US2061011A - Circuit arrangement for electrical time control - Google Patents

Description

Nov. 17, 1936. A. w. VINGERHOETS 2,061,011

CIRCUIT ARRANGEMENT FOR ELECTRICAL TIME CONTROL Filed July 10, 1933 2 Sheets-$heet 1 Inven ror ANTONIUS WILHELMUJ VINGERHOET5 A Home;

Nov. 17, 1936. A. w. VINGERHOETS 2,061,011

CIRCUIT ARRANGEMENT FOR ELECTRICAL TIME CONTROL Filed July 10, 1933 28heets-Sheet 2 Invenfor ANTON/US 'WILHELMUJ V/NGERHOETJ Afforn e] Patented Nov. 17, 1936 PATENT OFFICE cmoo'rr aamcsmr roa ELECTRICAL rms CONTROL Antonius Wilhehnns Vlnzerhoets, Eindhoven,

Netherlands, signer, by meme assignments, to N. V. Philips Gloeilampenfabrieken, Eindhoven, Netherlands, a Dutch company Application July 10, 1933, Serial No. 879,311 In Germany July 1932 13 Claims. '(Cl. 250-27) My invention relates to novel circuit arrangements for electrical time control.

My invention broadly applies to circuit arrangements for the electrical control of the duration of processes, and is specially adapted for such control of processes of very short duration.

A special and important application of my invention is in connection with X-ray installations, and specially with short time radiographic exposures, and I shall describe my invention primarily in connection with such use. However, it should be well understood that manifold other applications of my invention may suggest themselves. My invention can be used irrespective whether the process, the duration oi which is to be controlled, is an electrical, other physical, chemical, or other kind of process for example in electric signaling devices, in making photographic prints from negative images, in electrical therapy, etc.

Various means have been suggested for the control of the duration of short time processes and ,also in connection with the taking of short time X-ray exposures. Clock switches, tor instance, have been widely used. Suohswitches after a given time interval may act on a relay or otherwise make or break electrical circuits. Clock switches have, however, various disadvantages, among others, they require the winding of springs, are comparatively expensive, etc.

In view of the inherent drawbacks of such clock switches, various other time control means have been already suggested.

For instance, in "U. S. Patent 1,819,999 to Kears= ley, a timing device has been suggested in which a three electrode tube is used as the time control means, in which tube the grid potential m varied in accordance with the change of voltage of a previously charged condenser.

The potential of the grid thereby varies according to an exponential function between two values, which are so selected that at one value a current may flow through the tube, whereas at the other value the current is suppressed.

The above arrangement has, however. serious drawbacks. As this arrangement requires the pro-charging oi the condenser, in alternating current installation, when the discharge initiated, the condenseris liable to. lose part of its charge before the alternating anode-voltage has assumed a suiliciently high value to effect the discharge through the tube. This requires the use of auxiliary control means, to insure that the discharge of the condenser may only start at a moment when'the anode voltage has assumed a sulficiently positive value.

A further disadvantage is that with the above arrangement special provisions have to be taken to prevent the discharge of the condenser through the grid oi the tube.

also, the arrangement requires the charging of the condenser every time prior to the use of the device, which consumes considerable time in view of the pulsating character of the rectified current used for this purpose and the electrical constants of the charging circuit.

The present invention relates to an arrangement in which all of the above drawbacks are avoided and which arrangement has further important advantages.

According to the invention the potential of a condenser during its charging is used to influence the potential of the auxiliary electrode or grid of a three-electrode discharge tube.

Furthermore, by using the same alternating current source both for the anode voltage of the tubes as well as for the charging of the condenser through a rectifier, and by providing for the proper phase-connections, it is possible accord ing to the invention to have the starting oi the charging oi. the condenser automatically coincide with the starting of a positive half-wave oi the anode voltage.

