US2806186A - Relay adjusting set - Google Patents

Description

Sept 10, 1957 RELAY ADJUSTING SET Filed March 24, 1954 DE'MA GWET/ZA T/ON mu TIA 1. MANUA L) 6 Sheets-Sheet 1 FINAL :TEPs (AUTOMATIC) OPERATE 0 I04 E'LECT'ROMAGNETS CONT/P01- SELECTOR) /0/ FIXTURE) l0? POWER c pc r PULSE; J'W/TCHES) //0 /09 /05 /07 O RELEASE F PmMAAIEA/T l05 MAGNETS OPERATE- RELEASE cavmq. I00 7'55 T-DEMAGNET/ZAT/ON CONTROL R523) 0P UND ADJUSTMENT RELEASE d TEST COIL CURRENT RESE T RELAY CURRENT ADJUSTMENTS FIG. 2

FIG. 6 FIG. 7

POLL/1 RD, JR. W

ATTORNEY p 1957 J. T. L. BROWN ETAL 2,806,136

RELAY ADJUSTING SET 6 Sheets-Sheet 2 Filed March 24, 1954 TEST VA L UES ADJUSTMENT SEQUENCE OPERATE SENS/77W TV FIG. 5

kOPE/PA TE VALUES \TEST VALUES L RELEASE VALUES ADJUSTMENT SEQUENCE INVENTORS J. 7.'L.- BROWN By C. E. POLL/4RD, JR

ATTORNEY Sept 10, 1957 T. L. BROWN ETAL 2,806,186

RELAY ADJUSTING SET 6 Sheets-Sheet 3 Filed March 24, 1954 J. m. BROWN 271 c. E. POLL/1R0, JR.

p 1957 J. T. L. BROWN ETAL 2,896,186

RELAY ADJUSTING SET 6 Sheets-Sheet 4 Filed March 24 1954 A T TORNE V Sept 1957 J. T. L. BROWN ETAL 2,806,186

RELAY ADJUSTING SET QM L. BROWN 6 Sheets-Sheet 5 FIL IL Filed March 24, 1954 POLL/1RD, JR.

A 7TORNE V p 1957 J. T. L. BROWN ETAL 2,80

RELAY ADJUSTING SET 6 Sheets-Sheet 6 R0, JR.

BROWN POLLA Filed March 24, 1954 A T TORNE Y United States Patent RELAY ADJUSTING SET John T. L. Brown, Short Hills, and Charles E. Pollard,

Jr., Hoholrus, N. J., assignors to Bell Telephone Laboratories, Incorporated, New York, N. i2, corporation New York Application March 24, 1954, Serial No. 418,412 12 Claims. (Cl. 317-157) This invention relates generally to relay test circuits and more particularly to a test set for automatically testing and adjusting the permanent magnet bias of polar relays having permanent magnet polarization or bias affecting the armature movement thereof in addition to the usual energizing means such as a coil or coils.

Specifically, the present invention relates to a circuit for automatically adjusting the permanent magnet 'bias of a relay which includes an energizing winding and at least one contact and a permanent magnet and a magnetic armature movable in operable relation to said contact under the influence of the combination of the magnetic field produced by energization of said winding and the magnetic field of said magnet.

An object of the invention is to improve the art of adjusting such relays.

A particular object of the invention is to improve the means whereby the adjustments of interest are made to a polar relay of the totally enclosed type, which, due to its sealed construction, precludes the usual manual adjustment familiar to the art.

The general method employed is disclosed and claimed in Patent 2,590,228 to J. T. L. Brown of March 25, 1952. This method is described therein as used, by way of example, to adjust the magnetic bias of a polar relay of the sealed, mercury type, such as is shown in Patent 2,609,464 to J. T. L. Brown and C. E. Pollard, Jr. of September 2, 1952, and which has a movable armature arranged to make contact with either of two contacts and all sealed in a glass envelope containing mercury fed by capillary action to the contact areas and which has a permanent magnet attached to each contact outside of the envelope and an energizing coil surrounding the envelope. This relay is also described, along with its characteristics and performance, etc., in an article Balanced polar mercury contact relay, by l. T. L. Brown and C. E. Pollard, in the November 1953 issue of The Bell System Technical Journal.

Another type of relay which can be adjusted by means of the present invention and according to the method of the Brown patent is the type of relay shown in Patent 2,577,602 to E. T. Burton of December 4, 1951, which, again, is a sealed, mercury type of polar relay but which has only one magnet biasing only one set of the contacts with which the armature cooperates.

It will be appreciated by those skilled in the art that many other types of relays may be adjusted by means of the present invention and that the above are merely exemplary.

These polar relays are magnetically polarized in order that a specified magnitude and polarity of current in the energizing winding will cause the armature to move from one contact to the other. The two directions of motion are commonly referred to as the operate and the release directions, and this terminology will be used throughout subsequent discussion, description, specifica tion and, where necessary, claims. The magnitude and/ or polarity of current to do either job may be anything .of the invention provide means for 2,806,186 Patented Sept. 10, 1957 desired, within the capabilities of the relay structure of course. The current or currents specified for a particular relay are generally referred to as the operate and release sensitivities of the particular relay in question. The main purpose of the present invention is to effect automatically, quickly and accurately any desired such sensitivity value or values for a particular relay.

The general steps of the method employed, as set forth in the Brown patent and in the Brown-Pollard article, are as follows in order to adjust a balanced polar relay (magnetic bias on both contacts) to any desired pair of sensitivity values:

1. Magnetize the two magnets fully by a flux directly across them.

2. With the armature starting from one side, progressively decrease the magnetization on that side in small steps until the armature just operates to the other side on the final current value desired for this direction of operation (which may be the operate direction).

3. With the armature starting on the other side, progressively decrease the magnetization on that side in small steps until the armature just operates from that 'side on the final current value desired for this second direction of operation (which may be the release direction) Burton patent and having only one magnet, the procedure would presumably be complete after step 2.

In the disclosed embodiments of the present invention,

means are provided for performing step 1 by manual manipulation of circuit means. Steps 2, 3 and 4 are thereafter performed by the circuit automatically in response to a manual manipulation which amounts to a start signal. In more detail, the disclosed embodiments performing the above method steps as follows:

1. By the manipulation of a switch to a magnetizing position, a relay circuit applies a selected polarity of halfcycle alternating current as magnetizing pulses to electro magnets, which pulses thereby over-magnetize both of the bias magnets of the relay.

2. By the manipulation of said switch to a demag netizing position, the relay circuit selects the other polarity of half-cycle alternating current to be applied to one electromagnet at a time thereby to demagnetize one or the other of the bias magnets at one time under the control of a relay control circuit and a selector. This control circuit causes the test relay armature to operate .to one side, say the operate side, applies a test current to the relay, applies a relatively low demagnetizing pulse of specified magnitude of the selected half cycle as determined by the selector to the associated electromagnet, applies a reset current to the test relay to force the armature to operate to the said one side, applies a test current to said test relay and detects whether or not the armature of the test relay moves to the other side in response to said test current. If the armature does not so move, then the control circuit causes the selector to preselect a slightly larger magnitude of demagnetizing current and applies this slightly larger demagnetizing pulse to the associated electromagnet and then repeats the rest of the above procedure. If the armature does move, then the control circuit will adjust itself to be able to go through the same procedure on the other side, say the release side, using the other 3 electromagnet, of course, and starting the magnitude of demagnetizing pulses at a specified low value of demagnetizing current as before.

3. At the completion of a'demagnetization cycle on the release side, the control circuit will switch to the operate side and continue again because the adjustment of the release side will have caused an error in the previous operate side adjustment.

4. This procedure is continued back and forth on the operate and release sides until the detecting means in the relay control circuit indicates (such as by the rapid alternate flashing of two lamps associated with each side of. the relay) that the armature travels in the right direction upon the proper sensitivity or test current being applied respectively to the test relay winding.

A feature of the present invention is the provision of a circuit for automatically adjusting the permanent magnet bias of a relay of the general type referred to herein.

A particular feature of the present invention is the provision of the necessary relay control circuits, current or voltage selector means, and predetermined test current value source or sources whereby the above adjust ment procedure is performed automatically.

The invention is described in the following detailed description as embodied in exemplary circuitry shown on the drawings of which the following are general descriptions:

Fig. 1 shows in block diagram form a functional layout of a typical adjusting set arranged for demagnetization;

Fig. 2 illustrates how to arrange Figs. 6 and 7 to disclose a complete circuit according to one embodiment of the invention;

Fig. 3 illustrates how to arrange Figs. 8 and 9 to disclose a complete circuit according to another embodiment of the invention;

Fig. 4 shows a curve or graph or plot of test data applicable to the circuit of Figs. 6 and 7, which showing is referred to in the detailed description as an aid to understanding the functioning of the circuit of Figs. 6 and 7.

Fig. 5 shows data similar to that of Fig. 4 but associated with the circuit of Figs. 8 and 9;

Figs. 6 and 7 disclose the details of one complete embodiment; and

Figs. 8 and 9 disclose the details of another complete embodiment.

Fig. 1 shows a functional block diagram layout of an automatic relay adjusting set embodying the present in- -as 101 and 102. A control circuit 103 is arranged to select under certain circumstances specified polarities of half-cycle pulses of the alternating-current power and to apply these over the operate or the release path through respective initial and final steps of power magnitude selector 104, 105, 106 and 1'07 to one or both of the electromagnets 101 and 102. The control circuit 103 also, at certain times, exercises an operate-release control and a test reset control over the operation of the test circuit in cooperation with certain test relay current adjustment circuits which apply predetermined test and reset current values for the operate and release directions of motion of the armature 168 of relay 100.

