Sept. 24, 19-46. 2,408,313 L. R- HU‘NTER ET AL PHOTOELECTRI C COUNTER Filed Sept. 5, 1942 2 Sheets-Sheet l “824/5 ' %IIR ATTO I sePt- 24, 1946- 1.. R. HUNTER ET AL 2,408,313 PHOTOELECTRIC COUNTER Filed Sept. 5, 1942 BMWmk wk I -4UM_ h_ 2 Sheets-Sheet 2 Patented Sept. 24-, 1946 2,468,313 UNITED STATES PATENT OFFICE 2,408,313 PHOTOELECTRIC COUNTER Lyle R. Hunter, Clairton, and Oliver C. Levander, McKeesport, Pa. Application September 5, 1942, Serial No. 457,480 5 Claims. 1 In the preparation of bundles of metal sheets and the like for shipment, it becomes necessary 4 to know the number of sheets that are in each (01. 250-415) 2 Figure 3 represents a wiring diagram showing the circuits for the control of the mechanism. From the drawings it will be seen that the bundle. As the sheets move along the line of travel from the shears which cut the strip into the desired length of sheets, at a high rate of toelectric control, the cabinet being shown as mounted on a table I which comprises convey speed, counting mechanism must be utilized in ing instrumentalities for conveying the sheets to reference numeral 5 indicates a cabinet for a pho order to give an indication of the number of a piler 9. The photocell is activated by light from sheets which pass along the line of travel. suitable light sources, such as that indicated at In view of the high rate of travel of the sheets, 10 l l. A plurality of motors [3 drive a conveyor for it is found that all of the mechanical counting moving the sheets to the piler, and also for ac devices which are available up to this time are tuating an auxiliary conveyor l5 which receives inadequate to install for the desired purpose of discarded sorted sheets from the stock which is this invention, since the speed of actuation of all being handled by the equipment. such devices is not rapid enough to keep pace 15 The photoelectric counter, designated at IT, is with the travel of the sheets, and it has been located conveniently at an operator’s station l9, found in practice that every type of mechanical and it is controlled in the following manner, ref counter that is available has been tried but has erence being had to the diagram of Figure 3. been found to be a failure for the intended pur From this view, a photoelectric cell is indicated pose. 20 at 2 I, the cell 2| being in circuit with a rectifying In view of the many failures resulting from tube 23 which is positioned in the cabinet 5, and the installation of the mechanical counting de which receives current from a transformer 25, as vices, it has been necessary to resort to other is shown on the drawings. means for counting the rapidly moving sheets. The tube 23 is a standard radio rectifying tube, In view of this necessity, there has been evolved 25 known in the trade as “Type 80,” which receives an electrical control system for actuating a alternating current from the transformer 25, counting mechanism, the sensitiveness of the which current results when the transformer is electrical control system being such that an ac energized from a suitable source of 110 volt, 60 curate counting of the sheets is attained, quite regardless of the speed at which the sheets travel. In general terms, the present invention pro cycle alternating current. Each of the thyratron tubes employed in the system is essentially a hot cathode recti?er in vides a photoelectric cell in circuit with two thy which a control grid 4! has been placed between ratrdn rectifying tubes, current from which tubes the anode plate 43 and the cathode ?lament 45. is adapted to actuate a counting mechanism, In conventional operation of thyratron tubes, the or other electrical devices operable from the cur 35 cathode is of special construction, being heat in rent output of the thyratron tubes. This current sulated and of large emitting area, so that even is a continuously flowing pulsating direct current. when operated at low power it is capable of fur The arrangement of the apparatus is such that nishing thermionic current of a predetermined light from a suitable source is directed upon a speci?ed number of amperes. With the anode photoelectric cell through the spaces between at a de?nite potential with respect to the oath successive sheets moving along an operating line ode, no ciu~rent will pass until the grid potential which piles the sheets in suitable stacks or bun is raised above a certain critical value. When tiles for shipment to market. It will be under the grid potential is raised to this value, an are stood that a ?ash of light which is produced be suddenly starts and the full current ?ows, lim tween the sheets and falls upon the photoelec 45 ited only by the electron emission of the cathode tric cell must be sufficiently intense to activate and the resistance in the anode circuit. Once the photoelectric cell, and consequently, the more the arc starts, however, the grid loses control and rapid is the travel of the sheets, the greater must no longer has any e?ect on the discharge, re be the space therebetween. gardless of its potential. The are may be stopped The invention will be understood more readily only by