US2305984A - Railway traffic controlling apparatus - Google Patents

Description

Dec. 22, W42. F. H. NICHOLSON RAILWAY TRAFFIC CONTROLLING APPARATUS '2 Sheets-Sheet 1 Filed NOV. 29, 1940 I I NVENTOR Fmnl: AKA/2021023012 Q W HIS ATTORNEY Dec. 22, 1942. .F. H, NICHOL$ON RAiLWAY TRAFFIC CONTROLLING APPARATUS Filed Nov. 29, 1940 2 Sheets-Sheet 2 I L MS ATTORNEY Patented Dec. 22, 1942 RAILWAY TRAFFIC CONTROLLING APPARATUS Frank H. Nicholson, Penn Township, Allegheny County, Pa... assignor to The Union Switch & Signal Company, Swissvale, Pa., a corporation of Pennsylvania Application November 29, 1940, Serial No. 367,972

11 Claims. (Cl. 246-38) My invention relates to railway traflic controlling apparatus and it has special reference to the organization of such apparatus into systems of the class wherein traflic governing signals are controlled by energy that is distinctively coded in accordance with advance trafiic or other conditions and that is transmitted to the signal locations over circuit of either the track or the line type.

One object of my invention is to provide a novel and improved form of such organization.

Another object is to enable pulses of coded energy that recur at only one rate to select among a plurality of different signal indications.

A further object is to extend the number of signal indications which systems of the frequency code type are capable of providing.

A still further object is to provide code distinguishing apparatus which is immune to false responses and which incorporates other features of inherent safety.

In practicing my invention I attain the above and other objects and advantages: (1) utiliz ing control circuit energy that is of given polarity at times and of opposite polarity at other times; (2) coding or modulating the energy of each of the polarities so used at one or more'rates of supply circuit interruption; and (3) providing novel signal governing apparatus that responds distinctively to each different polarity and pulse rate combination of the so coded energy which the control circuit transmits.

I shall describe three forms of railway traflic controlling apparatus embodying my invention,

and shall then point out the novel features thereof in claims. These illustrative embodiments are disclosed in the accompanying drawings in which:

Fig. 1 is a diagrammatic representation of a track type of control circuit equipped with the improved apparatus of my invention and organized to form part 01" a three-indication sys tem. of automatic block signaling;

Fig. 2 illustrates a line type of control circuit which is equipped with improved apparatus closely resembling that shown in Fig. 1; and

Fig. 3 represents a second track circuit which incorporates the improvements of my invention but which is organized for use in a five-indication system of automatic block signaling.

In the several views of the drawings like reference characters designate corresponding parts. Referring first to Fig. 1, characters I and 2 designate the conductors of a control circuit-which normally is capable of transmitting energy between its two ends but which at-times is rendered incapable of such transmission. As shown in Fig. 1, these control circuit conductors take the form of the two rails of a section of railway track I-II which is separated from adjoining sections by the customary .insulated joints 3 and through which it will be assumed that trafilc moves in the single direction indicated by the arrow. Such movement, of course, makes location I the section entrance end and. location II the section exit end.

Single-rate code combination of Fig. 1

- contact 5 transmits to the rails.

At the section entrance end I there likewise is provided a polar relay TRP which has its winding connected across the rails and which in accordance with the polarity of the windingreceived pulses of coded energy biases contacts 89--|0 to the right or to the left; a code following track relay TR which requires direct current of a given polarity for operation and which also is connected with the section rails but over contacts 8 and 9 and in such manner that all received trackway energy impressed thereon has the required given polarity; a decoding transformer DT which receives primary current under the control of a pole changing contact ll of the track relay; a code detecting relay H which is of the direct current delayed release type (duplicating the advance section device of similar identification shown at location Ii) and which is energized from the decoding transformer secondary over a rectifying contact I2 of the.

trackrelay; and a wayside signal S which governs the entry of traflic into section 1-H and which is controlled to three indications by a contact 13 of relay H aided by contact [0 of relay TRP- The exit end or location II apparatus just described for the track section of Fig. 1 operates in the following manner. With advance section relay H picked up as represented, each pick-up of coding contact 5 produces an on period pulse in a given polarity signal control code. During the continuance of each of these pulses source TB maintains rail l positive with respect to rail 2. This is done over a connection (completed by device CT) extending from the positive terminal of source TB, through front contact 6 of device H, conductor 15, front contact 5 of device CT, conductor K6, the track rails l and 2, a current limiting impedance H, conductor [8 and front contact I of device H back to the negative terminal of source TB.

Upon each release of coding contact 5 there is produced (by an interruption in the circuit just traced) an 01% period interval in the given polarity signal control code and there is also set up a potential dissipating connection between the section rails and impedance 11. This latter connection extends from rail I through conductor it, back contact 5 of device CT, and impedance ll back to rail 2. It functions to discharge the rail storage potential before contact 5 againpicks up to produce a succeeding on code period.

When, however, the exit end conditions of Fig. 1 change in such manner that relay H becomes released, each pick-up of coding contact 5 then produces an on period pulse in an opposite polarity signal control code. During the continuance of each of these pulses source TB maintains rail 2 positive with respect to rail-I. This is done over a connection (completed by device CT) extending from the positive terminal of source TB, through back contact 6 of devicev H, conductor l8, impedance H, the track rails 2 and I, conductor l6, front contact 5 of device CT, conductor i5 and back contact I of device lT-I back to the negative terminal of source TB.

