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Aug, 13, 1946. o. R. MILLER 2,405,597 FREQUENCY MEASURINQ SYSTEM Filed NOV. 5, 1942 '7 Sheets-Sheet l m ï w \. .EM /Nl/EA/ TOR O. R. M/l. L ER AWO/#MEV Aug. 13, 1946» o. R. MILLER 2,405,597 FREQUENCY MEASURING SYSTEM Filed Nov. 5, 1942 7 Sheets-Sheet 2 WNNN /Ni/ENTOR 0. R. M/l. L ER ATTORNEY Aug. 13, 1946. 2,405,597 o. R. MILLER FREQUENCY MEASURING SYSTEM Filed NOV. 5, 1942 '7 Sheets-Sheet 3 @Nil No MWA A „v1/5N TOR O. R. M/L L ER A fr0/_mfr Aug. 13, 1946. O. R. MILLER 2,405,597 FREQUENCY MEASURING SYSTEM Filed Nov. 5. 1942 '7 Sheets-Sheet 4 F/G.5 ïlwmlw /NVE/VTOR A TTOR/VEV Aug. 13, 1946. Q_ R, M||_|_ER 2,405,597 FREQUENCY MEASURING SYSTEM Filed NOV. 5, 1942 '7 Sheets-Sheet 5 , @S /Nl/ENTOR BV 0. R. M/L L ER Aug. 13, 1946. o. R. MILLER 2,405,597 FREQUENCY MEASURING SYSTEM Filed Nov. 5, 1942 '7 Sheets-Sheet 6 di. N ATTORNEY Aug. 13, 1946. 2,405,597 O. R. MILLER FREQUENCY MEASURING SYSTEM Filed Nov. 5, 1942 QQl 7 Sheets-Sheet '7 «Si Q „Élu, w. l _ atented ug. 13, 1946 UNITED STATES PArNr 2,405,597 FREQUENCY MEASURING SYSTEM Ohmer R. Miller, Morristown, N. J., assignor to Bell Telephone Laboratories, Incorporated, New York, N. Y., a corporation of New York AApplication November 5, 1942, Serial No. 464,664 4 Claims. l (Cl. 175.-368) This invention relates to measuring systems and particularly to systems for the determina tion of the periodicity of regularly occurring phe nomena such as the frequency of alternating cur rent or the velocity of high speed rotating mech- . anism. i The object of the invention is to provide means for measuring with great accuracy the frequency 2 lating and indicating means so that a direct reading may be had. In order to promote accuracy, the admission of the train of regularly recurring impulses to the first counting chain is delayed for a predeter mined interval. This is especially important where the train of impulses is applied in a man ner where the impulses are at nrst very feeble of an alternating current or the periodicity of a and then gradually rise to full strength. This train of electrical impulses. 1.0 time delay, therefore, allows the impulses to grow to full strength lbefore being applied to the count Another object of the invention is to provide ing chain. Again it is practically impossible for means for measuring with great accuracy the velocity of objects moving through space at a a person to close a circuit accurately at a given high rate of speed. Many such objects such as point in the train of impulses so that this method projectileaaircraft and land vehicles rotate or 15 avoids a first impulse which might otherwise be mutilated. have some moving part which rotates at a rate directly proportional toits forward movement. Again, and for the same purpose, when the Due to the rifiing of the barrel from which a impulses are admitted to the counting chain a predetermined number are allowed to operate the projectile is fired it rotates at a rate depending on its speed. The propeller shaft of an airplane 20 chain Ibut are not counted. In other Words a predetermined number of impulses are absorbed engine and the propeller shaft of a motor car rotate at a rate which is proportional to their before the> actual count is started. This insures speed‘ through space. Any one of these devices that the counting will always be started at the may be fitted with a radio transmitter and a same point in the cycle so that no undetermined directional antenna so that if a radio receiver 25 partial cycles are counted. A feature of the invention is a means for count at an observation point is tuned to receive the ing a predetermined number of cycles of the un wave‘transmitted by such transmitter the result known frequency or a predetermined number of can easily be translated by well-known means impulses of unknown periodicity, means respon into- an alternating current. The object then is to accurately measure the frequency of such 30 sive thereto for generating and transmittinga alternating current. start and a stop pulse at the beginning and end ing of the counting operation and means for In accordance with the present invention the counting the number of cycles of alternating cur alternating current is fed into an impulse gen rent from a precision source between said start erator which will translate such current into a and stop pulses. r train of sharply defined impulses. This train of impulses is then passed through an impulse Another feature of the invention is a method of measuring the frequency of an alternating cur counting device which counts a predetermined number thereof and marks the Ibeginning and rent or the periodicity of a train of regularly re ending of such count by a start pulse and a stop curring impulses which consists of counting a pulse. Thus a period of time is noted which may 40 predetermined number of such alternations or . be measured by comparing it with the output of a precision oscillator. The next step is to operate a so-called “gatef’ such impulses, marking the beginning and the ending of the counting operation and then count ing the number of cycles of alternating current by the start and stop pulses generated by the from a source of known accuracy which occur impulse counting device. This gate will then 45 between the said beginning and ending of the admit to another pulse counting device the out nrst counting operation. The last count will then put of a precision oscillator for the exact period , bear a direct relation to the frequency of the alternating current or the periodicity of the then counted will bear a direct relation to the train of impulses to be measurer. time and thereby give an accurate measure 50 Still another feature of the invention is _la thereof. method of measuring the periodicity of a train of time measured whereby the number of pulses The impulse counting chain for counting the number of cycles of alternating current