US1680971A - Indication for color light signals - Google Patents

Description

Aug.14,1928. 1,680,971

S. M. DAY I INDICATION FOR COLOR LIGHT SIGNALS Original Filed April 5, 1923 Patented Aug. 14, 1928.

UNITED STATES PATENT OFFICE.

sALis URY M. DAY, OF ROCHESTER, NEW YORK, Assrenonro GENERAL RAILWAY SIGNAL COMPAYLTYLOF GATES, vEw YORK, A CORPORATION OF NEW YORK.

INDICATION FOR COLOR LIGHT SIGNALS.

Application filed April 3, 1923, Serial No. 629,627. Renewed April 5, 1927.

This invention relates-to interlocking systems employing color light signals, and more particularly to indicating means governed by such signals for unlocking the signal le- 1 vers and giving a visual indication in the signal tower. i

In alternating current interlocking plants where a reliable source of alternating current is available, it is found enonoinical and tion given by the respective signals.

desirable to use distinctive aspect color light signals energized by alternating current instead of the usual semaphore signals. In

systems of this kind, it is highly important that the control levers iii the tower should have a position corresponding to the indica That is, if the lever of a particular signal is moved from the reverse or clear position toward the normal or danger position, the completion of the stroke of this lever to the full normal position should not be possible unless the signal controlled thereby actually indicates danger. This is important because the move ment of a signal .lQVElflH an interlocking plant of the usual construction, when moved to the full normal position, will unlock other and conflicting levers operating signals of conflicting routes, 'derails, switches, and the like. l a

W'ith the above and other considerations in mind,it is proposed in accordance withthe present invention toprovide the usual signal lever having an indicationmagnet with means for energizing this magnet only it the light signal associated therewith is indicating danger, this means to be of a construction to facilitate adjustment of the various constants, especially the voltage applied to the respective lamps of the light signals; and also of a construction in which many of the electrical circuits are entirely insulated from the rest, which to a large extent assurcs against detrimental and dangerous crosses and grounds.

Other objects, purposes and characteristic features of the invention will appear as the description thereof progresses.

In describingthe invention in detail, ref- -crence will be made to the accompanying drawings, in which Figure 1 showsrthe invention applied to one form of semi-automatic block signal system, in which thevarious devices are shown in a diagrammatic and simplified manner so as to avoid complicating the description of the novel combination shown; and

Fig. 2 shows in a schematic manner an ap- .plication of the principles of the invention tomatically and assume a condition corresponding to the most unfavorable condition of the two controls effected at any time. Ohviously, the invention may be applied in other types of systems, but for convenience only one particular type has been illustrated. Since the several blocks in the particular system illustrated are thesame, like parts and circuits of the various blocks have been given the same reference characters with distincti-ve exponents.

track transformer 3 and. a track relay T,

which in combination with the track rails form the usual closed track circuit. At the entrance to each block there is provided a distinctive aspect light signal Z, which in the particular arrangement shown is provided with three independent lamps designated G,

vY and R and provided with color screens colored green, yellow and red, respectively, each of the lamps being energized by separate transformers 12, 13 and 14 respectively, as shown. Adjacent to each of the signals Z is provided a home relay HR and a distant relay D. These relays, in conjunction with the track relay T and a signal lever L, are adapt ed to control the indication of the lamps G, Y and R of the signal Z. c In the interlocking tower 'is provided manually operable lever L, which with its associated parts comprises a portion of a well-known dynamic indication interlocking system, and therefore will not be described in detail. It may, however, be stated that the coils 4 and armature 5 are parts ot' an indication magnet 1M, which in connection with the detent 6 is adapted to release the lock dog 7 from the locking shoulder 8 o l the lever L when this lever is being operated from the reverse toward the normal position. The lever is locked in the halt normal position by the engagement of this locking shoulder S with the lock dog 7 during this direct-ion of movement. This locking of the lever L in the half normal position persists until an indication current is received by the coils l ol the indication magnet IM. A inomcntary flow of currentthrough these coils l, with the lever in the hall' normal position, causes the armature to be attracted to move the detent (3 Trent under the lock dog 7, whereby the spring 9 moves the lock dog 7 to its ineffective position, thus enabling the tower attendant to move the lever L to the normal position and in turn unlock certain other conflicting levers.

