US2552862A - Block indication apparatus for centralized traffic control systems of the normally inactive reversible coded track circuit type - Google Patents

Description

y 1951 F. T. PASCOE ET AL 2,552,862

0N APPARATUS FOR CENTRALIZED TRAFFIC BLOCK INDICATI CONTROL SYSTEMS OF THE NORMALLY INACTIVE REVERSIBLE CODED TRACK CIRCUIT TYPE Filed Aug. 13, 1946 3 Sheets-Sheet 1 0 2; T wzw T 1 rd 5 M w 7 May 1 51 F. T. PASCOE ET AL 2,

BLOCK INDICATION APPARATUS FOR CENTRALIZED TRAFFIC CONTROL SYSTEMS OF THE NORMALLY INACTIVE REVERSIBLE CODED TRACK CIRCUIT TYPE Filed Aug. 13, 1946 5 SheetsSheet 2 Q wk vb m wmwsww INVENTORS [Ivan aSCOQ 5 4 LJamme THEIR ATTORNEY M y 1951 F. T. PASCOE ET AL 2,5 2,862

BLOCK INDICATION APPARATUS FOR CENTRALIZED TRAFFIC CONTROL SYSTEMS OF THE NORMALLY INACTIVE REVERSIBLE CODED TRACK CIRCUIT TYPE Filed Aug. 13, 1946 3 Sheets-Sheet 3 r 457% z-dlp M530 0 amp- 0 v 05 J6 T IPZS'T ah" i {v94 i. P m

I H PL .kmzzze 3 Fig.2.

THEIR ATTORNEY Patented May 15, 1951 BLOCK INDIGATION APPARATUS FOR GEN-- TRALIZED TRAFFIC CONTROL SYSTEMS or THE NORMALLY INACTIVE REVERTSI BLE conED TRACK omcUIT TYPE Frank T. Pascoe, Carnegie, and Arthur L. Jerome, Edgewood, 'Pa., assignors to TheUnion Switch & Signal Company, Swissvalc, Pa-, a corporation of Pennsylvania Application August 13, 1946, Serial m terials 6 Claims. 1

Our invention relates to railway traffic controlling apparatus, and more particularly to improved means for controlling the occupancy indication means in an absolute permissive block signaling system of the centralized trafiic control "type in which the signals are controlled in accordance with trafiic conditions bya normally inactive system of coded reversible track circuits.

An object of our invention is to provide improved means forcontrolling the occupancy indication lamp for a single track stretch so that it will cause the occupied indication to be displayed only when the track stretch is occupied.

A further object of the invention is to provide improved means of the type described which is arranged so that the occupied indication willnot be displayed temporarily because of differences in the order of transmission of indication codes from thefield stations of the centralized traffic control system at opposite ends of the stretch or because transmission of these indication codes 7 is deferred or delayed for an interval.

Another object of the invention is to provide improved means of the type described which is arranged so that the occupied indication is certain 'to be displayed when the stretch is occupied.

A further object of the invention is to provide improved means of the type described for use in connection with a track stretch where the block clear indication is at times provided from one end and at other times is provided from the other end of a stretch, the equipment being arranged so that after a clear block indication has been sent to the ofiice from the station at one end of the stretch, and a signal clear control code is thereafter transmitted, the clear block indication at the office will be maintained until an indication is transmitted to the office from the station at the other end of the stretch showing that the stretch is clear or that a train has entered the stretch.

Another object of the invention is to provide improved means of the type described which is arranged so that it will not interfere with the interlocked trafiic control circuits in the C. T. C. machine which are governed by the block indication codes transmitted from the field stations.

Other objects of the invention and features of novelty will be apparent from the following description taken in connection with the accompanying drawings.

.We shall describe one form of railway trafiic controlling apparatus embodying our invention and shall then point out the novel features there of in claims.

In the drawings Figs. 1A and 13, when placed together with Fig. 1A at the left, forma diagram of a stretch of single track railway equipped with a coded track circuit signaling system of a type with which the block indication means provided by this invention is adapted to be employed, and

Fig. 2 is a diagram of the circuits in the C. T. C. machine at the control oflice for controlling the wayside equipment shown in Figs. 1A and 1B and for indicating atthe oflice the nature of traffic conditions in the stretch.

In practicing our invention we provide additional stick circuits for the blockindication relays at the ofiice. These stick circuits are arranged so that upon transmission of a signal clear control code the block indication relay which .is'governed "from the'eXit end of the stretch for the established direction of traffic will not release upon receipt of an occupied block indication code from the associated field station but will remain picked up until the "block indication relay which is governed from the field station at the other or entrance end of the stretch is picked up, or until the indication relay for the detector section at the entrance end is picked up to show that a train has entered the stretch. The block indication relays control the block indication lamp so that the occupied indication is displayed when and only when both block indicationrelays are released. In the accompanying drawings, in order to illustrate our invention in a simple manner we have shown itapplied to a specific system of the type referred to, namely, that disclosed in Letters Patent of the United States, No. 2,344,333, issued March 14, 1944 to J ames J. Van Horn for Railway Traflic Controlling Apparatus, which patent was reissued as No. 22,780, on August 13, 1946. It will be understood, however, that our invention is not limited to use with this system but can readily be applied to other systems of the same general nature. To facilitate an understanding of our invention, we have employed reference characters similar to those of this patent, that to say, each relay shown herein which-corresponds to one shown in the patent is identified by the same reference character.

Referring to Figs. 1A and 1B of the drawings there is shown therein a stretch of-single track railway extendin between two passing sid-ings and provided with wayside signal apparatus for authorizing traffic to move in one direction through the stretch at times and to move in the otherdirection at other times. In this application only the portions of the wayside apparatus essential to the understanding of this invention have been shown and the remainder of the equipment may be arranged as shown in the aboveidentified patent to James J. Van Horn.