admitted thereto through the said gate from the precision of regularly recurring electrical impulses which consists of counting a predetermined number thereof and comparing the time taken .to make oscillator may be connected to a suitable trans- 55 such a count with the rate of a current of known 2,405,597 3 4 frequency characterized by steps taken to insure the accuracy of such count consisting of delay ing the application of the unknown periodic cur rent to the counting means for la predetermined time after the beginning of the operation and then absorbing without counting a predetermined ' number- of such impulses after theY unknown periodic current is applied to the counting means. ` Other features willappear hereinafter. The drawings consist of seven sheets having eleven figures, as follows: , _ Fig. 1 is a schematic circuit diagram showing the relation of the various circuit units to ex plain the general method of operation; ' Fig. 2 is a block diagram showing how Figures 3 to 7, inclusive may be placed to make a com plete detailed circuit diagram; Fig. 3 vis a circuit diagram of the impulse gen erator; , for instance, Just as the wave passes through zero from the positive half wave to the negative half wave. ' The train of impulses now flowing into the impulse counter 'I starts this device-into opera tion with the result that two pulses are produced thereby, one constituting a start pulse at the be ginning oi' a count and the other constituting a stop pulse at the end of an operation during which a‘ predetermined number of pulses are counted. Thus an interval of time A is meas ured between the start and stop impulses which is the time taken for a given number of rotations of the projectile or a given number of cycles oi' 15 the alternating current from the source 4. As will appear hereinafter. and for certain rea sons having to do with the question of extreme accuracy, several pulses incoming to the impulse counter 'I at the beginning of the operation are . Fig. V4.- is a circuit diagram of the time-delay 20 absorbed and not counted. The start and stop pulses produced by the lm pulse counter 'I are employed to operate the gate Fig. 5 is a circuit diagram of a pulse counter circuit 8. This is a device effectively interposed for'producing the start and stop pulses for oper between a precision oscillator 9 and a recording ating the gate circuit; ' Fig. 6 is a circuit diagram of the gate circuit; 25 circuit I0. The recording circuit I0 will accu rately ycount the cycles of alternating current Fig. '7 is a diagram of the pulse counting and flowing through the gate circuit 8 during the in recording means, showing one unit thereof in' circuit; . » l terval A, the gate being opened by the said start full and indicating duplicate units schematically; impulse and being closed by the said stop im Fig. 8 is a nest of graphs useful in explaining the operation of the time-delay circuit off-Fig. 4; 30 pulse.- Since the precision osillator Il may pro duce a current of precisely regulated frequency and of-a comparatively high frequency the in terval of time A may` be measured with extreme Fig. 10 is a characteristic curve of the gas tube accuracy. In general, the recording circuit I0 is which produces the impulses in the impulse gen 35 of the same nature as the impulse counter 1, as erator of Fig. 3'; and ' Fig. 1l is a nest of graphs useful in explaining will be more fully set forth hereinafter. The impulse counting circuit I0 operates an the operation of the gate circuit of Fig. 6. indicating circuit II which serves to giv/ë some In Fig. 1 the invention is illustrated schemat kind of an indication revealing the number of im ically. `The Working starts where _an alternating current is fed into the impulse generator I. As 40 pulses counted during the' time A while the gate 8 was open. llin accordance with one embodi shown, this alternating current may be derived ment of the invention this indicator consists of from a projectile equipped with a radio trans means to display a number such as 37,777. The mitter having a directional antenna in the fuse frequency of the source r9 being known, the numP portion thereof. The radiations of such a trans mitter are picked up by the radio receiver 2 in 45 ber 37,777 is then a direct measure of the time interval A and therefore in direct proportion to the form of oscillations periodically varying in the velocity of the projectile or to the frequency amplitude as illustrated by the graph below the radio receiver 2. The variations in amplitude of the source 4. Considering now the detailed circuit drawings, are caused by the rotation of the projectile in several general lobservations may be made. flight due to the rifling of known pitch of the Throughout the drawings wherever ionic tubes barrel from which it has been discharged. The are shown the filaments for heating such tubes frequency of such variations in amplitude bear a are indicated but' the battery supply is not shown direct relation to the velocity of such projectile since the manner of making such connections is in -flight. The output of the radio receiver 2 is passed through a low frequency detector 3 and 55 well known and the addition of such circuits would unnecessarily complicate the‘ drawings. In produces therein an alternating current all in various figures there are shown reset keys whose accordance with well-known means and methods. Or the alternating current which is fed into _ function it is to return the various circuits to their normal conditions. It will be understood the impulse generator I may be derived from any other source, such, for instance, as the source 80 thatthese may be in the form of separate keys as shown and described or they may all be in of alternating current 4 ,and applied to the im Fig. 9 is a nest of graphs useful in explaining vthe operation of the impulse generator of Fig. 3; t corporated in a single device so that at