As under the given polarity code supply conditions first described, each release of coding contact 5 now: (1) produces an off period interval in this opposite polarity code; and (2) connects the rails in energy dissipating relation with impedance H. p

The entrance end or location I apparatus earlier described for the Fig. 1 track section operates in a manner which will next be explained. When recurring pulses of the given polarity" code energy are being transmitted over the section rails to that apparatus, the polar relay TRP thereof responds to those pulses by holding contacts 8-43-40 continuously to the right. This positioning causes the code following track relay TR to have the potential of each of those given polarity pulses directly impressed thereon over a circuit extending from the now positive rail I through conductors 20 and M, right contact 8 of device TRP, conductor 22, the winding of relay TR, conductor 23, right contact 9, and conductors 24 and 25 back to the now negative rail 2.

Thus directly excited by this given polarity code energy, track relay TR picks up and releases its contacts H and I2 in step with the recurring on period pulses thereof. As a result, those contacts I! and I2 now cause decoding transformer DT to supply (from a local control source designated by terminals plus and minus) the code detecting relay H with code step pulses of energizing current which hold the detecting relay contacts continuously picked up. In consequence, signal SI now displays the clear indication as a result of lamp G thereof being supplied with lighting current over a circuit that extends from a positive supply terminal through front contact I3 of relay H, conductor 21, right contact I 0 of relay TRP, conductor 28 and the lamp G back to a negative supply terminal.

When, however, recurring pulses of opposite polarity code energy are being received at location I, polar relay TRP responds by shifting (and again continuously holding) contacts 8-9-l0 to the left. As a result of this shifted positioning, the track relay 'I'R now has the potential of each of those opposite polarity pulses reversely impressed thereon (in the required relay operating direction wherein the right terminal of the relay winding is positive) by way of a circuit that extends from the now positive rail 2 through conductors 25 and 24, left contact 9 of device TRP, conductor 22, the winding of relay TR, conductor 23, left contact 8 of device TRP, and conductors 2| and 25 back to the nownegative rail l.

Thus reversely energized by this opposite polarity code energy, track relay TR causes its contacts 'I I and 12 to pick up and release in step with the recurring on period pulses of that energy and thereby again effects (through the decoding transformer DT) the pick-up of code detecting relay H. In consequence, signal SI now shows approach as a result of lamp Y thereof being supplied with lighting current over front contact l3 of relay -H, conductor 21, left contact H] of relay TRP, and a conductor 29.

Finally, when reception of all trackway energy at entrance end locationI becomes discontinued, polar relay TRP retains its contacts 8-9-40 in the position to which they were last biased; track relay TR is continuously deenergized and hence inactive; code detecting relay H also is deenergized and hence released; and signal SI now displays the stop indication as a result of lamp R. thereof receiving lighting current over back contact l3 of device H and conductor 30.

From the foregoing description of the coded track circuit apparatus of Fig. 1, it will be apparent that by equipping each of a plurality of consecutive track sections with this Fig. 1 apparatus (and arranging that the entrance and relay H of each section determine,by means of contacts 6 and I as shown at location II,-the polarity of the pulsed trackway energy' that is supplied to the exit end of the rear adjoining section) there may be provided a three-indication automatic block signaling system of novel and improved character. Such a three-indication system will operate in the following manner.

As long as the signaled stretch of track remains vacant, the rails of each section therein transmit recurring pulses of given polarity code energy to their entrance ends; the polar relay TRP for each section reacts to that energy by holding its contacts in the position shown in Fig. 1; the track relay TR for each section follows the coding of that received energy; the code detecting relay H (entrance end) for each section is thereby held picked up; and the guarding signal S for each section is kept (by relays H and TRP) at clear.

In the event that a train now passes through the signaled stretch, the rail-shunting action of its wheels and axles produces the following effects at the entrance end of each of the sections occupied: (1) deenergization of track relay TR; (2) release of the code detecting relay H; (3) placement at stop of the section-guarding signal S; and (4) supply of opposite polarity code energy to the section immediately to the rear.

At theentrance end of that first rear section the pulses of that opposite polarity energy: (1) shift the contacts of relay TRP away from the position shown in Fig. 1; (2) operate relay TR in code following manner; (3) cause relay H to pick up; (4) put the signal S for that first rear section at approach; and (5) given polarity code energy to be supplied to the next section to the rear.

At the entrance end of that next or second rear section the pulses of that given polarity energy: (1) shift the contacts of relay TRP back to the position shown in Fig. l; (2) operate relay TR; (3) hold relay H picked up; (4) put the signal S for that second rear section at clear; and (5) cause given polarity code energy to be repeated into the rails of the succeeding section to the rear.

In this way each train passing through the signaled (as per Fig. 1) stretch of track sets up its own following protection in customary three indication automatic block manner.

Line circuit application of Fig. 2

The improved facilities of my invention are not restricted to control circuits of the just described track type but they also have utility when applied to circuits of any other form wherein the conductors lose their normal energy transmitting capability under certain conditions only. One such other form of circuit is shown in Fig. 2.

There the circuit conductors have been represented as line wires Ia and 2a. These line wires are analogous to the rails of the Fig. 1 tracksection in that they connect coded energy supply equipment TB-CT.H at the sending (righthand) end of the circuit with code distinguishing equipment TRPTR-I-I at the receiving (left-hand) end of the circuit.