It should be. noted that movement of the lever L toward the left. that is. toward the reverse position, will not cause it to be eli'ectively locked when reacl'iing the half reverse position. Although the righthand end of the lock dog 7 would be moved upward and retained there temporarily by the deteut t, as the lever is moved toward the left the projection l0 rocks the unlocking cam 11 which in turn strikes the tail piece of the detent (5. thereby unlocking this lever. That is. the lever L is locked in both the half normal and the half reverse positions, but upon movement of the lever to the reverse position mechanical unlocking takes place regardless of the condition of the distant signal; whereas movement of the lever toward the right, that is, toward the normal position does not cause such unlocking and the unlocking in this instance must be accomplished by the energizalion ol the indication magnet IM.

In the interlocking tower are also provided relays for controlling the flow of current to the indication magnet IM and to suitable pilot signals. In the particular arrangement shown, a clear and caution relay (lYR. and a danger relay RR, have been shown. These relays also control the pilot lamps GY and Re.

The individual transformers 1Q, 13 and 14, having their secondaries separately connected to the lamps G, Y and R respectively, are of a special construction. These transformers are designed and constructed to have characteristics similar to both a potential transtorn'icr and a current transformer oi the type well-known and used in commercial alternating current lighting and power systems. That is, each of these transformers is constructed to give a substantially constant voltage at its secondary terminals when the primary winding is connected in series with one of the relays GYR or RR and a source of energy, and will in turn energize such relay to move it to the energized position when the secondary winding of such transformer is closed through a signal lamp having its filament or filaments intact; but on the other hand requires a very small exciting current, insutlicient to move the relay to the energized position, if its secondary winding is open [or any reason.

The lamps (,i, Y and R are preferably of the multiple filament type, that is, are prel'erably constructed with two filaments connected in multiple, so that, it one ol the filaments burns out, an effective but weakened signal will still be given whereby information will be conveyed to the train crew and yard workmen that the signal lamp is partially burned out. Also, the relays GYR and RR in the tower may be so adjusted that they will not be moved to the energized position by the current flowing in the primary winding of the particular transformer 152, 13- or ll, to which they are connected when the lamp connected to the secondary winding of such transformer has one of its filaments burned out. lhus, by this construction, not only will it be possible to tell when a signal lamp is partially burned out by looking at such signal lamp from a distance but this will be indicated in the tower also, so that such lamp may be in'm'iediiately replaced.

Operation.

The signal lever L and the signal Z controlled thcreby have been shown in their normal danger condition, with the block to the entrance of which this signal is placed and the next block in advance thereof unoccupied and in their clear traliic condition. Under this condition, the track relay '1 at the entrance of the block I is energized by track circuit current from the track transvtormcr 3. Since the lever is in its normal danger position, the home relay HR and the distant relay D are decnergized. With these latter relays deenergized, the transformer l-i associated with the red lamp R is encrgized through the following circuit:lieginning at the secondary winding of the transforn'icr 20, wires 21 and 22, primary winding of the transformer 14, wire 23. back contact Ql of the distant relay D. wire 25, back contact 26 of the home relay HR wire 27, relay RR, wires and 2!) back to the secondary winding of the trmist'ormcr it). there by illuminating the red lamp R by energy derived from the secondary of this transformer.

lVith this red lamp R taking current from the secondary winding of the tl'ans'lbrmcr 1 1. a proportional current will flow in the primary winding which is sutlicient to maintain the relay RR in the tower in its energized position. This red lamp 11 is connected to the proper tap of the secondary winding of thedanger relay RR, wire 38, back contact 39 of the clear and caution relay GYR, wire 40 back to the secondary Winding of the transformer 33.