Various embodiments of my invention are possible. For instance an arrangement can be provided in winch the condenser is charged through a resistance which is connected tothe grid of the discharge tube and affects the potential of same in such a manner that the decreasing voltage drop in the resistance during the charging of the con denser affects the bias of the grid. For instance,

while the charging current is high and the voltage drop in the resistance large, this large voltage drop negatively biases the grid, thereby block ing the discharge current through the tube. As the condenser gradually charges, the voltage drop in the resistance decreases and the grid bias increases until finally a value is obtained at which the discharge through the tube is established. 0r inversely the voltage drop in the resistance may apply a positive bias to the tube which sets in the discharge and the charging of the condenser gradually decreases this positive bias until the current through the tube is blocked.

Again in another embodiment of my invention,'

the potential variations of the charging condenser may he used to directly control the biasing oi the grid of the discharge tube in a somewhat similar manner.

In the first case it is necemary, in the second case it is advantageous to so interconnect the alternating current which supplies the anode potential for the discharge tube and the alternating current used for the charging of the condenser through a half-wave rectifier, that the operative half-waves of the charging current coincide with the positive half-waves of the charging current. Thus the charging of the condenser always starts at the right moment, namely, at that instant when the anode voltage enters its positive or operative phase.

Preferably the same transformer Winding'is used'to supply the anode current as well as the charging current.

Usually I provide a switch in the circuit arrangement by means of which the condenser is normally short-circuited and which switch in another position closes the charging circuit of the condenser. It should be noted that the discharge of the condenser consumes practically no time, as the condenser is directly short-circuited and thus the device is well adapted for quick repeated use.

The invention will be more fully described with reference to the accompanying drawings showing arrangements illustrating various embodiments of my invention and in which:

Figure l is a diagram of an arrangement in which the discharge tube acts as a relay through which normally the current flows, the current being interrupted to control the duration of the process to be controlled and to achieve this the bias of the grid is varied by the voltage drop in a resistance which is connected in series with the charging condenser.

Figs. 2, 3, 4 and 5, show various modifications of my invention, in which the current through the discharge tube is normally suppressed and is only permitted to flow during the control time interval, the bias for the grid being directly af fected by the voltage of the charging condenser.

Referring to Figure 1, a discharge tube I is provided which acts as a relay and which cominterrupt the current through the tube.

prises an incandescible cathode 2, an auxiliary electrode or grid 3 and an anode l.

The discharge tube I, is preferably a gasfilled arc-discharge tube, although a, highvacuum tube may be also employed which, however, should be operated preferably at saturation voltage. As a rule, I prefer to use gas-filled tubes, as high vacuum tubes have the drawback that their anode current varies with the potential applied to the grid.

As is known, as long as the anode potential has a constant value in an arc discharge tube, limited variations of the grid potential do not However, if the anode voltage is an alternating voltage, the arc is interrupted in. each half-wave, and re-ignition of the arc depends on the potential applied to the grid. If during a positive halfwave the potential of the grid is sufliciently high, the tube is ignited and the full current permitted to pass. Thereby, the voltage drop in the tube is of no importance. However, if during a positive half -wave the potential of the auxiliary electrode is but slightly less than that required for the ignition of the tube, the current is altogether interrupted or at least practically suppressed.

A transformer is provided for the energy supply of the arrangement, the primary winding I2 of which is connected to the supply of alternating current, and which transformer has two secondary windings I3 and I4.

The winding I3 supplies the voltage for the anode circuit of the tube I and is connected with its two end terminals 30 and 3i across this circuit. The winding I3 is also provided with two intermediate taps 32 and 33.

Across the portion 36 to 32 of the winding I3 is connected the incandescible cathode 2 of the tube I.

The anode circuit of the discharge tube I comprises a magnet coil I, the armature of which actuates a. contact 8, which serves for either the closing or the opening of a circuit to be controlled, marked X, whichcircuit in turn controls the process, the duration of which it is desired to control. If this process is an X-ray exposure. the contact 6 may serve to close the primary circuit of the high voltage transformer of the X- ray tube. In Fig. 1, the relay 1 is shown as normally energized and the contact 8 normally open, this contact being closed upon the deenergization of the magnet coil 1.

