US2279971A - Railway traffic controlling apparatus - Google Patents

Description

April'` 14,1942.

y R. K, CROOKS RAILWAY TRAFFIC CONTROLLING APPARATUS `ITiled Nov. A16, 1940 HIS ATTORNEY Patented Apr. 14, n

` RAILWAY n `2,279,971 TRAFFIC coN'rRoLLING APPARATUS 'Ralph K. Crooks, Sharpsburgg Pa.,- assignor to "The Union Switch & Signal Company, Swissvale, Pa., a corporation of Pennsylvania Application November 16, 1940, Serial No. 365,886

` Claims.

My invention relates `to railway traliic fcontrolling apparatus and `more particularly to train carried train control apparatus `responsive to coded current. i i i Railway traffic controllingapparatus 'responsive to coded energy is well known and train carried train control'apparatus responsive. to coded alternating track circuit current hasfoundwide use. The track circuit customarily includes the track rails of a track section and the alternating current supplied thereto is coded by being periodically interrupted at a `preselected rate. n' 'MIhe alternating current is ordinarily of 100` cycles per second. Such coded alternating current has alternate on and 01T` periods, current ilo'wing during each on period and no current flowing during each oif period. The on and oif periods of a code are ordinarily of equal durations. 4Such `track circuit current `is coded at anyqone of several different code rates according to :different traffic conditions, `the code `rates `of 180; "120 and 75 interruptions per minute being thosejcom- `inonly used to reflect clear, approach-medium and approach traffic conditions, respectively. A receiving circuit is mounted onthe train inductive relation `to `the track rails to receive an `electromotive forcelinresponse to `aclion` period same code'rate as the rail current. vThe yelectro- 4of the track rail current.

vcuit being `tuned for response tocurrent of a frequencycorresponding to a respective code rate false `signal aspect.

Itfiscustomary to provide on railway trains `a 82 volt source of current, such as a battery or direct current generator for supplying current to traint Alighting circuits, locomotive headlight `cirlcuits,a`nd similar equipment. It is desirable that [the same train carried source of current be `usted as the current sourceior the train control apparatus without the necessity of providing means such as a dynamotor or a motor generator to con- ".vert the 32 volts of the usual source of supply to e fsome other voltage.

current supplied to the trackrallsarrdisfof the motive force pickedup `by the trainlcarried -re- Y ceiving circuit is amplified by means lofwan lelectron tube amplier and is used tocontrol the operation of a code ffollowingY relay,V suchrclay being operated at a rate corresponding to the code rate of the rail current. The codefollowingrelay is'coupled jtotheplate circuit of--the amplifier tube and isloperated in response'to the variations of the platecircuit current as caused tube during the on and off periods'of theelectro'- motive force received` from the ,track'rai-ls. That is to say, the code following relayA is operated *in `by the voltage applied tojthe control grid of the response to the variations of the plate current caused by thevariations `of the voltage applied to the grid during the on and off periods of the code.`

The code following relay in -turn'selec'tivelyz lgoverns cab signal and trainbra'ke control equi-p- `ment through` the medium` of a decoding means i which is selectively Aresponsive tothe several dirferent code rates@- The decoding means `usually `includes .different tuned circuits, eachsuch cir- In View of the foregoing conditions, a feature of my invention is the provision of a novel and improved low voltage electron tube amplifier for railway trafccontrolling apparatus.

"Another feature of myy invention is the provision in railway traiiic controlling apparatus of a novel and improved amplifier operable iromj a 'single 32 volt source of direct current. f

Again,`a feature of my invention is the provilsion of `an improved amplifier for railwaytraflic l controlling apparatus wherein a relativelylarge ratio lof change in the plate circuit current of a vacuum tube to a change in the applied alternat- `inggrid voltage is effected. a i i Still another` feature of my invention is the provision in railway traffic controlling apparatus fof novel and improved `means wherewith false operation of a signal or brake control device from 4intermittent open circuit conditions is avoided.,

To obtain the above" features, as :well as other advantages of my invention Which Will become apparent `as the specification progresses, `I Apro-- videaccordingto my invention a lowvoltage type of electron tube with heater and plate circuits, each of which circuits is voperable when connected to a 32 voltfsource of direct current.