removing the anode potential. from a consideration of the accompanying draw ings, wherein: In a thyratron tube, the grid can be used to start the current while applying an alternating Figure 1 represents a plan view of sheet han dling equipment; voltage to the anode. The are then goes out Figure 2 represents an elevation thereof; and 55 every half cycle while the anode is negative. It 2,408,313 3 4 will start during the next half cycle only if the grid potential is above its critical value. The present invention differs importantly from the foregoing, in that the discharge in the thy ratron tubes is controlled by the grid, the dis charge being stopped when a space between values all may be modi?ed to suit any particular installation. Potentiometer arm 5!? is connected through ?xed protective resistance 58 and conductor 58 to the cathode ‘60 of the photocell 2!. The anode 62 is connected through conductor 653 to the grids ill and ill’ of the thyratron tubes 3? and sheets passes a suitable light source for energiz 39, conductor 64- being connected to the grid til through resistance 55 and conductor 58, and to current negative voltage to be applied to the 10 the grid ti’ through resistance $5’ and conduc tor 68’. The resistances 55 and 06’ are employed grid during the instant that the photocell 2| is ‘for protective purposes and, in the illustrated energized, this voltage being greater than the embodiment of the invention, have a value of 4 alternating current potential between the anode ing the photoelectric cell, this latter, upon ener gizing, closing a circuit which enables a direct and cathode. ' The resulting interruption of the action of the 15 thyr-atron tube causes an actuation of the counter solenoid in a suitable direction to transmit mo tion to the counting device. As soon as each plate obscures the light source, megohms. The thyratron tubes Bl and 39 are similar, , and are provided with cathode ?laments 1B5, 45', respectively, and anode plates 83, 43’, respec tively. These elements are energized from sections of the photocell H is deenergized and the thyra 20 a secondary coil of a transformer 25', which is similar to transformer 25, the primary coils 20 tron circuit reestablished, this circuit being closed and Z!’ of the transformers 25, 25’ being ener during the time interval required for the sheet gized from a 60-cycle,‘1l0~volt alternating cur to travel completely across the light source. This rent supply. time is much longer than the time of ?ashes be Thus the cathode ?laments 45 and 35' are en tween the plates, and gives an opportunity for any 25 ergized by section 26’, which gives from about 2 lag in the circuit or counting device to have dis to about 5 volts, as shown in the diagram, and appeared before the next operation. section energizes the plates t3 and £3’ with In order to obtain full wave recti?cation, and 350 volts each. Leads 69, ‘it? connect the trans to increase the sensitivity of the circuit, thereby rapidly actuating the counter mechanism by ap 30 former section 25’ with the cathode ?lament G5, the ?lament t5’ being connected across through plying maximum recti?ed current to the counter leads l2, while the ends of the transformer mechanism, two of the thyratron tubes are em section 32' are connected to the anode plates 43, ployed, and there is sufficient inductance in. the t3’, respectively, by conductors 1-6, it, in which solenoid coil of the counter to maintain the op eration of the tubes continuous during the rela 35 are interposed respectively the resistances 89, 82. tively long time intervals that the photoelectric The lead '50 of the cathode ?lament i5 is con» cell is masked by passage of a sheet or plate be nected through conductor 8% to conductor 50 at tween the light source and photoelectric cell. the potentiometer resistance 53, this wire 85 serv As is shown in Figure 3, the secondary of the ing as the return line for the photocell 2i and also transformer 25 is connected in sections to the 40 completing the electronic circuit through the cathode ?lament of the thyratron tubes. elements of tube Thus, one section 26 is con The transformer section 32' is tapped at the nected to the ?lament Zl through leads 36, 36 middle third as is indicated at 8%. Conductor 38 and 38, the section 32 of the transformer second connects the tap 86 to a variable resistance 93 ary is connected to plates 25 and 30 of the tube 23 through leads 1Z0 and 132, respectively, and 45 which in turn is connected to a solenoid for actu ating the counter ill. Conductor 92 connects the transformer section 28 energizes the source of light ll. solenoid to conductor 812-. It will be apparent from the drawings (Figure It will be seen from Figure 3 that with the 3) that two thyratron tubes are employed in order tube 23 being a “Type 80” radio rectifying tube, to utilize both of the two alternations of the cur the cathode ?lament 27 receives 5 volts from the rent source thereby producing full wave recti? transformer section 2G, and each of the anode cation and increasing the sensitivity of the.sys plates 29 and 30 receives 350 volts from the trans tem and render the