US2474490A - Start-stop regenerative repeater - Google Patents

Description

2 Sheets-Sheet June 28, 1949. P, PELLE START-STOP PEGENEATIVE REPEATER Filed May 9, 1945 w ,w a Z WN a r1v n m5 \l \|l \I E. W 2f .W m 1w e f1 UO .n a f n n n f w r `f w P e r 0| llw 1111 a. i r u 4 --121 N 0/ I s T IR 5 m s t w/.R m s .I .1.11m ni z 5 iii-- l n y 4 d W E M v v 4 m w. /w 4 U. w f/ 1.. J D .ma s l.l l -l il-, I f W ..H 11111:?? .C M 0l v t /.E 2 12.1..- .nunwnnlnh v m. M n d r .M x 1 yk. ,0 i m 1m, .f i .J l r n w -uuh.; l l 0 1 i i l 0/ L. mr y o. H r

W1 rf HE M0 K k@ W M 5 M6 M HLM wmf .mm M Wmm Mmm Um w 5 m 4 mw l( l W ,W 0, M w. D,

June 28, 1949. P. PELLE 2,474,490

START-STOP REGENERATIVE REPEATER Fliled May 9, 1945 2 Sheets-Sheet 2 Patented June 28, 1949 :STATE-s. "PATENT orifice Application May 19 1945, Seriall No. 592,770 In France February 10, y1944 Section 1, Public Law 690; August 8, 1946 Patent expires February 10, 1964 10 Claims. 1

The presentmvention relates to telegraph repeaters. and regeneratingAv and. distohtiQn eliminatingdevices for telegraph modulated signals sent `out in the arhythmigc-or start-stop code.

One ofthe obieetsofgthe presentinvention is to provide .a deviceL of the general .character above referred ilo-comprising. mansior sending current impulses, said means beinggcontrolled by anl oscillater. thereby insuring greater stabil-ity than has heretofore been. possible.

.Another` object of the present invention is to provide a device Vof the generaloharacter above described with novel inea-ns for insuring the marking or determination ci the. operating times withA precision.

These and such other aims and objects kof the present. invention as may hereinafter appear will.y

be readily understoodf-romtlie following vdescrip-A tion, takenfin #connectionA with the accompanying drawing, of one illustrative embodiment of the present invention.

It is known that when using disturbed tele-` graph lines or telegraph linesy .of great length,l

the telegraph keying modulation oi the signal characterswwhichreaches .the receiving end ofthe line often suffers. considerable distortion, partien ularly when the line. is made of several sections, the transmittingrelay for eachV section 'being connected tothe receiving relay terminating a preceding section. I t is,l therefore, necessary to provide devies tov correct such Vdistortions and reshape the distorted pulses constituting the elements of the signal. Various Iexpedients have beenr usedr for this purpose.

.It is here proposed to use foreach group of the signal keying modulation received, a group of. short current impulses or signal elements precisely separated .from cach other by a unitary interval or time element of' said modulations. This` group of short currentimpulses'representing a charac-ter may consist, for example, of seven such short impulses, if the code used is a-ve element code plus a starting and stop signal.

Suitable means are provided in the regenerating system of thefpre-sent invention whereby the rst oi said current 'impuses occurs one-half of a unitary interval after the arrival of the starting signal element. As :a result, the impulses that follow occur at mennen-.ts corresponding exactly to the mid-'point of the. theoretical intervals relative to each element of the code used. A device is provided-which receives. the signal modulation tov be 11e-.shapedand.retransmittedy .and gives passage to 4short current impulses directed in the .same sense or dirccticnso that -iicw through 2 a winding of a polarizedrelay inone or the other direction. .according tothe polarity ci the modulation signalaelemenie received. at. the moment that said impulses arrivai The short current.irnpulses thus determine the instants when the armatures of the polarized relay. are displaced er rocked, the'direction in which said arnoatures.

are rocked being` determined by polarity of the signal element, neceivsed.h This polarized relaythus restores, the signal keying modulation which is received. tree of. distcrtimiy and with a displacement-.of 'nimeer phase equal to one-.half oi the unitary.intemfal-v In the drawing:

Fig. 1 is. a bloei: diagram of the signal reeenerator system.;

Fie. 2 is adieercmshcwingthe; operating sequencek of the Severalsignal. elements as they occur in the regenerator;

Fig. 3 is a circuitoi; asystem incorporating the improved signalfregenerator for a telegraph line.

