US2796521A - Electronic circuit - Google Patents

Description

June 18, 1957 Filed April 27, 1954 Number Va d wmber in Space J. J. LENTZ 2,796,521

ELECTRONIC CIRCUIT 2 Sheets-Sheet 2 FIG. 2

INVENTOR JOHN J. LE/VTZ ATTORNEY United States Patent Business Machines Corporation, New York, N. Y., a corporation of New York Application April 27, 1954, Serial No. 425,993

6 Claims. (Cl. 250-27) The invention relates to a novel storage device and more particularly to an electronic regeneration device that will remember indefinitely.

The principle object of the present invention is to provide an improved storage device that is relatively compact, inexpensive to construct and highly stable in operation.

Another object of the present invention is to provide a storage device that will accept data for storage at any instant in time and have said stored data available at subsequent periodic intervals of time.

An additional object of the present invention is to provide a storage device, which upon receipt of data to be stored, will inherently reset or discard any data stored in said device and accept and store the presently submitted data.

A still further object of the present invention is to provide a storage unit capable of accepting data expressed in widely varying wave forms and furnishing said data at a subsequent period in time in a more readily usable wave form.

Yet another object of the present invention is the provision of a storage device finding application as a delay circuit or a combination delay circuit storage device.

A still further object of the present invention is the provision of storage device that will directly and simply store decimal values.

A yet further object of the present invention is a delay circuit wherein the delay time is substantially independent of tube characteristics. That is the mathematical expression for the time delay of the delay circuit is a function only of the second and higher orders of the tube constants.

Other objects of the invention will be pointed out in the following description and claims and illustrated in the accompanying drawings, which disclose, by way of example, the principle of the invention and the best mode, which has been contemplated, of applying that principle.

The novel storage device herein disclosed is for use in storing for an indefinite period a number or data represented as a voltage impulse occurring at a preselected time relative to a standard time base interval. In so representing a number, a continuously repeated standard time base interval of predetermined length is established and is divided into ten equal divisions corresponding to the numbers 0 through 9. An impulse at any one of these divisions in any time base interval represents the corresponding number.

An impulse appears at the output of the novel storage circuit at a time corresponding to the particular number in each time base interval following the original introduction of the number to the circuit. This output impulse continues thus to appear periodically until a new number is introduced.

'More specifically, the novel storage device includes a multi-electrode tube having two control grids it being necessary that a positive voltage be impressed simultaneously on both said control grids to cause anode current. Synchronizing means is provided to supply synchronous positive impulses to one of said control grids of the multielectrode tube; a synchronizing impulse occurring at each time division of each base interval. The'other control grid of the multi-electrode tube is connected to an RC timing circuit at a point in the RC circuit having a steady state voltage of positive value with respect to the cathode of the multi-electrode tube. A clamping circuit is provided which is efiective to clamp the grid connected to the RC circuit, and one side of the capacitor of the RC circuit, momentarily to a negative line in response to an impulse to be stored or the regeneration of a stored impulse. Following the clamping action of the clamping circuit, the time of return of said other control grid to a positive voltage depends upon the time constant of the RC circuit. This RC circuit is designed to cause said other control grid of the multi-electrode tube to become positive approximately one-half of a time division ahead of the time in the next time base interval corresponding to the original impulse. The next synchronous pulse applied to said one of said control grids of said multielectrode tube results in an output pulse and the recycling of the storage device.

The above discussion will be more clear from the detailed description that follows. In addition, however, it is well to appreciate at this time, that the interval between the initiation and ending of the discharge period of the capacitor of the RC circuit is accurately controlled.

In the drawings:

Fig. 1 is a schematic circuit diagram of the novel storage device (or delay circuit) in accordance with a preferred embodiment of the present invention; and

Fig. 2 is a graphical representation to a common time base of the approximate voltage wave forms which exist at the designated points in the circuit of Fig. l.

