US2438492A - Signaling system - Google Patents

Description

lMarch 30, 1948.

y H. M. BASCOM ETAL SIGNALING SYSTEM v Fiied Aug. l17, 1944 2 sheexssheet .1

mobs .Sho

B. OSTENDORF JR.

au. @Ascou /NVEA/rons R. EmssoN/VEAU 17H54 av March 30, 1948. H. M. BAscoM ETAL SIGNALING SYSTEM Filed Aug. 1'7, 1944 2 sheets-sheet 2 u r 2' Ess Q Sl - R' 'NVENTORS s'. srENoonF, Jn.

. .y ZREA ATTORNEY Patented Mar. 30, 1948 2.438.492 sionismo srs'rmu Henry M. Bascom, New York, Robert F. Massonnean, Scandale, Bernard Ostendorf, Jr., Jamaica, and Wilton T. Rea, Manhasset, N. Y., assignors to Bell Telephone Laboratories, lincorporated, New York, N. Y., a corporation of .1

New York Application August I7, met, Serial No. Miiz Claims. (Cl. itt-380) This invention relates to signaling systems and start-stop" oscillator therein and received in a circuit which responds to both positive and negative half cycles, inverts the negative half cycles and causes both the positive half cycles and the inverted negative half cycles to be recorded by the tubes oi a counting chain, said tubes conditioning, in succession, the tubes oi a second chain for operating the tube therein last conn ditioned subsequent to the reception ci the last half cycleof the signal train.

Broadly speaking, the present invention repre sents, in a number` of respects, an improvement of the signaling system disclosed and claimed in the copending application of R. F. Massonneau, Serial No. 453,843, led August 6, 1942, now U. S. Letters Patent 2,373,134, granted April 10, 1945.

The various features of the invention will be understood from the following description when considered in connection with the accompanying two. sheets of drawings, the scope of the invention being more particularly pointed out in the appended claims.

In the accompanying drawings, Fig. 1` shows the transmitter and Fig. 2 shows the receiver, said figures being placed adjacent to each other from left to right in the order named to disclose the invention completely.

The transmitter, shown in Fig. 1, comprises a start-stop oscillator of the type disclosed in A Patent No. 2,370,685, issued to W. T. Rea. and J.

R. Wilkerson on March 6, 1945; a counting chain consisting of tencold cathode gas-filled tubes CTICTD, a recycling circuit comprising two cold cathode gas-rilled tubes GI and G2 by means of which single or repetitive transmission o f a pulse train is accomplished, a line coupling circuit comprising a potentiometer network RZB-R29 anda line amplifying tube L by means of which the oscillator is coupled to the line, the double triode D by means of which it is insured that only the predetermined number of oscillations are caused to be applied to the line, an impulse control circuit including the transformer IT and the upper triode of tube A by means of which each half cycle applied, to the line is caused to be registered on one of the tubes of the counting chain CTI-CTO, and a restoring circuit including the upper triode of tube B and the vacuum tube C 2 recycling circuit, extinguishes the tube of the counting chain.

Thelreceiver, shown in Fig. 2, comprises a two stage direct current ampliier employing a double triade tube RL; a detector, inverter and impulse amplier operating on odd half cycles, all of lwhich comprise three of the trodes of the double triode tubes DETl, DET2 and INV; a. detector and impulse amplifier operating on even half cycles which comprises two triodes of the trlode tubes DETZZ and INV; a recycling circuit comprising the twoy triodes of vacuum tube'RE and the vacuum tubes EXT and SEL; a counting chain circuit consisting of ten cold cathode gas-filled tubes C'I'Rl-C'I'Rt; and a marking chain consisting ofv the ten coldcathode gas-filled tubes Si-Sit Referring now more particularly to Fig. 1, the general operation of the transmitter is as follows:

During the interval when no signal is being transmitted the oscillator OC is held in a non oscillating condition and the line coupling circuit is so conditioned as' to prevent any impulses from being applied to the line. At this time, all the tubes GTi-CTD of the counting chain are maintained in the non-conducting condition. Now when a signal consisting of a certain number of positive andnegative half-cycles of a continu` ous alternating current train is to be transmitted over line LN, a connection is made between a common conductor and a tube in thel counting chain CTI-CTU that marks the last half cycle of the' desired signal train. At this time the recycling tube G2 becomes energized to condition the tubes of the counting chain for operation, starts the oscillator OC and removes the block in the line coupling circuit. The sine wave produced by the oscillator OC -is thus permitted to be impressed on theline LN. Each time the oscillator completes a half cycle itcauses an impulse generating circuit to .produce an impulse which res one of the tubes of the counting chain, and each tube, as it fires, conditions the succeeding tube to be fired by the following impulse. Thus the tubes of the counting chain are fired in succession by the successive half cycles of the signal wave until the tube associated with the chosen selecting lead is iired. The firing of this tube applies a voltage to the recycling circuit, which causes a tube to be energized that quenches the oscillator and further causes the line coupling tube to be so conditioned as to prevent the transmission thereafter of any further halfy cycles over the line. Thus at the proper which, under the control of the aforementioned 56 instant, the transmission of the line signal over the line LN terminates at the end of the proper half cycle. It an even number of half cycles have been generated by the oscillator OC, the same will stop almost instantaneously. n the other hand, if an odd number of half cycles have been produced. the oscillator will continue operating to produce the succeeding even half cycle since the current inthe elements of the oscillator is then owing in the non-conductive direction of the oscillator stop tube. This half cycle, however, is prevented from being applied to the line by the line clamp tube D.

After a .short delay, one of the tubes of the recycling circuit res, causing the tubes of the counting chain to be extinguished but still maintaining the oscillator stopped and the line coupling tube inthe non-transmitting condition. The circuit is thus returned to its initial condition, ready for the transmission of the next signal wave.

In the present embodiment of the invention, the transmitter has been arranged to send a desired digit either singly or continuously. For

` the latter type of operation, the recycling circuit is arranged so that, as long as a connection is maintained between the common lead and a selecting lead, the signal corresponding to the selection will be represented with a recycling pause between groups of half cycles of about ten milliseconds.

