US2349460A

US2349460A - Coded track circuit signaling system

Info

Publication number: US2349460A
Application number: US370186A
Authority: US
Inventors: Robert M Phinney; Oscar S Field
Original assignee: General Railway Signal Co
Current assignee: SPX Corp
Priority date: 1940-12-14
Filing date: 1940-12-14
Publication date: 1944-05-23
Anticipated expiration: 1961-05-23

Description

y 1944- R; M. PHINNEY ETAL 2,349,460

COD ED TRACK CIRCUIT SIGNALING SYSTEMS Filed Dec. 14, 1940 3 SheQts-Sheet 1 FIGuluAo Z m a I 2e INVENTORS Z56? THEIR ATTORNEY May 23, i 1944. 2,349,460

R. M. PHINNEY ETAL. CODED TRACK CIRCUIT SIGNALING SYSTEMS Filed Dec. 14, 1940 s Sheets-Sheet 2 INVENTORS THEIR ATTORNEY a y mi y 1944- R. M, PHINNEY ET'AL 2,349,460

CODED TgACK CIRCUIT SIGNALING SYSTEMS Fired D90. 14, 1940 3 Sheets-Sheet 3 1p L F M INVENTORS g; p wpmn e and 0.5. Field THEIR ATTORNEY Patented May 23, 1944 CODED TRACK CIRCUIT SIGNALING SYSTEM Robert M. Phinney and Oscar S. Field, Rochester, N. Y., assignors to General Railway Signal Company, Rochester, N. Y.

Application December 14, 1940, Serial No. 370,186

29 Claims.

The present invention relates to signaling systems of the absolute-permissiveblock type and more particularly to a duplex coded track circuit for such systems, and is an improvement over the system disclosed inthe prior application of Phinney, Ser. No. 362,636, filed October 2%, 1940, now Patent No. 2,272,581, dated Feb. 10, 1942.

By coded track circuit is meant a track circuit of the coded type wherein impulses of current are repeatedly applied to one end of'the track circuit and suitable code responsivev apparatus detects the code at the other end of such track circuit. By duplex coded track circuit is meant a track circuit in which codes may be applied at both ends of a section of track and code responsive apparatus may be connected at both ends thereof, wherein each code responsive apparatus only res-ponds to the codes applied by the code applying apparatus at the other end of the section. In order to control a signal in accordance with trafilc conditions in one or more blocks in advance, without the requirement of signal control line'wires, it is desirable to have the track relay or the code responsive apparatus located at that end of the block adjacent the signal, namely, at the entrance end of the track section or block. Obviously, if traffic is to move in both directions, as intne case in single track railroads, there should be a signal at each end of such track section for governing traffic into the section, consequently it becomes necessaryv or at least desirable, to have a track relay or code responsive means at each end of the track section to avoid the need of special control line wires.

Since traffic conditions in opposite directions from a particular track section may be different it becomes apparent that the codes transmitted in opposite directions through the same'track section may be diiierent. Also, when continuous inductive train control is employed it is. found necessary to apply the code to the exit end of the section for the particular direction in which the train is, moving, so that this code, may be detected b suitable receiving apparatus mounted on the front of the, locomotive and inductively related to the track rails. In view of these facts it is desirable to employ a duplex track circuit, so to speak, in which a track relay, or code responsive means, at each end of the track section controlled by energy applied at'the opposite end of such section is employed.

In the Phinney application above referred to suitable high frequency impulses, are superimposed on the transmission line,. these impulses operatingrelays at each end of each track section, 55,

which relays operate in synchronism and during on impulses connect the code applying apparatus at one end of the section and the code responsive apparatus at the "other end of such section, and during ofi periods connect the code creating apparatus at the other end to said track section and connect the track relay at the one end of such track section. In other words, the synchronously operated contacts allot time alternately to the two track circuits of one block, one of which has a track relay at one end connected to code applying apparatus at the other end, and the other of which has a track relay at the other end responsive to code creating apparatus located at said one end.

In accordance with the present invention it is proposed to construct a similar duplex track circuit but instead of employing synchronously operated contacts which are controlled over a transmission line or other line wires, it is proposed to employ individual timing apparatus, two such apparatuses being employed for each track circuit. These apparatuses allotting the use of the track rails alternately to two different track circuits for periods as determined by the timing apparatus inter-controlled through the track circuit. In the preferred embodiment. of the apparatus illustrating the present invention the apparatus, is so constructed that when the track circuit is occupied the apparatus conditions itself to permanently connect the track relay to the track rails. Obviously, this would occur at both ends of a block during the occupancy of such block and this would leave the track source at both ends. disconnected. As an auxiliary feature of. the present invention it is proposed to employ suitable apparatus for starting the timing apparatus into operation after suchoccupancy of such block.

Other objects, purposes, and. characteristic features of thepresent. invention will in part be described in the specification hereinafter and will in part be obvious. from. the accompanying drawingsin-which:

Figs. 1A and 1B, when. laid side by side, illustrate the apparatus applied to oneblock and the adjacent ends of, two. adjacent blocks of a preferred embodiment of, the present invention;

Fig. 2., illustrates a modified 'form of the present invention to show how alternating currentv may be intermittently applied. to the track rails in. code fashion tolbe. detected by suitable car-carried apparatus of a continuous. inductive train control y tem; and c Fig. 3 shows. a second modification including suitable means for applying alternating current to the track rails in code fashion for continuous inductive train control purposes.

Referring to Figs. 1A and 1B of the drawings which Show a railway track having rails l8 divided into sections or blocks by insulating joints H of which the block M and the adjacent ends of blocks L and N only have been illustrated. The section of track illustrated is a portion of a single track section extending from one passing siding to another preferably signaled by signals of the absolute-permissive-block type. Signals SI S3 govern West-bound trafiic into blocks L and M respectively, whereas signals S2 and S4 govern east-bound traffic into the blocks M and N, respectively. Since the apparatus associated with east-bound signals is almost identical to the apparatus associated with west-bound signals the apparatus associated with signal S2 will only be described specifically after which the difference between the apparatus associated with signal S2 and the apparatus associated with signal S3 will be specifically pointed out.

