US2578273A

US2578273A - Electronic time delay device

Info

Publication number: US2578273A
Application number: US650695A
Authority: US
Inventors: George P Wachtell
Original assignee: Individual
Current assignee: Individual
Priority date: 1946-02-27
Filing date: 1946-02-27
Publication date: 1951-12-11
Anticipated expiration: 1968-12-11

Description

Dec. 11, 1951 G. P. WACHTELL ELECTRONIC TIME DELAY DEVICE Filed Feb. 27, 1946 D O W w G U 0 W C -a W L c 4 a .M /v 4 m 7 0 w My m L j f f 7 '0 a Q I 2 fi i o MU FJO rw 3 A. w

o w C o f m .IIIIIII 1 o a 4m 5 0 TIME IN MICROSECONDS TIME IN MICROSECONDS FIG.2

INVENTOR. GEORGE P. WACHTELL ATTORNEY Patented Dec. 11, 1951 ELECTRONIC TIME DELAY DEVICE George P. Wachtell, Princeton, N. J assignor, by mesne assignments, to the United States of America. as represent-ed by the Secretary of the Navy Application February 27, 19%, Serial No. 650,695

15 Claims.

This invention relates to a delay device and more particularly to a single electron tube boot strap blocking oscillator used as a delay circuit.

In high frequency radio communications it is often desirable to impart a time delay between the operation of one component part of an apparatus and the operation of another component part where these parts have an interrelation. Heretofore such a delay has been accomplished with multivibrator circuits or with 1 conventional artificial delay line circuits. Multivibrator circuits have the disadvantage of requiring two electron tubes or at least the elements of two tubes enclosed in a single envelope, with the accompanying circuit complexity. Artificial delay lines have the disadvantage of relatively large space requirements and difficulty in continuous adjustment.

It is an object of this invention to overcome the aforementioned difficulties.

Another object of this invention is to provide a compact, light-weight electronic circuit which will produce a pre-determined time delay be tween pulses of voltage.

Another object is to provide an electronic delay circuit requiring only one electron tube.

Another object is to provide an electronic dc lay circuit capable of producing a range of time delays.

A still further object is to provide a compact, light-weight electronic delay circuit capable of application in high frequency radio equipment for use in aircraft.

These and other objects will become apparent when taken with the accompanying drawings,

in which:

Fig. 1 is a schematic circuit diagram of one embodiment of the invention; and

Fig. 2 depicts wave forms representing some of the voltages found in the embodiment of Fig. 1.

In Fig. 1 of the drawings is disclosed a gas tube to, which has its plate connected to a suitable source of plate voltage through resistor l I. Input terminal I2 is connected to the control grid of tube and to one end of a resistor G3, the other end of which is connected to a source of bias of sufficient magnitude to keep tube to normally non-conducting. The cathode of tube i0 is directly connected to ground and the second grid is grounded through resistor M.

The plate of tube It! is coupled to the cathode of a triode electron tube l5 through network I6, which consists of resistor I! in parallel with resistor is and capacitor l9 connected in series.

Tube i5, which with its associated circuits 2 embodies the boot strap blocking oscillator fea ture of this invention, is normally nonconduct ing because the difference in voltage existing between the grid of tube 15 and its cathode, when tube It is in a quiescent state, is great enough to keep it cut ofi.

To the cathode of tube I5 is connected one 'erminal of capacitor 2! and one end of cathode 'esistor 2i. The other end of resistor 2! is grounded, and the other terminal of capacitor 29 connects to the grid of tube !5 through the sec ondary of pulse transformer 22. Junction point t3 of capacitor 2% and the secondary of pulse transformer 22 is connected to ground through

resistors

23 and 24 in series. The junction point of

resistors

23 and 24 is grounded through capaci tor 25, is connected to a source of positive voltage through resistor 26, and also connected to one terminal of switch 21 through resistor 28. The other end of switch 21 is directly grounded. The junction of resistor 28 and switch 21 is connected to one side of capacitor 29, the other side of which is grounded.

