US2461452A - Code detecting means - Google Patents

Description

Feb.- 8, 1949.

H. A. THOMPSON CODE DETECTING MEANS 2 Sheets-Sheet 1 Filed July 1 1947 0 C Pl 4 27 i INVENTOR.

Fell 1949' H. A. THOMPSON CODE DETECTING MEANS Filed July l5, 1947 2 Sheets-Sheet 2 INVENTORQ T L f m ATTORNEY Patented Feb. 8, 1949 UNITED STATES FFICE CODE DETECTING MEANS Application July 15, 1947, Serial No. 760,985

15 Claims. 1

My invention relates to code detecting means and particularly to code detecting means'adopted for use in coded track circuit types of railway signaling systems.

Railway signaling systems of the coded track circuit type are arranged to apply coded track circuit energy to the exit ends of track sections for transmission through the track rails to code following relays either carried on a train in the section and inductively coupled with the track rails through the medium of train carried induction coils, or located in the wayside and arranged to be energized from the track rails. Ordinarily the coded track circuit current comprises alternate on and off intervals during which respec-. tively energy is and is not supplied to the track rails. The code following relays are provided with means for detecting the operation of the relay in response to coded energy, with the means arranged to assume one condition with the code following relay operates, that is, alternately picks up and releases in response to the receipt of coded track circuit energy, and to assume another condition whenever the code following relay ceases to operate in response to such coded energy.

Various means have been proposed to detect the coding operation of code following relays in railway signalin systems. One such means utilizes two slow releasing relays one of which is energized over a front contact of the track relay and the other of which is energized over a back contact of the code following relay and a front contact of the one relay maintained closed during the slow release interval of that relay. In such an arrangement the release times of the relays must be such that the one relay bridges the deenergized periods and the other bridges the energized periods of the codefollowing relay when it follows code. I

It is an object of my invention to provide means for detecting operation of a code following relay by means of two relays, one responsive to the periods of agreement, and the other responsive to periods of diagreement, between the positions of the code following relay and a repeater relay provided for such code following relay Another object of my invention is to provide novel and improved decodin means particularly adapted for use in coded track circuit systems of railway signaling.

Another object of my invention is to provide a relay type code detecting means utilizing slow releasing relays, only one of which is required to have an appreciable time release period.

Another object is to provide novel and im- (Cl. 246-34.)v

proved code detecting means arranged to provide protection against overlapping contacts on the code following relay.

The above mentioned and other important objects and characteristic features of my invention are attained by providing the code following relay with an auxiliary relay energized whenever the code following relay is picked up. Two controlled relays are provided and are controlled by the code following relay and auxiliary relay in such manner that one of the controlled relays is energized whenever the contacts of the code following relay and auxiliary relay are in corresponding positions, 7

relay. A front contact of one of the two con-.-'

trolled relays is interposed in the energiz ng circult of the other controlled relay which functions to indicate that the code following relay is operating in response to coded energy and may be utilized to control traffic governing functions in a signaling system.

I shall describe several forms of apparatus em-.- bodying my invention and shall then point out the novel features thereof in claims.

In the accompanying drawings, Fig. l is a diagrammatic View illustrating one form of appae ratus embodying my invention incorporated into a wayside railway signaling system. Fig. 1a is a diagrammatic view representing a modification of a portion of the apparatus shown in Fig, 1. Fig. 2 is a diagrammatic view illustrating another modification of the apparatus shown in Fig. 1. Fig. 3 is a diagrammatic view illustrating apparatus shown in Fig. 1 modified to provide pro? tection against overlapping contact on the code following relay. Fig. 4 is a time chart representing the relative periods of energization and deenergization of the relays illustrated in Fig. l, and also showing therelative periods of operation of the contacts of relays TR and TP.

In each of the several views similar reference characters refer to similar parts.