, The equipment at the left-hand or west end of the single track stretch includes a C. T. C. system field station unit designated Station [-2, and the equipment at the right-hand or east end of the stretch includes a C. T. C.- system field station unit designated Station 3-4.

a The field station units are connected with th office over a pair of line wires, not shown, by a code communication system which may be of the type shown in Letters Patent of the United States No. 2,229,249, issued January 21, 1941 to L. V. Lewisfor Remote Control Systems.

Consideration of the detailed mode of operation of the code communication system is not needed for an understanding of our invention and it is deemed sufiicient to point out that one or more field stations are provided at each end'of each track stretch to be controlled and that coding unitsare provided at the office and at each field station and are connected by a pair of line wires, not shown, over which control codes are transmitted at times to a selected field station,

and at other times indication codes are transmitted over the same line wires to the ofiice without interference. Transmission of each code includes the temporary establishment of aplurality of communication channels, such, for example, as seven, between the office and a station to position a grouplof relays.

' Each code includes a distinctive code call by means of which a selector relay i-ZS or 34S, at the oifice and a similar relay, not shown, at one station only is energized to effect temporary establishment of seven'communication channels between the ofiice and the station. The difierent stations have different code calls, consequently the selector relays for different stations or panels are not energized at the same time,:and the same channels provide communication at different times with all of the stations.

The explanation of this invention requires only two channels employed in the transmission of control codes and two channels employed in the transmission of indication codes, and in order tosimplify the disclosure other channels and related apparatus have not been shown.

The channels employed in the transmission of control codes are designated 1 and 4, and the channels employed in the transmission of indication codes are designated 9 and [0.

It is to be understood that the system of our invention is made up of a number of unit portions generally similar to the one shown in the drawings, but as the invention may be fully understood from one such portion, only one has been illustrated in the drawings. 7

The office and field stations as well as the intermediate signal location are each provided with a suitable source of direct current, such as a storage battery, not shown, the terminals of which are designated B and C in the drawings.

In most cases in the drawings the relay contacts are located directly under the winding of the relay, but in some cases in order to simplify the drawings, relay contacts are separated cating relays to provide connection from terminal B of a source of current to the indication channels to effect delivery of indication codes over the line wires during the time that a delivery relay D at the oflice is energized to thereby position agroup of indication relays in accordance with the condition of energization of the indication channels. The circuits for energizing the starting relays at the field stations are arranged in the manner shown in detail in the above-identified patent to Lloyd V. Lewis. These circuits have. been omitted in order to simplify this disclosure.

The indication relays at the ofiice governed from the field station l2, at the left-hand or west end of thesingle track stretch, include a track indication relay ITK, Fig. 2, which controls a lamp, not shown, in the track diagram of the control machine to indicate the occupancy, of a short detector section 1T, Fig. 1A, containing the track switch at that end of the stretch, the relay lTK being controlled by the track relay, ITR for the track section lTyand'a block indication re.'- lay ZWTK which is governed by traffic conditions in the single track stretch as hereinafter explained in detail. A track indication relay 3TK and a block indication relay dETK atthe ofiice are governed in a similar manner through the field station 3- 1 at the right-hand end of the single track stretch.

The block lamp 26BKE in the trackdiagram of the control machine is, governed by relays ZWTK and GETK, and also by trafiic relays iEFK and ZWFK, as hereinafter explained, so as to be lighted when the stretch is occupied.

The signal levers ZSIG and ASIG on the panel of the control machine of Fig. 2 are the usual three-position levers for the code control of the signal control relays at the field stations at the opposite ends of the stretch. A two-position traffic lever 2-4TFK is also mounted on the panel of the C. T. C. machine and governs a master directional polarized relay 24LP to thereby control the transmission of control codes to govern the traific control relays at the field stations at the ends of the stretch and thus control the coded track circuit apparatus to cause it to prepare the single track stretch for traific in one direction or the other.

The relay 2--4LP has associated therewith traflic indication relays ZWFK and ZEFK which 7 are stick repeaters of the block indication relays a release relay which picks up to cause elements from the relay winding and in these instances the relay with which the contacts are associated is designated by appropriate reference characters placed above the contacts. The equipment at each field station includes starting relay, not shown, which responds to a change in position of any of the associated indi- The relays 2NG, 211G, ERG, GNG, LG and lRG are controlled substantially in the same manner as are the relays 2--4FL and'2-4FLO, shown and described in our application for Letters Patent of the United States, Serial No. 592,947; filed May 10, 1945, now Patent No. 2,528,073 dated October 31, 1950.

The traffic lever 24TFK is preferably of the push-turn type such as is shown in Letters Patent of the United States No. 2,289,736, issued July 14, 1942, to C. S. Snavely and R. H. Zetwo.

The push buttons i-ZSTB and .l-tSTB are the starting buttons for operating the usual code starting relays i2ST and 3ST by means of which control codes are initiated and the corresponding stations selected. Each starting relay when energized initiates a control code as described in Lewis Patent No. 2,229,249 including a code call for energizing a selector relay S for the same panel. Each selector relay when ehergized releases the associated starting relay and connects terminal B of a local source of energy to selected ones of the control channels in accordance with the position of the contacts of relay 2-4LP and of relays 2RG and ENG or All: and dNGr.

The equipment is arranged so that when energy is applied to channel I and a control code is transmitted to a field. station, the traffic control relay WFSR or EFSR at that station is operated to condition the wayside apparatus to make that end an exit or a leaving end. Similarly, the equipment is arranged so that when energy is not applied to channel i and a control code is transmitted to a field station, the traffic control. relay is operated to condition the wayside apparatus to make that end of the stretch an entrance end so that the signal at that point may be com trolled by the wayside circuits on operation of the associated signal control relay.