In the receiver, during an interval when no vsignal is being received, all tubes of the 'counting chain C'IRi-CTRU are maintained in the nonconducting condition. When a signal is received, the ilrst half cycle, which is positive, causes an essentially square negative Wave, produced in the anode circuit of the first detector, to produce a positive square wave in the anode circuit of the inverter associated with this detector. This charges a condenser associated with the recycling circuit, the latter then acting to apply energizing potential to anodes of the tubes in the counting chain. Near the end of the first half cycle of the signal train, the first detector cuts oi, causing the associated inverter and impulse ampliiier to apply a positive voltage impulse to the odd tube/s of the counting chain. The iirst tube of this chain being the only one normally primed, res, priming the first marking tubek and the second counting tube. Near the end of the vsecond half cycle, the second detector cuts oil', ap-

plying a positive square wave to the recycling circuit.` The condenser of this circuit is arranged so as to discharge with comparative slowness and hence to prevent the recycling function from occurring during the interval between the termination of the positive square wave produced by the i'lrst detectors inverter and the beginning of the one produced by the second detector. Near the end of the second half cycle, current flow is initiated in the anode circuit of the second detector, causing the associated impulse amplier to apply a positive voltage impulse to the even number counting tubes. Since the second tube of this chain is now primed by the conducting condition of the first tube, it fires, priming the third counting tube and the second marking tube and removing the priming condition from the first marking tube. In a like manner the counting tubes re in turn, each priming the corresponding marking tube and the following counting tube and removing the priming'condition from the preceding marking tube. When the last half cycle of the signal train i received, the positive square waves are no longer n 4 applied to the recycling circuit by the first detectors inverter and the second detector. The recycling circuit condenser discharges, causing the recycling circuit to apply a positive impulse to all marking tubes and immediately thereafter to extinguish all counting tubes. Since at this time the only primed marking tube is that corresponding to the last fired counting tube, it is red by the impulse and acts to extinguish any other,

.the main gap of recycling tube GI is thereby applied between the anode and cathode thereof, positive potential from positive battery +V being applied through-the contacts of key K and resistor RI to the anodeof tube Gl, and negative potential being applied to the cathode of said tube through the voltage divider composed of grounded resistor RI3 and serial resistors R1 and R6 connected, in parallelwith resistor RIB, to battery -V. The difference of potential'thus applied between the cathode and anode of tube GI is sufiicient to .cause the ionization of its main gap and the same is thereby rendered conducting t-o draw current therethrough over the abovetraced circuit, whereupon ecrtain specific potentials are made available at the terminals of various electrodes, terminals and conductors connected with the circuit as indicated below:

The current flowing through the cathodeanode circuit of tube GI causes a potential to be available at the left terminal of resistor R6 which is applied by direct connection to the grid of the upper triode of vacuum tube B.y The ohmic value of resistor R6 is so computed that the potential applied to this grid will be such that the resu1ttube, to positive battery +V through resistor R8 and, in parallel therewith, resistor R15 to ground,l

The potential available at the junction point of resistors R15, R8 and R9 consequent to this iiow of current is suiiiicently less positive than the full potential of the battery +V as to be a little above the cut-oli" point of tube C. Since the cathode of the tube C is connected to allof the anodes of the gas-iilled tubes CTI-CTI) and since the cathode's of the latter have a negative potential applied thereto from negative battery -V through an undesignated resistance individual to each of the cathodes, the trickle of an infinitesiv cathode of tube which potential, however, is less than required to s tain conductivity. However, since at this time all these tubes are inactive ampere or two is iiowing through them as above set forth, the application of less than sustaining positive potential to the anodes thereof by the C will have no effect.

The current through the anode-cathode circuit of tube GI is also effective in producing another less negative potential which appears at the right terminal oi resistor R6 and is applied, through resistor R2I to the-grid of the lower triode of tube B. Since negative battery through resistor R22, with resistor R90 shunted to ground is connected to the cathode of this lower triode, and the anode thereof is connected to the upper termina-l of the oscillator coil OC (the lower plate of condenser OCN and the lower terminal of the coil OC both being connected to ground), current will flow through this lower triode to ground through the coil OC. The small potential developed at the upper terminal of the coil OC in consequence of this current now holds the condenser OCN charged to the value thereof. Inasmuch as the current thus flowing is a direct current, oscillation of the energy stored in the condenser OCN and the coil OC is thus prevented so long as the current continues to flow through even though a microthe Ilower triode of tube B. Under these condiwill be produced for'transmission over the line LN.

It will be observed that the upper grid of the line clamp vacuum tube D is connected to the common terminal of resistors RI2, RIE and RI1 and that the lower grid is connected to the common terminal of resistors RII, RM and Rl8. Resistors RI4 battery +V via the contacts of key K; resistors RI'I and RIB are connected, over conductor I, to the lower moving contact of each of the numerical keys 1-0 of the key-set KS and to a voltage divider comprising resistors R20 and R5 bridged between battery --V to ground; while resistors RII andvRIZ are connected to the cathe ode of tubeGI. Now resistors RII, RI2, RIA, RI5, RH, RI8 and resistors R20 and R5 (the latter two resistors comprising a voltage divider) are computed to such values that when tube GI is rendered conducting, the grids of both triodes of tube D are rendered relatively positive, and if signal voltages be applied current will ow' through both triodes effectively to short-circuit the line LN as subsequently set forth.

It will further be noted which the signals are to be transmitted is connected to the cathode of the line amplifier tube L and, also, to the left terminal ofthe low retions n0 oscillations sistance resistor R23 which has its right terminal connected to ground.` Resistors R24-R28 form a network which interconnects the grid of the line ampliiier tube L and the mid-terminal of oscillating coil OC, and the object of this network is to couple the oscillator coil OC with the line LN and with means to stop instantly the transmission of signals over the line LN through the control exercisedv by both triodes of tube D. It will also be observed that the anode of the upper triode of tube D is connected to ground and that the cathode is connected to the aforementioned resistance networkat the junction of resistors R26 and R21,",whereas the anode of the lower triode is connected to the network at the junction of resistors R25 and R26 while the cathode is connected to ground.. -Since each triode or the vacuum tube D conducts in one dithat the line LN over and RIS are connected to positive tial when tube GI is conducting, it follows thatk one triode of tube D acts as a low resistance cir- Acuit between the network and ground for, curl rents generated in the direction ci its conductivity and the other triode is a low resistance cir- Cuit between the network and ground for currents generated in the direction of its own conductivity, thus preventing tube L from transmitting signals over the line. In other words, as long as key K alone is operated and none of the numerical keys 1,0 oi key-set KS is operated, the condition of the transmitter is such that the oscillator coil OC is blocked, less than sustaining potential is applied to the anodes of the tubes CTI-CTO ci the counting chain and a high attenuation is established across the line LN by the triodes of tube D to prevent currents in either direction from getting through.

