US2478901A - Electric system - Google Patents

Description

Aug. l5, 1949. H, E, EDGERTON 2,478,901

ELECTRIC SYS TEM Filed Aug. 1G, 1935 4 Sheets-Sheet 2 zj Inval/:for

All-g- 16, 1949. H. E. EDGERTON 2,473,901

ELECTR I C SYS TEM Filed Aug. 16, 1933 4 Sheets-Sheet 3 f1? vew/or .Haro la7 ZY/a7 arto?? Aus 16, 1949. H, E. EDGERTON 2,478,901

ELECTRIC SYSTEM Filed Aug. 16, 1933 4 Sheets-Sheet 4 mhlllllllllll- [71 vena# Patented Aug. 16, 1949 UNITED STATES PATENT OFFICE ELECTRIC SYSTEM Harold E. Edgerton, Watertown, Mass. Application August 16, 1933, Serial No. .685,501

105 Claims.

The present invention, though having iields of more general usefulness in electric systems, is particularly related to electric-energy flash-producing systems in which the discharge of a flash condenser is employed for such purposes as to produce a single light flash or a repetition of light flashes of short duration and high intensity, as in ash-photography and stroboscopic work. The present application is a continuation-in-part of application. Serial No. 610,045, filed May 9, 1932, which matured, on December 5, 1939, into Letters Patent 2,181,879, reissued as Letters Patent 22,123, June 23, 1942, and Letters Patent 22,260, February 2, 1943. Reference may be made to the said Letters Patent and also to Letters Patent 2,186,013, issued January 9, 1940, for a description of details that, for brevity, are omitted from the present specification.

An object of the invention is to provide a new and improved electric system, and a new and improved stroboscope, that shall be simple and rugged in construction, light in weight, portable and self-contained, easily operable, without moving parts (except, in some cases. for a contactor) and thoroughly effective and reliable in operation.

Another object is to provide new and improved forms of stroboscopic-llght sources, so as to give strong and intensive illumination, and so as to permit observation of an object without submerging it in comparative darkness.

A further object is to provide new and lmproved means for controlling the stroboscopic iiashes of light, so that they may be started quickly and consistently and by means of a very small amount of electrical energy. Accurately controlled flashes aid in giving good deiinition when the stroboscopic light is used for observing periodically moving objects.

A further object is to provide a new and improved stroboscope for operation at high frequency.

A further object is to provide a new and improved electric system that shall operate reliably and at any time.

Still another object is to provide new and lmproved apparatus for producing substantially uniform electrical-energy ashes of the type in which a condenser is periodically discharged thrmigh a gaseous-conductor lamp.

Other and further objects will be explained hereinafter and will be particularly pointed out in the appended claims.

The invention will now be described in connection with the accompanying drawings, in which paratus arranged and constructed according to one embodiment of the invention; Fig. 2 is a. modication of the same; Fig. 3 is a similar view illustrating a stroboscopio light source operated by alternating current, but capable of operating at any flashing frequency: Fig. 4 is a similar view illustrating a stroboscopic light source operated at the frequency of the alternating-current supply and accurately timed to ash in phase with the applied voltage; Fig. 5 is a similar view embodying a circuit whereby several mercury-arc stroboscope lamps may be ashed in parallel; Fig. 6 is a View similar to Fig. 1, but replacing the mercury-arc tube by a spark gap; Fig. '7 is a similar view of a further modification, embodying a conducting wire; Fig. 8 is a view illustrating the use of the mercury tubes as a controlled rectifier; and Fig. 9 is a similar view of another modication.

A luminescent vapor electric gaseous-discharge ash lamp or iiash tube 2 is illustrated as provided with two internal main or principal electrodes 4 and 6 in a glass-tube envelope. In Fig. 9, a further such tube is shown at l. As these tubes are identical, it will sumce to describe only one of them. Other apparatus than the illustrated lamp 2 may also be used in accordance with the present invention. The principal electrodes I and 6 denne a principal-current path for the lamp 2. The lamp 2 is illustrated as of the lowimpedance mercury-arc gaseous-conductor type, the internal electrode l being shown as in the form of a liquid pool of mercury, used for a cathode. and the internal electrode Ii serving as the anode or plate. The remarks throughout this specication concerning mercury-arc tubes or lamps apply equally well to tubes or lamps iilled with other gases, with or without mercury vapor, and the invention, as will appear more fully hereinafter. is not limited to use with tubes for producing light.

The pressure of the mercury or other gas or vapor in lamps of this nature is normally of such value as to render the lamp 2 normally nonconductive or ineffective. The gas may become ionized, however, in response to the energization of a normally unenergized control-grid triggering or starting electrode i, to facilitate the starting of the tube 2, by initiating current flow in the principal-current path including the gaseous medium of the tube 2 deiined by the principal electrodes 4 and E. This initiation and starting are effected through the medium of a startingcurrent path extending from the starting elec- Fig. 1 is a. diagrammatic view of circuits and ap- 65 trode |00.

The electrode |60 is shown as an external metal-band condenser electrode, situated around the glass ui the envelope oi the lamp 2, outside tne mercury pool 4. opposite to tne menlscus of the mel'culy. Other types oi control-grid or starting electrodes, including electrodes oi Lne internal type. may also be employed.

A sultaule source oi direct-current energy is shown as constituted oi a battery |02. The positive terllnnal or the battery lu2 is shown connected by a wire-conductor lead Ill to the anode t, to render tile anode positive. and the negative terminal oy a wire-conductor lead to the cathoue u. eotentlal ls thus supplied across tne principal culi-ent patn between the cathode 4 and the anode 6. The direct-current voltage may. nowever, ne derived irom any desired conventional source ol alternating energy or suitable voltage ano lrequency, through a transformer M8. The primary winding |44 ol' the transiormer |46 is shown connected to the alternating-current source, and the secondary winding l4l to the conductors 8 and lll through a tbermionic or gaseous-discharge rectiner circuit. The tnermlonic or gaseous-discharge rectifier circuit may comprise a tnermlonlc or gaseous-dlscharge halfwave rectuier tube 20. as shown in Figs. 4 and 6, or a common type of ruil-wave thermlonic rectifier-and-nlter arrangement. comprising thermionic or gaseous-discharge haliswave rectifier units and 22, as shown in Figs. 3 and 9. The secondary winding |41 or toe transrormer |48 is snown connected to the anodes of the tnermionic or gaseous-discharge rectnier tubes Zu and 22. As shown in Figs. 3 and 9, iilter condensers 24 ano la and an lnductance or inductances 2J and tra may be provided as part or' the conventional source or direct current, in order to maintain a supply ol direct-current energy in the condenser 2a between tne pulses oi power rurais-nen through the rectlller units zu and 2z. rlhe condenser 15 is normally large compared to condenser 26 and may serve as a reservoir condenser.

A main discharge hash capacitor or condenser 26 is normally cnarged with energy at a predetermined rate from the source of direct current to the full potential oi that source. This charging may be errected by connecting the flash condenser 26 to the source of direct current in any desired manner, as by means of the wire conductors B and l0. The hash condenser 26 is shown connected to the source of direct-current potential in parallel with the principal electrodes 4 and 6. The electrodes 4 and 6 are therefore connected in series with the two terminals of the flash-condenser source of energy at the same time that energy is thus supplied to the flash condenser 26 from the source ofl direct current. The usual voltage to which the condenser becomes thus charged is from 200 to 2.000 volts.

The charging circuit for the condenser 26 is shown extending from the positive terminal of the battery l02, or from the rectier 20 or the rectiers 20 and 22, by way of the conductor I0, to the corresponding positive terminal of the condenser 26; and from the negative terminal of the battery |02. or from an intermediate tap of the secondary winding |41 of the transformer |48. by way of the conductor 6. to the negative terminal of the condenser 26. A current-limiting charging impedance 36 may be series-connected in the charging circuit o! the condenser 26, between the condenser 26 and its charging source of direct current. either in the wire conductor lll, as shown in Figs. 2, 4 and 6, or the wire conductor 8, as i1- lustrated in Figs. l and 3.

because or the dielectric properties of the normally deionized mercury vapor or other gas in the space ol the lamp, between the cathode 4 and the anode 6. the battery |02 or other direct-current source will oelore each ilash charge the hash condenser 26 through the impedance 35 so that the anode 6 is positive, without any oi' the energy of the battery l02 traversing that space. A dii'- iel'ence or' potential ol unvarying polarity will therefore be established between the cathode 4 and the anode 6 during the charging o1 the condenser 26.

Alter becoming thus charged, the condenser 26, as will presently be more fully explained, may be discharged through the gaseous medium of the lamp 2, between the anode 6 and the cathode 4, in the discharge circuit of the lamp 2. The lamp 2 will be recognized by persons skilled in the art as of the type in which a positive-column discharge may pass between the anode electrode 6 and the cathode electrode 4. The discharge current thus obtained from the flash-condenser source of energy results in the production of an electric-energy light flash through the lamp 2. The major portion of the energy supplied from the flash-condenser source of energy in the series-circuit connection between the terminals of the ash condenser 26 and the principal electrodes 4 and 6 is consumed in the positive-column discharge, with the result that the light flash is of high illumination intensity and short duration.

The condenser-discharge circuit is shown extending irom the positive terminal of the condenser 26, by way of the conductor I0, directly to the anode electrode 6; and from the negative terminal of the condenser 26, by way of the conductor 8, directly to the cathode electrode 4. The cathode 4 and the anode 6 of the lamp 2 are thus series-connected by the conductors 8 and I0 to the condenser 26 in this condenser-discharge circuit directly across the condenser 26. The connections are such as to enable the condenser 26 to discharge with relative rapidity through the lamp 2 between the anode electrode 6 and the cathode electrode 4 when the lamp 2 becomes conductive.

The impedance 35 should be designed sulficiently large so that, after the discharge of the condenser 26 between the cathode 4 and the anode 6, further current flow between them will be prevented until after the gaseous space in the lamp 2 between the electrodes 4 and 6 shall have again become deionized. The condenser 26 is therefore normally charged to a voltage of unvarying polarity and of magnitude insufficient to effect a discharge of the condenser through the lamp between the electrodes 4 and 6 when the lamp is non-conductive, though sufclent to effect a discharge of the condenser 26 through the lamp between the electrodes 4 and 6 when the lamp is conductive. The impedance 35 should, however, be small enough to permit of the re-establishment of suicient difference of potential between the cathode 4 and the anode 6 to enable recharging of the condenser 26 with energy from the direct-current source in time for the next ash. These ends may be attained by rendering the impedance 35 sultably reactive, as by constituting it of a wire conductor comprising a combination of resistance and inductance. The size and characteristlcs of the impedance 35 should be determined by the characteristics of the dash lamp 2 or other apparatus in connection with which it is used and the desired time interval between the condenser-discharges. This feature is claimed in a copending divisional application, Serial No. 688,406, tiled August 5. 1946.