These signals S may be of any suitable construction, such as semaphore signals, search-light signals, or multiple aspect light signals, and for convenience three color multiple aspect light signals have been illustrated. These signals S comprise three light units designated R, Y and G, respectively, which when-lightedemit light beams of the colors of red, yellow and green, respectively, to signify danger, caution and clear, respectively. These signals are so controlled that the green lamp G is energized when two blocks directly in advance thereof are unoccupied so that the lamp Y is energized if only the second block of the first two blocks in advance is occupied and so that the red lamp R, is energized When the block at the entrance to which the signal is located is occupied. v I

The signal S2 is located at the entrance'end of the block M for east-bound trafiic. Adjacent this signal S2 and at'the entrance end to the block M for east-bound traffic the code following track relay CFT2 is connected across the track rails, but has included in series therewith the winding of the rocking relay RCR2 and the polar contact I2 of this rocking relay RCR2 assuming its righthand position. With this rocking relay RCR2 assuming its right-hand position and with the rocking relay RCR3 located at the east end of the block M also assuming its right-hand position the east-bound track circuit for the block M is intact. This track circuit may now have coded impulses applied thereto through the medium of the back contact I5 of the coding relay CFP4. These coded impulses are derived from the track battery TB3 and are of such polarity that the rocking relay RCRZ as well as the rocking relay RCR3 both of which are included in series in this track circuit maintain their polar contacts l2 and I2 in their right-hand position.

Intermittent picking up of the code following relay CFTZ causes intermittent energization of the track repeater relay TPZ, but since this track repeater relay TPZ is slow dropping it will remain continuously energized so long as either a '75 impulse per minute code or a 180 impulse per minute code is applied at the east endof this east-bound track circuit for block'M. The circuit for the track repeater relay TF2 includes a front contact I6 of the code following track relay CFTZ. In order to decode or decipher the codes received at the west end of the block M suitable decoding apparatus including the transformer and T2, the home relay H2 and the distant relay D2 are provided. The home relay H2 responds to both the 75 impulse per minute code and the 180 impulse per minute code and the distant relay D2 responds only to the 180 impulse per minute code. tap connected to one terminal ofa suitable source of current (indicated by an arrow point and a minus sign), such as a battery, and has its two end terminals alternately connected to the other terminal of this source of current (indicated by the arrow tail and a plus sign). Intermittent operation of the code following relay CFTZ through the medium of its contact 11. will primary winding of this transformer.

cause a low frequency pulsating current in the The effect of this intermittent energization of the primary winding of the transformer T2 in opposite directions is equivalent to the application of an alternating current of a frequency corresponding to the frequency of operation of the code following relay CFT2. In other words, if a .180 impulse per minute code is applied to the east end of the track section M the contact H of the code following relay CFTZ is picked up and dropped away times per minute and each time it is picked up the magnetic core of the transformer T2 is magnetized in one direction and during each dropping of the contact I1 this core is magnetized to an opposite polarity as a result of which alternating current of 180 cycles per minute is induced in the two secondary windings l8 and I9 of the transformer T2.

The alternating current voltage induced in the secondary winding I8 of the transformer T2 is rectified by the rectifying contact 20 also controlled by the code following relay CFT2 so that a direct current flows in the winding of the home relay H2 during intermittent operation of the code following relay CFT2, and such current is present irrespective of whether the particular code received is 180 impulse per minute code or is '75 impulse per minute code. In other words, the home relay H2 is energized when either a caution code of 75 impulses per minute or a clear code of 180 impulses per minute is received. The dis tant relay D2 is connected in series with the secondary winding I9 of the transformer T2 and has included in series therewith a condenser C2 which is of such capacity that it in combination with the inductive reactance of the circuit in which it is included resonates when a frequency of 180 impulses per minute is induced in the secondary winding I9 of this transformer T2. In other words, the distance relay D2 will respond to a 180 impulse per minute code but will not respond to a 75 impulse per minute code.

It is readily seen that during the reception of a 180 impulse per minute code at the entrance end to the block M that the home relay H2 and the distant relay D2 are both energized and that under this condition the green lamp G of the signal S2 is energized through a circuit including the front contact 22 of the relay H2 and front contact 23 of the relay D2, assuming there is a train in block L to close the approach lighting back contact 40 It will also be observed'that upon the reception of a 75 impulse per minute codethe caution or yellow lamp Y is energized because the home relay H2 is energized and the distant relay D2 is deenergized, and that the stop or red lamp R will be energized if the home relay H2 is deenergized. I

Referring for a moment to the apparatus assooiated with signal S4 it will be noted that the The transformer T2 has its midcoding contact I controlling the block to the rear is a contact associated with the coding relay CFP l. It should be noted that this coding relay CFP is controlled in accordance with the picked up or dropped away condition of the home relay H4 controlled in accordance with trafiic conditions in the block next in advance of the signal Si and the condition of the directional stick relay SR l associated with this same signal and also in accordance with the condition of the opposing directional stick relay SR3. More specifically, this coding relay CFP4 is normally, as illustrated, energized intermittently at the 180 impulse per minute rate through a circuit starting at one terminal of a suitable source of direct current, such as a battery, and passing through the coding contact I8BC4, through the front contact 2& of the home relay Ht, through the windings of the coding relay CFP l, and through the back contact 25 of the opposing directional stick relay SR3. Similarly, the coding relay CFPZ is energized by circuits starting from the terminal and passing through the coding contact I80C2, through the front contact 24 of the home relay H2, through the windings of the coding relay CFP2, and through the back contact 25 of the opposing directional stick relay SRi.

It is thus apparent that the code applied to the east end of the block M is of the 180 impulse per minute rate when the home relay H4 is energized but is of the '75 impulse per minute ratewhen this home relay is deenergized and the directional stick relay SR4 is energized. It is thus seen that with the two rocking relays RCR?! and R033 assuming their right-hand positions a code applied at the east end of the block M may be received at the west end of the block M. Similarly, when these rocking relays RCR2 and RCR3 assume their left-hand position a code may be applied at the west end of the block M through the medium of the coding contact 15 which may be received by the code following track relay CFTS at the east end of the block M.

Let us now observe how these rocking relays RCRZ and RCRt are alternately operated to the opposite polar position in synchronism when the block M is unoccupied. It will be noted that the rocking relay RCR2 is provided with a repeater RCRPZ and that this repeater relay RCRPZ is only energized when the rocking relay RCRZ assumes its right-hand polar position. This repeater rocking relay RCRPZ is exceedingly slow dropping and will remain in its attracted position for about three seconds after its winding has been deenergized. Similarly, the rocking relay RCRS is provided with a repeater rocking relay RCRP3 and this repeater relay RCRP3 is also slow dropping to substantially the same extent, that is, it will drop to its deenergized position about three seconds after its energizing winding has been deenergized. It should be noted that the repeater rocking relay RCRP2 is energized through a right-hand contact of the relay RCRZ, whereas the repeater rocking relay RCRP3 is energized through a circuit including the lefthand polar contact of the rocking relay RCR3. In other words, the repeater rocking relay RCRPZ is energized while the repeater rocking relay RCRP3 is deenergized and similarly the repeater rocking relay RCRPS is energized when the repeater rocking relay RCRP2 is deenergized. Since, however, both of these repeater rocking relays are very slow dropping they assume their energized position almost continuously.

