US2335765A - Coded highway crossing control system for railroads - Google Patents

Description

T. J. JUDGE Filed O'Q't. 11 1941 3 Sheets-Sheet 1 Na ENE RE INVENTO Q? A ATTORI'VEY CODED HIGHWAY CROSSING CONTROL SYSTEM FOR RAILROADS Nov. 30, 1943.

3 Sheets-Sheet 2 TLJ. JUDGE CODED HIGHWAY CROSSING CONTROL SYSTEM FOR RAILROADS Filed Oct. 11, 1941 IgyENTO BY l ATTORNEY mm NE E 15 mm. ow T3 mu v n .fiw m E28 Nov. 30, 1943.

Nov. 30, 1943. T. J. JUDGE CODED HIGHWAY CROSSING CONTROL SYSTEM FOR. RAILROADS Oct. 11, 1941 3 Sheets-Sheet 3 INVENTOR m m. ATTORNEY Qua.

.Paten'ted Nov. 30, 1943 CODED HIGHWAY CROSSING CONTROL SYSTEM FOR RAILROADS Thomas J. Judge, Rochester, N. Y., assignor to General Railway Signal Company, Rochester,

Application October 11, 1941, Serial No. 414,584

15 Claims. (Cl. 246-130) The present invention relates to railway signalling and highway crossing signalling for railway systems including coded track circuits and more particularly to means for preventing a code fight when driven codes ar applied to opposite ends of a track section, as for instance, upon vacating of such track section or a sub-section in advance thereof after it has been temporarily occupied.

As is well known by one skilled in the art of railway and highway crossing signalling it is desirable to display highway crossing signals when a train approaches and while passing over the highway but to discontinue such signal as soon as the rear end of the train has passed over the highway. Since trains, and particularly work trains, may move in both directions on a double track railroad where railway signalling is provided for one direction of train movement only, it becomes apparent that an approachsec- 'tion must be provided on the railway track on teach side of the highway extending a distance 'to give an adequate advance highway crossing signal manifesting the approach of a train. This distance is very short as compared with the usual block so that it is necessary in many instances to divide a block into cut sections, two of these out sections constituting approach sections to the highway. Also it is apparent that mean 'for manifesting the direction of train movement is necessary in a system of this kind.

In accordance with the present invention it is proposed to divide a signalling block or section into a plurality of sub-sections, three such subsections having been illustrated, to provide means for repeating the code of a sub-section into the next sub-section in the rear and to provide one of these sub-sections or cut sections with means for creating an inverse code at a time when a driven code is present and to provide means for creating an auxiliary or special driven impulse code in the same directionas said inverse code at times when a driven code is not present, and to so construct the apparatus that if a regular driven code is applied to one end of the track section when an auxiliary or special driven impulse code is already applied to the opposite end of th track section that no long sustained code fight will exist. It is also proposed to so construct the apparatus for repeating More specifically it is proposed to avoid a code fight by making the impulses of a specially applied auxiliary driven code much shorter than the impulses of a regular driven code, and preferably of the same durations as the impulses of an inverse code, so that the longer impulses of a regular driven code will dominate the shorter impulses of such auxiliary driven code so that if a code fight should occur it will be of very short duration.

Other objects, purposes and characteristic features of the present invention will be described hereinafter and will in part be understood from the accompanying drawings, of which Figs. 1A, 1B and 10 show three successive portions of a railway signalling system embodying the present invention.

Structure Referring to the drawings the track rails IU of a railway signalling system have been shown divided into blocks and cut sections or subsections by insulating joints ll of which the block N, which is divided into cut sections NI, N2, and N3 and the adjacent ends of the blocks M and 0 only have been illustrated. This railway track is crossed by a highway which has been designated l5. The highway has been provided with highway crossing signals l6 which are flashed by flashing relay FR and which are controlled in accordance with traiiic conditions by decoding relays TNP2 and IRNBP and by an interlocking relay ILR. Railway signals S2 and S4 have been provided, of which the signal S2 governs the movement of east-bound trafiic into the block-N and the signal S4 governs the east-bound moveto the block or track section, and the inverse track relays, of which one (IRNI) only has-been shown, have been designated IR with the proper sufiix corresponding to the cut section in which they are located. This relay IRNI follows the impulses of the inverse code and the impulses of the auxiliary code, as the case may be. All of these relays CFT, AR and IR are preferably of polar construction so as to make them quick acting and so as to cause no operation thereof if current of the wrong polarity is inadvertently applied to the track rails.