Danger to 0Zear-ma0maZZy.-If the lever L is moved to the reverse or extreme left position, a circuit will be completed which may be traced as follows :Beginning at the secondary winding of the transformer 33, Wire 43, spring contact 44, contact block of the lever L, spring contact l6, wire W, front contact 47 of the track relay T, wire 48,- winding of the home relay I-IR, wires 49, 50 and 51 back to the secondary of the transformer 33. The completion of this circuit energizes the home rela HR'which interrupts the circuit for the anger relay RR in the tower by the lifting of back contact 26, and also completes a circuit for the distant relay'D which may be traced as follows Beginning at the secondary winding of the transformer 53 wire 54, front contact 55 of the track relay T, wire 56, front contact 57 of the track relay T, wire 58, front contact 59 of the homerelay HR, wire 60,

winding of the distant relay D, wires 61,

50 and 62 back to the secondary Winding of the transformer 53. I i

This energization of the relays HR and D completes an energizing circuit for the primary winding of the clear transformer 12 as follows z- Beginning at the secondary winding of. the transformer 20, wires 21, 63 and 64, primary winding of the transformer 12, wire 65., front contact 66 of the distant relay D, wire 67 front contact '68 of the home relay HR, wire 69, front contact 70 of the track relay T, wire 71, winding of the clear and caution relay GYR, wires 72 and 29 back to the secondary winding of the transformer 20. This flow of current through the primary winding of the clear transformer 12 and the relay GYR causes this relay to liftits back contact 39, the red pilot lamp Re' alreadyhaving beenextingnished by de-energization of relay RR and illuminating the clear and caution pilot lamp GY. This lamp GY is energized through a circuit including the secondary winding of the transformer 33, wire 40, contact'39 of the relay GYR, wire 74, lamp GY, wires 7 5 and 34.

Clear to dangewwutomatically.1f a train now passes through the block H in the a train.

normal direction of trafiic, as indicated by the arrow, and passes into the block I, the track relay T is deenergized because it is being shunted by the wheels and axles of the vehicle. This causes the home relayIIR and the distant relay D both to become deenergized, as is readily apparent by look ing at the drawing. The deenergization of the relays HR and D interrupts the circuit.

for the clear and caution relay GYR in the tower, and again energizes the danger relay RR, which causes the lamp GY to be extinguished and the lamp Re to be energized, thereby informing the tower attendant that the block I is occupied by another Since the danger lamp transformer 14 has its primary winding connected in series with the danger relay RR in the tower, the red lamp R of the signal'Z is also illuminated, thereby giving the proper indication to a following train attempting to enter the block I. a

Danger 20 0cmHow-ammonmticallyrads the train, assumed to be occupying the block I,

passes out of this block into the next block J, the track rclayIT at the entrance of the block J will'be deenergized, thereby preventing the distant relay D from picking up even if the track relay T and the home relay HR were energized, the energizing cir cuit for the distant relay D being broken at the front contact 55 of the track relay T As the train leaves the block I, the track relay T is again energized. This causes the home relay HR to pick up for obvious reasons, but does not cause the distant relay D to pick up for-reasons just explained.

With the track relay T and the home relay HR'in their energized position, and the distant relay D in its deenergized position, a

circuit for the caution transformer 13 may be traced as follows :-Beginning at the secondary winding of the transformer 20, wires 21, 63 and 78, primary winding of the transformer 13, wire 79, back contact 66 of the distant relay D, wire 67, front contact 68 of the home relay HR, wire 69, front contact 70 of the track relay T, wire 71, winding of the clear and caution relay GYR, wires 72 i and 29 back to the secondary winding of the transformer 20. The completion of this.

circuit causes the lamp Y of the signal Z to be energized by'current derived from the secondary winding of the transformer 13, consequently a proportional current will fiow in the primary winding of this transformer and through the circuit just traced, thereby energizing the clear and caution relay GYR in the signal tower which in turn completes a circuit heretofore traced for energizing the clear and caution lamp GY.

