US2277478A

US2277478A - Railway traffic controlling apparatus

Info

Publication number: US2277478A
Application number: US380416A
Authority: US
Inventors: Ralph K Crooks
Original assignee: Union Switch and Signal Inc
Current assignee: Hitachi Rail STS USA Inc
Priority date: 1941-02-25
Filing date: 1941-02-25
Publication date: 1942-03-24
Anticipated expiration: 1959-03-24

Description

R. K. CROOKS RAILWAY TRAFFI C GONTROLL I NG APPARATUS March 24, 1942.

4 Sheets-Sheet" l HIS ATTORNEY Filed Feb. 25, 1941 March 24, 1942.

R. K. CROOKS.

RAILWAY TRAFFIC CONTROLLING APPARATUS Filed Feb. 25, 1941 4 Shets-Sheet 2 .AAM

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AAAAA vvvvv INVENTOR Halpjflraokr. BY

HIS ATTORNEY March 24, 1942. R, K, CROOKS RAILWAY TRAFFIC CONTROLLING APPARATUS Filed Feb 25, 1941 4 sheets-sheets am Paw CA LQN \mwm EN XWMMW EEBSQ Q h L wm INVENTOR Hal p12 POOliJ.

MS ATTO RN EY March 24', 1942. K. CROOKS RAILWAY TRAFFIC CONTROLLING APPARATUS Filed Feb. 25, 1941 4 Sheets-Sheet 4 1' IINVENTOR 15([5 ATTORNEY Patented Mar. 24, 1942 v pmrso STATES PATENT OFFICE RAILWAY TRAFFIC CONTROLLING APPARATUS Ralph K. Crooks, Sharpsburg, PaL, assignorto The Union Switch & Signal Company, Swissvale, Pa., a corporation oi Pennsylvania Application February 25, 1941, Serial No. 380,416

18 Claims.

a plurality of characteristics in addition to the rate of interruption, a distinctive characteristic Several different code rates are required when several diilerent signal indications are needed. A distinctive code rate is prescribed for each of several dilferent traffic conditionsand the receiving apparatus includes decoding devices selectively responsive to these different code rates so as to establish a distinctive control for each such traiiic condition. Since a code rate is effected by interrupting the current a predetermined number of times per minute and an electromotive force of a frequency corresponding to the code rate is used, tuned circuit arrangements are provided as the decoding means, each such circuit arrangement being tuned for response to a frequency corresponding to a respective code. Hence when several diiferent code rates are used, several different tuned circuits are required and when it is necessary to provide an additional indication an additional code rate is provided with an additional tuned circuit.

In view of such code signaling conditions, a feature of my invention is the provision in railway trafiic controlling apparatus of novel means wherewith a code more distinctive in character than the usual frequency code is used and wherewith false operation due to an intermittent open circuit condition is avoided. 1

Another feature of my invention is the provision of railway traffic controlling apparatus incorporating novel and improved means for a simple code signal system for railways.

Again, a feature of my invention is the provision of novel railway traffic controlling apparatus for a four-indication cab signal system and which apparatus avoids the necessity of resonant decoding equipment. I

Still another feature of my invention is the provision of novel railway traflic controlling apparatus wherewith one or two additional signal indications can be added to the present standard frequency code signal system without requiring additional -code rates.

The above features of my invention, as well as other advantages which will become apparent as the specification progresses,are attained according to my invention by providing a code forming means which impresses upon a periodically interrupted alternating current any one of being efiected for each of a plurality of diiTerent trafiic conditions. Under onetrafiic condition 4 this special .code forming means causes in a periodically interrupted alternating current the amplitude of the current at the start of each on period to be relatively small and to progressively increase to a relatively high value at the end of the on period, the current dying away abruptly at theend of the on period when the circuit is interrupted. Under another traflic condition, the code forming means causes the alternating current to abruptly rise to a relatively high amplitude at the start of each on period and to gradually diminish in amplitude during the on period until it is of a relativelylow value when the circuit is interrupted at the end of the on period. That is to say, under one traflic condition the alternating current has an increasing amplitude code characteristic, and under a second traflic condition it has a decreasing amplitude code characteristic. A slow acting three-position polar relay'is controlled by such coded current and this relay is held at one extreme position when the first mentioned characteristic prevails,

is held at the other extreme position when the second code characteristic prevails and is held at its biased third position when the alternating current is not provided with either of such-code characteristics. This code responsive relay is used to govern the operating circuits of a multiple indication cab signal or train control device.

Additional indications are added to the present frequency code system by incorporating this special code forming means into the usual code transmitting apparatus of the present frequency code system, with the result that the special code forming means impresses upon a selected code rate the distinctive code characteristics described I shall describe two forms of apparatus embodying my invention, and shall then point out the novel features thereof in claims.

In the accompanying drawings, Fig. 1 is a diagrammatic view showing one form of apparatus embodying my invention when used for a threeblock four-indication cab signal system. Figs. 2, 3, c, 5, 6 and 7 are diagrams illustrating the characteristics of the coded current and electromotive forces effected by the apparatus of Fig. 1. Figs. 8a and 8b and 9 are diagrammatic views showing one form of apparatus embodying my invention for obtaining two additional indications in a frequency code cab signal system, Figs. 8a and 8b whentaken together with Fig. 8a placed at the left disclosing the trackway portion of the apparatus and Fig. 9 disclosing the train carried portion of the apparatus.

In each of the several views like reference characters are used to designate similar parts.

Referring to Fig. 1, the reference characters la and lb designate the track rails of a stretch of railway over which traffic normally moves in the direction indicated by an arrow and which rails are formed by the usual insulated rail joints with a series of consecutive track sections of which sections only the one full section D-E and the adjoining ends of the adjacent sections are shown for the sake of simplicity since these are sufiicient for a full understanding of my invention. track circuit including a source of alternating current connected across the rails at the exit end of the section and a track relay connected across therails at the entrance end of the section. The immediate source of current for'the track circuit of section D- -E is a track transformer TD whose secondary winding 2 is connected across the rails over wires 3 and 4 and whose primary winding 5 is supplied with alternating current from any convenient source such as a generator whose terminals are indicated at BX and CK.