system fully responsive to former section 32, this being tapped at its mid the high-speed installations to which the system p-ortion, as is indicated at 44. These speci?ed conditions may be varied, however, depending 55 is applied. There is su?icient inductance in the upon the type of rectifying tube that may be em solenoid coil of the counter to maintain the op eration of the tubes continuous during the rela ployed. Also, the position of the tap 44 may be adjusted, as may be necessary to provide requi tively long time intervals that the photoelectric cell is masked by passage of a sheet or plate be site current conditions in the remainder of the tween the light source and photoelectric cell. The control circuit, as will be pointed out herein thyratron tubes being in parallel, deliver a total after. 7 The tap M is shown as being connected by a current to the counter, which current is the sum of the current outputs of the tubes, thereby pro conductor 5.5 and resistance 3i to the variable ducing extremely rapid actuation of the counter. resistance ‘iii? of a potentiometer S5. The resist ance 138 also is connected through conductor 5%? 65 In Figure 3 the ?laments £5, :35’ are rendered incandescent by alternating current from the to a suitable resistance 33, which in turn is con transformer coil 26’. The‘ two terminals of the nected to transformer section 26 through con transformer 25’ are connected to the two anode ductor 52, which is connected as shown to the plates £3, 133' and the cathodes are connected to lead 36. The resistances, in the illustrated embodiment 70 each other, as shown, and to wire 84 of the ex ternal circuit. Therefore it will be seen that the of the invention, may have a resistance of ‘7590 thyratron tubes pass unampli?ed pulsating recti ohms in resistance 3!, to a total of 10,000 ohms ?ed current to the counter circuit. The recti?ed in resistance 48 and 15,000 ohms in resistance 33. current in the counter circuit exhibits variations Resistances 3i and 33 are ?xed resistances and are employed for protective purposes. These 75 which depend on those of the supply voltage but 2,408,313 5 6 there is no interruption. In order to reduce these tric cell is energized by the ?ash of light passing between the moving plates. variations and obtain a more uniform recti?ed current through the counter solenoid, advantage The photoelectric cell therefore acts as a very rapid circuit maker and breaker, which is re quired because of the high speed of travel of the is taken of the inductance of the solenoid coil which‘assists in such action by smoothing out the pulsations of the recti?ed current, and prevents sheets; and each time the photocell is energized, that instant of energization interrupting the thyratron circuit to make the latter operative stopping of the tubes as the current never reaches the zero point. It is thought to be unnecessary in view of the foregoing explanation to discuss the circuits in detail. One of the characteristics of the thyra tron tubes is that they operate on a difference in voltage between the independent cathode and anode circuits of from 3 to 7 volts, which voltage again to actuate the counter the instant that each of the successive moving plates interrupts the light source; so that the thyratron circuit is closed during the length of time that each sheet passes over the light source, which is relatively long com pared to the length of time that the photocell is 15 active. may be considered negative since the arc in the tubes passes from the plate to the cathode ?la Usually the sheets move on the conveyor at a ment. The voltages of the current supply and speed of about 800 feet per minute with a space of the value of the resistances til, 82, t5, 5:8, 58 and 1/4 inch between the sheets. This means, there 86' must be adjusted so as to give this voltage fore, that each quarter-inch space between the difference between the independent anode and 20 sheets passes over the light source in l/égguogo of a cathode circuits. minute, or 1/5400 second. That means, therefore, Upon the attainment of this condition, the that in 1,6400 second the photocell must energize thyratron tubes operate, and a pulsating direct and enable the grids of the thyratron tubes to current passes continuously through the counting interrupt the thyratron circuit, due to potential device ll. But it is desired not to have a con~ drop across resistance 68a. Then at the expira tinuous current flow through the counter, as the tion of 1/6400 second, the thyratron circuit closes latter will fail to operate under this condition, but and actuates the counter to count one unit, the it is necessary to interrupt this current periodi thyratron circuit remaining closed and the tubes cally responsively to the spaces between the sheets arcing during the time interval that it takes the in order for the counting device H to reset to length of the sheet to pass over the light source. count the sheets accurately. Then as the plate moves out from the light source, The interruption of the tubes is effected by during the next 1/6400 second that the photocell is impressing on the