Caution to 0Zea-rautoma tically.-As the train now considered to be moving inthe block J passes out of this block in the direction of traffic, the track relay T again becomes energized. This muses the energizing circuit for the distant relay D to again become completed as heretofore traced, thereby again energizing this relay and completing a circuit through the primary winding of the clear trmis'tormer 12 heretofore traced. thus causing the illumination of the green lamp (l and causing a current proportional to the current conamned by this lamp to flow through the clear and caution relay in the tower. thus maintaining it in its energized condition as it, was prior to the clearing of this block I.

Ulcer f0 (l .1 21f/( 7-lll(l7lZ[/ H /.-L(l us assume now that the tower attendant wishes to allow a train to more over an interfering track (not; shown). such as a crossover. Before the attendant can allow such movement of a t'ain over a contlicting route, he must lirst remove certain dcrails. open certain switches or clear certain signals, which cannot be done until the lever ll governing the signal Z of the block l shown has first been moved back to the normal position.

It now the lever L moved toward the right. that is. toward the normal position, it can only be moved in this direction until the contact block 4:) assumes the dotted position shown in the drawing. ".Vhen the lever L reaches this position. the right-hand end of the lock dog T will be engaged by the locking shoulder S of the lever ll. this lock dog being held in the locking position by the detent ti. Since the contact block to does no longer bridge the spring contacts ll and it, the circuit for the home relay llll will be broken. thereby deenergizing the distant relay .D for reasons heretofore described. Since the relays Hit and D are now in their deenergixed position, the clear and caution relay (ii it will be dccnergized and the circuit including the danger relay RR in the tower and the priu'iary winding of the danger transformer 1-.l at the signal Z will be completed. thereby illuminating the red lamp it and causing a prrntortional current to tlow through the winding of the danger relay llll. thereby moving it to its energized position.

With the relay (lYl'l decncrgized and the relay ltlt energizwl. a circuit may be traced through the indication nuignet 1M as followsZ-licglnning at the secondary winding of the translormer I'lll. vire 8'2, hack contact 83 ot the relay (lfll. wire 84, front contact 85 ot' the relay RR. wire 86, coils -t of the indication magnet IM. wire 8?, spring contact 58, contact block 4-5. spring contact 89 ot the lever L, wire 90 ba k to the secondary winding of the t 'anstorn'ier 33. The completion of this circuit causes the, armature 5 of the indication magnet IM to be attracted. thereby delivering a. blow under the extending arm of the detent 6 whereby the detent is disengaged, thus causing the lock dog 7 to assume the unlatched position. This unlocking ot' the signal lever L allows the tower attendant to complete the move ment of the stroke 01 the lever l, to its [all normal position, which in turn through the usnil ha 'and tappct interlocking mechanism unlocks other conflicting levers.

It should be noted that when the lever L is moved to the halt normal position, as just. described. it one or both filaments of the lamp it is burned out at this time. it will be impossible for the lever to be unlocked to permit its movement to the full normal position. This due to the particular construction of the tmnslormers l2, l3 and H and the adjustment of the relays (:YR and I'll-l. It the red lamp is partially or wholly burned out. there is not enough currentv llowing through the primary winding ot this transformer H to energize the danger relay ltlt in the tower sutiieicntly to cause it to close its front contacts and complete a cir cuit, either tor the pilot lamp He or for the indication magnet l.\l. This cha 'acteristie ot the transformer 1- is due to the fact that the nun ot the ex iting current and one halt ot the current [lowing in the red lamp is smaller than the pick-up current for this rela v. l l' it is desired to use single filament. lamps instead ol'" multiple tilament lamps, the relays (till and Hit should b: adjusted so that they will drop it only the exciting current of one of the transformers 12. ill or ll flows through its winding.

The -onstruction ol' the transformers 12. ill and It also permits various voltages to he applied to a particular type of lamp, or permits lamps of dill'erent voltages to be used. by connecting the lamps to the particular tap thought out: of the secondary winding of these transformers. lo the. particular constrmrtiou shown. only three taps, namely. 30, 3t and 31% have been illustrated. but any number of such taps may be employed it desired.

