke of the' line .scan, the interlacing troubles mentioned would not be so serious because a first order inductive coupling is only affected by the, relatively slow changes during the forward line stroke and the rate of change is approximately constant during the whole of the forward stroke.

The method of using the arrangementof Figure 1 for separating pulses described previously may be adopted in. the presentinstance. Instead of the deflecting waveform generating valve being tripped on the occurrence of a frame pulse the effect ofthe frame pulse on the frame scanning circuit is delayed by, for example, 20 Thus, in the case of the frame pulse coincident with a line pulse, the return stroke of the line will have ceasedv during this 20 micro-seconds. Similarly in the case of the both input and outputterminals a thermionicvalves having the cathodesconnected to a com- "mon impedance, it will be understood that a double triode' valve having a single cathode may be employed.

' I claim:

1. An electrical impulse converting system comprising an electrical delay network having a predetermined characteristic impedance and electrical impulse source connected to said input terminalsto transmit electrical impulses to said network, said network being terminated at said input terminal by an impedance substantially the same magnitude as said characteristic impedance and being mismatchedas to said characteristic impedance at said output terminals to provide reflected impulsesfromsaid transmitted impulses, a, thermionic device, adjustable means to connect said thermionic device to said network to receive both'the transmitted and the reflected impulses to vary the time interval between the receipt of the transmitted impulses and the re-- ceipt of the reflected impulses at said thermionic device and to' vary the time interval between the transmission of impulses from said source 1 to said network and thereceipt of said'transmitted'impulses at said thermionic device, and means to derive output im'pulse energy from said 7 thermionic device, said output impulse energy characteristic being controlled by the time dif-' ference between said transmitted and said refiected impulses. g 2. An electrical impulse converting system comprising an electrical delay network having a predetermined characteristic impedance and both input-and output terminals, a thermionic electrical impulse source "connectedto said input terminals to transmit electrical impulses to said v network, said network being terminated atsaid input terminals'by'. animpedance substantially, the same-magnitude as said characteristic pedance and being short-circuited at'said output terminals to provide reflected impulses, of opposite polarity from that of said transmitted impulses, a thermionic device, adjustable means to connect said thermionic device to said network to receive both the transmitted and the reflected impulses to vary the time interval between the receipt of the transmitted impulses and the receipt of the reflected impulses at said thermionic device and to vary the time interval between the transmission of impulses from said source to said network and the receipt of said transmitted impulses at said thermionic device, and meansto derive output impulse energy from said thermionic device, said output impulse energy characteristic being controlled by the time diflerence between said transmitted and said reflected impulses.

3. An electrical impulse converting system comprising an electrical delay network having a predetermined characteristic impedance and both input and output terminals, a thermionic electrical impulse source connected to said input terminals to transmit electrical impulses to said network, said network being terminated at said input terminals by an impedance substantially the same magnitude as said characteristic impedance and being open-circuited at said output terminals to provide reflected impulses of the same polarity as that or said transmitted impulses, a thermionic device, adjustable means to connect said thermionic device to said network to receive both the transmitted and the reflected impulses to vary the time interval between the receipt of the transmitted impulses and the receipt of the reflected impulses at said thermionic device and to vary the time interval between the transmission of impulses from said source to said network and the receipt of said transmitted impulses at said thermionic device, and means to derive output impulse energy from said thermionic device, said output impulse energy characteristic being controlled by the time difference between said transmitted and said. reflected impulses. I

4. An electrical impulse converting system comprising an electrical delay network having a predetermined characteristic impedance and both input and output terminals, a thermionic electrical impulse source connected to said input terminals to transmit electrical impulses to said network, said network being terminated at said input terminals by an impedance substantially the same magnitude assaid characteristic impedance and being mismatched as to said characteristic impedance at said output terminals to provide reflected impulses from said transmitted impulses, two electron discharge tubes each having a cathode, control electrode and an anode, adjustable means to connect each control electrode of said electron discharge tubes to said network to receive both the transmitted and the reflected impulses to vary the time interval between the receipt of the transmitted impulses and the receipt oi the reflected impulses at said control electrodes and to vary the time interval between the transmission of impulses from said source to said network and the receipt of said transmitted impulses at said control electrodes, and means to derive output impulse energy from said anodes of said electron discharge device,

said output impulse energy characteristic being controlled by the time diflerence between said transmitted and said reflected impulses.

5. An electrical impulse converting system comprising an electrical delay network having a predetermined characteristic impedance and both input and output terminals, a thermionic electrical impulse source connected to said input terminals .to transmit electrical impulses to said network, said network being terminated at said input terminals by an impedance substantially the same magnitude as said characteristic impedance and being mismatched as to said characteristic impedance at said output terminals to provide reflected impulses from said transmitted impulses, a thermionic device, adjustable means to connect said thermionic device to said network to receive both the transmitted and the reflected impulses to vary the time interval between the receipt of the transmitted impulses and the receipt of the reflected impulses at said thermionic device and to vary the time interval between the transmission of impulses from said source to said network and the receipt of said transmitted impulses at said thermionic device, means to derive output impulse energy from said thermionic device, said outputimpulse energy characteristic being controlled by the time diflerence between ,said transmitted and said reflected impulses, and

biasing means connected to said thermionic device to provide output impulse energy only when said transmitted and reflected impulses are superimposed with the same polarity.

ALAN DOWER BLUMLEIN.

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