The present embodiment of the invention is arranged either for the repetitive transmission of the same digit or for the single transmission of one digit only, the digit transmitted in either case being controlled by Whichever numerical key of the key-set KS is depressed, key S2, in its operated position. controlling the transmission of a single train of impulses and in its normal position controlling the repetitive transmission of the same train of pulses indicated by the operated numerical key. Assume, therefore, that a single signal train of pulses corresponding to a "5 selection is lto be transmitted. With key S2 operated, the numerical key 5 of key-set KS is then operated. With key S2 operated, resistor R35 which is connected to the anode of the tube G2 and to the left plate of condenser C3 is grounded, and since current for the circuit oi tube G2 is drawn from battery +V through resistor R2, the grounding of resistor R35 causes it to be connected in shunt with resistor R2 so that .the potential available at the anode o'f tube G2 for applying a charge to the left 4plate of condenser C3 is less than that available through the anode of tube GI forchargingthe right plate of said condenser. 5 connects, through its lower contacts, the cathode of counting tube CT5 to conductor I, while through its upper contacts it completes a charging circuit for condenser C2 of large capacity and condenser CI of relatively smaller capacity, the charging circuit of condenser C2 extending from positive battery +V, contacts ofvkey K, resistor R30, upper contacts of key 5, condenser C2 to ground. The charging circuit for condenser CI extends from battery +V through contacts of key K, resistor R30, upper contacts of key 5,

left operated contacts of key S2, condenser CI. resistor R3I to the potentiometer arm of resistor R32 (which is one of the resistance elements of the potentiometer network extending from battery -V to ground via resistors R3, R32, R33, right-hand inner operated contacts of key S2 to ground). The impulse thus created in the condenser CI raises the potential of the control anode of tube G2 sufficiently to cause ionization of the critical gap thereof, inasmuch as the cathode is connected to lnegative battery -V. This ionization spreads to the main gap since positive battery from source +V is applied to the anode of the tube via resistor R2 and the' The operation of key A the tube Gi causes the assensoY y upper contacts of key`fclose before its lower This, of course, could be obviated by a of the key contacts.

There is, moreover, a relatively large capacity CS connected between the anode of tube Gi and that oi tube G2. During the conductivity4 of tube Gl, the right plate of this condenser acquires a charge, of course, which depends upon the potential available at the anode of the tube Gl. When tube G2 lres, a parallel path to resistor R35 is established through tube G2 thus lowering the potential at the anode of tube G2. The lowering of the potential on the left-hand platev of condenser C3 (connected to the anode oi' tube G2) causes condenser CS to begin to charge and since the charging current is drawn through resistor Rl, the anode of tube Gl is momentarily made much less positive and the lattertube is extinguished. A negative source of voltage is furnished to the cathode of tube Gi via its connection '4to the junction of resistors RS, RIE and Ri, which resistors form part of a potentiometer circuit extending from negative battery V, .via the combination of resistors RIS in parallel withl serially-connected resistors Rl and R6, and thence via resistor R43 to ground. The extinguishing of tube GI causes the ow of plate current in this potentiometer circuit to cease, and the potential of the cathode, and of lead 2 connected thereto, to become more negative. 'I'he grids of both triodes of tube D, by virtue of their connection to lead 2 vla resistors contacts. sequence adjustment A RH and Rl2, assume a negative polarity, said grids now eiectively preventing any current from owing through their associated anode-cathode circuits so that any energy which is thereafter produced by the oscillator is applied to the amplifying tube L instead of being short-circuited to ground through the triodes of tube D. 'I'he signal applied to the grid of tube L will thereafter partly be carried to ground over resistor R23 and partly applied over the line conductor LN to the receiver.

The extinguishing of tube GI further causes the potential at the junction of resistors R1 and R6 to become more negative, and this potential is applied to the grid of the upper triode of tube B.' In a similar manner the extinguishing .of

potential at the junction of resistors R2I and R34 to become more negative and this potential is applied to the grid oi' the lower triode of tube B. The lower triode 0f tube. supply the oscillator coil OC with direct current duringthe times thatthe grid of said lower triode is positive; that is, during the time when tube GI is conducting. Hence, when tube GI is extinguished and the lower grid of tube B is made negative as an indirect result of theconductivity of tube G2, thiscurrent is suppressed and the energy stored inthe oscillator coil OC and condenser OCN begins to oscillate to produce a continuous train of alternating current waves as set forth in the above-mentioned patent, the lower triode of tube A functioning to supply the required energy to produce sustained oscillations. Since the anode ofthe lower triode of tube B is connected to the common terminal of oscillator coil OC and condenser OCN, the ilrst half cycle of the current will be positive.

It will be remembered that during the conductivity of tube GI the current flowing in the 1S IeInOVed.