Junction point 49 is also coupled to the control grid of a second gas tube 30 through capacitor 3| and resistor 32 connected in series. The junction of capacitor 3| and resistor 32 is connected to a source of bias voltage through resistor 33. This bias voltage is made large enough to keep tube Bil normally non-conducting. Tube 30 has its cathode directly grounded and its second grid connected to ground through resistor 34. The plate of tube 39 connects to a source of positive voltage through resistor 35 and is also directly connected to one end of the primary side of pulse transformer 22, the other end of which is connected to the plate of tube l5. The polarities of the windings of transformer 22 are as shown in Fig. 1. A third connection is made from the plate of tube 3!] to one end of pulse forming network 36, whose other end connects to the high side of the primary of pulse transformer 31. The other side of this primary is grounded. The high side of the primary of pulse transformer 3'! also is connected to one end of pulse forming network 38, the other end of which connects directly to the plate of tube 10. The high side of the secondary of pulse transformer 3 is connected to output terminal 39 and its other side is grounded.

Referring to Fig. 1, gas tube [B is triggered into operation by apositive pulse of voltage applied to terminal l2. Previous to this, gas tube It! Tube I5 is also non-conducting as discussed hereinafter. When tube iii conducts, its plate volt age drops sharply. This voltage drop is transmitted to the cathode of tube iii thro etwcr s is and also to the grid of tube i thron tor 25 and the secondary of transfo" The cathode and grid of tube l5 experience same voltage drop, because the cathode point 5 experience the same drop due to the action of capacitor 2c and because there is no voltage drop across the grid winding of pulse transformer 22.

During the quiescent state of tube It, capacitor has acquired a charge because the cathode and grid of tube l5 are at different levels of positive voltage with the parameters of

resistor

26 and 28 so chosen that the grid is considerably less positive than the cathode. After the pulse from the plate of tube Ill has dropped both oath" ode and grid of tube below their quiescent volt- .ages, capacitor 20 starts charging back toward a new voltage level as hereafter shown with reference to Fig. 2. The cathode is held at a low posi tive level by the conduction of tube i0. Tube 15 is still in a non-conducting state, however, and will remain so until the voltage difference between its cathode and grid has decreased to cutoff magnitude. The time that tube !5 remains non-conducting, after the signal has been de livered to both its cathode and grid, is determined by three factors, namely, the rate of charging of capacitor 20, the magnitude of the initial pulse of voltage delivered to the cathode of tube i=3, and the initial potential difference between cathode and grid of tube 45.

When the potentials of the cathode and grid of tube !5 differ only by a voltage equal to the cut-off potential, tube [5 starts conducting. The current through tube [5 increases from zero. The change in current through the primary of pulse transformer 22 induces a positive voltage at the grid of tube is with respect to point as, and therefore with respect to th cathode of tube [5. The grid being somewhat more positive with respect to the cathode, the current through tube l5 increases further, the rate-of-change of current induces more voltage in the grid winding and ,drives the grid still more positive with respect to the cathode. This regenerative action continues until tube l5 saturates and can no longer increase its current flow. rent flow can no longer increase, the voltage induced in the secondary of pulse transformer 22 decays, and immediately regeneration starts in exactly the opposite direction. as before. ihis reverse regeneration continues until the grid of tube I5 is driven far enough below its cathode to again out the tube off. Tube 15 has now completed one cycle of its blocking oscillator action.

During the rapid increase of current through tube l5, its grid becomes strongly positive with respect to its cathode, and therefore a large current flows through tube 15. This current flows through resistors ii, l8, 2!, 23, and 33, in parallel, and also through the stray capacity from cathode to ground, which capacity is quickly charged up. A positive pulse of voltage, therefore, appears at the cathode. This positive pulse is coupled to the control grid of tube 3b through capacitors Eli and 3| and resistor 32, overcoming the bias voltage and driving tube 35 into conduction. It is a pulse that appears at the cathode of tube l5 only as a result of the regenerative action. Were it not for the action of the pulse transformer, a rather slowly rising signal would appear at the cathode.

When the rate of curm In The delay feature of this invention is determined by the time consumed between the triggering of tube It into operation and the subsequent triggering of tube 30 into operation. As shown before, this delay time partly depends upon the voltage difference initially existing between the grid and cathode of tube 15. Switch 2! and the network consisting of resistor 23 and

capacitors

25 and 29 provide a method of changing this voltage difference and therefore the delay time. With tube 15 in its quiescent state, both its cathode and grid are at positive potentials With its grid less positive than its cathode. With switch 2? open, the voltage on the grid of tube I5 is determined by the voltage dividing network consisting of

resistors

24 and 25 in series, but with switch 2! closed, resistor 28 is parallel with resistor 24. This reduces the quiescent voltage on the grid of tube I5 and thus makes the time delay longer. With switch 27 open, the time delay is about fifteen microseconds and with it closed approximately forty-five microseconds.