Such alternating current is coded in a manner to be made clear presently. I

The reference character DTR designates a track relay for the track circuit of the section next in advance of section D-E. Relay DTR is a two element alternating current relay having winding 6 of one element connected across the rails over wires 1 and 8, and winding 9 of the second element of the relay connected directly to the BX and CK terminals of the source of alternating current. Relay DTR is of the type responsive to the relative polarity of the currents supplied to its two windings and is provided with two contact members In and H operable to a normal right-hand position when windings 6 and 9 are energized by currents of normal relative polarity and operable to a reverse left-hand position when the relative polarity of the current I supplied to the track winding 6 is reversed. When either one or both windings Band 9 are deenergized the contact members and H occupy a biased mid position. Track relay DTR controls a repeater relay DPR over an obvious circuit including contact member ID in engagement with either its normal contact I! or its reverse contact l3. Repeater relay DPR is preferably provided with slow release characteristics and is used to control the connections to primary winding of transformer TD, the arrangement being such that when repeater relay DPR is picked up a normal connection is completed for primary winding 5 and when the relay is released a reverse connection is provided for primary winding 5.

Each track section is provided with a to alternately engage a front contact I 5 and a back contact 16 as long as the winding'of the coder is effectively supplied with current. The rate at which contact member I4 is operated is preselected and as an aid to the understanding of the apparatus embodying my invention, I shall assume contact member I4 is operated at'the rate of '75 times per minute, although it is to be understood that any other convenient rate may be selected if desired.

The apparatus also includes a code forming means for determining the code characteristics of the current supplied to the track circuit of section D-E. This code forming means comprises a saturable reactor TC, another reactor RC and a full wave rectifier RF. When track relay DTR is held at its normal right-hand position and repeater relay JDPR is picked up, current is supplied to primary winding 5 of track transformer TD by a circuit which can be traced from terminal BX of the source of alternating current over front contact l4--l5 of coder CT, winding ll of saturable reactor TC, front contact l8 of relay DPR, primary winding 5 of transformer TD, a second front contact 19 of relay DPR and to terminal CX of the current source. The amplitude'of the current flowing in the circuit is determined in part by the impedance of winding ll of saturable reactor TC. The impedance of primary winding I! of reactor TC is governed by the flux condition of the magnetic core of the reactor and is high when no direct current flows in secondary winding 20 of the reactor to cause magnetic saturation of the core structure of the reactor and is low when direct current flows in secondary winding 20 to set up a saturated magnetic condition of the reactor core. With track relay D TR occupying'its normal position, a circuit is prepared by which rectified current is supplied to secondary winding 20 of reactor TC, each time front contact I4I5 of that at the end of such on period magnetic saturation is-effected for reactor TO. The impedance of primary winding I! of reactor TC is therefore relatively high at the start of each on. period and progressively decreases to a relatively low value at the end of the on period due to the change effected in the magnetic condition of the core of reactor TC. Consequently, the amplitude of the current supplied to primary winding 5 of I track transformer TD is relatively low at the D-E includes a code transmitter'or coder CT which is shown as ,being of the well-known relay type provided with a contact member l4 operable start of the on period and progressively increases to a relatively high value at the end of the on period. Hence, in turn, the amplitude of the current supplied to the track circuit from secondary winding 2 of track transformer TD is relatively low at the start of the on period and progressively increases to a relatively high value at the end of the on period. When coder contact I4l5 is operated at the end of an on period to interrupt the circuit for primary winding 5 the current abruptly dies away in the track circuit. Also, the rectified current supplied to secondary winding 20 is interrupted and the magnetic flux of reactorTC dies away during the oil code period with the result the above described operation is repeated each on period of the current. In Fig.2 there is illustrated this code characteristic impressed upon the track circuit current for section DE when the track relay DTR for the section next in advance occupies its normal position, the amplitude of the current being relatively low at the start of each on period, progressively increasing to a relatively high value at the end of the on period and abruptly dying away at the start of the off period. In other words, Fig. 2 illustrates the increasing amplitude code characteristic impressed upon the alternating current during each on'code period.

When track relay DTR occupies its reverse left-hand position, repeater relay DPR is picked up as before and current is supplied to the circuit including primary winding 5 of transformer TD the same as before. Rectified current is now supplied to secondary winding 20 over a circuit including terminal BX, back contact Ml6 oi' coder CT, wire 23, reverse contact I l--24 of relay DTR and thence as previously traced. This time magnetic saturation is effected for reactor TC during the off period of the code, and the circuit for secondary winding 20 is interrupted during the on period so that the magnetic saturation gradually decreases during each on period. It

.follows that the impedance of primary winding ll of reactor CT is low at the start of the on code period because of the magnetic saturation of reactor TC an the impedance of winding ll gradually increases to its high value at the end of the on period. Consequently, the current supplied to the track circuit through track transformer TD is abruptly started at a relatively high value, progressively decreases to a low value at the end of the on period and then dies away from the low value at the start of the off period. In Fig. 4 there is illustrated this decreasing amplitude characteristic impressed upon the track circuit current of section DE when track relay DTR for the section next in advance occupies its reverse position. In other words, Fig. 4 illustrates the decreasing amplitude code characteristic impressed upon the alternating current each on code period.