The equipment is also arranged. so that when energy is supplied to the code channel i, and a control code is transmitted to a field station, a signal control relay RHSR or Ll-ISR at that station is operated to render the signal subject to the control of the wayside circuits. When energy is not supplied to the code channel 5 governing a signal control relay, and a control code is transmitted to a field station, the signal control relay at that station is operated to keep the signal at stop irrespective of the condition of the wayside circuits.

The equipment at the office includes a repeater relay MBP which is governed as shown in Fig. 2

by the counting relay O3 and the master relay OM of the office coding unit of the Lewis patent in such manner that the relay is normally energized and is momentarily deenergized during the eighth step of a control code.

The equipment is shown in the condition which it assumes when the track stretch is vacant, the signals ER and 3L are at stop, and the signaling apparatus prepares the stretch for westbound traffic.

Referring to Fig. 2 of the drawings, the contacts of the master directional relay 2-4LP-are in their left-hand or normal positions in which they designate westbound traffic in the associated single track stretch. At this time the block indication relay ZWTK is energized by current supplied over its stick circuit which is traced from terminal B of the source over back contact 28 of relay ETK, back contact ii of relay AETK,

front contact 2'2 of relay ZWTK, back contact 23 of delivery relay OI-'-2D, winding of relay '2WTK, back contact 25 of relay AEFK, and normal polar contact'Zti of relay 2--4LPto terminal C. Accordingly, contact 2? of relay ZWTK is picked up and interrupts the circuit of :the blo'ck indication lamp 2-4BKE and this lamp is err-' tinguished to indicate that the single track stretch between signals 2R and 4L is not occupied.

At this time the westbound traffic indication relay EWFK is energized by current supplied over both its pick-up and stick circuits which are traced from terminal B over normal polar" contact '28 of relay 2- tLP, front contact 29 of relay ZWFK and front contact 35 of relay TVV IIKf in parallel, back contact 35 of relay SEFK, and winding of relay ZWFK to terminal 0. As relay" ZWFK is picked up, its front contact 32 in the circuit of the lamp Z- iBKE. is closed so that energy will be supplied to the lamp on release of relay ZW'IK.

As traflic indication relay 2WFK is picked up, its contact 35 in the circuits of the windings of the relay 2-dLP is open, but at this time front contact 36 of block relay 2WTK is closed and permits energy to be supplied to the lower winding of relay 2- iLP on movement of the lever 2--4TFK, provided conditions are proper as hereinafter explained.

As traffic indication relay 2WFK is picked up, its contact 42 in the pick-up circuit for relay 4LG is closed and this relay may be picked up as hereinafter explained.

As the contacts of relay 2- iLP are in their left-hand position, contact 38 connects terminal 13 of the battery to the circuit governed by front. contact 39 of selector relay l-2S for supplying energy to terminal I of the ofiice coding unit "so that control codes sent to field station l-2 atv the left-hand end of the stretch will pickup traffic control relay ZWFSR, or will maintain it: picked up if it is picked up. At this time contact as of relay 2--4LP interrupts the supply of energy to terminal I of the office coding unit over the circuit governed by front contact 40 of selector relay 3-43 so the control codes sent to field station 3-4 at the right-hand end of the stretch will release the traffic control relay 4EF'SR or will cause it to remain released if it is released.

Turning to the wayside apparatus, the relay 2WFSR, Fig. 1A, at the left-hand end of the single track stretch is picked up and is energized by current supplied over its stick circuit. Accordingly, front contact 44 of relay ZWFSR in the circuit of the code transmitter relay ZR'ICTM is closed but this circuit is open at contact 45 of a slow release front contact repeater relay 2RTFSA which is picked up as explained below.

Referring to Fig. 113 it will be seen that traffic control relay lEFSR, is released, and that sig nal control relay 4LHSR, which governs clearing of signals @LA and iLC, is also released. Accordingly, energy is supplied over backccontact 46 of relay ALHSR, back contact 417 of relay 4EFSR, and front contact 48 of the track-relay 3TB. to a code transmitter relay 4LTC'IM and its contact is picked up to connect the track "battery 4ETB across the track rails through the winding of the track relay iLTR in the wrong direction to pick up the relay contacts. The energy supplied from battery lETB'to the track rails feeds over back contact tifl of a code transmitter relay dRTCTM to the winding of the track relay lRTR and picks up its contact -5l to supply energy to its slow release front contactre- .peater relay ARTFSA. As relay ARTE/is steadily picked up, the code following repeater relay '2 4TM and the slow release back contact 1T6- .peater relay 2--4BSA of the track relays=-2LTR '7 and ifiTfi remain released and energy is not supplied through the decoding transformer so the code detecting relays 2-4HR and 2-4DR arereleased. At this time the directional stick relays ZWS and 4E5 are also released so steady energy is supplied to a code transmitter relay ZLTCTM over the circuit which includes front contact 60 of relay 4RTFSA, back contact 6| of relay lES, back contact 62 of relay 2-4HR, and back contact 63 of relay ZWS. Accordingly, the contact of relay 2LTCTM is picked up and connects the battery ZWTB across the track rails through the winding of the track relay 2LTR in the wrong direction to pick up the relay contacts.