Referring to Fig. l, the reference characters I v and la designate the track rails of a stretch of 2 into a track section E-F which has a traiiic' controlling signal 8 located adjacent its entrance end E. Coded track circuit energy is supplied to the exit end F of the section in any suitable V 1 manner as, for example, through a circuit extend ing from rail I through contact In of a code transmitter CT, battery H and a resistor 12 to the other track rail la. The code transmitter CT is constantly energized from a suitable source of current, such as a battery not shown but having its opposite terminals designated by the reference characters B and C, and coder CT operates its contact I alternately into and out of engagement with its mating contact point of a rate of, for example, 75 or 180 times per minute so that periodically interrupted or coded current is supplied from battery H to the track rails to form a code pattern of the type represented by the uppermost diagram in Fig. l. A code following relay TR is connected across the track rails at the entrance end E of the section, and is periodically energized and deenergized in step with the supply of coded energy to the track rails as long as section E-F is vacant, as indicated by the second diagram of Fig. 4. Relay TR is provided with contacts which are operated as indicated in Fig. 4 to a front or first position whenever the relay is energized, and to a back or second position whenever the relay is deenergized.

Relay TR has associated therewith novel and improved code detecting means embodying my present invention, and comprising an auxiliary relay TP and two controlled relays A and D. Auxiliary relay TP is controlled over an obvious circuit including front contact l3 of relay TR and accordingly is energized whenever the contacts of relay TR are closed in their front positions, as represented by the third diagram of Fig. 4. Relay TP is proportioned to be slightly slow to pick up and has connected across its winding a resistor M in series with an asymmetric unit 15 poled to present its high resistance direction to the flow of current from terminal B. The rectifier-resistor combination is effective to provide a closed path across the winding of relay T? for the current induced in the relay by the decay of flux when its energizing circuit is opened; and preferably the rectifier-resistor combination is proportioned so that the release period of relay T? is substantially equal to its pick-up period. The release and pick-up periods of relay TP may be of the order of two-hundredths of a second and during these periods the armature of relay TP lags behind the energization of its winding so that its contacts remain closed in their back positions for approximately two-hundredths of a second after relay TP is energized, and remain closed in their front positions for approximately the same interval of two-hundredths of a second after relay TP becomes deenergized. The relation between the periods of energization of relay TP and the operation of its contacts is represented in the third diagram of Fig. 4 in which the vertical full lines indicate the times at which relay TP becomes energized or deenergized while the slanted dotted lines represent the period that the armatiue of relay Tl? lags behind the energization of its winding, the lines slanting upwardly from left to right indicating the slow pick-up periods of relay TP while the lines slanting downwardly from left to right indicating the slow release periods of the relay.

Due to this lag in the operation of the contacts of relay TP there will be a short interval following each operation of the contacts of relay TR between their front and back positions during which the contacts of relay TP are out of correspondence with the contacts of relay TR, following which the armature of relay TP will operate so that the contacts of relay TP assume a position of correspondence with the contacts of relay TR. The relays TR and TP are arranged to energize relay D during each of these periods when the contacts of relay TP are out of correspondence with the contacts of relay TR, while the relays TR and TP are arranged to energize the other relay A during intervals that the contacts of relays TR and TP are in correspondence. A front contact of one of the relays A and D is interposed in the energizing circuit of the other relay so that such other relay may be used as a detecting relay to indicate that relay TR is operating in response to coded energy.