When track relay DTR is deenergized and its contact members l and II occupy the biased midposition, repeater relay DPR is deenergized and released and the connections to the primary winding 5 of track transformer 'I'D are pole changed at

back contacts

25 and 26 of relay DPR as will be readily understood by an inspection of Fig. 1. Current is now supplied to primary winding 5 of transformer TD over a circuit including terminal BX, back contact I4I6 of coder CT, wire 23, resistor 21, back contact 26 of relay DPR, primary winding 5 of transformer TD, back contact 25 of relay DPR and terminal CX. Since the impedance of this circuit remains substantially the same, the amplitude of the current flowing therein is substantially uniform throughout the entire on period which in this case is during the period back contact I l-l6 of the coder is closed. This current has a substantially uniform amplitude characteristic'as compared with the currents of the previous two conditions. In Fig. 6 there is illustrated this substantially uniform code characteristic for the track circuit current of section DE when track relay DTR for the section next in advance is released.

code characteristics are impressed upon the track circuit current of section D--E according to three different traflic conditions in advance, namely, a first traiiic condition which eiiects the normal position of track relay DTR causes an increasing amplitude code characteristic for the track circuit current of section DE, 'a second traflic condition which effects the reverse posi-- tion of relay DTR causes a decreasing amplitude code characteristic for the track circuit current of section DE, and a third traflic condition which causes relay DTR to be released causes a substantially uniform amplitude code characteristic for the track circuit current of section DE. It is to be observed that the code rate for the track circuit current is the same under each condition. Furthermore, it is to be pointed out that when repeater relay DPR' is picked up the current supplied to the track circuit of section DE. is of normal relative polarity and when relay DPR, is released the current is of reverse relative polarity.

Track relay ETR for section DE is a two element alternating current relay, the same as relay DTR for the section inadvance of section DE. Winding 28 of one element of relay ETR is connected across the rails of section DE, and winding 29 of the second element of the relay is energized directly from. the terminals BX and CX of the current source. Consequently when section DE is unoccupied, that is, when a train shown conventionally at TV does not occupy the section, relay ETR is energized to position its contact members 30 and 3| at the normal right-hand position when current of normal relative polarity is supplied to the track circuit, is energized to position contact members 30 and 3| at the reverse left-hand position when current of reverse relative polarity is supplied to the track circuit and is deenergized so that contact members 30 and 3| occupy. their biased midposition when train TV occupies the section to shunt the track circuit. It is to be pointed out track relays DTR and ETR are inherently slow in their action due to the type of relay and do not follow the on and ofi periods of the coded current supplied to the respective circuits. That is, each relay DTR and ETR remains in the position to which it is moved during an on code period during the off period of the code. If found necessary the track relays DTR and ETR may be provided with additional slow acting means, several of such means being well-known in the art. Track relay ETR is associated with code forming means which is the same as that associated with track relay DTR and relay ETR and its associated apparatus govern the supply of coded current to the track circuit for the section next in the rear of section DE in the same manner that relay DTR and its associated apparatus govern the supply of coded current to the track circuit for section D-'--E. It is to be observed that track relays DTR and ETR are not responsive in any distinctive manner to the increasing and decreasing amplitude characteristics impressed upon the coded current, but that such characteristics are employed for governing cooperating train carried apparatus as will now be described.

Still referring to Fig. 1, the train TV has mounted thereon two

inductors

32 and 33 in inductiverelationto rails Ia and lb, respectively, and

inductors

32 and 33 are connected together in the well-known manner so that electromotive It'is to be seen therefore that three different" forces induced therein duringthe on code period of the track circuit current add their effects.

Inductors

32 and 33 are included in a receiving circuit in series with a condenser 35 and primary winding 35 of a transformer TI. A condenser 35 is connected across secondary winding 31 of transformer TI and the receiving circuit that including

inductors

32 and 33 and transformer TI is tuned to resonance at the frequency of the track circuit-current. For example, when alternating current of 100 cycles per second is used for the track circuit, the receiving circuit of the train is tuned to resonance at 100 cycles per second. Hence each on period of the track circuit current is reflected by an electromotive i'orce appearing across secondary winding 31of transformer T|, such electromotive force having the same frequency as the rail-current and having an amplitude proportional to the amplitude of the rail current. In other wordsthe elec tr'omotive'force appearing across secondary winding 31 possesses the same code characteristics as the rail current.

An amplifier including an electron tube 38 is provided. Electron tube 38 may be of any one of several well-known types and is shown as a triode having a plate 39, a grid 40 and a filament 4|. Filament 4| is normally heated from the usual train carried 32 volt generator whose terminals are indicated in Fig. 1 as B32 and N32, a resistor 43 being included inthe circuit. Grid 40 is included in a grid circuit comprising a condenser-resistance biasing element 42, secondary winding 31 and condenser 36 in multiple, a portion of resistor 43 and filament 4|.

A motor generator MG whose motor 44 is connected across terminals B32 and N32, converts the 32 direct voltage of the train carried gener ator into a voltage suitable for the plate circuit of tube 38 and which plate circuit extends from positive terminal B300 of generator 45 of motor generator MG over primary winding 45 of an output transformer T2, plate 39 and intervening tube space to filament 4| of tube 38 and resistor 43 to negative terminal N300 of the generator 45-. A primary winding 41 of a transformer T3 in series with a condenser 48 is connected to the plate circuit in multiple with primary winding 45 of transformer T2. The parts are so proportioned that a given value of plate circuit current normally flows. That is, when no voltage is applied to grid 40 from the receiving circuit, the plate current is of a preselected value. Hence the electromotive forces made to appear portioned to pass the alternating component of the plate circuit and hence an alternating electromotive force is induced in secondary winding 49 of transformer T3 during each on period of the coded current picked up from the track rails. The electromotive force induced in secondary winding 49 is applied to a relay PR through a rectifier 50. Relay PR is a slow release direct current relay'and is energized and held picked up in response to the alternating current created in the plate circuit of tube 38 by the coded track circuit current, the slow release period of relay PR being sufficient to bridge the 'off period of the current. I

A secondary winding 5| of transformer T2 is connected to an operating winding of a relay MR over a circuit including front contact '52 of relay PR and a reactor '53. Relay MR is a for causing a relay to be slow. acting being well-.

