US2049622A - Remote control system - Google Patents

Description

1936- R. G. RICHARDSON ET AL 2,049,622

REMOTE CONTROL SYSTEM Filed March 30, 1923 3 Sheets-Sheet 1 l'zTfiTfis EuunsgE- Emhardsun -Jnhu 'I. Bellamy HIT y:

1936- R. cs. RICHARDSON ET AL 2,049,622

REMOTE CQNTROL SYSTEM Filed March 50, 1923 3 Sheets-Sheet 2 HIT.-

Irzusn urs Bmh5ru5un Jul-Ln I Bellamv r Z Q E E Aug. 4', 1936.

R. G. RICHARDSON ET AL REMOTE CONTROL SYSTEM Filed March 30,- 1923 3 Sheets-Sheet Imren Ursa haw s Inn-- J0 4%.

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Patented Aug. 4, 1936 UNITED STATES REMOTE CONTROL SYSTEM Rodney G. Richardson and John I. Bellamy, Chicago, Ill., assignors, by mesne assignments, to Associated Electric Laboratories, Inc., Chicago, Ill., a corporation oi. Delaware Application March 30. 1923, Serial No. 628,723

12 Claims.

The present invention relates to remote control systems in general, but more particularly to such remote control systems as are suitable for use in connection with remotely controlled electric substations; and as regards some of its features, may be considered an improvement on the co-pending application of Nelson, filed November 16, 1921, Serial No. 515,664, Patent No. 1,765,538, dated June 24, 1930.

The broad general object of this invention is the provision of suitable circuit arrangements for use in such a remote control system whereby the chances for error are reduced to a minimum.

Specifically, one object of the invention is to produce circuit arrangements such that the despatcher who operates the distant apparatus by means of the remote control system is enabled to check the position or setting of the distant controlling switch before the operation he is about to bring about takes place; and such that the despatcher can restore the distant control switch to normal without operating the device corresponding to the setting of said control switch, in case he discovers by means of the above mentioned checking arrangements that the distant control switch is set-in some position other than that in which he intended to set it.

Another object is to produce suitable circuit combinations whereby the despatcher is enabled to check the position of any piece of apparatus at the substation either as a matter of routine or in case he suspects that the usual lamp indication is incorrect.

The other objects, which have to do mainly with the detailed circuit arrangements, will appear from time to time, and will be apparent as the specification is further perused.

Referring now to the drawings comprising Figs. 1, 2, and 3, the apparatus shown in Fig. 1 is located in the despatchers oiiice and is connected to the apparatus in the substation by means of the two pairs of conductors 41 and 48, and 49 and 50, respectively. The apparatus shown in Figs. 2 and 3 is located in the substation.

Figure 1 shows the calling device CD by means of which the despatcher operates the control switch in the distant substation. This drawing shows also the switch D which is controlled from the substation and which effects the lighting and extinguishing of the associated signal lamps such as L and L Figure 2 shows the control switch E, located in the substation, which is operated by the calling comprising relays 3!", 302, and 303, of which two are provided for each starter, circuit breaker, etc. in the substation. These relays control the operation of the switch, D, Fig. 1, through the medium of the relay group RG and the counting switch CS.

The substation shown is assumed to be provided for the purpose of transforming three-phase alternating current energy which is supplied over conductors 215-2 ll, inclusive, Fig. 2, into direct current energy which is supplied to the bus-bar 260. The motor of the motor generator MG is operated in the well-known manner by the threephase alternating current and the associated generator supplies the'direct current.

The motor generator MG may be placed in service by operating the starter S so as to bring the unit up to running speed, and then closing the circuit breaker CB which connects the generator to the bus-bar 260.

The signal operating switch D, Fig. 1, and the controlling switch E, Fig. 2, are mechanically identical with each other, and are of a type of automatic switch disclosed in Automatic Telephony, second edition, a book published by McGraw-Hill Book Company, 370 Seventh Avenue, New York, N. Y. A photograph of this type of switch is shown on page 53 of this publication and a skeleton drawing is shown on page 58. A description accompanies the photograph and describes how this type of switch, which is a switch having a step by step vertical movement and a step by step rotary movement, operates. The circuits of the switches D and E are shown complete and will be described fully hereinafter.

The calling-device CD, Fig. 1, may be of any one of several well-known types, but for the purpose of illustration, is assumed to be of the type shown on pages 40 and 41 of Automatic Telephony above referred to. The function of this calling device, as stated hereinbefore, is to control the switch E in the substation over the conductors 41 and 48.

The various pieces of switching apparatus in the substation, such as the starter S and the circuit breaker CB which are shown, may be operated at the will of the despatcher through the medium of the controlling switch E. This operation is effected through the contacts in the bank of wiper 86, as will be explained hereinafter.

The starter S is arranged as usual to be returned to normal in case the alternating current supply fails, and the circuit breaker CB is adapted to be thrown out automatically in case the load on the generator of the motor generator unit MG becomes too great.

In order that the despatcher may be kept informed at all times of the respective positions of 60 the various pieces of switching apparatus, each piece of switching apparatus controls the supply of ground potential to two conductors, such as the conductors H8 and H8 associated with the starter S, and I20 and I2I associated with the circuit breaker CB. It will be noted that one of the associated conductors is grounded in case the starter, or circuit breaker as the case may be, is at normal while the other conductor is grounded in case it is operated. It is over these conductors II8--I2I, inclusive, that the various socalled call sending relay sets, such as the one comprising relays Mil-308, inclusive, are controlled. 'Each time the ground connection is shifted from one of the above mentioned conductors to the other, the call sending relays associated with the newly grounded conductor operate and cause, through the medium of the calling sending relay group RG and the counting switch CS, the signal operating switch D in the despatchers ofllce to be set into a position corresponding to the new position of the operated device in the substation. This results in one of the despatchers lamps becoming extinguished and another becoming lighted to give to the despatcher the correct indication.

The counting switch CS, Fig. 3, comprises two semi-circular rows of contacts which are wiped over by the wipers I18 and I19 under the control of the stepping magnet I16. The stepping magnet I16 operates the wipers I18 and I18 by rotating the common spindle to which the two wipers are rigidly secured. These wipers are operated step by step as the magnet is alternately energized and deenergized, being advanced upon the deenergization of stepping magnet I16 rather than upon the energization. One mechanical embodiment of such a switch is shown on page 51 of Automatic Telephony hereinbefore referred to.