control grids iii, :3 i ', a negative energized, the cycle of operation is repeated. direct current voltage by a value greater than It will be seen in view of the high speeds in the positive 3 to 7 volt difference between the volved that instrumentalities must be employed anode plates and ?laments. which operate instantaneously without lag. The This is accomplished in the following manner. photoelectric cell is free from lag, as are also the The anode plates 29 and 38 produce a pulsating rectifying tube 23 and the thyratron tubes 31 and direct current from the tube 23, some of this cur 39, and the time interval during which the sheets rent being conducted through the potentiometer - pass over the light source and with attendant 35 and conductor 58 to the photocell 2!, the po tentiometer arm 54 being suitably adjusted to the solenoid coil of the counter to be taken up de~energization of the photocell enables lag in supply sufficient voltage for the photocell and also and reset ready for the next counting. supply a voltage to the grids iii, Ill’ of at least 3 It will be seen from the drawings that the con to '7 negative volts greater than whatever voltage 45 ductor a2 is joined to the conductor 8!} at the is between the plate and ?lament of each tube, point 94, at which point there is shown connected when the photocell is operating responsively to a conductor 95, which connects with the conduc light hitting the photocell through the space-s be tor es at the point 88. The conductor 53 is shown tween the traveling sheets. Thus, for example, as being grounded at l?t through condenser Hi2, if the voltage between the plate and ?lament of this condenser being an optional provision, in cer each tube is 150 and the voltage drop across the tain installations it being found to be needed to photocell, for example, is 90 volts, the potenti smooth out the operation of the system. The ometer must be adjusted to take care of the 90 conductor line 91% $8 with its resistor Hi4 serves volts and to impress at least from, say 153 volts to balance the photocell and thyratron tube cir to 157 volts between the grid and cathode ?lament cuits. There is also provided a condenser W5, in each tube. It will be seen, therefore, that under which is connected across the photoelectric cell these conditions, the rectifying circuit would be 2!, this condenser rendering smooth the recti?ed required to supply at least 243 volts through the current from tube 23, which otherwise would be potentiometer 35. This voltage is a positive direct subject to peak variations, current voltage and must be su?icient to, in effect, 60 The values of the respective units indicated on change the voltage differential between the plates the drawings are illustrative only, they being and cathode ?laments 45, G5’ to negative in order determined for each change of the load operated to interrupt the action of the thyratron tubes by the circuit, it being understood that the in and obtain a resetting of the counter mechanism vention is not limited necessarily to the particular during the in?nitesimally short period of inter 65 embodiment herein speci?cally illustrated and ruption of the thyratron tubes, the counter mech described. anism operating to count upon closing the thyra We claim: tron circuit. 1. An electrical control system which comprises, It will be understood, of course, that the poten in combination, a source of light, ?rst and second tial on the thyratron anodes and cathodes is an rectifying instrumentalities for rectifying alter alternating current potential, the action of the tubes being controlled by a direct current poten tial of suitable value andclirection applied to the grids of the thyratron tubes; and this direct cur rent potential is applied only when the photoelec 75 nating current, a load device operated by unam pli?ed recti?ed current from the second rectify ing instrumentalities, and means electrically con necting the ?rst and second rectifying instrumen tilities including light responsive circuit making gnome-1c: and. breaking means; for:- transmitting at; inter-' vals of in?nitesimal duration unampli?ed; recti.fled‘ current;- from1 the. ?rst. rectifying instrumen talities to: the“ second rectifying.instrumentalities,. the. said light-responsive circuit making,‘ and: breakingmeans' being. adapted?o. be completely’ masked;from: the source: of lightv over relatively‘ long. periods of time, but being exposed‘ to; light} from. the light source duringin?'nitesimally. short anode,. a. cathode,~.andv a control grid,, the.