Generally speaking, the presen-t improved reer generator includes oscillator Whose frequency Y isaccurately adjustedso that` the length or period transmitted. oscillator is normally blocked.

but is instantaneously unblocked with a prede,-vr termined. initial phase upon thearrival of each starting` element of the received signal group. and aiterwar.dsl yblocked again,` responsive to the operation of an impulse-counter at the theoretical instant which corresponds tothe mid-point of the na-l steering signal element. cf thesignal group.. assuming said stopping element to have a duration equal t0.` that, of the code elements of the Chaelatl' lseli.V

Qscula-tions.l thus generated cause a train (for eacnsierial group) of @sequence of short current impulses (Say seven. in. number) which, appeal?. at. a .particular peint, ci cach-cycley of the oscillatien-` andere consequently accurately spaced from one. another by a interval.. The rst of, such oscillations has-its, positive. peak, due to a device adapted tc adjust. the oscillation phase, half a unitary interval after the arrival cf the starting signal element.; IIt follows that thesubsequentimpulses appear .at instants which exactly correspond with the Iiidvpoint of theoretical intervals ci cach codesisnal. elerrient.4

A current reversing device is provided for receiving the incoming keying medir.lated signal t0 be regenerated or recharged and yfor allowing passage of short current impulses which all have the same direction, in such manner that thelr flow through the winding of a relay in either direction, depending upon the polari-ty of the received signal modulation element as they arrive.

The short current impulses consequently determine the displacement yor rocking times or instants of the armature of the relay, the direction of the rocking action being dependent upon the received polarity of the signal element. Such polarizd relay restores or re-shapes Without any distortion the elements of the rceived signal train and with a time lag equal to half a unitary interval of the signal element. As a result of this, it corrects both the irregular distortion and the rate of keying modulation. The maximum distortion of the received modulation signal that can be possibly regenerated or reshaped, is limited only by the duration of the short current impulses or elements. The latter should be long enough to actua-te the polarized relay.

In the system of Fig. 1, the modulation of the keyed signal received on the incoming line L1 operates an input relay RE, the duty of which is to block or unblock an oscillator O. Oscillations delivered by this oscillator ow to a phase shifter D and control a short current pulse shaper or emitter I. Such pulses or impulses, as well as the modulation of the keyed signal received by the incoming line L1, are applied to current reversing means which may illustratively comprise a set of rectifying cells RS associated with a polarized output relay R. The regenerated modulation constituting the keyed signal is delivered at the output from reverser RS on the outgoing line L2. An impulse counter CI counts the impulses delivered by the emitter I and, as the seventh impulse occurs, releases the input relay RE, thereby blocking the oscillator O, and resumes its unoperated position.

In Fig. 2 are representedthe operating instants or times of the several elements of the system.

' At (a) in Fig. 2, is shown the perfect signal elements of a typical seven element train or group, representing a letter, as emitted by a transmitter at the of an incoming line L1.

At (y) and (h) in Fig. 2, are shown extreme possible types of distorted signals arriving at the repeating regenerating station and applied to input relay RE and also direct to the winding of polarized output relay R, which distorted signals can be reconstituted into the originally transmitted perfect signal of Fig. 2(a) by the regenerator here described, as can likewise received signals whose elements are less seriously distorted.

Fig. 2 shows at (b) the movements of the armature of input relay RE. which closes, after a brief operating interval, after the arrival of negative initial starting impulse d, and remains closed until there have been counted, as by condenser storage, six following impulses, the last being the stop impulse (a) ofl positive polarity which deenergizes input relay RE. During the time that input relay RE is thus closed, as shown at Fig. 2(1)). it unblocks oscillator O of the keying element frequency, which over the same period of time delivers oscillations as shown at (c) in Fig. 2. The phase of these oscillations is shifted so that. as shown at (d) in Fig. 2, the peaks are the mid-point of the interval of each of the signal elements.

Short pulses, as shown at (e) in Fig. 2, are formed by a pulser on the positive peaks of the of the modulation signal keying element.

phase-shifted oscillations shown at (d) in Fig. 2, and are applied to time a pole-changing output relay in accordance with the polarity of incoming signal elements, producing outgoing signal elements, as shown at (j) in Fig. 2, which are the same as the perfect signal elements shown at (a) in Fig. 2, but shifted by one-half of the length of the signal element.