'The storage unit as shown in Fig. 1 includes a main control tube 11 having an anode, a cathode and at least two control grids and a screen grid. A type 6BE6 has been found satisfactory for use as the control tube. The anode of the control tube 11 is connected through a resistor 12 to a +400 volts supply line 13. The cathode of the control tube 11 is connected by line 14 to a regulator unit 15 which serves to maintain the cathode constantly at a voltage approximately one-half of the value of the voltage of supply line 13. (From the detailed discussion that follows it will be appreciated that the important feature is merely to keep the cathode of tube 11 at a potential that is a fixed percentage of the potential of supply line 13). r

The first control grid llcgl of the control tube-11 is connected through a pair of series connected resistors 16 and 17 to the =+400 volts supply line 13. It is also connected through a timing capacitor 18 to the anode of the control tube 11. The first control grid 11cg1 is also connected through clamping tube 20 to grounded line 19. The clamping tube 20 may be a triode vacuum tube, such as one-half of a type 12AT7.

The second control grid 11cg2 of the control tube 11 is connected to a suitable source of synchronizing voltage impulses designated as number impulses. Now as previously indicated, the storage unit is for use in a system wherein successive elements of time represent successive number cycles, with each cycle being divided into equal time periods, each of which represents a number value. Thus, as indicated in Fig. 2, each cycle may be divided into ten time periods with the first period in each cycle representing a 9 value and the subsequent time periods in each cycle representing 8, 7, 6, 5, 4, 3, 2, 1, and 0 values in the order named. The synchronizing number impulse source is adapted to supply a positive voltage impulse once in 3 each number value period of every cycle as shown in Fig. 2.

The two screen grids llscg' of the control tube 11 shown in Fig. 1 are connected together and through a series connected resistor 21 and inductor 22 to the +400 volts suppryune 13. In addition, the screen grids llscg are con nected through a capacitor 23 and a resistor 24 to the grounded line 19. Another resistor 25 is connected from the junction point between capacitor 23 and resistor 24 to a -250 volts supply line 26. The screen grids llscg are originally at a voltage level of approximately +400 volts, but voltage variations at the screen grids are trans mitted through capacitor 23 to the grid 27g of tube 27 which is biased at approximately '50 volts.

The suppressor grid llsg of the control tube 11 is connected internally to the cathode.

It, is apparent that if the clamping tube 20 becomes conductive, it causes the potential impressed on the first control grid llbgl to drop approximately to ground potential, i. e., line 19. This results in a Charging of the timing capacitor 18 with the plate thereof which is connected to the first control grid 11g1 being negative. If the clamping tube 20 subsequently becomes non-conductive, the capacitor 18 is discharged through resistors 12, 16 and 17 tjo gradually restore the first control grid llcgl to its original voltage level. The time constant of the discharge circuit, for reasons which will appear in connection with the subsequent discussion of the operation of the storage unit, is adjusted so that the first control grid llcgl reaches a voltage starting a flow of screen grid current approximately eight number value periods after the clamping tube 20 becomes non-conductive and reaches its maximum value which is slightly more positive than the cathode as limited by the grid current, approximately nine number value periods after the clamping tube 20 becomes nonconductive.

The arrangement is such that when the first control grid 11'cg1 of tube 11 is at the level of the grounded line 19 and the second control grid 11cg2 is at its normal level between two number impulses, the flow ofcathode current through control tube 11 is cut off with the voltage of the screen grid llscg at its original voltage level. This is the condition illustrated in Fig. 2 at thebeginning of the sp'ace impulse in the seven number value period of cycle X. The space impulse, as is explained later, causes the clamping tube 20 to become non-conductive permitting the first control grid ll'cgl to start upward. As the first control grid starts upward, each n'umber impulse on the second control grid, because of the interelectrode capacity, causes a small positive voltage impulse on the screen grids llscg. When the first control grid llcgl becomes sufiiciently positive to allow some screen grid to cathode current to flow, which occurs eight number value periods after the clamping tube 20 becomes nonco'nductive as shown in the nine number value period in cycle Y, the screen gn'd voltage level starts to drop. In one additional number value period, i. e., the eight number value period in cycle Y, the screen grid voltage drops from its original level of approximately +250 volts to a level of about +100 volts where it remains, the first control grid llcgl having reached its maximum value. The number impulse occurring in the eight number value period produces only a small impulse at the screen grid superimposed on the negatively sloping voltage as the plate transconductance is still small. When the number pulse occurs in the tenth period after the clamping tube 20 becomes non-conductive, as shown in the seven number value period in cycle Y, the first control grid llcgl has become sufficiently positive that the number impulse causes the control tube to conduct and thereby produce a negative voltage at its anode which is fed through the capacitor 18 to the first control grid 11cg1 to cut oh the tube. This action causes the screen grid voltage to rise sharply in a large impulse above its original voltage level.