The inverse code track relay IRNI is preferably shunted by a half-wave rectifier R to cause proper timing of the relay. The series approach relays ARM and ARN3 each preferably have an adjustable resistance Tl connected in multiple therewith which also serves as a series resistance for the associated track battery and have an adjustable series resistance r2 connected in series therewith to adjust the relay for proper operation so that it will pick up only if the track section in which it is included is occupied. The resistance Ti is of course made adjustable to apply the proper amount of current to the track section to cause proper functioning of the code following track relay at the opposite end of such section. Each of the main track batteries has been designated 13 followed by a sufiix designating the block or cut section with which it is associated,'whereas each of the inverse track batteries has been designated by the letter 13 followed by a sufiix defining the track section in which it is included. The approach code impulse following relay ARM (see Fig. 1A) is repeated by an approach repeater relay ARMP, which latter relay is shunted by a rectifier R5 to render it slow dropping so as not to drop between impulses of a code, and which approach repeater relay ARMP is repeated by a second repeater relay ARMPP. In a similar manner the approach code impulse following track relay ARNS (see Fig. 1C) is repeated by an approach repeater relay ARNPS, which is shunted by a half-wave rectifier R1 to render it slow dropping so as not to drop between impulses of a code, and which approach repeater relay ARNPB is repeated by a second repeater relay ARNPPS.

Adjacent the signal S2 is provided suitable decoding apparatus for causing a home relay H2 to assume its energized position when either a 75 impulse per minute code or a 180 impulse per minute code is received and is provided with a distant relay D2 which assumes its energized position only if a 180 impulse per minute code is received. The home relay H2 is provided with the usual full-wave rectifier R! which is fed from a transformer THE which in turn is fed from a coding contact N5 of the code impulse following track relay CF-TNI. In a similar wa the distant relay D2 is fed from a full-wave rectifier R2 which in turn is fed from a tuned transformer TDZPP, which in turn is fed by an auto transformer TDZP, which in turn is fed by the transformer TDZ, which in turn is also fed from the coding contact M5 provided the approach repeater relay ARIVIP assumes its attracted position. Similar apparatus is provided for controlling the signal St for which reason like parts of this apparatus has been designated by like reference characters as that for the signal S2 except that these reference characters include the number 4 instead of the number 2.

The signal S2 is controlled through a front contact I7 of the approach repeater relay ARMPP, the contact H8 of the distant relay D2, and the contacts'lQ and 26 of the home relay H2. The signal St is similarly controlled through circuits having contacts designated by similar reference characters.

The approach repeater relay ARMP is provided with front contacts 25 22 and 23 which per- .form functions hereinafter described. This approach relay ARMP is controlled through a front contact 25M of the approach relay ARM and is sufficiently slow dropping that intermittent closure of this contact 25M, whether at the impulse per minute rate or the 180 impulse per minute rate, will cause it to assume its energized position continuously.

At the exit end of each block are provided coding contacts '55 and I which are electrically operated devices and which when active close and. open a circuit 75 or 180 times per minute depending upon whether the contact 75M or the contact [80M is referred to. These contacts have been designated 15M and IBQM for the block M and have been designated l'iiN and ltilN for the block N and are driven by motors MM and MN, respectively. A similar coding contact 75X (see Fig. 1A) driven by a motor MX, is also employed for reasons hereinafter pointed out. These contacts 15M, 30M, TEN and lEdN control coding relays M, IBEiCM, TECN and iSGCN, respectively. The home relay H2 is also provided with contacts 21 28 and 29 Referring now to the apparatus associated with the highway crossing signals it and illustrated in Fig. 1B of the drawings, the inverse code impulse following track relay IRN l is provided with a front repeater relay IRNFP and a front and back repeater relay or oscillation manifesting relay IRNBP which are controlled through the front point and back point, respectively, of the contacts 30 of this impulse following relay IRNI. These repeater relays are shunted by half-wave rectifiers R8 and R9, respectively. These repeater relays are code responsive or decoding relays rather than impulse responsive and remain energized continuously so long as the inverse track relay IRNI operates at either the '75 impulse per minute rate or the impulse per minute rate. The code following track relay CFTN2 is provided with a contact 3! which controls the code responsive or decoding relays TNPZ and TNPPZ and the impulse repeating relay TNPPP2, the code responsive repeater relay TNPPZ also being controlled through a front contact 32 of the code responsive relay TNPZ. The impulse repeating relay TNPPP2 is controlled through a front contact 33 of a code responsive repeater relay TNPPZ. By this construction the code responsive repeater relay TNPP2 will be continuouslyenergized only if the contact 32 is vibrated at either the '75 or the 180 impulse per minute rate, and the impulse repeating relay TNPPPZ is intermittently picked up and dropped away only if this contact 3| is vibrating to an extent to hold the relay TNPP2 in its energized position. This impulse repeating relay TNPPPZ in turn through the medium of contacts 3 3 and 35 re-applies the codereceived at the West end of the section N2 to the east end of the section Ni. It should be noted that closure of front contact 3&- of relay TNPPPZ connects the track battery BNl in series with inverse code track relay IRNi but not in effect because the inverse track relay IRN! is then shunted by front contact 35 of relay TN'PPPZ. When these contacts and 35 are down the inverse code track relay lRN! is connected directly across the track rails.