The energy supplied from battery ZWTB to the track rails is supplied over the back contact of the code transmitter relay 2RTCTM to track relay ZRTR and picks up its contact to energize a code following repeater relay 2T1VI, which in turn establishes a circuit to energize the slow release repeater relay 2RTFSA. As relay ZTM is steadily energized, a slow release back contact repeater relay ZRTBSA remains released and energy, is not supplied through the decoding transformer to the decoding relays ZRCDR- and 2RDR and they remain released. Accordingly, energy is supplied overback contact 15 of relay 2RDR, back contact 11 of relay ZRCDR, front contact 18 of relay ZRTFSA, and front contact 19 of relay ZWFSR to terminal 9 of'the field station l-2 so that indication codes sent to the ofiice from this station cause the block indication relay ZWTK to be picked up. 7

As the stretch is vacant, the track relay lTR for the detector section IT is picked up and its contact 80 interrupts the circuit leading to terminal ll] of the field station unit and indication codes sent from this station cause relay ITK at the office to be released.

Similarly, at the right-hand end of the stretch the track relay 3TB for the detector section 3T is picked up and interrupts the circuit leading to terminal of the associated field'station 34 and thus causes indication codes sent from this station to release relay 3TK at the ofiice. In addition, at this time, the circuits leading to terminal 9 of field station 3- are interrupted so indication codes sent from this station to the office release relay AETK. 7

If the operator wishes to clear one of the signals 4L to permit a Westbound train to enter the stretch, he may do so by moving the signal lever 4SIG to its left-hand position and pressing the starting button 34STB to pick up relay 3-4ST and initiate transmission of a control code to field station 34.

When the office coding unit operates to transmit the station selection steps of the control code for station 3-4, the selector relay 3-4S is picked up, while the relay M8P releases momentarily during the eighth step of the control code; which step occurs subsequent to picking up of relay 3-45. During the period in which the relay M8P is released and relay 34S is picked up, energy is supplied to the signal clearing relay 4LG over the circuit which is traced from terminal B over back contact 82 of relay M8P, front contact 83 of relay 34S, contact 84 of lever 4SIG, front contact 42 of relay ZWFK, and back contact 86 of relay lRG to the right-hand terminal of the winding of the relay 4LG, while the left-hand terminal of the relay winding is connected over back contact 81 of relay 4NG and back contact 88 of relay O3-4D in multiple, and

8'. thence over back contact 90 of relay 3TK to terminal C. When relay 4LG picks up, its contact 9| establishes connection from terminal 13 to the right-hand terminal of the relaywinding to keep the relay energized after relay M8P picks up and relay 3--4S releases.

The relay ll-2G is controlled in substantially the same manner as relay LG and is picked up when a control code is transmitted to clear signal 43. The details of the control of relay ERG are not essential to the understanding of this invention and are omitted to simplify this disclosure.

The relay 4NG is employed when a control code is transmitted to put a signal to stop, and corresponds to the relay 2-4FLO of our application Serial No. 592,947 hereinbefore referred to. V 7

When relay ALG picks up, a circuit is established over its front contact 92, back contact 93 of relay 4N6, and front contact 93 of relay 34S to input terminal 4 of the oflice coding unit so that the control code sent to field station 34 will pick up the signal control relay ALHSR.

In addition, when relay lLG picks up, its contact 9'! establishes a circuit shunting the contact 23 of delivery relay Ol-2D in the circuit of relay ZWTK to prevent release of relay ZWTK on picking up of the contact of the delivery relay. When relay iLG picks up, its contact I22 interrupts the circuit of relay 2-4LP so even though front contact 36 of relay ZWTK is closed, energy cannot be supplied to the loweriwinding of relay 24LP to move the relay contacts to their right-hand position. Accordingly, during.

the time in which relay ZWTK is picked up because of the circuit provided by contact 9! of relay 4LG, the relay EWTK is ineffective to permit energy to be supplied to relay 24LP and this relay is certain to maintain the established traflic direction.

When relay GLHSR picks up, its contact 95 establishes for the relay a stick circuit including back contact 95 of relay ARHSR, front contact 98 of relay 3TB, and back contact 99 of the field station delivery relay F84D.

When relay lLHSR picks up, its contact I00 interrupts one circuit for supplying energy to the red lamp R of signal ALA and establishes a circuit governed by the code detecting relays 4LCDR and 4LDR for supplying energy to the signal lamp. In the drawings, in order to simplify the, disclosure, the local signal control circuits are shown diagrammatically and it is to be understood that these circuits may be arranged in the usual manner so that signal ILA or ALB, will be cleared depending on the position of the track switch at this point.

In addition, when relay lLI-ISR picks up, its contact 46 interrupts the circuit for supplying steady energy to the code transmitter relay 4LTCTM and it releases to cut off the supply of energy from battery AETB to the track rails and connects relay ALTR across the track rails. When the supply of energy from battery 4ETB to the track rails is cut off, the relay lRTR releases and interrupts the circuit of relay GR'I'FSA and it releases with the result that its contact .60 interrupts the circuit traced above for supplying steady energy to relay ZLTCTM. Accordingly, the contact of relay ZLTCTM releases and interrupts the circuit of the battery 2WTB and connects relay ZLTR across the track rails.

When the supply of energy from battery ZWTB to the track rails is cut off, the relay 2RTR. releases and interrupts the circuit of relay ZTM and it releases and interrupts the circuit of relay ZRTFSA. As a result relay ZRTFSA releases and its contact 45 completes the circuit for supplying coded energy to relay ZRTCTM. This circuit is governed by contact fill which is governed in accordance with the indication displayed by signal ZLA. The control for contact lfil is arranged so that this contact is released when signal ZLA is at stop and so that the contact is picked up when signal 2LA displays its caution or its clear indication. The details of the control of contact Iii! are not essential to an understanding of this invention and are being omitted to simplify this disclosure.

In addition, when relay ZRTFSA releases, its contact is interrupts the previously traced circuit for supplying energy to terminal 9 of the field station unit i2 and indication codes sent from this station to the office would release relay ZWTK if the stick circuit provided by contact Q? of relay iLG did not keep the relay energized as hereinafter explained.