As shown in Fig. 2 these line circuit sending and receiving equipments exactly duplicate the corresponding track circuit equipments of Fig. 1 and hence detailed description thereof need not be repeated here. Of the Fig. 2 combination it will instead sufiice to say that: (1) device CTs coding contact 5 causes source TB to supply the line wires la. and 2a with coded energy in the form of recurring on period pulses that are separated by off period intervals; (2) these pulses have given polarity when contacts t-'! of relay H are picked up and opposite polarity when contacts Ei'l are released; (3) line wires la and 2a normally transmit all pulses of each polarity to polar and code following relays TRP and TR; l) relay TRP holds contacts 8-Qlil to the right in response to received pulses of given polarity energy and to the left in response to received pulses of opposite polarity energy; (5) relay TR is'so connected with the line wires over contacts 3@ that the potential of all energy pulses reaching the relay has the given polarity required to operate contacts I 1-42 in code following manner; and (6) decoding relay H responds to that operation by staying picked up during and only during the continuance thereof.

Any desired use of the line circuit combination of Fig. 2 may, of course, be made. In the particular organization which that figure represents, the receiving end relay H releases its contact i3 only when the normal transmission of coded energy over the line circuit lat-2a becomes discontinued by a release of contacts 2% and 3| that are included in the circuit in the serial manner shown.

cause These line wire contacts 26 and 3| may, quite obviously, be arranged to release in response to any condition which it is desired that relay H register. In the combination represented, they are carried by a relay XR which normally is held picked up by steady energy received from a source XB over the rails of a track section III with which the line circuit la-Za is shown as being co-extensive and through which trafiic moves in the single direction indicated by the arrow. I

As long as this Fig. 2 track section remains vacant, source XB holds relay 2m picked up, coded energy from devices TB--CT flows over the line circuit and operates code following relay TR, and relay H is thereby caused to hold contact I3 picked up. When, however, a train comes into the section and releases relay XR, contacts 26 and 3! introduce breaks in the line wires lat-2a, energy transmission to devices TRP and TR stops, and relay H releases contact l3.

By including this contact, along with a contact ll] of relay TRP, in the lamp selecting circuits" of an entrance end signal SI for the track section, there maybe provided a traffic responsive combination which performs all of the functions of the one disclosed in Fig. 1 and which thus is suitable for use in a three-indication system of automatic block signaling. Such a system may, quite obviously, be set up by equipping each of a plurality of consecutive track sections with this Fig. 2 line circuit combination and by arranging that the receiving end relay H of each determine the polarity of the pulsed trackway energy that is supplied to the sending end of the line circuit which adjoins to the rear.

Such a three-indication system 'willQoperate as follows. Under vacant conditions 'ofthe sig nale-d stretch, each line circuit la'2a'transmits iven polarity code energy to the entrance end of the associated track section; the polar relay TRP at each of those entrance ends is'by that energy caused to hold its contacts in the position of Fig. 2; each associated relay TR follows the coding of that received energy; the relay H at each section entrance end is thereby held picked up; and the guarding signal S for every track section in the stretch is accordingly kept at clear.

Passage of a train through the signaled stretch now produces the following actions at the entrance end of each of the sections occupied: (1) release of contacts 26 and 3| of relay KB; (2) deenergization of code following relay TR; (3) release of code detecting relay H; (4) placement at stop of the section guarding signal S; and (5) supply of opposite polarity code to the line circuit for the sectionimmediately to the rear.

At the entrance end of that first rear section the pulses of that opposite polarity energy; (1) shift the contacts of relay TRP away from the position shown in Fig. 2; (2) operate relay TR in code following manner; (3) cause relay H to pick up; (4) put the signal S for that first rear section at approach; and'(5) cause given polarity code energy to be supplied to the line circuit for the next section to the'rear.

At the entrance end of that next or second rear section the pulses of that given polarity energy: (1) shift the contacts of relay TRP back to the position shown in Fig. 2; (2) operate relay TR; (3) hold relay H picked up; (4) put the signal S for that second rear section at clear;

' and (5) cause given polarity code energy to be repeated into the line circuit for the succeeding section to the rear.

In this way each train passing through the signaled (as per Fig. 2) stretch of track sets up its own following protection in customary three indication automatic block manner.

MuZti-rate code combination of Fig. 3

The indication-extending facilities of my invention are not restricted to control circuits of the elementary single-rate code type just described but they also have utility when applied to control circuits wherein a plurality of distinctively differing rates of code pulse recurrence are selectively employed. One such multi-rate code circuit is shown in Fig.3.

As in Fig. l, the conductors i and 2 of this Fig. 3 control circuit take the form of the two rails of a section of track III through which it will be assumed that traffic moves in the single direction indicated by the arrow. As in Fig. 1, also, the track circuit of Fig. 3 is provided: (1) at its exit end II with a source of direct current energy TB, a coding contact 5 which connects source TB with the section rails in recurring code pulse manner, and apparatus (including contacts 6 and 1) which at times reverses the polarity of the pulsed energy which coding contact 5 transmits to the rails; and (2) at its entrance end I with a polar relay TRP which distinguishes the polarity of the there received pulses of coded energy, a code following track relay TR of the given-polarity responsive type which is connected with the rails over contacts 8 and 9'of device TRP, a decoding transformer DT which receives primary current under the control of a pole-changing contact H of the track relay, and a home decoding relay H which is energized from the decoding transformer secondary over a rectifying contact H. of the track relay.