`The grid circuit of such electron tube is `coupled lto the train carried receiving circuit to apply an The code following f To increase the ratio of the change in plate .circuit current to,

a given change in applied alternating grid volt-1.'.

age, a special plate circuit of relatively high impedance to both the alternating current com- K ponent and the low frequency variations of the plate circuit current is provided. To this end a i winding is interposed in the plate circuit and which winding is by-passed by `a condenser effec-y tive to by-pass the alternating current component but not the low frequency variations of the plate circuit current. This Winding may be the operating winding of a code following relay or it may be the primary winding of a low frequency type of transformer to the secondary Windingof which the code following relay is connected. Hence the code following relay is operated by the energy supplied thereto due to the low frequency variations of the plate circuit current. and a primary winding of this latter transformer is interposed in the plate cir-cuit in series with the condenser. This reactor transformer furnishes a, high impedance to the alternating current component of theplate circuit current. A slow release relay is connected to a secondary winding of the reactor transformer and is effectively energized and picked up in response to the alternating current component of the plate circuit current. These two transformers provide a l plate circuit of high impedance and that effects a substantially large ratio of change in the plate circuit current to a given change in the applied -grid Voltage.

The supply of current to the decoding means it might cause operation of the code following relay, will not cause energization of the slow release relay with the result that the decoding means is not operated falsely to create a false signal aspect due to an intermittentopen circuit condition.

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 with train carried train control apparatus. Fig. 2 is a diagrammatic view showing another form of apparatus embodying my invention when used with train carried train control apparatus. Fig. 3 is a diagram illustrating operating characteris- .tice of the apparatus of Figs. 1 and 2.

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

Referring to Fig. 1, the reference characters Ia `and Ib designate the track rails of a railway.

A reactor transformer is also furnished s section wouldbe supplied with coded alternating 75 `former TI current, the alternating current being of a frequency of say, for example, 100` cycles per second. The trackway apparatus for supplying coded current to the rails is not shown since it forms no part of my invention and may be any one of several well-known arrangements. The arrangement of such trackway apparatus may be that disclosed in Letters Patent of the United States, No. 1,986,679, granted January 1, 1935, to L. V. Lewis for Railway trac controlling apparatus, and it is sufficient for the instant application `to point out that the track rails Ia .and Ib are supplied with alternating current coded at the rate of 180, 120 and '75 cycles per minute in response to clear, approach-medium and approach traffic conditions, respectively.

' Two inductors 2 and 3 are mounted on a train in inductive relation to the track rails Ia and Ib, respectively. Inductors 2 and 3 are connected intoa receiving circuit which also includes a condenser 4 and the primary winding 5 of a trans- A condenser is connected across a` secondary winding 1 of transformer TI and the transformer and receiving circuit are tuned to resonance at the frequency of the rail current. That is, when alternating current of 100 cycles is used then the train carried receiving circuit and transformer TI are tuned to resonance at the frequency of 100 cycles per second.

It is to be understood, of course, that my invention is not limited to the use of 100 cycle alternating current, but alternating current of suchfrequency is widely used and is used here for the purpose of illustration, but the alternat-` ing current can be of any convenient frequency.

It follows that an alternating electromotive force appears across the terminals of secondary winding 'I and condenser 6 in response to the coded alternating current supplied to the track rails,such electromotive force being of the same frequency and code rate as that of the current supplied to the track rails.

A low Voltage electron tube TT is carried on the train. Electron tube TT may be of any one of several types and as here shown it is a tetrode, having a plate 8, a cathode 9, a control grid I0, another grid I I and a lament I2.

The reference TB designates a 32 volt source of direct current, such as a battery. Preferably the `current source TB would be that usually provided on the railway train for supplying current to the train `lighting circuits and similar equipment, but it is to be understood that my ,invention is not limited to the use of the usual train carried current source and the current vsource TB may be independent and used only for the train control equipment. Furthermore, it is to be understood that my invention is not limited to a 32 volt source of current and a low voltage .sourcepof a voltage other than 32 volts may be used.