one stroke pulse generator by any means such as the key 5. ,Now upon the application of an alternating the various circuits may be properly controlled. current to the -impulse generator I, a time delay ' As explained hereinbefore, an alternating cur circuit 6 starts into operation and delays for a 65 rent is fed into the impulse generator from one given interval oi’ time the application of the out or another source such asthe radio receiver 2 put of the impulse generator to the impulse count and low frequency detector 3 or the source 4 er 'I. This is to insure .that the first impulses to through some connecting agency such as the key -be counted are of full strength. v 5. In the impulse generator the alternating cur The impulse generator I is a device which pro 70 rent flows in over conductor I2, through con duces a single sharply deñned impulse from each denser I3 and thence through the primary wind cycle of alternating current fed thereinto. Through novel means provided this single sharply y ing of a transformer I 4 to ground, it being as sumed that a. ground connection is provided at defined pulse may be made to occur at any par ticular point in the cycle over a given range as 75 the said source of current. The secondary wind- l Il 2,405,597 5 6 ing of transformer It thus becomes a source oi’ 42 and 43 as indicated by the graph t5 from a comparatively high positive potential to a com alternating current to affect the triode it. paratively low positive potential. .At the same The cathode grid circuit of this tube may be traced from the cathode through the resistance time the potential on the grid of tube d6 falls, i6, the secondary winding of the transformer IB, 5 as indicated by graph M, from a positive value resistance il to the grid of tube l5. A condenser . to a negative value below the cut-ofi bias (in IB is in parallel with both the resistance i5 and dicated by the dotted line d8) oi the triode t6 a source of negative biasing battery comprising so that this tube now becomes non-conducting. This changes the potential of the potentiometer the resistance i9 and the well-known network of point between the resistances HB and 50, as indi~ rectiilers 2li, 2|, 22 and 23, energized by a source cated by graph 52, from a comparatively low pos of alternating current 2i and an interposed trans itive value to a comparatively high positive value. former 25. The potential supplied by this net Thereupon the potentiometer point‘between re work controls the anode-cathode current ilow in sistances Ell and Si rises, as indicated by graph the tube l5 between the battery connected to the 53, from a negative value through the trigger anode thereoiand the resistances 2b and 2li to potential of gas tube M (indicated bythe dotted ground. Under these conditions a given potential line 55)"to a positive value. 'Thereupon the con " thus stands on the cathode'i'o'i‘tube iii, this being ' denser Iêi‘l begins to charge through resistance 56 a point on the potentiometer consisting of the .in accordance with graph 5l, and when the trig internal resistance of the tube and the two re 20 ger potential E5 of the tube tél is reached the con ' sistances 2d and El. trol conductor 29 is effected, as follows. When Now as an alternating current wavein the -tube 5t becomes conducting the potentiometer secondary winding of transformer iii rises from point between the resistances £53 and 59 changes a zero value to an increasing positive potential its potential, as indicated by graph 6l, from a the grid oi the tube becomes less negative and comparatively high positive value to a compara as a consequence the anode-cathode current in tively low positive value. Thereupon the poten creases. Therefore, the potential oi’ the cathode tiometer point between reslstances 5d and Si) with respect to ground increases, so that the po drops, according to graph 62, from a positive tential on the start conductor iii increases. This value through the cut-off bias grid potential of start conductor leads into the time-delay circuit so that when the increase of potential thereon is 30 tube 63 (indicated by the dotted line fili) to a negative value and tube lit becomes non-conductgreat enough the time~delay circuit will be tripped ing. This in turn changes the potential on the off and in a given time will raise the potential on potentiometer point'between resistances and the control lead @il snmciently to allow the gas iid, as indicated by graph @8, from a comparatively tube il@ to function. , low positive value to a comparatively high posi Normally the cathode oi the tube id is connect tive value. This last potential change is com» ed in av circuit with the right-hand pair oi ele municated over control conductor 29 'to enable` ments of.’ the double diode tube iii, resistance t2, condenser resistance 2i to ground, whereby the condenser may be charged as the potenn tial of the cathode ci' tube iii'rlses. Normally also the potential standing on the control con ' ductor and communicated through the leit hand pair of elements~ of the double diode iii di rectly to the condenser 3s prevents the ai'oremen tioned charging circuit from becoming effective. In other words, the control conductor normally the impulse generator. The tubes of Fig. Li will now remain in the -condition just described _regardless of the varia tion in potential on the start conductor 2li until the reset keys t9 and 'lil are operated to render tubes ¿il and 5t again non-conducting. A pair of cold gas signal tubes l'vi and l2 are provided for visually indicating the operation of this time-delay circuit. Tube 'il whose control anode (indicated by the arrowhead) is normally at a comparatively high positive potential is there that the impulse generator cannot function. fore normally glowing. When this potential is If the alternating current fed into the input conductor i2 is derived from the, radio receiver 2 50 dropped in accordance with graph ¿i5 this tube becomes dark as an indication that the timing the signals may at first be weak but as they grow operation has started. Tube ‘i2 whose control in strength a point Will be reached where the anode is normally at a comparatively low positive rise of potential on the cathode of tube i5 and potential is normally dark. When this potential on start conductor 28 is suiiicient to trip off the is raised in accordance with graph 60 to a com time-delay circuit. Thereafter, and after a pre holds the voltage on the condenser 33 down so paratively high positive potential this tube 'l2 determined time the potential on the control con glows. The period of time during which both sig ductor 29 will be raised to enable the impulse gen nals are simultaneously dark is a measure of the erator to operate as will be described hereinafter. The operation of the time-delay circuit of Fig. desired time interval. This may be adjusted as d will be explained with the help of a nest of 60 desired by changing the value of the resistance 56 and the capacity of the condenser M1. graphs shown in Fig. 8. Two vertical lines are In this manner, then, the signals being fed shown, one marked "start" and the other marked into the impulse generator over conductor i2 grow “controL” The distance between these lines is a in strength, and the impulse generator is en measure of the time interval desired. 'I'he start conductor 28 is connected through 65 abled a predetermined time after such signals have reached a strength suñicient to trigger .off a resistance 3i to an intermediate point on a the tube 4I. potentiometer comprising resistances 35, 3G and With the rise of potential on control conductor 31 connected between positive battery 38 and neg ative battery 39. As' the potential on the con 29 the impulse generator will function. This will ductor 28 rises according to the graph fillv it 70 be explained with the help of Figures 9 and 10. reaches a point where the gas tube M triggers Tube 30 is a gas tube, one of whose character on` and this is the start of the operation. Tube istics is depicted in Fig. 10. For each given posi 4H becomes conducting and the anode-cathode tive potential value on the anode thereof there current iiow therethrough changes the potential is a corresponding given negative value on the at the potentiometer point between resistances 75 cathode at which the tube will fire or trigger off. ` 2,405,597 This is shown by the curve113 plotted between positive anode potentials and negative cathode po primary of the transformer 18 produces a single sharply defined pulse shown bygraph 19, which tentials. may be inverted by the transformer 18 to a nega In accordance with this inventionv a positive anode potential is nrst established and tive pulse. This is transmitted over the signal thereafter the negative potential is increased (in ing conductor to the impulse counter of Fig. 5. a positive direction) until the corresponding point Thus alternating current incoming over con is reached, whereupon the tube fires. ductor I2 is transformed into a train of sharply In Fig. 9 the'graph 14 represents a cycle of deñned unidirectional pulses, one for each com alternating current as delivered by the secondary plete cycle of alternating current. These pulses of transformer I4. As the positive half wave 10 are then applied to the output circuit of the im rises in value, the negative potential on the pulse generator which is connected to the in grid ofÍ tube I5 recedes until the tube becomes put circuit of the impulse counter. saturated and hence the change of potential on >The pulses coming in over the input conductor the cathode thereof rises to a particular value and pass through condenser 80 and appear as sharply then halts as indicated by the graph 15. This is 15 denned negative pulses leading to the suppressor a measure of the potential being applied through grids of two tubes 8| and 82. the right-hand elements of the double diode 3| to The tubes 8| and 82 form a counting pair, one the condenser 33. Thus the charge on condenser . of which is always energized and in a conduct ing state. The principle of operation is funda 33 rises, in accordance with graph 18, during the rising part of the positive half wave of alternat 20 mentally the same as that of the well-known ing current potential v14. However, due to the Eccles and Jordan circuit, disclosed in British unidirectional characteristics of the diode 3|- the Patent 148,582. These tubes are, however, pen positive chargeC attained on the condenser 33 todes with the anode of each connected to the is maintained as the falling part of the positive screen grid of the other. When the negative half wave is reached. But at this time the cath 25 impulse is applied to the suppressor grid of both, then both are rendered non-conducting. When ode potential of tube 38 measured at the poten tiometer point between resistances 28 and 21 be gins to fall, in accordance with graph 11, until the negative value B is reached. Since the posi the said negative impulse has ceased the com bination of the two tubes is left in an extremely unstable state- so that the slightest influence will tive potential C of condenser 33 is now placed 30 determine which of the two is to become conduct through the primary winding of transformer 18 ing to the exclusion of the other. This extremely on to the anode of tube 30, this tube will ilre and - slight innuence is supplied by a condenser 83 the condenser 33 will discharge through the connected between the cathodes of the two tubes anode-cathode circuit of tube 38 and the pri which is charged in one direction while tube 6i mary of transformer 18. ’ ' A35 is active and in the other direction while tube In. the above description the negative value B 82 is active. When the negativev impulse is ap of the cathode of tube 30 is described. Actually plied to the two suppressor grids, ,condenser 83 the cathode of tube 