B, it will be remembered, operates to y C is made more cathode-anode circuit ,thereof caused the grid ot the upper triode of tube B to be maintained at a positive potential so that this triode would conduct and that, in consequence, a relatively negative potential was applied to the grid of tube C which established an inappreciable current through the anode-cathode circuit thereof. including the anode-cathodepath of each gaslled tube in the counting chain GTi-CTU. Now When tube Gl is extinguished, cessation of the anode-cathode current through the upper triode of tube B causes the anode to become more positive in consequence oi' which the grid oil-tube positive. The greater current now owing'through anode-cathode 'circuit of tube C raises the available potential at the anode of each oi' the counting tubes CTl-C'Iii to a value such that, when one oi them is rendered conducting through its control gap as 4hereinafter set forth, the voltage available at the anode of that tube from the cathode ci' tube vC will cause said tube in the counting chain to become conn ducting throughvitsmain gap, thus causing it to remain operated when the initial breakdown' voltage between its cathode and control anode yescalator is picked ou the oscillator coil OCand ap- R2B whence, through re- The output of the mid-terminal of the plied to the resistor sistor R29, part of it and whence, through a voltage divider composed of Yresistors R27, R26, R25 and a portion of the, resistor Rit, a part of it is applied to the grid of the` line amplifying tube L, whereby the anode-cathode current in this tube is caused to :be modulated in accordance with the character of the oscillating voltage applied to the grid thereof which, in turn, is proportional to, and in accordance with, the character 'of the voltage produced by the oscillator coil OC. The anodecathode oscillating current in the line tube L passes through resistor R23 which is connected between the cathode of the tube and ground, and the voltage drop developed across this resistor is applied to the line conductor LN for transmission thereover to the receiver which, as set forth hereinafter, responds'to the oscillations and provides a suitable indication thereof. It should be` noted at this point that if the grids of both triodes of tube D werenot rendered negative when tube Gl is extinguished, the oscillating energy, instead of being applied to the line LN as above noted, will pass to ground, the positive half cycles of the energy passing through one triode of. tube D and the negative half cycles passing through theother triode of tube D. 'I'he fact that the grids of this'tube are rendered negative at the time tube Gl vis extinguished causes the triodes of this tube to present practically an open circuit to the potentiometer network between the oscillator and the grid of the line tube L so that the oscillations are reproduced in tube L .and passed into the line conductor LN,

The upper triode of tube A together with transformer IT form an The grid of this triode is connected serially through the high resistance resistor R16 to the common terminal of the oscillating coil OC and condenser OCN", and the alternating voltages prof duced by the oscillator correspondingly alter the .potential of said grid. These voltages, however, are so large that they drive the grid from the point of cut-olf to a positive value, a fact which, coupled with the additional fact of the high resistance of resistor R18, causes an anode-cathode is drained oil to ground impulse producing device.`

Awhich supplies the bias.

9 current flowing through the upper triode of tube A to be essentially a square top wave. Now the first half cycle produced by the oscillator is positive and during this period current will ilow in the upper triode of tube A through a circuit which traces from positive battery -1-V`through resistor R9I, the two left, or primary, windings of transformer IT, through the anode-cathode path, to ground on the cathode. At the end of the rst half cycle, the grid of the upper triode of tube A becomes negative with respect to its cathode, and anode current, therefore, ceases to ow through the primary of transformer IT. The cessation of current is'very abrupt due to the square-top character of the wave, and a sharp impulse is thereby caused to be generated in the secondary winding of transformer IT, which appears as a positive impulse at terminal 2 connecting with the control anodes of the odd numbered tubes CTI-CTB, and as a negative impulse at terminal I` which is connected to thel control anodes of the even numbered tubes CTZ-CTO. The control anode of tube CTI, however, is at ground potential. Since the cathodes of all the counting tubes CTI-CTU are connected to negative battery -V through appropriate resistances, the application of the positive impulse to the control anode of tube CTI via its associated undesignated condenser raises the potential of said control anode to a value which establishes a control gap breakdown difference of potential between it and the negative potential available at the cathode, causing the control gap to ionize. Since an appropriate positive potential is, at this time, also4 applied to the anodes of all counting tubes from the cathode of tube C, as previously explained, ionization of tube CTI spreads to the main gap, in consequence of which the tube will remain in a conducting state upon the termination of the impulse, the current flow path through the main gap of tube CTI tracing from positive battery +V through the anode -cathodev path of tube C,

anode-cathode path through'the tube CTI, and

the undesignated cathode resistance to negative battery -V. The ow of current through the 'cathode resistor of tube CTI produces a relatively positive potential at the cathode which is applied to the control anode of the next tube CTZ through an interconnecting resistor. This potential, however, is not suiicient to cause the breakdown of the control gap of tube CTZ, said potential serving only to bias the control anode of this tube for breakdown purposes upon the application thereto of an additional potential over that The other odd numbered tubes to whose control anodes the positive impulse from transformer IT is applied at the time it is applied to the control anode of tube CTI are not red with tube CTI because, while the control anode of tube CTI is normally at ground potential, the control anodes of the other odd numbered tubes are Amaintained at a voltage more negative than ground by means of the resistance network interconnecting -V and ground.

At the end of the second half cycle, current flow is again initiated in the plate circuit of the upper triode of tube A, the change in current being effective to produce an impulse in the primary windings of transformer IT which is opposite in polarity to that produced at the end of the rst half cycle and, consequently, causing a positive impulse to appear at the No. 1 terminal of the secondary windings of transformer IT and a negative impulse at the No. 2 terminal.

relatively positively biased by the cathode potential derived from the conductivity of tube CTI,

the positive impulse now applied to the control anode of tube CTZ will cause it to re, in turn conditioning the control anode of tube GT3 to be responsive to the next'positive impulse to be applied thereto from the No. 2 terminal of transformer IT.V A series combination of v aristor VR and resistor R36 shunted across the two primary windings of transformer 1T serves to equalize the amplitude of the impulses produced at the ends of the odd and even half cycles, which amplitudes would otherwise be unequal because the inductance of the primary winding causes its current to rise more gradually at the ends of even half-cycles than it decays at the ends of odd halfcycles.

In the above manner, counting tubes CTI-CTS fire, each in turn conditioning the succeeding tube. When, at the end of two and a half cycles, tube CT5 fires, the flow of current between its anode and cathode renders said cathode relatively positive. Since the cathode of this tube is connected to conductornl through the lower contacts of the numeral key 5, and the conductor is, in turn, connected to the grid of the lower triode of tube B via resistor R34 and to the grids of both triodes of tube D via resistors RII and RIB, all of said grids are rendered positive. As a result the anode-cathode impedance of both triodes ofr tube D is reduced to a fairly low value, the signal from the oscillator is greatly attenuatedacross the potentiometer resistor R24, and tube L is prevented, after the transmission of two and one-half cycles, from applying any further signal energy whatsoever to the line conductor LN. v

Due to the fact that, at the end of the two and one-half cycles, current in the oscillator OC is flowing toward ground and since the upper terminal of the oscillator is connected to the lower anode of tube B, the triode of which this anode is a part will fail to conduct even though its grid is positive with `respect to its cathode. The oscillator OC, therefore, fails to stop until, at some time later near the end of the third cycle, the current reverses, the anode of the lower triode of tube B becomes more positive than the cathode and current again ilows through this triode to thereby return the oscillator to its vsteady state stopped condition as originally described. This,

however, will in no way aiect the line since, as

before stated, the conductivity of the two triodes of vtube D prevents such voltage from being impressed on the grid of tube L even though the oscillator 0C is still functioning.