known in the art. When an effective electromotive force is made to suddenly appear across secondary winding 31 of transformer TI and a relatively large'change is suddenly created in the average value of the plate circuit current of tube 38, an electromotive force is induced in secondary winding 5| of transformer T2, it being recalled that the alternating current component of the plate circuit current is by-passed around primary winding by the path including condenser 48 and winding 41. The connections are made such that the electromotive force induced in secondary winding 5| due to a sudden increase in the average value of the plate current energizes relay MR at normal polarity as required to operate contact member 54 to the normal right-hand position, and the electromotive force induced in secondary winding 5| due to a sudden decrease in the average value of the plate circuit current energizes relay MR at reverse polarity as required. to operate contact member 54 to its reverse left-hand position. Referring to Figs. 2 and 3, the code characteristic for the track circuit current under a first traffic condition is such that the amplitude of the current gradually increases from a relatively low 1 to a. relatively high value and the currentis abruptly interrupted at the high value. Consequently, the average value of the plate current changes slowly during the on period and no effective electromotive force is induced in secondary winding 5| at the start of each on period, but when at the end of the on period the current is abruptly interrupted at its relatively high value, a relatively large change in the average value of the plate current occurs with the result a corresponding effective electromotive force is induced in secondary winding 5|. This electromotive forceinduced in secondary winding 5| is illustrated in Fig. 3 and as stated above it is of a polarity that energizes relay MRat normal polarity. Thus under this first traf'fic condition, relay MR is supplied with an energizing impulse at the end of each on code period but not at the start of the code period, and the successive impulses are all of the same polarity. Due to the slow acting characteristics of relay MR, relay MR is operated to its normal position only after several successive energizing impulses, but once it is moved to its normal position it remains in that position as long as these electromotive forces continue to occur at the preselected code rate. When such electromotive forces cease, relay MR shortly moves to its biased mid position under the influence of the biasing element of the relay. Looking now at Figs. 4 and 5, the

code characteristics for the track circuit underv the second traflic condition is -such as to cause the current to abruptly rise to its high value at the start of the on period and to gradually decrease to its low value at the end of the on period. Consequently, a relatively large change nated to cause signal CS to display a fourth in the plate circuit current is caused at the start of each on period to induce an electromotive force in secondary winding but substantially no electromotlve force is induced in secondary winding 5| at the. end of each on code period. This electromotive force induced in secondary winding 5| is illustrated in Fig. 5 and relay MR is successively energized at reverse polarity. Again after several of such energizing ,impulses relay MR is operated to its reverse position where it is held as long as this second code prevails. Looking at Figs. 6 and 7, the substantially uniform amplitude code characteristics effected in response to the third trailic condition is such that an abrupt change in the plate current is effected at the start and at the end of each on code period. The electromotive forces induced in secondary winding 5| are illustrated in Fig. 7 and are alternately of normal and reverse. polarity so that relay MR is alternately energized at normal and reverse polarity. Since relay MR is slow acting and does not respond to a single energizing impulse, the energization effected in the relay by one impulse is cancelled by the energization effected by the next impulse with the result that relay MR remains in its biased mid position for this. third code.

It is to be seen therefore, that relay PR is picked up for each of the three different codes and relay MR is held at its normal position for the first code, is held in its reverse position for the second code and at its biased mid position under the third code. Relays PR'and MR are used to control the operating circuits of a train control device such as a cab signal CS capable of displaying any one of four different indications.

Assuming the train TV occupies section DE as shown in Fig. 1 when traffic conditions in advance are such that the first code characteristic as illustrated in Fig. 2 is-impressed upon the track circuit current of section D-E, relay PR is picked up due to the alternating current component of the plate current and relay MR is held energized at its normal position. Under these circumstances an operating circuit extends from terminalB32 over front contact 58 of relay PR, normal contact 5455 of relay MR, lamp 5!! and to terminal N32, and lamp 59 is illuminated to cause cab signa1 CS to display a first indication.

In the event trafiic conditions in advance of section 'D-E are such that the code characteri tic is that illustrated in Fig. 4, relay PR is picked up by the alternating component of theplate current and relay -MR is energized in its reverse position. An operating circuit is formed which includes front contact 58 of relay PR, reverse contact 5456 of relay MR and lamp 60, and lamp 60 is illuminated to cause signal OS to display a second indication. When traific conditions are such that the code characteristic of the track circuit of section DE is that illustrated by Fig. 6, relay PR is picked up and relay MR remains at its biased position. An operating circuit is now formed including front contact 58 of relay PR. contact 54-51 of relay MR and lamp E and that lamp is illuminated to cause signal CS to d"sp1ay a third indication. Again, when section DE is occupied by a train in advance of train TV and the track circuit is shunted by such train "n advance, then relays PR and MR of train- TV are deenergized with the result that an operating circuit is formed over back contact 62 of relay PR and lamp I63, and that lamp is illumiindication.

In Figs. 8a and 8b there is disclosed trackway apparatus wherewith the two distinctive code characteristics illustrated in Figs. 2 and'4, respectively are added to a three indication frequency code system so that a total of five different indications are provided. In the embodiment here disclosed the two code rates or code frequencies of 180 and 75 are used for two distinctive frequency codes, the decreasing amplitude code characteristic of Fig. 4 is impressed on the 75 code rate for one additional distinctive code and the increasing amplitude code characteristic of Fig. 2 isimpressed on the 180 code rate for a seconjdiadditiOnal"distinctive code. That is, a first 1 indication is reflected by the absence of codedi current (shunted or occupied track circult), and the 75 code rate alone is employed for 20,-

the first track circuit to the rear of the occupied section to reflect a second indication, the 75 code rate with a decreasing amplitude characteristic is used for the second track circuit to the rear of the occupied track circuit to reflect a third indication, and 180 code rate with an increasing amplitude characteristic is used for the third track circuit to the rear of an occupied section to reflect a fourth indication, and the 180 code rate alone is used for the fourth track circuit to the rear of an occupied section to reflect a fifth indi cation.