As a result of operation of relay 2RTCTM by coded energy, impulses of energy are supplied from the battery 2ETB to the rails of section 21 and operate relay ZLTR. During the picked-up periods of the contact of relay 2L'IR energy is supplied to a slow release front contact repeater relay ZLTFSA and its contacts are picked up with the result that during the released periods of relay ZLTR energy is supplied over the back contact of the track relay, front contact 1B2 of relay ZLTFSA and back contact I93 of relay ARTFSA to relay 2-4TM and its contacts pick up with the result that energy is supplied over its contact me to relay 2-4BSA. As a result the relay Z- iBSA picks up and its contact Hit establishes the circuit governed by a contact of relay 2-4TM for supplying energy to the primary winding of the decoding transformer and on continued operation of the relay 2-4TM energy is supplied through the decoding transformer and picks up the relay 2 lHR, and also picksup the relay 2--DR if the track relay ZLTR is operated by energy of 180' code frequency.

When relay Z- iI-IR picks up, energy is supplied over its front contact E88 and front contact I09 of relay ZLTSFA to the circuit governed by contact lid of relay 2- lDR for supplying energy to the yellow or the green lamp of signal 2W. In addition, at this time energy is supplied over front contact I98 of relay 2-6HR and back contact Hi of relay QRTFSA to the red lamp R of signal 4E.

After relay 2-4IIR. picks up, energy of 180 code frequency is supplied to relay ARTCTM over the circuit which includes back contact 69 of relay 4RTFSA, a contact of code transmitter EBDCT, front contact 68 of relay 2-41-11? and back contact 69 of relay 4E3.

When relay 2-4HR picks up, energy is supplied over its front contact H 2, back contact H3 of relay tRTFSA, and front contact H4 of relay ZLTFSA to relay 2W8 and its contacts pick up.

As a result of the supply of coded energy to relay SRTCTM this relay causes coded energy to be supplied from battery lWTB to the rails of section 5T. This energy operates relay ALTR and during the picked-up periods of the relay lLTR; energy is supplied to the code following repeater relay dTlVi and it picks up. During the picked-up periods of the relay ATM energy is supplied to the slow release relay ALTFSA and its contacts pick up with the result that during the released periods of relay 4'IM energy is supplied to the slow release back contact repeater relay tLTBSA. When relay 4LTBSA picks up, its contact H4 establishes the circuit of the primary winding of the associated decoding transformer and energy is supplied through this transformer to pick up the code detecting relays :iLCDR and 4LDR with the result that energy is supplied over front contact Hill of relay iLI-ISR, front contact i if; of relay 4LCDR, and front contact H6 of relay 4LDR, to the green lamp G of signal 41- In addition, when relay ALDR picks up, energy is supplied over its front contact H8 to terminal 9 of field station unit 34 and indication codes sent from this station to the office will pick up relay 4ETK.

As previously stated, when steady energy is removed from the right-hand end of the stretch and the relay 2RTFSA at the left-hand end of the stretch releases, it removes energy from terminal $3 of the field station |2 while the starting relay for this field station is operated to prepare the station to transmit an indication code to the ofiice. Similiarly, when coded energy is received at the right-hand end of the stretch and picks up relay 4LDR, it establishes a connection to terminal 9 of the field station 3--4 while the starting relay for this field station is operated to prepare the field station to transmit an indication code to the office.

Since the relay 2RTFSA at the left-hand end of the stretch releases before the relay lLDR at the right-hand end of the stretch picks up, the field station l2 will be prepared to send an indication codetothe office before the station 34 is prepared to do so. However, because of the operating characteristics of C. T. C. systems the stations may not operate to send indication codes to the office in the order in which the stations are prepared to send such codes. Thus under the circumstances outlined above at times station l2 will send an indication code to the oiiice before station 34 does so, and at other times station [-2 will not send an indication code to the ofiice until after station 34 has sent an in dication code to the office. Furthermore, irrespective of the order in which the two stations operate to transmit indication codes to the ofiice, a considerable time interval may elapse between the time of transmission of codes from the two stations.

The indication code sent from station l--2 to the office after release of relay ZRTFSA would release relay ZWTK if. energy were not supplied to this relay by the stick circuit established by front contact 91 of relay llLG. If relay 2WTK is released by an indication code sent from station I2 before relay 4ETK is picked up by an indication code sent from station 34, contact 21,

of relay ZWTK will establish the circuit of the lamp 24BKE before this circuit is interrupted by contact I28 of relay 4ETK. If this should occur, the lamp 2-4BKE would be lighted to indicate occupancy of the stretch even though the stretch is not occupied. This lamp would be extinguished when an indication code is received from station 34 to pick up relay 4ETK but the lamp might be lighted. for a substantial period before this code is received. This premature lighting of the block indication lamp would be confusing to operators and this system operates to prevent this improper lighting of this lamp, but at the same time insures that it will always be lighted when it should be lighted.

lease upon picking up of delivery relay OIZD at the end of the indication code received from station l--2. Instead it is maintained picked I up by the stick circuit which includes back contact of relay 3TK, back contact 2| of relay AETK, front contact 22 of relay ZWTK, front contact 91 of relay 4LG, winding of relay ZWTK,

back contact of relay lEFK, and normal polar contact 26 of relay 2-4LP. Accordingly, contact 21 of relay ZWTK continues to interrupt the circuit of the lamp 2-4BKE and this lamp rea mains dark. 7 V

When an indication code is subsequently received from station 3-4 to pick up relay AETK its contact I20 opens the circuit of the lamp 24BKE so that on subsequent release of relay 'ZWTK and closing of its back contact 2? in the 'circuit of this lamp the lamp is not lighted.