The positive potential upon conductor I is also applied to the control anode of tube GI through resi-Stor R31. After a delay due to the time required to charge condenser C4, tube GI fires across its control gap and thence across its main gap to cause its anode potential to become more negative and its cathode potential to become more positive. Due to the connection of condenser C3 between the anode of tube GI and that of tube G2 and due to the fact that thisy condenser is charged to the voltage of the drop across resistor R2, the fact that the anode of tube GI is rendered more negative by its conductivity causes is made more positive than it was before, and this positive potential is, of course; applied to the grid of the upper triode of tube B to cause current to flow through its anode-cathode circuit. The anode being rendered more negative by the current flow, the relatively negative voltage thereof is applied to the grid of tube C in consequence of which the current through the anode-cathode is reduced and the potential of the cathode becomes su'lciently negative so that the voltageA applied to the anodes of the counting tubes is insuflicient tomaintain a discharge. T ubes CTI to CTB therefore become extinguished.

The extinguishment of tube CTB causes conductor I to become more negative, but the effect of this on the grids of tube D and that of the lower triode of tube B is compensated for by the fact that the cathode of tube GI has become positive by an equal amount. The reason for this is because the more positive potential at the cathode of tube GI is applied to the lower grid of tube B via resistor R2I at the same time that conductor I supplies a less positive voltage to the same grid via resistor R34. In the same manner, the more positive potential on the cathode of tube GI is applied to the two grids of tube D via resistors RIZ and RII at that same time that conductor I supplies a less positive voltage to these grids via resistors RI1 and RI8. Since the firing of tube GI and the extinguishing of tube CTS occur practically simultaneously, the grids oi `the above triodes remain at a substantially constant potenf tial. The circuit is thus returned to its initial condition except for the fact that, since numerical key 5 is closed, condensers CI and C2 remain charged over previously described paths and, therefore, no impulse will be produced across condenser CI to ilre tube G2. To produce the impulse, numerical key 5 is released and key 5 or some other numerical key reoperated. Upon release, condensers C2 and CI are discharged and, upon reoperation, condenser C2 will be charged and later condenser CI' will be charged as previously described, producing an impulse that will cause tube G2 to fire and the operations above s described to be repeated.

Other signals may be sent in the same manner as above described except that in the case of even numbered signals the oscillator stops immediately 'at the end of the last half-cycle of the signal since the direction of current ow at this time is in the conductive direction of the lower triode of tube B and the voltage applied to the plate of this triode is more positive than that of the cathode.

For the continuous transmission of the same signal only the numerical key correspondng to the number of the signal to be transmitted is operated, key S2 being kept in its unoperated condition. At the end of each signal train when tube GI has red and extinguished tube G2, the latter tube retires across its control gap after a delay which may be controlled by the adjustment of the potentiometer R32. Ihe reason for this is that when tube GI extinguishes tube G2, the anode potential of the latter becomes morepositive with respect to the potential supplied by battery -V at the cathode. However, due to the fact that key S2 is normal, the control anode is tied to the main anode via resistors R3 I, R32 and R33. Hence the potential of the control anode similarly becomes more positive with respect to the potential available at the cathode. Both these potentials, however, are derived from the charging circuit of condenser C3 which includes battery -V, resistors R3, R32. and R33, right inner normal contacts of key S2, condenser C3, resistor RI, contact of key K to positive battery +V; in parallel therewith there is also the potential available at the lower terminal of resistor RI due to the conductivity of tube GI, and also the parallel resistor R2 to battery +V through the contacts of key K. The potential applied to the control anode of tube GI, being derived from the above network and being a. function of time, can be derived for any particular time value by suitably adjusting the potentiometer R32. When the appropriate value of potential is reached, tube G2 will tlreacross its control gap and the operations above described will be repeated. Thus, without any further operation of keys, repetitive signals will be transmitted.

The delay feature in the flringand extinguishing of tubes GI and G2 and the correspondingly necessary joint control of the recycling operations by the potentials on conductor I an-d at the cathode of tube GI are necessary in order to obtain a short recycling time in continuous sending. In the transmission of a "1 signal, vfor example, the duration of the signal may be 2 milliseconds. If tube GI were to be fired immediately by the positive potential on conductor I, it could remain extinguished for only 2 milliseconds whereas the deionization of a tube of this type requires at least 5 milliseconds and the value of condenser C3 is such as to delay the rise of plate potential suillciently t0 permit such time for deionization. However, with a 4-mi1lisecond delay in the firing .0f tube GI (which can be arranged by the proper choice of values for .condenser C4 and resistor R31), it can remain extinguished for 6 milliseconds in the transmission of a 1 signal. Thus the circuit is so arrangedythat during continuous transmission of this shortestA signal combination, and with a recycling time of 10 milliseconds, tubes GI and G2 commutate at approximately equal intervals.

The operation of the receiver will now be described. It is assumed that filament current for the vacuum tubes .of the receiver ows through the filaments thereof from any suitable source of current (not shown) and that, in consequence, the respective cathodes of the tubes are in an emitting condition. In the no-signal condition, no current ow through the upper triode of detector tube DETI since the grid thereof is maintained at a cut-oir negative potential which is derived from a voltage divider comprising resistors R40 connected to negative battery -V through conductor 5, REI and R45, the latter being connected to a positive source of potential -l-V over conductor 2. The ohmic values of resistors RSI and R40 are computed to a value that will permit no current ow through the anode-cathode circuit of the upper triode of tube DETI. On the other hand, current is flowing through the anodecathode circuit of the upper triode of detector tube DET2 because the potential at the grid thereof isavailable from the voltage divider comprising resistors R4I connected to negative battery -V over conductor 5, and resistors R44 and R45, the latter being connected to positive bat-y tery as above mentioned. The ohmic value of resistors R44 and R4IV is computed to a value that will permit current now through the anode-cathof this voltage divider are computed so that the normal potential on said grid permits current to ow through the upper anode-cathodeof said tube INV, the path of said circuit tracing from positive battery +V, conductor 2, resistor R64, through the upper anode-cathode path of tube INV to cathode' ground. Thus current flows in the anode-cathode circuits of the upper triodes of tube DETZ and the inverter tube INV and the potentials on the anodes of the upper triodes of both tubes are applied through resistors R41 and R50 respectively to the plate and grid of the lower triode of tube RE. Resistor R48 is connected to and through RI to condenser A and to battery +V over conductor 5 so that, with the positive potentials on the. anodes of the upper triodes of tubes DETZ and INV obtaining at this time', the potential at the, junction point is negative with respect to ground and causes condenser A to be charged negatively through resistor R5I.- The negative potential on condenser A is applied to the grid of the upper triode of the recycling tube RE via resistor R52, thereby causing no current to now through the anode-cathode circuit thereof.