In Figs. 8a and 8b, the track rails ia and lb of a stretch of railway over which traffic normally moves in the direction indicated by arrows are formed by the usual insulated rail joints into sections F, G, H, J and K, the entrance end of section F and the exit end of section K being only shown. Each track section is provided with a track circuit operative'to supply alternating current coded at any one of the several codes described above according to the' tramc conditions in advance of that section. The track circuit apparatus includes a code following track relay and two decoding relays in addition to the track relay, repeater relay and code forming means described for the track circuit of section DE of Fig. 1. For example, the track circuit apparatus of section G'includes as additional apparatus a code following track relay GFS connected across the rails through the usual associated transformer-rectifier GR in multiple with the first elemerit of track relay GTR, and two decoding relays GA and GL. Relay GFS is therefore operated at a rate corresponding to the code rate of the current supplied to the track circuit of section G and is operated at such code rate whether or not an increasing or decreasing amplitude characteristic is impressed on the code rate. Relay GFS when operated causes direct current periodically interrupted at a rate corresponding to the rate at which relay GFS is operated to be supplied to a decoding unit GDU over a simple circuit including contact member 63 of relay GFS. Thedecoding unit GDU may be any one of several forms and is shown conventionally since its specific structure forms no part of my invention. It is sufllcientfor this application to point out that decoding relays GA and GL connected 'to the output side of decoding unit GDU are energized and picked up according to the code rate .at which the code following relay GFS is operated, the arrangement being such that relay GL is picked up and relay GA is released for the code rate, both relays GL and GA are picked up for the 180 code rate and both relays GA. and GL are released when relay GFS is inactive.

It should be pointed out that the coder GCT associated with the track circuit apparatus of section G is provided with four contact members I80a, l88b, 15a and 15b, the contact members 180a and l8llb being each operated at the code rate of 180 times per minute and the contact. members la'and 151 being each operated at the code rate of 75 times per minute. Furthermore each coder associated with the apparatus of each track circuit of Figs. 8a and 8b is provided with four contact members the same as coder GCT.

It should also be pointed out at this time that in Figs. 8a. and 8b, the relative polarity and code rate of the current supplied to the track circuit is utilized to determine the code of the.

tionally at VTI occupies section F to shunt thev track circuit with the result that track relay FTR is deenergized to occupy its biased midposition and code following track relay FFS .is inactive causing the two associated decoding relays FA and FL to be released. When the relays of section F are conditioned to take the positions explained above due to train VTI occupying the section, alternating current is supplied to primary winding 64 of track transformer TG for the section G next in the rear of section F over a circuit extending from terminal BX, back contact 65 of relay FA, back contact 66 of relay FL, front contact of contact member 1517 of coder FCT, back contact 61 of repeater relay FPR, primary winding 64 of transformer TG, back-contact 88 of repeater relay FPR and to terminal CX. It follows that the track circuit of section G is supplied with alternating current coded at the '75 code rate and of uniform amplitude. The

current is of relative reverse polarity since repeater relay FPR is released to pole change the connection to transformer TG. Track relay GTR of section G is energized at its reverse or left-hand position, causing repeater relay GPR to be picked up. Code following relay GFS of section G is operated at the '75 code rate caus ing decoding relay GL to, be picked up and relay GA to be released.

With the relays of section G thus positioned, the primary winding 68 of transformer TH of section H is supplied with alternating current of the 75 code rate having impressed thereon the decreasing amplitude characteristic. The effective circuit includes terminal BX, reverse contact 18 of relay GTR, front contact H of relay GL, back contact 12 of relay GA, front contact of contact member 15a of coder GCT, a second reverse contact 13 of relay GTR, front contact 14 of relay GL, back contact 16 of relay GA, primary winding 11 ofsaturable reactor GTC of the code forming means of section G, front contact 18 of repeater relay GPR, primary winding 68 of transformer TH, front contact 18 of relay GPR and terminal CX. During each off-code period and back contact of contact member 15a of coder GCT is closed, current flows over the previously traced circuit up to contact member 1511, thence over back contact of contact member 15a, reverse contact 88 of relay GTR, one arm of rectifier GRF, reactor GRC, secondary winding 8| of reactor GTC, and a second arm of rectifier GRF to terminal CX, and. rectified current flows in the secondary winding 8| of reactor GTC to saturate that reactor during each off code period with the result that a decreasing amplitude characteristic is impressed upon the coded'current supplied to transformer TH and in turn supplied to the track circuit of section H in the manner fully explained in connection with Fig. 1. Since the repeater relay GPR, is picked up the current supplied to section H is of normal relative polarity.

With alternating current of anormal relative polarity of the '75 code rate supplied to section H, the second section in the rear of the occupied section F, track relay HTR is energized at its normal position causing repeater relay HPR to be picked up, and code following relay HFS is operated at the '75 code rate causing decoding relay HL to be picked up and relay HA to be released. Under such circumstances th primary winding 82 of track transformer TJ of section.J is supplied with alternating current of 180 code rate having impressed thereon an increasing amplitude characteristic. The circuit includes terminal BX, normal contact 83 of relay H'IR, front contact 84 of relay HL, back contact 85 of relay HA, front contact of contact member |88b of coder' HCT, normal contact 86 of relay H'I'R, front contact 81 of relay HL, back contact 88 of relay.HA, primary winding 88 of saturable reactor HTC, front contact 90 of repeater relay HPR, primary winding 82 of track transformer TJ, front contact 9| of relay HPR and terminal CX. During each on period that the front contact of contact member l80b is closed current also flows over the previously traced circuit up to contact member |80band the code rate, causing track relay 'J'IR. to

be energized .atnormal polarity and code following relay JFS to be operated at the 180 code rate to pick up both decoding relays JA and JL.

Under such condition of the relays for section J, the third section to the rear of occupied section F, the track circuit of section K, the fourth section to the rear of the occupied section, is supplied with current of the 180 code rate alone, the effective circuit extending from terminal CX over normal contact 85 of relay JTR, front contact 86 of relay JL, front contact 81 of relay JA,

front contact of contact member l88a of coder JCT, primary winding 88 of reactor JTC, front contact 88 of repeater relay JPR, primary winding 94 of transformer TK and front contact I88 of relay JPR to terminal CX. Since the secondary winding of reactor JTC is not supplied with rectified current then the circuit for supply ing alternating current to secondary winding 85 of track transformer TX is of substantially uniform impedance and the track circuit current of section K is of the 180. code rate, with a substantially uniform amplitude throughout the code Period.

Since section K is supplied with current of 180 code rate and of normal relative polarity, it is apparent that the track relay and the decoding relays (not shown) of section K are positioned the same as the corresponding relays of. section J with the result that the section next in the rear current increases andof the other polarity when the plate current decreases. Consequently relay MRI is operated in the usual manner due to of section K is supplied withcurrent of the same code characteristics as the current supplied to section K.