Let us now observe how the rocking relays RCRZ and RCR3, which are connected in series, are alternately operated to opposite polar positions. It will be noted that the track batteries TB! and TB3 which may apply coded energy to the opposite ends of the block M are of opposite polarity insofar as the application of current through the relays RCR2 and RCR3 in series is concerned. Furthermore, the polarities of these track batteries TBZ and TB3 are such as to leave the rocking relays RCR2 in the position in which they were last operated to close the particular track circuit in which these track batteries are included. In other words, so long as rocking relay RCRPZ remains in its attracted position after its winding has been deenergized by the operation of the rocking relay RCRZ to its lefthand position it will allow the track rails of the block M to be energized from the track battery TBZ, and the polarity of the current applied from this track battery TBZ to the west-bound track circuit is such as to maintain the rocking relays RCRZ and RCR3 in their left-hand position. After the lapse of the timing period (determined by dropaway period of the rocking repeater relay RCRP2) has been consumed this relay RCRPZ assumes its deenergized position. Dropping of the contact 21 of this relay RCRP2 substitutes the battery B2 for the track battery T32, with the exception that the coding contact l5 is omitted. Since the battery B2 is of the opposite polarity from that of the battery TB?! the current flowing through the rocking relays RCRZ and RCR3 in series will be of such polarity as to operate the contacts of both of these relays to their right-hand position, in which they are shown. As these relays RCRZ and RCRS assume their right-hand position the code following track relay CFTZ is connected to the track rails at the west end of the block M, whereas the track battery T53 is connected to the track circuit at the east end of the block M and it may be pointed out that the track battery T33 applies energy of a polarity to maintain the rocking relays RCRZ and RCR3 in their righthand polar position.

Each signal location is provided with the usual directional stick relay and the directional stick relay SR2 is provided with a pick-up circuit including the back contact 38 of the opposing directional stick relay SRl, the back contact 3P of the opposing home relay Hi, the back contact 32 of the track repeater relay TF2, and the front contact 33 of the home relay H2, and is provided with a stick circuit including a stick contact 3 5 and the back contacts 35 and in multiple of the relays TF2 and H2, respectively.

It has already been pointed out how the eastbound track circuit and the west-bound track circuit of the block M are alternately completed through the rails of the block through the medium of the rocking relays RCR. It will be noted that a particular rocking repeater relay RCRP is only energized while that end of the block with which it is associated is the receiving end of the track circuit, namely, has its track relay connected to the track rails. It should now be observed that if the block M, for instance, is occupied by a train, that the end of the block which is the receiving end (code following track relay connected) will remain in that condition during occupancy of the block and even after the block is vacated. It is also apparent that the coding end of the block (track battery connected to the block) will become a receiving end (track relay connected to the block) after a short interval necessary to cause the associated relay RCRP to drop. If now the block becomes vacated the apparatus will, except for a special circuit, remain in a condition where the two rocking relays RCR are assuming out-of-correspondence positions. In order to cause the apparatus to again start into operation to render the two track circuits alternately available this special starting circuit has been provided at the east end of the block, and is provided for operating the rocking relay RCR at the east end to the right. Referring to the rocking relay RCR3 this special starting circuit may be traced from a terminal through the polar contact 38 of the relay RCR3 to the left, back contact 39 of the track repeater relay TF3 through the upper Winding of the rocking relay RCR3 to the other terminal of the same battery. This starting circuit will in combination with the circuit including the battery B3 and the bottom winding of relay RCR3 cause intermittent operation of this rocking relay RCR3 to its right-hand and its left-hand position, this relay RCR3 being operated to the right through the starting circuit just traced and being operated to the left each time that the associated rocking repeating relay RCRP3 is deenergized.

Since the coding contact I5 is free to apply a code to the track circuit through the front contact 27 of the relay RCRP3 and the right-hand contact :2 of the relay RCR3 the east end of the track circuit M will be coded during the presence of a train in the track section. Since, however, the west end of this block M is not provided with the starting circuit including the back contact 39 of the track repeater relay TP, there is no code applied to the west end of the block, except possibly for a three second interval, during the occupancy of such block. It may be pointed out at this time that the home relay H2 and the distant relay D2 are so slow dropping that they will not drop during the period of time when a code is being transmitted from the west end to the east end of the block M. Since the apparatus associated with the signals S4 and SI is the same as that associated with signals S2 and S3, respectively, these apparatuses have not been specifically described, but instead like parts have been assigned like reference characters with distinctive exponents and suiiixes.

Operation Under normal conditions, that is, when there are no trains present in any one of the blocks L, M and N or the blocks adjacent thereto, codes will be received alternately at opposite ends of each of these blocks, these codes being clear codes of 180 impulses per minute. These codes will be received alternately at opposite ends of the block for a period of say three seconds, and then will be absent for a period of three seconds at such end, it being of course understood that other time periods, such as a two second period, may be employed if desired. The home relays H and distant relays D are made so slow dropping that if they assume their energized position at the end of a track circuit period they will remain in their attracted position until the beginning of the next track circuit period. By track circuit period is meant the time that a track circuit for a particular direction is available. Under this normal condition all of the directional stick relays SR will remain in their retracted position. The two rocking relays RCR of any particular block will alternately both assume their right-hand position and then the left-hand position in synchronism for such time periods as are selected by the practitioner of the invention for the track circuit periods heretofore mentioned, which may be three second intervals. The rocking repeater relays RCRP will be alternately energized at opposite ends of a particular block, but each of these relays RCRP will not assume a deenergized position until the track circuit period has almost elapsed. In other words, these rocking repeater relays RCRP are substantially continuously in their attracted position, and will alternately assume their retracted position momentarily. As soon as one of these repeater rocking relays RCRP assumes its deenergized position its back contact 21 will apply a polarity of current to the track circuit to cause the rocking relay RCR to assume a polar position where the associated rocking repeating relay RCRP is again energized.

Let us now assume that a train is moving from left to right (namely an east-bound train) in the block L. The presence of this train in the block L will cause continuous deenergization of the code following track relay CFTI, because the rails of the block L are shunted by the wheels and axles of the train as a result of which the home relay HI and the distant relay Dl are both continuously deenergized. This condition of the relays associated with the signal SI will prevent the directional stick relay SRI from picking up. With the directional stick relay SRI in its retracted position and with the home relay HI deenergized the energizing circuit for the coding relay CFPI is broken, thereby leaving this coding relay continuously deenergized, as a result of which its back contact I5 applies non-interrupted direct current to the west end of the track circuit of block M so long as the polar contact I2 of the relay RCR2 remains in its lefthand position. This continuous direct current applied to the west end of the block M will of course cause deenergization of both of the relays H3 and D3 at the east end thereof, so that in a similar manner as just described continuous direct current will be applied to the west end of the block N. In other words, the entrance of a train into a single track section of the absolutepermissive-block signaling system of the present invention will cause all of the opposing signals to assume the stop position, thereby preventing an opposing train entering the same single track section.