The large screen grid voltage impulse occurring exactly ten number value periods after the clamping tube 20 was rendered non-conductive is employed to cause the clamp ing tube 20 to again become conductive. To accomplish this a triode tube 27 is provided as shown in Fig. l. The anode of tube 27 is connected to +250 volts supply line 28 and its grid 27g is connected to the junction of capacitor 23 and resistor 24. The cathode 27k of tube 27 is connected through the anode and cathode of triode tube 29 and a resistor 30 to 250 volts supply line 26. The cathode 27k is also connected through a capacitor 31 to the anode of an input triode tube 32. The anode 32a of tube 32 is connected through a resistor 33 to +250 volts supply line 28. The cathode 32a of tube 32 is connected to ground line 19. The cathode 27k of tube 27 is also connected directly to the grid of clamping control tube 34.

The tube 29 may be a triode. The grid of tube 29 is coupled through a capacitor 35 to a source of synchronous voltage impulses, designated as space impulses. These space impulses are to be supplied as indicated in Fig. 2, i. e., one space impulse in each number value period at a time in that period later than the number impulse. The grid of tube 29 in Fig. l is also connected through a resistor 36 to the cathode of tube 29. A capacitor 37 is connected between the cathode of tube 29 and ground line 19.

The arrangement of tube 29 is such that said tube is normally non-conductive but conducts an impulse of current each time a space impulse is supplied to its gn'd. When the tube 29 is conductive it lowers the voltage level of the cathode 27k of tube 27 to a voltage which is only slightly more positive than the -50 volts supplied to grid 27g of tube 27.

The input tube 32 is normally cut off so that its anode 32A is almost at the level of the +250 volts supply line 28. This input tube 32 functions as described herematter to cause a negative voltage impulse to appear at its anode when it is desired to store a number (or data) in the storage unit.

The clamping control tube 34 is illustrated in Fig. l as one-half of a type 12AT7 tube with its anode connected to the +250 volts line 28 and its cathode connected through resistor 38 to the 250 volts line 26. The cathode of clamping control tube 34 is also connected to the grid of the clamping tube 20 so that the operation of the clamping tube depends on the voltage level of the cathode of the clamping control tube. (Clamping control tube 34 is used as a cathode follower to supply the grid potential necessary to obtain good clamping action by clamping tube 20).

As may be seen in Fig. 2 the voltage impulses appearing at the screen grid llscg of control tube 11 are differentiated and applied to the grid 27g of tube 27. The voltage bias provided through resistors 24 and 25 keeps the grid 27g quite negative except when a large impulse appears at the screen grid llscg of control tube 11 as occurs in the seven number value period in cycle Y in Fig. 2. Since tube 29 becomes conductive once in each number value period, the capacitor 31 is charged with a polarity as indicated in Fig. 1. The relative value of the bias voltage on the grid 27g and the charge on the capacitor 31 results in tube 27 being normally cut off.

7 Preferably the arrangement is such that each space impulse causing tube 29 to conduct reduces the voltage level of the cathode 27k slightly which causes tube 27 to conduct a small amount of current which in turn causes the voltage level of the cathode 27k to rise slightly until the tube 27 is again cut ofi. Consequently the voltage level of the cathode 27k is not exactly constant in between impulses at the screen grid llscg of control tube 11. In addition each of the small impulses at the screen grid llscg causes a small current flow through tube 27. However, these variations in the voltage level of the cathode 27k of tube 27 are relatively small and have no-substantial eflect upon the overall operation; For this reason, in the interestof clarity, these small variations are not shown in the curves ofFig. 2. It is suificient to say that the voltage level of the cathode 27k andhence of the cathode of tube 34 are maintained sufliciently negative, except when a large impulse appears at the screen grid llscg of control tube '11, to cause the clamping tube 20 to remain non-conductive.