When relay BETK picks up, its contact 2! interrupts the previously traced stick circuit for relay ZWTK and its contacts release so that its back contact 21 in the circuit of lamp 24BKE is closed.

When a train governed by signal GLA or ALC enters the stretch, the relay lLTR ceases to op- ,erate and relay tLDR releases and its contact l8 interrupts the supply of energy to terminal 9 of relay ZWTK remains released and its contact 2? maintains the circuit of the lamp 2-4BKE.

If a westbound train enters the stretch promptly after one of the signals 4L has been cleared,

it may cause release of relay iLDR, with consequent interruption of the supply of energy to ter minal 9'of the field station 34, before this sta- ,tion has had an opportunity to transmit an indication code to the ofiice to pick up the relay AETK.

. Because of release of relay ALDR and consequent interruption of the supply of energy to terminal 9 of the field station unit, indication codes subsequently transmitted from this station to the ofiice will not pick up relay GETK. However, when the train passes through the detector section 3T, the track relay 3TB, is released and its contact l2! establishes a circuit to supply energy to terminal ll] of field station '3-4 so that indication codes sent from this station pick up relay As explained in the Lewis patent, the field station units are constructed in such manner that after release of relay 3TB to establish the supply of energy to terminal N3 of the field station unit, this unit causes the next indication code sent to the office to be of such character as to pick up relay 3'I'K even though relay STR picks up before this indication code is transmitted. This insures that On entrance of a train into the stretch an indication code will be sent to the office to pick up relay 3TK even though the train is relatively 12 short and vacates section 3T before an indication code is sent to the ofiice. v

After section ST is vacated and relay 3TB. is picked up, an indication code will be sent to the ofilce to release relay 3TK, but this indication code will not be sent until a code has been sent to pick up relay 3TK. On release of relay 3TK its contact in the circuit of relay 2-4LP is closed,

but at this time the circuit of the lower winding of this relay is interrupted by contact 36 of relay ZWTK so energy cannot be supplied to relay Z4LP to move its contacts to their reverse posi 7 tion.

When the indication code is received at the ofiice to pick up relay 3TK, its contact 2 0 interrupts the stick circuit for relay ZWTK and it releases so that its contact 2'! in the circuit of the lamp 2-4BKE is closed. At this time relay lETK is in its released position so its back contact in the circuit of the lamp'24BKE is closed and the lamp is lighted to show that the stretc is occupied.

In addition, when relay 3TK picks up, its contact 99 interrupts the stick circuit for relay 4LG and it releases with the result that its contact I22 in the operating circuits for relay 2--4LP is closed, but at this time these circuits are interrupted by contact I24 of relay 3TK so the relay 24LP cannot be operated.

When a train enters the stretch, contact 98 of relay 3TB interrupts the stick circuit for relay GLHSR and it releases to prevent reclearin'g'oi the signal ALA or 4LB unless another control code is sent to pick up this relay. In addition, when relay lLI-ISR releases, its back contact 36 in the circuit of relay ALTCIM is closed and when section 3T is vacated so that front contact 48 of relay 3TB is closed, steady energy is supplied to relay 4LTCTM and its contact picks up to cause steady energy to be supplied from the battery AETB to the track rails. As the train proceeds through the stretch the steady energy supplied behind the train follows the train and when the stretch is vacated this energy picks up track relay ZRTR to pick up relays 2TM and 2R'IFSA, causing relay 2R'I'FSA to close its front contact 18 in the circuit leading to terminal 9 of field station l 2. When relay ZRTFSA picks up, the starting relay for field station |2 is operated to cause this field station to transmit an indication code to the ofiice which will pick up relay ZWTK.

Accordingly, when delivery relay Ol-2D picks up at the end of the indication code and connects relay ZWIK to terminal 9 of the ofiice coding unit energy is supplied to relay ZWTK and its contacts pickup so that front contact 22 of relay ZWTK is closed and on release of relay 0 l-2D the stick circuit for relay ZW'IK is completed and the contacts of the relay ZWTK are thereafter maintained picked up by energy supplied over the relay stick circuit.

When relay ZW'IK picks up, its contact 21 interrupts the circuit of the lamp 2-4BKE and this lamp is. extinguished to show that the stretch is no longer occupied. In addition, when relay ZWTK picks up, its front contact 36 in the circuit of the lower winding of relay 2-4LP is closed and on movement of the trafiic lever 2-4TFK energy may be supplied to the lower winding of relay 24LP to move its contacts to their right-hand or reverse position if it is desired to prepare the stretch for eastbound traflic. The equipment is now substantially in the condition in which it is shown in the drawings.

for supplying coded energy thereto.

first released period of relay 2LTCTM energy asse ses If it is desired to change the wayside apparatus to prepare the stretch for eastbound traffic, the traffic lever 2-4TFK is moved to its righthand position in which its contact I establishes the circuit of the lower winding of relay 2--4LP, assuming that this circuit is otherwise complete, and the contacts of relay 2--4LP move to their right-hand position. On this movement of the contacts of relay 24LP contact 26 interrupts the stick circuit for relay 2WTK and its contacts release, while contact 28 of relay 2--4LP interrupts the circuit of relay ZWFK and its contacts release with the result that contact 32 interrupts the circuit of the lamp 2BKE. and prevents lighting of this lamp upon closing of back contact 21 of relay 2WTK. In addition, on release of relay ZWFK its back contact is closed so that as long as relays IETK and ZWTK are released energy may be I supplied to either of the windings of the relay 2--4LP. This enables the operator to restore the contacts of the relay 24LP to their lefthand position to designate westbound ,traflic, if the operator wishes to condition the stretch for westbound trafiic before the wayside equipment completes the change to eastbound trafiic.