It is to be noted that gas tubes 55 and 38 are used in this embodiment only to demonstrate the operation of the delay circuit including tube i5. Other methods alternatively may be employed.

It is characteristic of a gas tube that once it has been triggered into operation, the control g-id has little or no further effect. The recovery of gas tube if? is accomplished as follows: After the pulse forming network 38 has been discharged by tube Hi, the only current through tube it flows through resistor Ii. Resistor H limits the current to a small enough value for the gas in the tube to be able to deionize in approximately fifty microseconds. At the end of this time, tube It ceases to conduct, the pulse forming network recharges exponentially through resistor H and tube It is again in its steady state condition. Resistor 35 and pulse forming network behave in an identical manner in connection with tube 30, the only difference being that there is a time delay between the identical operations, determined by the time delay of the circuit including tube [5.

In this embodiment as disclosed in 1, even though a blocking oscillator circuit is used as a delay stage, is not desirable for it to oscillate at its natural frequency 1. e. run free, for this would delay the recovery time of gas tube 33. Therefore, to prevent the blocking oscillator from running free, plate voltage is practically removed from tube i5 when tube 35 is conducting. As shown in Fig. 2, tube it remains in conduction for approximately fifty micro-seconds. Tube 353 also conducts for approximately fifty microseconds. Therefore, since tube it is triggered into conduction before tube 39, it will be out off before tube 36, thus applying cathode bias to tube i5 before the re-application of ll plate voltage.

The

pulse forming networks

33 and 38 in their steady state condition are charged. They discharge in six-tenths of a microsecond, thereby applying pulses six-tenths of a microsecond long to a load attached to terminal 33. The load is matched to the networks by transformer 3?.

In Fig. 2 are shown four wave forms which are a pictorial representation of voltage values, with respect to time, that occur at variou locations in the circuit disclosed. The pla of tube it are shown by curve A. T.-..-at portion of the curve between points 52 and 5 represents ti: steady state or quiescent value. When tube It starts conducting, the plate voltage drops sharply 5. as shown between points 54 and 56. Then for approximately fifty microseconds i. e., the length of-time that tube It conducts, its plate voltage remains at a low positive voltage. At the end of its conduction period, the plate voltage starts rising exponentially toward its steady state value as shown by the remaining portion of curve A. Since tube 30 and tube Iii are identical in operation, curve B, which shows the plate voltage values of tube 30, is exactly like curve A except that it is displaced on the time axis. The displacement is equal to the time delay as determined by the boot strap blocking oscillator circuit.

The voltages at the cathode of tube I5 are represented by curve C. Its steady state value is shown between points 62 and E4. Curve D shows the voltages at point 48. Its steady state voltage is shown between points 65 and 88, and is illustrated for the case with switch 2? closed. The grid voltages follow curve D except between points 14 to 84.

When tube H3 starts conducting and its plate voltage sharply drops, the cathode and grid of tube [5 also drop sharply. The cathode drop is shown between points 64 and i8, while the grid drop is shown between

points

68 and 12. Then for a time equal to the delay time, about fortyfive microseconds as illustrated, the cathode of tube [5 remains at a steady value of voltage but the grid voltage begins an exponential rise as capacitor 25! charges up. The steady value of cathode voltage is shown between points iii and 16, while the grid rise is shown between

points

12 and 14. When the grid of tube [5 has reached a value'of voltage indicated at point 14, the voltage difference between the grid and cathode of tube [5 is equal to cut-ofi potential and..tube l5 starts conducting. Immediately the voltages at the cathode and at point 49 jump sharply upward to points 89 and it respectively, as a result of the regenerative action described above. During this sharp rise, the regeneration between the grid circuit and plate circuit of tube 15 has been progressing at a rapid rate. But the tube reaches its plate current peak very rapidly, and the regeneration reverses, resulting in a rapid drop at both cathode and point 40. The resultant cathode potential drop occurs between points 8!! and 82 while that of the point 43 is shown between

points

18 and 84.