One clun'acteristic of this invention. which will be readily appreciated from the loregoing explanation. is that the indiratiou mechanism for a lever is controlled dependent upon the actual flow of current through the filament or filaments ot the lamp tor the red signal. In other words. the indication for the lever is dependent upon the actual aspect of the signal itself. so that. unless the signal is actually giving a red or stop indication. no iudicat'ion is received. it should be noted that this result is obtained without nmdil'ying the voltage or current require ments of the incandescent lamps themselves. as is the case whenever it: is attempted to connect a means in circuit directly in series with the lilamcnt. Also. the operating characteristics of the relays RR and (lYll. together with the charactcristics of the transformers 12, 1.3 and ll may be selected, as

. above explained, so that the burning out of one filament of a double or duplex filament lamp will be manifested, thereby indicating to the attendant that alamphas to be replaced. a V,

' Heretofore little attention has been given to determining automatically whether or not the lamp or lamps of a light signal are lighted. Ordinarilyit is assumed that burn ing out of the lamps ofa colorlight signal,

or interruption of their energizing circuits, results in a so-called dark signal WhlCh 1f the engineer, by rule, will interpret as givthe signal casing and observe that there is may be employed to keep the tower man ad GYand Re enable the tower man to disno lamp lighted." It is highly desirable, therefore, as far as consistent, with practical limitations, to provide a means of automati cally detecting the burning out of the lamp of a light signal. Such automatic means has been provided by this invention.

This invention, in its broadest aspects, is applicable to various conditions found n practical railway signaling. The particular arrangement shown in Fi 1 is merely typ1- cal. This arrangement i lustrates how the indication mechanism of a lever may have its cation of the light signal, and also how suitable lamps or other indicators in the tower vised regarding the actual indicating conditions of the several signals. Inthis connection it should be understood that the lamps.

GY and Re are preferably mounted in suitable casings directly above or below the corresponding lever L, or in a well defined relation thereto, so that the tower man can easily associate each lamp with its particular lever. Among other things, the indicator lamps cover at the earliest possible moment whenever the signal lamp of. any one of'the signalsburns out-or has its control circuit open,

thereby permitting the defective lamp to be immediately replacedbr the circuit failure repaired so as not to-1innecessarily delay trafiic movement or introduce a hazardous condition occasioned by a dark signal.

7 It will be observed thatv the relay RR ac curately repeats thelighted condition of the redor danger lamp R, this relay when delamp Rfto ive the desired stop indication may be utilized in ways other than control of the indication mechanism and the indicator lamps GY and Re. An extra contact or contacts X, or a repeater relay controlled thereby," may be added to the re'layRR and these additional contacts. are employed to govern any circuit or circuits which it is de sired in the interestsof safety to break in the event that the red lamp R is out. Various arrangements employing such additional contacts to advantage will be readily appre ciated by those skilled inthe art. For example, the relay RR maybe used to perform a'functionanalogous to thatof the so-called SS relay sometimes used in modern interlocking practice. or, the contact X of the relay RR maybe used to interrupt the con trol circuit of another signal or signalsof conflicting routes. I a V As a typical specific example of the adaptability of the present invention to practical operating conditions, there is shown in Fig. 2 in a diagrammatic fashion the way in which the invention may be employedto electrically interlock or cross-check the indications of the two-arm interlocked sig nal, commonly used to signal traffic over a main or high speed route or over a diverging or low speed route. While the signaling practice for such conditions varies somewhat,

ordinarily there is used what istermed a two-arm signal, this signal consisting of two separate signals one above theother. In Fig. 2 are shown two three-aspect light signals U and B mounted on the same pole. Call-on signals or other signals for giving operation dependent upon the actual 1nd1-- additional aspects, sometimes used, have been omitted to avoid complication. Ord1- narily, the uppermost signal U is used to govvern traiiicon the straight or high speed plified and schematic manner in Fig. 2 of the drawings. Two levers 1L and L have bieen shown, which are] adapted for controlling the signals U and B respectively, subject to automatic control in the same manner as shown in Fig. 1, only that the lever IP'is still "further subjected or restricted, in that, itis at times locked in the normal position.