This multi-code rate track circuit of Fig. 3 differs from the single-rate circuit of Fig. 1 by utilizing certain further apparatus at each of its two ends. vThus, at the exit end II of the Fig. 3 circuit: (1) the polarity reversing contacts 6'l of the advance section relay H are aided by contacts 323334-35 of advance section relay TRP and by contacts 38-3l33--39 of a distant decoding relay D for the advance section; (2) the coding or energy interrupting contact 5 is carried not by a single speed coder CT but instead by a relay CR. which repeats the action either of a high speed code transmitter CTNQ or of a low speed code transmitter CTI5; and (3) selection between these high and low speed code rates is made by a contact Ml of advance section relay D aided by contacts 4!--1t2 of advance section relay H and contacts 43-M of advance section relay 'IRP.

Likewise, at the entrance end I of the Fig. 3 circuit: (1) the home decoding relay H is supplemented by a distant decoding relay D; (2) this distant relay H is energized through a frequency selective unit IGDDU which allows pick-up current (from transformer DT) to reach the relay only when the controlling track relay TB is following code at the high speed rate; and (3) the section guarding wayside signal takes the form of a device S which is controlled to five indications by contact !-3 of relay H, a contact 46 of relay D, and contacts it and 41 of relay TRP.

The just described exit end facilities of Fig. 3 selectively supply the rails of section III with off" period intervals. 1) when the advance section relays D and H trackway energy of one or another of four different signal control codes. These four codes are made up of distinctive combinations of: (1) pulse rate; and (2) energy polarity.

The pulse rate is, of course, determined by the speed at which coding contact 5 of the repeater device CR recurrently picks up and releases. Under certain conditions, contacts d-B-it of advance section relays D-H-TRP assign the driving circuit of that repeater device to a contact it!) of the high speed code transmitter C'Ilfiii and thereby cause the coding contact 5 to operate at a rate assumed to be 180 times per minute. Under other conditions, however, the relay contacts 46-44 transfer the repeater driving circuit to a contact 15 of the low speed transmitter C'Il5 and then cause the coding contact 5 to operate at a slower rate assumed to be times per minute.

The energy polarity, similarly, is determined by the way in which source TB is connected with the section rails each time that coding contact 5 is picked up. Under certain conditions, contacts L -l and 32-413 of advance section relays IITRP-D so set up this connection that current from source TB flows into the rails in the given polarity direction which makes rail I positive with respect to rail 2. Under other conditions, however, the relay contacts above designated reverse the just named connection and then cause current from source TB to flow into the rails in the opposite polarity" direction which makes rail 2 positive with respect to rail I.

For producing the four distinctive signal control codes earlier referred to use is made of the pulse rate and energy polarity combinations which the following code names designate: (1) 180 positive; (2) 75 positive; (3) 180 negative; and (4:) 75 negative.

The first or 180 positive code consists of on period pulses of given polarity energy that are impressed (over the front point of contact 5) upon the section rails at the rate of 180 per minute and that are separated by the usual This code is supplied:

are both picked up at a time when the contacts of advance section relay TRP have the position shown in Fig. 3; or (2) when the advance section relay D is released at a time when the companion relays H and TRP have the condition shown in Fig. 3.

Each energy pulse of this 180 positive code reaches the rails over a circuit that extends: (l)

.. in the first stated instance from the positive terminal of source TB (see location II of Fig. 3) through conductor 49, front contact 36 of relay D, conductors it and !5, front contact 5 of device CR, conductor E6, the rails i and 2, impedance I1, conductors l8 and 5!, front contact 3? of relay D, and conductor 52 back to the nega tive terminal of source TB; and (2) in the second stated instance from the positive terminal or source TB through conductor 49, front contact 63 of relay H, conductor 53, right contact 33 of relay TR-P, conductor 54, back contact 36 of relay D, conductors iii) and I5, front contact 5 of device CR, conductor It, the rails l and 2, impedance ll, conductors i8 and 5|, back contact 31 of relay D, right contact 32 of relay 'I'RP, conductor 55, front contact l of relay H and conductor 52 back to the negative terminal of source TB.

During the supply of this 180 positive code, the repeater relay CR. receives pulsed operating current over contact I of the high speed transacu e initter CTl8fl.- in the instance first named above (relays D and H picked up and relay TRP as shown in Fig. 3) the repeater driving circuit extends from a positive supply terminal, through front contact I60 of device CTl8 0, conductorv 56, right contact 44 of device TRP, conductor 51, front contact 4| of device H, conductor 58, front contact 40 of device D, conductor, 59, and the winding of relay CR, back to a negative supply terminal. In the instance second named above (relay D released, relay H picked up, and relay TRP as shown in Fig. 3) the repeater driving circuit extends from code transmitter contact I 86 through conductor 66, front contact 42 of device H, conductor 6|, back contact 40 of device D and again through conductor 59 to the winding of relay CR.

The second or 75 positive code consists of recurring on period pulses of given polarity energy that are impressed upon the section rails at the rate of '75 per minute. This code is supplied when advance section relay D is picked up at a time when the contacts of companion relay TRP have positions opposed to those which Fig. 3 shows and when companion relay H is picked up.