It is to be understood that while several batteries are indicated in each of the drawings, there is no need ofhaving more than one battery in the substation and one battery in the despatchas office, the several batteries being shown for the sake of simplicity.

Although the starter S and the circuit breaker CB, Fig. 2, are the only pieces of substation switching equipment shown, it will be understood that in actual practice a great many more similar devices will be found in each substation. In

view of the fact that substations and their eouipment are well known, no attempt has been made to show the substation layout in any great detail, only so much being shown as will be needed to describe. and explain the various features of the present invention.

It has been assumed that there are several other units of switching apparatus in the substation, which may or may not be similar to the starter S and the circuit breaker CB. It is assumed further that each switching unit has its own call sending relays such as the relays shown in the upper part of Fig. 3, which relays, as before stated, are associated with the starter S and the circuit breaker CB. It is assumed that some of these other sets of relays have contacts connected in series in the two chain circuits extending through the contacts of the relays shown and being connected in the dotted portions of these circuits. It is assumed also that the remaining ones of the other relays are located to the right of the relays shown in the upper part of Fig. 3 as indicated by the arrowheads placed on the ends of the conductors terminated at the right-hand edge of'the drawing.

The apparatus, having been described in general, will now be described in connection with a detailed description of its operation. For this purpose, it will be assumed that the despatcher decides to put the motor generator MG into operation. In order to do' so, the first thing the despatcher must do is to effect the operation of the starter S. Accordingly, the despatcher operates the key K associated with the calling device CD, thereby closing .a circuit for the slow to pull up relay I8. This relay is made slow to pull up by placing the copper collar on the armature end of the core rather than on the opposite end of the core. This is denoted in the drawings by the position of the copper collar on the upper end of relay I6, which; is assumed to be the armature end. Relay I6, therefore, does not operate its armature immediately. Relay I1, which is a slow-acting relay also, energizesv immediately, however, owing to the fact that its copper collar is on the end of the core away from the armature. Upon energizing, relay I.1 opens a point in the circuit of the lower winding of relay 24 at armature 2I and at armature 28 closes a bridge across the conductors 41 and 48 and including the contacts I4 of the calling device CD.

Before the effect produced by the closing of this bridge across the conductors 41 and 48 is considered, the description of the operation of relays I6 and I1 will be completed. Relay I6 energizes a moment after the energization of relay I1 opens the circuit of relay I1 at armature I8 closes a point in the circuit of the lower winding of relay 24 at armature I9; and at armature I8 places a shunt around armature 20 and its working contact. A moment later, slow-acting relay I1 deenergizes; opens the previously closed point in the bridge across conductors 41 and 48, leaving said bridge closed through armature I8 and its working contact; andat armature 2I completes a circuit for the lower winding of relay 24 including the normally closed contacts controlled by armature 39' of relay 28 and armature I9 and its working contact of relay I6. Relay 24 energizes over this circuit and prepares a locking circuit for itself at armature 3I; disconnects wiper 23 and connects up wiper 22 at armature 32; opens a point in the circuit of the signal relay ID at armature/ 30'; and at arma'ure 30 shifts the wiper circuit from the local locking conductor to the flasher F. The net result of the energization of relay 24 is that the circuits of the switch D are shifted so that the said switch.

D will operate correctly as a checking switch when the despatcher operates the substation switch E as will be explained subsequently. It is necessary to make this circuit change at this time owing to the fact that the switch D is normally connected in such a. way that when it is operated one of the lamps of a set is extinguished and another lighted as fully explained later.

The energization of relay 24 was delayed as pointed out above in order to permit any call which may have started in the substation, but which has not reached the stage at which relay 28 of the switch D has energized, to be vcompleted before the energization of relay 24 takes place. The above mentioned delay while only momentary is long enough to assure that any call which is already started Will have time to proceed far enough to operate the release relay 28 of the 75 switch D, while other calls are prevented from starting after the closure of the bridge across conductors 41 and 48 as will be explained fully hereinafter.

In the substation line relay 60 of the switch E energizes in response to the above mentioned closure of the bridge across conductors 41 and-'48 in the despatchers oilice and closes a circuit f or release relay 6|. Relay 6I' thereupon energizes; and removes the ground from conductor I24 at This results in ground being re-' armature 68. moved from the chain circuit passing through armature 306 and its resting contact of relay 302 and the corresponding armatures on the following relays. This has the effect of preventing any more calls from starting until conductor I24 is again grounded. The way in which this operates to prevent calls from being started will be appreciated perhaps more fully as the description progresses.

As a further result of the energization of relay 6|, it prepares a circuit for the lower winding of switching relay 64 at armature 67, and at armature 69 opens a point in the circuit of release magnet 8! and prepares a circuit for vertical magnet 80.

Having operated the key K, as above pointed out, the despatcher now manipulates the calling device CD in accordance with the first digit in the number assigned for operating the starter S. It will be assumed that this number is IIand, accordingly, the calling device is turned for the digit I and produces one interruption in the bridge across conductors 41 and 48. When this occurs, the line relay 60 of the switch E deenergizes once momentarily, thereby sending an impulse of current to vertical magnet over the following circuit: From ground by way of armature 66 and its resting contact, armature 69 and its working contact, contact of off normal spring 84 and said spring, slow-acting series relay 62, and vertical magnet 80 to battery. By the operation of vertical magnet 80, the switch shaft is raised one step and brings the wipers and 86 opposite the first level of bank contacts. Relay 62 is energized in series with vertical magnet 80 and is made slow-acting so as to retain its armature attracted and maintain its own circuit and that of vertical magnet 80 intact after the ofi normal springs have shifted as they do on the first vertical step. The last part of the impulse sent to vertical magnet 80, therefore, traverses the normally open contacts controlled by off normal spring 84, and armature I0 and its working contact instead of the contact of oil normal spring 84 and said spring. In cases when it is desired to raise the shaft of the switch E to some other level, a greater number of impulses are sent and all of them after the first are transmitted over the same path as the last part of the first impulse' Soon after the termination of the above mentioned impulse to vertical magnet 86, slow-acting series relay 62 deenergizes and transfers the operating circuit from the vertical to the rotary magnet.