In Fig. 1, relay D is shown provided with an energizing circuit including two circuit paths, one closed when contact iii of relay TR is in its front position and contact I! of relay TP is in its back position, and the other circuit path closed when contact 16 of relay TR is in its back position and contact H of relay '1)? is in its front position. The relative intervals of time that relay D is energized over the circuit just traced is represented by the fourth diagram in Fig. 4, and it will be apparent from an inspection of this diagram that relay D is energized for the intervals, corresponding alternately to the pick-up and release periods of relay TP, that the contacts of relay TP are out of correspondence with the contacts of relay TR. Relay D has connected across its terminals either a resistor or, as shown, a condenser IB, to provide slow releasing characteristics to the relay effective to hold the relay armature in its attracted position for the intervals between the periods of energization of its winding. Relay A is energized over a circuit path including front contact l9 of relay D and contacts 20 and 21 of relays TR and TP, respectively, the circuit being completed when contacts 26 and 21 are both closed in their front positions, or are both closed in their back positions. The periods of energization of relay A are shown in the bottom diagram of Fig. 4:, from which it will be noted that relay A is energized whenever the position of the contacts of relay TP is in correspondence with the position of the contacts of relay TR. Relay A has connected across its terminals a resistor 22 effective to snub this relay so that the relay will retain its armature in its picked up position for the relatively short periods of time that the energizing circuit for this relay is interrupted because of disagreement in position of the contacts of relays TP and TR. With the relays D and A controlled in the manner explained above, it is obvious that relay D will be energized and picked up only so long as relay TR is intermittently picked up and released to create recurrent periods of lack of agreement between the contacts of relays TR and TP in response to coded energy from the track rails, and similarly that relay A will be energized only when relay TR follows code. If relay TR is constantly released by the failure of power in the track circuit or by a train shunt in the section, relay TP will likewise be released with the result that relay D becomes deenergized because the contacts of relays TR and TP remain in agreement, and relay D will therefore release to open the circuit for relay Aso that even though contacts 20 and 2| of relays TR and TP are in agreement under this condition, relay A will be released to indicate that relay TR has ceased to follow code. Similarly, should relay TR be constantly held picked up for any reason as by the presence of foreign current in the track rails, relay Tl? will likewise be picked up and in such 5' condition relay D will become released to open the circuit for relay A which thereupon releases to indicate that relay TR has ceased to follow code. *In addition, should the circuit for relay TP become opened under either of the conditions mentioned above, relay TP will then retain its contacts closed in their back positions, and in such event if relay TR, is steadily released relay D will be deenergized so that relay A becomes re leased, while if relay TB is held steadily energized, relay D will be energized but relay A will be deenergized because of the lack of correspondence between contacts 2.8 and 2| of relays TR and TP. Relay A therefore functions as a code detecting relay and when picked up indicates that relay TR is following code. Relay A may therefore be utilized as is customary in railway signaling systems to control any desired form of trafilc governing devices such as, for example,

signal S shown controlled by contact 23 of relay A in a manner obvious from an inspection'o-f the drawing.

Fig. 1a. represents a modification of the apparatus of Fig. 1 in which contact is of relay D is omitted from the energizing circuit of relay A, while a front contact 24 of relay A is interposed in the energizing circuit of relay D. Relay D will therefore function as a code detecting relay in the same manner as explained hereinbefore whereby relay A functions as a code detecting relay in the circuits illustrated in Fig. 1. It is readily apparent that by providing two relays, one energized over circuits completed when the track relay and auxiliary relay contacts are in agreement, and the other relay energized when the track relay and auxiliary relay contacts are in disagreement, and by controlling either one of these two relays over the front contact of the other, such one relay will then function as a code detecting relay effective to distinguish between the coding and non-coding conditions of the code following relay.

In Fig. 2 I have represented the anparatus of i modified to require only a single movable cont-at on the track relay. This arrangement is of particular advantage in connection with relatively long coded track circuits of the type where the margin of energy available for the operation of the track relay limits the number of contacts operated thereby to a minimum. Referring now to Fig. 2, relay TR; when energized closes its front contact as to energize relay TP, and when relay TP picks up its front contact 21 c? to energize relay A in multiple with relay *iP. When contact 26 of relay TR drops to its back. position, relay 1) becomes energized during short interval that relay T 3 holds its front contact closed, over a circuit extending from terminal 5 through back contact 2% of relay TR, front contact 23 of relay TP, front contact 2!: of relay A and the winding of relay D to terminal C. When relay TP releases, relay A lee comes energized over a circuit passing through each contacts and 2? of relays TR and TP, r'e-' spectively, and when relay subsequently be comes energized. relay D- is energized again for the short interval of time that relay T? lags re lay TR over a circuit including front contact 26 of relay TR. back contact 28 of relay TP and front contact Ell of relay A. As shown, asymmetric units 36 are included in the circuit paths of relays TP and A presenting their low resistdirection to the flow of current in the energizing circuits for these relays. These units are eifective to prevent the tying in of thesnubhing' 'acteristics and immediately release.

circuits of relays TP and A and will confine the effectiveness of thosesnubbing circuits to the individual relays themselves. Also, a circuit connecting condenser it across the terminals of re lay D is carried over front contact 28 of relay A so that if this latter relay should release, relay D would then lose its slow releasing char- The apparatus of Fig. 2 will operate to detect the operation .of relay TR by code, in a manner corresponding to that hereinbefore described for Fig. l, and further detailed explanation is deemed unnecessary.