In Fig. 2, is shown at (a) by way of example, any perfect modulation signal as received on the incoming line L1 and corresponding to a character. T is the duration of the unitary time interval of the signal code, the changes in the current direction occurring at the instants designated by T, 2T, 3T, 4T, 5T. The initial and final signal elements d and a are, respectively, the starting and stopping elements for the particular signal group, while the signal elements I, 2, 3, 4, 5, are the code elements representing a letter or gure. Fig. 2 also shows the movements of the armature of the input relay RE. `This relay being in unoperated condition at the instant taken as zero time, its armature will be rocked on arrival of start element d, so that the osciliator O is unblocked a very short time O1 (Fig. 2-d) following the arrival of the starting initial signal element d. Oscillations as applied by the oscillator O are represented at (c) in Fig. 2. After passing through the phase shifter D, they appear as shown in Fig. 2 at (d), each minimum corresponding to the instants T, 2T, 3T, and so forth, while each maximum corresponds to the midpoint of a modulation or keying element.

The pulse sender I delivers a short current pulse at each peak or maximum of the oscillations in the output of the phase shifter as shown at (e) in Fig. 2. The positions assumed by the armature is of the double current polarized output relay R are illustrated at (f) in Fig. 2. Normally this armature is pulled from its left contact r3 to its right contact t3 when the rst short current pulse reaches relay R, the direction in which said pulse flows through the exciting Winding of the relay having been predetermined by the polarity (Fig. 2--a.) As the second short impulse of the group of seven constituting the letter, reaches output relay R, it oWs through the winding of polarized relay Rin the reverse direction, since the polarity of the modulation keying signal element I is the opposite to that of initial starting signal element (d) and rocks the armature of relay R into contact with its left contact r3. The same phenomena occur for the other impulses of the group of seven shown in Fig. 2-a, constituting the letter. The fifth impulse for the character shown in Fig. 2-a has no effect on the output relay R because of its tendency to rock its armature into Contact with the left contact 1'3 against which it has been previously brought by the preceding impulse.

The seventh impulse counted by the impulse counter C'I returns the input relay RE to rest position and blocks the oscillator O. The input relay RE operates very fast in returning to its rest condition.

As will be seen, keying signal elements of a received signal, although considerably distorted as those shown at (y) and (h) in Fig. 2, will still be correctly regenerated or reshaped since the polarity of the elements of the output during intervals of the pulse with O2 duration (Fig. 2 6) which correspond'to the several pulses, are similar to those of the corresponding elements of the 5 perfect. modulation of ther transmitted signal, as. shown` aty (a) in Fig. 2.

Fig. 3. shows an illustrative possible, applicationy of a Vdevice embodying the present invention. As shown in thisembodiment, the double winding inf-z put relay RE has two diierential windings I, 2, of which 2 is the weaker, the winding I being connected on the one hand to the incoming line L1 and on the other hand to a current source +B..

The winding 2 of input relay RE is in the cir*- cuit of the pulse counter CI, and input relay REy is provided with a pair of armatures i1 and i2 in operative relation with the windings I", 2, of irrputv relay RE, said armatures vibrating through the gaps between contacts rl, tI, and r2, t2, respectively.

In unoperated position, the armature ii rests on. contact r1 while the armature i2 rests on contact 12. Should a signal element of positive polarity` be received on the incoming line L1, no current will flow through the winding I of input relay RE, this polarity being nullii'led by the positive current source -I-B. The oscillator O of the capacityresistance type is then blocked, the condensers C1, C2, C3, of its grid circuit being charged.y through contact r1 with a predetermined positive voltage by a potentiometer P1, so that their charge shall equal that corresponding to the peak of the oscillating plate voltage of the oscillatorI tube O when oscillating normally.

When relay armature i1 is in rest position en,- gaging contact r1, there is no coupling between,l the plate circuit and the grid circuit of the oscil-A lator tube O, so that this tube cannot oscillate and is blocked. When armature i1 is in operated position engaging Contact t1, there is coupling between the plate circuit and the grid circuit of the oscillator tube, through condensersl CI, C2, C3, and the tube is unblocked. and oscillates.

The impulse counter CI is constituted by a circuit including a capacitance 3. and a cathode re.l sistance l associated with a gas discharge tube. When the armature i2 of the input relay RE is onrest contact r2, the grid I5 of the discharge tubeV has cathode potential, whereby this discharge tube becomes conductive and closes a circuit across the capacitance 3 between the positive ter'- minal of battery HT, and the grounded negative terminal of battery HT. The current through this circuit flows through the differential Winding 2 of the input relay RE and holds its armatures in contact with the contacts r1 and rz, under which circumstances they are unoperated position. Thus, when the first charging impulse is applied to condenser 3, oscillator I remains.` blocked.