A condenser 5 is provided with one of its electrodes, which as will appear is the negative electrode, in permanent electrical connection at 36 with the grid 3. The other electrode of the condenser 5 is connected to the heel 34 of a twoposition switch I5, the free end of which switch may be brought into contact with either one of the contacts marked I and II, these switch positions being hereafter referred to as positions I and II respectively.

The contact I is connected to the point 36, and while the switch I5 is in position I, the condenser is short-circuited.

When the switch I5 is moved into position II. the charging circuit of the condenser 6 is established. This circuit comprises a half-wave rectifier tube 9-having an incandescible cathode I0 and an anode II-the transformer winding I4, a variable resistance 6, and the condenser 5.

The cathode III of the rectifier 9 is heated from a tapped portion of the winding I4.

Upon closure of the charging circuit, the condenser is gradually charged up by the rectified current, the charging time depending on the electrical constants of the circuit and may be adjusted by varying the resistance 6.

The Junction point 36 of the resistance 6 and of the winding I4, is connected to the tap 33 of the transformer winding I3, thus to a point the potential of which lies between that of the anode and that of the cathode; the other end of the resistance 6 is connected to the junction point 36 and is thus also connected to the auxiliary electrode 3. It will thus appear that while the condenser charges the potential of the auxiliary electrode is rendered less positive, by the extent of the voltage drop in the resistance 6.

As long as the charging circuit is open, the potential of the auxiliary electrode 3 is willciently high to provide for the ignition of tube I during each positive half-wave of its anode voltage.

When the charging circuit is closed, provided the arrangement and connections of the windings are such that the operating half-waves or current flow through the charging circuit coincides with the positive half-waves of the anode voltage of tube I, the potential of the auxiliary electrode will be decreased below the value required for the ignition of the tube I.

This interrupts the current flow in the anode circuit and deenergizes the magnet I, which in the arrangement shown then will cause the contact 8 to close the circuit X controlled by same.

However, with the gradual charging of the condenser 5, the voltage drop in the resistance 6 the auxiliary electrode again assumes a sum-' decreases and the extent'by which this voltage drop reduces the potential of the auxiliary electrode gradually diminishes. After a given time interval, the value of which can be adjusted with great precision and in a simple manner by the proper adjustment of the variable resistance 6,

c'iently positive potential to allow the ignition of the tube I.

The current flow through the anode circuit is thereby reestablished, the magnet coil 1 reenergized and the contact 8 opened.

It is evident that the energization of magnet coil 1 instead of being used to eflect the opening of the contact 8, can be used in an analogous manner to eiIect the closure of a similar circuit control contact.

For the proper adjustment of the duration of the suppression of the anode current, and thus of the closure or opening of the contact 8, besides making the resistance' variable, the capacity of the condenser may also be made adjustable, which makes it possible to obtain a very fine adjustment. Such a circuit arrangement is therefore exceedingly well suited for a time switch for X-ray installations, especially for taking exposures of very short duration, in which case the exact adjustment of the exposure time isof very great importance.

It should be, of course, understood that the magnet switch 1-4 has to be of such character as to respond to the pulsatory current passing through the anode circuit.

Between successive uses, the switch I5 is placed in the position 1, whereby the condenser 5 is short-circuited and loses its charge almost instantaneously.

Insteadof providing a separate transformer winding to supply the charging current, it is also possible to use for this purpose the same winding which feeds the anodeeircuit of the tube I. This is illustrated in Fig. 2, the arrangement of which, however, differs from that of Fig. 1, also in several other respects. While in the arrangement of Fig. 1, the anode circuit I is energized all the time except when suppressed during the charging of the condenser and thus the tube I actsas a normally energized or closed circuit relay, in the arrangement of Fig. 2, the current through tube I is always suppressed except for the duration of the charging of the condenser, thus the tube operates as a normally deenerglzed or "open circuit" relay.