Let us now assume that the east-bound train under consideration now occupying the block L passes the signa1 S2 and enters the block M. Since the directional stick relay SRI and the home relay HI were already deenergized the dropping of the track repeater relay TPZ, upon entrance of the train into the block M will cause its back contact 32 to complete the pick-up circuit heretofore traced for the directional stick relay SR2. This directional stick relay SR2 will be stuck up through its stick circm't including the back contact 35 of the track repeater relay 'I'P2, and after a short time interval a second stick circuit will be closed for the stick relay SR2 including the back contact 36 of the home relay H2.

By referrin to the apparatus associated with the signal S2 it will be seen that with the home relay H2 deenergized and with the directional stick relay SR2 energized that a coding circuit including front contact 26 of relay SR2 and back contact 24 of relay H2, applying 75 impulses per minute to the coding relay CFPZ, is closed for the next block in the rear. From this it is apparent that as soon as the rear end of the train under consideration has passed entirely out of the block L a caution code of 75 impulses per minute will be applied to the east end of the block L, as a result of which the signal governing the entrance of traffic into the west end of the block L (not shown) will assume its caution position. Also, with the relays H2 and D2 now both deenergized the red lamp R of the signal S2 will be illuminated to cause this signal S2 to assume the stop condition. This red lamp R will, however, not be actually energized unless there is a train in the block L, following the train in block M, to cause deenergization of the track repeater relay TPI and to cause its back contact 48 which is really an approach lighting contact, to be closed. In

this connection it may be pointed out that as soon as the first mentioned east-bound train left the block L the relays DI and HI assumed their energized position unless there was a second train following the first mentioned train so that in the event there is no following train the signal SI will assume its clear position for reasons already pointed out.

Let us now assume that the train under consideration which now occupies the block M proceeds into the block N. As the train in question enters the block N the pick-up circuit for the relay SR4 heretofore traced is closed. As soon as this relay SR4 is picked up, its stick circuit is closed for reasons heretofore given. With the relay SR4 energized and the relay H4 deenergized the coding relay CFP l will be energized through a circuit including the contacts 26 26 and the coding contact I504, as a result of which this coding relay CFPA is intermittently picked up at the '75 impulse per minute coding rate, which in turn results in the intermittent energization of the code -following track relay CFTZ at the '75 impulse per minute coding rate. For reasons already pointed out this 75 impulse per minute rate code is however only applied intermittently for three second intervals spaced by periods of about three second intervals. The reception of this code at the west end of the ously energized and causes the distant rela D2 to be continuously deenergized. With these relays H2 and D2 in their energized and deenergized condition, respectively, the yellow signal lamp Y will be illuminated as soon as an eastbound train enters the block L and closes the approach lighting contact Mi of the track repeater relay TPi. In the same manner as just explained a west-bound train will act upon the signals having an odd suflix in the same way as the east-' are common. to both of these track circuits and therefore only one track circuit can exist at one time. This precaution is necessary to prevent the track relay at a particular end of a block being operated from a track battery at the sam end of a block. It should also be understood that when a particular track circuit is either continuously energized by its track battery or is intermittently energized to characterize either the 75 impulse per minute code or the 180 impulse per minute code the current flowing therein is of such po- -15 block M causes the home relay 1-12 to be continularity as to maintain the two rocking relays RCR in their then polar position, but that upon termination of the interval of time allotted to that track circuit, namely, when the rocking repeating relay RCRP is deenergized that at least one impulse of direct current is applied to the track circuit from the auxiliary battery B and that this impulse is of reverse polarity. This reverse polarity impulse causes the rocking relays RCR of that block to assume the opposite polar position in which either continuous or coded current may be applied to the track rails of that block from the opposite end. Referring to the block M this block may have coded current applied to the west end thereof during the drop-away period of the relay RCRPZ and may have coded current applied to the east end thereof during the drop-away period of the rocking repeater relay RCRP3. It should also be remembered that the home and distant relays H and D respectively are sufiiciently slow dropping that they will not assume their dropped away position during the usual track circuit period which is from two to three seconds.

Fig. 2

It is sometimes desirable to provide a cab signal in the cab of the locomotive, by inductively detecting on the car the nature of the current flowing in the track rails directly ahead of the locomotive by continuous inductive train control apparatus well known in the art. The invention illustrated in Figs. 1A and 1B lend themselves to the application of continuous inductive train control providing that alternating current instead of direct current is applied to the track rails. In accordance with the present invention it is proposed to apply alternating current impulses during the off periods between the direct current impulses. The necessary circuit wiring to apply such alternating current has been illustrated in Fig. 2 of the drawings in which alternating current is applied to the track circuit through the front contact I5 it being remembered that direct current impulses are applied in Figs. 1A and 13 through the back point of this same contact. If, however, alternating current impulses are applied as illustrated in Fig. 2 it is desirable to employ the starting circuit including the contacts 38 and 39 of relays RCR andTP, respectively, hereto-fore described at both ends of the block instead of at the east end of the block only as illustrated in Figs. 1A and 113. If this starting circuit is employed at both ends of the block track circuit energy will be applied to both ends of the block substantially continuously during the occupancy of such block, these track circuit currents of course being'coded in accordance with traflic conditions in advance of the train irrespective of the direction in which the train occupying the block is moving.

Fig. 3

If for some reason or another it is undesirable to employ the starting circuits (including contacts 38 and 39) heretofore mentioned at both ends of each block, such starting circuit may be employed only at one end, as illustrated in Figs. 1A and 1B, and in this case the alternating current is applied to the track circuit through a separate branch including the back contact 42 of the coding relay CFPZ and the back contact 43 of the track repeater relay TPI, all as shown in Fig. 3 of the drawings. In this latter case the alternating current may be applied to the block only so long as that particular block is occupied by a train.

Car-carried apparatus The car-carried apparatus illustrated rather conventionally in Fig. 2 is symbolic of many types of car-carried apparatus used in train control systems of the continuous inductive type. As 11-,

lustrated two receivers R are preferably mounted on and in front of the locomotive, each of these receivers being inductively associated with one of the track rails ahead of the first wheel and axle of the train so that voltage is induced in each of these receivers in accordance with the alternating current flowing in the track rails. As shown these receivers R0 are so connected in series that the voltages induced therein are cumulative. The circuit in which the receivers are included also include a condenser Cc to tune this circuit to resonance for the particular alternating current frequency that is applied to the track rails from the alternating current source conventionally shown as a transformer Tt. This in-put circuit includes the receivers Re and condenser Co in series is connected to a suitable amplifier A, the out-put circuit of which is connected to a carcarried code following relay CR. This relay CR controls the home relay Ht and the distant relay Dt in exactly the same manner as the track relays CFT control the home relays H and D respectively, along the wayside. As the apparatus is illustrated there is one difference between the circuit for the distance relay Dt on the car and the distant relay D along the track, namely, that a full-wave rectifier Rt is employed in the carcarried apparatus to convert the 180 cycle per minute alternating current, to which frequency the tuned circuit for the relays D and Dt are tuned by a condenser, to direct current. In all other respects the car-carried apparatus and the trackway apparatus is the same and for this reason like reference characters have been applied to like parts except for the addition of an exponent or suflix t to the reference characters of the car-carried apparatus. It may be pointed out that a similar rectifier to that of the rectifier Rt illustrated in Fig. 2 may be used in connection with each of the distant relays D employed along the wayside. Since the car-carried apparatus functions substantially the same as the trackway apparatus it is believed unnecessary to describe the operation of the car-carried apparatus. It is to be understood that suitable brake control apparatus as well known in the art may be superimposed upon the car-carried apparatus illustrated so that the brakes may be automatically applied in the event the engineer does not himself properly control the train speed.