Briefly, the operation of the circuit is as follows. Assuming that the release direction of motion of the armature 103 is from contact 109 to contact 110 and that the operate direction is the reverse and assuming that the armature of relay 100 is initially in contact with the operate contact 110, the relay current adjustment circuits are first set such'that when an operate or release test 4 v or reset current is desired to be transmitted through the coil 111 of relay 104 these values will be those which are specified for the relay under adjustment. The selector switches 105 and 1117, comprising a fine adjustment, will be set at their minimum voltage values. The variacs 164 and 106, comprising the coarse adjustment, will be set at some predetermined relatively high value of voltage output. In response to the operation of a manual switch, the power control circuit 193 will apply to both of the electromagnets 1111 and 162 a few half cycles of specified polarity (say the positive half cycles) of the alternating-current power, whereby each of the relay contacts comprising permanent magnets 199 and 116 is overmagnetized. Thereafter, the coarse controls 1114 and 196 are manually readjusted to a selected minimum voltage position and the control circuit 103 will select the variac 166, the selector switch 163'] and the electromagnet 101, and will cause relatively low level reverse polarity halfcycle pulses of demagnetizing current to he applied to the electromagnet 161 for the purpose of partially demagnetizing the magnet contact 111 of relay 1%. While this particular half cycle of demagnetizing current is being applied to the electromagnet 1111, the release reset current value will be applied to the winding 111 of relay 1% to insure that the armature 1158 remains in contact with the operate contact magnet 11%. As soon as this half-cycle demagnetizing pulse is finished, the control circuit 103 will cause the release test current value to be applied to the winding 111 to determine whether or not the armature 1133 will transfer from contact 119 to contact 109. Normally, in response to the first demagnetizing pulse, the armature 1% will not perform as required, whereupon the control circuit 193 causes the release power selector to adjust itself to a slightly increased amount of demagnetizing voltage and to apply this increased demagnetizing voltage again to the electromagnet 101 simultaneously with the previously-mentioned value of release reset current being applied to the winding-111. As soon as this second demagnetizing pulse is finished, the release test current is again applied to the winding 111. This procedure is repeated until such time as the armature 108 will travel from the operate contact magnet 110 to the release contact magnet 1119 as an indication that the magnet 119 has been demagnetized to a sufiicient extent to permit the armature 1113 to travel to the release contact 109 in response to the predetermined value of release test current.

The control circuit 1113 detects the travel of the armature 108 from the operate contact 119 to the release contact 109 in response to the preselected value of release test current. Thereupon the control circuit 103 switches its power control from the release to the operate side thereby enabling the variac and selector to apply demagnetizing pulses only to the electromagnet 1132. The above procedure, whereby successively increasing increments of half-cycle demagnetizing pulses are applied to electromagnet 1191, is repeated with respect to electromagnet 162 except that the reset and test relay current adjustment circuits which are used are the operate values instead of the release values. Sooner or later the armature 108 will move in response to the operate test current from the release contact magnet 199 overvto the operate contact magnet 11%) as an indication that the mag- The last-mentioned adjustment of the magnet 1% race essarily causes an error in the previous adjustment of the magnet 1113 because of their proximityand their joint influence over the action of the armature 1118. it is,- therefore, necessary, upon the movement of the armature 108 from the release contact 1199 to the operate :coritact 111 to again repeat the demagnetizing procedure with respect to the magnet 11%.

This process continues back and forth until the control circuit 103 detects that the adjustment of the two mag- ; ne'ts 109 and 110 is relatively close to the desired final without any further demagnetization.

adjustments with respect to their starting condition, and

thereupon may, according to one embodiment of the invention, bring into play the fine adjustment selector switches 105 and 107 to the exclusion of the coarse adjustments comprising the variacs 104 and 106. Thereupon, under the control of the fine adjustments, the testing set proceeds to a conclusion whereby each of the magnets 109 and IE is successively and alternatively adjusted until the armature 108 buzzes back and forth from contact 109 to contact 110, and vice versa, immediately in response to the application to the winding 111 of the respective operate and release test current values Thi represents a condition, as detected by the control circuit 103, indicating that the relay 100 has been properly adjusted and that the test is completed.

Thereafter, another relay may be placed in the electromagnet fixture and the selector switches or variacs reset to their starting position and a new test procedure followed.

Fig. 4 illustrates in a general manner what happens during the various adjustment sequences according to the embodiment of the invention wherein a shift is provided between coarse and fine power control which is in the embodiment of Figs. 6 and 7. At sequence 0, the release sensitivity and the operate sensitivity of the test relay are respectively 20 ampere turns and +43 ampere turns. This represents the condition of over-magnetization of both magnets prior to the demagnetizing procedure.

The first series of adjustments, whereby the magnet 110 (the operate magnet contact) is demagnetized until the armature moves to the release contact 109 in response to the preselected value of release test current, places the relay under test in a condition where the respective release and operate sensitivities are +10 and +82 ampere turns. Thereupon, an adjustment sequence is effected upon the operate contact magnet 109, at'the conclusion of which the respective release and operate sensitivities are +3 and +56.

Thereafter, the circuit alternatively causes an adjustment sequence to the release and to the operate sides. At the "inth adjustment sequence time the release sensitivity of the relay is +30 and the operate sensitivity is +47, these being assumed as the final adjustment sensitivities of the relay.

Somewhere, approximately in the neighborhood of the fourth or fifth or sixth sequence, the circuit will automatically shift from coarse to fine adjustment.

Fig. is an illustration of what happens during the various adjustment sequences of a test circuit according to another embodiment of the invention, such as disclosed in Figs. 8 and 9, wherein there is no shift from a coarse .to a fine power adjustment, but wherein the entire pro- :cedure is controlled under a fine adjustment situation.

tact magnet being operated upon to its respective test value. Each time, however, due to the interaction of 'the two magnets, the successive adjustments of opposite sides will upset the previous adjustment of the other side. Eventually, however, as was the case in Fig. 4, the final adjustment at approximately adjustment sequence time nine will approach the desired final test values.

In Figs. 4 and 5 it will be appreciated that each of the lines on the curves marked with a black arrow represents one entire adjustment sequence on the particular release or operated side, as indicated, and that each one of these adjustment sequences may involve any number of separate consecutive demagnetizing pulses and reset and test current tests for that side. Figs. 4 and 5 merely represent what the release and operate sensitivities of a test .relay would be if taken out of the test set and checked to ascertain what these sensitivities are at the end of each adjustment sequence. Of course, the test setembodying the present invention does not actually provide ampere turn sensitivity values for the relay at these specific times, but continues with the automatic adjustment sequences until such time as the relay under test buzzes to and from the operate and release contacts in rapid sequence under the control of the respective operate and release test currents, without the necessity of any further demagnetization.

In the embodiment of Figs. 6 and 7 the relay I in Fig. 7 is the relay under test and is shown as including an armature 718, an energizing winding 719, an operate contact 716 with an associated permanent magnet 717 and a release contact 714 with an associated permanent magnet 715. Located adjacent to the respective magnets 717 and 715 are the magnetizing-demagnetizing coils 713 and 712. The armature 718 of the relay under test, relay I, is shown in contact with the release contact 714. The armature 718 of this type of relay will be in contact with one or the other of its contacts 714 and 716 and the showing of armature 718 in contact with the release contact 714 is merely illustrative of a suitable starting position.

With the double-pole double-throw switch 723 in one or the other of its two positions and with switch 724 open, a circuit is completed from the voltage divider comprising resistance 721 and 722 across the battery, into switch 723 through milliammeter 725, out of switch 723, through the secondary of transformer 726, the winding 719 of relay 1, contact 1 of relay H, contact 1 of relay C to potentiometer 702 comprising part of a voltage divider including potentiometer 702 and resistance 703 across a battery.

By observing the milliammeter 725 and by adjusting the potentiometer 702, the predetermined desired value of operate test current may be set up by potentiometer 702. By operating switch 720 to the reset position, relay H will be operated in a circuit extending from ground over switch 720 and through the winding of relay H to negative battery. This switches the circuit of the winding 719 of relay I to extend over contact 2 of relay H and contact 1 of relay D to potentiometer 705 which comprises part of a voltage divider including resistance 704 in series with potentiometer 705 across a battery. By moving the double-pole double-throw switch 723 to the proper position and by adjusting potentiometer 705, the preselected value of operate reset current may be adjusted.

Leaving switch 720 in the reset position and operating switch 737 to the release position holds relay H operated and operates relays N and K of Fig. 6 and relays B, C and D of Fig. 7. The operation of relays N, K and B are not significant at the moment. Relays C and D are operated in a circuit extending from ground over switch 737, conductor 638 through the windings of relays C and D in parallel to negative battery, whereupon relays C and D operate. With the switch 723 in the appropriate position, a circuit is now completed through the milliammeter 725 and the secondary of transformer 726, the winding 719 of relay I, contact 2 of relay H and contact 2 of relay D to the potentiometer 709 comprising part of the voltage divider, including resistance 707 and potentiometer 709 across battery. By observing the milliammeter 725 and by adjusting potentiometer 709, the preselected value of release reset current may be properly set up.

By maintaining switch 737 in its release position and moving switch 720 back to its test position, relay H will be released, whereupon the previously described circuit through the winding 719 of relay I is switched over contact 1 of relay H and contact 2 of relay C to the potentiometer 708, by means of the adjustment of which the release test value of current may be set up, at the conclusion of which switch 720 may be momentarily placed in its reset position to apply the release reset value of current to the winding 719 to insure that the armature 718 thereof ends up in contact with the release contact 714. Thereupon, switches 737 and 720 may be returned to their respective operate and test positions leaving the armature 718 in the position shown in Fig. 7.

To place the circuit in condition for automatic operation, switch 724 is closed to short circuit the meter 725 and switches 737 and 720 are placed in their respective run positions. In'this condition, all relays in the circuit of Figs. 6 and 7 are in the conditions as shown.

In Fig. 6, upon the closure of switch 614, the alternatingcurrent source of power 633 is applied over the two bus bars marked 1 and I which extend to the similarly marked terminalsof the variacs 604 and 609,'to the primaries of transformers 612 and 613 and to potentiometers 610 and 611. The manual adjustment knobs, such as 605 for variac 604, may be moved to adjust the variacs and potentiometers 604, 609, 610 and 611 to their minimum voltage positions corresponding with phase 5 This manual adjustment is permitted by virtue of the fact that the magnetic clutch arrangements, such as comprising the electromagnet 603 and the friction clutch 602 associated with the variac 604, are not energized.

With these various initial settings of the coarse and fine power selection controls for the operate and release sides, it will be noted that the wiper of the variac 609 carries zero voltage with respect to phase 6, and applies it to the I terminal of the potentiometer 611, whereupon the wiper. of potentiometer 611 carries zero voltage with respect to hand applies it over conductor 636 into Fig. 7 to the right side of the 'elect romagne t 713, the left side of the magnet of winding 713 extending back to contact 2 of relay B. Similarly, in Fig. 6, the Wiper of variac 604 carries zero voltage with respect to 1, and applies it to the 6, terminal of the potentiometer 610, whereby the wiper of potentiometer 610 carries zero voltage with respect to 6 and applies it over conductor 635 into Fig. 7 to the left side of the winding of electromagnet 712, the right side of the winding thereof extending back to contact 1 of relay B.