While the discharge circuit of the condenser E and the connections to the junction point" are unaltered in Fig. 2, the other end of the resistance 6 instead of being connected to an intermediate tap of the secondary transformer winding IS-which in this case feeds both the anode circuit of tube I as well as the charging circuitis connected to the anode II of the rectifier tube 9. The cathode III of the tube 9 is connected to the end terminal 40 of the winding I6, close to which a tap 4| is provided, the portion 40 to H of the winding supplying the heating current for the rectifier cathode I0.

The winding It is furthermore provided with two closely spaced taps l2 and ll, which supply the heating current for the cathode 2 of tube I, the tap 42 also serving as the cathode terminal of the anode circuit.

Furthermore, between the tap it and the terminal N of winding it, there is provided a tap II, or to permit adjustment of the voltage pref- -the potential of the cathode tap 42.

erably a plurality of taps-the tap I1 being connected to the contact II of the charging circuit.

grid 3, with which it is in electrical connection,

a charge which gives the grid a negative bias with respect to its cathode 2. As a result, the anode current through the tube I is blocked.

The charging circuit goes through winding I6, rectifier 9, resistance i, condenser 5, switch I5, contact 11, and tap II. It will be noted that in' this arrangement the rectifier is connected to a point of the ,winding, the potential of which is further away from that of the anode 4 than is Thus the charging circuit and the anode circuit are in phase opposition.

When the switch I5 is brought in position II, a voltage is applied to the grid 3, which corresponds to the voltage induced in the winding portion 42-I| and which in the operative haliwave of the anode voltage increases the grid potential above the ignition value. However, as the condenser charges, the potential applied to the grid 3 is gradually reduced, and in a predetermined time interval the grid potential falls below the value required to permit the ignition of the tube. Thus the anode current is interrupted and the contact 8 is actuated.

In this arrangement, the negative electrode of the condenser is connected to the auxiliary elec-' trode 3, the potential thereof being thus directly dependent on the condenser voltage.

It should be noted that the duration of the current through the anode circuit of tube I is not affected by the instantaneous value of the anode voltage at which the switch I5 closes the charging circuit, as the charging of the condenser can only start in the operative half cycle of the anode potential.

The proper adjustment for the duration of the anode current can be obtained by either the adjustment of the resistance 6, or that of the condenser 5 or of the tap II or by a combination of these adjustments.

In'the arrangement of Fig. 2, if energization of coil I should cause the closure of contact 8, a biasing spring 45 serves to hold the contact 8 normally open. When the coil I is energized, the pull of the magnet overcomes the spring 45 and the contact 8 is closed.

Figure 3 shows a further modification of my invention, which gives an arrangement similar to that of Fig. 2 except for the provision of a threeposition instead of a two-position switch and the addition of a resistance 20 connected across a portion of the winding I6.

The switch l8 contacts with a segment I9 in the positions I and III, the segment Iii being connected to the junction point 35. In position I, the switch short-circuits the condenser 5 in the same manner as in the previous figures.

In position II, the switch establishes the charging circuit of the condenser in the same manner as in Fig. 2, except that contact II instead of being connected to a tap of the winding I6 is vides for a more convenient variation of the bias voltage to be applied to grid 3.

Preferably, the resistance 20 is shunted across a portion oi the winding l6, which portion extends on both sides of the taps 42 and 42 for the cathode 2. Thereby, it is made possible, to better adapt the bias voltage to the characteristic of the tube I, and it required, the tube may be operated without grid bias, or with negative grid bias.

In the position III, the condenser remains short-circuited, but the contact III, being connected to the movable contact 2|, the grid is kept continuously at a sufllciently high potential to maintain the ignition of tube l. Thus, a current is maintained in the anode circuit as long as the switch is kept in position III.