The applicants have thus shown and described a portion of an absolute-permissive-block signaling system employing a double track circuit, in which the track rails are rendered alternately available to each of two track circuits in the same block for periods of time long enough to transmit a complete code, as a result of which codes of two different code rates may be transmitted in opposite directions through the same block alternately for two or three second intervals so that signals at opposite ends of such block may distinctively indicate the conditions of traffic in advance. The applicants have also illustrated by several modifications how continuous inductive automatic cab signaling and train control may be added to the system illustrated in Figs. 1A and 13. Although the present invention has been rather specifically illustrated and described it should be understood that this has been resorted to to facilitate description of the underlying nature and principles of the invention and that this has not been resorted to to show the scope of the invention, and it should be understood that various changes, additions and modifications may be made to adapt the invention to the particular problem encountered in practicing the same, all Without departing from the spirit or scope of the invention except as demanded by the scope of the following claims.

What we claim as new is:

1. In a duplex track circuit of the coded type comprising, a section of track, code creating apparatus at each end of said section for creating codes each consisting of a plurality of impulses, code responsive apparatus at each end of said section distinctly responsive to such codes, double throw contacts at each end of said section operating in substantial synchronism to connect the code creating apparatus at one end of said section to the code responsive apparatus at the other end of said section through the rails of said section and connect the code creating apparatus at the other end of said section to the code responsive apparatus at said one end of said section through the rails of said section alternately, said double throw contacts assuming alternate positions at such a slow rate that complete codes each consisting of a plurality of impulses may be transmitted alternately in opposite directions through the rails of said section during such alternate connections, and means at the ends of said section controlled through the track rails of said section for operating said double throw contacts.

2. In a duplex track circuit of the coded type comprising, a section of track, code applying apparatus at each end of said section for creating distinctive multiple element codes, code responsive apparatus distinctively responsive to such codes at each end of said section, electro-magnetically operated means including double throw contacts at each end of said section operating in substantial synchronism to connect the code applying apparatus at one end to the code responsive apparatus at the other end of said section through the rails of said section and connect the code applying apparatus at the other end to the code responsive apparatus at said one end of said section through the rails of said section alternately, said double throw contacts assuming alternate positions at such a slow rate that a complete code comprising a plurality of impulses may be transmitted alternately in opposite directions through the rails of said section during such connection, and relays controlled through a circuit including the rails of said section for controlling said electro-magnetically operated means, said code responsive apparatus having slow acting operating characteristics such as to manifest a continuous reception of code in spite of its intermittent interruption due to such alternation.

3. In combination, a track section separated by insulating joints from the adjacent track, code creating apparatus for creating distinctive codes and code responsive apparatus distinctively responsive to such codes at each end of said section, double throw contacts at each end of said section operated substantially in synchronism, and circuit wires including said double-throw contacts to alternately connect the code creating and code responsive apparatuses to the ends of said section in such a manner that the code creating apparatus at one end is connected to the track section when the code responsive apparatus is connected to the other end, the timing of closure of said contacts being such that a complete code consisting of a plurality of impulses is transmitted first from one end to the other and then from the other to said one end of said track section, and relays and electro-magnetic means con" trolled through a circuit including the rails of said section for operating said double throw contacts.

4. In combination, a track section separated by insulating joints from the adjacent track; electro-magnetic means, code creating apparatus for creating distinctive codes and code responsive apparatus distinctively responsive to such codes at each end of said section; double throw contacts at each end of said section operated substantially in synchronism by said electro-magnetic means; circuit wires having included therein said double-throw contacts to alternately connect the code creating and code responsive apparatuses to the ends of said section in such a manner that the code creating apparatus at one end is connected to the track section when the code responsive apparatus is connected to the other end, the timing oi operation of said contacts being such that a complete code consisting of a plurality of impulses is transmitted first from one end to the other and then from the other to said one end of said track section, the said code responsive apparatus being so constructed that it will manifest continuous reception of a code in spite of the interruption during which a code is being transmitted to the opposite end; and a relay at each end of said section and controlled through a circuit including the rails of said section for controlling said electro-maghetic means and double throw contacts.

5. In ombination, a railway track divided into sections by insulating joints, code creating apparatus for creating distinctive codes and code responsive apparatus distinctively responsive to such codes at each end of eachtrack section, contacts at each end of each track section alternately connecting said code creating and said code responsive apparatus for that end to the rails of such track section, and electro-responsivc means for each of said contacts intermittently closing said contacts to connect said code creating apparatus to the particular end of the track section. with which it is associated while the code responsive apparatus is connected to the opposite end of such track section and to connect the code responsive apparatus to said particular end of each track section While the code creating means is connected to the opposite end of such track section. said electro-responsive means at opposite ends of such track section being interconnected through the medium of the track rails of said track section to operate substantially in synchronism and being operated at such a slow rate as to maintain each connection long enough to allow a complete code consisting of a plurality of impulses to be transmitted.

6. In combination, a railway track divided into sections by insulating joints, code creating apparatus for creating distinctive codes and code responsive apparatus distinctively responsive to such codes at each end of each track section, contacts at each end of each track section for alternately connecting said code creating and said code responsive apparatus to the rails at a particularend of such track section, and electroresponsive means operatively connected to each of said contacts for intermittently closing said contacts for the opposite ends of a particular track section in synchronism in such a manner that the code creating apparatus is connected to a particular end of each track section while the code responsive apparatus is connected to the opposite end of such track section and so that the code responsive apparatus is connected to said particular end of each track section while the code creating means is connected to the opposite end of such track section, said intermittent connections being made for suiilcient time periods to allow complete codes each constituting a plurality of impulses to be sent in opposite directions alternately, and said electro-responsive means at opposite ends of each track section being interconnected through the rails of such section in a manner to be actuated in synchronism.