The reverse regeneration continues until the grid of tube I5 is driven far enough below the cathode to cut on? tube l5. Cut-on is indicated by the potential difference between 82 and 84. When tube [5 cuts-off, capacitor 29 starts charging up toward its steady state value and hence the grid starts its exponential rise towards its quiescent voltage. When tube l cuts off, the cathode of tube l starts its exponential rise toward its steady state value. The circuit is back to its quiescent state when tubes H3, and 3b are all cut ofi and the voltages as shown by the curves of Fig. 2 have completed their exponential rises. This invention need not be limited to the details shown and described, which are considered to be only illustrative of one form the invention may take.

What is claimed is:

1. A delay device comprising, a source of input pulses, an electron tube including an anode, cathode, and grid, a source of power for energizing said tube, a capacitor joining the cathode and grid of said tube, means coupling the output at said 'plateof *said tube to the gridthereofi'said grid being biased from said power source to render said tube normally non-conducting, means coupling said cathode of said tube to said pulse source, said capacitor charging after application of an input pulse from said pulse source at the cathode of said tube, the charging of said capacitor from said power source biasing said tube to become conducting and thereby produce an output pulse at a time delayed from the application of said input pulse by an amount dependent upon the rate of charging of said capacitor, the magnitude of said input pulse applied to said cathode, and the magnitude of said bias on said grid.

2. A delay device comprising, a source of input pulses, an electron tube including an anode, cathode, and grid, a cathode resistor for said tube, a capacitance and resistance network connected in parallel with said cathode resistor, a pulse transformer coupling the output at said plate to said grid, said grid being coupled through one capacitor of said network and through the secondary of said pulse transformer to said cathode, a source of power for energizing said tube, the grid of said tube being biased from said power source to render said tube normally non-conducting, said one capacitor charging from said power source after application of an input pulse from said source at the cathode of said tube and biasing said tube to become conducting, whereby an output pulse is produced at a time delayed from the application of said input pulse by an amount depending upon the rate of charge of said one capacitor, the magnitude of said input pulse applied to said-cathode, and the magnitude of said bias on said grid.

' 3. A delay device comprising, a source of negative input pulses, an electron tube including an anode, cathode, and grid, 2. source of power for energizing said tube, a cathode resistor for said tube, a capacitance-resistance network connected in parallel with said cathode resistor, a source of positive bias voltage connected to said network, said bias voltage causing said electron tube to be normally non-conducting, means for varying the value of resistance in said network to vary the bias upon said electron tube, a pulse transformer coupling the output at the plate of said tube to the grid of said tube, said grid being coupled through one capacitor of said capacitance-resistance network and through the secondary of said pulse transformer to said cathode, said one capacitor charging from said power source after application of a negative 7 pulse from said source of pulses at the cathode of said tube, biasing said tube to become conducting, whereby an output pulse is produced at a time delayed from the application of said negative pulse by an amount depending upon the rate of charge of said one capacitor, the magnitude of said negative pulse applied to said cathode, and the magnitude of said bias on said tube.

4. An electronic circuit for producing an output voltage pulse at a predetermined time interval after the occurrence of an input voltage pulse comprising, a source of direct current, a source of negative voltage pulses, an electron tube having an anode, a cathode and a control grid, said electron tube being connected as a blocking oscillator and biased to be normally non-conducting from said source, a capacitor connected to couple the grid and cathode circuits of said electron tube, and means coupling said source of pulses to the cathode of said electron tube, whereby the application of a neg ative voltage pulse'from said source to said electron tube simultaneously changes the potential levels of said gridand said cathode substantially equally and holds said cathode at a low potential while said capacitor is charged from said power source to a new value biasing said electron tube to conduction and causing a cycle of operation of said electron tube as a blocking oscillator at a time delayed from the application of said negative pulse by a predetermined amount.

5. An electronic circuit for producing an output voltage pulse at a predetermined time interval after the occurrence of an input voltage pulse comprising, a source of direct current, a source of negative voltage pulses, an electron tube having an anode, a cathode and a control grid, said electron tube being connected as a blocking oscillator and biased to be normally non-conducting from said source, a capacitor connected to couple the grid and cathode circuits of said electron tube, means coupling said source of pulses to the cathode of said electron tube, whereby the application of a negative voltage pulse from said source to said electron tube simultaneously changes the potential levels of said grid and said cathode substantially equally and holds said cathode at a low potential while said capacitor is charged from said power source to a new value biasing said electron tube to con duction and causing a cycle of operation of said f electron tube as a blocking oscillator at a time delayed from the application of said negative pulse by a predetermined amount, and means for changing the biased voltages applied to said electron tube from said source to change the predetermined delay time interval.