When a large voltage impulse appears at the screen grid llscg of control tube 11, exactly ten number value periods after the clamping tube 20 last became nonconductive as in the seven number value period in cycle Y (shown in Fig. 2), the tube 27 becomes conductive to make the cathode 27k and therefore the grid of the clamping control tube 34 more positive. As a result clamping control tube 34 becomes more conductive. Also, clamping tube 29 again becomes conductive because of the connection between the cathode of tube 34 and the grid of tube 29. When the next subsequent space impulse causes tube 29 to become conductive the cathode 27k is lowered to its original negative value, i. e., capacitor 31 is recharged. When the cathode 27k is thus lowered, the clamping control tube 34 is cut oil to in turn cut off the clamping tube 2%). With clamping tube 20 cut 03 discharging of the timing capacitor 18 is again initiated. Thus the clamping tube becomes non-conductive at a predetermined instant in the number value period, that is, the instant when the space impulse is supplied, so that the timing of the delay aiforded by the discharge circuit of the timing capacitor 18 is always initiated at the same relative instant in 'the number value period. Consequently, if the clamping tube 20 has been operated originally in a selected number value period, the clamping tube will thereafter be operated in the same number value I period in each successive cycle.

To store a number in the storage unit the input tube 32 is provided. The input tube 32 may be a triode. The grid 32g of tube 32 is coupled through a capacitor 39 (or any suitable coupling means) to a suitable source of positive input impulses. An input impulse occurs once in each number value period at a time within each number value period prior to the beginning of the space impulse. The grid 32g is also connected through a resistor 40 to the .250 volts supply line 26 and through another resistor 41 to a suitable bias voltage supply control designated the store command control. The store command control is arranged to supply either of two voltagelevels through the resistor 41 and is shown for purposes of schematic illustration only as a double throw switch 42 having two positions designated store and no store. In the no store position of the command control the resistor 41 is eflectively connected to 65 volts line 43 to maintain tube 32 non-conductive at all times. In the store position of the command control, the resistor 41 is effectively connected to ground line 19 so that each positive input impulse supplied to the grid 32g, While the command control is in store position, causes a corre sponding negative impulse at the anode 32a of tube 32.

Idealized wave-forms of the voltages appearing at the grid 32g and the anode 32a of tube 32 are shown in Fig. 2. With the command control in no store position, as in number value periods 9 and 6 through of cycle X and all of cycle Y, the bias on the grid 32g prevents the input impulses from causing corresponding impulses at the anode 32a. in the eight number value period of cycle X, the command control is also in no store position during the input impulse but is thereafter changed to store position so that the bias on grid 32g is made more positive and the positive input impulse in the seven number value period of cycle X causes a corresponding negative impulse at the anode 32a to store a value of 7 in the storage unit. After this impulse in the seven number value period of cycle X, the command control again returns to the no store position in the example shown. The command control may of course be any suitable control capable of changing the bias on the grid 32g of tube 32 at the proper time to permit a selected input impulse to be stored in the storage unit. (It will be appreciated that during normal operation the store command control switch may be placed in the store" position during a complete cycle or cycles).

The voltage regulating unit enclosed by broken line 15 in Fig. 1 maintains the level of the line 14 at approximately one-half of the voltage level of the supply line 13 and is in eifect a comparing device. The regulator 15 includes two comparing tubes 44 and 45 which may be the two halves of a type 12AX7 twin triode tube. The anode of the first comparing tube 44 is connected to the +400 volts supply line 13 and its cathode is connected through a resistor 46 to ground line 19. The grid of the first comparing tube 44 is connected directly to line 14 and through a capacitor 47 to ground line 19. The grid of the first comparing tube 44 is also connected through the anode and cathode of tube 48 to ground line 19.

The anode of the second comparing tube 45 is connected through a resistor 49 to the +400 volts supply line 13. The cathode of tube 45 is connected to the cathode of the first comparing tube 44. The grid of the second comparing tube 45 is connected to the midpoint, 50, of a resistive divider comprising a pair of resistors 51 and 52 connected in series between the +400 volts supply line 13 and the grounded line 19. The resistors 51 and 52 each have the same resistance so that the grid of the second comparing tube 45 is at a voltage level halfway between the voltage of supply line 13 and ground line 19. It is also evident that the grid of the first comparing tube 44 is at the voltage level of the line 14.