The arrangement shown in Fig. 3 thus permits to eil'ect either a short time control of predetermined duration or may perpetuate a desired condition. For instance, when applied to X-ray installations, the arrangement may be used both for short radiographic exposures and for continuous fluoroscopic work. In such case, I prefer to combine with the switch ll other regulating means which upon movement of the switch into the positions II and III respectively, cause the establishing of the proper 'voltage and current values of the X-ray for radiographic and fluoroscopic work respectively.

The arrangement of Fig. 4 is similar to that oi Fig. 2, except for the following. A separate winding 22 is used ior'the heating of the cathode 2 oi tube I, the contact 11 is connected to the winding 22 instead of to the tap l1, whereas the latter is connected to the heel 34 of the switch ii.

In this arrangement, the anode circuit oi tube l is altogether interrupted, until the charging circuit is closed when the switch I! takes the position II. This arrangement has the advantage that undesired ignition of the relay tube i is avoided even if-due to some uncontrollable circumstances, for instance, due to extraneous reasons-a high voltage impulse is induced in the anode circuit which otherwise might ignite the tube in spite of the sub-ignition potential applied to the grid.

In this arrangement the charging of the condenser starts as soon as the switch leaves the contact I, whereas the anode circuit only closes when the switch has contacted with II.

In the arrangement of the Figures 2 to 4 the drawback may occur that the end of the time interval during which the switch I should remain closed is not exactly defined and that current impulses which, due to the lower grid potential, start at a later phase, become transitory, so that the switch 8 instead of being positively actuated is caused to chatter over a plurality of cycles.

This drawback is entirely avoided and the advantages of the arrangement 01 Fig. 4 maintained by the arrangement shown in Fig. 5.

In this arrangement, the cathode 2 is again connected to the winding l6, whereas the electrode oi the condenser 5 is connected to the tap i1, similarly to Fig. 4.

The switch I5 is omitted, and the armature of magnet coil I is provided with two additional contacts 23 and 24. Furthermore, there is provided in the anode circuit a manually operable switch 25. The contact 23 is adapted to shortcircuit the condenser 5, whereas the contact 24 is in multiple with the switch 25 and serves as a stick contact for the magnet I.

- As long as the switch 25 is kept open the anode circuit is interrupted and the spring biased armature of magnet coil I is in its upper position, whereby contact 22 short-circuits the condenser, whereas contacts 24 and I are open.

When switch 25 is closed, the anode circuit is immediately established as the grid 3 assumes simultaneously with anode 4 a positive potential, coil 1 is now energized and breaks contact 23 and makes contact 24 and 8. The switch 25 may be now released as contact 24 retains the anode circuit closed.

The condenser 5 being no more short-circuited charges up in the same manner as described in connection with Fig. 2 and after having charged to a given value causes a drop of the grid potential, thereby interrupting the anode current and deenergizing the relay coil I. Once the anode current is interrupted the magnet I cannot be re-energized and the chattering of the contact 4 is thus prevented.

It should be noted that in this arrangement the short-circuiting and discharging of the condenser takes place automatically.

To insure that the contact 24 be closed before the manual switch 25 is opened, the later is preferably designed as an automatically opening switch provided with sufllcient delay to insure the closure of the anode circuit until the magnet coil 1 has attracted its armature.

The automatic opening of the switch 25 is also desirable to prevent the prolonged closure of this switch which otherwise might again cause chattering of contact 4, due to the fact that after the magnet controlled switch has returned 'to its normal position and the condenser partly discharged closure of the switch 25 would re-establish the anode current.

In a specific embodiment used for controlling X-ray exposures, where the relay contact 24 required .05 second for its closure (after the switch 25 has been closed) and with a required minimum exposure time of .1 second, the automatic closure time of the switch 25 was selected to be .07 second. Or generally the time of closure effected by the switch 25 has to be larger than the time required for the closure of switch 24 and smaller than the minimum time during which the condition effected by contact 8 should persist.

As there are various known switch constructions suitable for this purpose and no novelty is claimed for this switch per se, its detailed description and illustration is not believed to be necessary.