The quantity of stroboscopic light is determined by the amount of energy in the condenser 26 and by circuit conditions. The capacity of the condenser 28 is increased until there is sufficient average light for the particular frequency of flashing and the extraneous illumination. Slow speeds require a larger amount of light per iiash than fast speeds to give the same average illumination. As it is necessary to have very bright flashes when the speed of flashing is slow, switches 3 and 6 are shown in Fig. 3 for connecting additional capacity 2l in parallel with the condenser 26 and thus to increase the brightness of the flash.

The discharge of the flash condenser 26 through the condenser-discharge circuit above described is initiated by energizing the normally unenergized starting electrode |00, under the control of a trip circuit. The trip circuit is shown comprising a second normally non-conductive or ineffective gaseous-discharge triggertube device |40, a small auxiliary capacitor or condenser 28, a second suitable direct-current source of energy, such as a second battery |0i, or some rectified source of alternating energy for charging the small auxiliary condenser 28 at a predetermined rate, and a normally ineffective triggering or trip ash transformer 38. For deniteness, the larger ash condenser 26 may be referred to as a rst condenser, and the small auxiliary condenser 28 as a second condenser.

A further such trip circuit is shown in Fig. 9 comprising a second such tube |48a, a second such capacitor 28a, and a second such transformer 30a. As these tripcircuits are alike, the similar elements thereof are referred to by the same reference numerals except for the additional distinguishing reference letter a, and it will sufiice to describe only one of them.

The geasous-discharge device |40 may be constituted of a mercury-vapor thyratron, a gaslled hot-cathode thermionic tube, a grid-controlled cold-cathode arc-discharge tube or any other suitable discharge device. The transformer 3D may be of the high-ratio step-up or any other desired type, with a relatively lowimpedance primary winding 36, and a secondary winding 29, shown connected between the cathode 4 and the external electrode |88. The before-mentioned starting-current path of the lamp 2, extending from the starting electrode |08 to the cathode 4, includes the inductance of the secondary winding 28. The trip circuit may contain other elements also; for example, in Fig. l, the two impedances 3| and 33, both shown resistive, and connected into circuit with the source of potential lill,

The trip circuit may perform its function o! initiating the discharge of the condenser 28 through its discharging circuit by converting the direct current of the second source of potential. such as the battery IUI, into very sudden voltage pulses in the primary Winding 3i of the flash transformer 38. These, as will be described more fully presently, will be manifested as alternating-current pulses in the secondary winding 29 or 29a.

As the tube |40, like the lamp 2, may be a rectiiier of the arc-like discharge type, conductive in one direction only, it serves also as an electric check valve. It is shown provided with at least three electrodes. Two of these are main or principal electrodes, namely, an anode or plate 52 and a cathode 48. The third is a controlgrid electrode 58. These three electrodes correspond to the anode 8. the cathode 4 and the control electrode |08, respectively, of the flash lamp 2. The tube |40, like the tube 2, may be of the type having an abrupt characteristic. To energize the tube |40, therefore, a maximum predetermined potential may be impressed across it. between its two main or principal electrodes, without appreciable current flow between these electrodes, and a substantially constant potential difference may be impressed between the control electrode and one of the principal electrodes. The gas pressure of the tube |48 is such that the control electrode 58 loses control over a discharge already passing through the tube. The electric discharge of the second small condenser 28, as will presently be more fully explained. may be initiated to produce a current between the anode electrode 52 and the cathode electrode 48 by suitably controlling the third electrode 58.

The trip circuit is provided with a normally unenergized control input circuit and an output circuit. These will iirst be described in connection with the trip circuit of Fig. 1.

The output circuit of the trip circuit, of Fig. 1, or of the thyratron |40, may be traced from the cathode 48, through the primary winding 36 of the flash transformer 38 and the small second condenser 28, to the anode 52. This output circuit of the trip circuit of Fig. 1 is connected to the lamp 2, since it includes the inductance of the primary winding 36 of the ash transformer 38. the secondary winding of which has before been described as connected in the starting-current path of this lamp 2,

It has been stated that the small second condenser 28 in this output circuit of the trip circuit is charged from the battery lill. The impedance 33 is shown as a bleeder resistor, shunted across. or connected in parallel with, the small condenser 28. The impedance 33 is also connected in parallel with the output circuit of the trip circuit. comprising not only the condenser 28, but also the cathode 48 and the anode 52 of the tube |48 and the primary winding 36 of the flash transformer 38, connected in series. The positive terminal of the battery IDI is connected to one terminal of the small second condenser 28 and one terminal of the bleeder resistor 33 and the negative terminal of the battery ||l| is connected to the other terminal of the small condenser 28 and the other terminal of the bleeder resistor 33, through the resistor 3|. Power is thus obtained for the thyratron |40 and for charging the small second condenser 28 in the output circuit of the trip circuit from the battery lill. in series with the resistor 3|. The trip-circuit output circuit of Fig. 1, comprising the primary winding 36, the tube |40 and the small second condenser 28, in series, may therefore be regarded as obtaining its energy from this small condenser 26, after becoming charged from the battery IDI. The battery lili may, however, also be regarded as included Within the output circuit of the trip circuit of Fig. 1. The resistor 3| may perform a function similar to that of the impedance 35 in the charging circuit of the condenser 26. The resistance of the resistor 8| may initially be so adjusted as to prevent self-operation of the trip circuit when the small second condenser 28 becomes charged.

The contrpl input circuit of the trip circuit oi Fig. 1 is the same as the input or grid circuit of the thyratron or other gaseous-discharge tube |40. It may be traced from the cathode 48, through the primary winding 36, the impedance 3| and the secondary winding of the trip or grid transformer E4, the function of which will be explained presently, to the control grid electrode 50. The connection of the bleeder resistor 33 to the battery before described is such as to allow a small current to flow in the resistor 3l. A voltage becomes thereby established across the resistor 3| for impressing upon the control grid 50 of the thyratron |40 in this control input circuit a normal bias suitably negative with respect to the thyratron cathode 48. The control grid 50 is connected to the negative end of the resistor 3|. As will hereinafter appear, advantage is taken of this normally negative voltage bias provided by the resistor 3| upon the control grid 50 to render the normally ineffective tube |40 effective at desired instants of time.

The discharging circuit for the small condenser 28, in the trip circuit of Fig. l, may therefore be traced from one terminal of the condenser 28, through the tube |40 and the primary winding 36, in series, to the other terminal of the small condenser 28. As soon as the normally nonconductive gaseous-discharge trigger tube |40 of the trip circuit is rendered conductive, therefore, the energy of the small condenser 23 is discharged through both the thyratron |40 and the primary winding 36, in series.

The conversion effected by the trip circuit of the direct current of the battery ||l| into alterhating-current pulses may be effected by this discharge of the small condenser 2B through the primary Winding 36 of the flash transformer 30.

The condensers 26 and 2B, however, may be charged through the impedance from a common direct-current source of potential, shown in Fig. 3 as the reservoir condenser 25. As the system of this Fig. 3 is fully described and specifically claimed in Letters Patent 2,342,257, issued February 22, 1944, to which reference may be made, it will not be further described herein.

The output circuit of the trip circuit or of the tube of Fig. 2 may be traced from the cathode 43, through the small second condenser 28 and an impedance 33, shown as a resistor, connected in parallel, and through the primary winding 36, to the negative terminal of the battery |0l. The output circuit is completed from the positive terminal of the battery |0l, through a variable impedance I9, shown as a resistor, to the anode 52. As in the case of the trip circuit of Fig. 1, therefore. the battery IDI is included in the output circuit of the trip circuit of Fig. 2 also. An impedance 3|, shown as a resistor, is connected in parallel between the cathode 48 and the anode 52. A by-pass condenser, not shown, is usually shunted across the battery |0| to bypass the current surges that charge the condenser 28. This by-pass condenser may serve as the source of energy for the output circuit of the trip circuit of Fig. 2.

The inductance of the primary winding 36 in the starting-current path of the tube 2 is therefore connected in the output circuit of each of the trip circuits of Figs. 1 and 2, between the cathode 48 and the plate or anode 52, in series with the small second condenser 2li. The output circuit of the trip circuit of Fig. 1, however, as

before described, is connected in shunt to the second battery IUI. In the trip circuit of Fig. 2, on the other hand, the small second condenser 28, the primary winding 36 and the tube |40 are connected in series with the battery |0l.

The control input circuit of the trip circuit of Fig. 2, or the input or grid circuit of its thyratron |40 may be traced from the cathode 48, through the small second condenser 2B and the impedance 33, in parallel, and through the primary winding 36. as before described, to the negative end of the battery |0l. This control input circuit is completed by way of the impedance |42, shown as a resistor, and the secondary winding of the transformer 64, to the control-grid electrode 50. The negative terminal of the resistor |42 is connected to the negative terminal of the battery lill. The negative bias upon the control grid 5U through the resistor |42 is developed across the resistor 33 from the battery IUI in the circuit extending from the positive terminal of this battery |0|, through the resistors I9, 3| and 33, and through the primary winding 36, to the negative terminal of the battery Illl.

Because of the normally negative potential bias impressed on the control grid 50 in the control input circuit of the trip circuit of each of Figs. 1 and 2, therefore, the output circuit is maintained normally open, to render the thyratron |40 normally non-conductive.

The control-grid electrode 50 may be caused to determine the exact instant when the normally non-conductive thyratron |40 shall become conductive. This control by the grid electrode 50 may be exercised by suitably modifying the potential difference between the negatively biased control grid 50 and one of the principal or main electrodes, as the cathode 4l, to a predetermined critical value in order to energize the normally unenergized control input circuit of the trip circuit. This may be effected by subjecting the control grid 50 to a suitable stimulus, as will be described hereinafter. The normally open output circuit of each of the trip circuits of Figs.

1 and 2 thereupon becomes closed or completed from the anode 52 to the cathode 43, in series with the low-impedance primary winding 36 and the small second condenser 2B.