38 is never at a value'negative becomes discharged but there is left a slight resid with respect to ground but if the actual potential ual charge, the magnitude of which depends on of this cathode at the static condition of the cir 40 the effective length of the said negative pulse. cuit when the incoming alternating current Wave At the- termination of this negative pulse the is at zero is taken as a reference point, then the said slight residual charge on condenser 83 ~is cathode of tube 30 moves in a negative direction suilicient to determine which of the two tubes so that when the potential of the cathode of this 'will then become active. If tube 8| has been ac tube is spoken of as becoming negative it will be 4. tive before the negative pulse, then tube 82 will understood that it is increasing in a negative become active thereafter. Thus one negative pulse sense. Thus as the current in resistance 21 de ‘ will render tube 8| inactive and tube 82 active creases the potential of the cathode» of tube 38 and a second pulse will reverse this condition increases in a negative sense. and render tube 82 inactive and tube 8| active. Thus the difference of ` potential between the Throughout the circuits to be described a large terminals of condenser 33 increases both dur number of these counting pairs are employed all ing the rising value of the incoming half wave of which operate in the same manner. 'I'he de of alternating current and the following decreas tailed description of. the operation of a single pair ing value of this half wave until the tube 3|) is will therefore be suilicient. It will be found that triggered ofi'. .- ' s This action will continue as long as the po tential of conductor 29 is maintained at a com paratively high value by the tube 63 whereby the upper tube of each pair is normally active; that is, it is in a conducting state and has a low potential on its anode. Conversely the lower tube of the pair is normally inactive; that is, it is in a non-conducting state and has a high po the charge on condenserV 33I is prevented from being dissipated over the path including con (if) tential on its anode. . ductor 29 and tube 63, as it is during the inac It will be noted that the anode of each tube tive periods of the impulse generator of Fig. 3. It is to be noted that the value of the negative bias of tube |5 may be regulated so that the value of the positive potential attained on the anode of tube 38 may be adjusted >as desired. This may particularly be adjusted so that this positive potential attained or established on con denser 33 may just match the negative potential ` attained on the cathode of tube 30 as the alter nating current wave 14 passes through zero from the positive half wave to the negative half wave. 'I‘hus the discharge of the condenser 33 may be made to occur at any desired point. - is in a potentiometer circuit. For tube 8| this potentiometer circuit may be traced from a high positive battery through resistance |58 and re sistance |5| to ground. The anode of the tube 8| is connected to the potentiometer point be tween resistances |50 and I5I. Also a circuit constituting a potentiometer may be traced from resistance |58, the anode cathode path within the tube, resistance |52 and resistance |53 to ground. The resistances of the tube |52 and |53 are thus in parallel with resistance |5I. Now when the tube is non-conducting or inactive there being little if any current flow in this potentiometer The discharge of condenser 33 through the 75 circuit, the potential of the anode (and the screen e 2,405,597 9 l0 grid of the companion tube) is at a comparatively with such pulse being passed on to the following high positive value. Thus the tube 82 is enabled by a comparatively high positive screen grid po However, when a negative potential is ' tential. applied to both suppressor grids both tubes be pair or stage. v Thus in the impulse counter`- of Fig. 5 eight stages of these counting pairs of tubes are pro vided. 'I'he first pulse renders tube 8i inactive; the second pulse renders tube 85 inactive and come non-conducting and hence a comparatively high positive potential is applied to the screen grid-of each. Hence, when the negative poten tial is removed from the suppressor grids both tube 86 active. As tube 86 passes from the in active to the active stage a negative pulse is gen erated and passed over conductor 81 where it tubes are in a condition to become active or con 10 functions as a `start signal to the gate circuit of Fig. 6. The two hundred and fifty-sixth pulse ducting.. The choice of which one prevails 'rests returns all the upper inactive tubes to normal with the condenser 83 as hereinbefore pointed and generates a negative pulse which now passes out. . When tube 8| is in an active or conducting over conductor 88 where it functions as a stop state theY current flow in its anode-cathode cir 15 signal to the gate circuit. Thus the difference cuit aii’ects the potentiometer point between the between two hundred and fifty-six and two or resistances i5ß and i5! so that the potential two hundred and nity-four pulses is counted, the thereof is at a. comparatively low positive value. first two being effectively absorbed. The gate circuit thus opens a circuit for the flow of alter~ Hence the screen grid of the companion tube is at a comparatively low positive value and this tube 20 nating current from a precision oscillator for the length of time of two hundred and iiIty-four isD held in a non-conduction or inactive state. pulse cycles from the- impulse generator. The The potentiometer circuit for tube 8| has been impulse counter may be arranged to count any described. Tube 82 has a similar potentiometer other number which would be more suitable un circuit consisting of the resistances I5ë, |55, IE6 25 der the circumstances under which this appa and l53. It should be noted that as a tube goes from a ratus may be