Another voltage divider is connected between the +400 volts supply line 13 and the 250 volts supply line 26. This divider comprises a tube 53, a pair of voltage regulator tubes 54 and 55 (such as VRl tubes) and a resistor 56. These elements are serially connected in the order recited between the supply line 13 and the supply line 26. The grid of tube 53 is connected to the anode of the second comparing tube 45. Consequently, any variation in the voltage of the anode of the second comparing tube 45 causes a corresponding variation in the voltage across the resistor 56 in the divider. The grid of the vacuum tube 48 is connected to a point 57 on' the variable voltage divider intermediate the resistor 56 and the voltage regulator tube 55. It is thus evident that the impedance across the anode and cathode of tube 48 varies in accordance with variations in the voltage across the resistor 56.

As described hereinbefore the control tube 11 becomes conductive once in each cycle. During conduction of control tube 11 the capacitor 47 in the voltage regulating unit 15 is charged. Capacitor 47 thus serves to maintain the voltage on line 14 more positive than ground line 19. The actual voltage level of line 14 is then determined by the degree of conductivity of the tube 48. The conductivity of tube 48 depends upon the voltage across resistor 56 which in turn depends upon the conductivity of tube 53 as controlled by the voltage level of the anode of the second comparing tube 45. Now the grid of the second comparing tube, it will be recalled, is at a voltage level halfway between that of supply line 13 and the grounded line 19 while the grid of the first comparing tube 44 is at the voltage level of line 14. If the level of supply line 13 should vary, a corresponding variation appears at the grid of the second comparing tube 45 to vary the voltage level of the anode of that tube. Thus, if the voltage level of supply line 13 should drop slightly, the grid of the second comparing tube 45 becomes slightly more negative causing the anode of tube 45 to become more positive. As a result, the tube 53 becomes more conductive causing an increase in the voltage across resistor 56. The increase in voltage across resistor 56 makes the grid of tube 48 more positive and the resulting increase in conductivity of tube 48 lowers the voltage level of supply line 14 slightly to match the lowered voltage level of the grid of the second comparing tube 45.

If the voltage level of supply line 13 remains constant but the voltage level of the line 14 varies, the change in conductivity of the first comparing tube 44 changes the voltage level of the cathode of the second comparing tube 45 and results in a variation in the conductivity of the second comparing tube. This change in anode voltage of the second comparing tube 45 which in turn results in a variation in the conductivity of tubes 53 and 48 brings the voltage level of line 14 into agreement with the voltage level of the grid of the second comparing tube 45.

By providing the voltage regulating unit 15 to maintain the ratio of the voltage on line 14 to the voltage on line 13 at a substantially constant value the accuracy and reliability of the storage unit is greatly increased and the voltage on line 13 may be allowed to vary over wide limits. The duration in time of the interval between the time when the clamping tube 20 becomes non-cnductive and the time when the control tube 11 becomes conductive in response to a number impulse depends primarily upon the discharging of the timing capacitor 18 to raise the level of the first control grid llcgl above a critical value relative to the level of the cathode of control tube 11, that is, the level of line 14. The time required for the grid to rise to the critical voltage relative to the cathode voltage depends upon the ratio between the voltages on lines 14 and 13. If this ratio is held constant, the time between an input pulse and each successive corresponding output pulse is constant.

To read out a value stored in the storage unit an output tube 58 is provided. The anode of tube 53 is connected to the +250 volts supply line 28. The cathode of tube 58 is connected through a resistor 59 to the 250 volts supply line and an output terminal is connected to the cathode. Thus the output tube circuit is in efiect a cathode follower circuit.

The grid of tube 58 is connected to a point 60 intermediate a pair of resistors 61 and 62 which are connected in series with each other in the order named from the cathode of the clamping control tube 34 to the read out control. The read out control may be any suitable device for applying either of two different voltages to the end of resistor 62 which is remote from resistor 61. For purposes of illustration only the read out control is shown in Fig. l as a double throw switch 63. In one position of switch 63 the resistor 62 is connected to 65 volts supply line 43. This position of switch 63 is labelled no road. In the other position of switch 63 which is labelled read the resistor 62 is connected to ground line 19. From explanations given hereinbefore it will be recalled that the clamping control tube 34 becomes conductive at the beginning of the number impulse in the number value period corresponding to the stored number (i. e., value) in each cycle and becomes non-conductive at the beginning of the subsequent space impulse in that same number value period. Each time the clamping control tube 34 becomes conductive, a positive voltage impulse appears at its cathode and is transferred through the resistor 61 to the grid of the output tube 58. When the read out control is in the no read position, the voltage level at the grid of the output tube 58 is low as compared with the voltage level at the grid of the output tube 58 when the read out control is in the read position. It is to be appreciated that a positive impulse impressed on the grid of tube 58 when said grid is at the higher of the two voltage levels will result in tube 58 being rendered conductive and an impulse appearing at the output terminal. The output impulse will occur during the number value period corresponding to the stored number. The above condition will exist and the above sequence of operation take place whenever the readout control is in the read position and a value is stored within the novel storage unit.