Referring first to the trip circuit of Fig. 1, the small second condenser 28 having meantime become charged, the energy thus stored in the condenser 28 becomes suddenly discharged through this output circuit of the trip circuit, between the anode 52 and the cathode 48. A sharp violent high-potential single electrical transient impulse becomes thus quickly. accurately and reliably impressed very suddenly. for a brief interval of time, upon the primary winding 36 of the thyratron trip circuit, at the exact instant desired, accompanied by a sudden surge of current therethrough.

The resulting high potential trip surge across the terminals of the secondary winding 23 becomes conveyed, accurately and reliably, to impress a high-potential stimulus between the starting electrode |00 and the cathode 4 of the tube 2. In response to this sudden energization of the starting electrode |00. a triggering surge or puise of current becomes thereupon suddenly initiated in the starting-current path between the control electrode |00 and the cathode electrode 4, resulting in the formation of a bright cathode spot of light on the surface of the mercury-pool cathode 4 at the Junction between the mercury and the inner wall of the glass tube 2. A source of electrons becomes thereupon created upon the mercury cathode 4, in the vicinity of th'e cathode spot. These electrons ionize the normally un-ionized ga's in the normally non-conductive lamp 2. to render it conductive. The flash condenser 26 having previously become charged to a suitable potential, it thereupon, at the exact instant determined by the potential impulse upon the control grid D, discharges quickly and violently to initiate current flow through the principal current path, including the gaseous medium of the lamp 2, between the cathode electrode 4 and the anode electrode 6. This violent electrical transient surge of current through the gaseous medium of the lamp 2 between the cathode 4 and the anode 6. thus produced in response to the potential stimulus impressed upon the thyratron grid 50, initiates, as before stated, a very brilliant intense quick sharp clear flash of light of high illumination intensity. At the instant of discharge. the current surge through the lamp 2 is very great. It may be over one thousand amperes.

Because of the low impedance of the mercury lamp 2, the duration of the flash discharge is short, of the order of microseconds, as determined by the size of the capacity 28, the dimensions of the lamp 2, its volt-ampere characteristics, its temperature, the impedance of the conductors 8 and i0 connecting the condenser 26 and the lamp 2, and other factors. The inductance of the conductors 8 and I8 is useful in extinguishing the arc, as it tends to make the discharge current oscillatory. Under some conditions, the duration of the flash is less than even one microsecond,

The arc through the lamp 2 is not maintained, but is promptly extinguished, because of the current-limiting action of the impedance 35. At the end of a predetermined interval of time, therefore, the current now in the principal-current path becomes discontinued. The condenser 2S becomes thereupon again charged, in preparation for the next discharge.

The tube |40 therefore serves as a relay for accurately timing the starting of the mercuryarc tube 2. A timing impulse of only a few microamperes of current in the control input or grid circuit of the thyratron or other gaseousdischarge tube |40, to stimulate the grid 50, in the manner more fully described hereinafter, will effect the discharge of the small second condenser 28 through the output circuit, including the primarv winding 36, at just the instant of time desired.

The timing voltage impulses in the control input circuit of the trip circuit for stimulating the control grid 50, in order to raise it to the predetermined critical value necessary to trip the thyratron |40, so as to render it conductive, may be obtained through the medium of an external signal. If the signal is reproduced at a predetermned rate repetitively, many times a second, at selected intervals determined by the predetermined rate, the resulting periodically produced flashes may be used, for example, for stroboscopic purposes; for the apparent speed of e. moving objectbecoznes thereby so eiectively reduced, and the moving object moves so inappreciable a distance during the period of the ash, that it appears to be "stopped. Single signals, however, may also be used, as in flash photography.

In the trip circuit of Figs. 1 and 2, the external signal for rendering the tube 2 conductive is produced in the control input circuit with the aid of the trip or grid transformer 64 from an oscillator G2. The transformer 64 may be of the type that iwill yield a peaked secondary voltage. In response to the oscillation pulses of the oscillator 62, impulse charges become suddenly impressed intermittently upon the thyratron control grid 50 in order suitably to modify the potential thereof. It is in this manner that the potential of the control grid 58 intermittently becomes sutliciently critical with respect to the potential of the cathode 48 of the thyratron |48 to energize the normally unenergized control input circuit of the trip circuit, in order to render the thyratron lli! conductive.

Referring again to Fig. 1, the small second condenser 28 discharges suddenly through the output circuit of the trip circuit in response to each oi' these impulses in order to establish suddenly the before-mentioned violent high-potential single electrical transient pulse in this cutout circuit. A high-potential gradient becomes thus established in the output circuit in response to each such discharge of the small second condenser 28.

Corresponding energizing pulses are thereupon produced intermittently in the transformer 30 to eiect sudden transient energizations of the normally unenergized starting electrode illil, intermittently to render the lamp 2 suddenly conductive at times determined by the discharges of the small second condenser 28. At each such discharge of the small condenser 28, the normally ineffective transformer 30 becomes thus suddenly effective to subject the starting electrode of the tube 2 to a relatively high potential. This, as before stated, renders the tube 2 suddenly conductive, in order that a current impulse may be obtained through the gaseous medium of the tube 2, by the discharge of the condenser 28, between the cathode 4 and the anode 6, to produce the flash. This result is effected without the aid of any switches in the high-voltage circuit. merely by having the oscillator G2 supply periodically the signal charges to the grid 50.

The duration of each such sudden discharge of the condenser 28 through the output circuit constituted of the small second condenser 2B produced by the before-described impulse upon the control grid 50 is short compared to the times between successive discharges of the small second condenser 28. This is because the control grid 5i) is normally maintained at a potential such as to render the thyratron |48 normally non-conductive during times long comnared to the duration of the pulse in the trio output circuit. Because of the suddenness of the operation, the thyratron or other tube H0 becomes effective with corresponding suddenness to render the lamp 2 suddenly conductive.

In the trip circuit of Fig. 1. an energizing pulse is impressed suddenly upon the primary winding 36 of the transformer 30 by a discharging surge of current from the source of energy constituted of the small second condenser 28. A corresponding sudden energizing pulse may equally well be produced in the primary winding 3B by e chsrgf ing surge of current, during the charging of the small condenser 28, however, as occurs in the trip circuit of Fig. 2. In this case, the pulse is produced suddenly from the battery lill or the before-mentioned by-pass condenser. not shown. In the trip circuits of both Figs. 1 and 2, the control electrode 58 loses control over the thyratron 11 |40 upon the initiation by the condenser 28 of the sudden current impulse in the output circuit.

In the trip circuit of Fig. 2, when the tube |40 is rendered conductive, in response to a voltage pulse upon the control grid 50, from the transformer 54, the potential of the cathode 4B is raised to nearly that of the anode 52. This results in a charging surge of current into the small second condenser 28 and, at the same time, through the output circuit, including the primary winding 36. During the ensuing discharge, a sudden very strong negative bias becomes reestablished upon the grid 50.

The surge in the control input circuit may, oi course, be brought about in other ways also, as by the use of electrical transients in transformers, or by impulses from photo-electric cells, amplifiers, etc. In the trip circuits of Figs. 3, 6 and 1, as a further example, the signal for controlling the flashes of light is supplied to the grid 50 through the closing of a switch contactor 32. Upon the closing of the switch contactor 32. at any time after the condenser 28 has become charged, the grid 50 of the thyratron |40 will receive a potential stimulus of the same nature as already described. to effect the discharge oi the small second condenser 28 into the primary winding 36.

The input circuit of the trip circuit or the inprut or grid circuit of the thyratron |40, of Fig. 3, may be traced from the cathode 48. through an adjustable impedance I9, shown as a resistor, and impedances 3| and |42, also shown as resistors. to the control-grid electrode 50. The tripping is performed by a control series circuit between the control grid 50 and the anode 52. In this control series circuit, the control grid 50 is shown connected to one side oi' the switch 32 through a trio condenser 59, which may be as small as 0.00025 microfarads, in parallel with a leak resistor |43. The other side of the switch 32 is connected to the anode 52. The control grid 30 is connected also to the negative end of the resistor 3|, in series with the resistor |42. The resistance of the resistor |42 limits any current that may tend to rlow when the grid 50 becornes positive. or when there is any ionization in the tube. Especially in variable-speed stroboscopes. the adjustment of the impedance i9 may be employed to vary the intensity of the starting voltage applied to the starting-grid electrode I 00.

The output circuit of the trip circuit or of the thyratron |40 of Fig. 3 may be traced from the cathode 4B, through the variable impedance I9. the small condenser 28 and the primary winding 33. to the anode 52.

The input circuit of the trip circuit of Figs. 6 and 7 is the same as that of Fla'. 1, with the exiception that the secondary winding of the transformer 64 of Fig. 1 is replaced by an impedance |42. shown as a resistor. The tripping is performed by a control series circuit of nature similar to that described in connection with Fig. 3.

In the trip circuits of Figs. 3. 6 and '1, the closing of the switch contactor 32 may be controlled in any desired manner. manually or automatically. An example of an automatic control. ef- Seated tifirouzh the medium of a periodically movable member. is described in the said Letters Patent 2,181,879. I'he switch 32 may be very small, since it need carry only very small (myrents.

The present invention. therefore. makes it possible to operate the system without any switches or other movingparts, except, in some cases, as

12 with the aid oi the very small switch contacter 32, for causing the thyratron or other gas-discharge tube |40 to function.

By varying the frequency of the oscillator 62 or the speed of operation of the switch 32 of the illustrated trip circuits, it is possible to vary the number of times per second that the external signal ls applied to the control grid 50 to control the thyratron or other gaseous-discharge device |40 to render it conductive. The predetermined rate at which the signal is applied may thus be varied to vary the selected intervals of flashing.

The rate of flashing may be controlled, however, by suitably varying the frequency in other ways also. The voltage-impulse stimulus may, for example, be transmitted from the control circuit to the output circuit of the trip circuit, and from this output circuit to the lamp 2, to produce the flashes of light, without any outside aid, such as the oscillator 62 of Figs. 1 and 2 or the switch contactor of Figs. 3, 6 and 7, purely through self-oscillation oi' the system. The tripping surges in the grid circuit may be supplied by transformer or capacity coupling, as commonly used in the art, or in any other desired manner.

The control may, for example, be effected by varying the impedance 3| or 33, as, for example, by connecting the control grid 50 to various taps on the impedance 3| or 33. The adjustment of either tap may thus control the ashing rate of the condenser 28 and. therefore, the frequency of the high-voltage surges that become impressed upon the starting electrode |00.