When the despatcher manipulates the dial of the calling device CD in accordance with the second digit in the desired number, one interruption is again produced in the circuit of line relay 60, whereupon said line relay 60 deenergizes and sends an impulse of current to the rotary magnet 82 over the following circuit: From ground by way of armature 66 and its resting contact,

armature 68 and its working contact, normally open contacts controlled by oil normal spring 84, armature I0 and its resting contact, armature I8 and its resting contact, and rotary magnet 82 to battery. Upon receiving this impulse, rotary magnet 82 energizes and steps the switch wipers 86'and into engagement with the bank con- 1 tacts Bland 88, respectively, which are the first set of bank contacts in the selected level. Relay 631 isfenergized in multiple with rotary magnet '82 and maintains the circuit of the lower winding of switching relay 64 open until the switch wipers have come to rest on the selected contacts. Relay 63 'is made slow-acting so that it will re--' tain its armature attracted between succcessive impulses when the number of rotary steps taken exceeds one. Shortly after the termination of the rotary movement, relay 63 deenergizes, thereby connecting up the lower Winding of relay 64 at armature 12. When this occurs, relay 64 and relay 303, Fig. 3, energizes in series over the following circuit: From ground by way of armature I59 of relay MI in the relay group RG, Fig. 3, and its resting contact, armature I41 and its resting contact, conductor I23, armature 61 and its working contact, resting contact of armature I2 and said armature, lower winding of switching relay 64, normally closed contacts controlled by armature I6, wiper 85, bank contact 81, conductor IIO, resting contact of armature 304 of relay 3M and said armature, and relay 303 to battery. Relay 64 of the switch E and relay 303 energize in series overthe above traced circuit. Due to its adjustment relay 64 energizes first and closes a locking circuit for its upper winding at armature I5, which locking circuit includes the working contact of armature 68 and said armature; disconnects rotary magnet 82 at armature, I8; prepares a circuit for relay 65 at armature 11; places ground on conductor I22 at armature 14, thereby preparing a circuit for relay I35 of the relay group RG which will be closed subsequently; and at armature I6 short circuits and then opens its own lower winding, thereby applying direct ground to wiper .85.

Relay 303, Fig. 3, upon energizing over the above traced circuit, closes a locking circuit for itself at armature 301 which includes the normally closed contacts controlled by armature I64 of relay I43 in the relay group RG. As a further result of the energization of relay 303, it connects the first impulse stop conductor I8I to the first digit and second digit stop conductors I28 and I21 at armatures 309 and 3l0, respectively, thereby preparing the circuits for sending in the number II to the despatcher; prepares a circuit for relay 30I at armature 308; and at armature 3II places ground on conductor I26, thereby closing a circuit for relays I40 and MI in multiple. Relays I40 and I4I energize, but the energization of relay I4I does not have any particular function at this time. Relay I40, upon energizing, places ground on conductor I 29, thereby completing the circuit of relay 30I by way of the working contact of armature 308 and .1.

said armature. Relay 30I thereupon energizes but does not have any particular function at this time. As a further result of the ground potential being placed on conductor I26 in response to the energization of relay 303, a circuit is closed by way of armature I 54 and its resting contact for relay I42. Relay I42, upon energizing, closes a bridge across conductors 49 and 50 at armature I62 includingarmatures I65 and I6! and their resting contacts in multiple; places ground on armature I84 at armature I88; and at armature I8I closes a circuit for relay I48. Relay I43, upon energizing, places a multiple ground on conductor I28 at armature I83, and at armature I84 shirts the locking circuit of relay 383 so as to Include the working contact of armature I84 and said armature and armature I68 and its working contact instead or the normally closed contacts controlled by armature I84. This is done so as to permit a release of relay 383 at the proper time, as will be explained subsequently.

In the despatcher's oflice line relay 29 of the switch D energizes in response to the closure of the above mentioned bridge across conductors 49 and 68 in the relay group RG, and closes a circuit for release relay 28 at armature 4I. Upon energizing, release relay 28 opens a point in the circuit of release magnet 44 and prepares a circuit for vertical magnet 41 at armature 48; connects the flasher F to wiper 22 at armature 38; and at armature 39' closes a locking circuit, for

.the upper winding of relay 24 by way or armature 3I and its working contact and opens the circuit of the lower winding 0! the said relay 24. The switch D is now in readiness to be operated under the control of the sending equipment in the substation.

Returning now to the relay group R6, as a still further result of the ground potential being placed on conductor I26 as described hereinbefore, a circuit is completed for the sending relay I44 by way of the armature I54 and its resting contact, resting contact of armature I69 and said armature, sending relay I44, and the constantly rotating interrupter I to battery. Sending relay I44 now starts to vibrate under the control of the interrupter I. Upon the first effective energization of relay I 44, a circuit is completed for stepping magnet I16 of the counting switch CS at armature I66, whereupon said magnet I16 energizes and attracts the armature I11, thereby causing the associated pawl to engage another notch in the wiper driving ratchet wheel. Upon the next deenergization of relay I44, stepping magnet I16 deenergizes also on account of its circuit being opened at armature I66, and upon armature I11 being retracted the wipers I18 and I19 are advanced into engagement with the first set of their bank contacts. When wiper I18 comes into engagement with its first associated bank contact, it closes a circuit for pick-up relay I45. Pick-up relay I45 thereupon energizes and removes a shunt from around the armature I65 of relay .I44 and its resting contact at armature I61 so as to render each of the subsequent energizations of relay I 44 effective in interrupting the bridge across conductors 49 and 58.

Upon the next energization of relay I44, the bridge across conductors 49 and 58 is opened at armature I65 and stepping magnet I16 of the counting switch CS is energized again. Upon the subsequent deenergization of sending relay I44, the bridge across conductors 49 and 50 is again closed and the circuit of stepping magnet I16 is opened, whereupon the wipers I18 and I19 are advanced into engagement with the second set of associated bank contacts. Since the number to be called is 11 and the first digit of that number is 1, it is now necessary to terminate the first digit. That being the case, the first impulse stop conductor I8I is connected to the first digit stop conductor I28 through armature 369 and its working contact, and ground is accordingly extended to the second contact in the bank of wiper I19, thereby energizing stop relay circuit of stepping magnet I 18 and the circuit I48. Upon energizing, stop relay I48 opens the circuit of sending relay I44 at armature I88; closes a-locking circuit for itself at armature I 19'; and at armature I1I connects stepping magnet I18 to wiper I18 through interrupter contacts I15. Stepping magnet I18 accordingly operates in a buzzer-like manner and rotates the wipers I18 and I88 step by step until they pass of! the last set of bank contacts, thereby opening the oi the slow-acting relay I45. Relay I45, being slow-acting, does-not deenergize immediately.