Referring now to Fig. 10 it will be readily understood that if either a 75 impulse per minute code or a 180 impulse per minute code is received by the code following track relay CFTO- the home relay H4 will assume its energized position, the

distant relay D2 assuming its deenergized position by reason of the approach contacts 2 l and 22 included in its energizing circuits being open. in

the absence of an east-bound approaching train in sub-section N3. It is also readily seen that with the home relay 1-14 assuming its energized position that an energizing circuit is closed for the coding relay l80CN, which then through its front contact 3lN and through front contact 29 of the home relay H4 may apply a 180 impulse per minute code to the east end of the section N3 through a circuit including the track battery BN3 and the series resistance T1 in multiple with the approach relay ARNS. It is also readily, understood that if the home relay H4 is deenergized a 75 impulse per minute code will be applied to the track circuit of the section N3 in the same way by the contact 38N of the coding relay 15CN and through back contact 29 of home relay H4. The code received at the West end of the sub-section N3 will then be repeated into the east end of the sub-section N2 by back contact repeating through the medium of the back contact 39 of the code impulse following track relay CFTN3 and the track battery BN2. Similarly, the code received at the west end of the sub-section N2 will be repeated into the east end of the sub-section N! by front contact repeating through the medium of front contact 3! of th code impulse following track relay CFTN2, the track battery BN1 and the impulse repeating relay TNPPPZ and its front 3 and 35.

The code so repeated from sub-section to subsection will be received by the code following track relay CFTNl associated with the signal S2 and will be there decoded by the decoding apparatus including home relay H2 and distant relay D2 which will in turn control the signal S2. A code will be applied to the east end of the block M in accordance with the position of the home relay H2 in the same manner as a code is applied to the east end of the sub-section N3 in accordance with the home relay H4 as just explained.

Attention is directed to the fact that with the home relay H2 in its energized position, as is normally the case, a coding circuit including th back contact 4 l of the code impulse following track relay CFTNI front contact 28 of the home relay H2, back contact 42 of the impulse relay A. the winding of the impulse relay B is closed. This impulse relay B is shunted by a half-wave rectifier RIO. It is readily seen that the contacts M and 45 of this impulse repeating relay B will connect the inverse code battery IBM in (also at times used to create an auxiliary driven code) series with the code impulse following track relay CFTNI and will at the same time short circuit this code impulse following track relay. Since the circuit for the impulsing relay B includes a back contact 42 of the impulsing relay A it will be readily seen that upon proper timing of these relays, the relay A being partly shunted by a resistance r i, the impulses created by the impulsing relay B may be made much shorter than are the spaces between the impulses of the driven code received by the code following track relay CFTNE. In any event, these relays are so timed that the inverse impulses created in the track circuit for section NI fall in the time spaces between the impulses applied to the east end of this track section Ni and are much shorter than are the spaces between these impulses.

These inverse code impulses applied by the impulsing relay B through the medium of the contact M of the code following track relay CFTNI result in the intermittent energization of the inverse code impulse following track relay IRNI and therefore result in the continuous energizarectifier Hi i may be of a construction such as disclosed in the tion of the front code repeater relay IRNFP and the oscillation manifesting relay IRNBP, the oscillation manifesting relay IRNBP being also controlled through a front contact 40 of the front repeater relay IRNFP. This inverse code therefore holds the front contact 41 of the oscillation manifesting relay IRNBP closed to hold one of the windings of the interlocking relay ILR energized, the other winding of this interlocking relay being held energized through a front contact 48 of the decoding relay TNP2. This latter relay also serves as a track repeater relay in that it will assume its energized position if the code following track relay CFTNZ is continuously energized. This relay TNPZ is shunted a half-wave The interlocking relay ILR, which prior application of Little, Ser. No. 314,923, filed January 22, 1940, or patent of Field No. 1,824,131 granted September 22, 1931, may through the medium of its contacts 49 and 5E; control both the flashing relay FE and the highway crossing signals 16. It may be pointed out that this flashing relay FR may be of a construction such as is illustrated in the patent to Bryant No. 2,132,097 granted October 4, 19318.

Itmay be pointed out here that all of the relays which follow the impulses of a code, that is, pick up for each impulse and drop between each of two successive impulses, have been called code impulse following or impulse repeating relays whereas all of the relays which are maintained up in response to a series of impulses and which do not drop between successive impulses have been called code responsive or decoding relays, these latter relays in some instances distinguishing between difierent codes and in other instances assume their energized position in response to any code. The coding relays 15CM, IBQCM, 15CN and IBDCN, the impulse repeating relay TNPPPZ, the relays A and B have therefore been called impulse repeating and impulsing relays whereas each of the track relays CFTNI, CFTNZ, CETNB,

following. S milarly, each of the relays ARMP,

vH2, D2, TNPZ, TNPPZ, IRNFP, IRNBP, ARNP3,

H4 and D4 are code responsive or decoding relays. Relays ABMPP and ARNPPE are slow dropping repeater relays.