Referring to Fig. 9, the train. carried apparatus for cooperating with the track apparatus of Figs. 8a and 8b includes

inductors

32 and 33 and a first stage electron tube 38 the same as in Fig. 1, except that the secondary winding 5| of transformer T2 is, in Fig. 9, connected to the grid circuit of a second electron tube IOI having a plate I02, a grid I03 and a filament I04. The

filament I06 of tube IN is heated in series with the filament M of tube 38 and the'grid I03 is connected to secondary winding SI of transformer T2 as mentioned above. The plate circuit for tube IOI involves terminal B300 of the motor generator MG, primary winding I05 of a transformer T3, plate I02 and intervening tube space to filament I04 of tube WI, and thence over filament 5i and resistor 43 to terminal N300. Primary winding I05 of transformer T3 is by-passe'd by a condenser I06, and a secondary winding I01 of transformer T3 is connected to a three-position polar relay MR through a reactor 53, relay MR being of the same character as the corresponding relay of Fig. 1. A code following relay MRI is also connected to secondary winding I 0I. 1"

Relay MRI is a polar code following relay of the usual well-known form whose contact member I00 remains in the position to which it is last moved when the relay is deenergized. Direct current is alternately supplied to the two portions of a primary winding I00 of a decoding transformer T4 when relay MRI is alternately energizedat normal and reverse polarity causing operation-of its contact member I03 with the result that an alternating electromotive force is induced in secondary winding I I0 of transformer T0 the frequency of which electromotive force corresponds to the rate at which relay MRI is operated. Secondary winding I I0 is connected to two decoding circuits one of which includes in v series a condenser III and a reactor H2, and

such alternate polarities of the electromotive forces induced in secondary winding I01 and both decoding relays AI and LI are picked up. Relay MR which is .a slow acting polar relay is not effectively energized by such electromotive forces of alternate polarity for the reasons explained in full in connection with the polar relay MR of Fig. 1. With both relays-LI and AI picked up, closing front contacts H6 and Ill, respectively, an operating circuit for lamp II8 of signal CSI is completed, and that lamp is illumi-' nated to cause signal CSI to display a first or clear signal indication to indicate that there are at least three unoccupied sections in advance of' the train. I

When the train having mounted thereon the apparatus of Fig. 9 enters section J where the track circuit current is of the 180 code rate with v increasing amplitude characteristic, a co r reperiod and an effective electromotive force is induced in secondary winding -I0l of transformer T3 only at the end of the on period. These electromotive forces are all of the same polari'y and relay MRI remains at one position and both dethe other of which circuits includes a'reactor H3.

A decoding relay AI is connected across a portion of reactor II2 through a rectifier H4, and a second decoding relay LI is connected'to reactor I I3 through a rectifier I I5. The circuit including reactor H3 is non-tuned and relay LI is efiectively energized and picked up when relay MRI is operated at a rate corresponding either to the '75 or 180 code rate. The circuit ineluding condenser III and reactor H2 is tuned so that'relay AI is effectively energized and picked up only when relay MRI is operated at the rate corresponding to the 180 code rate. Relay MR together with the decoding relays AI and LI govern a, five-indication cab signal CSI.

Assuming, the train on which the apparatus of Fig. 9 is mounted is operating in section K of Fig..8b, which track circuit is supplied with current of the 180 code rate and uniform amplitude characteristic, a corresponding electromotive force is picked up by the

inductors

32 and 33 and amplified at tubes 30 and IN. As a result of such amplification of the electromotive force there is induced in secondary winding I01 of coding relays Li and AI are released because relay MRI is notoperated by electromotive forces all of the same polarity. After a few such electromotive forces relay MR is moved to its reverse position and an operatingcircuit is formed from terminal B over back contact II 9 of relay LI, contact 54-56 of relay MR, lamp I20 and to terminal C, and lamp I20 is illuminated to cause signal CSI to display a second or approach medium signal indication.

When the train advances to enter section H i where the track circuit current is of the 75 code rate with a decreasing amplitude characteristic,

the operation of the train carried apparatus is the 1 same as in section J except for the fact that relay MR is moved to its normal position due to the polarity of the electromotive force induced in secondary winding I0'I. An operating circuit is now formed including back contact I I 9 of relay LI, left-hand contact 5455 of relay MR and is operated at a corresponding code rate and relay LI is picked up and relay AI is released. Also relay MR is inactive. An operating circuit now is formed including front contact III; of relay LI. back contact I22 of relay AI and lamp I23. and that lamp is illuminated to cause signal CSI to display a fourth or approach signal indication.

In the event the train VTI remains in section F and the train on which the apparatus of Fig. 9 is mounted enters section F behind train VTI. the track circuit current is shunted by train VT I so that relays MRI and MR are both deenergized. An operating circuit now including back contact N9 of relay Li and contact 54-57 of relay MR and lamp E24 is completed, and lamp I24 is illuminated to cause signal CSI to display a fifth or slow speed signal indication.

It is to be observed that although wayside signals are not shown in either Fig. 1 or Figs. 8a and 8b, it is clear that wayside signals may be provided andcontrolled by the trackway apparatus shown in the drawings.

It is to be seen therefore that I have provided simple railway trafiic controlling apparatus incorporating novel means for a code signal system using distinctive code characteristics. have provided novel railway traffic controlling apparatus wherewith additional indications can be added to the present frequency code system without the necessity of additional code rates.

Although I have herein shown and described only two forms of railway traffic controlling apparatus embodying my invention, it is understood that various changes and modifications may be made therein within the scope of the appended claims without departing from the spirit and scope of my invention.