6. An electronic circuit for producing an output voltage pulse at a predetermined time interval after the occurrence of an input voltage pulse comprising, a, source of direct current power, a source of synchronizing trigger pulses, a pulse forming network energized from said power source, means responsive to pulses from said pulse source for discharging said network, an electron tube having an anode, a cathode and a control grid, said electron tube being connected as a blocking oscillator and biased to be normally non-conducting from said source, a capacitor connected to couple the grid and cathode circuits of said electron tube, and means coupling said network to the cathode of said electron tube, whereby discharge of said network in response to said trigger pulse applies a negative voltage pulse to said electron tube simultaneously changing the potential levels of said grid and said cathode substantially equally and holds said cathode at a lowered potential while said capacitor is charged fromsaid source to a new value biasing said electron tube to conduction at a time interval delayed from the application of said trigger pulse by a predetermined amount established by the rate of charge of said capacitor, the initial bias of said electron tube and the amplitude of negative potential applied from said network.

7. An electronic circuit for producing an output voltage pulse at a predetermined time interval after the occurrence of an input voltage pulse comprising, a source of direct current power, a source of synchronizing trigger pulses, a pulse forming network energized from said power source, means responsive to pulses from said pulse source for discharging said network, an electron tube having an anode, a cathode and a control grid, said electron tube being connected as ablocking oscillator and biased to be normally non-conducting from said source, a capacitor connected to couple the grid and cathode circuits of said electron tube, and means coupling said network to the cathode of said electron tube, whereby discharge of said network in response to said trigger pulse applies a negative voltage pulse to said electron tube simultaneously changing the potential levels of said grid and said cathode substantially equally and holds said cathode at a lowered potential while said capacitor is charged from said source to a new value biasing said electron tube to conduction at a time interval delayed from the application of said trigger pulse by a predetermined amount established by the rate of charge of said capacitor, the initial bias of said electron tube and the amplitude of negative potential applied from said network, and means for changing the bias voltages applied initially to said electron tube from said source to change the predetermined time interval of delay.

8. An electronic circuit for producing an output voltage pulse at a predetermined time interval after the occurrence of an input voltage pulse comprising, a source of direct current power, a source of synchronizing trigger 'pulses, a pulse forming network energized from said power source, means responsive to pulses from said pulse source for discharging said network, an electron tube having an anode, a cathode and a control grid, said electron tube being connected as a blocking oscillator and biased to be normally nonconducting from said source, a capacitor connected to couple the grid and cathode circuits of said electron tube, and means coupling said network to the cathode of said electron tube,

whereby discharge of said network in response to said trigger pulse applies a negative voltage pulse to said electron tube simultaneously changing the potential levels of said grid and said cathode substantially equally and holds said cathode at a lowered potential while said capacitor is charged from said source to a new value biasing said electron tube to conduction at a time interval delayed from the application of said trigger pulse by a predetermined amount established by the rate of charge of said capacitor, the initial bias of said electron tube and the amplitude of negative potential applied from said network, a second pulse forming network energized from said source, second pulse responsive means for discharging said second network, and means coupling the cathode of said electron tube to said second pulse responsive means to initiate discharge of said second pulse forming network upon conduction of said electron tube, whereby the discharge of said second pulse forming network provides an output pulse at a predetermined time interval following said trigger pulse.

9. An electronic circuit for producing an out put voltage pulse at a predetermined time inter val after the occurrence of an input voltage pulse comprising, a source of direct current power, a source of synchronizing trigger pulses, a pulse forming network energized from said power source, means responsive to pulses from said pulse source for discharging said network, an electron tube having an anode, a cathode and a control grid, said electron tube being connected as a blocking oscillator and biased to be normally non-conducting from said source, a capacitor connected to couple the grid and cathode circuits of said electron tube, and means coupling said network to the cathode of said electron tube, whereby discharge of said network in response to said trigger pulse applies a negative voltage pulse to said electron tube simultaneously changing the potential levels of said grid and said cathode substantially equally and holds said cathode at a lowered potential while said capacitor is charged from said power source to a new value biasing said electron to conduction at a time interval delayed from the application of said trigger pulse by a predetermined amount established by the rate of charge of said capacitor, the initial bias of said electron tube and the amplitude of negative potential applied from said network; a second pulse forming network energized from said source, second pulse responsive means for discharging said network, means coupling the cathode of said electron tube to said second pulse responsive means to initiate discharge of said second pulse forming network upon conduction of said electron tube, whereby the discharge of said second pulse forming network provides an output pulse at a predetermined time interval following said trigger pulse, and a pulse transformer connected to said first and second pulse forming networks to provide two output pulses separated by a predetermined time interval.