While the operations of various portions of the storage unit have been set forth in connection with the detailed description of those portions, it is believed that a ail) more comprehensive understanding of the operation of the storage unit may be obtained by disclosing a specific example with reference to both Fig. 1 and Fig. 2. Let it be assumed that the storage unit is in operation and has a O stored therein. Let it further be assumed that when the storage unit reaches cycle X it is desired to store a 7 therein. Now when cycle X is reached we find, as shown in Fig. 2 that number impulses are being supplied to the second control grid 11cg2 once in each number value period. A space impulse is being delivered to the grid of the tube 29 in Fig. 1 once in each number value period at a time in that period subsequent to the number impulse as shown in Fig. 2. An input impulse is delivered to the grid 32g of the input tube 32 in Fig. 1 once in each number value period at a time in each such period prior to the number impulse. The command control i in the no store position at this time so that the level of the input impulses on grid 32g remains below the critical value of the tube as reported by the broken line 64 in Fig. 2.

With a 0 stored in the unit the first control grid llcgl of the control tube 11 is at the beginning of cycle X gradually rising in voltage from the low negative value assumed in the 0 number value period of the preceding cycle when the clamping tube 20 was conductive. The gradual rise in voltage of the first control grid 11cg1 is due to the discharging of the timing capacitor 18. However, in the beginning of cycle X the voltage of the first control grid llcgl is still considerably below the critical value as reported by the broken line 65 in Fig. 2.

When the first control grid 11cg1 is at the voltage indi-' cated at the beginning of cycle X, the voltage of the screen grid llscg of the control tube 11 is at a relatively high level. The tube 27 is non-conductive and the clamping control tube 34 and the clamping tube 20 are also non-conductive.

In the nine and eight number value periods of cycle X the input impulses impressed on grid 32g do not result in the potential rising above the critical value thus the input tube 32 is non-conductive. This condition exists because the command controlis in the no store position. The number impulses in the nine and eight number value periods do cause variations in the voltage of the screen grid llscg, but the resulting voltage variations of the grid 27g of tube 27 are insufficient to cause more than a slight variation in the voltage level of the cathode 27k. For clarity these variations of the voltage level of cathode 27k are omitted in the idealized waveforms of Fig. 2. Consequently the clamping control tube 34 and the clamping tube 20 remain non-conductive in the nine and eight number value periods.

In the eight number value period after the input impulse in that period ha been delivered the store command is changed from the no store to the store position raising the voltage level of the grid 32g of the input tube 32. Then at the beginning of the seven number value period of cycle X the corresponding input impulse raises the voltage of the grid 32g above the critical value causing the input tube 32 to pass a current impulse. This results in a negative voltage impulse at the anode 32a ofthe input tube as is seen in Fig. 2. The negative impulse at the anode 32a in Fig. 1 tends to cause a similar negative impulse (not shown in Fig. 2) at the cathode 27k of tube 27. However, the grid 27g is maintained at approximately 50 volts, thus the flow of cathode current from cathode 27k prevents the potential at this point from falling significantly below -50 volts and further charging capacitor 31. At the termination of the input impulse applied to grid 32g the plate 32a of tube 32 tends to rise again to +250 volts and this rise in potential is transmitted through capacitor 31 to cathode 27k causing the potential at that point to rise to approximately ground level. When the cathode 27k is thus raised, the grid of clamping control tube 34 is likewise raised to cause the clamping control tube to become more con- 9 ductive, which in turn causes the clamping tube 20 to become conductive. When the clamping tube 20 becomes conductive the voltage of the first control grid 11cg1 of the control tube 11 is dropped almost to the voltage level of the grounded line 19. The cathode 27k of tube 27 remains at the voltage level of ground and the clamping control tube 34 and the clamping tube 20 remain conductive until the beginning of the space impulse in this same seven number value period of cycle X. While the clamping tube 20 is conductive the timing capacitor 18 is charged by virtue of the circuit extending from the +400 volts supply line 13 through the resistor 12, the timing capacitor 13 and the clamping tube 20 to ground line 19.