The impedances 3| and 33 need not, however, be resistive. If, for example, the impedance 3| is reactive, or ii' there are other circuit conditions such that the voltage of the grid 50 may exceed the critical starting potential, the thyratron circuit may, under certain conditions, generate its own oscillations at a frequency determined by the circuit constants and the characteristics oi the tube |40. 'I'he thyratron or other gaseous-discharge device |40 will then oscillate as a self-excited relaxation oscillator. The electrical impulses for stimulating the thyratron control grid 50 in order to initiate the discharges of the condenser 26 through the lamp 2 at the desired selected intervals may thus be produced at a controlled rate determined by the adjustment of this self-excited relaxation oscillator. The manner of connecting the grid 50 for self-oscillation will depend upon the characteristics of the particular thyratron or other gasecus-discharge device |40 that is used.

The oscillator 62, the switch 32 and the selfexcited oscillations are alternative arrangements, all fully equivalent for the purpose of producing the above-described stimulus upon the thyratron control grid 50 for causing the discharge of the flash condenser 26 through the lamp 2. In all cases, the light ashes will occur accurately and reliably, at just the desired selected intervals, in response to the discharge of the condenser 26 through the tube 2, once during each cycle of the oscillations of the oscillator 62, or of the self-oscillations, or once corresponding to each closing of the very small switch contacter 32. In all cases, the voltage impulses will thus occur at the instant that the current ow through the tube |40 is conveyed, through the transformer 30, to the flash-producing apparatus.

The electrical parameters of the discharging circuit of the condenser 26, including the condenser 26 and the inductance of, the lead conductors 8 and I0, are such that, if the discharge device 2 we re substantially equally conductive in both directions between the principal electrodes 4 and 6, this condenser-discharging circuit would be oscillatory. For brevity, therefore, I shall hereinafter use this term oscillatory" to describe lthis condenser-discharging circuit.

Although the discharge or gaseous-conductor device 2 is illustrated and described as a rectifier. it will be obvious that the invention is not limited thereto, but that the invention may be practised with the aid of any other means having similar rectifier characteristics. Any discharge device or gaseous-conductor or other means may be employed in accordance with the present invention that has rectifier characteristics enabling it to conduct appreciable current in one direction but preventing it from conducting appreciable current in the opposite direction under the predetermined conditions of the reverse voltage applied to it by reason of the oscillatory nature of the condenser-discharging circuit.

The oscillatory tendency of the discharging circuit of the condenser 26 is useful, however, since it assists in preventing a continuous flow of current through the lamp 2 from the directcurrent power supply, such as the battery |02. The condenser 26 is charged with a potential of an opposite polarity after a surge of current iiows through the tube 2. A negative voltage is thus put on the anode E, which helps to deionize the tube.

As the thyratron |40 is a rectier, the current in the circuit comprising the condenser 23 and the transformer 3u cannot oscillate, although there is a tendency to do so.

As explained in the said Letters Patent, one characteristic of the present invention is that the iight produced by the tube 2 may be of much higher instantaneous intensity than is attainable with ymercury tubes the light of which is continuous, instead of periodic.

The circuit arrangement illustrated in Fig. 9 is very useful for obtaining high-frequency Stroboscopic light when efficiency is important. As already stated, the two tubes 2 and 'l are of the salme character. and the trip circuits for controlling them are also of the same character, so that they are designated by the same reference numerals, differing only by the reference letter a. The tube 'l may be referred to as a rst gaseousconductor Stroboscopic rectifier tube and the tube 2 as a second such tube.

As has also already been stated, the directcurrent source illustrated in Fig. 9 is substantially of the same nature as is illustrated in Fig. 3. An impedance |48, shown as a resistor. is connected in parallel to the reservoir condenser 25, however. and the iiash condenser 2E is connected, in parallel with a leak resistor |49. across the reservoir condenser 25 and the resistor |48, in series with the tube 1.

The same voltage of unvarying polarity before described as impressed from the rectified source of direct current across the cathode 4 and the anode 6 of the tube 2 is therefore impressed also across the cathode 4 and the anode 6 of the tube 1. That voltage is in both cases of magnitude insuiicient to produce a current impulse from the source through the gaseous-conductor tube 2 or 1 between the electrodes 4 and 6 when the tube 2 or I is non-conductive, but sumcient to produce such a current impulse when the tube 2 or 'l is conductive.

Under the control of its trip circuit, through the flash transformer 30, in the same manner as before described. the normally non-conductive tube l will be rendered conductive in advance of the tube 2. The same type of current impulse that has before been described as obtained during the discharge of the condenser 26 through the tube 2 will therefore be obtained through the tube 1 during the charging 0f this same condenser 26. The difference between this operation of the two tubes 2 and 'l is analogous to that between the operation of the two thyratrons |40 of Figs. 1 and 2, respectively; just as the former is energized during the discharge of the condenser 28 and the latter during the charging of the condenser 28, so the tube 2 is energized during the discharge of the condenser 2E of Fig. 9 and the tube I during the charging of this same condenser 26.

The rst stroboscopic or rectifier tube 1, therefore, flashes in advance of the second tube 2 of Fig. 9, during the pulse of current that is transmitted to the condenser-charging circuit to charge the condenser 26. After the condenser 26 has become charged, another pulse of current becomes transmitted through the starting-current path to initiate current flow through the principal-current path between the cathode 4 and the anode 6 of the tube 2 under the action of the capacitor 26. A second flash is obtained when the second tube 2 short-circuits the condenser 26. Two thyratron trip circuits feed into the primary windings 3E, 36a of the transformers 3D and lilla that start the tubes 1 and 2. The tubes 2 and 1 are thus energized alternately to charge and discharge the condenser 26 alternately.

The control input circuits of the two trip circuits of Fig. 9 may be respectively traced from the cathode 48 or 48a, through an impedance 3i or 3Ia, shown as a resistance, and the secondary winding of a transformer 5I or 5ta, to the control-grid electrode 50 or 50a. The output circuits of these trip circuits may be traced from the cathode 48 or 48a, through the small condenser 28 or 28a, serving as sources of energy for the respective output circuits, and the primary winding 3B or 36a, in series, to the anode 52 or 52a. The thyratrons are tripped alternately by connecting their grids 5U. 50a to a source i4| of alternating voltage by transformers 5I and 5Ia which are degrees out of phase, or by any other means, to accomplish the desired result. The circuit shown in Fig. 9 is especially effective at high frequency since the time for deionization is long. The circuit of Fig. 9 constitutes the subject matter or a divisional application, Serial No. 522,662, filed February 16, 1944.

In Fig. 4, there is illustrated a circuit by means of which it is possible to produce stroboscopic light of the same frequency as the alternating source of power |44, and the light dashes are accurately timed at the same relative position of each cycle. Stroboscopic light of this nature is useful for such purposes as examining induction and synchronous motors. and for accurately determining speed.

The anode of a further thermionic or gaseousdischarge half -wave rectifier tube 2| is connected to a tap IBI of the transformer secondary winding |41. The cathode of the further rectifier 2i is connected in series with an adjustable impedance 3i, shown as a resistor, to charge the second condenser 2l. The connection of the condenser 28 to the cathode of the rectider 2| through the resistor 3| is similar to that of the cathode oi'the rectler 20 through the impedance 35 to the condenser 26. The rectifier 2| thus charges the condenser 28 from the same alternating source |44 of voltage as the condenser 26, but through the impedance 3|.

The cathode of the rectifier 2| is shown connected also through the impedance 3|, shown as a resistor, to the anode 52 of the thyratron |40, similarly to the connection of the cathode of the rectifier 20 to the anode 6 of the lamp 2. The grid 50 of the thyratron |40 is connected through the resistor |42 to that end of the further secondary winding |60 of the transformer |48 that is negative during the half-cycle while the condensers 26 and 28 are being charged.

While the grid 50 is negative, the thyratron is ineffective and, therefore, the condensers 28 and 26 are permitted to accumulate a charge. On the succeeding half-cycle, the grid 50 swings Positive and trips the thyratron |40 which, in turn, causes the main condenser 26 to discharge through the mercury-arc tube 2, as has been previously explained.

The control input circuit of the trip circuit of Fig. 4 may be traced from the cathode 48, through the primary winding 36, by way of the conductor 8, through the portion i60 of the secondary winding |41, and through an impedance |42, shown as a resistor, to the control-grid electrode 50. The output circuit of the trip circuit may be traced from the cathode 48, through the primary winding 36, by way of the conductor 0, and through the small auxiliary condenser 20, to the anode 52. The small condenser 26 is charged by a charging circuit extending from the terminal |6i of an intermediate portion of the secondary winding |41, through the half-wave rectier 2| and an impedance 3 I shown as a resistor, and through the small condenser 26. to the other terminal of the intermediate portion of the secondary winding |41. The half-wave rectifier 2| converts the alternating current supplied by the intermediate portion of the secondary winding |41 into direct current for this output circuit.

The circuit of Fig. 4 constitutes the subject matter of a divisional application, Serial No. 688.405, filed August 5, 1946.

Fig. 5 illustrates a method of operating mercury-arc stroboscope tubes in parallel, each tube 2 being in parallel with a condenser 26. As many tubes may be operated together as are needed to produce the quantity of light which is desired. The anodes 6 and corresponding ends of the con. densers 26 are all connected together and to the positive end of the supply of power, such as the battery |02. by the conductor I0. The other ends o1 the condensers 26 and the cathodes 4 are connected together, and to the negative end of the battery |02, through the impedances 35. The external grid |00 and other starting connections are all tied together and energized by means of the common step-up transformer 30. Four such parallel connected, one foot long, stroboscopic lamps and four discharge condensers are eiective for taking motion-pictures on continuously movlng films with stroboscoplc light.

The charging lmpedances 36 may be equally well placed in series with each anode 6, and the cathodes 4 may be connected together. A separate step-up transformer 30 may, if desired, be used with each tube 2, and several thyratrons |40 may be used and tripped together by having a common grid circuit.

The control input circuit and the output circuit of the trip circuit of Fig. 5 are the same as those of Fig. l. The trip circuits of Fig. 8 are also the same as the trip circuits of Fig. 1, except for the addition of an impedance |42, shown as a resistor, in the control input circuit.