Counting relay I38 is energized in multiple with slow-acting relay I48 through armature I58 and its resting contact and armature I52 and its resting contact. Upon energizing, counting relay I88 closes a locking circuit for itseli through counting relay I31 at armature I58. This locking circuit does not become effective, howe'ver, untilthe initial circuit is broken and relay I31 is not energized at this time owing to the fact that it is grounded at both terminals.

Upon deenergizing after an interval, slow-acting relay I45 replaces the. shunt around annature I66 and its resting contact of sending relay I44 at armature I61 and at armature I68 opens the locking circuit of stop relay I46 and also the initial circuit of counting relay I 36. When this occurs, the locking circuit of counting relay I36 through counting relay I31 becomes effective andrelay I31 energizes in series with relay I36; opens a still further point in the initial circuit of relay I36 and prepares a circuit for counting relay I38 at armature I52; and at armature I 5| disconnects ground from the first digit stop con- 3 ductor I28 and places ground on the second digit stop conductor I 21.

Upon deenergizing, relay I46 opens a still further point in its locking circuit at armature I10; disconnects stepping magnet I16 from Wiper I18 4 at armature HI; and at armature I69 again con nects up sending relay I44,

Relays I44 and I46 and the counting switch CS now repeat the above described operations with the result that the second digit 1 is sent 4 out in the same manner as the. first digit 1 except. that the stop relay I46 is energized in the second case from the second digit stop conductor I21 and through the working contact of armature I5I instead of from the first digit stop con- 5 ductor I 28 as in the first case.

Upon the circuit being closed for stop relay I46 the second time, relay I46 energizes with the hereinbefore described results, and also a circuit is closed for counting relay I38 in multiple with 5 relay I46 and in series with armature I56 and its resting contact and armature I52 and its working contact. Upon energizing, relay I38 closes a locking circuit for itself through counting relay I39, which locking circuit does not be- 6 come efiective until the initial circuit of relay I38 is opened. When the initial circuit of counting relay I38 and the circuit of relay I46 are opened upon the deenergization of relay I45 after the termination of the second digit 1, the locking 6 circuit for relay I38 through the counting relay I39 becomes efiective and counting relay I39, upon energizing, opens the circuit of relays I42 and I 44 at armature I54; opens another point in the initial circuit of relay I38 at armature I56; and at armature I55 closes a circuit for relay I35 as follows: From ground by way of the working contact of armature 14 of the switch E and said armature, resting contact of armature 1I and said armature, conductor I22, armature I55 75 and its working contact, and relay I35 to battery. Upon energizing, relay I35 closes a locking circuit for itself at armature I48; disconnects conductor I23 from the resting contact of armature I59 of relay I4I at armature I41; and at armature I49 places a multiple bridge across conductors 49 and 50 so as to hold up the switch D in the despatchers ofiice for a purpose to be explained hereinafter.

As the result of the circuit of slow-acting relay I42 being opened, this relay deenergizes after an interval and opens the initial bridge across conductors 49 and 50 .at armature I62, leaving said bridge closed by relay I 35; opens the circuit of slow-acting relay I43 at armature SI; and at armature I60 opens the locking circuit of relay 303. Relay I43, beingslow-acting, remainsenergized for an interval after its circuit is opened, and maintains the locking circuit of relay 303 open at the normally closed contacts controlled by armature I64 long enough to permit relay 303 to deenergize. Upon deenergizing, relay 303 opens a further point in its locking circuit and closes a point in the chain circuit at armature 301; removes ground from conductor I26 at armature 3| I, leaving said conductor grounded at armature I63 of relay I43; and at armature 30B opens the circuit of relay 30I. Relay 30I, upon deenergizing, prepares a circuit for relay 302 at armature 305, and at armature 304 closes a point in the initial energizing circuit of relay 303 through wiper-85 of the switch E. This circuit is not completed and relay 303 does not energize again at this time owing to the fact that ground has been removed from conductor I23 at armature I59 of relay I M as explained hereinbefore, thereby removing ground from wiper 85.

After an interval slow-acting relay I43 deenergizes, thereby replacing ground on conductor I25 at the normally closed contacts controlled by armature I64 and removing ground from conductor I26 at armature I63, whereupon relays I36-I4I, inclusive, deenergize, leaving the relays in the relay group RG all deenergized with the exception of the holding relay I35 which is locked up switch E.

The operation of the switch D in the despatchers oflice in response to the calling of the number I I by the call sending equipment in the substation as described above will now be taken up. When line relay 29 deenergizes in response to the first interruption representing the first digit I in the number, it closes a circuit for vertical magnet 41 by way of armature 40 and its working contact, contact of off normal spring 46 and said spring, and series relay 21. Vertical magnet 41 operates in the same manner as the vertical magnet 80 of the switch E as explained before and raises the switch shaft one step, carrying the switch wipers 22 and 23 opposite the first level of bank contacts. Slow-acting series relay 21 is energized in series with vertical magnet 41 and performs the same function as series relay 62 of the selector E hereinbefore described. After the termination of the impulse sent to the vertical magnet, series relay 21 deenergizes and transfers the operating circuit to the rotary magnet 42.

In response to the interruption in its circuit representing the second digit I in the number I I, relay 29 deenergizes and sends an impulse of current to rotary magnet 42 by way of armature 40 and its working contact, normally open contacts controlled by off normal spring 46, armature 38 and its resting contact, and armature 36 and its resting contact. Rotary magnet 42 responds to this impulse of current by stepping the switch wipers 22 and 23 into engagement with the first set of bank contacts 8 and 9 in the first level. Slow-acting relay 26 is energized in multiple with rotary magnet 42 and maintains the switch wiper disconnected during the rotary movement. Upon deenergizing, at the termination of the rotary movement, slow-acting r ay 26 connects up wiper 22 at armature 31', thereby completing a circuit for the lamp IF traceable from ground through the flasher F, spring 30 and its working contact, springs 39, 31, lower winding of relay 25, through the normally closed contacts controlled by springs 35,'spring 32 and its make contact, wiper 22 and contact 9, through the lamp L to grounded battery. The lamp L3 accordingly starts'fiashing so as to attract the attention of the despatcher and inform him that that is the lamp corresponding to the set posi-' tion of the switch E in the substation. The rotary magnet cut-ofi relay 25 energizes in series with the lamp L shorts its lower winding at armature 35; locks itself at armature 34 over a circuit including the upper winding of relay 25, armature 34 and its make contact, armature 39' and its make contact to ground; and at armature 36. disconnects rotary magnet 42 and relay 26 from the operating circuit so as to prevent their unnecessary operation during the subsequent release of the switch D.