. which, through resistor R55, is applied to the grid since the grid of the iower triode of the inverter l tube INV is connected to the upper anode of tube RE through resistor R82, the potential on this grid, as modified by the connection of said grid to negative battery -V via resistor R81 is, therefore, positive with respect to its cathode. This permits current to llow through the anode-cathode of the lower triode of tube INV, and the potential on the anode of this triode, which is relatively negativel'due to the ow of plate current from positive battery through resistor R19 is transmitted to the grid of the extinguishing tube EXT through resistors R54 and R53. The value of this potential causes only a very slight current ow through the anode-cathode of tube EXT and the anode-cathodes of each of the gas-lled tubes of the counting chain C'I'RI-CTRB to negative battery -V, which maintains the cathode potential of tube EXT sufficiently negative that the voltage applied to the anodes of the tubes CTRI-CTRD of the counting chain is insufficient' to maintain a discharge through any of these lastmentioned tubes.

In the rio-signal condition upon line LN, the

of the lower triode, causing a further amplified change in voltage to appear inthe anode of said lower triode.

'Ihe first half cycle of the incoming signal, which is positive, is applied to the grid of the upper triode of tube RL, causing the potential thereof to be rendered less negative. More current now flows through the anode-cathode circuit of the upper triode of this tube, and the potential developed across resistor R55 as a result of the increase in current renders the grid of the lower triode more negative than previously, and thereby increases the potential of the lower anode. For small Values of signal voltage this increase in potential is a'two-stage amplication of the potential of the rst half cycle of the incoming signal. For larger values of signal voltage the peak of the half-cycle may be flattened las the grid of the lower triode attains a potential which causes the cessation of current in the anode-cathode path, but this will not adversely aiiect the action of the receiver.

The potentials across the voltage divider comprising resistors RSI and R40 and across the voltage divider comprisingresistors R44 and R4! which result from the amplication of the signal are applied, respectively, to the upper grids of detector tubes DETI and DET2. Since the rst received signal is positive, these grids become more positive and, at some value of signal which exceeds the noise level on the line circuit LN, current flows through the anode-cathode circuit of the upper triode of detector tube DETI. The current iiow in said triode causes the potential of its anode to become more negative, 4and this more negative potential is applied, via resistor R46, to the grid of the upper triode of inverter tube INV. The anode potential of this triode now becomes more positive, but this has little effect on the grid of the lower triode of tube DETI to which it is connectedby way of condenser B since its grid is already positive with respect to its cathode due to the potential available on said positive battery +V on conductor 2.

grid of the upper triode of the line receiving tube RL is maintained at a slightly negative potential through resistor R58, variable resistor R59 and resistor R60 which is connected to negative battery -V. Under this condition, some current flows through the upper triode, path which extends from positive battery +V, resistor R51, anode-cathode path to cathode resistance ground. The anode of the upper triode of tube RL is, therefore, at a potential less positive than the full positive battery potential, and this potential, as modied by potentiometer comprising resistors R andv R56 to negative battery V, is connected to the grid of the lower triode of this tube, thereby maintaining said grid at a potential which will cause some current to ow through the' grid as a consequence of its connection to the common terminal of resistors R63 and R62. Since little or`no current is flowing through the upper triode of tube INV, the anode thereof is relatively positive by virtue of the small voltage drop in resistor R64 which interconnects said anode and Hence, while this anode is relatively positive during the time that no current ows through the associated anode-cathode circuit, this positive potential is also available at the anode of the lower triode of the recycling tube RE, which is used as a diode, so that current ilows through the anode-cathode circuit and a positive charge is applied to condenser A. Since the plate of this condenser is connected to the grid of the upper triode of the recycling tube RE via resistor R52, said upper grid likewise acquires a positive potential the effectv of which is to cause the associated upper anode I of this tube to become more negative, carrying with it the grid of the lower triode of tube INV. This causes the potential at the anode of the latter triode of tube INV to become more positive, carrying the grid of tube-EXT towards positive also. Thus, the cathode of tube EXT is permitted to become suiciently positive to apply to the anodes of the counting tubes CTRl-CTRO an anode-to-cathode potential greater than their sustaining potentials. l

The change toward positive of the anode of the lower triode of tube INV applies a positive im- 15 pulse through condenser D to the grid of triode SEL. Since said grid already has a positive potential applied to it from resistors RI00, RIOS and RI03, the anode-cathode current is little afl fected and hence the anode potential remains substantially constant. It should be remembered that during the reception ofthe first half-cycle of signal, positive potential was not only applied to the grid of the upper triode of tube DETI as already explained, but also to the grid of the upper triode of tube DET2. Since this merely constituted an increase of the existing positive potential applied through resistor R42 to said grid, and

-in consequence of the large value of resistor R42,

only a small increase in grid current results, and there is practically no change in the anode-cathode current in the upper triode of vtube DET2. The anode potential therefore remains substantially constant.