Operation Let us assume that there is an east-bound train moving in the block M. The presence of this train causes the track circuit coded current which is supplied by the intermittent operation of the contact 31M of the coding relay ISGCM to increase to a value where the approach relay ARM is intermittently picked up. Intermittent closure of the front contact 25M of this approach relay decoding ARM causes the approach repeater or decoding relay ARMP to assume its pickedup condition continuously. This results in the closure of its approach contacts H and 22 and in continuous energization of the distant decoding relay D2, the code impulse following track relay CFTNi, for reasons heretofore pointed out,

.now being intermittently picked up at the impulse per minute code rate. The front contact 23 of the approach repeating relay ARMIP clear lamp G for the signal S2 is therefore illuminated.

Let us now assume that the train in the block M accepts the clear signal S2, it being assumed that trafiic conditions in advance are favorable, and moves into the rear sub-section NI. This will, of course, result in continuous deenergization of the cod impulse following track relay CFTNI and also in the continuous deenergization of the inverse code impulse following track relay IRNI located at the exit end of the sub-section N I. Continuous deenergization of the code following track relay CFTNI will, of course, cause the signal S2 to assume its stop condition and the dropping of the home relay H2 will also result in the closure of the circuit for the coding relay l5CM and in the deenergization of the coding relay IBQCM. Continuous deenergization of the inverse code impulse following track relay IRNI will cause the front and back point inverse code responsive relays IRNFP and IRNBP (see Fig. 1B) to assume their deenergized position to result in the opening of front contact ill or" the back point code responsive relay IRNFP which in turn results in the deenergization of the left-hand winding of the interlocking relay ILR. As the left-hand armature of the interlocking relay ILR drops it mechanically locks and prevents dropping of the right-hand armature of this interlocking relay ILR until both of the windings of this relay ILR have been re-energized in overlapped relation. With the left-hand contact 49 in its retracted position and the right-hand contact 5!) in its attracted position energy is applied to the flashing relay FR to cause intermittent opening of its contact 52, thereby resulting in the flashing of the highway crossing signals l6.

Let us now assume that the rear end of the east-bound train has advanced beyond the signal S2 but is still in the rear cut section NI. Under this condition the back contact 45 of the code following track relay CFTN! is continuously closed as is also the back contact 28 of the home relay H2 resulting in the closure of an energizing circuit for the impulse creating relays A and B which includes the coding contact X. This coding contact 15X is closed and opened seventyfive times per minute and results in intermittent picking up of the impulse creating relays A and B at the rate of seventy-five times per minute. The impulse creating relay A is, of course, somewhat slower in picking up than is the impulse creating relay B as a result of which this relay B is energized a very short time its energizing circuit being broken at the back contact 42 of the impulse creating relay A. Intermittent picking up of the impulsing relay B will, of course, send a 75 impulse per minute code into the west end of the track circuit for the rear sub-section NI, the impulses of this code being very short and substantially of the same duration as those of the inverse code but being long enough to intermittently pick up the inverse code impulse following track relay IRNl when the track rear sub-section Ni becomes unoccupied.

Let us now assume that the east-bound train moves by the crossing i5 and in so doing deenergizes the code impulse following track relay CFTNZ continuously resulting in the deenergization of the relays TNPE, TNPP2 and TNPPPZ. Dropping of the decoding relay TNP2 will by the opening of its front contact 48 result in the deenergization of the right-hand coil of the interlocking relay ILR. Th deenergization of the right-hand coil of interlocking relay ILR will not result in the opening of front contact because the armature for this portion of the relay has been locked up, the partial dropping of the righthand armature will however complete the mechanical locking of the interlocking relay so that the front contact 5!! will not open (the righthand winding being deenergized) even after the left-hand coil of this relay ILR is again reenergized. In other words, the crossing signal I6 will continue to flash until the rear end of the train has passed entirely out of the rear sub-section Ni and has allowed reenergization of the left-hand winding of the interlocking relay ILR and the opening of its back contact 49.

As the east-bound train moves entirely out of the rear sub-section N5 the code following track relay CFTNi will not be picked up either intermittently or continuously because the code impulse repeating relay TNPPZ is continuously deenergized and no code is applied to the east end of the rear sub-section Ni. The inverse code repeater track relay IRNl is, however, intermittently picked up in response to the auxiliary driven code applied at the west end of section N! by the coding contact X and its associated relays A and B (see Fig. 1A), and this auxiliary code causes the picking up of the front and back code responsive relays IRNF'P and IRNBP and the reenergization of the left-hand winding of the interlocking relay ILR. This causes opening of back contact 49 of relay ILR and stops the flashing operation of the highway crossing signals it.