In the circuits of Figs. 6 and '7, the mercuryarc tube 2 is replaced by a spark gap |50 in air, with a starting electrode. The thyratron |40 is tripped by a transient surge in a grid circuit when the switch 32 is closed. as has been previously explained in connection with Fig. 3. This tripping arrangement makes it possible accurately to time the instant when the spark occurs, without having any switches in the high-voltage circuit. The energy of the condenser 20 produces a high voltage across the secondary winding 29 of the step-up transformer 30, at the moment when the thyratron is started. This high voltage onizes the air in the vicinity of the spark gap |50. thereby reducing the insulating properties of the air to such an extent that a spark is initiated. A bright and quick flash of light is thus produced by the spark. The energy for the spark discharge is taken from the condenser 26, which has been previously charged from the transformer |48 and the rectifier 20. The stroboscopic light from this source is very brilliant and is concentrated in a small space, which makes it very convenient for foscusing on a small area.

According to the modification of Fig. 6 that is shown in Fig. 7, a small wire |52 may be placed in series with the spark gap |50. and used as a source of light. Under some conditions, the wire |52 gives more light than the gap |50, with a somewhat shorter light duration. Fig. shows the manner in which the thyratron trigger circuit is used to give the main condenser discharge at the desired moment.

The circuits which have been described herein are useful for many other purposes than for the production of stroboscopic light. They are useful with almost any apparatus adapted for excitation by electrical impulses through the medium of a condenser. One such use is illustrated in Fig. 8, which shows two mercury-arc tubes 2 so connected ln a rectier circuit that the load current can be regulated by varying the time of the cycle at which the arc is started. The load |63 may be connected either in the cathode or the anode circuit, in series with the impedance 35. A separate thyratron tube |40 ls supplied for each tube 2, coupled thereto through a separate transformer 30, and set into operation by a separate trip transformer 64. The load |63 is supplied with direct current from the transformer |48 and rectifier tubes 2. in series with an impedance. A voltage is thus accurately and reliably applied to the primary windings 36 of the transformers 30 from the batteries or other sources of direct voltage |0|, so as to be transmitted to the input circuits of the tubes |40 and the starting bands |00 in a sudden manner that makes the corresponding tubes 2 start reliably at the same relative position of each cycle at a time determined by the voltage connected to the transformers 64.

The starting of the discharges through the tubes 2 is controlled in accordance with the alterations in the transformers 64. The transformers 64 may be of the type that will Yield a peaked secondary voltage. This will give the grid circuit of the thyratron a rapid voltage change and thus tend to eliminate any uncertainty in the iring time. By varying the phase of the alternating current in the transformer 64 17 with respect to the alternating current in the transformer |48, the moment of discharge through the tubes 2 may be accurately and reliably controlled.

The present invention has many uses. such. for example, as a rectifier switch, for giving pulses of power to cathode-ray tubes, X-ray tubes, etc. A mercury-arc tube. made similar to an inverted U, can have a starting band at each end and the current can be permitted to flow either direction.

Further modifications will occur to persons skilled in the art, and all such are considered to fall within the spirit and scope of the invention. as defined in the appended claims.

What is claimed is:

1. A stroboscope having, in combination, a mercury tube, means comprising a transformer for subjecting the mercury in the tube to a relatively high potential, and means comprising gridcontrolled, gaseous-discharge, rectifier for controlling the transformer.

2. A stroboscope having, in combination, a gaseous-discharge device having a cathode. a condenser arranged to be charged from a source of electricity connected to said device, means including a starting electrode for causing a source of electrons to exist at said cathode and rendering said device conductive, and means including a second discharge device controlling the operation of said starting electrode for controlling the discharge of said condenser through said first-named discharge device.

3. A stroboscope having. in combination, a

Agaseous-discharge tube having an anode and a cathode, a condenser arranged to be charged from a source of electricity connected to said anode and said cathode, a control electrode for rendering said tube conductive, and means including a second discharge tube connected to said control electrode for controlling the discharge of said condenser through said rst-named gaseous-discharge tube.

4. A stroboscope having, in combination, a luminescent-discharge device, a main circuit including said luminescent-discharge device and means for causing a surge of current to flow through said luminescent-discharge device. a grid-controlled, gaseous-discharge, rectifier tube haying a control input circuit and a control output circuit, an auxiliary circuit connected to said main circuit and including said control output circuit, and means connected with the control input circuit for rendering the rectifier tube eifective and initiating the surge of current through the luminescent-discharge device.

5. In combination, a discharge device having a starting electrode, a condenser connected to said device arranged to be charged from a source of electric energy, a transformer having a primary winding and a secondary winding connected with the starting electrode, a rectifier tube having a grid, a second `onclenser arranged to be charged from a source of electric energy in series with the rectifier tube and the primary winding of the transformer, and means connected with the grid of said rectier tube for causing said second condenser to discharge through said primary winding, thereby causing said rst condenser to discharge through said discharge device.

6. Apparatus of the character described having, in combination, a capacitor, means connecting the capacitor with a source of energy to charge the capacitor from the source, a luminescent-discharge device having a control grid,

a grid-controlled. electron-discharge device, a circuit in which the electron-discharge device is connected, means controlled by the electron-discharge device for causing a surge of current to flow in the said circuit to the said control grid of the luminescent-discharge device, and means controlled by the said control grid oi the luminescent-discharge device to cause the capacitor to discharge through the luminescent-discharge device.

7. Apparatus of the character described having, in combination, a normally ineifective luminescent-discharge device having a normally unenergized control electrode for rendering the device effective when energized, a tube having a control circuit and an output circuit, a transformer having a primary winding and a secondary winding. means connecting the secondary winding to the control electrode, means connecting the primary winding with the output circuit, a capacitor in the output circuit and adapted to be charged from a source of current, and means connected with the control circuit for causing a surge of current to oW through the capacitor and the primary winding, thereby to energize the control electrode through the secondary winding.

8. Apparatus of the character described having, in combination, a normally ineffective luminescent-discharge device having a normally unenergized control electrode for rendering the device effective when energized, a tube having an anode, a cathode and a control electrode, an input circuit connecting the cathode and the control electrode, an output circuit connecting the cathode and the anode, means for normally maintaining a bias upon the control electrode of the tube to maintain the output circuit normally open, a capacitor in the output circuit, means connecting the capacitor in circuit with a source of current, and means connected with the input circuit for causing a surge of current to flow through the capacitor to control the energizing of the iirst-named control electrode.

9. An electrical apparatus for producing intermittent light at controlled intervals of time comprising a gaseous-discharge lamp having a control electrode with an electrical circuit for controlling the electrode to flash the lamp and an amplifier for controlling the instant of flash.

10. A stroboscope having, in combination, a gaseous-discharge tube having an anode, a cathode and a starting electrode, a condenser connected between the anode and the cathode, means for charging the condenser, a second condenser, a grid-controlled discharge tube for controlling the starting electrode, the grid-controlled discharge tube having an input circuit and an output circuit in which the second condenser is connected, and means for intermittently controlling the input circuit to energize the starting electrode intermittently and thereby to produce intermittently a source of electrons at the cathode, whereby the rst-named condenser will become enabled to discharge intermittently between the cathode and the anode to produce intermittent flashes of light.

ILA stroboscope having, in combination, a luminescent-discharge device having a startingr electrode, a condenser connected to said device arranged to be charged from a source of electric energy, a transformer having a primary winding and a secondary winding connected with the starting electrode, a discharge rectier tube having a grid, and means connected with the grid 19 of said rectifier tube for energizing the transformer to energize the starting electrode, thereby to cause said condenser to discharge through said discharge device.

12. A stroboscope having, in combination, a gaseous-discharge tube having an anode, a cathode and a starting electrode, a condenser connected between the anode and the cathode, means for charging the condenser, a second discharge tube connected in circuit with the cathode and the starting electrode, an oscillator, and means controlled by the oscillator for intermittently opening and closing the circuit to render the circuit intermittently effective to energize the starting electrode intermittently and thereby to produce intermittently a source of electrons at the cathode, whereby the condenser will become enabled to discharge intermittently between the cathode and the anode to produce intermittent flashes of light.

13. In combination with apparatus for producing electrical-energy flashes of the type in which a condenser is periodically discharged through a gaseous-conductor lamp, means for initiating discharge of the condenser at selected intervals consisting of a relaxation oscillator for producing electrical impulses at a controlled rate, said relaxation oscillator comprising a grid-controlled device for producing electrical impulses connected in circuit with a source of potential and with means for varying the impulse rate, and means ior conveying such impulses to the flash producing apparatus.

14. In combination with apparatus for producing electrical-energy flashes of the type in which a condenser is periodically discharged through a gaseous-conductor lamp. means for initiating discharge of the condenser at selected intervals consisting of a relaxation oscillator for producing electrical impulses comprising a gridcontrolled device i'or producing electrical impulses in series circuit with a source of potential and with a second condenser, means for varying the impulse rate, and means for conveying such impulses to the fiash-produclng apparatus.

15. In combination with apparatus for producing electrical-energy ilashes of the type in which a condenser is periodically discharged intervals consisting of a relaxation oscillator for initiating discharge of the condenser at selected intervals consisting of a relaxation oscillator for producing electrical impulses at a controlled rate, said relaxation oscillator comprising a gas-containing grid-controlled device for producing electrical impulses connected in circuit with a source of potential, a second condenser shunted across the device, means for varying the impulse rate, and means for conveying such impulses to the flash-producing apparatus.

16. In combination with an electric-discharge device of the type incorporating a plurality of principal electrodes between which an electric discharge is to pass and a starting electrode disposed adjacent to one of said principal eectrodes for initiating said discharge; a capacitor, means for charging said capacitor, means including a second electricdischarge device havins a control electrode and coupled to said capacitor and said starting electrode to provide a discharge path for said capacitor. and means controlled by said control electrode so to discharge said capacitor that the electric discharge between said principal electrodes shall be initiated.

17. In combination with an electric-discharge device of the type incorporating a plurality o! principal electrodes between which an electric discharge is to pass and a starting electrode disposed adjacent to one of said principal electrodes ior initiating said discharge; a capacitor, means for charging said capacitor, a second electric discharge device having a control electrode and a plurality ol principal electrodes, means for coupling said second-named principal electrodes to said capacitor and said starting electrode to provide a discharge path for said capacitor, and means for coupling said control electrode to said starting electrode, thereby so to discharge said capacitor that the electric discharge between said ilrst-named principal electrodes shall be initiated.