It might be mentioned that a suitable construction for this switch is the one used in automatic telephone apparatus, which comprises a rotary disc which upon manual displacement is returned by a biasing spring at a fixed speed and during such return establishes and breaks certain circuit connections.

As stated, instead oi using a gas-filled discharge tube for the relay tube I, a high vacuum electron discharge tube may be used. In this case, the lowering of the grid potential instead of suppressing the ignition of the discharge tube, cuts oil the current flow through the tube.

While I have described my invention in connection with certain embodiments and in certain applications, I do not wish to be limited to such embodiments and applications, but desire the appended claims to be construed as broadly as permissible in view of the prior art.

What I claim is:

- 1. A circuit arrangement for automatically with said auxiliary electrode, a transformer winding to supply the current to the tube circult and to the charging circuit, a potentiometer connected across a portion of said winding and a switching device to connect the movable contact of said potentiometer to the other electrode of the condenser for the charging of said condenser.

2. A circuit arrangement for automatically limiting the duration 01' an electrically controlled process, comprising a discharge tube having a cathode, an anode and an auxiliary electrode, an anode circuit for said discharge tube and an alternating current supply for said circuit, a condenser and a charging circuit for same, means to apply a potential to the grid which is sumcientlyhigh to permit the current flow through said anode circuit during the positive half-wave of said alternating current, and a three-position switch which in one of its positions shortcircuits said condenser and in its second position applies said potential to the auxiliary electrode, and in its third position shortcircuits said condenser and simultaneously applies said potential to the auxiliary electrode.

3. A circuit arrangement for automatically limiting the duration of an electrically-controlled process, comprising an arc discharge tube having a cathode, an anode, and an auxiliary electrode, a condenser and a charging circuit therefor, an anode circuit for said discharge tube including electro-responsive means, and a twoposition switching device having a normal position in which it interrupts the anode circuit at a point outside the tube and a second position in which it establishes said anode circuit and initiates charging of said condenser, said condenser during the charging thereof impressing upon said auxiliary electrode a varying potential which after a predetermined time interval assumes a value at which current in the anode circuit is suppressed and said electro-responsive means is deenergized to cause interruption of the process.

4. A circuit arrangement for switching on an electric current and automatically limiting the duration thereof, comprising a transformer having a primary winding, a secondary winding and a tertiary winding, a gas-filled electric discharge tube having a filamentary cathode, an anode and an auxiliary electrode adapted to control the starting of the discharge of the said tube, said cathode being connected to said tertiary winding so as to be energized thereby, a second discharge tube having a filamentary. cathode which is energized from a portion oi! said secondary winding and an anode, a variable resistance connecting said latter anode. and said auxiliary electrode, an electromagnetica iy actuated relay switch having a magnet coil, the anode of said first discharge tube being connected through said coil to said secondary winding, said secondary winding having an intermediate tap between the connection to the anode of said first discharge tube and the connection to the cathode of said second discharge tube and a condenser connected between said auxiliary electrode and said tap, a two-way switch connecting said tap in one position to the cathode of said first discharge tube and in a second position to said auxiliary electrode, thereby short circuiting said condenser.

5. A circuit arrangement for switching on an electric current during a predetermined time, comprising a transformer having a primary wind ing, a gas-filled electric discharge tube having a filamentary cathode, an anode and an auxiliary electrode adapted to control the starting of the discharge in saidtube, said cathode being connected over a portion of said secondary winding so as to be energized therefrom, a relay switch actuated by a magnet coil which is connected in series with a manually actuated switch between said anode and one point of said secondary winding, a tap intermediate between said point and said portion of the secondary winding and a condenser connected between said tap and said auxiliary electrode, said auxiliary electrode being further connected through a variable resistance and a second electric discharge tube having an anode and a filamentary cathode to a point of said secondary winding in opposite phase as said first point oi. this winding with respect to the portion energizing the cathode of said first tube, said second discharge tubebeing connected with its anode turned to the auxiliary electrode of said first tube and its cathode turned to the secondary winding, said relay switch comprising three circuit breakers one of which is normally closed and short-circuits said condenser, the second of which is normally open and forms a stick contact for the said coil and the third of which controls the current to be switched on by the circuit arrangement during a predetermined time.