The space impulse of the seven number value period of cycle X is delivered to the grid of tube 29 causing that tube to become conductive to lower the cathode 27k of tube 27 to its original (negative) voltage level and held there due to capacitor 31 being re-charged. With cathode 27k at this negative voltage level, the clamping control tube 34 and the clamping tube 20 become non-conductive.

While the clamping control tube was conductive in the seven number value period of cycle X, an impulse appeared at the output terminal. However, since the read out control was in the no read position, this output impulse is at a relatively low voltage level.

When the clamping tube 20 becomes non-conductive, the timing capacitor 18 begins to discharge through resistors 12, 16 and 17 at a predetermined rate. Consequently, the voltage level of the first control grid 11cg1 gradually rises through the next several number value periods. So long as the voltage of the first control grid llcgl remains below the critical value represented by line 65 the number impulses cause only small impulses at the screen grid llscg which are insufficient to cause tube 27 to become conductive.

The rate of discharge of the timing capacitor 13 is such that approximately eight number value periods after the clamping tube 20 becomes non-conductive (i. e., eight number value periods after the seven number value period of cycle X), the first control grid llcgl becomes sufficiently positive that a substantial screen grid current begins to flow. This occurs in the nine number value period of the next cycle which is labelled cycle Y in Fig. 2. Consequently, the voltage of the screen grid llscg begins to drop rapidly. When the number impulse occurs in the eight number value period of cycle Y the screen grid voltage is still declining rapidly. Since the transconductance of the control tube 11 is still small and the voltage of grid 27g of tube 27 is lowered slightly because of the differentiation of the dropping screen grid voltage, the resulting impulse in the screen grid voltage is not effective to cause tube 27 to conduct. Toward the end of the eight number value period in cycle Y the first control gn'd 11cg1 of the control tube 11 is sufficiently positive that the screen grid voltage is levelled and is no longer dropping. Then the number impulse in the seven number value period of cycle Y causes the control tube 11 to conduct through its anode-cathode circuit. This results in a negative voltage impulse at the anode of the control tube 11, which impulse is transferred through the capacitor 18 to the first control grid 11cg1. This causes a very large positive impulse to appear at the screen grid 11scg which is transferred to the grid 27g of tube 27 to cause that tube to conduct momentarily.

When tube 27 becomes conductive in the seven number value period of cycle Y, its cathode 27k becomes more positive rising to the level of ground line 19 where it is maintained until the beginning of the subsequent space impulse in the same number value period. While the cathode 27k is at this higher level the clamping control tube 34 and the clamping tube are conductive. When the clamping tube 20 becomes conductive the timing capacitor 18 is again charged to drop the voltage of the first control grid 11cg1 of control tube 11 to its lowest value. When the clamping tube 20 becomes non conductive the capacitor 18 again begins to discharge and the voltage of the first control grid 11cg1 begins to rise.

It is then obvious that until another number is stored through the operation of the command control, the clamping tube 20 will become conductive at the beginning of the number impulse in each seven number value period of each succeeding cycle. Whenever a difierent number is to be stored in the storage unit the command control is operated to permit the corresponding input impulse to render the tube 32 conductive in the corresponding number value period. Such action will remove the stored number seven from the unit and will replace it with the new number.

When it is desired to read out the number which is stored in the storage unit, the read out control is moved into the read position at the beginning of a cycle. For example, assume that at the beginning of cycle Y this new position (i. e., read-out position) of the read out control raises the level of the output terminal as indicated in Fig. 2.

It is to be particularly noted that the clamping tube 20 is always rendered conductive as a result of a number impulse, and is rendered non-conductive as a result of the subsequent space impulse in the same number value period of the same cycle. Consequently, discharging of the timing capacitor 18 is initiated synchronously and is ended synchronously. In addition, the interval between initiation and ending of the discharging period of the timing capacitor 18 is maintained accurate by maintaining the voltage level of line 14 substantially constant. Thus the first control grid llcgl is arranged to operate between two fixed voltage levels.