A heater circuit is provided for electron tube TT by connecting the filament I2 across the battery TB as rwill be understood by an inspection of Fig. 1. Preferably cathode 9 is connected to the negative terminal of filament I2 and grid II is lconnected to the positive terminal of filament I2.

A grid circuit for tube TT extends from control grid ID over blocking condenser I5 and a resistor I6 in multiple, secondary winding 'I of transformer TI and condenser 6 in multiple and thence `to cathode 9. Tube TT is provided with a plate circuit which can be traced from the positive terminal B32 of battery TB over primary winding I3 of a reactor transformer T2, to be later asador/'T1 referred to, primary winding I4 ofS a low frequency transformer-"T3, to be alsoreferred to later, plate -8 and intervening tube space to cathode'` '9 of tube 'I"I'.and` thence to the negative terminal C32 of battery TB. A condenser I'I is connected acrossiprimary winding I4 of transformer T3. A polar code following relay MS is connected tosecondary winding I8 oftrans-` former T3 throughia full waverect'ier I9, and aslow release relay RS is `connected to secondary winding of transformer T2 `through a full wave rectii'lerZI."` i l l*Code following relay MS is preferably a polar relaywhose "contact member is biased to normally engage a normal contact 26 and is oper-` Y ated "5to" engage a reverse contact 21 when the relay isenergized by current of al preselected polarity; RelayRS is a neutral slow releasing relay,v Relays MS and RS control `the supply of current to the primary winding 22fof a decod- `ing `transformerv DT, the` secondary Winding 23 of whichis `connected to the input terminals of a decoding means DM. When relay RS is picked up closing front contact 24 andrelay MS is deenergized 4and` `its contact member -25 engages normal' contact 26, direct `current 'from battery mary winding 22 of transformer DT,`and when relay MS isenergized at a preselected polarity to operate its contact member 25 to engage reversecontact 21 and relay RS is also picked up, current flows from battery TB to the right-hand portionof primary winding 22. Thus with relay RS picked :up and relay MS operated `direct current is alternately suppliedzto the two portions of `primarywinding 22 of transformer DT and the several `well-known forms and may be thek tuned` circuit arrangementcovered by Letters Patent of the United States No. 1,773,515, granted August 19, 1930, to C. C. Buchanan for Railway traffic controlling apparatus; It is sufficient for this` application to pointA out that three control relays A, Rand L connected to the -output side of decoding means DM are selectively controlled according to thefrequency of` the current `supplied -to its input terminals.v As `here shown,

`relaysl and L `are `effectively energized and picked up when decoding'meansDM is supplied with current of arfrequency created by operation ofarelayIMS atarate corresponding tothe 180 `code rateof the trackrail current. RelaysR and L are effectively energized and picked up and relay A is released when current of a frequency created by operation of relay MS at a ratefcorrespondingA to the 120` code rate of therail curr'entisl supplied to `the `decoding means DM, and

relay L is effectively4 energized and picked up and relays A, and R are released when the decoding means `DM is Supplied With current of a frequency corresponding to operation of relay MS in response tootrackcrail current of the 75 code rate. All three `.of the control relays A, R and L i are released when code `following relay MS is inactive and when relayRS is released. 1

Control relaysA, R and L are used to control the operating circuits of 'train control apparatus here shown asfacab signal CS, signal CS being `a four-position color lightsignal. IThe operating `'IIB islsupplied to the `left-hand portion of prii lcircuits for signal CS are those `commonly employed and as here shown when relay A is picked up closing front contact 28 an operating circuit leasily traced lis formed for lamp 29 and that lamp is illuminated to cause signal CS to display a clear signal indication; When relay A is released, fclosing back contact 39 and relay R is picked up closing frontcontact 3|, an operating 'circuit `is formed for lamp 32 and that lamp is illuminatedto cause signal CS to display an approach-medium signal indication. When relays A and R are released,` closing back contacts 33 and 33, respectively, and relay L is picked up closing front contact 34, an voperating circuit is formed for lamp 35 and that lamp is illuminated to cause signal `CS to display an approach signal indication 4When relays A, R and L are released closing back contacts 3D, v33 and 36, respectively, fa-n operating circuit is formed for `lamp 31 and that lamp is illuminated to cause signal CS to display `a slow speed signal indication.