In Fig. 6, the a, phase of the alternating-current power bus extends through resistance 634 and over conductor 637 into Fig. 7 to the contact of relay A. it will, therefore, be apparent that, when relay A is operated, the 6, phase of the alternating-current power will be applied from conductor 637 over the contact of relay A to the armature of relay B, whereupon, depending upon whether relay B is released or operated, the 1 phase will extend over contact 1 or Z'thereof and through the respective electromagnet 712 or 713 to conductor 636 or 636, ex-

tending back into Fig. 6 to the coarse and fine power selector controls associated with the respective electromagnets 712 and 713, namely, the operate and release controls. It will further be appreciated that Whatever increment of power may have been selected by the power control circuit of Fig. 6 with respect to phase 13 will thereupon be applied over conductor 635 or 636 to the associated magnetizin -demagnetizing electromagnet 712 In Pi g. 6 the directions of increasing increments of power with respect to phase I are indicated by arrows associated with the wipers of the variacs and potentiometers comprising the coarse and line power increment selection means.

The first operation in initiating the relay adjustment cycle is a preselected manual setting of the wiper of variac 604 by means of the knob 605 to a position which represents a substantial amount of alternating-current voltage on the wiper ofvariac 604 with respect to its a, terminal. A similar setting is made of the variac 669. This, then, will apply this amount of aiternating-current power to conductors 635 and 636 extending into Fig. 7 through the electromagnets 712 and 713 back to the contacts 1 and 2 of relay B, one or the other of which will extend to the armature of relay A.

The magnetize-demagnetize switch 615 will now be "operated to its upper or magnetize position, causing a numberof things to happen as follows:

of relay B. This, as will be appreciated, places the electromagnets 712 and 713 in parallel between their respective power source conductors 635 and 636 and the contact 1 of relay B which, when relay A is operated, will extend back over conductor 637 into Fig. 6 and through resistance 634 back to the I phase of the alternatingcurrent power source.

2. With the switch 615 in its upper or magnetizing position, phase 6, of the alternating-current power source 633 is extended over the left inner blade of switch 615 to the swinger armature of relay L, to the winding of relay K, to the primary windings of transformers 623 and 624, to the winding of relay N, and over conductor 638 into Fig. 7 to the windings of relays B, C and D. The only significant connections in this respect are that phase 6, is connected to transformers 623 and 624 and to the swinger armature of relay L.

3. A circuit is completed from phase i on the armature of relay L, over contact 2 of relay L, conductor 642 into Fig. 7 through the potentiometer 727 to phase 1 on the conductor 639 extending back into Fig. 6. No alternating-current power is, therefore, applied to the transformer 726 when the switch 615 is in its upper or magnetizing position.

4. The phase 6, extends from the armature of relay L over the contact 1 thereof to the right-hand terminals of the operate and release drive motors 600 and 606. The left-hand terminals of these drive motors extend to respective contacts 1 and 2 of relay K and over the armature of relay K, depending upon whether relay K is released or operated, back to the phase 1, bus. The righthand terminals of the fine power control motors 607 and 60S extend over the contact of relay M back to contact 3 of relay L. It is thus apparent that with relay L in the position shown in Fig. 6, the coarse motors 600 and 606 are enabled for operation and the fine control motors 607 and 603 are disabled. The converse is true, as will be pointed out in subsequent description, when relay L is operated so that its armature makes contact with its contact 3.

Variac 620 selects a suitable quantity of alternatingcurrent voltage from the secondary of transformer 624, a portion thereof appearing across the resistance 622 in the voltage divider comprising resistance 621 and 622 and being applied to the series circuit including the winding of relay E and condenser 632. This causes a specified level of alternating current to flow in this circuit through the winding of relay E, the level of which is too low to cause the relay E to operate on the alternating current alone. However, it will be noted that negative battery (positive terminal grounded) is applied over the armature of relay E and the contact 2 thereof, through potentiometer 630 and through resistance 631, through the Winding of relay E and to ground through resistance 622. Also, it will be noted that condenser 632 shunts the lower side of the winding of relay E to ground. In this position of relay E, the condenser 632 will acquire a charge at a rate determined by the setting of the potentiometer 630 The circuit variables are chosen, preferably, so that the maximum value of direct current which may flow through the winding of relay E is by itself less than the operate value of current for relay E.

As the direct current flowing in the winding of relay E increases (as the charge on condenser 632 increases), it is arranged that at some suitable point on this exponential direct-current curve the alternating current injected into the relay circuit will be suficient such that the sum of the alternating current and the exponentially increasing direct current will be suificient to operate relay E. When this happens, the armature of relay E moves from its contact 2 to its contact 1. This removes the directcurrent charging circuit for condenser 632 and permits capacitor 632 will, therefore, decrease at an exponential rate determined by the resistance in this discharge path.

Since this resistance is fixed for any one setting of the variac620, the time constant of the discharge circuit for condenser 632 is substantially constant. When the discharge current in this circuit, including the winding of the relay E, has decreased to a sufiicient extent, the summation of the alternating and direct currents through the winding of relay E will be such as to permit relay E to again release, whereupon the armature of relay E again makes contact with its contact 2 to cause the abovedescribed cycle to repeat itself.

Potentiometer 630, as above explained, changes the time constant in the charging circuit for condenser 632, thereby varying the amount of time from a specified starting point at whichrelay E will operate. Potentiometer 630, therefore, may be termed as a Percent Make Control; that is, it will control the amount of time when the armature of relay E is in contact with its contact 1 as compared to the total amount of time including the latter plus the amount of time when the armature of relay E is in contact with its contact 2.

At the instant that the armature of relay E makes contact with its contact 1, a circuit is completed from negative battery, armature of relay E, contact 1 of relay E, resistance 629, potentiometer 628, winding of relay F, secondary winding of transformer 623, contact 2 of relay I to ground. The phasing of transformers 623 and 624 is arranged such that the upper side of the winding of relay F carries the same phase of alternating current as the upper winding of relay E, as indicated on Fig. 6 by the notation Same Phase. Potentiometer 628 simultaneously adjusts the levels of the alternating and direct currents which are permitted to flow through the Winding of relay F and thereby adjusts the instant at which the composite current through the winding of relay F first reaches the operate value, at which time the armature of relay P will transfer from its contact 2 to its contact 1.

When relay F transfers to its contact 1, a circuit is completed from ground over the armature and contact 1 of relay F to conductor 644 extending into Fig. 7, through the winding of relay A, and to negative battery through a parallel circuit of condenser 701 and potentiometer 700, and conductor 644 extends over the run positive of switch 720 to operate relay H for a purpose to be described later. The condenser 701 in the circuit of relay A presents an instantaneous short circuit across the potentiometer 700 and permits relay A to operate very quickly upon the grounding of conductor 644. Sooner or later, depending upon the setting of potentiometer 700, condenser 701 will acquire a suflicient charge to cause relay A to release.

The settings of the potentiometer 628 in the circuit of relay F and potentiometer 700 in the circuit of relay A may be considered, respectively, as pulse start and pulse end potentiometers, whereby the specific instant with respect to the alternating-current Wave form at which relay A will operate is determined by potentiometer 628 and the specific instant of the release of relay A compared to the same alternating-current wave form is determined by the setting of potentiometer 700.

The net effect of this relaxation oscillator type of relay circuit is that relay E will operate and release at a rate which is preferably a subharmonic of the alternating- -current frequency (but broadly may be any integral 634 and over conductor 637 to the contact of relay A.

When relay A is operated, the phase I 1 is extended from or both, to the wiper or wipers of the fine power control potentiometers 610 or 611 or both, to apply a pulse of alternating-current power to one or the other or both of these electromagnets during the time when relay A is operated. An oscilloscope may be connected across the resistance 634 to observe the alternating-current half cycle of power which is transmitted through the contact of relay A. With such a continuous indication, the various adjustments, such as the variac 620 and potentiometers 630, 628 and 700, may be adjusted such that the portion of alternating-current power delivered through the closed contact of relay A may be exactly a positive or negative half cycle more or less.

The previously described relaxation oscillator type of power control circuit involving relays E, F and A, etc. is disclosed and claimed as a power control circuit in the application of C. E. Pollard, Jr., Serial No. 418,396, filed on March 24, 1954, now Patent No. 2,781,459 issued February 12, 1957. A more detailed and more precise description of the operation of this power control circuit is provided therein.

Therefore, with the switch 615 in the upper or magnetizing position, selected polarity half cycles of the alternating-current power (the magnitude of which is de termined by the settings of the variacs 604 and 609) are transmitted through the contact of relay A over contact 1 of relay B to the right side of the winding of electromagnet 712 and over conductor 641 into Fig. 6, over the right outer blade of switch 615, and back over conductor 640 into Fig. 7, to the left side of the winding of electromagnet 713 and in parallel back over conductors 635 and 636 to the wipers of the fine power control potentiometers 610 and 611, out over the respective t 1 terminals thereof to the wipers of the respective coarse power control variacs 604 and 609, to the preselected portion of alternating-current voltage at which they are set.

These selected polarity half-cycle pulses of power are considered as magnetizing pulses, whereby each of the permanent magnets 715 and 717 associated with the release and operate contacts 714 and 716 of relay I (the relay under test) are overmagnetized.

After the operator is satisfied that sufficient time has been allowed for these magnetizing pulses to take efiect (actually only one pulse is necessary), the switch 615 may be transferred from its upper to its lower or demagnetiz- .ing position. As an incident to this operation, the variacs 604 and 609 will be manually adjusted to a low value toward their 1 1 terminals. This causes a number of effects, as follows:

1. The phase of the alternating-current power applied to the primaries of transformers 623 and 624 is reversed. This, as will be appreciated, will cause the power pulses which are transmitted through the contact of relay A to be of the reverse polarity from those previously described. These new power pulses will be referred to as demagnetizing pulses.

2. Phase Q1 will be applied over the left outer blade of switch 615 to the armature of relay L and thence over contact 2 thereof and conductor 642 to the top of potentiometer 727, whereby alternating current will be trans- .mitted through transformer 726 to be injected in series with the previously described direct-current reset and test values preselected by the potentiometers 702, 705, 708 and 709.

3. The right outer blade of switch 615 removes the short circuit across conductors 649 and 641, which removes the short circuit across contacts 1 and 2 of relay B in Fig. 7. This permits relay B to select by its release or operation which of the two electromagnets 712 and 713 will be permitted to receive demagnetizing pulses transmitted over the contact of relay A.

' 4. A circuit is completed from ground, over the right inner blade of switch 615, through resistance 617 and to battery through the windings of all of the magnetic clutch magnets, such as magnet 6133 associated with the operate coarse power control mechanism. This causes all of the clutches, such as clutch 692, to engage, whereby the respective drive motors, if energized, will cause the associated wipers of the variacs 664 and 609 and potentiometers 610 and 611 to move from their in terminals toward their I z terminals at a fairly slow rate depending upon the speed of the associated motor and the amount of gear reduction in the respective reduction gear boxes, such as reduction gear box 6111 for motor 600.