Each energy pulse of this second code reaches the rails by way of a circuit that extends from the positive terminal of source T'B, through conductor 49, front contact 33 of device D, conductors B and I5, front contact 5 of device CR, conductor Hi, the rails I and 2, impedance l1, conductors l8 and 5|, front contact 31 of device D, and conductor 52 back to the negative terminal of source TB. During the supply of this second code the repeater relay CR receives pulsed operating current over contact l5 of the low speed transmitter CTI5 and by way of a circuit that extends from the positive supply terminal through the front point of contact 15, conductor 65, left contact 63 of device TRP, conductor 58, front contact 40 of device D, conductor 59 and the winding of relay CR back to the negative supply terminal.

The third or 180 negative code consists of recurring on period pulses of opposite polarity energy that are impressed upon the section rails at the rate of 180 per minute. This code is supplied when advance section relay D is released at a time when companion relay H is picked up and the contacts of relay TRP have positions opposed to those shown in Fig. 3.

Each energy pulse of this third code reaches the rails by way of a circuit that extends from the positive terminal of source TB through conductor 49, left contact 34 of device TRP, conductor 63, back contact 39 of device D, conductor l8, impedance ll, the rails 2 and I, conductor l6, front contact 5 of device CR, conductor [5, back contact 38 of device D, conductor 54, and left contact 35 of device TRP back to the negative terminal of source TB. During the supply of this third code the repeater relay CR receives pulsed pick-up current over contact I85 of the high speed transmitter CT|86 and by way of a circuit that extends from the positive supply terminal through the front point of contact I821, conductor 66, front contact 42 of device H, conductor 6|, back contact 56 of device D, conductor 59 and the winding of relay CR back to the negative supply terminal. f

The fourth or '75 negative code consists of recurring on period pulses of opposite polarity energy that are impressed upon the section rails at the rate of 75 per minute. This code and H are both releasedat' a time when the contacts of relay TRLP are in either of their two 63, back contact 39 of device D, conductor I 6,

is supplied when the advance section relays D impedance H, the rails 2 and I conductor [6, front contact 5 of device CR, conductor I5, back contact 38 of device D, conductor 64, back contact l of device H and conductor 52 back to the negative terminal of source TB. During the supply of this fourth code the repeater relay CR receives pulsed pick-up current-over contact 15 of the low speed transmitter and by way of a circuit that extends from the positive supply terminal through the front point of contact 15, back contact 42 of device H, conductor 6|, back contact 40 of device D, 'conductor59 and the winding of relay CR back to the negative supply terminal.

In the case of each and every one of the four signal control codes that ,have just been described, the off period intervals which separate the applied pulses of trackway energy. result, as has been seen, from the recurring releases of coding contact 5 of the repeater relay CR. During each of these releases, contact 5 connects (as in the embodiment of Fig. 1) the section rails across the impedance H for the purpose of dissipating any storage potential which may exist between the rails after the end of the preceding on code period. The earlier described entrance end apparatus for section III of Fig. 3 operates in a manner which will next be explained. When recurring pulses of the positive code energy are being transmitted over the section rails to entrance location I, the polar relay TRP thereat responds to the given polarity of those pulses by holding all of its contacts continuously to the right, as shown. This positioning causes the code following track relay TR to have the given polarity potential of each of those pulses directly impressed thereon over conductors 23 and El, right contact 8, conductor 22, the winding of relay TR, conductor 23, right contact 9, and conductors 25 and 25.

Relay TR responds to this energization by picking up and releasing its contacts ||i2 at the high speed rate of 180 times per minute; that action excites transformer DT in a way causing it to hold both of the decoding relays H and D continuously picked up; and, in consequence, sig- 'nal SI now displays the fclear indication as a result of unit a. being energized over a circuit that extends from the positive supply terminal through front contact l3 of relay H, conductor 61, front contact 46 of relay D, conductor 21, right contact ll] of relay TRP, conductor 28 and the unit a back to the negative supply terminal.

Whenrecurring pulses of 75 positive code energy are being received at location I, the polar relay TRP thereat keeps its contacts in the position shown in Fig. 3 and thus causes the track relay TR again to have the given polarity'potential of those pulses directly impressed thereon. Responding to that energization relay TR now picks up and releases its contacts Ill2 at the low speed rate of 75 times per minute; that slower action of contacts ||I2 excites transformer DT in a way causing it to hold onlythe code detecting relay H picked up and allows decoding relay D to release; and, in consequence, signal S'I now shows approach restricting as a result of unit I) being energized over front contact l3, conductor 61, back contact 46, conductor 68, right contact 41 and conductor 69.

When recurring pulses of the 180 negative code energy are being received at the section entrance I, the polar relay TR thereat responds to the opposite polarity of those pulses by shifting (and again continuously holding) all of its contacts to the left. This shifted positioning causes the track relay TR to have the opposite polarity potential of each of those pulses reversely impressed thereon over conductors and 24, left contact 9, conductor 22, the winding of relay TR, conductor 23, left contact 8, and conductors 2| and 20. Responding to this energization relay TR follows code at the high speed or 180 rate and once more holds decoding relays H and 'Dbo'th picked up. In consequence, signal SI now shows fappro'ac'h slow as a result of unit 0 thereof receiving energy overfront contact l3, 'conductor 61-, front contact 46, conductor 21, left contact I0 and conductor 29.

When recurring pulses of the 75 negative code energy are transmitted over the section rails to entrance end location I, the polar relay 'IRP thereat continues its contacts in the shifted position (away from thatshown in Fig. 3) just described and once more causes the track relay TR to have the opposite polarity potential of each of those pulses reversely impressedthereon. Responding to that energization, relay TR follows code at the '75 pulse per minute rate; that slower action (of contacts I l-|2) causes transformer DT to hold only thecode detecting relay H picked up and allows distant decoding relay D to release; and, in consequence, signal SI now shows approach as a result of unitd being energized over front contact l3, conductor 61, back contact 46, conductor'68, left contact 41 and a conductor 1B.