'7. In combination, a railway track divided into sections by insulating joints, code creating apparatus for creating distinctive codes and code responsive apparatus distinctively responsive to such codes at each end of each track section, contacts at each end of each track section for alternately connecting said code creating and said code responsive apparatus at that end to the rails of such track section, and electro-responsive means for intermittently closing said contacts to connect the code creating apparatus at a particular end of such track section While the code responsive apparatus at the opposite end is connected to the rails of such track section and so that the code responsive apparatus is connected at said particular end of each track section while the code creating means is connected at the opposite end of such track section, said electro-responsive means being periodically actuated and causing said contacts to remain in closed positions for time periods long enough to allow a complete code consisting of a plurality of impulses to be sent in opposite directions alternately and said code responsive apparatus. being constructed to manifest the continuous reception of a code in spite of its intermittent nature, and said electro-responsive means at the two ends of such track section controlling each other through circuits including the rail of such track section.

8. In a double track circuit of the coded type comprising. a section of track. code creating apparatus for creating distinctive codes at each end of said section, code responsive apparatus distinctively responsive to such codes at each end of said section, and doubl throw contacts at each end of said section operating substantially in synchronism to connect the code creating apparatus at one end to the code responsive apparatus at the other end through the rails of said section and to connect the code creating apparatus at the other end to the code responsive apparatus at said one end through the rails of said section altemately, said double throw contacts assuming alternate positions at such a slow rate that a complete code comprising a plurality of impulses may be transmitted alternately in opposite directions through the rails of said section during such connection, and electro-responsive means at each end of said section controlling each other through the rails of said section and controlling the operation of said double throw contacts.

9. In a duplex track circuit of the coded type comprising, a section of track, code creating apparatus for creating distinctive codes at each end of said section, code responsive apparatus distinctively responsive to such codes at each end of said section, double throw contacts at each end of said section operating in substantial synchronism to connect the code creating apparatus at one end to the code responsive apparatus at the other end through the rails of said section and connect the code creating apparatus at the other end to the code responsive apparatus at said one end through the rails of said section alternately, electro-responsive means at each end of said section controlled through the rails of said section by the electro-responsive means at the other end of such section and for operating said double throw contacts, said double throw contacts assuming alternate positions at such a slow rate that a complete code comprising a plurality of impulses may be transmitted alternately in opposite directions through the rails of said section during such connection, and said code responsive apparatus having slow acting operating characteristics such as to manifest a continuous code in spite of its intermittent inter ruption due to such alternation.

10. In combination, a railway track divided into sections by insulating joints, code creating apparatus for creating distinctive codes and code responsive apparatus distinctively responsive to such codes at each end of each track section, contacts at each end of each track section for alternately connecting said code creating and said code responsive apparatus at that end to the rails of such track section, and electroresponsive means for intermittently closing said contacts to connect the code creating apparatus at a particular end of each track section While the code responsive apparatus is connected at the opposite end of such track section and to connect the code responsive apparatus at said particular end of each track section while the code creating means is connected at the opposite end of such track section, said contacts being intermittently closed for time periods sufiiciently long to allow complete codes each consisting of a plurality of impulses to be sent in opposite directions alternately, and mean for controlling the electro-responsive means at one end of each section through the rails of such section by the electro-responsive means at the opposite end of such section.

11. In combination, a railway track divided into sections by insulating joints, code creating apparatus for creating distinctive codes and code responsive apparatus distinctively responsive to such codes at each end of each track section,

contacts at each end of each track section for alternately connecting said code creating and said code responsive apparatus to the rails of such track section, electro-responsive means for intermittently closing said contacts in one position and then the other to connect the code creating apparatus to a particular end of each track section while the code responsive apparatus is connected to the opposite end of such track section and to connect the code responsive apparatus to said particular end of each track section while the code creating means is connected to the opposite end of such track section, and means for controlling the electro-responsive means at one end of each track section through the rails of such track section by the electroresponsive means at the other end of such section, said apparatuses being connected together for sufficient time periods to allow a complete code consisting of a plurality of impulses to be sent in opposite directions alternately, and said code responsive apparatus being constructed to manifest the continuous reception of a code in spite of its intermittent nature.

12. In an absolute-permissive-block signaling system, the combination with a railway track divided into blocks by insulating joints, a signal at each end of each block to govern the movement of traflic into such block from that end, code resposive means distinctively responsive to difierent codes and associated with each signal and governing such signal and governed through the rails of the block in advance of such signal by code creating means for creating such codes and located at the exit end of such block, and synchronously operated contacts at opposite ends of each block for alternately connecting the vcode creating means and the code responsive means across the rails at such end of the block in such synchronous relation with the operation of the contacts at the opposite end of the block that the code responsive means at the two ends of the block are alternately controlled by the code creating means at the opposite end of the block, said contacts operating at a sufiiciently slow rate to allow complete codes each consisting of a plurality of impulses to be sent alternately in opposite directions through the rails of such block, and two electro-responsive devices for each block one at each end thereof controlling the other through the rails of such block for operating said contacts for a particular block in substantial synchronism.

13. In an absolute-pernflssive-block signaling system, the combination with a railway track divided into blocks by insulating joints, a signal at each end of each block to govern the movement of traffic into such block from that end, code responsive means distinctively responsive to difierent codes and associated with each signal and governing the same and governed through the rails of the block in advance of the signal by code creating means for creating such codes and located at the exit end of such block, and

synchronously operated contacts at opposite ends of each block for alternately connecting the code creating means and the code responsive means across the rails at such end of the block in such synchronous relation with the operation of the contacts at the opposite end of the block that the code responsive means at the two ends of the block are alternately controlled by the code creating means at the opposite end of the block, electro-responsive means at each end of each block controlling each other through the rails of such block and controlling the contacts for its end of such block, said contacts operating at a sufiiciently slow rate to allow complete codes each consisting of a plurality of impulses to be sent alternately in opposite directions through the rails of such block, and said code responsive means being constructed to manifest the continuous reception of a code in spite of its intermittent reception due to such alternate directional transmission.

14. In an absolute-permissive-block cab signaling system, the combination with a railway track divided by insulating joints into blocks, code responsive means distinctively responsive to different codes at each end of each block gov- -erned through the rails of such block by code creating means for creating such codes located at the opposite end of the block, synchronously operated contacts at the two ends of each block flor alternately connecting the code creating means and the code responsive means across the rails at its end of the block in such synchronous relation with the operation. of the contacts at! the sive means at the two ends of the block are each alternately controlled by thecode creating means at the opposite end of the block, electro-responsive means at each end of each block each controlled through the rails of such block by the electro-responsive means at the opposite end of the block for controlling the contacts at the two ends of such block, said contacts operating sufficiently slow to allow a complete code consisting of a plurality of impulses to be transmitted during each closure of such contacts, means for controlling each code creating means at an exit end of a block by the code responsive means at the adjacent end of the block next in advance, and car-carried apparatus including a cab signal controlled by the coded current flowing in the track rails in advance of the vehicle carrying such car-carried apparatus.