5. A circuit is completed from ground, over the right middle blade of switch 615, through resistance 61% to negative battery through the Winding of relay L. The condenser 646 across the winding of relay L will acquire a voltage charge, the value of which, however, is insufficient to cause the relay L to operate, but which is sufiicient to cause the relay L to stay operated once it is operated by other means.

Simultaneously with the operation of relay F from its No. 1 contact to its No. 2 contact which, as previously explained, operates relay A by applying ground to conductor 644, relay H is also operated by an extension of conductor 6 34 over the run position of switch 720. Relay H, in operating, applies the operate reset value of current from potentiometer 705 over contact 1 of relay D and contact 2 of relay H, through winding 719 of the test relay I, through the secondary of transformer 726 and through switches 723 and 724 to the connection of resistances 721 and 722. As previously explained, this value of operate reset current will insure that the armature 718 of relay I remains in contact with its contact 714 during the time when relay A is operated to apply a demagnetizing pulse to the electromagnet 712. The magnitude of this demagnetizing pulse as previously explained, will be determined by the position of variac 604 as it moves slowly from its 2 1 terminal toward its I 2 terminal under the control of motor 690, which at this time is connected to the alternating-current source of power over contact 1 of relays K and L.

Relay A will release, terminating the application of a demagnetizing pulse to the electromagnet 712, at a time determined by the setting of potentiometer 706, as previously described. As soon as relay F releases to its contact 2, relay 1-1 will release. The release of relay H, therefore, occurs during the time when relay A is also released, which represents the time interval between applications of demagnetizing pulses to electromagnet 712. Relay H, in releasing, completes a circuit from the potentiometer 702 over contact 1 of relay C, contact 1 of relay H,

through the winding 719 of the test relay I, through the relay I transfer from contact 714 to contact 716 of relay I when the permanent magnet 715 has been properly demagnetiz'ed. Due to the injection, by means of transformer 726, into this test current circuit for relay 1 of a suitable quantity of alternating current, the armature 718 will accomplish the prescribed transfer earlier in the demagnetizing cycle of permanent magnet 715 than it otherwise would if the alternating current were not superimposed upon the direct current in this circuit of the winding 719. That is, as the relays usually under adjustment are capable of operating or releasing in less than a half cycle of the superimposed alternating current, the latter permits the relay to operate or release whenever the composite current passes through a value about equal to the respective direct-current sensitivities.

If the armature 718 of relay 1 does not accomplish the required transfer, no changes in the circuit operation occur and the relay A is again operated along with relay H to apply another demagnetizing pulse to the electromagnet 712, this time of a slightly increased magnitude due to the fact that during the intervening time the variac 604 has moved farther from its In terminal thereby selecting a slightly increased magnitude of demagnetizing current. Upon the operation of relay H, as before, the preselected value of operate reset current is applied to the winding 719 of relay I to insure that the armature 718 remains in contact with the release contact 714 of relay I. Thereafter, as soon as the relay A has released and relay H has released, as evidence of the fact that the demagnetizing pulse is over, relay H again being released once again applies the selected operate test value of current to the winding 719 of relay I. p

This process continues until such time as the armature 7'18 of relay I transfers to its operate contact 716 during the time interval between applications of demagnetizing pulses to the electromagnet 712. When this transfer takes place, a circuit is completed from negative battery over the armature 718 of relay 1, contact 716, resistance 729, to the right side of the lower winding of relay G, through the lower winding of relay G and to conductor 643 extending to ground over contact 2 of relay F. It will be noted that condenser 736 shunts the lower winding of relay G thereby causing a slight delay in the operation of relay G, after which delay the armature of relay G will be operated to make contact with its contacts 2 and 3.

Upon the movement to the right of the armature of relay G, ground is extended over the armature thereof and over contact 3 of the relay G, through condenser 733 and over conductor 645 to the upper side of the winding of relay 1. This ground pulse augments the charge existing on condenser 647, whereby the relay I will cause its armature to transfer from contact 2 to contact 1, where the armature of relay I will remain for a short period of time depending upon the amount of time the condenser 733 requires to obtain a charge. After this short interval of time, relay I will release again to its contact 2. During the time that relay I is operated to its contact 1, relay M will be operated in an obvious circuit for a'purpose to be described later. Relay 1, in

operating for a short period of time, immobilizes the circuit of relay F, thereby permitting the armature of relay F to remain in contact with its contact 2, and thus preventing the immediate reoperation of relays A and H when relay E continues to oscillate.

Relay G, in operating its armature to the right, also completes a circuit from ground over its contact 2, through the run position of switch 737, to conductor 638 which, in an obvious manner, causes the operation of relays B, C and D. The grounding of conductor 63% in Fig. 6 causes the operation of relays N and K. Relay N, in operating, applies a ground pulse 'over its contact 1 through condenser 626 and through resistance 619 to the left side of the winding of relay L. Condenser 626 will very quickly, however, acquire a charge which then removes the additional. pulse from the winding of relay 'L, and relay L is arranged such that this single pulse will not cause it to operate. Relay K, in operating, transfers the phase P, of alternating-current power from its contact 1 to its contact 2 thereby stopping the operation of motor 6196 and starting the operation of motor 6%. Furthermore, during the time when the armature of relay G is in contact with its contacts 2 and 3, the previously charged condenser 732 associate with contact 1 of relay G will discharge through resistance 735.

After relay J of Fig. 6 releases, after its momentary operation as previously described, the circuit for relay F is again completed and the relaxation oscillator relay circuit comprising relays E and F again comes into play to cause the operation of relay A of Pig. 7 to again apply a demagnetizing pulse over its contact However, with relay B operated, this demagnetizing pulse, the magnitude of which is. determined by the nowhcontinuaily slowly increasing value of alternating current voltage 13 selected by the variac 609 under the control of motor 606, will be transmitted over contact 2 of relay B to the electromagnet 713. During the interval of time when relay A is operated, relay H will again be operated, as previously described, and a circuit will becompleted from the release reset potentiometer 709 over contacts 2 of relays D and I-I-to apply to the winding 719 of relay I the predetermined value of release reset current whereby the armature'718 of relay I is forced to'remain in contact with the operate contact 716 of relay I.

During the interval between the magnetizing pulses when relays A andH are'released, as above described, a circuit is completed from the release test potentiometer 703 over contact 2 of relay C and contact 1 of relay H, whereby the predetermined value of release test current is applied to the winding 719 of relay I to determine whether or not the armature 718 will transfer back to the release contact 714-. As previously explained, this release test current is augmented againby the portion of alternating current transmitted through transformer 726. r If the armature 718 does not transfer back to ca 714, the above-described demagnetizing process is rep 2 whereby another demagnetizing pulse is transmitted to the electromagnet 713. This, as will be obvious from previous description, will beof a slightly increased magnitude due to the fact that the variac 609 has been moving slowly under the control of motor 606 toward its I terminal.

Sooner or later armature 718 will accomplish the desired transfer, by which time-a circuit is completed from negative battery, through the armature 718 of relay I, over contact 714 of relay I and through resistance 728 to the right side of the upper winding of relay G. Relay G will operate in the same manner as previously described, after a short delay caused by the short-circuiting effect of condenser 730, to move its armature from the right to the left, thereby releasing relays B, C, D, *N and K. This, as will be obvious at this point, reverts the entire control circuit again to the condition whereby demagnetizing pulses will again be applied to the electromagnet 712 associated with the release contact 714 of relay This back-and-forth procedure will continue under the control of thecoarse variacs 604 and 609, as controlled by their respective motors 600 and 1606, until the relay G operates to and releases from its contact 2 at a sufiiciently rapid rate such that relay N of Fig. 6 is operated and released at a fairly fast rate, whereby a succession of ground pulses are applied over contact 1 and relay N to the winding of relay L. Relay I is also operated and held operated by the rapid pulsing of the relay over its contacts 3 and a. This immobilizes the F relay and operates the M relay, thereby to stop .the demagnetizing procedure. S ich a rapid pulsing of the winding of relay L will cause the condenser 646 in shunt thereof to acquire a suiiiciently increased charge to cause relay L to operate its armature into engagement with its contact 3. Relay L, in operating its armature into engagement with its contact 3, remains in this position because the steady charge on condenser 643 is now sufficient to accomplish this holding effect. Relay L, in so operating, causes the power circuit for motors 600 and 606 to be opened and causes the power circuit for motors 607 and 608 to be completed, in an obvious manner, over contact 3 of relay L and the contact of relay M (at such time as relay M releases upon the release of relay I into engagement with contact 2 of relay I as previously described). The operation of relay L, in addition to bringing into operation the fine power control in the upper right portion of Fig. 6 instead of the coarse control as previously effected, also removes from contact 2 of relay L the previously-described circuit whereby the trans former 726 in Fig. 7 receives alternating-current power. This causes the buzzing of the relay I to cease, whereupon relays M and I release and relays N and G cease to buzz. This means that during the remaining part of the relay adjustment there will no longer be any alternating currentsuperimposed upon the test currents injected-into winding 7190f relay I and the circuit may continue its automatic operation as the wipers of the fine power control potentiometers 610 and 611 move slowly from their .4 terminals toward their I terminals to apply very small, but nevertheless increasing amount of-alterhating-current demagnetizing pulse power to the two electromagnets 712 and 713.

Eventually, a point will be reached where the'armature 718 of relay I will even morerapidly and more quickly transfer back and forth between contacts 716 and 714, and vice versa, of relay I and'to in turn cause relay'G to switch quickly back and forth between its contacts .1 and 3, whereupon sufficiently frequent pulses will be applied to conductor-645 to cause relay J to remain operated in the position where contact 1 of relay J 'is .grounded continuously. This causes a continuous operation of relay M thereby to open at its contact the operating circuit for motors 607 and 608 to stop any further demagnetizing procedure.

This condition is visually indicated by the two lamps 710 and .711 in Fig. 7 which, under this condition, will flash back and forth in a very rapid fashion, thereby indicating to theoperator that the demagnetizing procedure for adjusting relay I has come to a proper conclusion. At this point, the operator will move switch 615 to'the off-position and will remove relay I from the electromagnet fixture preparatory to repeating the above test on a new relay.

Before beginning a new-test, the operator will readjust the fine potentiometers 610 and 611 to their minimum or I positions and'may or may not return the variacs 604 'and.609 to their starting positions. In Fig. 6 the ffine switch .627 maybe manually closed, if desired, assuming-that a'coarsc setting of the variacs 604 and 609 has been predetermined. This will cause the immediate operation of relay'L, as will be obvious, such that only the motors 607 and 608 controlling the fine, power control will be effective.