The traffic lever 24TFK is of the push-turn type and during movement of the lever the contacts I26 and I2! establish pick-up circuits for the starting relays 34ST and I2 ST and thus cause control codes to be transmitted to stations I-2 and 3--4. As contact 38 of relay 24LP is in its right-hand or reverse position, energy is not supplied to terminal I during transmission of the control code to station I2 and the code sent to this station releases relay ZWFSR so that its contact I9 in the circuit leading to terminal 9 oi the field station is open and so that contact 4 of relay ZWFSR establishes the circuit including back contact I29 of relay ZRI-ISR for supplying steady energy to relay 2RTCTM. Accordingly, relay 2RTCTM picks up and connects battery 2ETB across the track rails, but energy supplied from battery ZETB does not pick up the relay ZLTR since relay 2LTCTM is picked up and connects battery ZWTB across the rails through the relay ZLTR. As relay 2LTR remains released the relay ZLTFSA also remains released.

As contact 38 of relay 2-4LP is in its righthand position, energy is supplied to terminal 4 of the office coding unit during transmission of the control code to station 3--4 so this control code picks up relay AEFSR. Accordingly, contact A l of relay 4EFSR interrupts the circuit for supplying steady energy to relay 4LTCTM and connects this relay to the circuit governed by back contact I30 of relay 4LTFSA for supplying coded energy to relay dLTC'IM with the result that it now supplies coded energy from battery AETB to the rails of section 4T. This coded energy causes code following operation of relay 4RTR with the result that relay 2-4TM operates and causes energy to be supplied through the associated decoding transformer to relay 2-4I-IR. When relay 2-4HR picks up, its contact H2 establishes the circuit including back contact H4 of relay 2LTFSA and front contact H3 of relay ARTFSA for supplying energy to relay 4E3 and its contacts pick up so that contact 6! interrupts the circuit for supplying steady energy to relay ZLTCTM and establishes a circuit including, back contact, 73 of relay ZL'IFSA During the from battery 2ETB feeds to. relay ZLTR and picks up its contact to establish the circuit of relay lLTFSA and its contacts pick up so that contact 13 interrupts the supply of coded energy to relay 2LTC'IM and its contacts remain released and maintain relay ZLTR, connected across the track rails.

In addition, when relay ZLTFSA picks up; its contact an interrupts the operating circuit for relay 25TM and it remains released with the result that energy ceases to be supplied through the decoding transformer to relay 2-41-18; and it releases to interrupt the supply of energy to relay AES and it releases to close its back contact 69 in the operating circuit of relay :IRTCTM. After release of relay 4E8 steady energy is supplied to relay 4R'ITCI?M over the circuit which includes front contact I3 of relay 2LTFSA, back contact I6 of relay 2W8, back contact 68 of relay 2-4HR, and back contact 59 of relay HES. This energy picks up contact 50 of relay iRTCTM to connect battery 4WTB across the rails of section 4T through the winding of relay fiRTR. After relay IRTCTM picks up, the relay lRTPt remains released and relay GRTFSA releases. After battery 4W'IB is connected across the rails of section 4T, energy from the battery feeds to relay IL'I'R. during the first released period of the contacts of relay ALTCTM. This energy picks up the contact of relay ALTR to establish the circuit of relay HM and it picks up to establish the circuit of relay ALTFSA, with the result that contact I30 of relay AL'I'SF'A interrupts the circuit of relay 4LTCTM and it remains released and maintains the circuit of relay 4LTR.

In addition, after relay 4L'IFSA picks up, energy is supplied over back contact II-8 of, relay ILDR, back contact I3I of relay ILCDR, front contact I32 of relay ALTFSA, and front contact I33 of relay 4EF SR to terminal 9 of the-field station 3-4- and the indication codes sent from this station pick up relay 4ETK at the office.

At the other end of the stretch the circuits for supplying energy to terminal 9 of station I-2 are interrupted and the indication codes sent from this station do not pick up relay ZWTK at the office and it therefore remains released.

When relay AETK at the oince picks up, its contact I34 establishes the relay stick circuit which includes back contact [36 of relay ZW'IK and back contact I31 of relay I TK.

In addition, when relay lETK picks up, energy is supplied to relay IEFK over the circuit which includes reverse polar contact 28 of relay 2-4LP, front contact I38 of relay lIETK and back contact I39 of relay ZWFK. This energy picks up the contacts of relay EFK and its front contact I40 establishes a stick circuit to keep the relay contacts picked up during subsequent release of relay AETK.

When relay AEFK picks up, its contact MI in the circuit of lamp 2-4BKE" is closed, but at this time this circuit is interrupted by contact I20 of relay IETK so the lamp is not lighted.

In addition, when relay 4EFK picks up, its contact I42 in the circuits of relay 2-4LP i open with the result that energy is no longer supplied over back contact 36 of relay ZWTK to the lower winding of relay 2--lLP but because 01 the operating characteristics of relay 2-4LP the relay contacts. remain in their right-hand position. As long as relay 4ETK is picked up, its front contact I44 establishes a circuit over which energy may be supplied to the upper winding of relay 2-4LP ion: movement of lever 24TFK to its left-hand "position.

' When relay 4EF'K is picked up, its contact M3 in'the pick up circuit for relay 2RG is closed so that on movement of signal lever ZSIG to its right-hand position, and the transmission of a leading to terminal 4 of the office coding unit.