15. In an absolute-permissive-block cab signaling system, the combination with a railway track divided by insulating joints into blocks, code responsive means distinctively responsive to different codes at each end of each block governed through the rails of such block by code creating means for creating such codes located at the opposite end of the block, said code responsive means being constructed to continuously manifest a code even though the code is intermittently absent for a time period to allow a complete code comprising a plurality of impulses to be transmitted in the opposite direction, synchronously operated contacts at the two ends of each block for alternately connecting the code creating means and the code responsive means across the rails at its end of the block in such synchronous relation with the operation of the contacts at the opposite end of the block that the code responsive means at the two ends of the block are alternately controlled by the code creating means at the opposite end of the block, said contacts operating sufficiently slow to allow a complete code consisting of a plurality of impulses to be transmitted during each closure of such contacts, means for controlling each code creating means at an exit end of a block by the code responsive means at the adjacent end of the block next in advance, electro-responsive means at each end of each block controlling each other through circuits including the rails of such block for controlling the contacts at the ends of such block in substantial synchronism, and car-car-' ried apparatus including a cab signal controlled by the coded current flowing in the track rails in advance of the vehicle carrying such carcarried' apparatus.

16. In an absolute-permissive-block cab signaling system, the combination with a railway track divided by insulating joints into blocks, code responsive means distinctively responsive to difierent codes at each endof each block governed through the rails of such block by code creating means for creating such codes located at the opposite end of the block, said code responsive means being constructed to continuously manifest a code even though the code is intermittently absent for a time period to allow a complete code comprising a plurality of impulses to be transmitted in thev opposite direction through the rails of the block, synchronously operated contacts at the two ends of each block for alternately connecting the code creating means and the code responsive means across the rails at its end of the block in such syn- Vii chronous relation with the operation of the contacts at the opposite end of the block that the code responsive means at the two ends of the block are alternately controlled by the code creating means at the opposite end of the block, said contacts operating sufiiciently slow to allow a complete code consisting of a plurality of impulses to be transmitted during each closure of such contacts, electro-responsive means at each end of each block controlled by the electro-responsive means at the other end of such block through the rails of such block and controlling said contacts for that end of such block, means for controlling each code creating means at the exit end of a block by the code responsive means at the adjacent end of'the block next in advance, car-carried apparatus including a cab signal controlled by the coded current flowing in the track rails in advance of the vehicle carrying such car-carried apparatus, and means effective under danger traffic conditions to apply the brakes of the vehicle.

17'. In an absolute-permissive-block signaling system; the combination with a single track section divided into blocks by insulating joints; a track relay for each end of each block; a track source for each end of each block; synchronously operated contacts at each end of each block for alternately connecting the track relay and the track source across the rails at that endof the block in such synchronous relation with the operation of the contacts at the opposite end of such block that two track circuits, cachincluding a track source at one end and a track relay at the other, for such block are alternately established for periods of time long enough to allow a code consisting of a plurality of impulses to be transmitted, electro-responsive means for each of said synchronously operated contacts for controlling the same each controlled through the rails of the block by the electro-responsive means located at the opposite end of such block, code responsive means for each track relay controlled by such track relay in accordance with the code received by such track relay, a directional stick relay associated with each code responsive means, a pick-up circuit for each stick relay closed momentarily when a train enters the block at the entrance to which such stick relay is located, a stick circuit on each stick relay closed only when the block at the entrance to which such stick relay is located is occupied, and coding means associated with each track source for coding the current supplied to the track circuit from said source in accordance with the conditions of the associated stick relay and the code responsive means associated with the adjacent end of the adjacent block.

18. In combination, a section of railway track, a track source and a track relay for each end of said track section, an electro-responsive device for each end of said track section each having a contact which if in one position connects the associated track source across the track rails and if in another position connects the associated track relay across the track rails, and means to cause each electro-responsive device to control the other through the medium of the track rails of said section and to control said contacts so that two track circuits one including a track relay at one end and a track source at the other and the other including a track source at one end and a track relay at the other are alternately established for periods of time long enough to transmit any one of a plurality of complete dis- 7 tinctive codes each comprising a plurality of impulses.

19. In combination, a section of railway track, a track source and a track relay for each end of said track section, an electro-responsive device for each end of said track section each having a contact which if'in one position connects the associated track source across the track rails and if in another position connects the associated track relay across the track rails, and means to cause each electro-responsive device to control the other through the medium of the track rails of said section and to control said contacts'so that two track circuits one including a track relay at one end and a track source at the other and the other including a track source at one end and a track relay at the other are alternately established for periods of time long enough to transmit any one of a plurality of complete distinctive codes each comprising a plurality of impulses and including means to cause the contacts of both of said electro-responsive devices to disconnect their respective track sources from the track rails upon occupancy of said track section, and other means responsive to occupancy of said track section and efiective after a period of delay to operate one of said electro-responsive devices to a position to reconnect its associated track source to said track section to thereby reestablish one of said track circuits which is then efiective to detect when said track section becomes unoccupied.

20. In combination, a section of railway track, a track source and a track relay for each end of said track section, an electro-responsive device for each end of said track section each having a contact which if in one position connects the associated track source across the track rails and if in another position connects the associated track relay across the track rails, means controlled by each electro-responsive device to control the other electro-responsive device through the medium of the track rails of said section and by current derived from a source at the opposite end of said section to control said electro-responsive devices and in turn their contacts so that two track circuits one including a track relay at one end and a track source at the other and the other including a track source at one end and a track relay at the other are alternately established for periods of time long enough to transmit any one of a plurality of complete distinctive codes each comprising a plurality of impulses and including means to operate said electro-responsive devices to positions to disconnect both of said track sources from the track rails upon occupancy of said track section whereby said electro-responsive devices cannot control each other upon unoccupancy of said section, and other means-responsive to occupancy of said track section and effective after a period of delay to reconnect one of said track sources to the rails of said track I section to allow control of the electro-responsive device at the other end of said track section as soon as said track section becomes unoccupied.

21. In combination, a section of railway track, a track source and a track relay for each end of said track section, an electro-responsive device for each end of said track section each having a contact which if in one position connects the associated track source across the track rails and if in another position connects the associated track relay across the track rails, means to cause each electro-responsive device to control the other through the medium of the track rails of said section and to control said contacts so that two. track circuits one including a track relay at one end and a track source at the other and the other including a track source at one end and a track relay at the other are alternately established for periods of time each long enough to transmit a complete code comprising a plurality of impulses, code creating means at each end of said section for intermittently disconnecting said source to create distinctive codes, code responsive means at each end of said section controlled by the track relay at that end distinctively responsive to said codes, and a signal at each end of said section controlled by the associated code responsive means and governing the movement of trafiic over a track junction including that end of said section.