Having thus described my invention, what I claim is:

i. In railway trafiic controlling apparatus the Also I combination comprising, a track section, a source of alternating current, a circuit to connect said source to the rails of said section, means to periodically interrupt said circuit to cause the current supplied to the rails to have alternate on and oii periods, code forming means having a variable reactance included in said circuit and effective to cause an increasing amplitude or a decreasing amplitude of the alternating current each on period according as said reactance is progressivelydecreased or increased during the on period, and traflilc controlled means effective under one traffic condition to progressively decrease said reactance during each on period and effective under another traflic condition to progressively increase said reactance during each on period 2. In railway traiiic controlling apparatus the combination comprising, a track section, a source of alternating current, a circuit to connect said source to the rails of said section, means to periodically interrupt said circuit to cause the current supplied to the rails to have alternate on and off periods, code forming means having a variable reactance included in said circuit and effective to cause an increasing amplitude or a decreasing amplitude of the alternating current each on period according as said reactance is progressively decreased or increased during the On period, trafiic controlled means effective under one traffic condition to progressively decrease said reactance during each on period and effective under another trafiic condition to progressively increase said reactance during each on period, and receiving means coupled to therails -of saidsection responsive to such alternating on and off periods, code forming means including a variable reactance element interposed in said circuit and said code forming means effective when supplied with current during each on period to progressively decrease the reactance of said element to impress an increasing amplitude on the alternating current supplied to the rails, and trafiic controlled means to supply current to said code forming means during each on period in response to a given traffic condition in advance of said section.

4. In railway trailic controlling apparatus the combination comprising, a track section, a source of alternating current, a circuit to connect said source to'the rails of said section, means to penodically interrupt said circuit to cause the current supplied to the rails to have alternate on and off periods, code forming means including a variable reactance element interposed in said circuit and said code forming means effective when supplied with current during each off period to cause a progressively increasing value of the reactance of the element during the on period to impress a decreasing amplitude 0n the alternating current supplied to the rails, and traflic controlled means to supply current 'to said code forming means during each off period in response to a given traffic condition in advance of said section.

5. In railway traflic controlling apparatus the combination comprising, a track section, a source of alternating current, a circuit to connect said source to the rails of said section, means to periodically interrupt said circuit to cause the current supplied to the rails to have alternate on and oil periods,'code forming means having an element the impedance of which progressively decreases or increases according as unidirectional current is supplied to a winding of the code forming means or is interrupted therefrom, said element interposed in said circuit to impress an increasing or a decreasing amplitude code characteristic on the alternating current according as the impedance of said element is made to progressively decrease or increase during each on period, and traffic controlled means to supply unidirectional current to said winding during each on period only under one traflic condition and to supply such unidirectional cur- I rent to the winding during the 05 period only under another traflic condition.

6. In railway trafflc controlling apparatus the combination comprising, a track section, a source of alternating current, a circuit to connect said source to the rails of saidsection, means to pcriodically interrupt said circuit to cause the current supplied to the rails to have alternate on and off penods, code forming means including a saturable reactor having a primary winding and a secondary winding and said primary winding interposed in said circuit, a first traflic controlled .means to supply unidirectional current to said secondary winding during each on period of the alternating current to progressively decrease the impedance of said primary winding during each on period and impress an increasing amplitude characteristic on the alternating current in response to a first traflic condition in advance of the section, and a second traflic controlled means to supply unidirectional current to said secondary winding during each off period of the alter-.

nating current to progressively increase the impedance of said primary winding during each on period and impress a decreasing amplitude characteristic on the alternating current in response to a second traflic condition in advance of the section.

7. In railway trafiic controlling apparatus the combination comprising, a track section, a source of alternating current, a circuit to connect said source to the rails of said section, means to periodically interrupt said circuit to cause the current supplied to the rails to have alternate on and off periods, a code forming means including a saturable reactor' provided with a first and a second winding with said first winding interposed in said circuit, a first trafilc controlled means to supply unidirectional current to said second winding during each on period of the alternating current to progressively saturate the reactor and cause each on period of the alternating current to be characterized by an increasing amplitude, a second traffic controlled means to supply unidirectional current to said second winding during each off period of the alternating current to saturate said reactor and which saturation dies away during the next on period to cause each on period of'the alternating current to be characterized by a decreasing amplitude, and receiving means coupled to the rails of said section responsive to such alternating current andefiectively influenced to one condition by said increasing amplitude characteristic and to another condition by said decreasing amplitude characteristic.

8. In railway trafiic controlling apparatus the combination comprising, a track section, a source of alternating current, a circuit to connect said source to the rails of said section to supply cur rent'thereto, a coder'having a front contact interposed in said circuit to cause the alternating current to have alternate on and off periods, a saturable reactor having a first winding interposed in said circuit, means responsive to trafiic conditions in advance of said section and including a contact member moved to a first and a 'second position in response'to a first and a second traffic condition respectively, means including a front contact of said coder and the first position of said contact member to supply unidirectional current to a second winding of said reactor to magnetically saturate the reactor during each on period of the alternating currentand impress an increasing amplitude characteristic on the alternating current, and means including a back contact of said coder and the second position of said contact member to supply unidirectional current to said second winding to magnetically saturateof alternating current, a circuit to connect said source to the rails of said section to supply current thereto, a coder having afront contact interposed in said circuit to cause the alternating current to have alternate on: and off periods, a saturable reactor having a first winding interposed in said circuit to control the impedance of the circuit and a second winding to control the magnetic saturation of the -reactor; trafllc controlled means operable to a-first, a second and a third position in response to a, first, a second and a third traffic condition respectively in advance of said section; means including a front contact of said coder and the first position of said traflic controlled means to supply unidirectional current to said second winding to provide an increasing amplitude characteristic of the alternating current in response to said firsttraffic condition, means including a back contact of said coder and the second position of said trafiic controlled means to supply unidirectional current to said second windingto provide a decreasing amplitude characteristic of the alternating current in response to said second trafiic condition, and means including the third position of said traflic controlled means to deenergize said second reactor winding to provide a uniform amplitude characteristic of the alternating current in response to said third trafiic condition.