used. non-conducting to a conducting state its poten tiometer point suddenly drops from a compara tively high t0 a comparatively low positive value. Hence as tube 8| becomes active the potentiome , , The purpose of absorbing one or more pulses at the beginning oi’ the. train is to insure the measurement of a definite time interval and avoid 30 error which might come from a false start if the first impulse transmitted from the impulse gen erator were not of full strength. and condenser 84 translates this sudden drop in potential into a negative impulse to be applied The reset key H48, when operated. will return to the suppressor grids of tubes B5 and 8E. the impulse counter to normal by rendering all Thus the pair of tubes iii and d2 provide a 35 the lower tubes of the various stages inactive. means which sets up a- stable condition which will The action of the gate circuit, Fig. 6, will be remain fixed, but which instantly responds to a explained with the help of a set of graphs, Fig. ll. ter point between resistances |50 and iii drops negative incoming pulse to reverse the previous Here a number of tubes are employed some of condition of the two tubes. Also the tubes in which are paired as in the pulse counter. For in their reversal will generate a like negative pulse 40 stance, tubes 90 and Si form one pair and tubes 92 when the reversal in condition is in a given direc and 93 form another pair. Tubes 90 and 92 are tion so that for every two incoming negative normally active and tubes 9|, 93 and Si are nor pulses asingle outgoing negative pulse is gen mally inactive. The connections of the tubes are erated. much as before except that the condenser between The impulse counter consists of a plurality of 45 the cathodes'of the tubes of a pair is not employed pairs arranged to count the impulses according so that a negative pulse coming in over the start to a binary geometric progression system. Thus, conductor Bl and passing through the condenser the first pulse renders tube d2 active. The sec- . ’ 8s will reverse the condition of the tubes 90 and ond pulse rendering tube di again active will also ill, rendering tube 90 inactive and the tube 9| generate a negative pulse through condenser 8d 50 active. A potentiometer is formed between the to the pair of tubes 35 and du and will result in positive battery 95, resistance 9E and resistance rendering tubes 82 and 85 inactive and tubes 8i Sl to ground, and the anode of tube 90 and the and 86 active. The third pulse will render tube grid of tube 9i are _connected to this potentiom di inactive and tube’tZ active. eter at a point between resistances 96 and 97. It may be noted that if each of the lower tubes 55 Due to the current now while tube 9U is active the oi all pairs is given a value of zero and each of potential of this point is held at a comparatively the upper tubes is given a value according to a low positive value. When the negative start pulse geometric progression as l, 2, LS., 8., i6, 32, 64, 128, comes in over conductor 81 to the suppressor grid 256, etc.,.the sum of the values of the inactive of tube 9i! this tube becomes non-conducting with tubes will be a count of the number of pulses. 60 the consequence that the potential of the anode Thus, at the beginning all the inactive tubes will in the said potentiometer circuit rises to a com have a value of zero and the‘sum of such values will be zero. After the first pulse, tube iii will be inactive and the sum now becomes l. After the second pulse tube t5 is inactive and tube iii is paratively high positive value, as indicated by graph 9B (Fig. 11) . Since this comparatively high positive potential also appears on the grid of tube 9 i, this latter tube now becomes conducting. Here again a potentiometer is formed of positive active so that the sum becomes 2. After the third pulse tubes di and t5 are inactive so that battery 95, resistance lSi! and resistance itl!) to the sum becomes l+2=3. With two pairs oi ground, The potential on the potentiometer tubes three pulses may be counted as the next point between resistances 99 and itil! is normally or fourth pulse will return both pairs of tubes to 70 a comparatively high positive potential but as normal while passing such fourth pulse on the tube 9i becomes conducting this drops to a com next pair of tubes to be counted there. With eight stages two hundred and fifty-’five pulses may be counted, all pairs being returned to nor-v mal on the two hundred and nity-sixth pulse 75 paratively low positive potential as indicated by graph i t i, This being communicated to the grid of tube S0 holds this tube non-conducting after the termination of the negative start pulse. ' 2,405,597 . 11 12 . As the potential of the anode of tube 9| drops, the condenser |02 responds by discharging be -tween resistances |03 and |00, forming a negative pulse, graph |04, applied to the suppressor grid of Y 'I'he inter ` y pulse is received whereupon it glows. val during which both tubes are dark is there fore _a measure of the time interval between the start and stop pulses. ` ` tube 92. Tube 92, normally conducting’now be.. The control electrode of tube |25, indicated by comes non-conducting with the result that the the arrowhead, is connected to a potentiometer potentiometer point between resistances |05 and |01 rises from a comparatively low positive value to a comparatively high positive value, as indi' cated by graph |08. This causes tube 93~to be point leading through resistance |21 to ground. The potential of this point is controlled by tube come conducting so that the potential on the po tentiometer point between resistances |09 and | |0 now drops from a comparatively high positive value to a comparatively low positive value, as in 9| over resistance |28 and by tube 93 over resist ance |29. When either of these tubes is active the tube |25 is held inactive but when both these tubes 9| and 93 are inactive, as under normal