Let us now assume that the east-bound train moves entirely out of the sub-section N2 and moves entirely into the advance sub-section N3. This results in the continuous deenergization of the code impulse following track relay CFTN3 and in the continuous closure of its back contact 39. Under this condition the track battery BN2 is continuously connected to the east end of the track section N2 and results in the continuous energization of the code impulse following track relay CFTNE. With the code following track relay CFTNZ' continuously picked up it will through the continuous closure of its front contact 3| result in the continuous energization of the track repeater relay Tl-?2, which results in the closure of its front contact 48 and in the unlocking oi the mechanical locking feature of the interlocking relay ILR, thus restoring tlus interlocking relay fully to its normal condition. This continuous picking up of the code impulse following track relay CFTNZ, it should be noted, does not result in the transmission of a driven code from the right-hand end toward the lefthand end of the rear sub-section N! 50 that the auxiliary driven code which is created by the coding contact 'EfiX and applied to the west end of this rear sub-section N5 is still effective to hold the contact ll in the energizing circuit for the left-hand coil of the interlocking relay ILR closed. The entrance of the train into the advance sub-section N3 and its bridging of the rack rails causes the series approach relay ARNS to be intermittently picked up resulting in the continuous picking up of the approach repeater relay ARNP3 and in the picking up of the second approach repeater relay ABNPPEB. The picking up of these relays results in the approach clearing of the signal S4 for reasons explained in connection with signal S2, assuming trallic conditions in advance to be clear.

Let us now assume that the east-bound train moves into the block 0. This advance of the train results in the deenergization of the home relay H4, in the deenergizing of the distant relay D4 and in the placing of the signal S4 in its stop condition. As the rear end of the train now passes out of the advance sub-section N3, the home relay E4 of course being deenergized causes a '75 impulse per minute code to be applied to the east end of the advance sub-section N3 through the medium of the coding relay 15CN which is energized through the back contact 2'! of the home relay H4. This 75 impulse per minute code will, of course, result in the picking up and dropping of the code impulse following relay CFTN3 at the 75 impulse per minute rate, which in turn results in the intermittent picking up of the code impulse following track relay CF'INZ at the 75 impulse per minute rate. Intermittent picking up of the contact 3| of the code impulse following track relay CFTNZ will result in the continuous picking up of the repeater relays TNPE and TNPP2 but will result in the intermittent picking up of the impulse repeating relay TNPPP2. It will be observed that the usual '75 impulse per minute code is now applied to the east end of the rear sub-section NI through the front contacts 33 and 35 of relay TNPPPZ, this code consisting of ons and "offs which are substantially of equal duration. It will be remembered that the coding contact 15X associated with the signal S2 is also applying a '75 impulse per minute auxiliary driven code to the west end of this same rear sub-section NI, this latter "l impulse per minute auxiliary driven code however consisting of short ons and long offs. Since the impulses applied to the east end of the rear sub-section NI are comparatively long as compared with the on impulses of the auxiliary code applied to the west end of this track section, the longer impulses dominate the shorter impulses irrespective of whether these impulses are in synchronism or not, because the code impulse following track relay CFTNI can be picked up intermittently for sufficient time periods to cause the home relay H2 to assume its energized position. As soon as this occurs the back contact 28 of this home relay H2 which is included in series with the coding contact X is opened and the 75 impulse per minute auxiliary driven code produced by contact 35X is removed from the west end of the track section NI. The closing of the front contact 28 of home relay H2 allows the back contact M of the code impulse following track relay CFTNI to cause inverse code impulses however to be applied to the west end of the track section NI during the off periods of the driven code through the medium of the short'impulse creating relays A and B, and the inverse code impulse following track relay IRNI will thereafter be intermittently picked up by an inverse code rather than by a generated auxiliary code. Under the condition assumed both of these codes are 75 impulse per minute codes in which the impulses are comparatively short, the principal difference between the two codes is that the impulses of the inverse code fall between the impulse of the driven code whereas this is not necessarily true of the impulses of the auxiliary code produced by contact 15X.

It is readily seen that if'a west-bound train, such as a work train or an east-bound train making a back-up move, should pass over the crossing IS the right-hand coil of the interlocking relay ILR will be first deenergized resulting in the closure of a highway crossing signal circuit through front contact 29 and back contact 5|] of has passed entirely out of the sub-section N2 and into the sub-section N i. In all other respects the presence of a west-bound train produces the same effect as the presence of an east-bound train on each of the track circuits.

The code responsive relay TNPP2, it will be noted, is of rather unusual construction. This construction has been resorted to in order to render this relay very quick to pick up and very slow dropping. It will be noted that when this relay TNPP2 assumes its deenergized position the lower winding is short circuited through back contact 54 of this relay, whereas when it assumes its energized position its upper winding is short circuited by the front contact 54. If We assume the upper coil of this relay to have a number of turns of proper size to have an ohmic resistance of 50 ohms, as has been found desirable in practice, and assume the lower winding to have an ohmic resistance of 200 ohms, also used in practicing the invention, the resistance of the relay during its transient condition will have an ohmic resistance of 250 ohms because the two windings are then connected in series and are both unshunted. The relay core structure is also linked with rings or slugs of copper or other conducting material. The action of these slugs, shown conventionally by shading, is further augmented by the action of the rectifier R92 which bridges the'winding or windings of the relay TNPP2 connected between the inlet and outlet terminals. This rectifier allows the inductive kick of the relay to produce a sustaining current to delay the dropping of the relay. The relay is, of course, rendered quick picking up by reason of the fact that the low resistance coil (upper coil) is only included in the energizing circuit when they relay is down. In other Words, the relay TNPP2 is provided with a single quick pick-up feature and with two slow dropping features.