Upon the arrival of the starting element d of a signal train, a negative polarity exists on the line L1, current ilows from +B, and the principal winding I of the input relay RE is energized. The action of this Winding I, is stronger than that of the diierential winding 2 of input rel-ay RE,v whereby the input relay RE rocks its armatures ii and i2 into contact with actuated contacts t1 and t2, respectively. Owing to the Contact madec at t1 the oscillator O is unblocked and the oscillan tion starts instantaneously owing to the charge which was delivered through Contact t1 to the capacitances C1, C2, C3, of the grid circuit during the unoperated period, which charge corresponds to the voltage which is the peak plate Voltage of oscillator tube O during norm-a1 operation. The-f initial phase of the oscillation corresponds to the.y

6r" ofthe discharge tube of the impulse. counter ci? is connected atA operated.' contact ti to apoten-tial. determi-ned by a. potentiometer P2, whereby it is negatively polarized 'withy respect to the cathode .of saidv tube as determined by the cathode resista ance 4. The gastube of thefimpulse counter then ceases tobe conductive, and the capacitance 3Lis:

sldwly charged ironia; current. source l+HI.

lEhe oscillation delivered; from` oscillator O flows :through the phase shifter Dr constitutedy byv the capacitancef-andthe resistanceslsand 'I-; itl trips; thepulse sender l': constitutedby a triode-pentode.

conl'iccteclv asisvknown. in the art to'fform a blocki ingy relaaiation` oscillator by' a double' coupling be-A tweenv the pent-ode grid and the triode plate ort the onehancl., andvv to. a. cathode resistance 8 ons the otherhand.v Pulses collected in the pentodeplate,V circuit passv through transformers 9, t3: Each impulse as it passes through the transformer Ill'. transientlyrenders the grid of the gas'. discharge tube of impulse counter CI more pos'ie tive, thereby approximating the value'. of its potential; to. that ofrthcfcathode. The time constant of the circuitv including the; capacitance 3., and: resistance 4 is.. so calculated that the scvenl'fllz` impulse renders the gasy tube of CI; condlmting-iv At this moment,` the dischargecurren-t froml the:l ca'pac-:itmncev 3 passes. through the win-ding 2'. op the input relay RE. and returns the armature of,

RE tounoperatedposition, closing;l contactsri andv r2, thereby blocking; oscillator O.

As they flow through the transformer 9`r ther short current impulses reach thesetv of rectiyingl cel-ls Il, I2, I3, I4, constitutingl current reverser RS associated with the polarized. output rela-y Re the armature* is of which comprises a permanent magneti and is connected to the-outgoing line Lz. and can beI rocked into Contact with either one o; the relay contacts trend r3, which are respec-y tively connected` to the telegraph line batteries,- -I-B and -B. When current iloWs through. the; twov windings in series'. of relayR in one direction, the armatureis.V rocked into engagement with relay contact 1jr-if; it` is not already inengagement. therewith. Whenl current flows through the two# windings in series of relay R in the oppositev di-` rection, the armature isis rockedintoen'gagement with` right contact .tai-f' it is not already in engage men-t therewith.;l The armature is is usually'in engagement with4 eitherv ra or ta, depending on the directionv o the last pulse of current through the;-` Windings of relay The setof rectifying cells, RSfis. of known construction; and arrangement.. andN comprises the four recti-fying cells, I I, I-2f,` I3g,-,

55, t4. When. a positive polarity,A is applied to the incomingA line. L1, cl-irrentsL iiow through the;k transverse rectiiier cells I 2 and I3\ and render themconductive.` These currents. have no actionf whatever on the` output relay R, the current;

mi tl-irougghv one ofthel two windings I and 2 of the;v

latter tloWi-ng the opposite direction to thatpf the currentiiowing through the other.- If, dure.` ing the moment when cells I2 and I3 are thus; rendered conductive\,V a pulse fromemitter I flows through thetransformer 9, it nds-aconductiyepat-h throughthe-f conductive-y rectifying cells I2*L and L3 and the two windings I=, 2,- of the output. relay Rif which are connected in series,l whereupon, this relay rocksY its'. armaturen i'ntocontact with A 'mi theleit contact mi anda positive polarity is imzpeak ofv thel plate voltage. (Fie. 2.-:2.)v The grid. tc moment; ar'nulse.; from @mit.ter-k I. passes through.