22. In combination, a section of railway track, a track source and a track relay for each end of said track section, an electro-responsive device for each end of said track section each having a contact which if in one position connects theassociated track source across the track rails and if in another position connects the associated track relay across the track rails, means to cause each electro-responsive device to control the other through the medium of the track rails of said section and to control said contacts so that two track circuits one including a track relay at one end and a track source at theother and the other including a track source at one end and a track relay at the other are alternately established for periods of time each long enough to transmit any one of a plurality of complete distinctive codes each comprising a plurality of impulses, a distinctive source of current at each end of said section, said means including a slow dropping relay energized by a circuit closed only when the associated electro-responsive device is in a position to connect the associated track relay to the track rails, which slow dropping relay when it assumes its deenergized position connects sociated track source across the track rails at that end of said section and if in another position connects the associated track relay across the track rails at that end of said section, means to cause each electro-responsive device to control the other through cluding the track rails of said section and to control said contacts so that two track-circuits one including a track relay at one end and a track source at the other end and the other including a track source at one end and a track relay'at the other are alternately established for periods of time long enough to transmit any one of a plurality of complete distinctive codes each comprising a plurality of impulses, a distinctive source of current at each end of said track section, said means including a slow-dropping relay energized by a circuit including a contact of the associated electro-responsive' device closed only when the associated electro-responsive device is in a position to connect the to the track rails, which slow-dropping relay when it assumes its deenergized position connects the medium of a circuit inassociated track relay electro-responsive device ,1 at :the gopposite end ,of saidsection toa position to open:the.circuit:'for energizing -.the slow-dropping relay :atsuc-h opposite ,end of said section.

24. vIn :a single .track railway signaling system for governing the :movement oftrafficiin vbotndirections over the same :track comprising, .a sec.-

tion of track isolated from adjacent trackhy' insulating joints; .atrack source of :current,:a track relay, a timing device, a special sourcesof-current at each end ofsaid section andran 'electro-responsive device at each .end of said 'section; and goincuit means at each endofsaid section reflective when the associated electro-responsive device assumes one positionto connct the associated track relay to the track rails and to close an energizing circuit for said timing device, effective when the electro-responsive device assumes another position with said timing device assuming its active position to connect said track source to the track rails and efiective when said electro-responsive device assumes such other position with said timing device assuming its inactive position to connect said special source of current to the track rails to actuate said electro-responsive device at the opposite end of said section to said other position through a circuit including the track rails of said section; and a signal at each end of said section for governing the movement of traffic into that end and controlled by the associated track relay.

25. In a single track railway signaling system for governing the movement of traffic in both directions over the same track comprising, a section of track isolated from adjacent track by insulating joints; a track source of current, a track relay, a timing device, a special source of current at each end of said section and an electro responsive device at each end of said section; and circuit means at each end of said section effective when the associated electro-responsive device assumes one position to connect the associated track relay to the track rails at that end of said section and to close an energizing circuit for said timing device, effective When the electro-responsive device assumes another position with said timing device assuming its active position to connect said track source to the track rails at that end of said section and efiective when said electro-responsive device assumes such other position with said timing device assuming its inactive position to connect saidspecial source of current to the track rails to actuate said electro-responsive device at the opposite end of said section to said other position through a circuit including the track rails of said section; code creating means at each end of said section including an intermittently closed coding contact included in series with the associated track source for creating distinctive multiple impulse codes; code-responsive means at each end of said track section each controlled by the associated track relay and distinctively responsive to such codes; and a signal at each end of said section for governing the movement of traffic into that end of said section and controlled by the associated code-responsive means.

26. In a single track railway signaling system for governing the movement of trafiic in both directions over the same track comprising, a section of track isolated from adjacent track by insulating joints; a track source of current, a track relay, a timing device, a special source of current at each end of said section and an electro-responsive'device at each end of said section; and circuit means :at each end of said 1 section effective when the associated ielectro-sresponsive.device assumes .one position to connect the associated track relayto the track :rails and to close an energizi-ng circuit .for said timing device, effective whenthe electro-responsive device assumes another position vwith-said timing device assuming its active position to connect said track source to the track rails and efiective when said electroresponsive device assumes such other position with-saidtimingdevice assumingits inactive po- SltiOIlitO connect said specialsource of current to the :track rails to actuate said electro-responsive deviceat .that end of said section torsaid one position andalsoactuate said electro-responsive device atthe oppoiste end of said section to said other position through a circuit including the track rails of said section.

27. In a single track railway signaling system for governing the movement of traffic in both directions over the same track comprising, a section of track isolated from adjacent track by insulating joints; a track source of current, a track relay, a timing device, a special source of current and an electro-responsive device at each end of said section; and circuit means at each.

end of said section effective when the associated electro-responsive device assumes one position to connect the associated track relay to the track rails and t close an energizing circuit for said timing device, effective when the electro-responsive device assumes another position with said timing device assuming its active position to connect said track source to the track rails and effective when said electro-responsive device as sumes such other position with said timing device assuming its inactive position to connect said special source of current to the track rails to actuate said electro-responsive device at that end of said section to said one position and actuate said electro-responsive device at the opposite end of said section to said other position through a circuit including the track rails of said section; special means associated only with the electro-responsive device at one end of said section to actuate such electro-responsive means to its said other position including a contact 'closed only when such electro-responsive device assumes its said one position with the track relay at the said one end assuming its deenergized position for a prolonged period of time; and a signal at each end of said section for governing the movement of trafiic into that end of said section and controlled by the associated track relay.

28. In a single track railway signaling system for governing the movement of traffic in both directions over the same track comprising, a section of track isolated from adjacent track by insulating joints; code creating means for creating distinctive codes, code responsive means distinctively responsive to such codes and electroresponsive contact actuating means having contacts associated therewith at each end of said section; means including the track rails-of said section for causing the electro-responsive contact actuating means at opposite ends of said section to control each other to cause synchronous intermittent actuation of their respective contacts at such a slow rate that a complete code consisting of a plurality of impulses and created by said code creating means may be transmitted during a stationary condition of said contacts during such intermittent actuation; circuit means including the said contacts at both ends of said section to alternately establish two track circuits one including the code creating means at one end of said section and the code responsive means at the other end and the other including code creating means at said other end of said section and the code responsive means at said one end; and signals controlled by said code responsive means.

29. In combination with a section of track divided from adjacent track by insulating joints, of a multiple impulse code creating apparatus at each end of said section for creating distinctive codes, multiple impulse code receiving apparatus at each end of said section distinctively responsive to such codes, selecting means at each end of said section for connecting either the at such opposite end and being controlled to an-' other position by its associated timing means.

ROBERT M. PHINNEY. OSCAR. S. FIELD.