In Fig. 3 I have illustrated the apparatus of Fig. 1 modified to obtain protection against overlapping contacts on the code following relay by use of two-winding relays as agreement-disagreement relays. Referring now to Fig. 3, a single movable contact 2% of relay TB is utilized for controlling the energization of both windings of the two relays A and-D, and has its associated front stationary contact point connected to terminal B, and its back stationary contact point connected to terminal C. One winding 3! or the other Winding 32 of relay A is ener ized whenever contacts 2G and 2! of relays TR and TP, respectively. are closed in corresponding positions, winding 3! being energized when contacts at and ii are both closed in their corresponding front positions to complete a circuit extending from terminal B through front contact 2i! of re lay front contact 2! of relay TP and winding 3! of relay A to terminal C, while winding 32 is energized when contacts .26 and 2! are both closed in their back nosit-ions to. complete a air, cuitfrom terminal B through winding 32. back contact 2! of relay TP and back contact as of relay to terminal 0. The energization of the circuit path including the contacts 25! and 25 is of one polarity or the other according as the contacts 20' and 2! are. in corresponding front or back positions. respectively. but the windings Eli and 32 are arranged so that when-energized in the previously traced'the windings create in relay A fiures of the same relative polarity. and each winding has a resistor 22 connected across its terminals to retard the release of the armature of the relay when deenergized. The relea e of the armature of re ay A is at times additionally retarded during the intervals that contact 2;! of relay TP is o t of correspond once with contact 26 of relay TR by means of a short circuit oath comnlete'd when contact '29 of relay TB. is closed in its back nosition and con-- fact 2! of relay TR is closed in its front position, effective to connect terminal 0 of the source directly across both term nals of winding 3!, and by means of another short circuit path complated over front contact at of relay TR and hack contact 2! of relay TP effec ive to connect terminal B of the source across both terminals o windinq The, release ne ind of relav A is selected so t at the relav wi l bridge the relative short intervals. during which it is dee'nergized when contact 20 and iii are out of correspondence.

Relay D has its one winding 33 or its other winding as energized whenever contacts 2!! and 35 of rela s TR- and TP. respecti ely, are out/of corresnondence. nroyided that relay A holds its front contact 25 closed. Winding 33,0 relay D is energized over a circuit extending from. ter e urinal B throu'rh front contact 25 of relay front contact 2d of relay A. back: contact 35 of relay TP and winding 33 of relay D'to terminal 7 C, while winding 34 of relay D isenergized over a circuit extending from terminal 3' through winding 3t, front contact 35 of relay TP, front contact 2d of relay A and back contact 2% of relay TR to terminal C. The polarity of current supplied through contacts 20 and 35 to winding 33 is opposite to that supplied to winding 35, but the windings 33 and 3%, when energized in the manner traced above, will create fluxes in relay 3;.- of the same relative polarity, and each winding 33 and 3:; has a resistor 36 connected across its terminals to retard the release of its armature when deenergized. In addition, with front contact 24 of relay A closed, winding 33 has a short circuit path connected across its terminals when contacts 26 and 35 of relays TR and TP, respectively, are both in their back positions, while winding 34 has a short circuit path connected across its terminals when contacts v and 35 are both closed in their front positions. The release period of relay D is selected so that the relay will maintain its armature in its picked up position for the intervals that its energizing circuit is interruoted by contacts 20 and 35 of relays TR, and '1'? being in corresponding positions.