In describing the operation of the apparatus of Fig. 1, reference is also made to the plate-current plate-voltage characteristic curves of Fig. 3. With filament `I2 of tube T'I heated and with no -electromotive lforce picked up by the receiving circuit so that the potential of grid I0 with respect to the cathode 9 is zero (e. g.=0) and the 32 Volts from battery TB are impressed on the plate circuit a given steady direct current flows in the plate circuit.` This condition is indicated by the `curve CI `of Fig. 3, the value of the plate voltage `being indicated by line PV of Fig. 3 :and the value of the plate current being indicated `by :line PA.k Under this condition of steady direct current in the plate circuit, no energy is transferred through either transformer T2 or T3, and relay RS is released and code following relay MS is inactive. `This condition of relays RS and MS causesno electromotive force to be induced in `secondary winding 23 of the decoding transformer ADT and hence the control relays A; R and L arefall deenergized and released with the result that lamp 31 is illuminated to cause signal CS to display a slow speed signal indication. It vfollows thatiabsence of track rail current causes a slow` speed cab signal indication.

Ishallnext assume Ithat alternating current of the code rate is supplied to the rails Ia and Iband `a corresponding alternating electrornotive force is picked up -by the receiving circuit.

This alternating electromotive force is applied between thev control grid |13 and cathode 9 of tube The blocking condenser I5 and resistor I6 function in the usual manner andhence the potentialof control grid I0 is varied with respect to cathode 9 during theon period of the code by .each `cycle of the rail currentl Such electrometive force picked up by the receiving circuit has a frequency of cycles per second and an alternating current component of corresponding frequency is created in the plate circuit current. Furthermore, due to the effect of blocking condenser I5 and resistor'l, theaverage Value of the direct current component of the plate circuit current is ydecreased during each on period of the code and is then restored to its normal value duringA each olf period; The condenser I'I is effective to by-pass the alternating component of the plate circuit current around primary Winding I'4`2of transformer T3 but is not effective to bypass the variations of the direct current component of the plate circuit current. Hence each `tirne the 'average value of the ydirect current plate circuit current is decreased at the start'of Van on code period and is increased at the start of each 01T period of the code an electromotive force is induced in secondary winding I8 of transformer T3. This electromotive force induced in secondary winding I8 is rectified and unidirectional current is supplied to relay MS which energizes that relay at the previously mentioned preselected polarity causing contact member 25 of the relay to be operated to engage reverse contact 21, contact member 25 being operated back to engage normal contact 2B subsequent to each operation to the reverse position by the biasing means of the relay. The alternating current component of the plate circuit current induces an electromotive force in secondary Winding 20 of transformer T2 which electromotive force is rectified and unidirectional current is supplied to relay RS and that relay is energized and picked up. Current is supplied to relay RS only during the on period of the code, but relay RS is maintained picked up during each off period of the code, due to its slow release characteristics. It follows that relay RS is picked up and code following relay MS is operated at a rate corresponding to the '75 code rate of the track rail current which rate of operation of relay RS is effective to cause relay L to be picked up and relays A and R to be released with the result that lamp 35 is illuminated to display an approach signal indication.

When the rail current is coded at either the 120 or 180 code rate, the operation of the apparatus is the same except for .the rate of the operation of the code following relay MS and the selection of the control relays A, R and L, relay RS being picked up in response to each code rate. When the code rate is 120 then control relay RA is picked up and relay A is released so that lamp 32 is illuminated to display an approach-medium indication and relay A is picked up in response to the 180 code rate so that lamp 29 o-f signal CS is illuminated to display a clearsignal indication.

Referring again to Fig. 3, if the load or impedance in the plate circuit is that represented by the load line V-W and if an alternating voltage is applied to control grid I of the electron tube 'IT which drives the grid to a negative voltage of two Volts (e. g.=2) the average value of the direct current in the plate circuit is reduced from a value indicated by the line PA to a value indicated by the line PB. The line V--W represents the conventional load line for amplifiers of the type here involved. I have found that if instead of a plate circuit load represented by the line V-W the load is increased to a value represented by the line X-Y of Fig. 3, the change in the average value of the direct current plate circuit will be increased when the same applied grid voltage is applied to control grid I0 and would be reduced to a value represented by the line PC of Fig. 3. This increase in the change of the average value of the plate current is due to the presence of high impedance provided by the transformers T2 and T3. In other words, the reactor transformer T2 which is of high impedance to the alternating component of a plate circuit current and the low frequency transformer T2 and condenser I1 which are of low impedance to the high frequency variation of the plate circuit current are effective to increase the change in the average value of the plate circuit current in response to a `given grid voltage.