The dotted rectangles R and R designate the relays T, HR and Dgoverning the signals U and B respectively. The dot and dash line shown indicates the dividing line of the apparatus belonging to these two levers and signals. I

In the particular arrangement shown, the danger relay RR of the lever. L is provided with contacts'X and X similar to thecontacts X heretofore mentioned. The contact 1X is connected in the wire W of the diverging route signal substantially. as hereto the lever L is deenergized.

fore described, and the contact X governs the control circuit for a lock magnet for locking the lever L in its normal position when the danger relay RR associated with Similarly, the relay GYR of the lever L is shown in Fig. 2 with two back contacts Y and Y, which are also included in said circuits.

In order to bring out the advantages and the safety afforded by the application of the invention to the arrangement illustrated in Fig. 2. let us assume that a train is approaching from the left and that the tower attendant has set up the diverging route for the train. \Vith the diverging route set up, the upper signal U will normally indicate red (danger) as before, and the lower si g-.

nal B will indicate green (clear) onthe assumption that two blocks at least in advance on the diverging route are clear. In other words, the whole signal will indicate red over green which means to the engineer that he may proceed but must reduce his speed to take a diverging medium or low speed route.

If now the red lamp of the upper or main track signal U should burn out, a green light standing alone would remain. which n'light be mistaken by the engineer as a signal to proceed at high speed, with the result that the train would probably be derailed when taking the curve of the diverging route. This hazardous condition is avoided in the system shown in Fig. 9 in two different ways.

In the first instance. it the redlamp R of the main line signal U is not ilhnninated at the time the diverging route is being set up. the tower attendant would not be able to move the lever L to set up this route because the lock magnet 100 is not energized at this time, its energizing circuit being broken at the contact X of the relay RR, this relay only being energized when the'lamp R of the signal U is energized. That is, the tower attendant could not clear the lower signal B and would be forcibly and unmistakably in formed that something was wrong, so that it could be immediately looked after and corrected. The whole signal then would have the appearance of: one red light, which would signify stop.

In the second instance, if the red lamp of the main line signal U is intact, the tower man may set up the diverging route. Assuming. however. that the red lamp of the upper signal U fails sometime after the diverging route has been set up, the electric lock 100 on the lever L at this time is useless because the lever L had already been moved to its reverse position. This deencrgization of the red lamp of the main route signal U will, however. deenergize the relay RR of the lever L, thereby deenergizing the relays HR and D included in the dotted rectangle R by interruption of the circuit through wire W, thus changing the indicathe tion of the lower diverging route signal B from clear or caution, as the case may be, lo red (danger). which informs the engineer of; danger ahead and causes him to take the proper precaution in moving up to this interlocking point.

In practice, a distant signal will be located some distance in the rear of the interlocking signals I and l, which might in Hrllltb instances give the engineer additional information in case the red lamp of the signal li should burn out. Since. however, such failure of the lamp It ought easily occur while the train is moving between the distant and the home or interlocking signal. this distant signal has not been shown in the application of the invention to a system such as shown in Fig. 2.

As an additional precaution the contatds Y and Y of the relay GYR are included in the circuit for the lock magnet 0 and the control circuit for signal ll, so that the green and yellow lamps of signal U must be out. before the signal l3 can be changed to give a favorable indication.

IVl do only certain specific aIJpliCaLions o l' invention have been shown and described. particularly with reference to interlocked signals. it will be evident to those skilled in the art that the invention is susccp tihle of other applications in practice; and it is desired to have it understood that various additions, substitutions. changes and modifications may be made in the particular arrangements shown and described so as to adapt theinvention to other practical uses or amilications, all without departing from the spirit. and scope of the invention. or the broad idea of means constituting the invention.

\Vhat is claimed, ist

1. In an interlocking system for railways, the comljiination with a multiple a pect color light signal including a danger lamp. and a transformer for energizing said danger lamp under predetermined conditions, of indicating means located at a distant point and in a circuit. including the primary winding of said transformer for indicating whether or not said danger lamp is energized.