The applicant has thus evolved and disclosed a signalling system involving coded track circuits which not only employ inverse code generating apparatus for generating inverse codes intermeshed with driven codes but in which there is also provided a so-called auxiliary driven code, which is substituted in place of an inverse code when the inverse code cannot be applied because a sub-section in advance of the sub-section under consideration is occupied and removes the driven code from the sub-section under consideration. The nature of the regular driven code and the auxiliary driven code is such, by reason of the differences in the length of their impulses, that if such codes are applied at opposite ends of the same track section no prolonged code fight will result in that the regular driven code will dominate the auxiliary driven code. It is, of course, understood that the particular system which has been selected to illustrate one form the present invention may take does not exhaustall possible circuits and devices which may be employed to carry out the underlying principles of the invention and it should be further understood that various changes, modifications and additions may be made to adapt the invention to the particular railway signalling systems and highway crossing problems involved in practicing the invention, and that these deviations may be made without departing from the spirit or scope of the invention except as demanded by the scope of the following claims,

What is claimed as new is:

1. In combination, a section of track divided from adjacent sections by insulating joints, means for transmitting a driven code in one direction through the track rails of said section including a coder and a source of current at one end and a driven code impulse following track relay at the other end, means for transmitting an inverse code in the other direction through the track rails of said section including a source of current at said other end intermittently applied thereto by means controlled by said driven code impulse following track relay and including an inverse code impulse following track relay at said one end, means for connecting said inverse code impulse following track relay to said one end of said track section only when said first mentioned source of current is not connected to said track section, and means for transmitting an auxiliary driven code consisting of shorter impulses than the impulses of said driven code transmitted from said other end to said one end of said section when said driven code impulse following track relay is continuously deenergized,

whereby if a driven code is applied to one end of such section while an auxiliary driven code applied at the other end is present such first mentioned driven code will dominate said auxiliary driven code.

2. In combination, a track section; a signal for governing the entrance of traffic into said track section, a home relay for controlling said signal, a code impulse following track relay intermittently picked up in accordance with code impulses separated by off periods applied to the opposite end of said track section, decoding apparatus for controlling said home relay by energizing it only when said code impulse following relay is intermittently picked up, an inverse coding relay having contacts to substitute a source of current for said code impulse following track relay, and two energizing circuits for said inverse coding relay one including a back contact of said code impulse following relay and a front contact of said home relay and the other including a coding contact and a back contact of said home relay.

3. In combination, a section of track divided from the remaining track by insulating joints, insulating joints for dividing said section into sub-sections, means for applying a driven coded current across the rails at the exit end of the forward sub-section, means for applying coded current across the rails at the exit end of a rear sub-section in accordance with the driven code received at the entrance end of said forward subsection, inverse coding means controlled by the driven code received at the entrance end of said rear sub-section for applying an inverse code across the rails at such entrance end of said rear sub-section the impulses of said inverse code falling between the impulses of said driven code transmitted through the rails of said rear subsection, whereby no inverse code will be present in said rear sub-section if said forward subsection is occupied, and means including said inverse coding means for applying an auxiliary driven code across the rails of the entrance end of said rear sub-section the impulses of which are shorter than the impulses of said first mentioned driven code when no inverse code can be generated because no driven code is there received, whereby if said forward sub-section becomes unoccupied and re-applies a driven code to the exit end of said rear sub-section while an auxiliary driven code is being applied to the entrance end of said rear sub-section the said first mentioned driven code by reason of its longer impulses will dominate and change the auxiliary driven code to an inverse code.

4. In combination; a section of railway track; means for transmitting a multiple impulse driven code in one direction through the track rails of said section including a source of current and a coding contact at the exit end of said section and a code impulse following track relay at the entrance end of said section; inverse code source of current; means for transmitting an inverse code of which the impulses fall between the impulses of said driven code and including a contact of said code impulse following track relay and two impulsing relays in multiple controlled thereby, one of which is controlled through the back contact of the other, and front contacts on said one relay for, when shifted, substituting said inverse code source of current for said code impulse following track relay; a home relay at said entrance end of said section controlled by said code impulse following track relay and energized when said code impulse following track relay manifests the reception of a code; and other means effective to intermittently energize said impulsing relays when said code impulse following track relay and said home relay are both deenergized.