In order to facilitate the explanation, it will be assumed for the time being that due to an error by the despatcher in operating his calling device CD or due to a false operation of the switch E, Fig. 2, the said switch E landed upon a set of contacts other than the first set in the first level as assumed hereinbefore. That being the case the call sending mechanism at the substation fails to operate the switch D or else causes the switch D to be set on a set of contacts other than the ones with which the lamp I. is associated. Whether the call sending mechanism responds or not depends upon whether the conductor associated with the contact on which the wiper 05 of the' switch E actually lands is connected through to the associated call sending relay such as 303 for'example (see conductor H0) or is disconnected by the associated cut-ofl. relay such as 30I for example (see conductor III). In this case no lamp is flashed or else the wrong lamp is flashed, and in either case the despatcher is informed that the substation switch is not on the desired set of contacts.

Assuming at any rate that the desired lamp does not start flashing, the despatcher releases the switch E at this stage without operating the device for which it is set. In order to do this, he merely releases the key K which he has been holding operated during this time, thereby opening the circuit of relay I6 and permitting it to deenergize. Upon deenergizing, relay I6 opens the bridge across conductors 41 and 48, whereupon line relay 60 of the switch E deenergizes and sends an impulse of current over the previously traced operating circuit to the relay 63. Relay 63, upon energizing at this time, opens the locking circuit of holding relay I35 in the relay group RG at armature 1 I, whereupon relay I35 deenergizes and opens the bridge across conductors 49 and 50, permitting the switch D to release In qjaanner to be described subsequently. A momentjifter the deenergization of line relay 60, slow-acting release relay 6| deenergizes due to the prolonged opening of its circuit, thereby bringing about the release of the switch E in a manner to be described subsequently.

Returning now to the original assumption that the switch .E operated as the despatcher desired and that the switch D was set on the contacts 8 and 9 with the result that the lamp I. started flashing, the despatcher, upon noting that the desired lamp is flashing, knows that the switch E .is set in the desired position and not in some other position. The despatcher now operates his calling device CD in accordance with any desired digit, the digit -1, for example, thereby producing a momentary interruption in the circuit of line relay 60 of the switch E, whereupon the line relay 60 deenergizes momentarily and sends an impulse of current to slow-acting relay 63, resulting in the energization of said relay 63. Relay 63, being slow-acting, maintains its armature attracted for an interval after the termination of this impulse and at armature H opens the locking circuit of holding relay I35, Fig. 3, whereupon relay I35 deenergizes and opens the bridge across conductors 49 and 50. As a further result of the energiza tion of relay 63 of the switch E, it prepares a circuit for relay 65 at armature I3. When line relay 60 energizes again after its momentary deenergization, it completes a circuit for relay 65 as follows: From ground by way of armature 66 and its working contact, working contact of armature I3 and said armature, working contact of armature I1 and said armature, and relay 65 to battery. Upon energizing, relay 65 places ground on wiper 86 at armature 19 in order to operate the starter-S.

After having manipulated his calling device for the digit 1 to initiate the operation of the starter S as described above, the despatcher releases the key K, thereby opening the circuit of relay It. It may be pointed out that the off normal spring I 5 comes into engagement with its associated contact .as soon as the dial of the calling device is turned ofi normal, thereby closing a circuit tor relay I6 independent of the key K so as to maintain the relay I6 energized a sufllcient length of time in case the despatcher happens to release the key K too quickly while the calling device is returning to normal after having been operated the last time. Upon deenergizing, relay l6 opens the bridge across conductors 41 and 48 at armature l8, whereupon the line and release relays oi the switch E. deenergize one after the other, and release relay 6|, upon deenergizing, opens the operating circuit and closes the release magnet circuit at armature 69, and at armature 68 removes ground irom the locking armature 15 of relay 64 and replaces ground on the chain conductor I24. Relay 65 deenergizes in response to the'falling back of armature 66 of line relay 60 and removes ground from wiper 86 and relay 64 deenergizes in response to the opening of its locking circuit by release relay 6|. Release magnet 8| energizes in response'to the deenergization of release relay 6! and is energized over the following circuit: From ground by way of armature 66 and its resting contact, armature 69 and its resting contact, off normal contacts 83, and release magnet 8| to battery. Upon the energization of release magnet 8|, the shaft and wipers of the switch E are restored to normal position, and the circuit of release magnet 8| is opened at ofi normal contacts 83 by the switch shaft when the latter reaches its normal position.

The line and release relays 29 and 28 of the switch D in the despatchers omce deenergize one after the other in response to the opening of the bridge across conductors 48 and 58 in the substation as pointed out hereinbefore. In response to the deenergization of release relay 28, armature 39' is retracted and the circuit-oi relays 24 and 25 is opened, whereupon these relays deenergize. As a further result of the deenergization of release relay 28, thecircuit of release magnet 44 is closed the same is in engagement with bank contact 88 as explained hereinbefore.

Upon energizing, relay 2 closes a locking circuit for itself at armature 246 in series with the resting contact of armature 232 and said armature; closes a circuit for the solenoid 230 through armature 244 and its, resting contact at armature 245; and at armature 241 'closes a circuit for relay 240 through the resting contact of armature 242 and said armature. Relay 240 does not energize immediately, however, owing to the fact that it is wound so as to be highly inductive and owing also to its stifi adjustment. In response to the closing of the circuit of the solenoid 230, said solenoid 238 energizes and attracts the plunger 228, thereby rotating the operating lever in such a direction as to swing all of the pivoted switches 2|8-223, inclusive, to the left. This results in the three-phase auto-transformer being connected to the three-phase supply leads 2| 5-2", inclusive. The switch levers 221-223, inclusive, connect the three conductors of the three-phase induction motor of the motor generator MG to the reduced potential taps of the auto-transformer. When this occurs, the motor generator MG starts to pick up speed and, as usual, draws a very heavy current for starting. This heavy'current is sufficient to operate the relay'238 which is shunted around resistance 224 connected in one of the auto-transformer leads. Relay 238 energizes before the slow to energize relay 240 has had time to energize and opens the circuit of the latter.

When the motor generator MG has picked up suflicient speed to approach synchronism, the intake of current is no longer sumcient to main- I tain the marginally adjusted relay 238 energized.