.Near the end of the first half cyc1e of the smus- 20 oidal half wave produced by the transmitter, the grid of the upper triode of tube DETI becomes negative with respect to the cathode, the signal being applied to the gridl of thisupper triode through the two-stage amplier comprising both triodes of tube RL. The anode potential on the anode of the upper triode of tube DETI, therefore, increases in a positivev direction which, in

nitude of this impulse is insuiiicient to re the control gaps of these tubes, but since the control anode of tube CTRI is provided with a positive bias relative to its cathode through resistors RSS,

e R61 connected to ground and resistor R66 in parallel thereto connected to negative battery -V, tube CTRI ilres across its control gap to the negative potential at the cathode supplied from battery -V through an undesignated resistor. The tube then fires across its main gap to the positive potential supplied by the cathode of tube EXT and remains in a conductive state until this potential is removed or reversed.

When tube vC'IRI ilres, the current drawn through its anode-cathode circuit causes the cathode potential to become more positive, car'- rying with it, in the positive direction, the control anodes of tubes CTR2 and SI, the latter tube being the rst tube in the marking chain. The potential for the control anode of tube CTRZ is applied through resistor R69 while that for the control anode of tube SI is applied through resistor R10. The applied potentials are, however, insufficient to re either of these two tubes be'- cause, in the case of tube CTR2, the diiference in potential between thecontrol anode and the cathode will not reach the breakdown value until a positive impulse is applied to its control anode by way of condenser CN 2 Since the positive im-v pulse which red tube C'I'RI. is also applied to control anodes of all the odd-numbered tubes but not to the control anodes of the even-numbered ones, tube CTR2 cannot be fired on the same impulse which red CTRI. In the case of tube SI, the potential applied to its control anode is insulclent to ilre said gap in the absence of large positive potential at the plate of tube SEL.

Soon after the beginning of the second halfcycle of the signal train, which second lhalf-cycle triode of tube INV, said potential being applied v through resistor R50 and the lower diode of tube RE. In other Words, during the reception of a train of positive and negative half-cycles, condenser A is continually charged'. Now resistor RSI, which is virtually short-circuited during the charging of condenser A, appears in the discharge circuit of this condenser, which discharge circuit terminates at' the potential available at the common terminal of resistors R48, R50 and R41. The ohmic resistance of resistor RSI and the capacity of condenser A are so computed that the time constant on discharge is long enough to prevent appreciable discharge of the condenser during the short instants between the latter part of each half-cycle and the early part oi. the following half-cycle and, therefore, the potential on the grid of the upper triode of said tube RE (via resistor R52) is prevented from becoming negative.

Near the end of the second half-cycle, the grid of the upper triode of tube DET2 becomes positive with respect to the cathode. The anode potential now becomes more negative, applying a negative impulse through condenser C, tothe 40 grid of the lower triode of this tube. The resulting positive impuls'e on the anode of this lower triode is applied, through condensers CN2, CN4,

CNS, CNB and CNO to the control anodes of the even-numbered tubes CTR2, CTRA, CTRG, CTR8 and CTRO. Unaided, the magnitude of this impulse is insufilcient to fire the control gaps' of these tubes. Since, however, the current in the cathode circuit of. tube CTRI has caused a positive bias to be applied to the control anode of` the ilow of current in the cathode resistor of.

tube CTRI. In this way, the tubesCTR of the counting chain are fired in succession, each in turn biasing the control anode of the corresponding marking tube and the succeeding countingr tube, and neutralizinguthe bias of the preceding marking tube. It--will now be `shown that, inM

response to operatio'rs following the reception of a last pulse or'vhalf cycle in a signal train, the

" marking tube orresponding to the last fired counting tube will also -be fired and remain in the conducting state, thus indicating by its numerical designation the number of half cycles received. This tube remains in a fired condition until the last half cycle of a succeeding signal train is received, at which time the marking tube previously red is extinguished and the marking casacca tube indicative of the last pulse in the second signal train is fired, Obviously, il both signal trains contain the same number of half cycles, the same marking tube will remain lighted.

Suppose, for example, Vthat signal is being received and that a previous signal train of three half cycles (3), having been received, will have caused marking tube S3 to have become fired and to have remain lighted in the manner shortly to be explained. After the end of the fifth half cycle, no further signals will be' received. Condenser A will then discharge through resistor RSI to the point where the grid of the upper triode of the recycling tube RE becomes negative with respect to its cathode. The fiow oianode current in this triode will thus be interrupted and the anode potential will become more positive, carrying with it the grid of the lower triode of tube INV. The anode potential of this latter triode now becomes more negativeapplying a negative impulse through condenser D, to the grid of tube SEL. The resulting positive plate Apotential of tube SEL causes a positive impulse to be applied through conductor 6 and condensers SNI-SND to the control anodes of marking tubes Sl-Sll', firing tube S5 since it is the only one of the marking tubes which is primed at this time.

In connection with tube S3, assumed to be previously conducting, the potential of its cathode is maintained at a constant positive value by the charge in condenser CC3 accumulated The more negative potential on the anode of the lower triode of tube INV is applied to the grid o! tube EXT by way of resistors R54 and R53, from whose junction point a condenser E is bridged to ground. Said condenser dela-ys the change o! potential at the grid of tube EXTl sufliciently long to permit the above-described action of tube SEL to take place. Thereafter, the negative potential on the grid of the tube EXT causes the cathode thereof to become more negative. The potential appliedthereby to the anodes of the counting tubes CTRI-CTRU is now no longer sufllcient to sustain a discharge. Hence, counting tubes CTRl-CTR5 extinguish. The marking tube S5, however, remains lighted. Otherwise the circuit is returned to its initial conidltion, ready for the receipt of the next signal tra n.

While we have described our invention in connection with its application to a specic signal transmitting and receiving arrangement, it is thereon by the voltage drop across the cathode resistor. It will also be noted that the anode current for any of the marking tubes is drawn through the resistor RBI, and the drop across.

this resistor, with one markingtube conducting, will still provide suflicient anode potential so that the diierence between said anode potential and the potential maintained at the cathode of a conducting marking tube, like tube S3 by its associated charged condenser C63, .will be suilicient to keep the tubein a conducting condition.

Now when tube S5 is fired subsequent to the reception of the fifth (and last) half-cycle of the second signal train, the current through resistor RBI is increased since current now flows through'both tubes S3 and S5. As a consequence,

the voltage across resistor RBI is also increased.

and the voltage available at the anode of the marking tubes is reduced a corresponding amount. Since condenser OC3 is charged to a positive potential and condenser CC5 is uncharged at the time tube S5 is iired, the potential difference Vbetween the cathode and anode of tube S3 is now reduced below the sustaining valve, in consequence of which tube S3 is extinguished. On the other hand, the potential difference between the anode and the cathode of tube S5 is the full dlierence between the potential on the anode and that of the potential divider connected between the negative battery -V and ground, Aand is suiiicient to maintain the tube S5 in a coriducting state.