In Fig. 2, the apparatus is the same as in Fig. 1, except a code following relay MSI replaces the code following relay MS, the winding A38 of relay MSI being interposed in the plate circuit of tube 'IT and transformer T3 being omitted. Condenser I1 is connected across winding 38 of relay MSI to by-pass the alternating current component of the plate circuit current around relay MSI. Relay MSI is operated in response to the variation of the average value of the plate circuit current for tube TT, being picked up to close front contact 39 when no voltage is applied to control grid IIJ and being released to close back contact 40 when the average value of the plate current is reduced due to the grid voltage applied to grid I0 during each on period of the coded current. Hence code following relay MSI is operated at a rate corresponding to the code rate of the track rail current the same as code following relay MS of Fig. l. Slow release relay RS of Fig. 2 is controlled by energy transferred through transformer T2 the same as in Fig. 1 and hence operation of code following relay MSI in response to coded alternating track rail cur-l rent causes direct current to be alternately supplied to the two portions of primary winding 22 of decoding transformer DT and an electromo- ,tive force of a corresponding frequency is induced in secondary winding 23 of the decoding transformer and applied to the decoding means DM to govern the control relays A, R and L. l It is to be seen, therefore, that the apparatus of Fig. 2 operates in substantially the same manner as the apparatus of Fig. 1 in response to coded alternating rail current.

It is to be seen therefore that I have provided novel and improved amplifiers for railway traflic controlling apparatus which are operable When connected to a single 32 volt source of direct current. Transformers T2 and T3 provide a plate circuit for the electron tube which pro- Vides an increase in the change of the average value of the direct current due to a given applied grid Voltage and effective operation of the code following relay is assured. Also the slow release relay RS. is effective to check the presence of the alternating current component of the plate circuit and a cab signal indication due to an intermittent open circuit condition is avoided.

It should be pointed out that the principle set forth herein lends itself very effectively to control circuits in which a considerable change in direct current is required by the application of a relatively small alternating voltage.

Although I have herein shown and described only two forms of 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:

1. In railway traffic controlling apparatus for use with a receiving circuit mounted on a train in inductive relation to the track rails for receiving an electromotive force when alternating current coded at a given rate is supplied to the rails, the combination comprising: an electron tube having a plate, a cathode and a control grid mounted on the train; a grid circuit connected across said grid and cathode of the tube and coupled to said receiving circuit to apply to the grid the electromotive force received by said receiving circuit, a control winding, a condenser, a transformer; a plate circuit including a current Source, the primary Winding of said transformer and said control winding and said condenser in multiple and connected across `said plate and cathode of thetube; contact means controlled by said control winding in response to the variations of the plate circuit current caused by the I5 `on. and off code periods of o such'electromotive force applied to said grid, 'arelay` connected to the secondary winding of said transformer to control that relay in response to' the `alternating current component oftheplat circuit current `1g) caused by said, electromotiveforce applied to said grid, and a train carried signalingcircuit controlled jointly by said'relay and said contact means. i

2. In railway traflic controlling apparatus for use with a receiving circuit mountedon a train "l in inductive relation tothe track rails for receiving an electromotive force when alternating cur# rent coded at a given` rate is supplied to the rails,

the combination comprising:` an electron Vtube having a plate, a cathode and a'control grid mounted on the train; a grid circuit connected across said grid andcathode ofthe tube and coupled to said receiving circuitto apply to the gridv the electromotive force received by said re- 25 ceiving circuit, a transformer: a plate circuit` inclujding a current source, the primary winding of said transformer and another winding and connected across said plate and cathode of the tube;