- anode: and cathodeof; each‘tube being. connected to-a. suitable source’ of alternating current. and. the. cathodesbeing, connected together, whereby the‘ tubes are. adaptedto deliver an unampli?ed. pul eating. unidirectional. current, a load device» adapted to receive the said-.unampli?ed pulsating; unidirectional current, means includingthesaidv photoelectriccell for connecting the. grid: of; each time intervals . between the. relatively. long periods ' of ' the: said thyratron-type tubes with the said. of masking, the resulting. transmitted’ current. being of: a potentialand polarity'suitable, to pre.L determinately'interrupt action. ofathegsecondlrecs tifying' instrumentalities for actuating the. said. rectifying1circuit,.the- photoelectric ‘cell beingjren- dercdirstantaneously responsive‘ to an in?nitesie mally short: ?ash oflight‘ passing .from the. light. source to‘ the‘ photoelectric cell, the said photo: 151' eleotric cell beingadapted to closeacircuit. from: load device. the. rectifying circuit- through the, grid of each. 2. An electricalcontrol system, which comprises thyratronetype. tube during the: in?nitesimally' the-combination .witha.sourceiof-light, of- a photo; 7 shortmoments of conductivity.- of. the. photoelec-v electric cell. adapted to; be completely‘ maskedi tric; cell and to. open the circuit during relatively from. the source of; light; overv relatively‘ long‘ periods of, time, but; being. exposed to lightiro'm: 202 long intervals duringwhichthe cell is:completely; masked, the said cell during successivemoments; the-light source: duringin?nitesimally short-time. of conductivity transmitting. to; the grids of. the intervals between. the. long. periods‘- of. masking, thyratronetype. tubes a succession. of. momentary: the saidxphotoelectric cellbeingthereby rendered: unampli?ed: unidirectional; currents. control. conductive; by in?nitesimally short light flashes: meansior the:said unidirectional current sothat, resulting from the‘ light. passing." tov the; cell be. current. of. a. potential and. polarity will be im-» tween'the masking periods, ?rstandsecond recti pressed . on .the ; grids suitable 1 to - neutralize. alter. fying instrumentalities for rectifying. alternating: nating; current; potentials: between. the: anode. and. current,.the ?rst rectifying. instrumentalities pro cathode. of eachof the- thyratron-typa tubes. for ducing. a‘ pulsating. unampli?ed unidirectional. current, a; load. operated. by current from the 3 U 1 interrupting actioniof the-tubes, thereby momenr tarlly actuating the load device toconditionthe; second; rectifying. instrumentalities;. the said sec‘ a . ond. rectifying. instrumentalities . including recti-v same. for; further actuation‘ through a; succeeding fying tubemeansincluding an: anode; a cathode, and a.contr.ol grid, the said anode: and cathode relatively long period of: masking. of. the photo electriccell, the load device being:thus;conditioned. each time: amomentary ?ash of light reaches the; beingconnected torsuit‘ablet supplies of alternating current; the: rectifyingitube; meansheing adapted. to; deliver-an unampli?ed pulsating: direct. current‘ to.the said'load, means connecting the ?rst; recti fying.instrumentalities.in: circuitwith: the; control f grid,'.tl1e. connecting means including the: said; photoelectric. cellwhich. is instantaneously: oper able. responsively toxin?nitesimally ‘short; exposure: to light from the; light. source, thephotoelectric: cell being adaptedxto: clcseithe: circuit: through the D. photoelectric cell from thelightsource; can. electrical. control; system, which com prises-the combination Withia source-or light,.of a photoelectric cell‘ adapted to‘ be completely masked. from: the: source. of light.v over relatively. long periodsof. time; but being exposed. to. light. from. the lightsource. during in?nitesimally' short‘, time intervals ' between thee/long‘ periods. of; mask. non-conductive duringzthezrelatively long; periods1 ing, the said‘photoelectric cell being'thereby rem. dered. conductive by;v in?nitesimally short; light: flashes: resulting: from: the light‘. passing, to. the: cell between. the? masking periods. a rectifying: during, which: the cell is. masked-.froini the light; source, therce'll thereby. transmittingtothe con--~ tiiyin'g; tube. having diode; characteristics at: any’ grid during the,in?nitesimally'short exposuresto the; light; and‘ to: open. the: circuit. when; rendered: trol; grid‘ during." successive; in?nitesimally' short‘ circuit . including. av transformer; and a‘. trioide. rec. of. a. potential and’ polarity suitable" to: neutralize; . givenrinstantior obtaining full wave recti?cationg. the. said. circuit; being adapted: to‘ deliver ' an une/ ampli?ed unidirectional . current,. second. rectify alternating current potentials. between the: anode. ing instrumentalities- including a' second triode; periods :ofconductivity'of - thecelli a" direct current; and cathode‘ of. therectiiying tube means" toine' terrupt: action of there'ctifyin'g: tube means for actuating the‘ load device . incident to: restarting the. rectifying‘ tube . means. An electrical controlsystem whichcomprises the combination with a sourceroflight’, ofl'a photoelectric cell‘ adapted to be completely masked from the source of. light‘ during relatively. long rectifying circuit. including . a second‘ transformer. 1: and. a. pair: of i triode- thyratron-type. tubes con. nected to sections‘; of the: said. transformer‘ and.