10. In railway traffic controlling apparatus the combination comprising, a track section, a source of alternating current, a circuit to connect said source to the rails of said section to supply current thereto, a coder having a front contact interposed in said circuit to cause the alternating current to have alternate on and off periods of a preselected code rate, a saturable reactor having an impedance winding interposed in said circuit and provided with a saturating winding; traflic controlled means operable to a first, a second or a third position in response to a first, a second or a third traflic condition respectively in advance of said section; means including a front contact of said coder and the first position of said trafiic con-trolled means to supply unidirectional current to said saturating winding to cause a progressing decrease in the impedance of said impedance winding each on period of said coder to provide an increasing amplitude code characteristic of the alternating current in response to said first trafiic condition, means including a back contact of said coder and the second position of said traffic control led means to supply unidirectional current to said saturating winding to cause a progressing increase in the impedance of said impedance winding each on period to provide a decreasing amplitude code characteristic of the alternating current in response to said second traffic condition, and means including the third position of said trafiic controlled means to bypass said circuit around said impedance winding to provide a uniform amplitude code characteristic of the alternating current in response to said third trafiic condition.

11. In railway traffic controlling apparatus the combination comprising, a track section; trafiic controlled means to supply to the rails of the section alternating current periodically interrupted at a preselected rate and operative to provide an increasing amplitude code characteristic of the current under a first traflic condition, a decreasing amplitude code characteristic of the current under a second traflic condition and an uniform amplitude code characteristic of the current under a third trafiic condition; a train to travel said section, receiving means responsive to such alternating current and mounted on .the train in inductive relation to the rails, and train carried signaling means coupled to said receiving means and including a three-position relay effectively operated to a. first position in response to periodically interrupted alternating current of said increasing amplitude code characteristic, to a second position in response to periodically interrupted alternating current of said decreasing amplitude code characteristic and to a third position in response to periodically interrupted alternating current of said uniform amplitude code characteristic.

12. In railway trafilc controlling apparatus the combination comprising, a track section; traffic controlled means to supply to the rails of the.

position, a reverse position and a biased position; and amplifying means on the train to couple said receiving means to said relay and effective to supply to the relay energizing impulses of normal polarity for positioning the relay at its normal position when the alternating current supplied to the rails is provided with said increasing amplitude characteristic, energizing impulses of reverse polarity for positioning the relay at its amplitude code character- 15. In railway trafiic controlling apparatus the combination comprising, a track section, a source of alternating current, a coder provided with two reverse position when the alternating current supplied to the rails is provided with said decreasing amplitude characteristic and energizing impulse alternately of normal and reverse polarities for holding the relay at its biased position when the alternating current supplied to the rails is provided with said uniform amplitude characteristic.

13. In railway trafiic controlling apparatus the combination comprising, a tracksection, circuit means to' supply to the rails of the section alternating current periodically interrupted at a preselected rate, trafiic controlled code forming means including a'saturable reactor interposed in said circuit means to impress on said alternating current an increasing or a decreasingamplitude characteristic in response to a first or a second trailic condition respectively, a train to travel said section, and train carried receiving apparatus including an inductor mounted on the train in inductive relation to the rails, a polar relay, amplifying means coupled to said inductor and connected to said relay and operative to supply to the relay successive energizing impulses oi one polarity when the alternating current is characterized by said increasing amplitude and of the opposite polarity'when the alternating cur- .rent is characterized by said decreasing amplied code rates, trafiic controlled means including said contact members to connect said current source to the rails of said section to supply to the rails alternating current of a first or a second code rate in response to a first or a second traflic condition in advance of the section respectively, a code forming means including a saturable reactor, and other tramc controlled means including a selected one of said contact members and said code forming means to connect said current source to the rails of said section to supply to the rails alternating current of a preselected one of said code rates further characterized by a progressive change in the amplitude of the current during each on code-period.

contact members operated at different preselected code rates, trafllc controlled means including said contact members 'toconnect said current source to the rails of said section to supply to the rails alternating current of a first or a second code rate in response to a first or a second tramc condition in advance of the section respectively,

'a code forming means including a saturable re-.

actor, other trafilc controlled'means including a selected ore of said contact members and said code forming means to connect said current source to the rails of said section to supply to the rails alternating current of a preselected one of said code rates further characterized by a progressive change in the amplitude of the current during each on code period, a train to travel said section, a receiving circuit mounted on the train responsive to such codedalternatingcurrent, a first and a second code responsive relay mounted on the train, train carried amplifier to couple said receiving circuit to said relays and effective to operate said first relay in response to said'first and second codes and to effectively energize said second relay in response to said third code, and a train carried train control device governed by said first and second relays.

16. In railway trafilc controlling apparatus the combination comprising, a track section, a source of alternating current, a coder provided with two contact members each operated at a distinctive code rate, traffic controlled means including said contact members to connect said current source to the rails of said section to supply to the rails alternating current of a first or a second code rate in response to a first and a second traflic condition respectively, a code formingmeans including a saturable reactor having a first and a second winding, other traflic controlled means including a selected one of said contact members and said first reactor winding to connect said current source to the rails of said section to supply to the rails current of said selected one of said code rates, means including said selected contact member to supply unidirectional current to said second reactor winding during each oil code period to impress upon said coded current ofsaid one code rate a decreasing amplitude characteristic, still other trafllc controlled means including the other contact member and said first reactor winding to connect said current source to the rails of said section to supply to the rails current of the other code rate, and means including said other contact member to supply unidirectional current to said second reactor winding to impress on the coded current of said other code rate an increasing amplitude characteristic.

17. In railway trailic controlling apparatus the combination comprising, a track section, a'source of altenating current, a circuit to connect said source to the rails of said section, means to ,periodically interrupt said circuit to cause the current supplied to the rails to have alternate on and off periods, and trafllc controlled means associated with said circuit and including a vari- 'able element to cause the alternating current to have an increasing amplitude characteristic each on period under one tra-filc condition in advance of the section and to have a decreasing amplitude characteristic each on period under another trafiic condition in advance of the section.

combination comprising, a circuit, supply means connected to said circuit and effective to supply the circuit with alternating current having alternate on and off periods, code forming means associated with said supply means and effective to cause the alternating current to be coded by an increasing amplitude characteristic or by a decreasing amplitude characteristic each on period according to a first or second condition of the coueforming means, control means op- 10