Accordingly, relay 238' deenergizes and closes the circuit of relay 240 at armature 242. I Relay 240, upon energizing after the interval for which it is adjusted, attracts armature 244, thereby opening the circuit of solenoid 230 and closing a circuit through solenoid 23L When this occurs, the plunger 229 is attracted and the operating lever 226 swings the switch arms 2|8-223, inclusive, to the right, thereby disconnecting the auto-transformer from the line and connecting the three conductors of the motor direct on to the line instead of to the low potential taps. One of the conductors through which current is now supplied to the motor is cut and the' resistance 228 is inserted therein. The holding magnet 233 is connected in shunt of resistance 228 through armature 243 and its resting contact. Holding magnet 233 accordingly energizes and attracts its armature 232 which engages the end of the lever 226, thereby holding said lever in its operated position independent of the solenoid 23L The attraction of armature 232 results in the locking circuit of relay 24] being broken. Relay 24I, upon deenergizing, opens the circuit of relay 240 at armature 241, whereupon relay 240 deenergizes and opens the circuit of solenoid 23I, leaving the lever 226 under the control of armature 232 which holds said lever 226 in its operated position. The motor generator MG is now up to speed and is ready to carry its portion of the load.

As a further result of the starter S being thrown to running position, ground is removed from conductor I I9 and placed on conductor 8. When this occurs, the cut-off relay which is shown locked up over conductor II9 deenergizes and relay 302 is energized over conductor H8 through armature 305 and its resting contact. Upon energizing, relay 302 opens the chain circuit so as to render the energization of any one of the other similar relays ineifective in case it should occur at this time. Relay 302 also closes a circuit for relay 303 at armature 306 as follows: From ground by way of armature 68 and its resting contact, chain conductor I24, armature I58 and its resting contact, armature 306 and its working contact, and relay 303 to battery. Upon energizing, relay 303 opens at armature 301 the chain circuit extending to the other similar relays so as to unlock any of them that might have just become locked up over this chain circuit. These two chain circuits, it may be pointed out, are used in order to secure the desired effect that only one relay, such as 303, can remain energized while a call is being sent in to the despatchers office. Otherwise, two or more such relays might be energized at the same time and prevent the successful operation of the call sending equipment. As a further result of the energization of relay 303, it closes a locking circuit for itself at armature 301 which includes the locking conductor I25 which is grounded .by way of the normally closed contacts controlled by armature I64 of relay I43; prepares a circuit for relay 30I at armature 308; connects up the first and second digit stop conductors to the first impulse stop conductor I8I at armatures 309 and 3I0; and at armature 3II places ground on conductor I26 with the hereinbefore described results that relays I40 and MI are energized. Relay I40, it may be explained at this time, is highly inductive and stifily adjusted and for these reasons does not energize immediately. Relay I4I, however, energizes right away and opens at armature I58 another point in the chain circuit extending through armature 306 and its resting contact and similar armatures and contacts on the corresponding relays in the other sets. This is done to prevent the operation of any relay set irom being interfered with by a preceding relay set after the operation has progressed thus far. While this operation has no particular utility at this stage of the operation in this particular case, it is a. very necessary operation when the call sending relay set in operation is one of the sets other than the first in the chain. After an interval, the slow to pull up relay I40 energizes and places ground on the common conductor I29, thereby closing a circuit for cut-off relay 30I through the working contact of armature 308 and said armature. Relay 30I, upon energizing, disconnects conductor IIO from relay 303 at armature 304, and at armature 305 opens the circuit of relay 302 and locks itself to grounded conductor I I8 to spring 305 and its make contact. Relay 302, having completed its operation, now deenergizes.

' It can probably now be understood just why the grounding of the common conductor I29 was As a further result of the placing of ground on conductor I26 by relay 303, relay I42 operates to close a bridge across conductors 49 and 50 at armature I62, and the remaining relays I43-I46, inclusive, together with the counting switch CS operate as described hereinbefore to send in the number II to the control switch D in the despatchers oflice. At this time since the switch E is not operated, the conductor I22 is not grounded and holding relay I35 does not energize after the call has been sent in and the switch D is, therefore, rel-eased upon the opening of the bridge across conductors 49 and 50 at armature I62 when relay I42 deenergizes, which it does as described in the preceding example.

It will be remembered that, as explained hereinbefore, the slow-acting relay I43 maintains conductor I26 grounded at armature I63 after the ground has been removed from the said conductor I26 at one of the call sending relays, such as relay 303. This is done so as to prevent another call from being sent in to the despatchers office before the switch D has had time to return to normal. The line circuit of the switch D is opened at armature I62 by relay I42, which relay opens the circuit of slow-acting relay I43 at the same time. Another call cannot be sent in, however, until after the slow-acting relay I4I, which is maintained energized over conductor I26, has deenergized and closed the chain circuit at armature I58. This interval is that required for the two slow-acting relays I43 and MI to'fall back one after the other, and is sufliciently long to permit the switch D to be completely restored to normal position.

In the despatchers office, since the despatcher is not making a call, relay 24 is not energized and,

wipers 22 and 23, a circuit is closed for the pilotrelay I0 as follows: From ground by way of the working contact of armature 3i and said armature, armature 30' and its resting contact, and

pilot relay I0 to battery. Pilot relay I0, upon energizing, closes a locking circuit for itself at armature I3, and at armatures II and I2, closes the circuits for the lamp L and the buzzer B so as to inform the despatcher both visually and audibly that a call is coming in. Also, since-relay 24 is not energized. the wiper 23 instead of the wiper 22 is connected up to the lower winding of relay 25, and as soon as the slow-acting relay 26 deenergizes after the switch wipers have been set on the contacts 8 and 9, relays 25 and 2 energize in series over the following circuit: From ground by way of the resting contact of armature 30 and said armature, armature 39 and its working con tact, armature 31' and its resting contact, lower winding of switchir: relay 25, normally closed contacts controlled by armature 35, armature 32 and its resting contact, wiper 23, bank contact 9, relay 2, and the associated resistance to battery. Due to its lighter adjustment, relay 25 energizes first over this circuit and closes the previously traced locking circuit for itself at armature 34;

contact, and the .lamp L to battery. Accord-.

ingly, the lamp L starts flashing under the control of the flasher F. The lamp is made to flash at this time so as to give the despatcher immediate indication of the particular set of lamps in which the change has occurred. This obviates any necessity for a checking operation by the despatcher.

The despatcher, after having been informed by the buzzer B and the pilot lamp L that a call is coming in, operates the push button P, thereby opening the locking circuit of the pilot relay I0, whereupon said relay I0 deenergizes and extinguishes the lamp L and disconnects the buzzer B.