It is now evident that if the second signal train contains the same number of half-cycles as the first signal train, said first train already having caused the lighting of the appropriate marking tube, this tube remains lighted continuously. Thus, if tube S5 is lighted, the sustaining voltage is undisturbed between the successive signals. Although lthe control anode of tube S5 will be primed in the regular course of operations as already described, such priming will, of course, have no effect upon the tube since it is already conducting,

understood that various other applications and embodiments thereof may be made by .those skilled in the art ywithout departing from the 'spirit of the invention as dened by the scope of the appended claims. Thus, a relay may be included in the anode circuit of each of the marking tubes, which will operate when the tube is rendered conducting, in turn operating a suitable register circuit that includes steering devices for switching the relays from one registerto the next, thus registering a series of numbers indicative of the number of half-cycles in each of the signal trains received.

It is also apparent that, by doubling the number of counting tubes and marking only every other pulse, the signal transmitted can be represented by the number of whole cycles instead of half cycles.

What is claimed is:

1. In a signaling system in combination, a line,

an oscillator connected to said line, electronic means normally effective 'to short-circuit said line, and controllable means for operating said oscillator and said electronic means whereby the former produces a predetermined number of half y cycles for application to said line and the latter will ilow through the anode-cathode path of removes the short-circuit from said line to cause said predetermined number of half cycles to be transmitted thereover, said controllable means being thereafter effective to quench said oscillator and to cause said electronic means to reestablish the short-circuit of said line to prevent spurious oscillations produced by said oscillator after quenching frombeing transmitted over said line.

2. In a signaling system in combination, a line, an oscillator adapted to produce a current wave substantially sinusoidal in character for transmission over said line, .a potentiometer connected between said line andsaid oscillator, a rst electronic device having its anode-cathode path connected at one point of said potentiometer in the direction of the current ilow of a positive half cycle of said current wave, a second electronic device having its cathode-anode path connected atl another point in said potentiometer in the direction of the current flow of a negative half cycle of said current wave, and means for applying a positive potential to the control electrodes of both of said electronic devices, whereby each half cycle of current generated'by said oscillator either device, depending upon its direction.

3. In a signaling system in combination, a line, an oscillator adapted to produce a current wave cycles of said current wave, a second electronic device having its cathode-anode path connected at another point of said potentiometer in the direction of the current flow of the negative half cycles of said current wave, means for applying a positive potential to the control electrodes of both of said electronic devices whereby each half cycle of current generated by said oscillator will iiow through the anode-cathode path of leither device depending upon its direction, andmeans -for changing the potential at the control electrodes of both of said electronic devices from positive to negative, whereby a high impedance is offered in the anode-.cathode path of said electronic devices to the current from said oscillator, and whereby in consequence of said high impedance said current isv applied to said line.

4. In an alternating current signaling system the combination with a transmission line of a transmitter connected to said line comprising an alternating current oscillator adapted to produce a current wave substantially sinusoidal in charcurrent wave and a path of low impedance to negative half cycles of a current wave, whereby any cycles oi' the current produced by said oscillator will pass through said paths, a pluralityy of numerical keys, a plurality or gas-lled tubes arranged as a counting chain, means responsive to operation of one of said numerical keys for selecting a tube corresponding to the digit of the key for starting the operation of said oscillator and for operating said electric coupling means to change said paths from low impedance to high impedance whereby the half cycles of the signal acter for transmission over said line, means for i determining the number of the positive and negative half cycles of said current to be transmitted over said line, an electronic counting chain responsive to said means for counting said number ofv half cycles, electronic means bridged between said oscillator and said line for short-circuiting positive and negative half cycles of said current vtransmission of the last half cycle oi.' the signal wave for reactivating said electronic means, whereby a short-circuit is again applied between said oscillator andsaid line and for stopping the operation of said oscillator.

5. In an alternating current signaling system adapted for the repetitive transmission of signals,

the combination with a transmission line, of an oscillator adapted to produce a current wave substantially sinusoidal in character for transmission over said line, va pair of gas-filled tubes ot which one is normally in a. conducting state, electronic coupling Ameans between said oscillator and said line responsive to said conductive. gaslled tube for'applying across said line a path of low impedance to the positive haii.' cycles or a current pass over said transmission line, a de- .tector circuit responsive to each half cycle of the signal current for producing an impulse to operate, in succession, the tubes in the chain, means responsive to the operation vof the selected tube for operating the other of said` pair of tubes, means responsive to the operation oi. the other of said pair of tubes for stopping said oscillator, for operating said electronic coupling means to change said paths from high to low impedance whereby the transmission of further half cycles, over said transmission line is prevented,v and for quenching the first of said pair of gas-nlled-tubes whereby said means for operating the rst of said pair of gas-lled tubes is again eiective to operate said tube to restart the transmission cycle, and means responsive to the yreoperation of the rst of said pair of gas-nlled tubes for quenching the second of said pair of gas-fille tubes. HENRY M. BASCOM.

ROBERT E. MASSONNEAU. BERNARD OSTENDORF, Ja. WILTON T. REA.

40 ille of this patent:

Number Name Date 2,248,937 Bellamy 1' July 15, 1941 2,192,217 Bellamy Mar. 5,A 1940 2,225,680 Boswau D ec. 24, 1940 2,096,954 Bellamy Oct. 26,1937

2,241,156 Powell May 6, 1941 2,373,134 Massonneau Apr. 10, 1945.`

2,332,300 Cook a O'ct. 19, 1943 1,882,010 Hershey Oct. 11, 1932 2,273,193 Helsing Feb. 17, 1942 1,930,609 Davidsmeyer Oct. 17, 1933 FOREIGN PATENTS Number Country 1 Date 355,705 Great Britain Aug. 24, 1941 485,703 Great Britain May 24, 1938 411,903

4UNITED STATES PATENTS Great Britain June 15, 1934

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