the transformer 9, it will ow through the rectifier cells I I, I4, and through the output relay R, but in the reverse direction. The output relay R then rocks its armature i3 into contact with right contact t3 and a negative polarity is imparted to the outgoing line L2. As will be seen, distorted impulses arriving through the incoming line L1 cannot alone control the output relay R, the latter responding only to correct impulses furnished by the unit O, I, 9, which is determined by the oscillator. Signals sent through the outgoing line Lz are consequently of correct shape.

I am aware that the present invention may be embodied in other specic forms without departing from the spirit or essential attributes thereof,l and I, therefore, desire that the present embodiment of the invention be considered in all respects as illustrative and not restrictive, reference being 'had to the appended claims rather than to the foregoing description to indicate the scope of the invention.

What is claimed is:

1. A regenerating and distortion-eliminating device for telegraphic modulated signals emitted in the start-stop code, comprising on a telegraphic line an oscillator having a period equal to the theoretical duration of the unitary interval of the modulations requiring regeneration, an input relay located before said oscillator for blocking and unblocking the oscillatorLe, phase shifter fed by the oscillator, a shortcurrent vimpulse emitter tripped by said phase shifter, a current reversing device and polarized relay unit fed by said emitter andforming the output terminal of the regenerating and distortion eliminating device, and means shunted across the input relay and emitter for counting the impulses generated by said emitter and lfor actuating the input relay to block the oscillator while itself resuming its inoperative condition at the appearance of the seventh impulse of a Sequence. l

2. A regenerating and distortion-eliminating device for telegraphic modulated signals emittedv in the start-stop code, comprising on a telegraphic line an oscillator having a period equal to the theoretical duration of the unitary interval of the modulations requiring regeneration, an input relay connected in the input of said oscillator for blocking and unblocking the oscillator, a phase shifter fed by the oscillator, a short' current impulse emitter tripped bysaid phase shifter so as to center each impulse on the theoretical mid-points` of the several codeelements, a current reversing device and polarized relay unit fed by said emitter and forming the output terminal of the regenerating and distortion eliminating device, and means shunted -across the input relay and emitter for counting the impulses generated by said emitter and for operating the input relay to block the oscillator while itself resuming its inoperative'condition at the appearance of the seventh impulse of a sequence.

-l 3. A regenerating and distortion-eliminating device for telegraphic modulated signals emitted in the start-stop code, comprising on a Atelegraphic line an oscillator having a period equal t'o the theoretical duration of the unitary interval of the modulations requiring regeneration, an input relay located before said oscillator for blocking and unblocking the oscillator, a phase shifter fed by the oscillator, a short current impulse emitter tripped by said phase shifter, a current reversing device and polarized relay unit fed by said emitter and forming the output kterminal of the regenerating and distance eliminating device, r

said reversing device comprising a rectifier bridge and determining the direction of flow of said impulses through said relay responsive to the polarif?. ties of each code element as received when the impulse appears, and means shunted across the input relay and emitter for counting the impulses generated by said emitter and for operating the input relay to block the oscillator while itself re- 10 'suming its inoperative condition at the appearance of the seventh impulse of a sequence.

4. A regenerating and distortion-eliminating device for telegraphic modualted signals emitted in the start-stop code, comprising on a telef graphic line having an input terminal and an output terminal, an oscillator having a period equal to the theoretical duration of the unitary interval of the modulations requiring regeneration, an input polarized relay connected in the input of said oscillator for blocking and unblocking the oscillator, said relay including a pair of differential windings and armatures, one of the windings interconnecting the line input terminal and a current source, a phase shifter fed by the oscillator,

a short current impulse emitter tripped by said phase shifter, a current reversing device and polarized relay unit fed by said emitter and forming the output terminal of the regenerating and distortion eliminating device, and an impulse counter including the other input relay winding for counting the impulses generated by said emitter and for actuating the input relay to block the oscillator while itself resuming its inoperative condition at the appearance of the seventh impulse of a sequence.