10. An electronic circuit for producing an output voltage pulse at a predetermined time interval after the occurrence of an input voltage pulse, comprising, a source of direct current power, a source of synchronizing trigger pulses, a pulse forming network energized from said source, a grid-controlled gas discharge tube shunting said network and biased to be normally non-conducting from said source, means for applying pulses from said source to bias said gas tube to initiate conduction and discharge said network, a high vacuum electron tube having an anode, a cathode and a control grid, said electron tube being biased to be normally non-conducting from said source, a transformer coupling the grid and anode of said electron tube in a blocking oscillator circuit, a capacitor connected to couple the grid and cathode circuits of said electron tube, and means coupling said network to the cathode of said electron tube so that discharge of said network by said gas tube in response to said trigger pulse acts to apply a negative voltage pulse to said electron tube by simultaneously changing the potential levels of said grid and said cathode substantially equal amounts and holding said cathode at a lowered potential while said capacitor is charged from said power source to a new value biases said electron tube to conduction and causes a cycle of operation of said electron tube as a blocking oscillator at a time delayed from the application of said trigger pulse by an amount established by the rate of charge of said capacitor, the initial bias of said electron tube and the amplitude of negative potential supplied from said network.

11. An electronic circuit for producing an out- .put voltage pulse at a predetermined time interval after the occurrence of an input voltage pulse, comprising, a source of direct current power, a source'of synchronizing trigger pulses, a pulse forming network energized from said source, a grid-controlled gas discharge tube shunting said network and biased to be normally non-conducting from said source, means for applying pulses from said source to bias said gas tube to initiate conduction and discharge said network, a high vacuum electron tube having an anode, a cathode and a control grid, said electron tube being biased to be normally non-conducting from said source, a transformer coupling the grid and anode of said electron tube in a blocking oscillator circuit, a capacitor connected to couple the grid and cathode circuits of said electron tube, and means coupling said network to the cathode of said electron tube so that discharge of said network by said gas tube in re sponse to said trigger pulse acts to apply a negative voltage pulse to said electron tube by simultaneously changing the potential levels of said grid and said cathode substantially equal amounts and holding said cathode at a lowered potential while said capacitor is charged from said power source to a, new value biases said electron tube to conduction and causes a cycle of operation of said electron tube as a blocking oscillator at a time delayed from the application of said trigger pulse by an amount established by the rate of charge of said capacitor, the initial bias of said electron tube and the amplitude of negative potential supplied from said network, and means for changing the bias voltages applied to said electron tube to change the predetermined time interval.