The apparatus of Fig. 3 will operate in a manner corresponding to that hereinbefore described in connection with the description of the apparatus of Fig. l, to detect the coding and noncodlng operation of relay TR, and further detailed description of the operation of the apparatus of Fig. 3 is believed to be unnecesary. It is to be noted, however, that if movable contact element 28 of relay TR should bridge between its associated front and back points, or if those points should overlap, then in such event terminal B will b connected directly to terminal C through movable contact element 20 and neither relay A nor D will be energized during the periods that such contact bridging occurs. The arrangement illustrated in Fig. 3 therefore provides protection against improper operation of the agreement-disagreement relays A and D in the event of overlapping contacts on the code following relay.

-It is to be understood that while in Figs. 2 and 3 I have represented agreement relay A controlling through its front contact 24 the circuit for disagreement relay D,-which latter relay functions as a code detecting relay, the arrangements may readily be modified to provide for relay D controlling the circuit for relay A, in which case relay A will function as a code detecting relay, as indicated in Fig. 1 of the drawings. The system organization is thus such that a code detecting means is provided by utilizing a repeater relay for the code-folowing relay, by controlling a first of two relays'over' a circuit completed when the contacts of the code following and repeater relays are in agreement, by controlling the second of the two relays over a circuit completed when the contacts of the code following and repeater relays are in disagreement, and by further controlling the circuit of either one of the two relays by a front contact of the other of the two relays, the one relay then functioning to detect between coding and non-coding operation of the code following relay.

An advantage of the code detecting means embodying my invention is that of the two relays utilized to check the agreement and disagreement between the code following relay and its repeater, only one of such two relays needbe provided with a slow release. period of relatively long duration while the otheris required to bridge only the short intervals during which the code following relay and. its repeater are out of agreement. Further advantages reside in the arrangement permitting the use of the code detecting means in long track circuits where it is desirable to employ only a single movable contact on the code following relay, and in the arrangement which provides protection against overlapping or bridging contacts on the code following relay.

Although I have herein shown and described only a few forms of code detecting means embodylng my invention, it is understood that various changes and modifications may be made therein within the scope of the appended claims without departing from the spirit and scope of my invention.

Having thus described my invention, what I claim is:

1. In a coded track circuit system of signaling for a section of railway track having means for supplying coded energy to the track rails at one end of said section and having a code following track relay receiving energy from the track rails at the opposite end of said section, said code following track relay having contacts which are operated to a first position when said relay is energized and to a second position when said relay is deenergized, the combination with said track relay of an auxiliary relay energized when said track relay contacts are in said first position and having contacts operable to a first position or second position according as said auxiliary relay is or is not energized, said auxiliary relay operating its contacts slightly out of step with its energization, two slow releasing controlled relays each having contacts closed in a first position when energized, an energizing circuit for afirst of said two relays including in series contacts of said track and auxiliary relays and closed when said contacts are in corresponding positions, an energizing circuit for the second of said two relays including in series contacts of said track and auxiliary relays and closed when the contacts of said auxiliary relay are out of correspondence with the contacts of said track relay, a first position contact of oneof said two controlled relays interposed in the energizing circuit of the other of said two controlled relays, and traffic governing means for said section controlled by said other controlled relay.

2. In a coded track circuit system of signaling for a section of railway track having means for supplying coded energy to the track rails at one end of said section and having a code following track relay receiving energy from the track rails at the opposite end of said section, said code following track relay having contacts which are operated to a first position when said relay is energized and to a second position when said relay is deenergized, the combination with said track relay of auxiliary relay energized when said track relay contacts are in said first position and having contacts operable to a first position or second position according as said auxiliary relay is or is not energized, said auxiliary relay operating its contacts between their first and second positions slightly out of step with the energization of said relay, two slow releasing controlled relays, an energizing circuit for a first of said two relays including in series a contact of said track relay and a contact of said auxiliary relay and closed when said contacts are 9 V out of corespondence, an energizing circuit for the second of said two relays including in series a front contact of said first rela and a contact of said track relay and a contact of said auxiliary relay and closed when the contacts of said track and auxiliary relays are in corresponding positions, and trafiic governing means for said section controlled by said second controlled relay.