18. In combination with an electric-discharge device of the type incorporating a plurality of principal electrodes between which-an electric discharge is to pass and means for initiating the discharge including a plurality of electrodes; a capacitor, means for charging said capacitor, means including a second electric discharge device having a control electrode and connected in circuit with said capacitor and said last-named electrodes, and means controlled by said control electrode so to discharge said capacitor that the discharge between said principal electrodes shall be initiated.

19. An electric system having, in combination, a normally non-conducting gaseous-discharge device having an anode and a mercury-pool cathode, means for connecting the anode and the cathode to a. source of energy, the device having a normally unenergized starting electrode for producing when energized a cathode spot at the mercurypool cathode, thereby to render the device conducting to effect a discharge from the source through the device between the cathode and the anode, a tube having a normally unenergized control input circuit and an output circuit, means for connecting the output circuit to the starting electrode, means for energizing the control input circuit. a condenser. means for charging the condenser, and means responsive to the energization of the control input circuit for causing the condenser to discharge suddenly through the output circuit to establish a high-potential gradient in the output circuit, thereby to energize the electrode suddenly at a time determined by the discharge of the condenser.

20. An electric system having, in combination. a normally nom-conducting gaseous-discharge device having a cathode, means for connecting the device to a source of energy, the device having a normally unenergized starting electrode for producing when energized a source of electrons at the cathode, thereby to render the device conducting to eifect a discharge from the source through the device, a normally unenergized gridcontrolled gaseous-discharge device connected to the starting electrode, means for energizing the grid-controlled device, a londenser, means for charging the condenser, and means responsive to the energization of the grid-controlled device for causing the condenser to discharge suddenly to establish a high-potential gradient, thereby to energize the starting electrode suddenly at a time determined by the discharge of the c denser.

21. In combination, a normally non-conductive electric valve comprising at least two principal electrodes and a control member associated with one of said principal electrodes for rendering said electric valve conductive between said principal electrodes, a source oi.' potential, a capacitance.

2l means for charging the capacitance from the source, and means comprising a grid-controlled gas-filled electric valve for transmitting a relatively large transient electrical impulse through said control member and said capacitance to render conductive said first-mentioned electric valve.

22. In an electric system, a normally ineffective discharge device having a control electrode for rendering the device effective. means connecting the discharge device into the electric system, and means comprising a grid-controlled gaseous-discharge rectifier for controlling the electrode to produce an initiating Surge of current or voltage across the discharge device. thereby to render the device effective, the gas pressure of the rectifier being such that the grid loses control over a discharge already passing through the rectifier.

23. An electric system having, in combination, a capacitor, means for connecting the capacitor with a source of energy to charge the capacitor from the source, a normally ineffective discharge device having a starting electrode for rendering the device effective, a discharge circuit connecting the capacitor and the device, and means including an electric-discharge device for controlling the electrode to cause a surge of current to flow in the discharge circuit, thereby to render the device effective.

24. A light-flash producer having. in combination, a normally non-conducting luminescentdischarge lamp having two principal electrodes between which a discharge may pass when the lamp is conducting to produce light and a normally unenergized control electrode operative when energized to render the lamp conducting, means for connecting the principal electrodes to a source of energy to cause energy from the source to discharge between the electrodes through the lamp when the lamp is conducting to produce a flash of light, a normally ineffective gaseousdischarge rectifier having a control electrode and operative when effective to energize the control electrode of the lamp, means for producing an impulse upon the control electrode of' the rectifier, and means operative in response to the impulse upon the control electrode of the rectifier for rendering the rectifier suddenly effective, thereby to effect sudden energization of the control electrode of the lamp to render the lamp suddenly conductive.

25. A light-flash producer having, in combination, a normally non-conducting luminescentdischarge lamp having twoprincipai electrodes between which a discharge may pass when the lamp is conducting to produce light and a normally unenergized control electrode operative when energized to render the lamp conducting, means for connecting the principal electrodes to a source of energy to cause energy from the source to discharge between the electrodes through the lamp when the lamp is conducting to produce a flash of light, an oscillator, means comprising the oscillator for producing a transient impulse, and means operative in response to the transient impulse for effecting sudden energization of the control electrode.

26. A light-flash producer having, in combination. a normally non-conducting luminescentdischarge lamp having two principal electrodes between which a discharge may pass when the lamp is conducting to produce light and a normally unenergized control electrode operative when energized to render the lamp conducting, means for connecting the principal electrodes to a source of energy to cause energy from the source to discharge between the principal electrodes through the lamp when the lamp is conducting to produce a flash of light, a normally ineffective gaseous-discharge rectifier having e. control electrode and operative when effective to energize the control electrode of the lamp. a. condenser, means for charging the condenser, means for producing an impulse upon the control electrode of the rectifier. and means operative in response to the impulse upon the control electrode of the rectifier for causing the condenser to discharge suddenly through the rectifier to render the rectifier suddenly effective, thereby to effect sudden energization of the control electrode of the lamp to render the lamp suddenly conductive.

27. A light-flash producer, having, in combination. a normally non-conducting gaseous-discharge lamp having an anode, a cathode and a normally unenergized starting electrode operative when energized to render the lamp conducting, a normally ineffective transformer operative when effective to energize the starting electrode, a condenser. means for charging the condenser and for discharging the condenser into the lamp between the anode and the cathode when the lamp becomes conducting. and a rectifier for rendering the transformer effective.

28. A light-flash producer having. in combination, a normally non-conducting luminescentdischarge lamp having an anode, a cathode and a normally unenergized starting electrode, means for connecting the anode and the cathode to a source of energy. a normally unenergized transformer, means for connecting the transformer to the starting electrode to energize the starting electrode when the transformer is energized. thereby to render the lamp conducting to cause energy from the source to pass between the anode and the cathode through the lamp in order to produce a flash of light, an electricdischarge device. and means for producing a transient impulse to cause the electric-discharge device suddenly to energize the transformer, thereby to energize the starting electrode to render the lamp suddenly conducting.

29. A light-flash producer having, in combination, a normally non-conducting gaseous-discharge lamp having an anode and a cathode, a normally ineffective transformer operative when effective to render the lamp conducting, a condenser, means for charging the condenser, means for discharging the condenser between the anode and the cathode through the lamp when the lamp becomes conducting, a second condenser. means for charging the second condenser, and a grid-controlled gaseous-discharge rectifier for discharging the second condenser to render the transformer effective.

30. A light-dash producer having. in combination, a normally non-conducting gaseous-discharge lamp having a control electrode and at lleast two principal electrodes, namely. an anode and a. cathode, between which, when the lamp is conducting, a discharge may pass to produce a flash of light of substantial illumination intensity, a condenser connected to the anode and the cathode, means for charging the condenser. a normally ineffective gas-filled device adapted when effective to connect the control electrode in circuit with one of the principal electrodes to render the lamp conducting, thereby to cause the condenser to discharge between the anode and the cathode to produce the said flash of light, and means for rendering the device effective.

31. A light-flash producer having. in combination, a gaseous-discharge lamp that is normally non-conducting when not in operation and having an anode and a cathode between which. when the lamp is conducting, a discharge may pass to produce a ash of light of substantial illumination intensity. a condenser connected to the anode and the cathode, means for charging the condenser, the lamp having a control electrode that is normally ineffective when the lamp is not in operation for rendering the lamp conductive when effective to enable the charged condenser to discharge between the anode and the cathode. a gasdilled device through which a discharge may pass to render the control electrode eiiective, means for producing a discharge through the device, the device having a control electrode that is normally M ineffective when the device is not in operation for initiating when effective the operation of the means for producing a discharge through the device, the gas pressure of the device being such that its control electrode has no control over a discharge already passing through the device, and means for rendering the control electrode of the second-named device effective to initiate the operation of the means for producing a discharge through the device.

32. A light-flash producer having. in combination, a gaseous-discharge lamp that is normally non-conducting when not in operation and having an anode and a cathode between which, when the lamp is conductingI a discharge may pass to produce a flash of light of substantial illumination intensity, a condenser connected to the anode and the cathode, means for charging the condenser, the lamp having a control electrode that is normally ineiective when the lamp is not in operation for rendering the lamp conductive when effective to enable the charged condenser to discharge between the anode and the cathode, a gasilled device through which a discharge may pass to render the control electrode effective, means for producing a discharge through the device, the device having a control electrode that is normally ineffective when the device is not in operation for initiating when effective the operation of the means for producing a discharge through the deviceI the gas pressure of the device being such that its control electrode has no control over a discharge already passing through the device, and a condenser for controlling the second-named control electrode to initiate the operation of the means for producing a discharge through the device.

33. A light-Hash producer having, in combination, a. normally non-conducting gaseous-discharge lamp having an anode and a cathode between which, when the lamp is conducting. a discharge may pass to produce a ash of light of substantial illumination intensity, the lamp having a starting electrode for causing a source of electrons to exist at the cathode to render the lamp conducting, means for producing the said discharge when the lamp is conducting, a. gas-filled device through which a discharge may pass to cause the starting electrode to produce a source of electrons at the cathode, means for producing a discharge through the device, the device having a normally ineffective control electrode for initiating when effective the operation `of the means for producing a discharge through the device. the gas pressure or the device being 24 such that its control electrode has no control over a discharge already passing through the device, and means for rendering the control electrode of the device effective to initiate the operation of the means lor producing a discharge through the device.

34. A light-llash producer having, in combination, a gaseousnischarge lamp that is normally non-conducting when not in operation and having an anode and a cathode between which, when the lamp is conducting, a discharge may pass to produce a flash of light of substantial illumination intensity, the lamp having a starting electrode for causing a source of electrons to exist at the cathode to render the lamp conducting. means for producing the said discharge when the lamp is conducting, a gas-lled device having a control input circuit that is normally unenergiced when the device is not in operation and an output circuit, means for connecting the output circuit to the starting electrode, means for energizing the control input circuit, a condenser. means for charging the condenser, and means responsive to the energization of the control input circuit for causing the condenser to discharge through the output circuit to cause the starting electrode to produce a source of electrons at the cathode, the gas pressure of the device being such that its control electrode has no control over a discharge already passing through the device.