conditions, then the „potential of the point be dicated by graph |||. This drop of potential communicated to the grid of tube 92 holds this tween resistances 99 and |00 and the potential of the point between resistancesr|09 and l l0 is at a comparatively high positive value and tube |25 tube non-conducting after the termination of the a's a consequence, glows. . negative impulse from condenser |02.' Likewise, tube |29 is under control of tubes Another potentiometer is formed between posi 90 and 93 so that only .after the gate circuit has tive battery 95, resistances |06, ||2 and`||3 to 20 completely functioned and tubes 90 and 93 are negative battery lill.Y The potential of the point . simultaneously inactive is tube |26 conditioned to between resistances ||2 and | I3 in general follows glow. Thus tube |25 glowing indicates that the the potential of the point between resistances |06 ` gate circuit has not yet functioned and tube |28 and |01, as indicated by graph H5, and hence as glowing indicates that the gate circuit has com this point rises in potential the tube 94 is ren v25 pletely functioned. dered active so that pulses from the precision os cillator connected to input lead | I6 may be passed through the tube 94 to the output lead ||1 as a The train of negative pulses transmitted over` conductor ||1 feed into a chain of pulse counters " in Fig. '1 represented by the recorder circuit |0 of Fig. 1 similar to those shownsin Fig. 5. In | I8. ~ 30 yorder to count a number of ypulses of the order of The output of the precision oscillator is practi 16,000 it would be necessary to provide about iii-_ cally a sine wave. It is, however, connected teen pairs of tubes. As pointed out hereinbefore, ` through a condenser ||9 and a resistance |20 to with fourteen pairs'of tubes and after a counting a potentiometer ypoint between resistance |2| operation in which the upper or normally con leading to positive battery and resistance |22 ducting tube of each pair has been rendered non leading to negative battery. whereby the tube 94 conducting a number 1l, 111, 111, 111, 111 in ac is biased to cut-off so that only the peaks of the cordance with the simple binary geometric positive half waves affect the tube tol produce at progression scheme of counting -would be re its anode and on conductor | l1 a series of negative corded. This number, translated into the com pulses. Before thev start pulse has rendered the 40 monly used decimal system would mean that a tube „non-conducting the screen grid of tube 94 train of 16,383 pulses had been counted. How is held down to> a comparatively low positive po ever, since the first of these numbers is awkward tential (graph ||5) so that the `tube 94 is blocked. to handle the arrangement shown in Fig. '1 may When, upon the occurrence of the start pulse, the be employed. Here, a set of fifteen pairs of tubes potential ofthis screen grid rises to a compara 45 is employed, arranged in five sets of three pairs tively high positive potential this tube becomes each. Each such set of tubesr represents the train of negative pulses, as indicated by the graph unblocked and the'distorted wave from the pre- g means for recording a single “digit” in a system , cision oscillator passes to the output | |1 as a train using the digits 0 to 7, inclusive, so that 16,383 of negative pulses. `The conditions thus far de pulses counted would be recorded as the number scribed hold until the stop pulse is received over 50 37,777. As hereinbefore pointed out, if the three lower conductor 88. ' ' When the stopvpulse is transmitted over con tubes |38, |39 and |40 are given the value zero ductor 88 it passes through condenser |23 and each and the three upper tubes |4|, |42 and |43 appears as a negative pulse on the suppressor grid are given the value 1, 2 and 4, respectively, then of tube 93, whereupon the condition of the two 55 the “digit" recorded on this unit will be equal tubes 92 and 93 will become reversed, 92 becom to thefsum of the value_s of the three tubes which ing conductingl and 93 becoming non-conducting. are simultaneously inactive. A group of eight It will be seenA from graphs |08, |||, ||5 and ||8 glow tubes |30 to |31, inclusive represented by the that the _flow of negative pulses over the output indicator circuit ||- of Fig. 1, is used to indicate circuit | |1 is thus'abruptly terminated. "60 the number recorded on this unit having the The circuit will remain in the present condition, values 0 to '7. inclusive, respectively. Thus, if the with tubes'9l and 92 active and tubes 90, 93 and three lower tubes |33, |39 and |40 are all inactive, 94 inactive until the circuit is returned to normal as in normal condition, the glow tube |30 will be ' condition by the operation of the reset key |24, active and by glowing will indicate the “digit” which, by temporarily placing negative potential 65 zero. If, on the other hand, all three upper tubes on the control grids of tubes 9| and 93 insures |4|, |42 and |43 are inactive, then glow tube |31 by glowing will indicate that the “digit” 7 ` that tubes 90 and 92 become active and tubes 9|, 93 andY 94 become inactive. (equal to the sum of 1+2+4) has been recorded. As in the case of the time-delay circuit de It will be noted that each glow tube. such as scribed hereinbefore, this circuit unit is provided 70 the tube |30, is connected to a network having a with a pair of glow tubes to indicate the condition resistance leading to one tube of each pair. Thus of the apparatus. Tube |25 is normally active, resistance |44 is connected to the anode 0f tube and becomes dark as soon as the start pulse is d |38, resistance |45 is connected to the anode oftube |39 and resistance |46 is connected to the received andv remains dark thereafter. Tube |26 is normally dark and remains dark until the stop 75 anode of tube` |40. It is only when these three r ‘ 2,405, 597 14 13 Fig. 5--direct current for anode potentiometers. tubes |38, |38 and IW are simultaneously inactive that the potential of the control electrode of 810W +255 volts “ ît‘ig. â-direct current for reset key |48, -150 tube |30 is sufficiently high to render the tube |30 active. From the above it will readily be seen vo s ` Fig. 6-95. +255 volts that these tubes are connected in a network based 5 Fig. G-direct current for indicating lamps |25 on a permutation code whereby only one of the and E26, -130 volts glow tubes |30 to |31 is rendered active at any one time. Fig. G-direct current for reset key |26, _150 « volts The arrangement of the six tubes §38 to |43, Fig. S-I M, -150 volts inclusive, may be considered a recording and in- 10 Fig. 7-direct current for anode potentiometers, dicating means for the last “digit” in a system +255 volts based on the use of digits 0 to 7, inclusive. Other` Fig. 