Finally, when reception of all trackway energy becomes discontinuedat entrance end location I, the polar relay TR'P thereat retains-its contacts in the position to which they were last biased; the track relay TB is continuously deenergized and hence inactive; the decoding relays H and D also are deenergized and hence both released;

and signal SI now displays the stop indication as a result of unit e thereof receiving energizing current over back contact l3*and conductor 39.

From the foregoing description of the fourcode track circuit facilities of Fig.3, it will be apparent that by equipping each of a plurality of consecutive track sections with these faciliing manner. I t H As long as the signaled stretch of track remains vacant, the rails of each section therein transmit recurring puls'es of 180 positivef code energy to their entrance ends; the polar relay TRP ateach .of those entrance endsreacts to the given polarity of that energy by holding its contacts. in

the position shown in -Fig. 3; the track relay TR'for' each section responds to that received energy by'following code'at the 180 rate; the en trance end decoding relays- H- and D forea-thh section are thereby both held-picked-up and "the F775 guarding signal S for each section is kept (by relays H, D and 'I'RP) at clear.

.In the event that a train passes through the signaled stretch, the rail-shunting action of its wheels and axles produces the following effects at the entrance end of each of the sections occupied: (1) deenergization of track relay TR; (2) release of both of the decoding relays H and D; (3) placement at stop of the section-guarding signal S; and l) supply of negative code energy to the rails of the section in the immediate rear.

At the entrance end of that first rear section the pulses of that opposite polarity energy: (1) shift the contacts of relay TRP away from the position shown in Fig. 3; (2) operate relay TR at the 75 code rate; (3) cause decoding relay H only to pick up; (4) put the signal S for that first rear section-at approach; and (5) cause 180 negative code energy to be supplied to the next section to the rear.

At the entrance end of that second rear 'section the pulses of this opposite polarity energy: (1) shift the contacts of relay TRP away from the position shown in Fig. 3; (2) operate track relay TR at the 180 code rate; (3) cause decod ing relays H and D both to pick up; l) put the signal S for that second rear section at approach slow; and (5) cause 75 positive code energy to be supplied to the succeeding section to the rear.

At the entrance end of that third rear section the pulses of this given polarity energy: (1) return the contacts of relay TRP to the position shown in Fig. 3; (2) operate relay TR at the '75 code rate; (3) cause decoding relay H only to pick up; (4) put the signal S for that third rear section at approach restricting; and (5) cause 180 positive code energy to be supplied to the succeeding section to the rear.

At the entrance end of that fourth rear section the pulses of this given polarity energy: (1) cause the contacts of relay TRP to have the position shown in Fig. 3; (2) operate relay TR at the 1 code rate; (3) cause decoding relays H and D both to pick up; (4) put the signal S for that fourth rear section at clear; and (5) cause positive code energy to be repeated into the rails of the succeeding section to the rear.

In this way each train passing through the si naled (as per Fig.3) stretch of track sets up its own following protection in five-indication automatic block manner.

Summary In the novel form of coded control circuit orgam'zation which all three of the just described embodiments of my invention disclose the code following and detecting relays TR and H are immune to false responses should the polar relay TRP fail to shift its contacts upon a change in the polarity of the pulsed energy which the circuit transmits.

Upon such failure the energy pulse potential then impressed upon relay TR will have a polarity which is ineffective to operate that relay and which, accordingly, cannot produce pick-up on the part of relay H. This results in the im- -munity above stated. By that immunity the safety characteristics of all of the herein disclosed coded control circuits are greatly enhanced. Thus, the signal S which each of these circuits controls can show proceed only when the 'con tacts of the polar relay 'IRP are in positional'cor- 'respondence with the polarity of tl'ie pulsed energy which the circuit transmits. In the absence of such correspondence the signal shows "stop in the same manner as had transmission of the pulsed energy been completely discontinued.

In the combination of Fig. l, for example, assume that contacts 6-| at location II reverse the polarity of the pulsed energy with which the section rails l-2 are supplied but that relay TRP at location I fails to shift contacts 8-9 in correspondence with that reversal. The opposite polarity pulses now received from rails |-2 are impressed directly upon relay TR, but being of the wrong polarity they fail to cause contact pick-up. Relay H (at location I) now releases and lights the stop lamp R of signal SI in the same manner as were reception of all trackway energy to be discontinued at location I. In the absence of this response immunity by relay TR,

signal SI would falsely show clear (by a light-' ing of lamp G over frontcontact l3 and left contact H1) even though the advance trafiic conditions actually called for the more restrictive indication of approach.

The just made analysis of Fig. 1 also applies to Fig. 2 wherein the control circuit conductors take the form of line wires la-2a. In Fig. 3, likewise, comparable features of safety also are present. its contacts with each change of trackway energy polarity releases relay H and energizes (over back contact E3) the stop unit 6 of signal SI.