While there have been shown and described and pointed out the fundamental novel features of the invention as applied to a preferred embodiment, it will be understood that various omissions and substitutions and changes in the form and details of the device illustrated and in its operation may be made by those skilled in the art with out departing from the spirit of the invention. It is the intention, therefore, to be limited only as indicated by the scope of the following claims.

What is claimed is:

1. A storage device for use in storing for an indefinite period data represented by a voltage impulse comprising, an electron discharge device including a cathode, an anode, a first control electrode, a second control electrode and a screen electrode, a resistance-capacitor network coupling said anode and said first control electrode with a first source of positive potential, voltage regulator means for maintaining said cathode at a substantially constant second positive potential, synchronous means for periodically impressing a positive potential on said second control electrode, clamp circuit means coupling said first control grid with ground potential, means coupling said screen electrode and said clamp circuit means whereby the storage device is capable of accepting an input impulse and periodically regenerating an output impulse.

2. A storage device as claimed in claim 1 wherein the means coupling said screen electrode and said clamp circuit means includes a clamping tube, a clamping control tube and an additional tube capacitively coupled to said screen electrode.

3. A storage device for use in storing for an indefinite period data represented by an electrical impulse comprising, an electron discharge device including a cathode, an anode, a first control electrode, a second control electrode and a screen electrode, a resistance-capacitor network coupling said anode and said first control electrode with a first source of positive potential and a clamping tube, voltage regulator means for maintaining said cathode at a substantially constant second positive potential, synchronous means for periodically impressing a positive potential on said second control electrode, a clamping control tube for controlling said clamping tube, a

I 1 1 first triode capacitively coupled to said screen electrode and connected to said clamping control tube, means responsive to an electrical input impulse to'be stored for energizing said clamping control tube and said clamping tube and thereby charging the capacitor of said resistancecapacitor network, and cyclic means operative after an electrical input impulse has been stored for periodically causing said clamping control tube and said clamping tube to be conductive and charge said capacitor of said resistance-capacitor network and thereby generate an electrical output impulse.

4. A storage device as claimed in claim 3 further characterized in that said cyclic means includes a second triode coupled to said first triode and said clamping control tube, and second synchronous means for periodically rendering said second triode conductive 5. A storage device for use in storing for an indefinite period data represented by an electrical impulse comprising, an electron discharge device including a cathode, an anode, a first control electrode, a second control electrode and a screen electrode, a resistance-capacitor network coupling said anode and said first control electrode with a first source of positive potential and a clamping tube, means for maintaining said cathode at a second positive potential which is a fixed percentage of the potential of said first source of positive potential, synchronous means for periodically impressing a positive potential on said second control electrode, a clamping control tube for controlling said clamping tube, a first triode capacitively coupled to said screen electrode and connected to said clamping control tube, means responsive to an electrical input impulse to be stored for energizing said clamping control tube and thereby charging the capacitor of said resistance-capacitor network, and cyclic means I operative after an electrical input impulse has been stored for periodically causing said clamping control tube and said clamping tube to be conductive and charge said capacitor of said resistance-capacitor networkand thereby generate an electrical output impulse.

6. A delay circuit for use in delaying an electrical impulse for a fixed interval of time, or any positive integer multiple of said fixed interval of time comprising, an electron discharge device including a cathode, an anode, a first control electrode, a second control electrode and a screen electrode, a resistance-capacitor network coupling said anode and said first control electrode with a first source of positive potential and a clamping tube, means connecting said cathode with a second source of positive potential, synchronous means for periodically impressing a positive potential on said second control electrode, a clamping control tube for controlling said clamping tube, a first triode capacitively coupled to said screen electrode and connected to said clamping control tube, means responsive to an electrical input impulse to be delayed for energizing said clamping control tube and said clamping tube and thereby charging the capacitor of said resistance-capacitor network, and additional repetitive means for periodically effecting the generation of an electrical output impulse.

References Cited in the file of this patent UNITED STATES PATENTS 2,482,973 Gordon Sept. 27, 1949 2,584,882 Johnson Feb. 5, 1952 2,594,104 Washburn Apr. 22, 1952 2,675,469 Harker et al Apr. 13, 1954

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