3. In a coded track circuit system of signaling for a section of railway track having means for supplying coded energy to the track rails at one end of said section and having a code following track relay receiving energy from the track rails at the oposite end of said section, said code following track relay having contacts which are operated to a first position when said relay is energized and to a second position when said relay is deenergized, the combination with said track relay of: an auxiliary relay energized when said track relay contacts are in said first position and having contacts operable to a first position or second position according as said auxiliary relay is or is not energized, said auxiliary relay operating its contacts between their first and second positions slightly out of step with the energization of said relay, two slow releasing controlled relays, an energizing circuit for a first of said two relays including in series contacts of said track and auxiliary relays and closed when said contacts are in corresponding positions, an energizing circuit for the second of said two relays including in series a front contact of said first controlled relay and a contact of said track relay and a contact of said auxiliary relays and closed when the track and auxiliary relay contacts are out of correspondence, and traific governing means for said section controlled by said second controlled relay.

4. In a coded track circuit system of signaling for a section of railway track having means for supplying coded energy to the track rails at one end of said section and having a code following track relay receiving energy from the track rails at the opposite end of said section, said code following track relay having a single movable contact which is operated to a first position when said relay is energized and to .a second position when said relay is deenergized, the combination with said track relay of: an auxiliary relay energized when said track relay contact is in said first position and having contacts operable to a first position or second position according as said auxiliary relay is or is not energized, the operation of the contacts of said auxiliary relay lagging slightly behind the energization of that relay, two slow releasing controlled relays each having contacts closed to a first position when energized, an energizing circuit for a first of said .two relays including in series said contact of said track relay and a contact of said auxiliary relay and closed when said contacts are in corresponding positions, an energizing circuit for the second of said two relays including in series said contact of said track relay and a contact of said auxiliary relay and closed when the two contacts are out of. correspondence, a first position contact of one of said two controlled relays interposed in the energizing circuit of the other of said two controlled relays, and traffic governing means for said section controlled by said other controlled relay.

5. In a coded track circuit system of signaling for a section of railway track having means for supplying coded energy to the track rails at one end of said section and having a code following track relay receiving energy from the track rails atthe opposite end of said section, said code following track relay having a single. movable con.- tact which is operated to a firstposition when said relay is energized and to a second position when said relay is deenergized, the combination with said track relay of: an auxiliary relay energized when said track relay contact is in said first'position and having contacts operable to a first position or second position according as said auxiliary relay is or is not energized, the operation of the contacts of said auxiliary relay lagging slightly behind the energization of that relay, two slow releasing controlled relays each having contacts closed in a first position when energized, an energizing circuit for a first of said two relays including in series said contact of said track relay and a contact of said auxiliary relay and closed when said contacts are in corresponding positions, an energizing circuit for the second of said two relays including in series a front contact of said first controlled relay and said track relay contact and a contact of said auxiliary relay and closed when said track and auxiliary relay contacts are out of correspondence, and trafiic governing means for said section controlled by said second controlled relay.

6. In a coded track circuit system of signaling for a section of railway track having means for supplying coded energy to the track rails at one end of said section and having a code following track relay receiving energy from the track rails at the opposite end of said section, said code following track relay having contacts which are operated to, a first position when said relayis energized and to a second position when said elay i deenere ed the o na i n with said track relay of an auxiliary relayenergized when said track relay contacts are in said first position and having contacts operable to a first position or second position according as said auxiliary relay is or is not energized, said auxiliary relay operating its contacts slightly out of step with its energization, two two-winding relays, a source of current having its opposite terminals connected respectively to the first and second position stationary contact elements of a movable contact of said track relay, a circuit energizing one winding or the other of a first of said two two-winding relays when said track relay movable contact corresponds in position'to a contact of said auxiliary relay, the energizacuiting the last energized one of said two wind-V ings of said first two-winding relay, a circuit energizing one winding or the other of the second of said two two-winding relays when said track relay movable contact is out of correspondence with a contact of said auxiliary relay, the energization of said circuit being of one polarity or the other according as said movable' contact is in its said first or second position respectively and said windings being arranged when energized to create fluxes of the same relative polarity;

a circuit path completed when said movable contact operates to a position of correspondence with said auxiliary contact for short circuiting the last energized one of said-two windings of said first two-winding relay, a front contact of -1'1 one of said two two-winding relays interposed'in the energizing circuit ofthe other of such relays, and means for governing traffic in said section controlled by said other two-winding relay.