5. In combination with a section of track; a railway trafilc signal at the entrance to said section; a highway crossing signal near the exit end of said section and governing highway traffic; a track circuit including a code impulse following track relay at the entrance to said section, and means for applying a driven code to the exit end of said section; decoding apparatus at the entrance end of said section controlled by said code impulse following track relay and governing said relay traflic signal; means governed by said code impulse following track relay for applying an inverse code to said track circuit at the entrance end of said section of which the impulses fall between the impulses of said driven code; inverse decoding means governed by said inverse code and controlling said highway crossing signal; and means effective if said code impulse following track relay is continuously deenergized for applying an auxiliary driven code consisting of impulses which are shorter than the impulses of said first mentioned driven code to said track circuit at the entrance end, said auxiliary driven code also controlling said inverse decoding means and in turn said highway crossing signal; whereby if such first mentioned driven code is applied to the exit end of said track circuit while an auxiliary driven code applied to the entrance end of said section is present such first mentioned driven code by reasons of its longer impulses will dominate and remove said auxiliary driven code and re-apply said inverse code.

6. In combination, a track section, means for applying a first driven code to one end ofsaid section, a code impulse following track relay at the other end of said section controlled by said driven code, a decoding relay controlled: by said code impulse following track relay, and means controlled by said code impulse following track relay and said decoding relay for applying an inverse code to said other endof said track section when said decoding relay assumes its energized position and applying an auxiliary driven code of which the impulses are shorter than are the impulses of said first driven code to said other end of said track section when said decoding relay assumes its deenergized position.

'7. In combination, a track section, means for applying a first driven code to one end of said section, a code impulse following track relay at the other end of said section controlled by said driven code, a decoding relay controlled by said code impulse following track relay, and means controlled by said code impulse following track relay and said decoding relay for applying an inverse code of which the impulses fall between the impulses of said driven code to said other end of said track section when said decoding relay assumes its energized position and applying an auxiliary driven code to such other end of said track section of which the impulses are shorter than are the impulses of said first driven code when said decoding relay assumes its deenergized position, whereby an inverse code may be transmitted in a track section in the opposite direction from that of said first driven code when such first driven code is present and an auxiliary driven code may be transmitted in such track section in such opposite direction during the absence of such first driven code.

8. In a track circuit; of code creating means for creating a code and applying it to one end of said track circuit in which the impulses are shorter than the time spaces therebetween comprising, a first coding contact intermittently closed in a manner that the periods of closure and the periods of opening are substantially the same, a second coding contact for intermittently closing said track circuit, and means for operating said second contact in response to operation of said first contact including two relays in multiple which are controlled by said first contact and of which the second relay is controlled through a back contact of the first of said two relays and of which said second relay controls said second contact, whereby said second relay is energized only during closure of said first contact so long as said first relay has not yet assumed its energized position; and a code impulse following relay at the other end of said track circuit responsive to the impulses of said code.

9. In combination, two adjacent track sections consisting of a forward section and a rear section, a code impulse following track relay at the entrance end of the forward track section, coding contacts at the exit end of the rear track section, said exit and said entrance ends being adjoining ends of said track sections, a back repeater slow dropping relay controlled by said code impulse following track relay which assumes its energized position continuously when said code impulse following relay assumes its deenergized position intermittently, an impulse repeating relay controlling said coding contacts, and an energizing circuit for said impulse repeating relay including a front contact of said code impulse following track relay and a front contact of said back repeater slow dropping relay.

10. In combination, two adjacent track sections, a code impulse following track relay at the entrance end of the forward track section, a coding contact at the exit end of the rear track section, said exit and said entrance ends being adjoining ends of said track sections, a front repeater slow dropping relay controlled through a front point of said code impulse following track relay, 9, back repeater slow dropping relay for said code impulse following track relay which is controlled through a back point of said code impulse following track relay and a front point of said front repeater slow dropping relay and assumes its energized position continuously when said front repeater slow dropping relay assumes its energized position and said code impulse following track relay assumes its deenergized position intermittently, an impulse repeating relay controlling said coding contact, and an energizing circuit for said impulse repeating relay including a front point of said code impulse following track relay and a front point of'said back repeater slow dropping relay.

11. In combination, a forward track section, a second track section to the rear of said forward track section, a wayside signal and a, highway crossing signal to the second of the entrance end to said rear track section, code responsive means and track circuit energy responsive means at the entrance end of said second track section for when active respectively holding said wayside signal at clear and holding said highway crossr ing signal inactive, a code following track relay at the entrance end of said forward track section having a back contact included in the track circuit of said second track section, and means forapplying coded energy to the exit end of said forward section, whereby if both of said sections are unoccupied said wayside signal indicates proceed and said highway crossing signal is maintained inactive if said forward section is occupied and said second section is unoccupied said wayside signal is put to stop but said highway crossing signal is held inactve in response to current flowing through said back contact but if said train moves from said forward section into said second section both said wayside signal indicates danger and said highway crossing signal is rendered active.