a contact member controlled by said other winding and operable to engage a first and a second Contact in response to the changes in the energiz ation of said other winding due to the variations in the plate circuit currentcaused by the onand off code periods of said ,electromotive forcefapg5 plied to said grid,`a slow release relay connected to the secondary winding of said transformer through `a` rectifier to pick up that` relay in response to the alternating current component of the plate circuit current caused by said elec- Q tromotive force applied to said grid, and train an electromotive force when alternating current coded at a given rate is Supplied tothe rails, thel combination comprising, an electron tube having ,go a plate, 4a cathode and a control grid mounted on the train; a grid circuit A connected across said grid and cathode ofthe tube and coupled to said receiving circuit to apply to the gridthe electromotive force received by said receiving circuit, V`a transformer; a plate circuit including aV current source anda Winding of said transformer and connected across the plate and cathode of said tube, aA code following relay electrically associated with said'` plate circuit to `operate such) relay in re- Il69 sponse to the variations of the plate circuit current causedby the on and off code periods` of said electromotive force applied tov said control grid, a slow release relay connected to another winding of said transformerthrough `a rectifier toeffec- I tively energize said slow release relay in response to the alternating current component of the plate circuit current caused during each on period of said. electromotive force applied to said control grid, and" train carried signaling means controlled 7 jointly by said code following relay and said slow release relay.

4. In railway traiiic controlling apparatus for use with a receiving circuit mounted on a train in inductive relation to the track rails for receiv- 7 ing an electromotive force when alternating currer-1t coded at a given rate is Supl-liedk to the rails, theA combination comprising: Van electron tube having a plate, a cathode anda control grid mounted lon the train; a grid circuit connected "across `said grid and cathode` ofA the tube and coupled to said receiving circuit to apply `to the` grid the electromotive force receivedby said receiving circuit, a transformer; a platecircuit infcluding a current source and a winding of said transformer and connected across the plate and cathodeof s aid tube, a code following relay electrically associated with said plate circuit to operate such `relay in responseto the variations of the plate circuit current caused bythe on and off code periodsof said electromotiveforce applied to said control grid, a slow release relay connected to another winding of said transformer through a rec-l tifier to effectively energize said slow release relay 'in response to the alternating curernt component of the plate circuit current, caused by. each on period of said `electromotive force applied to said control grid,` and train carried signaling means controlled by said relays and `effectively energized when and only when said slow release relay is picked up erated. o

5. In railway traine controlling apparatus for use with a receiving circuit coupled to a` trans-- mitting circuit for receiving an electromotive and said code following relay is op-v `force when alternating current coded at a given rate is supplied to such transmitting circuit, the combination comprising: an electron tube having a plate, a cathode and a control grid; a grid circuit connected across said grid and cathode of thetube and coupled to said receiving circuit to "apply to the grid the electromotive force received by said receiving circuit, a plate circuit for said tube including a `source oi' current, a code following relay electrically coupled to said plate circuit and operated by the increase and decrease of the direct current component of the plate circuit cur` rent due to the variations of the grid voltage caused by' the on and offcode'periods of said electromotive force, a transformer having a first winding interposed in said plate circuit, another relay connected to a second winding of said transformer and effectively energized by the energy transferred thereto in response to the alternating current component of the plate circuit current caused by the harmonic variations of the grid voltage during each on period of said electromotive force, and a control circuit controlled jointly by said code following relay and said other relay.

6. In railwayktraiiic controlling apparatus for use with a receiving circuit mounted on` a train in inductive `relation to the track rails for receiving an electromotive force when alternating current coded at`a given code rate is supplied to the rails,` the `combination comprising: an electron tube having a plate, acathodel and a control grid mounted on the train; a grid circuit connected across said grid and cathode of the tube and coupled to said receiving 'circuit to `apply toy the grid the electromotive force re kceived by said receiving circuit, a first and a secto. said grid, a slow release relay coupled to a second winding of said transformer for picking up that relayvby the energy transferred thereto due to the alternating current component of the plate circuit current caused by said electromotive lforce applied to said grid, and train carried signaling means controlled by said relays effectively energized only when said code following relay is operated and said slow release relay is picked up.