From the foregoing descriptions of Figs. 1, 2 and 3, it will be seen that in addition to enhancing the inherent safety characteristics of coded control circuits per se, I have also made important improvements in complete railway signaling systems of the coded control circuit class. In particular, I have provided novel and improved organizations for the trafiic controlling apparatus of such systems; I have enabled pulses of coded energy that recur at only one rate to select among a plurality of different signal indications; I have extended the number of signal indications which systems of the frequency There a failure of relay TRP to shift Although I have herein shown and described only three forms of railway trafiic controlling apcludes a pair of conductors, means for supplying said conductors with recurring pulses of coded energy that are of given polarity at times and of opposite polarity at other times. a polar relay connected across said conductors and responding distinctively to each polarity of the said energy pulses which are received therefrom, a code following relay which responds when and only when given direction current is passed therethrough and which stays released at all other times, contacts of said polar relay which connect said code following relay directly across said conductors when in their given polarity position and reversely across those conductors when in their opposite polarity position whereby received energy pulses of either of said two polarities pass said given direction current through thecode following relay if and only if said polar relay contacts pulse polarity, a decoding relay which picks up in response to operation on the part of said code following relay and which stays released in the absence of such operation, and signaling ap-pa ratus controlled by a contact of said decoding relay aided by a contact of said polar relay and displaying an indication of maximum restrictiveness whenever said decoding relay contact is released.

2. In combination, a control circuit that includes a pair of conductors, means for supplying said conductors with recurring pulses of coded energy that are of given polarity at times and of opposite polarity at other times, a polar relay connected across said conductors and having contacts which occupy a first position when said given polarity pulses are received by the relay and a second position when said opposite polarity pulses are received, a code following relay which responds when and only when given direction current is passed through the winding thereof and which stays released at all other times, means for causing certain of the contacts of said polar relay to connect the winding of said code following relay directly across said conductors when in their said first'position and reversely across the conductors when in their said second position whereby received energy pulses of either of said two polarities pass said given direction current through said relay winding if and only if said polar relay contacts are in positional agreement with the received pulse polarity, a decoding relay which picks up in response to operation on the part of said code following relay and which stays released in the absence of such operation, and signaling apparatus controlled by a contact of said decoding relay aided by a contact of said polar relay and displaying an indication of maximum restrictiveness whenever said decoding relay contact is released.

3. In combination, a control circuit that includes a pair of conductors which normally are capable of transmitting energy between the two ends of the circuit but which at times are rendered incapable of such transmission, means at one end of said circuit for supplying said conductors with recurring pulses of coded energy that are of given polarity at times and of 0p posite polarity at other times, a polar relay at the other end of said circuit connected with said conductors and responding distinctively to each polarity of the said energy pulses which are there received, a code following relay also at said other circuit end which responds when and only when given direction current is passed therethrough and which stays released at all other times, contacts of said polar relay which connect said code following relay directly across said conductors. when in their given polarity position and reverse 1y across the conductors when in their opposite polarity position whereby received energy pulses; of either of said two polarities pass said given direction current through the code following re 4. In combination, a control circuit that includes a pair of conductors which normally are capable of transmitting energy between the two ends of the circuit but which at times are rendered incapable of such transmission, means for supplying said conductors with recurring pulses of coded energy that are of given polarity at times and of opposite polarity at other times, a polar relay connected across said conductors and responding distinctively to each polarity of the said energy pulses which are received therefrom, a code following relay which responds when and only when given direction current is passed through its winding and which is connected with said conductors over reversing contacts of said polar relay in such manner that under and only under polarity determined positionings of said contacts received energy pulses of either of said two polarities circulate given direction current through said winding, a decoding relay which picks up in response to and only to operation on the part of said code following relay, a trafiic governing signal having two proceed units and a stop unit, circuits over which said signal units are selectively supplied with energizing current, a contact of said polar relay which in its given polarity position sets up the energizing circuit for one of said proceed units and which in its opposite polarity position sets up the energizing circuit for the other of said proceed units, and a contact of said decoding relay which in its picked up position completes the said set up proceed unit circuit and which in its released position completes the said energizing circuit for said stop unit.

5. In combination, a section of railway track, means at the exit end of said section for supplying the rails thereof with recurring pulses of coded energy that are of given polarity at times and of opposite polarity at other times, a polar relay connected with said rails at the entrance end of said section and responding distinctively to each polarity of the said energy pulses which are there received, a code following relay at said section entrance which responds when and only when given direction current is passed therethrough, contacts of said polar relay which connect the winding of said track relay directly across said rails when in their given polarity position and reversely across those rails when in their opposite polarity position whereby received energy pulses of either of said two polarities pass given direction current through said relay winding if and only if said polar relay contacts are in positional agreement with the received pulse polarity, a decoding relay at said section entrance which picks up in response to operation on the part of said code following relay and which stays released in the absence of such operation, and an entrance end signal for said section which is controlled by a contact of said decoding relay aided by a contact of said polar relay and which shows stop whenever said decoding relay is released.

6. In combination, a section of railway track, means at the exit end of said section for supplying the rails thereof with recurring pulses of coded energy that are of given polarity at times and of opposite polarity at other times, a polar relay connected with said rails at the entranceend of said section and responding distinctively to each polarity of the said energy pulses which are there received, a code following relay at said section entrance which responds when and only when given direction current is passed there-- through, contacts of said polar relay which con nect the winding of said track relay di'ectly across said rails when in their given polarity position and reversely across those rails when in their opposite polarity position whereby received energy pulses of either of said two polarities pass given direction current through said relay Winding if and only if said polar relay contacts are in positional agreement with the received pulse polarity, a decoding relay at said section entrance which picks up in response to operation on the part of said code following relay and which stays released in the absence of such operation, an entrance end signal for said section having two proceed units and a stop unit, circuits over which said signal units are selectively supplied with energizing current, a contact of said polar relay which in said given polarity position sets up the energizing circuit for one of said proceed units and which in said opposite polarity position sets up the energizing circuit for the other of said proceed units, and a contact of said decoding relay which in its picked up position completes the said set up proceed unit circuit and which in its released position completes the said energizing circuit for said stop unit.