12. In combination, a track section divided by insulating joints into a first and a rear sub-section, a highway crossing signal at the junction between said sub-sections, means for applying a driven code consisting of current impulses separated by off periods to the track rails at the exit end of said first sub-section, means at said junction including a first code impulse following track relay connected across the rails of said first section for relaying said driven code received at the entrance of said first sub-section into track rails at the exit end of said rear sub-section, a second code impulse following track relay connected across the track rails at the entrance end of said rear sub-section responsive to the impulses of said driven code when received, code responsive means at the entrance end of said rear sub-section controlled by said second code impulse following track relay, means including said second code impulse following track relay and effective when said code responsive means is active to create and apply an inverse code to the track rails at the entrance end of said rear subsection so that these impulses fall in said off periods of said driven code and to create an auxiliary driven code when said code responsive means is inactive, decoding means at the exit end of said rear sub-section responsive if either an inverse code or a driven auxiliary code is received, and interlocking means controlled by said first code impulse following track relay and by said decoding means for rendering said highway crossing signal active only So long as the first occupied of said sub-sections is occupied by a train moving over said track section irrespective of the direction of movement of such train.

13. In combination; a section of track divided by insulating joints into a first sub-section and a rear sub-section; means for transmitting a driven code through the track rails of said first sub-section from one end to the other end thereof; receiving means for receiving said driven code at the other end; means including said receiving means for transmitting a driven code from one end to the other end of said rear sub-section consisting of a series of current impulses separated by off periods; means for transmitting an inverse code, consisting of impulses in the ofi periods of said driven code, from said other to said one end of said rear sub-section; means for transmitting an auxiliary driven code from said other end to said one end of said rear subsection when no driven code is transmitted from said one end to said other end of said rear subsection; a highway crossing signal at the junction of said sub-sections; code responsive means at said one end of said rear sub-section responsive to said inverse code and to said auxiliary driven code; and means controlled by said receiving means at said other end of said forward subsection and by said code responsive means at said one end of said rear sub-section for rendering said highway crossing signal active when either of said sub-sections is occupied by a train approaching said highway crossing signal and rendering it inactive when such train has passed said junction irrespective of the direction of movement of such train.

14. In combination; a track section electrically isolated into a rear, an intermediate and a forward sub-section; means for applying a multiple impulse driven code to the exit end of the forward sub-section means at the junction between said intermediate and said forward sub-sections including a first code impulse following track relay connected across the entrance end of said forward sub-section and a track source connected through a back contact of said code impulse following track relay and across the exit end of said intermediate sub-section for repeating said driven code from said forward sub-section into said intermediate sub-section; a second code impulse following track relay connected across the entrance end of said intermediate sub-section; means for applying a code to the exit end of said rear sub-section in accordance with traffic conditions manifested by said second code impulse following track relay; a third code impulse following track relay connected across the rails at the entrance to said rear sub-section; a home relay controlled by said third code impulse following track relay; a highway crossing signal at the junction between the rear and the intermediate sub-sections; means at the entrance end of said rear sub-section for applying a short impulse code consisting of impulses shorter than the impulses of said driven code and which fall in the off periods of the driven code applied at the opposite end of said rear sub-section when said home relay is in its attracted condition and which is indiscriminately applied when said home relay is in its deenergized condition; a fourth code impulse responsive track relay at the exit end of said rear sub-section controlled by said short impulse code; and means including said second and said fourth code impulse following relay for controlling said highway crossing signal.

15. In combination; a track section electrically isolated into a rear, an intermediate and a forward sub-section; means for applying a multiple impulse driven code to the exit end of the forward sub-section; means at the junction between said intermediate and said forward subsections including a first code impulse following track relay connected across the entrance end of said forward sub-section and a track source connected through a back contact of said code impulse following track relay and across the exit end of said intermediate sub-section for repeating said driven code from said forward sub-section into said intermediate sub-section; a second code impulse following track relay connected across the entrance end of said intermediate sub-section; means for applying a code to the exit end of said rear sub-section inaccordance with traffic conditions manifested by said second code impulse following track relay; a third code impulse following track relay connected across the rails at the entrance to said rear subsection; a home relay controlled by said third code impulse following track relay; a highway crossing signal at the junction between the rear and the intermediate sub-sections; means at the entrance end of said rear sub-section for applying a short impulse code consisting of impulses shorter than the impulses of said driven code and which fall in the off periods of the driven code applied at the opposite end of said rear sub-section when said home relay is in its attracted condition and which is indiscriminately applied when said home relay is in its deenergized condition; a fourth code impulse responsive track relay at the exit end of said rear subsection controlled by said short impulse code; and means controlled by said second and said fourth code impulse following relay for rendering said highway crossing signal active when a train approaching said highway crossing signal occupies either said intermediate or said rear sub-section but which does not render said highway crossing signal active when approaching in said advance sub-section or when receding in any of said sub-sections.

THOMAS J. JUDGE.

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