7-. In railway traffic controlling apparatus for usewith a receiving circuit mounted on a train Vin inductive relation to the track rails for receiving an electromotive force when alternating current coded at a given rate is supplied to the rails,the combination comprising: an electron tube having a plate, a cathode and a control grid mounted on the train; a grid circuit connected across said grid and cathode of the tube and coupled to said receiving circuit to apply to the grid the electromotive force received by said receiving circuit, a first and a second transformer; a plate circuit including a current source and la first winding of each of said transformers and connected across the plate and cathode of said tube, a code following relay coupled toa second winding of said rst transformer for operation ofthe relay by the energy transferred thereto ,due to the decrease and increase in the average value of the plate circuit current kcaused by the electromotive force applied to said grid, a slow release relay coupled to a second winding of said second transformer for picking up that relay by the energy transferred thereto due to the alternating current component of the plate circuit current caused by said electromotive force applied to said grid, decoding means responsive tocurrent of a frequency corresponding to said given code rate, and a control circuit including a contact of said code following relay and a front contact of said slow release relay for supplying current to said decoding means.

8. In railway traflic controlling apparatus for usewith a receiving circuit mounted on a train in inductive relation to the track rails for receiving an electromotive force when alternating current coded at a given rate is supplied to the rails, the combination comprising: an electron tube having a plate, a cathode and a control grid mounted on the train; a grid circuit connected across said grid and cathode of the tube and coupled to said receiving circuit to apply to the grid the electromotive force received by said receiving circuit, a transformer, a code following relay, a condenser; a plate circuit including a current source, a first winding of said transformer and a winding of said code following relay and said condenser in multiple and connected across the plate and cathode of said tube; said condenser effective to by-pass around said relay winding the alternating current component of the plate circuit current and ineffective to by-pass the low frequency variations of vthe plate circuit current as caused by said electromotive force applied to said control grid for operation of said relay in response to the on and oif code periods of said electromotive force, a slow release relay connected to a second winding of vsaid transformer through a rectifier to ener- L gize and pick up such relay in response to said alternating current component of the plate circuit current, decoding means responsive to current of a frequency corresponding to said given code rate, and means including a front contact of said slow release relay and a contact of said code following relay for supplying current to said decoding means.

9. In railway traffic controlling apparatus for use with a receiving circuit mounted on a train in inductive relation to the track rails for receiving an electromotive force when alternating current coded at a given rate is supplied to the rails, the combination comprising: an electron tube having a plate, a cathode and a control grid mounted on the train; a grid circuit connected across said grid and cathode of the tube and coupled to said receiving circuit to apply to the grid the electromotive force received by said receiving circuit, a current source, a heater-circuit for said tube connected across said current source, a reactance device, a condenser, a winding; a circuit including said current source, said reactance device and said winding and condenser in multiple and connected across the plate and cathode of said tube to provide a plate circuit of relatively high impedance to current of said given frequency and of relatively high impedance to variations of the plate circuit current corresponding to said code rate; contact means controlled by said winding effectively operated to a rst and a second position by the variations of the plate circuit current caused by the on and off periods of said electromotive force applied to said grid, and a train carried signaling circuit controlled by' said contact means effectively energized only when said contact means is operated.

10. In railway traic controlling apparatus for use with a receiving circuit mounted on a train in inductive relation to the track rails for receiving an electromotive force of a predetermined frequency and a preselected code rate when alternating current of said frequency and coded at said code rate is supplied to the rails, the combination comprising: a low voltage electron tube having a plate, a cathode and a control grid mounted on the train; a grid circuit including a winding coupled to said receiving circuit and a condenser-and a resistor in multiple and connected across said grid and cathode of said tube, a low voltage source of direct current, a heater circuit for saidtube connected across said current source, a reactance device of relatively high impedance at said predetermined frequency, another winding and another condenser connected in multiple; a plate circuit including said current source, said reactance device and said otherl winding and other condenser and connected across said plate and cathode of said tube, contact means controlled by said other winding effectively operated by the decrease and increase in the average value of the plate circuit current caused by the coded electromotive force applied to said grid because of said high impedance of said reactance device, and signaling means controlled by said contact means when operated.

RALPH K. CRooKs.

CERT IFICATE OF CORRECTION patent No. 2,279,971. April -1L;A 19kg.

Hnry Van Arsdale, (seal)4 Acting Commissioner of Patents.

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