The embodiment of the invention disclosed in Figs. 8 and 9 performs substantially the same relay adjusting; job-as that described previously-in connection with Figs. 6 and 7. The embodiment of Figs. 8 and 9 differs from the embodiment of Figs. 6 and 7 in a-number of deails the differences of major significance being as follows:

1. The means whereby successively increasing increments of demagnetizing current are supplied from the source of alternating-current power comprises a pair-- of step-by-step switches shown in the upper left portion; of Fig. 8. These switches are self-normalizing and, therefore, need not be manually readjusted tov their starting positions prior to each relay adjustment cycle.

2. There is no coarse control over the increments; of demagnetizing pulse magnitude. The total; excu'r sion of the step-by-step selectors provide equal incre ments of power throughout the entire test and; no alternating current is superimposed on the relay. test currents,

3. A number of additional control relays are pro-- vided as will be apparent from subsequent description.

In reference to Fig. 9, the relay undertest is shown; in the right-hand portion in the same manner as pre viously discussed with respect to Fig. 7. With the main: power switch 802 in Fig. 8 unoperated and with the magnetizing switch 900 and demagnetizing switch 901, run switch 902 and run switch 904 also unoperated, thevan'ous operate and release currents of the reset and test values may be set up on the potentiometers 906,, 909, 912 and 913 in substantially the same manner as: described in connection with the circuit of Figs. 6 and 7..

With the release switch 903.and the reset switch 905' both unoperated, relays 3, 4 and 5 will be in the posi tion shown on Fig. 9. Whereupon, by manipulating.- switch 915 in one direction or the other depending upon:

justment of potentiometer 906 has been set at the prescribed value of operate test current. Now, with switch 903 closed, operating relays 3 and 4 in an obvious cir :cuit to ground over the contact of switch 903, the potentiometer 912 will be effective over contact 2 of relay 3 and contact 1 of relay to setup the prescribed value of release test current. With switch 903 operated,

switch 905 is also operated, thereby operating relay 5 in an obvious circuit, the potentiometer 913 may be adjusted whereby it is effective over contact 2 of relay 4 and contact 2 of relay 5 to adjust the prescribed value of the release reset current. Now with switch 905 operated and switch 903 released, thereby maintaining relay 5 operated and releasing relays 3 and 4, potentiometer 909 is effective by means of contact 1 of relay 4 and contact 2 of relay 5 to establish the prescribed value of operate reset current. Switches 903 and 905 may then be released and switch 916 may now be closed to short-circuit the meter 917.

Upon the closure of the main power switch 802 in Fig. 8, alternating-current power is applied from the source 800 thereof, through fuse 801 and switch 802, to the two alternating-current power lines designated phase 1 and phase I This applies power to the primary windings of transformers 816, 810, 804 and 803 and also applies alternating-current power to variacs 811 and 805.

To accomplish the initial over-magnetization of the permanent magnets 925 and 924, associated with the respective release and operate contacts 922 and 923 of the relay under test, the magnetizing switch 900 will be closed causing the following operations:

1. Relays and 1601: Fig. 8 will be operated in a circuit extending from ground over contact 4 of switch 900 and over conductor 845 to the windings of relays 15 and 16.

2. A circuit is completed from ground over contact 5 of switch 900, conductor 838 into Fig. 8 and over the contact of relay 11 to place ground on the bottom terminal of the secondary winding of transformer. 803.

3. Grounds are extended over contacts 1 and 3 of switch 900 and over respective conductors 848 and 856 extending intoFig. 8 to the respective wipers 820 and 824 of the two step-by-step selectors.

4. A circuit is completed for operating relay 14 in Fig. 8 extending from the phase P2 power line through the winding of relay 14, conductor 851, contact 2 of switch 900, conductor 852, back to the phase In power line.

Relay 9 in Fig. 8 operates in the same fashion as previously described for relay E inFig. 6; that is, relay 9 will oscillate its armature back and forth between its contacts 1 and 2 at a rate which is preferably a subharmonic of the alternating-current frequency (such as three to five cycles per second as compared to a 60-cycle source). The rate at which relay 9 oscillates is determined primarily by the settings of the variac 825 and the potentiometer 826, both comprising, in effect, a frequency adjustment. The amount of time when the armature of" relay 9 dwells at us contact 2, as compared to the total amount of time when it dwells against contact 2 and contact 1, 'is adjustable by means of the percent make potentiometer 829.

Each time relay 9 operates its armature against its contact 2, relay 10 will be operated by a combination of alternating and direct currents, and it will operate at an instant with respect to the alternating-current wave form 1% determined by the adjustment of the pulse start potentiometer 830.

Each time relay 10 operates and grounds its contact, ground is applied to the winding of relay 1 and over conductor 843 into Fig.9. Relay 1 will thereupon operate and will stay operated for a short interval of time depending upon the setting of the pulse stop potentiometer 858, which adjusts the time constant of the circuit whereby condenser 859 will acquire a charge suflicient to cause relay 1 to release.

The various adjustments comprising variac 825, frequency potentiometer 826, percent make potentiometer 829, pulse start potentiometer 830 and pulse stop potentiometer 858 are preferably made with an oscilloscope connected across the terminals of resistance 846, such that the relay 1 will close its contact when the alternatingcurrent wave form goes through zero in one direction and will open its contact when the alternating-current wave form goes through zero in the other direction; that is, the contact of relay 1 will be closed only during a selected polarity half cycle (more or less) of the alternatingcurrent power, all as previously described with respect to relay A of Fig. 7.

During the operation of relay 1, a circuit is completed from the phase @1 power line over the contact of relay 15, in parallel over contacts 1 and 2 of relay 16, over conductors 857 and 844 into Fig. 9, to the respective right and left sides of the windings of the electromagnets 919 and 917, back over respective conductors 850 and 849, to the respective contacts 2 and 1 of relay 2. It will be noted that the contacts 1 and 2 of relay 2 are short circuited by means of contact 1 of the operated relay 14. Therefore, no matter what position relay 2 may be in, the circuit continues over the armature thereof through resistance 832, over the contact of relay 1, through resistance 846 and fuse 847 and over contact 2 of relay 14 to the top terminal of the variac 811, which will carry phase I z of the alternating-current power. Selected half cycles of a specified polarity of the alternating-current power are, therefore, applied to both of the electromagnets 917 and 919 to over-magnetize them.

In the event that the two stepping switches are not in the positions shown in Fig. 8, the grounds on conductors 848 and 856 in Fig. 8 will be extended over the respective wiper arms 820 and 824 and over the contacts of the respective stepping magnets SEL1 and SELZ to operate them. Immediately upon being operated. these respective stepping magnets SEL1 and SEL2 open their own operating circuits, thereby releasing and advancing the associated wiper arms one step in the directions shown by the arrows. It will be appreciated that, for instance, the wiper arms 817, 818, 819 and 820 are associated with the stepping magnet SEL1 and that the Wiper arms 821, 822, 823 and 824 are associated with the stepping magnet SEL2. Each of these stepping switches continues to step automatically until position 22 is arrived at, whereupon ground will extend over the wipers 819 and 823 to battery through the right-hand windings of the respective relays 7 and 8. These relays 7 and 8 will thereupon operate their armatures into the positions shown in contact with their respective contacts 1. If the respective stepping switches are initially in the position shown, the respective relays 7 and 8 will therefore nevertheless be in the position shown. It will be noticed that with relays 7 and 8 in the positions shown the primary windings of transformers 812 and 808 are short-eircuited so that no alternatingcurrent voltage or current is induced into the secondaries of these transformers.

The magnetizing switch 900 will now be released preparatory to setting the circuit into automatic operation for demagnetizing the two permanent magnets 925 and 924 of the relay under test, thereby releasing relays 15 and 16, removing ground from the wipers 820 and 824 of the stepping switches, releasing relay 14 and removing 17 ground from conductor 838 thereby stopping the oscillation of relay 9, etc.

To initiate the demagnetizing procedure, switches 902 and 904 are placed in their run positions and the demagnetizing switch 901 is closed. The closure of the demagnetizing switch 901 accomplishes the following things:

1. Ground is extended over contact 4 of switch 901 to conductor 838 to cause the relay 9, etc., to start oscillatmg.

2. Ground is extended over contact 3 of switch 901 to conductor 853 extending into Fig. 8 to cause the operation of relays 17 and 18.

3. Ground is extended over contact 1 of switch 901 to conductor 837 extending into Fig. 8 and to battery through the left-hand windings of relays 7 and 8. This does not cause relays 7 and 8 to operate, but will hold them operated if they are caused to operate when and if the respective step-by- step wiper arms 819 and 823 ground the terminals 22 of their respective contact arcs, as previously described.

4. The conductor 843 in Fig. 8, which is grounded each time relay 10 is operated, is extended in Fig. 9 over the contact of switch 904 to the winding of relay and is extended over contact 2 of switch 901 to conductor 854 extending back into Fig. 8 to the winding of relay 13. Therefore, each time that relay is operated (operating relay 1 as previously described) relay 5 will operate to cause the operate or release reset value of current to be applied to the relay under test and relay 13 will be operated to extend a pulsing ground over its contact and over contact 1 or 2 of relay 6 to the respective stepping magnet SEL2 or SEL1 in Fig. 8. As soon as the ground is removed from conductor 843 in Fig. 8, when relay 10 releases, relays 5 and 13 likewise will release, thereby respectively calling into operation the operate or release test value of current for the relay under test and permitting the operated stepping magnet SEL1 or SEL2 to release to advance the associated stepping switch one position.

With the relay under test in the position shown in Fig. 9, that is, with its armature 920 in contact with its release contact 922, a circuit will have been completed for causing the relay 12 of Fig. 8 to operate into the position shown with its armature in contact with its contact 2. This circuit extends from battery, armature 920 of the relay under test, contact 922, resistance 926, conductor 840 through the winding of relay 12, conductor 841, resistance 927 to ground through the operate lamp 929. The operate lamp 929 will not light in this circuit due to the impedance in series therewith. The release lamp 928 will light, being directly connected to battery over contact 922 and armature 920 of the relay under test. The fact that the release lamp 928 is lit indicates to the operator the situation of the relay under test. With relay 12 in the position shown, ground is removed from its contact 1 and from conductor 839, which extends over the contact of switch 902 to relays 3 and 4 of Fig. 9 and over conductor 855 into Fig. 8 to the windings of relays 2 and 6. These relays 3, 4, 2 and 6, therefore, will be released and in the positions shown in the drawing.