After having taken sufllcient note of the set of lamps in which the change has occurred, the despatcher operates the locking key K to its alternate position by pushing the locking push button shown, thereby disconnecting the working contact of armature 5 from ground by way of the flasher F and connecting it to ground direct. This causes the lamp L to stop flashing and to light steadily. This operation also serves to prepare a flashing circuit for the lamp L which becomes effective upon the subsequent deenergization of the relay 2.

The switch D is released at this time in the hereinbefore described manner.

In order to put the motor generator MG finally into operation, it is necessary that the circuit breaker CB be thrown in. In order to effect this operation, it is necessary for the despatcher to close the bridge across line conductors 41 and 48 and then dial the number assigned to the throwing in of the circuit breaker CB. This number, it will be assumed, is I9. Accordingly, the despatcher operates the key K with the hereinbefore described results and then operates his calling device CD for the two digits 1 and 9 in the number 19.

In response to the operation of the calling device CD in accordance with the digit 1, the wipers or" the switch E are raised opposite the first level of bank contacts, and in response to the operation of the calling device CD in accordance with the second digit 9 of the number, the wipers and 86 are brought into engagement with the ninth set of bank contacts in the first level, which are the contacts 9| and 92.- When wiper 85 is grounded at the cessation of the.rotary movement, ground is placed on bank contact SI and is extended through conductor II2 to the third set of relays, counting from the left, shown in the upper part of Fig. 3. This results in these relays operating in the same manner as described for relays 30I-303, inclusive, and the number 19 is sent in to the substation by the calling sending equipment, thereby bringing the wipers of the switch D in the substation into engagement with the ninth set of bank contacts in the first level. This results in the associated lamp being flashed in the usual manner, thereby giving the despatcher the indication that the switch E is on the right set of bank contacts. It will be noted I that the number 19 is sent out by the call sending equipment in this case'instead of the number 11 described in the preceding case, owing to the fact that the ninth impulse stop conductor I89 is used to terminate the second digit ratherthan the first impulse stop conductor I8I.

The despatcher now operates the calling device CD again i or der to throw in the circuit breaker CB and, hen this occurs, the wiper 86 is grounded momentarily as hereinbefore described, with the result that the ground potential is extended by way of bank contact 92 and conductor I I6 to the solenoid 25B of the circuit breaker CB. The momentary energization of solenoid 256 results in the plunger 255 being attracted, whereupon the lever 254 is rotated, thereby connecting the switch arm 253 with the lead extending to the bus-bar 260-. The armature 2 51 of trip magnet 258 is provided with the notch in the upper end in which the end of the lever 254 catches,

thereby holding the circuit breaker in its operated position. The lever 254 also ungrounds conductor I2I, thereby causing the associated locked up relay to deenergize, and places ground on conductor I20 with the result that the call sending equipment is again operated to send in the number I9 to theswitch D in the despatchers office, which has been released in the hereinbefore described manner in the meantime owing to the deenergizatlon of holding relay I35 which occurred in response to the last mentioned operation of the calling device CD.

The switch E is released in the usual manner when the despatcher releases the key K afterhaving brought about the operation of the circuit breaker CB.

It will be noted that in case the alternating current supply to the motor of the motor generator MG is interrupted, the holding magnet 233 is deenergized, whereupon the armature 232 is retracted and the starter returns to its normal position. When this occurs, the ground potential is removed from conductor II8, allowing the locked up relay 30I to deenergize and a ground potential is placed on conductor HQ with the result that the number I2 is sent in by the call sending equipment, which results in the wipers 22 and 23 of the switch D being brought into engagement with the bank contacts 6 and 'I which are the second set of bank contacts in the first level. When this occurs, the wiper 23 places ground on bank contact I, thereby short circuiting the relay 2 and causing the said relay 2 to deenergize. The switch D is then released automatically in the usual manner. The deenergization of relay 2 results in the lamp L becoming extinguished and. the lamp L being connected up to the flasher F through the working contact of the lower spring of the associated key K and said spring, resting contact of armature 5 and said armature, and armature 4 and its resting contact. The despatcher, upon noting the flashing condition of the lamp L knows that the starter S has returned to normal. The despatcher causes the lamp L to light steadily by retracting the plunger of the key K and allowing the springs thereof to assume their normal position. 1

The despatcher may in this case take such steps as he may deem necessary, either reoperating the starter S immediately or waiting a sufficient length of time to permit the supply of current to the leads 2I5-2II, inclusive, in. the substation to be replaced.

Although it is not shown as such, the circuit breaker CB is preferably of the typehaving a suitable circuit arrangement for tripping the circuit breaker in case the current is reversed. Assuming the circuit breaker CB to be a reverse current circuit breaker, it is tripped immediately after the starter S is returned to normal, owing to the-fact that the motor generator MG slows down and the generator there- 01 starts to run as a motor, taking current from the bus-bar 260. The circuit breaker CB has the resistance 259 energizes and trips the circuit breaker. This results in ground being removed from-conductor I20 and placed on conductor Ill. The result of ground being placed on conductor I2I is that the associated relay group is operated and the call sending equipment sends in the number I due to the fact that the first and tenth impulse stop conductors I8I and I90, respectively, are associated with this relay group. This causes the switch D in the despatcher's office to operate in the usual manner to give the despatcher the necessary signal.

It has been shown above how either the starter S or the circuit breaker CB can be returned to normal owing to an abnormal condition in the substation. It will now be explained how. the despatcher himself can initiate either of these operations. In order to restore the circuit breaker CB, the despatcher dials the number 10, causing the wipers 85 and 86 ofthe switch E to be brought into engagement with the tenth set of bank contacts in the first level. Then, when the despatcher gives the calling device CD the extra operation after receiving the usual indication that the switch E is on the right contacts, the bank contact 94 is grounded by the wiper 86 and trip magnet 256 of the circuit breaker CB is operated over conductor III.

Similarly, the starter S can be restored by the despatcher who for this purpose closes the line circuit of the switch E by means of the key K and then dials the number I2, thereby causing the wipers 85 and 86 of the switch E to be set upon the bank contacts 89 and 90. The despatcher then gives the calling device CD a further turn, after having received the usual indication that the switch E is on the desired set of contacts, thereby causing a ground potential to be supplied to bank contact 90 by way of the wiper 86. This ground potential extends by way of conductor II to relay 239 in the starter S which thereupon energizes and opens the circuit of holding magnet 233, whereupon the starter S is returned to its normal position, with the result that the corresponding number I2 is sent in to the despatchersoflice by the call sending equipment in the manner described above.