5. A regenerating and distortion-eliminating device for telegraphic modulated signals emitted in the start-stop code, comprising on a telegraphic line an oscillator of the capacitance- 4U@ resistance type having a period equal to the theoretical duration of the unitary interval of the modulations requiring to be regeneratedan input relay connected in the input of said oscillator for blocking and releasing the oscillator, a

phase shifter fed by the oscillator, a short current impulse emitter tripped by said phase shifter, a current reversing device and polarized relay unit fed by said emitter and forming the output terminal of the regenerating and distortion eliminating device, and an impulse counter 'bridging the input relay and emitter and comprising a condenser connected for storing pulses emitted by said pulse emitter for counting the impulses generated by said emitter and being connected for actuating the input relay said inin the start-stop code, comprising on a telegraphic line, an oscillator of the capacitanceresistance and tube type including grid circuit condensers positively charged by potentiometer means, said oscillator having a period equal to the theoretical duration of the unitary interval of the modulations requiring regeneration, an input relay connected in the input of said oscillator for blocking and unblocking the oscillator, a phase shifter fed by the oscillator, a short current impulse emitter tripped by said phase shifter,

a current reversing device and polarized relay unit fed by said emitter and forming the output terminal of the regenerating and distortion eliminating device, and an impulse counter bridging the input relay and emitter and comprising a condenser connected for storing pulses emitted by said impulse emitter for counting the impulses generated by said emitter and being connected for actuating the input relay, said input relay being connected when actuated to block the oscillator.

7. A regenerating and distortion-eliminating device for telegraphic modulated signals emitted in the start-stop code, comprising on a telegraphic line an oscillator having a period equal to the theoretical duration of the unitary interval of the modulations requiring regeneration, an input relay located before said oscillator for blocking and unblocking the oscillator, a phase shifter fed by the oscillator, a short current impulse emitter tripped by said phase shifter, a current reversing device and polarized relay unit fed by said emitter and forming the output terminal of the regenerating and torsion eliminating device, and an impulse counter bridging the input relay and emitter and comprising a condenser connected for storing pulses emitted by said impulse emitter for counting the impulses generated by said emitter and being connectedA for urging the input relay, said input relay being connected when actuated to block the oscillator, said counter including a capacitance and resistance unit associated with a discharge tube.

8. In a telegraph repeater regenerating system transmitting signal trains of signal elements of both polarities of uniform duration determined by a definite keying frequency including initial starting and nal stop elements, an input relay having a principal winding and an opposing bias winding, an output polarized relay having two windings connected in series and having two controlled contacts, connected respectively for applying voltages of opposite polarity to its armature, a line input terminal connected to the common terminal of said windings of said output relay and also connected to said principal winding of said input relay, a blocking oscillator tube of said keying frequency and having its blocking circuit connected to a controlled contact of said input relay for becoming unblocked y upon receipt of a start pulse by said input relay, a phase shifter connected to the output of said oscillator tube, a narrow pulse former connected to the output of said phase shifter and adapted to form a narrow pulse on the positive peaks of the output of said phase shifter, a rectifier bridge having two terminals connected to the output of said pulse :former and having its other two terminals connected to the outer terminals of the `windings of said output relay, said rectifier bridge having only one of its pairs of arms conductive at a given time as determined by the polarity of the signal element applied at a given instant to said line input terminal, whereby the direction of application of pulses from said pulse former to the two windings in series of said output relay is determined by the polarity of the instantaneous signal element applied to the input terminal, and regenerated undistorted signals are delivered to the armature of said output relay.

9. A system according to claim 8, and an irnpulse counter unit comprising a gas triode and a condenser, said condenser being connected in the output circuit of said gas triode through said biaswinding of said input relay, controlled contacts of said input relay connected for connecting the grid of said gas triode to its cathode when said oscillator is blocked and for connecting Said grid of said gas triode to the output of said pulse former when said oscillator is unblocked, said output circuit of said gas triode including said condenser being adapted upon the receipt from said impulse former of the number of signal elements constituting a complete Signal train including the final stop element, to cause said condenser to discharge and ionize said gas tube and actuate said input relay to stop said oscillator.

10. A system according to claim 8, the blocking circuit of said blocking oscillator comprising reactive elements adapted to initially apply to the plate of said blocking oscillator tube at the instant of unblocking a positive Voltage which is the peak voltage of said lblocking oscillator tube during normal operation, whereby upon unblocking the said oscillator tube starts its initial oscillation at its normal positive peak,

PELLE, PIERRE.

REFERENCES CITED The following referenlces are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,133,456 Kinkead Oct. 18, 1938 2,357,840 Martin Sept. 12, 1944

Images