Under this condition a circuit is completed each time relay 1 is operated to apply a reverse polarity (that is, reverse with respect to the magnetizing pulses) of alternating-current power to the electromagnet 917 associated with the permanent magnet 925 which comprises part of the release contact 922 of the relay under test. This circuit extends from the phase in power line in Fig. 8 over the contact of relay 18, through fuse 847 and resistance 846, contact of relay 1, resistance 832, contact 1 of relay 2, conductor 849, through the winding 917 of the electromagnet, conductor 844, contact 2 of relay 17, wiper arm 822, wiper 809, the secondary of transformer 808 and the wiper of variac 805, back to the phase In side of the power line. It will be noted that the polarity of this circuit is reversed from that previously 18 described in connection with the magnetizing part of the procedure. In View of the fact that the primary of transformer 808 is short-circuited over contact 1 of relay 8 (it will be noted that shorted or energized transformer 812 represents a substantially constant impedance), the only voltage available in this demagnetizing path is the voltage available from the variac 805, and the small amount of voltage represented by the position of the wiper 809 which is of no particular significance except that it may be adjusted to one position or the other for purposes of balancing out small differences between transformers, such as 812 and 816 or 808 and 810. Simultaneously, with the closure of the contact of relay 1, as previously explained, conductor 843 is grounded by the operation of relay 10, whereupon relay 5 is operated over the contact of switch 904. This causes the operate reset value of current to be applied on potentiometer 909 to the winding 921 of the relay under test to insure that the armature 920 remains in contact with contact 922.

As soon as relay 10 releases, relay 5 will release, thereby causing the operate test value of current to be applied from potentiometer 906 to the winding 921 of the relay under test. In the meantime, relay 13 had been operated and released once thereby causing the stepping magnet SEL2 to operate and release once, advancing the associated wiper arms one step.

If the armature 920 of the relay under test does not transfer to its contact 923, another demagnetizing pulse will be applied to the electromagnet 917 upon the reoperation of relay 10. This demagnetizing pulse will be of slightly increased magnitude as determined by the advance of one step of the wiper arm 822. Simultaneously with the application of this next demagnetizing pulse to the electromagnet 917, relay 5 is reoperated to again apply the operate reset value of current to the winding 921 of the relay under test. As soon as relay 10 releases, relay 5 is released to cause the operate test value of current to be applied to the winding 921. In the meantime, the stepping magnet SEL2 is again reoperated and released to cause the wiper arms associated therewith to advance still another step.

This process continues uninterruptedly until such time as the armature 920 of the relay under test, in response to the application to the winding 921 of the operate test value of current, moves from its contact 922 to its contact 923. This causes the release lamp 928 to extinguish and the operate lamp 929 to become lighted. This also causes a circuit to be completed from battery over the armature 920, contact 923, resistance 927, conductor 841, winding of relay 12, conductor 840, resistance 926 to ground through the release lamp 928. This battery pulse applied to the winding of relay 12, over and above the steady charge maintained on condenser 861, is sufficient to cause the relay12 to move its armature from its contact 2 into contact with its contacts 1 and 3. This movement of the armature of relay 12 causes the charge previously acquired by condenser 833 to be dissipated in resistance 835 and causes a ground pulse to be applied over the armature of relay 12, contact 3 thereof through condenser 834, to the winding of relay 11, which ground, augmenting the charge normally carried by condenser 860, will cause relay 11 to operate momentarily until condenser 834 can acquire a sufiicient charge to cause relay 11 to release. This momentary operation and release of relay 11 opens the circuit between the grounded conductor 838 and the bottom terminal of the secondary winding of the transformer 803, thereby causing the relay 9 to stop oscillating. Ground is also applied over contact 1 of relay 12 to conductor 839 extending into Fig. 9 and over the contact of switch 902 to operate relays 3 and 4 and extending over conductor 855 into Fig. 8 to operate relays 6 and 2.

Upon the release of relay 11, after a momentary delay above mentioned, relay 9 is again permitted to oscillate to again cause relays 10, 1 and 5 to operate to cause a 19 r demagnetizing-pulse to be applied to the electromagnet 919. 'lThe" circuit for this demagnetizing pulse extends from the phase I side of the power line, over the contact of relay 18, through fuse S47, resistance 846, contact of relay 1, resistance 832, contact 2 of relay 2, conductor 850, through the winding of the electromagnet 919 back over conductor 857, contact 1 of relay 17, to wiper 818 of the upper stepping switch and out over the wiper 813, through the secondary of transformer 812, back to the wiper of variac 811. The only voltage available in this demagnetizing pulse circuit is the voltage derived from the wiper arm of variac 811 and the small amount of voltage available due to the position of the wiper arm 813, by virtue of the fact that relay 7 is short-circuiting the primary of transformer 812.

Due to the fact that relay 4 is operated during this demagnetizing pulse and due to the fact that relay 5 is also operated, potentiometer 913 will cause the release reset value of current to be applied to the winding 921 of the relay under test to force the armature 920 to remain in contact with the operate contact 923 of the relay under 'test. As soon as the demagnetizing pulse is over with, as indicated by the release of relay 10, relay 5 will release and will cause, in combination with the operation of relay 3, the potentiometer 912 to apply to the winding 921 of the relay under test the prescribed value of release test current. It the armature 920 does not return to contact 922 in response to this value of release test current, then another demagnetizing pulse of slightly increased amplitude is applied to the electromagnet 919. This increased amplitude of demagnetizing pulse is produced because during the operation and release of relay 10, conductor 843 is grounded and ungrounded, which in turn causes relay 13 to operate and then to release. The operation and release of relay 13 extends a ground pulse over its contact and contact 2 of relay 6 to the winding of the stepping magnet SELI, whereupon the stepping magnet SELl operates and releases causing the associated wiper arms to advance one step.

This process continues with the armature 920 in contact with the operate contact 923 until such time as the armature 920 transfers to the release contact 922 in response to the prescribed value of release test current, whereupon relay 12 is again operated to cause its armature to make contact with its contact 2. This momentarily operates relay 11 to stop the oscillation of relay 9, which stops the application of demagnetizing pulses to the electromagnets and releases relays 3, 4, 2 and 6 to revert the relay control circuit to the previously-described condition whereby further demagnetizing pulses may be applied to the electromagnet 917.

The above-described procedure is repeated back and forth with respect to the electromagnets 917 and 919 until a point is reached where the armature 920 moves back and forth between contacts 922 and 923 immediately in response to each respective application of the release and operate test values of current. This will cause a similar oscillation of relay 12 back and forth between its contacts 2 and 3 whereby a succession of ground pulses is applied to the winding of relay 11 at a sufiiciently high rate to maintain relay 11 operated continuously. The continuous operation of relay '11 immobilizes the demagnetizing procedure by causing relay 9 to stop oscillating. The rapid flashing back and forth of the two lamps 928 and 929 provides a visual indication to the operator that the relay under test has arrived at a con dition whereby the permanent magnets 925 and 924 have been demagnetized to such an extent that the respective operate and release test values of current prescribed for the relay under test properly cause the armature 920 to perform as prescribed.

The relay under test may now be removed from the circuit and another relay may be placed under test, whereupon the above procedure is repeated, it being appreciated that as soon as the magnetizing switch 900 is operated with the demagentizing switch 931 released, the two stepping mechanism of'Fig. 8 will automatically adjust themselves to their normal starting positions.

It is to be understood that the above-described arrangements are merely illustrative of the application of the principles of the invention. Numerous other arrangements may be devised by those skilled in the art without departing from the spirit and scope of the invention.

What is claimed is:

1. A'circuit for automatically adjusting the permanent magnet bias of a test relay including an energizing winding and a contact and a permanent magnet and a magnetic armature movable in operable relation to said contact 7 under the influence of the combination of the magnetic field produced by' the energization of said winding and the magnetic field of said magnet, said circuit comprising a source of electric power, switch means having a magnetizing and a demagnetizing position, a magnetizingdemagnetizing coil adaptable to magnetize or demagnetize said test relay magnet, a power control circuit responsive to the op'eration of said switch means into its magnetizing position to apply at least one pulse of current of a magnetizing polarity to said coil from said source, said current pulse being adaptable to over-magnetize said magnet, variable means operable to deliver variable increments of power from said source to said coil under the control of said control circuit, means automatically responsive to the operation of said switch means into its demagnetizing position to cause said control circuit to control said variable means to apply a sequence of pulses of current of a demagnetizing polarityand of successively increasing increments of magnitude to said coil from said source, said sequence of pulses being adaptable to demagnetize said magnet to successively increasing extents, means automatically operative by said control circuit during the application of each demagnetizing pulse of said sequence to said coil and adaptable to cause said armature to be placed into contact with said contact and automatically operative by said control circuit during the intervals before and after demagnetizing pulses of said sequence are applied to said coil and adaptable to apply to the winding of said test relay a test current of such a magnitude and polarity as would move said armature away from said contact when the permanent magnet bias is properly adjusted by said sequence, and means automatically operative by said control circuit and adaptable to detect the movement of said armature away from said contact.

2. A circuit for automatically adjusting the permanent magnet bias of a test relay including an energizing winding and a contact and a permanent magnet and a magnetic armature and movable in operable relation to said contactunder the influence of the combination of the magnetic field produced by the energization of said winding and the magnetic field of said magnet, said circuit comprising a source of electric power, switch means having a magnetizing and a demagnetizing position, a magnetizing-demagnetizing coil adaptable to magnetize or demagnetize said test relay magnet, a power control circuit responsive to the operation of said switch means into its magnetizing position to apply at least one pulse of current of magnetizing polarity to said coil from said source, said-current pulse being adaptable to over-magnetize said magnet, variable means operable to deliver variable increments of power from said source to said coil under the control of said control circuit, means automatically responsive to the operation of said switch means into its demagnetizing position to cause said control circuit to control said variable means to apply a sequence of pulses of current of a demagnetizing polarity and of successively increasing increments of magnitude of said coil from said source, said sequence of pulses being adaptable to deenergize said magnet to successively increasing extents, means automatically operative by said control circuit during the application of each demagnetizing pulse of said sequence to said coil and adaptable to cause said armature to be ass me placed into contact with said contact, means automatically operative by said control circuit during the intervals before and after demagnetizing pulses of said sequence are applied to said coil and adaptable to apply to the Winding of said test relay a test current of such a magnitude and polarity as would move said armature away from said contact when the permanent magnen bias is properly adjusted by said sequence, and means automatically operative by said control circuit and adaptable to detect the movement of said armature away from said contact.