35. A light-flash producer having, in combination, a normally non-conducting gaseous-discharge lamp having an anode and a cathode between which` when the lamp is conducting, a discharge may pass to produce a ilash of light of substantial illumination intensity, the lamp having a normally inefiective control electrode for rendering the lamp conducting when eiective, means for producing the said discharge when the lamp is conducting, a transformer having a, primary winding and a secondary winding, means connecting the secondary winding to the control electrode. a gas-filled device connected in circuit with the primary winding and through which a discharge may pass to render the lamp conducting, and means for producing a discharge through the gas-lilled device for energizing the transormer to render the control electrode effective, the gas pressure of the device being such that its control electrode has no control over a discharge already passing through the device.

36. A light-hash producer having. in combination, a normally non-conducting gaseous-discharge lamp having an anode and a cathode between which, when the lamp is conducting, a. discharge may pass to produce a flash of light of substantial illumination intensity, the lamp having a normally ineifective starting electrode for causing a source of electrons to exist at the cathode to render the lamp conducting, means for producing the said discharge when the lamp is conducting, a transformer having a. primary winding and a secondary winding, means connecting the secondary winding to the starting electrode. a gas-filled device connected in circuit with the primary winding. means for producing a. discharge through the device, the device having a normally ineiective control electrode for initiating when effective the means for producing a discharge through the device, the gas pressure of the device being such that the control electrode has no control over a discharge already passing through the device. and means for rendering the control electrode effective to energize the primary winding to cause the secondary winding to energize the starting electrode.

37. A ashqamp system having, in combination. a hash-lamp, a condenser for discharging through the hash-lamp, a charging circuit for connecting the condenser to a source of energy, a gaseous-discharge trigger device, a second condenser, a transformer having a primary winding and a secondary winding, means connecting the second condenser and the primary winding to a source of energy, means connecting the secondary winding to the flash-lamp, and means for discharging the second condenser through the gaseous-discharge device, thereby causing the first-named condenser to discharge through the hash-lamp.

38. A flash-lamp system having, in combination, a flash-lamp having a starting electrode, a condenser for discharging through the flashlamp, a charging circuit for connecting the condenser to a source of energy, a gaseousdischarge trigger device, a second condenser, a transformer having a primary winding and a secondary winding, means connecting the second condenser and the primary Winding to a source of energy, means connecting the secondary winding to the starting electrode, and means for discharging the second condenser through the gaseous-discharge device, thereby causing the first-named condenser to discharge through the flash-lamp.

39. In combination with an electric-discharge device of the type incorporating a plurality of principal electrodes between which an electric discharge is to pass and a starting electrode disposed adiacent to one of said principal electrodes for initiating sad discharge, a source of alternating-current energy for the discharge device, a capacitor, means for charging the capacitor, a second electric-discharge device, means for coupling the second electric-discharge device between the capacitor and the starting electrode to provide a discharge path for the charge on the capacitor, and means for coupling the second electric-discharge device to the source for coupling the capacitor, after it has been charged, to the starting electrode and the principal electrode adjacent thereto so to discharge the capacitor that a pulse of current is transmitted through the starting electrode and the electric discharge between the first-named principal electrodes is initiated.

40. A light-flash producer having, in combination, a luminescent-discharge lamp having an anode and a cathode, a condenser, means for charging the condenser, means for connecting the condenser to the anode and the cathode, a discharge device having a control input circuit and an output circuit, an oscillator connected with the input circuit, and means for controlling the input circuit in response to the oscillations of the oscillator to produce between the anode and the cathode through the lamp successive sudden discharges of energy of the condenser, each energy dscharge oi' duration short compared to the time between the successive condenser discharges, thereby to produce in the lamp successive well dened light flashes of high intensity.

41. A light-ash producer having, in combination, a gaseous-discharge lamp for producing light flashes of substantial illumination intensity having a control electrode and at least two principal electrodes, namely, an anode and a cathode, between which a. discharge may pass, a condenser connected to the anode and the cathode, means for charging the condenser, the lamp being normally non-conducting when not in operation and the anode and the cathode are connected to the condenser, a gas-iilled device through which a discharge may pass, means for passing a dischargethrough the device, the gas pressure of the device being such that its control electrode has no control over a discharge already passing through the device, and means for connecting the control electrode in circuit with one of the principal electrodes to render the lamp conducting when a discharge is passed through the gasiled device in order that the charged condenser may discharge between the cathode and the anode to produce a flash of light of substantial illumination intensity.

42. In combination with apparatus of the type in which a condenser is periodically discharged through a gaseous-conductor device, means for initiating discharge of the condenser at selected intervals consisting o! a relaxation oscillator for producing electrical impulses at a controlled rate, said relaxation oscillator comprising a grid-controlled device for producing electrical impulses connected in circuit with a source of potential and with means for varying the impulse rate, and means for conveying such impulses to the apparatus.

43. In combination with apparatus of the type in which a condenser is periodically discharged through a gaseous-conductor device, means for initiating discharge of the condenser at selected intervals consisting of a. relaxation oscillator for producing electrical impulses at a controlled rate, said relaxation oscillator comprising a grid-controlled device for producing electrical impulses in series circuit with a source of potential and with a second condenser, means for varying the impulse rate, and means for conveying such impulses to the apparatus.

44. In combination, a tube having an anode, a mercury-pool cathode and a starting electrode, a condenser connected between the anode and the cathode, means for charging the condenser, a transformer having a primary winding and a secondary winding, means connecting the secondary winding between the cathode and the starting electrode, and means for intermittently energizing the primary winding to cause the secondary winding to energize the starting electrode intermittently and thereby to produce intermittently a source of electrons on the mercury-pool cathode, whereby the condenser will become enabled to discharge intermittently between the cathode and the anode.

45. A flash-producer having, in combination, a condenser connected with a source of energy so as to be charged from the source, a flashlamp having an anode and a cathode connected to the condenser and having also a control electrode, a discharge device, a transformer having an input circuit connected to the discharge device and an output circuit c innected to the cathode and the control electrode. and means connected to the discharge device for causing the condenser to discharge through the hash-lamp.

46. In combination, a luminescent-discharge device having a starting electrode, a condenser connected to said device arranged to be charged from a source of electric energy, a transformer having a primary winding and a secondary winding connected with the starting electrode, a gridcontrolled discharge rectiiier tube having a grid, a second condenser arranged to be charged from a source oi electric energy in series with the rectiiif r tube and the primary winding of the transformer'. and means connected with the grid of sind rectifier tube for causing said second condenser to discharge through said primary winding, thereby causing said first condenser to dls charge through said discharge device.

47. Apparatus of the character described having. in combination, an impedance, a capacitor, means connecting the impedance and the capacitor with a source of energy to charge the capacitor from the source through the impedance. a luminescent-discharge device provided with a conlrol grid, the device having a cathode adapted to emit electrons under the control of the grid, and means comprising a discharge device controlling the operation of the grid for controlling the discharge of the capacitor through the luminescent-discharge device.

48. In combination. an electric-discharge device having a principal-current path defined by a plurality of principal electrodes and a startingcurrent path extending from a starting electrode for initiating current flow in said principal path, means for supplying a potential across said principal path, a capacitor, means for charging said capacitor at a, predetermined rate, a second electric-discharge device of the arc-like discharge type, and means for connecting said capacitor, said second discharge device and said starting path in series. whereby, when said capacitor is charged to a predetermined potential. said second discharge device is energized, a current is transmitted through said starting path and current now in said principal path is initiated, said current flow being discontinued after a predetermined interval of time.

49. In combination, an electric-discharge device having a plurality of electrodes at least one of which is composed of mercury and another of which ls a starting electrode defining a principalcurrent path and a starting-current path for initiating current flow in said principal path, means for supplying a potential across said principal path, a capacitor, means for charging said capacitor at a predetermined rate, a second electric-discharge device of the arc-like discharge type, said second discharge device having a control electrode and a plurality of principal electrodes. means for impressing a substantially constant potential difference between said control electrode and one of said principal electrodes. and means for connecting said capacitor, said second discharge device and said starting path in series, whereby, when said capacitor is charged to a predetermined potential, said second discharge device is energized, a current is transmitted through said starting path and current now in said principal path is initiated, said current flow being discontinued after a predetermined interval of time.

50. In combination, an electric-discharge device having a. plurality of electrodes at least one of which is composed of mercury and another of which is a starting electrode defining a principalcurrent path and a starting-current path for initiating current iiow in said principal path, means for supplying a potential across said principal path, a capacitor, means for charging said capacitor at a predetermined rate, a second electric-discharge device of the arc-like discharge type, said second discharge device having a control electrode and a plurality of principal electrodes, means for impressing a substantially constant potential dlierence between said control electrode and one of said principal electrodes, and means for connecting said capacitor. said second discharge device and said starting path in series. whereby. when said capacitor is charged to :1 predetermined potential, said second discharge device is energized, a current is transmitted through said starting path, and a discharge in said principal path is initiated.

51, In combination, an electric-discharge device having a principal-current path defined by a plurality of principal electrodes and a startingcurrent path extending from a starting electrode lor initiating current ow in said principal path, means for supplying a potential across said principal path, a capacitor, means for charging said capacitor at a predetermined rate. a second electric-discharge device of the type having an abrupt characteristic arranged to require a predetermined potential to be impressed thereacross to energize it, and means for connecting said capacitor, said second discharge device and said starting path in series, whereby, when said capacitor is charged to impress said predetermined potential across said second discharge device, the latter is energized, a current is transmitted through said starting path, and current flow in said principal path is initiated.

52. In combination, an electric-discharge device havlng a principal-current path defined by a plurality of principal electrodes and a starting current path extending from a starting electrode for initiating current flow in said principal path, a capacitor connected between said principal electrodes, means for charging said capacitor, and means for transmitting a pulse of current through said starting path after said capacitor has been charged to initiate current flow through said principal path under the action of the potential of said capacitor, said means including a normally non-conductive discharge device having a control electrode and a plurality of prncipal electrodes, and means for impressing a potential between said control electrode and one oi' the said last-named principal electrodes to render the normally non-conductive discharge device conductive.

53. In combination, a luminescent discharge device having a control electrode and a plurality of principal electrodes and having rectier characteristics, a discharging circuit including the principal electrodes, the electrical parameters of the discharging circuit being such that, if the luminescent discharge device were conductive in both directions between the principal electrodes, the discharging circuit would be oscillatory, means for causing a surge of current to flow through the discharge device between the princi- ,pal electrodes, and means including a grid-controlled discharge rectifier tube for producing an initiating surge of current between the control electrode and one of the principal electrodes.