7. In a coded track circuit system of signaling for a section of railwaytrack having means for supplying coded energy to the track rails at one end of said section and having a code following track relay receiving energy from the track rails at the opposite end of said section, said code following track relay having contacts which are operated to a first position when said relay is energized and to a second position when said relay is deenergized, the combination with said track relay of: an auxiliary relay energized when said track relay contacts are in said first position and having contacts operable to a first position or second position according as said auxiliary relay is or is not energized, said auxiliary relay operating its contacts slightly out of step with its energization, two two-Winding relays, a source of current having its opposite terminals connected respectively to the first and second position stationary contact elements of a movable contact of said track relay, a circuit energizing one winding or the other of a first of said two twowinding relays when said track relay movable contact corresponds in position to a contact of said auxiliary relay, the energization of said circuit being of one polarity or the other according as said movable contact is in its said first or second position respectively and said windings being arranged when energized to create fluxes of the same relative polarity, a circuit: path completed when said movable contact operates to a position out of correspondence with said auxiliary relay contact for short circuiting the last energized one of said two windings of said first two-winding relay, a circuit including a front contact of said first two-winding relay for energizing one winding or the other of the second of said two two-winding relays when said track relay movable contact is out of correspondence with a contact of said auxiliary relay, the energization of said circuit being of one polarity or theother according as said movable contact is in its said first or second position respectively and said windings being arranged when energized to create fluxes of the same relative polarity, a circuit path completed when said movable contact operates to a position in correspondence with said auxiliary contact for short circuiting the last energized one of said two windings of said first two-winding relay, and means controlled by said second two-winding relay for governing traffic in said section.

8. Code detecting means for detecting operation of a code following relay in response to coded energy, comprising a repeater relay repeating said code following relay and having contents operated slightly out of step with its energization, means for detecting correspondence between the contacts of said code following relay and its repeater, means for detecting lack of correspondence between the contacts of said code following relay and its repeater. and means further controlling one of said means by the other whereby said one means functions to detect between coding and non-coding operation of said code following relay.

9. Code detecting means for detecting operation of a code following relay in response to coded energy, comprising a repeater relay repeating said code following relay and having contacts operated slightly out of step with its energization, means for detecting lack of correspondence between the contacts of said code following relay andltsrepeater, and means controlled bysaid lack of correspondence detecting means'for detecting correspondence between the contacts of said code following relay and its repeater whereby to detect between coding and non-coding operation of said code following relay. V

10. Code detecting means for detecting operation of a code following relay in response to coded energy, comprising a repeater relay repeating said code following relay and having contacts operated slightly out of step with'its energization, means for detecting correspondence between the contacts of said code following relay and its repeater, and means controlled by said correspondence detecting means for detecting lack of correspondence between the contact of said code following relay and its repeater whereby to detect between coding and non-coding operation of said code following relay.

11. Code detecting means for detecting operation of a code following relay by periodically coded energy comprised of alternate on and ofi intervals during which energy respectively is and is not supplied to said relay, said code following relay having contacts which are operated to a first position when the relay is energized and to a second position when the relay is deenergized, said means comprising the combination with said code following relay of an auxiliary relay energized when said code following relay contacts are in said first position and having contacts operable after a slight delay to a first position or secend position according as said auxiliary relay is or is not energized, two slow releasing controlled relays each having contacts closed in a first position when energized, an energizing circuit for a first of said two relays including in series contacts of said code following and auxiliary relays and closed when said contacts are in corresponding positions, an energizing circuit for the second of said two relays including in series contacts of said code following and auxiliary relays and closed when said contacts are out of correspondence, and a first position contact of one of said two controlled relays interposed in the energizing circuit of the other of said two controlled relays.