3. A circuit for automatically adjusting the permanent magnet bias of a test relay including an energizing winding and a contact and a permanent magnet and a magnetic armature movable in operable relation to said contact under the influence of the combination of the magnetic field produced by the energization of said winding and the magnetic field of said magnet, said circuit comprising a source of electric power, a manually operable switch having a magnetizing and a demagnetizing position, a magnetizing-demagnetizing coil adaptable to magnetize or demagnetize said test relay magnet, a power control relay circuit responsive to the operation of said switch into its magnetizing position to apply at least one pulse of current of a magnetizing polarity to said coil from said source, said current pulse being adaptable to over-magnetize said magnet, a power selector operable to deliver variable increments of power from said source to said coil under the control of said relay control circuit, relay means in said relay control circuit automatically respon sive to the operation of said switch into its demagnetizing position to cause said power selector to apply a sequence of pulses of current of a demagnetizing polarity and of successively increasing increments of magnitude to said coil from said source, said sequence of pulses being adaptable to demagnetize said magnet to successively increasing extents, means automatically operative by said relay control circuit during the application of each demagnetizing pulse of said sequence to said coil and adaptable to cause said armature to be placed into contact with said contact, relay means in said relay control circuit automatically operative during the intervals before and after demagnetizing pulses of said sequence are applied to said coil and adaptable to apply to the winding of said test relay a test current of such a magnitude and polarity as would move said armature away from said contact when the permanent magnet bias is properly adjusted by said sequence, and means automatically operative by said control circuit and adaptable to detect the movement of said armature away from said contact.

4. A circuit for automatically adjusting the permanent magnet bias of a test relay including an energizing winding and a contact and a permanent magnet and a magnetic armature and movable in operable relation to said contact under the influence of the combination of the magnetic field produced by the energization of said winding and the magnetic field of said magnet, said circuit comprising a source of electric power, a manually operable switch having a magnetizing and a demagnetizing position, a magnetizing-demagnetizing coil adaptable to magnetize or demagnetize said test relay magnet, a power control relay circuit including a pulsing relay and responsive to the operation of said switch into its magnetizing position to apply at least one pulse of current of a magnetizing polarity to said coil from said source under the control of said pulsing relay, said current pulse being adaptable to over-magnetize said magnet, a power selector operative to deliver variable increments of power from said source to said coil under the control of said relay control circuit, means in said relay control circuit including said pulsing relay and a power selector control relay automatically responsive to the operation of said switch into its demagnetizing position to cause said power selector to apply a sequence of pulses of current of a demagnetizing polarity and of successively increasing increments of magnitude to said coil from said source under the control of said pulsing and selector control relays, said sequence of pulses being adaptable to demagnetize said magnet to successively increasing extents, means automatically operative by said control circuit during the aplication of each demagnetizing pulse of said sequence to said coil and adaptable to cause said armature to be placed into contact with said contact, means in said relay control circuit including a pair of relays and a current control automatically operative by said control circuit during the intervals before and after demagnetizing pulses of said sequence are applied to said coil and adaptable to apply to the winding of said test relay a test current of such a magnitude and polarity as would move said armature away from said contact when the permanent magnet bias is properly adjusted by said sequence, and means automatically operative by said control circuit and adaptable to detect the movement of said armature away from said contact.

5. A circuit for automatically adjusting the permanent magnet bias of a test relay including an energizing winding and a contact and a permanent magnet and a magnetic armature movable in operable relation to said contact under the influence of the combination of the magnetic field produced by the energization of said Winding and the magnetic field of said magnet, said circuit comprising a source of electric power, a manually operable switch having a magnetizing and a demagnetizing position, a magnetizing-demagnetizing coil adaptable to magnetize or demagnetize said test relay magnet, a power control relay circuit including a pulsing relay and responsive to the operation of said switch into its magnetizing position to apply at least one pulse of current of a magnetizing polarity to said coil from said source under the control of said pulsing relay, said current pulse being adaptable to overmagnetize said magnet, 21 power selector operable to deliver variable increments of power from said source to said coil under the control of said relay control circuit, relay means in said relay control circuit including said pulsing relay and a power selector control relay automatically responsive to the operation of said switch into its demagnetizing position to cause said power selector to apply a sequence of pulses of current of a demagnetizing polarity and of successively increasing increments of magnitude to said coil from said source under the control of said pulsing and selector control relays, said sequence of pulses being adaptable to demagnetize said magnet to successively increasing extents, means automatically controlled by said pulsing relay during the application of each demagnetizing pulse of said sequence to said coil and adaptable to cause said armature to be placed into contact with said contact, means in said relay control ircuit including a pair of relays and a variable test current source automatically controlled by said pulsing relay during the intervals before and after demagnetizing pulses of said sequence are applied to said coil and adaptable to apply to the winding of said test relay a test current of such a magnitude and polarity as would move said armature away from said contact when the permanent magnet bias is properly adjusted by said sequence, means automatically operative by said control circuit and adaptable to detect the movement of said armature away from said contact, and means in said relay control circuit responsive to the operation of said detecting means to disable said pulsing relay whereby the demagnetizing procedure is stopped.

6. A circuit for automatically adjusting the permanent magnet bias of a test relay including an energizing winding and two separate contacts and a permanent magnet associated with each contact and a magnetic armature attracted magnetically in opposite directions towards each contact by respective magnets and movable away from each respective contact under the influence of the combination of the magnetic field produced by the energization of said winding and the magnetic fields of said magnets, said circuit comprising a source of power, switch means having a magnetizing and a demagnetizing position, a magnetizing-demagnetizing coil adaptable to magne tize or demagnetize each of said test relay magnets, a power control circuit responsive to the operation of said switch means into its magnetizing position to apply at least one pulse of current of a magnetizing polarity to said coils from said source, said current pulse being adaptable to over-magnetize said magnets, variable means operable to deliver variable increments of power from said source to said coils under the control of said control circuit, means operative at respective odd and even times by said control circuit and adaptable to detect respective movements of said armature away from said odd contact and into contact with said even contact and away from said even contact and into contact with said odd contact, means automatically responsive to the operation of said switch means into its demagnetizing position and under the control of respective even and odd operations of said detecting means to cause said control circuit to control said variable means to apply respective odd and even sequences of pulses of current of a demagnetizing polarity and of successively increasing increments of magnitude to respective odd and even coils from said source, said sequence of pulses being adaptable to demagnetize respective odd and even magnets to successively increasing extents, means automatically operative by said control circuit during the application of each demagnetizing pulse of respective odd and even sequences to respective odd and even coils and adaptable to cause said armature to be placed into contact with respective odd and even contacts and said latter means automatically operative by said control circuit during the intervals before and after demagnetizing pulses of respective odd and even sequences are applied to respective odd and even coils and adaptable to apply to the winding of said test relay respective first and second test currents of such respective magnitudes and polarities as would move said armature respectively away from said odd contact and into contact with said even contact and away from said even contact and into contact with said odd contact when the permanent magnet bias of respective odd and even magnets is properly adjusted by respective odd and even sequences, and means responsive to immediate odd and even operations of said detecting means pursuant to respective immediately preceding even and odd operations of said detecting means to prevent any further demagnetizing sequences and adaptable to indicate completion of the adjustment of the permanent magnet bias of both magnets.

7. A circuit for automatically adjusting the permanent magnet bias of a test relay including an energizing winding and two separate contacts and a permanent magnet associated with each contact and a magnetic armature attracted magnetically in opposite directions towards each contact by respective magnets and movable away from each respective contact under the influence of the combination of the magnetic field produced by the energization of said winding and the magnetic fields of said magnets, said circuit comprising a source of power, switch means having a magnetizing and a demagnetizing position, a magnetizing-demagnetizing coil adaptable to magnetize or demagnetize each of said test relay magnets, a power control circuit responsive to the operation of said switch means into its magnetizing position to apply at least one pulse of current of a magnetizing polarity to said coils from said source, said current pulse being adaptable to over-magnetize said magnets, variable means operable to deliver variable increments of power from said source to said coils under the control of said control circuit, means operative at respective odd and even times by said control circuit and adaptable to detect the respective movements of said armature away from said odd contact and into contact with'said even contact and away from said even contact and into contact with said odd contact, means automatically responsive to the operation of said switch means into its demagnetizing position and under the control of respective even and odd operations of said detecting means to cause said control circuit to control said variable means to apply respective odd and even sequences of pulses of current of a demagnetizing polarity and of successively increasing increments of magnitude to respective odd and even coils from said source, said sequences of pulses being adaptable to demagnetize respective odd and even magnets to succe ssively increasing extents, means automatically operative by said control circuit during the application of each demagnetizing pulse of respective odd and even sequences to respective odd and even coilsand adaptable to apply to the winding of said test relay respective first andsec; 0nd reset currents of such respective magnitudes and polarities as would attract said armature into contact with respective odd and even contacts, means automatically operative by said control circuit during the intervals before and after demagnetizing pulses of respective odd and even sequences are applied to respective odd and even coils and adaptable to apply to the winding of said test relay respective first and second test currents of such respective magnitudes and polarities as would move said armature respectively away from said odd contact and into contact with said even contact and away from said even contact and into contact with said odd contact when the permanent magnet bias of respective odd and even magnets is properly adjusted by respective odd and even sequences, and means responsive to immediate odd and even operations of said detecting means pursuant to respective immediately preceding even and odd operations of said detecting means to prevent any further demagnetizing sequences and adaptable to indicate completion of the adjustment of the permanent magnet bias of both magnets.

8. A circuit for automatically adjusting the permanent magnet bias of a test relay including an energizing winding and two separate contacts and a permanent magnet associated with each contact and a magnetic armature attracted magnetically in opposite directions towards each contact by respective magnets and movable away from each respective contact under the influence of the combination of the magnetic field produced by the energization of said winding and the magnetic fields of said magnets, said circuit comprising a source of power, switch means having a magnetizing and a demagnetizing position, a magnetizing-demagnetizing coil adaptable to magnetize or demagnetize each of said test relay magnets, a power control circuit responsive to the operation of said switch means into its magnetizing position to apply at least one pulse of current of a magnetizing polarity to said coils from said source, said current pulse being adaptable to over-magnetize said magnets, variable means for each coil and operable to deliver variable increments of power from said source to the associated coil under the control of said control circuit, means automatically responsive to the operation of said switch means into its demagnetizing position to cause said' control circuit to control a first variable means to apply a first sequence of pulses of current of a demagnetizing polarity and of successively increasing increments of magnitude to one of said coils from said source, said first sequence of pulses being adaptable to demagnetize the associated magnet to successively increasing extents, means automatically operative by said control circuit during the application of each demagnetizing pulse of said first sequence to said one coil and adaptable to apply to the winding of said test relay a first reset current of such a magnitude and polarity as would attract said armature into contact with the one contact, means automatically operative by said control 25 circuit during the intervals before and after demagnetizing pulses of said first sequence are applied to said one coil and adaptable to apply to the winding of said test relay a first test current of such a magnitude and polarity as would move said armature away from said one contact and into contact with the other contact when the permanent magnet bias of said one magnet is properly adjusted by said first sequence, means automatically operative at respective odd and even times by said control circuit and adaptable to detect respective movements of said armature away from said one contact and into contact With said other contact and away from said other contact and into contact with said one contact, means automatically responsive to an odd operation of said detecting means at the end of said first sequence to cause said control circuit to control the second variable means to apply a second sequence of pulses of current of a demagnetizing polarity and of successively increasing increments of magnitude to the other of said coils from said source, said second sequence of pulses being adaptable to demagnetize the other of said magnets to successively increasing extents, means automatically operative by said control circuit during the application of each demagnetizing pulse of said second sequence to said other coil and adaptable to apply to the winding of said' test relay a second reset current of such a magnitude and polarity as would attract said armature into contact with the other contact, means automatically operative by said control circuit during the intervals before and after demagnetizing pulses of said second sequence are applied to said other coil and adaptable to apply to the winding of said test relay a second test current of such a magnitude and polarity as would move said armature away from said other contact and into contact with said one contact when the permanent magnet bias of said other magnet is properly adjusted by said second sequence, means eifeetive in response to succeeding respective even and odd operations of said detecting means at the end of succeeding respective even and odd sequences to permit said control circuit to control said first and second variable means alternately to apply succeeding respective odd and even additional sequences of demagnetizing pulses of still increasing magnitude to respective coils from said source, said additional sequences of pulses being adaptable to succes sively further demagnetize said magnets, and means responsive to immediate odd and even operations of said detecting means pursuant to respective immediately preceding even and odd operations of said detecting means to prevent any further demagnetizing sequences and adaptable to indicate completion of the adjustment of the permanent magnet bias of both magnets.