12. An electronic circuit for producing an output voltage pulse at a predetermined time interval after the occurrence of an input voltage pulse, comprising, a source of direct current power, a source of synchronizing trigger pulses, a pulse forming network energized from said source, a grid-controlled gas discharge tube shunting said network and biased to be normally non-conducting from said source, means for applying pulses from said source to bias said gas tube to initiate conduction and discharge said network, a high vacuum electron tube having an anode, a cathode and a control grid, said electron tube being biased to be normally non-conducting from said source, a transformer coupling the grid and anode of said electron tube in a blocking oscillator circuit, a capacitor connected to couple the grid and cathode circuits of said electron tube, and means coupling said network to the cathode of said electron tube so that discharge of said network by said gas tube in response to said trigger pulse acts to apply a negative voltage pulse to said the initial bias of said electron tube and the amplitude of negative potential supplied from said network, means for changing the bias voltages applied to said electron tube to change. the time interval by a predetermined amount, a second pulse forming network energized from said source, a second grid-controlled gas discharge tube shunting said second network and biased to be nor-' mally non-conducting from said power source, and means coupling the cathode of said electron tube to bias saidsecond gas discharge tube to initiate conduction upon the cycle of conduction of said electron tube, whereby the'discharge of said second pulse forming network by said second gas discharge tube provides an output pulse at a predetermined time interval following said 1 1 comprising, a source of direct current power, a source of synchronizing trigger pulses, a pulse forming network energized from said source, a grid-controlled gas discharge tube shunting said network and biased to be normally nonconducting from said source, means for applying pulses from said source to bias said gas tube to initiate conduction and discharge said network, a high vacuum electron tube having an anode, a cathode and a control grid, said electron tube being biased to be normally non-conducting from said source, a transformer coupling the grid and anode of said electron tube in a blocking oscillator circuit, a capacitor connected to couple the grid and cathode circuits of said electron tube, and means coupling said network to the cathode of said electron tube so that discharge of said network by said gas tube in response to said trigger pulse acts to apply a negative voltage pulse to said electron tube by simultaneously changing the potential levels of said grid and said cathode substantially equal amounts and holding said cathode at a lowered potential while said capacitor is charged from said power source to a new value biases said electron tube to conduction and causes a cycle of operation of said electron tube as a blocking oscillator at a time delayed from the application of said trigger pulse by an amount established by the rate of charge of said capacitor, the initial bias of said electron tube and the amplitude of negative potential supplied from said network, means for changing the bias voltages applied to said electron tube to change the time interval by a predetermined amount, a second pulse forming network energized from said source, a second grid-controlled gas discharge tube shunting said second network and biased to be normally non-conducting from said power source, means coupling the cathode of said electron tube to bias said second gas discharge tube to initiate conduction upon the cycle of conduction of said electron tube, whereby the discharge of said second pulse forming network by said second gas discharge tube provides an output pulse at a predetermined time interval following said trigger pulse, and a pulse transformer connected to said first and second pulse forming networks to provide two output pulses separated by a predetermined time interval.

14. An electronic circuit for producing an output voltage pulse in a predetermined time interval after the occurrence of an input voltage pulse comprising, a source of direct current power, a source of negative voltage pulses, a pulse forming network energized from said source, an

electron tube having an anode, a cathode and a control grid, said electron tube being connected as a blocking oscillator and biased to be normally non-conducting from said source, a capacitor connected to couple the grid and cathode circuits of said electron tube, means coupling said source of negative pulses to the cathode oi said electron tube so that the application of said negative voltage pulse simultaneously charges the potential levels of said grid and said cathode substantially equally and holds said cathode at a lowered potential while said capacitor is charged from said power source to a new value biasing said electron tube to conduction and causing a cycle of operation of said electron tube as a blocking oscillator at a time delayed from the application of said trigger pulse by a predetermined amount established by the rate of charge of said capacitor, the initial bias of said electron tube and the amplitude of negative pulses supplied from said source, pulse responsive means for discharging said network, and means coupling the cathode of said electron tube to bias said'pulse responsive means to initiate discharge of said pulse forming network upon the conduction of said electron tube, whereby the discharge of said pulse forming network provides an output pulse at a predetermined time interval following said negative input pulse.

15. An electronic circuit for producing an output voltage pulse at a predetermined time interval after the occurrence of an input voltage pulse comprising, a source of direct current, a source of negative voltage pulses, an electron tube having an anode, a cathode and a control grid, said electron tube being connected as a blocking oscillator and biased to be normally non-conducting from said source, a capacitor connected to couple the grid and cathode circuits of said electron tube and means coupling said source of pulses to the cathode of said electron tube so that the application of a negative voltage pulse from said source to said electron tube simultaneously changes the potential levels of said grid and said cathode substantially equally and holds said cathode at a low potential while said capacitor is charged from said power source to a new value biasing said electron tube to conduction, thereby permitting a cycle of operation of said electron tube as a blocking oscillator at a time delayed from the application of said negative pulse by a predetermined amount, a pulse forming network energized from said source, a gridcontrolled gas discharge tube biased to be normally non-conducting from said power source, means coupling the cathode of said electron tube to bias said gas discharge tube to initiate conduction therein upon conduction of said electron tube whereby thedischarge of said pulse forming network by said gas discharge tube provides an output pulse at a predetermined time interval following said input pulse.

GEORGE P. WACHTELL.

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

UNITED STATES PATENTS