In case the despatcher has any reason to believe that the lamp indication of the position of any particular substation switching devices is incorrect, he may verify his opinion or, at any rate, ascertain the true position of any particular switching device such as the starter S, for example, by' closing the line circuit of the switch E and dialling either one of the two numbers assigned to that device. In case the lamp L,

Fig. 1-, is lighted, indicating that the starter 8 is at normal, the despatcher may verify this by dialling the number II, with theresult that the lamp'll starts flashing as hereinbeiore described in case the starter is actually at normal, while '6 ii the lamp L indicates that the starter is at normal at a time when the starter is actually in I its operated position, the despatcher'will not be able to receive any response when he dials the number 11 for thereason that cut-oil! relay IIII will be operated at that time and the lead III! will be disconnected from relay 803 at armature 304.

In this case the despatcher will probably want still further verification in order that he may 15 be absolutely sure of the position of the starter S and he will, therefore, dial the number 12,

whereupon the switch E through its wiper 86 places ground on conductor III which is not at this time disconnected from the associated relay in Fig. 3, and, as a result, the call sending equipment sends in the number 12 resulting in the flashing of the lamp L.

It will be seen from the foregoing that the present system is a considerable improvement over prior systems of the same nature in that the despatcher is enabled to ascertain the position of the substation switch before he operates the device associated with that position of the switch. It will be seen further that the des- 80 patcher is enabled to check the indicated position of any piece of switching apparatus against the actual position.

What we claim is:

1. In a remote control system, a calling device, 85 a control switch, a control circuit extending between said device and switch, a key associated with said calling device, two relays operated in response to the operation of said key, said relays jointly, completing said control circuit, means for operating said control switch over saidcontrol circuit in response to a manipulation of said calling device, and contacts operated by said calling device for maintaining said control circuit completed independent of said key, while said calling device is being operated and for a definite interval thereafter.

2. In a remote control system, a switching device having a plurality of positions, a visual signal for each position of said device, means whereby one of said signals is operated to indi-- cate the position of the switching device, a circuit between said device and signal, means for moving said switching device to a new position, means responsive thereto and controlled over said circuit for restoring said operated signal to its normal condition and for intermittently operating the signal associated with the new position of the switching device, and manually controlled means for causing the last named signal to be operated steadily.

3. In a remote control system, a plurality of switching devices each having a plurality of positions, a set of signals for each device, one signal of the set corresponding to each position of the associated device, automatic means for maintaining the proper signal operated to indicate the position of the device, means responsive to a change in position of the device for intermittently operating the signal indicating the new position and retiring the signal indicating the old position of the device.

4. In a remote control system, a plurality oi. switching devices each having a plurality of positions, a set of signals for each device, one

for extending a circuit to a. device to change its position, and automatic means responsive to the extension of saidcircuit for intermittently operating the signal which indicates the position into which the device is to be moved.

5. In aremote control system, a plurality oi. switching devices each having a plurality of positions, a set of signals for each device consisting of a signal for each position of the device, automatic means for maintaining the proper signal operated to indicate the position of the device means responsive to a change in position of a device for intermittently operating the signal indicating the new position and retiring the signal indicating the old position, means for selecting a device and moving it from one position to another, means operating in response to said selection to control said automatic means to intermittently operate the signal indicating the new position and to maintain the signal indicating the old position.

6. In a remote control system, a plurality of devices each having a plurality of positions, a set of signals for each device comprising a signal for each position of the device, means for selecting a device to change its position, an automatic switch operated in response to said selection to intermittently operate the signal indicating the position into which the device is to be moved without affecting the operation of the signal which indicates the position in which the device stands, means for then changing the position of the device, means responsive to said change in position to control said automatic switch to intermittently operate the signal indicating the position into which the device moves and to retire the signal indicating its old position.

'7. In a remote control system, a plurality of switching devices, signalling devices, means for.

selecting a device at the substation to change its position, switching mechanism automatically respons'ive to a change in position'oi one of the devices to control the signalling means to indicate that change in position, automatic means controlled by the initiation of the operation of said first means to change the function of said switching mechanism to prevent its indication of further changes of the devices on said signalling means and to prepare it to indicate the position of said selecting means, and means for delaying the change in function of said switching mechanism for a certain time after the initiation or the operation of said first means to permit indications of changes already in progress to be completed.

8. In a remote control system, a control circuit and a checking circuit, a step by step control switch, a calling device, a key associated with said calling device, means responsive to the operation of said key for completing said control circuit, means for operating said control switch 9. In a control system, a control circuit terminating in a selective control switch, a checking circuit terminating in a selective checking switch, a plurality of switching devices, each having a plurality of positions, an indicating device for each or said switching devices, each indicating device having a plurality of positions correspending to the positions of the corresponding switching device, means for moving each 01' said switching devices from one position to another, means including checking means controlled by the change of position of a device over said checking circuit and through the medium of said checking switch for causing the associated indi- 10. In a remote control system, a plurality of switching devices, a set of signals for each device, a selective switch, means operating automatically inv response to a change of condition of any device to operate said switch to select the associated set of signals, means in said switch for operating said signals to indicate the change in the condition of the device, another automatic switch, means for operating said second switch to select one of said devices, means operated by said second switch to render said first means unresponsive to changes in therconditions 01' said devices, and means controlled by the operation of 'said second switch for operating said first means to operate said first switch in a distinctive manner to indicate the position 01' said second switch.

11. In a remote control system, a plurality of switching devices each operable from one position to another, signalling means individual to each of said devices, common selecting means for selecting any one of said devices for operation, means for operating said device, means responsive to the selection of said last device for operating said signalling means in one manner to indicate such seizure, said means also responsive to the operation of said device for operating said signalling means in a diiIerent manner to indicate the actual operation of said device.

12. In a remote control system, a plurality of switching devices, an operating circuit individual to each-oi said devices, signalling means individual to each of said devices, means for preparing the operating circuit of one of said devices, means responsive to the preparation 01' said circuit for operating the signalling means individual to said device in one manner to indicate the said prepared operating circuit, means for completing said operating circuit to operate said device, and said second means reoperated responsive to the actual operation of said device over said circuit for reoperating said signalling means in a diflerent manner to indicate the actual operation of said device.

RODNEY G. RICHARDSON. JOHN I. BELLAMY.

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