6. In a timing device, an arc discharge tube having an anode, a cathode and a control electrode, a normally open anode circuit for said tube, means to gradually vary the control electrode potential from a definite value which is positive with respect to the cathode and makes the tube conductive to a lower value which makes the tube non-conductive, said means comprising an electrical condenser and a normally inoperative charging circuit therefor, and switching means connected to said two circuits to simultaneously switch on the charging current through said condenser and close the anode circuit at a point outside the discharge tube. a

'7. In a timing device, an arc discharge tube having an anode, a cathode and a control electrode, an anode circuit for said tube having an interruption outside said tube, 'a second circuit comprising an electrical condenser and means to normally maintain saidcondenser discharged, a transformer winding common to said two circults and having a variable intermediate tap, a

rectifier in said second circuit having its negative side connected to said winding on one side of control electrode in said path, a condenser having one electrode connected to said control electrode, an anode circuit for said tube including the discharge path and current responsive means, a charging circuit for said condenser and including same, a heating current circuit for energizing said cathode and including same, said circuits having common portions, and switching means connected to said charging circuit and to a point of said anode circuit outside said discharge path to selectively make said charging circuit operative or inoperative and to establish said anode circuit whensaid charging circuit is made operative. 9. In combination, an electric discharge device having an anode, a cathode and a control electrode, means for supplying anode current to said tube, means for applying to the control electrode a potential of such value as to render said discharge device normally conductive, means comprising a condenser to vary the potential of said control electrode between said value and a second value at which the tube is non-conductive, and means for switching on the condenser to gradually change the potential oi! the control electrode from the first value to the second value and for simultaneously establishing the connections to permit the flow o! anode current.

10. In combination an electric discharge device having an anode, a cathode and a control electrode, a rectifier having a cathode and an anode, a series circuit including said condenser and said rectifier, a point in said circuit between said condenser and said rectifier being connected to said control electrode, means for supplying an alternating electromotive force to said circuit and between the anode and cathode of said discharge device, and a circuit arrangement including a two-position switching device, said switch in one position permitting the application oi! electromotive iorce to said rectifier and condenser and between the anode and cathode of said discharge device, said switching device in its other position preventing the application of electromotive force to said condenser and between the anode andcathode of said discharge tube.

11. In a timing device an arc discharge tube having an anode, a cathode and a control electrode, a transformer winding having an intermediate tap, an anode circuit for said tube comprising a magnetic relay coil and a portion of said winding to one side of said tap, a series circuit comprising a rectifier, a variable resistance,

a condenser, and a portion of said winding at the other side 0! said tap, and a two-position switch included in the connection from the cathode of the tube to said winding, said switch in one position establishing said anode circuit and in the other position interrupting the anode circuit at a point outside the discharge tube and shortcircuiting said condenser.

12. In a timing device, an arc discharge tube anode of said tube and a point on said winding at the other side of said tap, and a two-position switching device which in one position connects said tap to said cathode to establish the anode circuit of said tube and in its other position disconnects the tap from the cathode to interrupt the anode circuit and connects same to the control electrode to short-circuit the condenser.

13. In a timing device, an arc discharge tube having an anode, a cathode and a control electrode, a source of alternating current comprising a winding having an intermediate tap, a condenser connected between said control electrode and said tap, a rectifier having an anode connected through a resistance to said control electrode and a cathode, an open circuit relay switch having a coil connected with one end to a point on said winding on the other side of said tap and with its other end connected through said switch to the anode of said are discharge tube, a second switch connected in multiple with said condenser and interconnected with said first switch, said second switch being closed when saidfirst switch is open and being open when said first switch is closed, and an auxiliary switch connected in parallel with said first switch.

ANTONIUS WILHELMUS VINGERHOEIS.

Images