7. In combination, a stretch of railway track, a track section included in said stretch, a source or trackway energy and a coding contact at the exit end of said section, a circuit over which said contact repeatedly connects said source with the rails of said section and thereby causes those rails to be supplied with coded energy in the form of recurring on period pulses that are separated by ofi period intervals, means included in said circuit and governed by trafiic conditions in advance of said section for causing the energy of said on period pulses to have given polarity at times and opposite polarity at other times, a polar relay connected with said rails at the entrance end of said section and having contacts which occupy a first position when the there received pulses of said trackway energy have said given polarity and a second position when those pulses have said opposite polarity, a code following track relay at said section entrance which responds when and only when given direction current is passed through the winding thereof, means for causing certain of the contacts of said polar relay to connect said track relay winding directly across said rails when in their said first position and reversely across said rails when in their said second position whereby received energy pulses of either of said two polarities pass said given direction current through said winding if and only if said polar relay contacts are in positional agreement with the received pulse polarity, a decoding relay which picks up in response to and only to code following operation on the part of said track relay, and an entrance end signal for said section which is controlled by a contact of said decoding relay aided by a contact of said polar relay and which shows stop whenever said decoding relay is released.

8. In combination, a control circuit that includes a pair of conductors which normally are capable of transmitting energy between the two ends of the circuit but which at times are rendered incapable of such transmission, apparatus at one end of said circuit which supplies said conductors with time spaced pulses of energy that recur at one or another of a plurality of different code rates and that are of given p0- larity at times and of opposite polarity at other times, decoding equipment at the other end of said circuit which is energized by the said time spaced pulses that are there received from said conductors and which selectively responds both to the rate at which those pulses recur and to the polarity of the energy of which they are constituted, and traffic governing means controlled by said decoding equipment and giving a distinctive indication during each of the said selective responses which that equipment makes.

9. In combination, a control circuit that includes a pair of conductors, means for supplying said conductors with pulses of coded energy that recur either at a high speed rate or at a low speed rate and that are of given polarity at times and of opposite polarity at other times, a polar relay connected across said conductors and responding distinctively to each polarity of the said energy pulses which are received therefrom, a code following relay which responds when and only when given direction current is passed therethrough, contacts of said polar relay which connect said code following relay directly across said conductors when in their given polarity position and reversely across those conductors when in their opposite polarity position whereby received pulses of either of said two polarities pass said given direction current through the code following relay if and only if said polar relay contacts are in positional agreement with the received pulse polarity, a code detecting relay which picks up in response to operation by said code following relay at either of said high and low speed code rates, a code distinguishing relay which picks up when and only when said code following relay operates at said high speed code rate, and apparatus controlled by a contact of said code detecting relay aided by a contact of said code distinguishing relay together with a contact of said polar relay. 10. In combination, a control circuit that includes a pair of conductors which normally are capable of transmitting energy between the two ends of the circuit but which at times are rendered incapable of such transmission, means at one of said circuit ends for supplying said conductors with pulses of coded energy that recur either at a high speed rate or at a low speed rate and that are of given polarity at times and of opposite polarity at other times, a polar relay connected across said conductors at the other of said circuit ends and responding distinctively to each polarity of the said energy pulses which are there received, a code following relay also at said other circuit end which responds when and only when given direction current is passed therethrough, contacts of said polar relay which connect said code following relay directly across said conductors when in their given polarity position and reversely across those conductors when in their opposite polarity position whereby received pulses of either of said two polarities pass said given direction current through the code following relay if and only if said polar relay contacts are in positional agreement with the received pulse polarity, a code detecting relay which picks up in response to operation by said code following relay at either of said high and low speed code rates, a code distinguishing relay which picks up when and only when said code following relay operates at said high speed code rate, and signaling apparatus controlled by a contact of said code detecting relay aided by a contact of said code distinguishing relay together with a contact of said polar relay and displaying an indication of maximum restriction whenever said code detecting relay is released.

11. In combination, a control circuit that includes a pair of conductors, means for supplying said conductors with recurring pulses of coded energy that are of given polarity at times and of opposite polarity at other times, a polar relay which receives said coded energy from said conductors and which has a contact that occupics a first position when the received energy is of said given polarity and a second position when the received energy is of said opposite polarity, a code following relay having an operating winding and being provided with a contact which picks up when and only when given direction. current is passed through said winding and which stays released at all other times, means including said polar relay contact for connecting said code following relay winding in direct relation with said conductors when that contact is in said first position and in reverse relation with those conductors when that contact is in said second position whereby received energy pulses of either of said two polarities pass said given direction current through the code following relay winding if and only if said polar relay contact is in positional agreement with the received pulse polarity, a decoding relay which picks up in response to code following operation on the part of said code following relay contact and which stays released in the absence of such operation, and signaling apparatus controlled by said decoding and polar relays acting in cooperation and displaying an indication of maximum restriction whenever said decoding relay is released.

FRANK H. NICHOLSON.

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