'Z-direct current for reset key, -150 volts Fig. 7-direct current for upper cathode of in digital recorders are indicated by the broken line rectangles to the right. All of the various pairs of tubes are arranged serially so that if the upper 15 dicating lamps, -150 volts Fig. T-direct current for lower cathode of in tube of each pair were given a value according to dicating lamps, +140 volts the simple binary geometric progression l, 2, 4, 8, 16, 32, 64, 128, 256, 512, 1,024, 2,048, 4,096, Fig. 'l-alternating current for lower cathode of indicating lamps, 11G-volt E50-cycle alternating 8,192, 16,384 and the upper tubes oi’ the first four teen pairs were active, then the sum of such 20 current values would be the sum of the first fourteen » members of the above progression, of 16,383. Appendix By way of example, the following lists of values 25 and types of resistanees, capacities, voltages and tubes are given. It should be noted that other values may be used and it is quite possible that further experiment might prove that improve ment in operation could be secured through de- 30 viation from the values and types given: Resistors llt-5,0000» ll--5,000w 2â--9,000a 2l---5,000w :i2-5,0000, @ll-ln u9-125ß00w l10n-lil ills-.1n ißt-125,000@ iii-.25u Mil-_1n 35-.50 .fit-0400,00@ lil-150,000@ M-lOuOOOw illu-425,000@ i lll-_liz i |2--.5Q i i3-2n Alt-_.551 itil-»50,00% ¿lt-.50 ca_-30,000@ til-150,000@ tät-100,00@ i 22-50,000w lil-»5u t i-looßûûw tt-o-io 528-59 irs-5o 35 What is claimed is: l. Means for measuring the periodicity of a train of regularly recurring electrical impulses comprising a delay means for preventing the ad mission of impulses to they rollowing measuring w means for a predetermined time after the be~ ' ginning of the operation, a means for counting a predetermined number of said impulses, said means generating and transmitting a start im pulse marking the beginning and a stop impulse 45 marking the ending of said counting operation, a source of impulses of known and accurate pc riodicityJ a means for counting impulses from said source and means operated by said start and stop impulses for admitting impulses from said ac 50 curate source to said last counting means. 2. Means for measuring the periodicity of a 5t--l(iil,li0uw i5u-l25,000w til-_.59 tti-«5u itl-1Q @a2-_820e train oi' regularly recurring electrical impulses tt-«öubiluw itt-1,50% mission of impulses to the following measuring tt-.Zeil til-.til itt-125,00@ itt-_la tt-l25ßtlia itt-820e Condense'rs comprising a delay means for preventing the ad 55 means for a predetermined time after the be ginning of the operation, a means for counting a predetermined number of said impulses, said means generating and transmitting a start im pulse marking the beginning and a stop impulse marking the ending of said counting operation, a@ said means also being responsive to impulses ad mitted thereto by said delay means for absorb Condenser associated with grid of tube fil, ing a predetermined number of said impulses be E13-«l mi. ia-so 35i-.002 mf. 2G mi’. 5.5-.5 mi’. tt--öll mm1’. tél-«.03 mi”. tid-«50 mini’. @Q_-50 mmf. HB2-_125 mmf. i lt-.l mi. voltages fore transmitting said start impulse, a source of @E impulses of known and accurate periodicity, a means for counting impulses from said source and means operated by said start and stop im~paises for admitting impulses from said accurate source to said last counting means. 3. Means for measuring the frequency of an tél-llo volts Sli-cycle alternating current m alternating current, comprising an impulse gen erator for translating said alternating current in Alternating current source to indicating lamps to a train of impulses of like periodicity, a delay li and l2, lill volts, Sli-cycle alternating current means for preventing the admission of impulses ¿t9-_+ 150 volts 75 to the following measuring means for a predeter 2,405, 597 _ mined time after the beginning o: the operation, a, means for counting a predetermined number of said impulses, said means generating and trans ' 'is , the admission of said alternating current to means for counting the cycles thereof for a predeter mined time, absorbing without counting a pre mitting a start impulse marking the beginning determined number of said cycles after admis- ' and-a stop impulse marking the ending of said 5 sion to said counting means, thereafter count counting operation, a source of impulses oixknown ing a predetermined number of cycles of said al and accurate periodicity, a means for counting impulses from said source and means operated by said start and stop impulses for admitting im ternating' current, marking the beginning and the ending of the said counting operation and simultaneously counting the number of cycles of pulses from said accurate source to said last count 10 alternating current from a known source of great ing means. accuracy which ‘occur between the said begin 4. The method of measuring the frequency or » an alternating current which consists of delaying ning and ending of said ñrst counting operatiom OHMER R. MILLER.