9. A circuit for automatically adjusting the permanent magnet bias of a test relay including an energizing winding and two separate contacts comprising permanent magnets and a magnetic armature attracted magnetically in opposite directions towards each contact by respective magnets and movable away from each respective contact under the influence of the combination of the magnetic field produced by the energization of said winding and the magnetic fields of said magnets, said circuit comprising a source of power, a manually operable switch having a magnetizing and a demagnetizing position, a magnetizing-demagnetizing coil adaptable to magnetize or demagnetize each of said test relay magnets, a power control relay circuit responsive to the operation of said switch into its magnetizing position to apply at least one pulse of current of a magnetizing polarity to said coils from said source, said current pulse being adaptable to over-magnetize said magnets, a power selector for each coil and operative to deliver variable increments of power from said source to the associated coil under the control of said relay control circuit, relay means in said relay control circuit automatically responsive to the operation of said switch into its demagnetizing posi- 26 tion to cause a first power selector to apply a first sequence of pulses of current of a demagnetizing polarity and of successively increasing increments of magnitude to one of said coils from said source said first sequence of pulses being adaptable to demagnetize the associated magnets to successively increasing extents, relay means in said relay control circuit automatically operative during the application of each demagnetizing pulse of said first sequence to said one coil and adaptable to apply to the winding of said test relay a first reset current of such a magnitude and polarity as would attract said armature into contact with the one contact, relay means in said relay control circuit automatically operative during the intervals before and after demagnetizing pulses of said first sequence are applied to said one coil and adaptable to apply to the winding of said test relay a first test current of such a magnitude and polarity as would move said armature away from said one contact and into contact with the other contact when the permanent magnet bias of said one magnet is properly adjusted by said first sequence, relay means in said relay control circuit automatically operative at respective odd and even times and adaptable to detect respective movements of said armature away from said one contact and into contact with said other contact and away from said other contact and into contact with said one contact, relay means in said relay control circuit automatically responsive to an odd operation of said detecting means at the end of said first sequence to control the second power selector to apply a second sequence of pulses of current of a demagnetizing polarity and of successively increasing increments of magnitude to the other of said coils from said source, said second sequence of pulses being adaptable to demagnetize the other of said magnets to successively increasing extents, relay means in said relay control circuit automatically operative during the application of each demagnetizing pulse of said second sequence to said other coil and adaptable to apply to the winding of said test relay a second reset current of such a magnitude and polarity as would attract said armature into contact with the other contact, relay means in said relay control circuit automatically operative during the intervials before and after demagnetizing pulses of said second sequence are applied to said other coil and adaptable to apply to the winding of said test relay a second test current of such a magnitude and polarity as would move said armature away from said other contact and into contact with said one contact when the permanent magnet bias of said other magnet is properly adjusted by said second sequence, relay means in said relay control circuit effective in response to succeeding respective even and odd operations of said detecting means at the end of succeeding respective even and odd sequences to control said first and second power selectors alternately to apply succeeding respective odd and even additional sequences of demagnetizing pulses of still increasing magnitude to respective coils from said source, said additional sequences of pulses being adaptable to successively further demagnetize said magnets, and relay means in said relay control circuit responsive to immediate odd and even operations of said detecting means pursuant to respective immedately preceding even and odd operations of said detecting means to prevent any further demagnetizing sequences and adapt able to indicate completion of the adjustment of the permanent magnet bias of both magnets.

10. Acircuit for automatically adjusting the perman'ent magnet bias of a test relay including an energizing winding and two separate contacts comprising permanent magnets and a magnetic armature attracted magnetically in opposite directions towards each contact by respective magnets and movable away from each respective contact under the influence of the combination of the magnetic field produced by the energization of said winding and the magnetic fields of said magnets, said 27 circuit comprising a source of power, a manually operable switch having a magnetizing and a demagnetizing position, a magnetizing-demagnetizing coil adaptable to magnetize or demagnetize each of said test relay magnets, a power control relay circuit including a relay controlled by said source to oscillate at a desired rate and including a power relay controlled by said oscillating relay, said relay control circuit responsive to the operation of said switch into its demagnetizing position to apply at least one pulse of current of a magnetizing polarity from said source to said coils under the control of said power relay said current pulse being adaptable to over-magnetize said magnets a power selector for each coil and operable under the control of said relay control circuit to deliver variable increments of power from said source to the associated coil through the agency of said power relay, a dual-condition steering relay in said relay control circuit automatically responsive to the operation of said switch into its demagnetizing position to assume one of its positions thereby to cause a first power selector to apply a first sequence of pulses of culrent of a demagnetizing polarity and of successively increasing increments of magnitude to one of said coils from said source under the control of said power relay said first sequence of pulses being adaptable to demagnetize the associated magnet to successively increasing extents, a group of test current relays controlled by said relay control circuit to at times assume one of four different conditions of operated and released relays of said group, said group automatically operative by said control circuit into a first of its conditions during the application of each demagnetizing pulse of said first sequence to said one coil and adaptable to apply to the winding of said test relay a first reset current of such a magnitude and polarity as would attract said armature into contact with one of said contacts, said group automatically operative by said control circuit into a second of its conditions during the intervals before and after demagnetizing pulses of said sequence are applied to said one coil and adaptable to apply to the winding of said test relay a first test current of such a magnitude and polarity as would move said armature away from its one contact and into contact with the other contact when the permanent magnet bias of said one magnet is properly adjusted by said first sequence, a detecting relay in said relay control circuit automatically operative at respective odd and even times and adaptable to detect respective movements of said armature away from said one contact and into contact with said other contact and away from said other contact and into contact with said one contact, said dualcondition steering relay automatically responsive to an odd operation of said detecting means at the end of said first sequence to control the second power selector to apply a second sequence of pulses of current of a demagnetizing polarity and of successively increasing increments of magnitude from said source to the other of said coils through the agency of said power relay said second sequence of pulses being adaptable to demagnetize the other of said magnets to successively increasing extents, said group automatically operative by said control circuit into a third condition during the application of each demagnetizing pulse of said second sequence to said other coil and adaptable to apply to the winding of said test relay a second reset current of such a magnitude and polarity as would attract said armature into contact with the other contact, said group automatically operative by said control circuit into its fourth condition during the intervals before and after demagnetizing pulses of said second sequence are applied to said other coil and adaptable to apply to the winding of said test relay 9. second test current of such a magnitude and polarity as would move said armature away from said other contact and into contact with said onecontact when the permanent magnet bias of said other magnet is properly adjusted by said second sequence, means including said relay control circuit and said steering relay and said group of relays efiective in response to succeeding respective even and odd operations of said detecting means at the end of succeeding respective even and odd sequences to control said first and second power selectors alternately to'apply succeeding respective odd and even additional sequences of demagnetizing pulses of still increasing magnitude from said source to respective coils through the agency of said power relay, said addition sequences of pulses being adaptable to successively further demagnetize said magnets, and relay means including said detecting relay means and responsive to immediate odd and even operations of said detecting means pursuant to respective immediately preceding even and odd operations of said detecting means to dis-able said oscillating relay thereby to prevent any further demagnetizing sequences and adaptable to indicate completion of the adjustment of the permanent magnet bias of both magnets.

11. A circuit for automatically adjusting the permanent magnet bias of a test relay including an energizing winding and a contact and a permanent magnet and a magnetic armature movable in operable relation to said contact under the influence of the combination of the magnetic field produced by energization of said winding and the magnetic field of said magnet, said circuit comprising a source of electric power, switch means having a demagnetizing position, a coil adaptable to magnetically influence said test relay magnet, a power control circuit, selector means operable to deliver increments of power from said source to said coil under the control of said control switch, means responsive to the operation of said switch means into its demagnetizing position to cause said control circuit to control said selector means to apply at least one pulse of current of a demagnetizing polarity to said coil from said source, means operative by said control circuit during the application of said demagnetizing pulse to said coil and adaptable to cause said armature to be placed into contact with said contact and operative by said control circuit after said demagnetizing pulse is applied to said coil for applying to the winding of said test relay a test current of such a magnitude and polarity as would move said armature away from said contact when the pei manent magnet bias is properly adjusted, and means operative by said control circuit and adaptable to detect the. movement of said armature away from said contact.

12. In a circuit for automatically adjusting the permanent magnet bias of a test relay including an energizing winding and a contact and a permanent magnet and a magnetic armature movable in operable relation to said contact under the influence of the combination of the magnetic field produced by the energization of said winding and the magnetic field of said magnet, said circuit comprising a source of electric power, switch means having a demagnetizing position, a coil adaptable to magnetically influence said test relay magnet, a power control circuit responsive to the operation of said switch means into its magnetizing position to apply at least one pulse of current of a magnetizing polarity to said coil from said source, said current pulse being adaptable to over-magnetize said magnet, variable means operable to deliver variable increments of power from said source to said coil under the control of said control circuit, means automatically responsive to the operation of said switch means into its demagnetizing position to cause said control circuit to control said variable means to apply a sequence of pulses of current of a demagnetizing polarity to said coil from said source, said sequence of pulses being adaptable to demagnetize said magnet, means automatically operative by said control circuit during the application of each demagnetizing pulse of said sequence to said coil and adaptable to cause said arma-

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