Q. Ina signal system for railroads, the combination with a light signal having an in candesccnt lamp, a transformer having its secondary connected in circuit with said lamp, and an energizing circuit; for the primary of said transformer including a source of current and a relay, said rcla having its energizing current reduced sullicientlv to open its contacts when the impedance of the primary of said transformer is increased upon burning out oil the lamp and cessation of flow of current in the secondary of said transformer.

3. A railway signal system comprising. a color light signal including an incandescent lamp, a transformer having a secondary ill) windingprovided with a plurality of taps for energizing said lamp by any one of a large number of voltages, and means associated with the primary winding of said transformer for indicating whether or not said lamp energized to consume a predetermined amount of energy.

4. A railway signal system according to claim 3. wherein the lamp is provided with two filaments in multiple, and in which the indicating means indicates whether or not bothof said filaments are energized.

5. A railway signal system comprising, a color light signal including an incandescent lamp, automatic trafiic controlled means for illuminating said lamp ii. the block at the entrance to which the signal is placed or the next block in advance thereof are occupied, manually operable means for deenergizing said lamp regardless of trafiic conditions ahead, and. indicating means responsive to the energization of said lamp.

6. In an interlocking system for railways, the combination with a multiple aspect color light signal including a plurality of multiple filament lamps, each of said lamps being connected to the secondary winding of its individual transformer, and means associated with the primary windings of said transformers for indicating the indicating condition of said signal and whether one filament of said multiple filament lamps is burned out.

7. A multiple aspect color light signal comprising, a plurality of color light signals each having a signal lamp having two filaments, means for energizing any one of said lamps, and means for indicating if the particular lamp-energized at the time has both of its filaments intact.

8. In an interlocking system having two levers, a lock on one of said levers, a magnet associated with said lock, said lock locking said one lever when said magnet is de-energized, a multiple aspect light signal associated with and controlled by said one lever, another multiple aspect light signal associated with and controlled by the other lever, and means for deenergizing said magnet when one of the lights insaid another multiple aspect light signal burns out.

9. In an interlocking system for railroads, the combination of a "plurality of multiple aspect color light signals mounted one above the other to indicate traflic conditions on two.

10. An lnterlocking systemfor railroads comprising, two multiple aspect color light signals one located above the other to give a compound indication, and means governed by the current for energizing a lamp of one of the signals for locking a lever governing the other signal or for effecting a danger indication by said other signal.

11. In a signal system for railroads, two light signals each constituting a separate light projecting device, said signals when lighted giving indications corresponding to different trailic conditions, an incandescent lamp for each signal, and means for automatically lighting the lamp of one signal if the lamp of the other signal burns out when it should be lighted.

12. In a signalling system for railroads, the combination with two railway tracks, oi two multiple aspect light signals associated with said tracks each governing traffic over only one of said tracks, manually operable levers for controlling the indicating conditions ofsaid light signals, and means for locking the lever for controlling one of said light signals when a lamp in the other light signal is burned out. 1

13. In a railway signal system, a light signal having a clear lamp and a danger lamp, a manually operable lever, having clear and danger positions, for controlling the signal, an electrically operated detent for the lever preventing movement of the lever from its clear to its danger position when its control circuit is tie-energized, a relay having a front contact in the detent control circuit, and a transformer having its secondary in series with the danger lamp, and its primary in series with the said relay.

14. A light signal for railways comprising, two light projecting units, an incandescent lamp for each unit, control means for each unit and automatic means associated with the lighting circuit of one lamp for lighting the other lamp independently of its control means, said automatic means being eilective whenever the lighting circuit of the first mentioned lamp is established and current fails to flow therein.

15. A light signal for railways comprising, two light. projecting units, an incantdescent lamp for each unit, control means for each unit and a relay controlled bythe 7 lighting circuit of one lamp, and having a contact controlling the lighting circuit of the other lamp independently of its control means, said relay being effective whenever the lighting circuit of the first mentioned lamp is established and current fails to flow therein.

In testimony whereof I hereby aflix my signature. 1

SALISBURY M. DAY.

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