‘ adapted toproduce fulllwave. recti?cation, a load. device operated by'unamplified': recti?ed current from thextliyratron-type'tubes,.the said-rectifying circuit being connected. through the photoelectric: cell .to: a control gridof each of: the triode. thyra'e tron-type; tubes. for‘ impressing: momentary= uni periodsof time while being'exposed to light from directionalcurrentto the saidgrid: of each of the; thelight source during in?nitesimally short-time triode: thyratronetype' tubes for interrupting intervals bctweenthe. long periods of" masking, alternating. current discharge.’ between the“ re: the said photoelectric-cell‘being thereby rend'eredl maihing? elements. of; the’ tubes: respon'sivelyv tov conductive by infinitesimally short light. flashes‘ momentary conductivity of : the». photoelectric: cell resulting from the light passing to the celliduring during in?nitesimally short intervals of'time, the infinitesimally short intervals;betweenithemask photoelectric cell- thereby momentarily closing ing periods, a rectifying circuit adaptedrto deliver‘ an ,unampli?ed pulsating. unidirectional‘ current 70 the rectifying. circuit through. the- saidi control grid in the thyratronetype'tubesi for in?nitesii-i from an alternating current supply; atthyratron» mall'y. short'iperiodsiof time as.light;?ashes toitlie: type'rectiiying circuit comprisinga pair. ofzthyra photoelectric" 0811,; thereby momentarily: rendering. tron-type‘tubes, the. said: tubes;being adapted to. thesaidgcell conductive-rand deenergi'zing. the load utilize both half ‘Waves of: each: alternating: C1113 rent cycle, the: .thyratron-type: tubes. including an; 75. device; responsively to: the in?nitesimally' short‘ 2,408,313 10 interruptions to actuation of the thyratron-type tubes, the said tubes supplying unampli?ed uni directional current to the load device during rel atively long periods of time during which the photoelectric cell is completely masked from the light source, the thyratron-type tubes being con nected in the circuit to be self-starting, the load device being conditioned for further operation during the in?nitesimally short moments of actu ation of the photoelectric cell. 5. Mechanism for counting rapidly moving, closely spaced-apart metal sheet, which comprises a predetermined cycle by unampli?ed unidirec tional current from the thyratron-type tubes, a potentiometer, the said ?rst rectifying circuit being connected through the potentiometer and the photoelectric cell to a control grid of each of the thyratron-type tubes for impressing momen tary unampli?ed unidirectional current to the said grid of each of the triode thyratron~type 10 tubes for interrupting alternating current dis charge between the remaining elements of the tubes responsively to momentary conductivity of the photoelectric cell during in?nitesimally short the combination with a conveyor having the sheets to be counted traveling thereon, of a source of light positioned on one side of the conveyor and adapted to illuminate the sheets and spaces there between, a photoelectric cell mounted relative to intervals of time as light flashes between the sheets being counted to render conductive the photoelectric cell, thereby energizing the load during each ?ash responsively to the in?nitesi the conveyor for receiving in?nitesimally short mally short interruptions to actuation of the ?ashes of light from the light source, the said thyratron-type tubes, the said tubes supplying in?nitesimally short light ?ashes being the light 20 unampli?ed recti?ed current to the counting passing through successive spaces between the means during relatively long periods of time dur rapidly moving sheets, the photoelectric cell being ing which the photoelectric cell is completely completely masked from the light source by pas sage of the sheets, ?rst and second rectifying in masked during passage of the sheets between the light source and the photoelectric cell, the said strumentalities for rectifying alternating current, load performing a resetting operating during the periods of actuation of the thyratron-type tubes, the ?rst and second rectifying instrumentalities being free from mechanical and electrical inertia effects, the ?rst rectifying instrumentalities being and being actuated to perform the said predeter mined cycle during the in?nitesimally short inter ruptions of the thyratron-type tubes as the photo a rectifying circuit including a transformer and a triode rectifying tube having diode character 0 electric cell becomes conductive responsive to istics at any given instant for obtaining full wave light ?ashes between the sheets being counted, the thyratron-type tubes being connected in the recti?cation, the said circuit being adapted to circuit to be self-starting after each interruption deliver an unampli?ed unidirectional current, the and, being in parallel, the said thyratron~type second rectifying instrumentalities including a second triode rectifying circuit including a second 35 tubes deliver a total current to the load which is the sum of the current outputs of the tubes, transformer and a pair of triode thyratron-type thereby producing extremely rapid actuation of tubes connected to sections of the said trans former and adapted to produce full wave recti ?cation, a load adapted to be operated through 40 the counting means. LYLE R. HUNTER. OLIVER C. LEVANDER.