12. Code detecting means for detecting operation of a code following relay by periodically coded energy comprised of alternate on and off intervals during which energy respectively is and is not supplied to said relay, said code following relay having contacts which are operated to a first position when the relay is energized and to a second position when the relay is deenergized, said means comprising the combination with said code following relay of: an auxiliary relay energized when said code followin relay contacts are in said first position and having contacts operable after a slight delay to a first position or second position according as said auxiliary relay is or is not energized, two slow releasing controlled relays, an energizing circuit fora first ,of said two relays including in series contacts of said code following and, auxiliary relays and closed when said contacts are in corresponding positions, and an energizing circuit for thesecond of said two relays including in series a front contact of said first relay and a contact of said code following and a contact of said auxiliary relay and closed when the contacts of said code following and auxiliary relays are out of correspondence.

13. Code detecting means for detecting operation of a code following relay by periodically codedenergy comprised of alternateon and ofi lnter vals during which energy respectively is and is not supplied to said relay, said code following relay having contacts which are operated to a first position when the relay is energized and to a second position when the relay is deenergized, said means comprising the combination with said code following relay of: an auxiliary relay energized when said code following relay contacts are in said first position and having contacts operable after a slight delay to a first position or second position according as said auxiliary relay is or is not energized, two slow releasing controlled relays, an energizing circuit for a first of said two relays including in series contacts of said code following and auxiliary relays and closed when said contacts are out of corresponding positions, and an energizing circuit for the second of said two relays including in series a front contact of said first relay and a contact of said code following and a contact of said auxiliary relay and closed when the contacts of said code following and auxiliary relays are in correspondence.

14. Code detecting means for detecting operation of a code following relay by periodically coded energy, said code following relay having a single movable contactwhich is operated to a first position when the relay is energized and to a second position when the relay is deenergized, said means comprising the combination with said code following relay of an auxiliary relay energized when said code following relay contact is in said first position and having contacts operable after a slight delay to a first position or second position 7 according as said auxiliary relay is or is not energized, two slow releasing controlled relays having contacts closed in a first position when energized, an energizing circuit for a first of said two relays including in series said movable contact of said code following relay and acontact of said auxiliary relay and closed when said contacts are in corresponding positions, an energizing circuit,

for the second of said two relays including in series said contact of said code following relay and a contact of said auxiliary relay and closed when the contacts of said code followin and auxiliary relays are out of correspondence, and a first position contact of one of said two controlled relays interposed in the energizing circuit of the other of said two controlled relays.

15. Code detecting means for detecting operation of a code following relay by periodically coded energy comprised of alternate on and off not supplied to said relay, said code following relay having contacts which are operated to a first position when said relay is'energized and to a second position when said relay is deenergized, said means comprising the combination with said code following relay of: an auxiliary relay energized when said code following relay contacts are in said first position and having contacts operable to a first position or second position according as said auxiliary relay is or is not energized, said auxiliary relay operating its contact slightly out of step with its energization, two two-winding relays, a source of current having its opposite terminals connected respectively to the first and second position stationary contact elements of a movable contact of said code following relay, a circuit energizing one winding or the other of a first of said two two-winding relays when said code following relay movable contact corresponds in position to a contact of said auxiliary relay, the energization of said circuit being of one polarity or the other according as said movable contact is in its said first or second position respectively and said windings being arranged when energized to create fluxes of the same relative polarity, a circuit path completed when said movable contact operates to a position out of correspondence with said auxiliary relay contact for short circuiting the last energized one of said two windings of said first two-winding relay, a circuit energizing one winding or the other of the second of said two two-winding relays when said code following relay movable contact is out of correspondence with a contact of said auxiliary relay, the energization of said circuit being of one polarity or the other according as said movable contact is in its said first or second position respectively and said windings being arranged when energized to create fluxes of the same relative polarity, a circuit path completed'when said movable contact operates to a position a of correspondence with said auxiliary contact for short circuiting the last energized one of said two windings of said first two-winding relay, and a front contact of one of said two two-winding relays interposed in the energizing circuit of the other of such relays;

'HOWARD A. THOMPSON.

No references cited.

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