54, A stroboscope having, in combination. an impedance and a. capacitor connected in series with a source of direct current, whereby energy from the source is fed to the capacitor through the impedance to charge the capacitor, a gaseousconductor lamp provided with an anode, a cathode and a control grid, means connecting the anode with a terminal of the source and a termina] of the capacitor and connecting the cathode with the other terminal of the source and the other terminal of the capacitor to produce, during the said charging of the capacitor from the source, a difference of potential between the cathode and the anode, with the anode positive with respect to the cathode, the pressure of the gas of the lamp being normally of such value that the lamp is normally deionized in order to render the lamp normally non-conductive during the said charging of the capacitor, the impedance being large enough to maintain the lamp non-conduc tive until the lamp has become deionized but small enough to permit the capacitor to become charged prior to each discharge of the lamp, and means including a grid-controlled discharge tube for controlling the grid of the lamp to initiate the emission of electrons from the cathode.

55. In combination, a capacitor connected with a source of direct current, whereby energy from the source is fed to the capacitor to charge the capacitor, a gaseous-conductoi` lamp provided with an anode, a cathode and a control grid, means connecting the anode with a terminal of the source and a terminal of the capacitor and connecting the cathode with the other terminal of the source and the other terminal of the capacitor to produce, during the said charging of the capacitor from the source, a difference of potential between the cathode and the anode. with the anode positive with respect to the cathode. the pressure of the gas of the lamp being normally of such value that the lamp is normally deionized in order to render the lamp normally non-conductive during the said charging of the capacitor, and means including a grid-controlled discharge tube for controlling the grid of the lamp to initiate the emission of electrons from the cathode.

56. A stroboscope having, in combination, a normally non-conductive gaseous-conductor lamp for producing light ashes of substantial illumination intensity having two electrodes, means for connecting the electrodes to a source of energy to impress between the electrodes from the source a voltage of magnitude insuflicient to produce a current impulse from the source through the lamp between the electrodes when the lamp is non-conductive but sufcient to produce a current impulse from the source through the lamp between the electrodes to produce a light flash when the lamp is conductive, and a trip circuit comprising a discharge device, means for connecting the discharge device to the lamp. means for impressing impulses at a predetermined rate upon the discharge device, means controlled by the discharge device in response to the impulses for producing sudden violent electrical transient impulses at the predetermined rate, and means for transmitting the transient impulses to the lamp to render the lamp suddenly conductive at selected intervals in accordance with the predetermined rate in order to produce current impulses from the source through the lamp between the electrodes at the selected intervals to produce light flashes of substantial illumination intensity at the selected intervals.

57. A stroboscope having, in combination, a normally non-conductive gaseous-conductor lamp for producing light flashes of substantial illumination intensity having two electrodes, means for connecting the electrodes to a source of! energy to impress between the electrodes from the source a voltage of magnitude insufficient to produce a current impulse from the source through the lamp between the electrodes when the lamp is non-conductive but sufcient to produce a current impulse from the source through the lamp between the electrodes to produce a light ash when the lamp is conductive, and a trip circuit comprising a normally non-conductive discharge device, means for connecting the discharge device to the lamp, means for impressing impulses at a predetermined rate upon the discharge device to render the discharge device conductive at the predetermined rate, means controlled by the discharge device upon the discharge device becoming conductive for producing sudden violent electrical transient impulses at the predetermined rate, and means for transmitting the transient impulses to the lamp to render the lamp suddenly conductive at selected intervals in accordance with the predetermined rate in order to produce current impulses from the source through the lamp between the electrodes at the selected intervals to produce light ashes of substantial illumination intensity at the selected intervals.

58. A stroboscope having, in combination, a normally non-conductive gaseous-conductor lamp for producing light flashes of substantial illumination intensity having two electrodes, means for connecting the electrodes to a source of energy to impress between the electrodes from the source a voltage of magnitude insullcient to produce a current impulse from the source through the lamp between the electrodes when the lamp is non-conductive but suicient to produce a current impulse from the source through the lamp between the electrodes to produce a light flash when the lamp is conductive, and a trip circuit comprising a condenser, means for charging the condenser, a discharge device connected between the condenser and the lamp, means for impressing impulses at a predetermined rate upon the discharge device, and means controlled by the discharge device in response to the impulses for causing the condenser to produce sudden violent electrical transient impulses at the predetermined rate for transmission through the discharge device to the lamp to render the lamp suddenly conductive at selected intervals in accordance with the predetermined rate in order to produce current impulses from the source through the lamp between the electrodes at the selected intervals to produce light flashes of substantial illumination intensity at the selected intervals.

59. A stroboscope having, in combination, a normally non-conductive gaseous-conductor lamp for producing light flashes of substantial illumination intensity having two electrodes, means for connecting the electrodes to a source of energy to impress between the electrodes from the source a voltage of magnitude insufficient to produce a current impulse from the source through the lamp between the electrodes when the lamp is non-conductive but sufficient to produce a. current impulse from the source through the lamp between the electrodes to produce a light flash when the lamp is conductive, and a. trip circuit comprising a condenser, means for charging the condenser, a normally non-conductive gaseousdischarge device connected between the condenser and the lamp, means for impressing impulses at a predetermined rate upon the discharge device to render the discharge device conductive at the predetermined rate, and means controlled by the discharge device upon the discharge device becoming conductive for causing the condenser to produce sudden violent electrical transient impulses at the predetermined rate for transmission through the discharge device to the lamp to render the lamp suddenly conductive at selected intervals in accordance with the predetermined rate in order to produce current impulses from the source through the lamp between the electrodes at the selected intervals to produce light flashes of substantial illumination intensity at the selected intervals,

60. A stroboscope having. in combination, a normally non-conductive gaseous-conductor lamp for producing light hashes of substantial illumination intensity having two electrodes, means for connecting the electrodes to a rst source of energy to impress between the electrodes from the source a voltage of magnitude insuiTicient to produce a current; impulse from the source through the lamp between the electrodes when the lamp is non-conductive but sufficient to produce a current impulse from the source through the lamp between the electrodes to produce a light ash when the lamp is conductive. and a trip circuit comprising a discharge device having two principal electrodes and a control electrode, an output circuit connected to the principal electrodes provided with a second source of energy. means for normally maintaining the control electrode at a predetermined potential to maintain the discharge device normally non-conductive, means for modifying the predetermined potential at a predetermined rate to render the discharge device conductive at the predetermined rate in order that the second source of energy may produce sudden violent electrical transient impulses in the output circuit at the predetermined rate, means whereby the normally maintaining means maintains the control electrode at the predetermined potential during times long compared to the duration of the impulses in the output circuit, and means for connecting the output circuit to the lamp to transmit the transient impulses to the lamp to render the lamp suddenly conductive at selected intervals in accordance with the pretedmined rate in order to produce current impulses from the first source through the lamp between the electrodes at the selected intervals to produce light ashes of substantial illumination intensity at the selected intervals.

6l. A stroboscope having. in combination, a normally non-conductive gaseous-conductor lamp for producing light ashes of substantial illumination intensity having two electrodes, means for connecting the electrodes to a first source of energy to impress between the electrodes from the source a voltage of magnitude insufficient to produce a current impulse from the source through the lamp between the eectrodes when the lamp is non-conductive but sufficient to produce a current impulse from the source through the lamp between the electrodes to produce a light flash when the lamp is conductive, and a trip circuit comprising a discharge device having two principal electrodes and a control electrode, an output circuit connected to the principal electrodes provided with a condenser and a second source of energy for charging the condenser, a transformer having a primary winding connected in the cutput circuit and a secondary winding, means for normally maintaining the control electrode at a predetermined potential to maintain the discharge device normally nonconductive, means for modifying the predetermined potential at a predetermined rate to render the discharge device conductive at the predetermined rate in order that the condenser may produce sudden current impulses in the output circuit at the predetermined rate to impress sudden violent electrical transient impulses upon the primary winding at the predetermined rate, means whereby the normally maintaining means maintains the controLelectrode at the predetermined potential during times long compared to the duration oi' the transient impulses. and means for connecting the secondary winding to the lamp to transmit the transient impulses in thc primary winding through the secondary winding to the lamp to render the lamp suddenly conductive at selected intervals in accordance with the predetermined rate in order to produce current impulses irom the rst source through the lamp be tween the electrodes at the selected intervals to produce light flashes of substantial illumination intensity at the selected intervals.

62. A stroboscope having, in combination, a normally non conductive gaseous conductor lamp for producing light flashes of substantial illumination intensity having two electrodes, means for connecting the electrodes to a first source of energy to impress betweenthe eiectrodes from the source a voltage of magnitude insufficient to produce a current impulse from the source through the lamp between the electrodes when the lamp is non-conductive but sufncient to produce a current impulse from the source through the lamp between the electrodes to pro duce a light flash when the lamp is conductive, and a trip circuit comprising a gaseous-discharge device having two principal electrodes and a control electrode, an output circuit connected to the principal electrodes provided with a condenser and a second source of energy for charging the condenser, a transformer having a primary winding connected in the output circuit and a secondary winding, means for normally maintaining the control electrode at a predetermined potential to maintain the discharge device normally non-conductive, means for modifying the predetermined potential at a predetermined rate to render the discharge device conductive at the predetermined rate in order that the condenser may produce sudden current impulses in the output circuit at the predetermined rate to impress sudden violent electrical transient impulses upon the primary winding at the predetermined rate, means whereby the normally maintaining means maintains the control electrode at the predetermined potential during times long compared to the duration of the transient impulses, and means for connecting the secondary winding to the lamp to transmit the transient impulses in the primary winding through the secondary winding to the lamp to render the lamp suddenly conductive at selected intervals in accordance with the predetermined rate in order to produce current impulses from the first source through the lamp between the electrodes at the selected intervals to produce light ashes of substantial illumination intensity at the selected intervals. the gas pressure of the discharge device being such that the control electrode loses control over the discharge device upon the initiation of the production by the condenser of the sudden current impulse in the output circuit.

63. A stroboscope having, in combination, a normally non conductive gaseous conductor lamp for producing light flashes of substantial illumination intensity having two electrodes. a condenser, means for connecting the condenser to the electrodes: means for charging the ccndenser to a voltage of magnitude insuilicient to effect a discharge of the condenser through the lamp between the electrodes when the lamp is non-conductive but sumclent to effect a discharge of the condenser through the lamp between the electrodes to produce alight flash when the lamp is conductive. and a trip circuit com-

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