Accordingly, the control code transmitted at this time picks up relay ZRHSR. to remove the steady energy from the left-hand end of the track stretch and to establish a circuit to cause signal only one form of railway traific controlling ap- ZRA or ZRB to clear when coded energy is received over the single track stretch. Also when relay ZRG picks up, itscontact Ml establishes a stick circuit for relay GETK to keep its contacts picked up until an indication code is received to pick up relay ZWTK or lTK. As relay EE IK re- "mains picked up its contact I interrupts the circuit of the lamp 24BKE and prevents lighting of this lamp until relay ZWTK picks up to interrupt the lamp circuit, or until relay IIK picks up to show that a train has entered the stretch.

' When ma ZRG picks up, its Contact 14a insures that these control codes will maintain relay 4EFSR picked up.

When eastbound signal 2RA is cleared, the wayside apparatus operates in substantially the same manner as upon clearing of the westbound signal 4LA and a detailed description of the operation of the apparatus is unnecessary.

From the foregoing it will be seen that the improved circuits provided by this invention insure that when a signal is cleared the block indication lamp will not be improperly lighted because of delays in the operation of the equipment in transferring control of this lamp from the exit to the entrance end of the stretch.

In addition, it will be seen that these circuits are arranged so that when control of the block indication lamp is transferred from the exit to the entrance end of the stretch, the indication relay at the ofiice which is governed from the exit end of the stretch surrenders its control of this lamp as soon as the indication relay at the ofiice which is governed from the entrance end of the stretch shows that it is prepared to assume con- I trol of the lamp.

These circuits are also arranged so that if a train enters the stretch before an indication code has been sent to the oihce to cause the control of the'indication lamp to be transferred to the in- 1 dication relay at the entrance end of the stretch,

the indication code sent in response to entrance of the train into the stretch will cause the control of this lamp to be transferred to the indica- -tion relay which is governed from the entrance end of the stretch.-

The block indication relays are employed in the control of the trafiic direction designating relay 2-4LP. but the improved circuits of this invention which delay release of the block indication relays cannot result in improper supply of energy to relay 2 -4LP because the relays which delay 'release of the block indication relays also interrupt the circuit of the relay 2'4LP.

Although we have herein shown and described paratus embodying our 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 our invention.

Having thus described our invention, what we claim is;

1. In a centralized trafiic control system for a stretch of single track railroad equipped with a communication system for transmitting control codes from a control office to stations at the ends of the stretch and for transmitting indication codes from the stations to the ofiice, said stretch being equipped with a reversible track circuit system which when energized reflects trafiic conditions in said stretch, a first and a second indication relay at the ofiice controlled by said track circuit system by indication codes transmitted from one end andfromthe other end, respectively, in accordance with its direction of energization to indicate the condition of occupancy of the stretch, said track circuit system being normally energized in the direction to control said first indication relay and arranged to have its direction of energization reversed when a control code is issued for authorizing a train to enter the stretch at the end from which said second indication relay is controlled, said system also including a block indication lamp at the ohice which when lighted indicates the occupancy of said stretch, havin an energizing circuit which includes contacts of said indication relays in series arranged so that the circuitis closed only when both relays assume their block occupied positions, the combination with the foregoing apparatus of means for preventing the temporary closing of said lamp circuit during the reversal of the direction of energization of said track circuit system, comprising a signal clearing relay at the oifice which is operated when said control code for authorizing a train to enter the stretch is issued and which releases when such authorization is cancelled, means controlled by said signal clearing relay and effective as long as such relay isin its operated position to suspend the code control of said first indication relay from its block clear to its block occupied position, and means controlled by said second indication relay for restoring the first indication relay to its block occupied position when said second indication relay is operated to its block clear position.

2. In. a centralized trafiic control system as claimed in claim 1, a track indication relay at the oihce governed by indication codes reflecting the condition of occupancy of a detector track section at the end of the stretch from which said second indication relay is controlled, and means controlled by said track indication relay for restoring said first indication relay to its block occupied position in the event the occupancy of said detector section is indicated but the second .indication relay is not operated.

3. In a centralized traffic control system as claimed in claim 2, means for restoring said signal clearin relay to its normal position automatically by said track indication relay when an indication code indicating the occupancy of said detector track section is received, and other means for restoring said signal clearing relay to its normal position effective when a code is re- 12? ceived which indicates that the authorization for a train to enter the stretch has been manually cancelled.

4. In a centralized traffic control system as claimed in claim 1, the combination in which said first and second indication relays are neutral stick relays arranged to be picked up and released by indication codes which reflect the energized and deenergized condition, respectively, of said track circuit system, and in which the circuit for said block indicator lamp includes back contacts of both indication relays in series and the first indication relay has a stick circuit for holding such relay in its block clear position which includes a back contact of the second indication relay and also includes a normally closed code controlled contact bridged by a normally open contact of said signal clearing relay.

5. In a centralized trafiic control system as claimed in claim 4, a track indication relay at the office governed by indication codes reflecting the condition of occupancy of a detector track section at the end of the stretch from which said second indication relay is controlled, and means comprising a contact of said track indication relay included in the stick circuit for said first indication relay for opening said stick circuit when a code is received which indicates the occupancy of said detector track section.

18 6. In a centralized traflic control system as claimed in claim 5, the combination in which said signal clearing relay is arranged to be picked up in response to the transmission of a control code for authorizing a train to enter the stretch at the end from which said second indication relay is controlled, and is arranged to be released automatically by said track indication relay in response to a code indicating the occupancy of said detector track section, and is also arranged to be released in response to an indication code which follows the transmission of a control code for cancelling the authorization for a train to enter the stretch.

FRANK T. PASCOE.

ARTHUR L. JEROME.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,344,333 Van Horn Mar. 14, 1944 2,395,706 Young Feb. 26, 1946 2,422,127 Pascoe et a1 June 10, 1947 2,424,038 Jerome July 15, 1947

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