US2068736A - Train dispatching system for railroads - Google Patents

Description

Jan. 2 1937.

O. H. DICKE TRAIN DISPATCHING SYSTEM FOR RAILROADS Filed April 12;, 1923 VE 0R Y "I'TORNEY Patented Jan. 26, 1937 FATE??? FEQE TRAIN DISPATCHING SYSTEM FOR RAILROADS Application April 12, 1928, Serial No. 269,388

24 Claims.

This invention relates to train dispatching systems, and more particularly to the type of system in which a dispatcher communicates with an engineer of a moving train through the medium of signal indications.

In a system of the type mentioned the track switches at passing sidings are preferably operated by switch machines controlled by the dispatcher, and these track switches preferably have signals associated therewith for indicating to the engineer of an approaching train whether he is to take the main track or siding; and if he is headed away from the siding informing him when he may proceed. By reason of the fact that information must be transmitted to the engineer either through cab or wayside signals provision must be made to transmit many distinctive indications to each passing siding. If wayside signals are used each passing siding would require 20 at least eight signals and if the switches are to be power operated two switch machines are preferably employed. It is thus important that these various controls be transmitted over the least number of line wires, such line wires also aiiord ing means for communicating to the dispatchers office the existence of traflic conditions at such passing siding.

In accordance with the present invention it is proposed to use a single line circuit to transmit 30 such distinctive controls, such line circuit being applied to a railway signalling system having an alternating current transmission line associated therewith. This single line circuit, in addition to said transmission line, forming the medium for controlling all of the switch machines and signals associated with a single passing siding and also afiording a medium through which to inform the dispatcher when there is a train passing over a particular track switch of such passing siding.

More specifically it is proposed to apply alternating current potential of one or another relative polarity, direct current potential of one or another polarity or both of these potentials to the line circuit, and to have connected in series with each other (or in multiple if desired) a polarized alternating current relay and a polarized direct current relay at the corresponding passing siding, whereby either of these relays may be energized to either of their energizing conditions irrespective of the condition of the other relay. In addition it is proposed to connect in series with the line circuit but located in the dispatchers office a direct current and an alternating current indicating relay, and to provide means at the passing siding for impeding or stopping the flow of direct or alternating current or both, depending upon which of the two detector track circuits associated with the two track switches of the passing siding are occupied or whether both of these track circuits are occupied, whereby one or the other or both of the indicating relays in the dispatchers ofiice will be deenergized and will light indicating lamps corresponding to the occupancy of the particular detector track circuit or circuits.

Other objects, purposes and characteristic features of the invention will in part be obvious from the accompanying drawing and in part be pointed out in the specification hereinafter.

In describing the invention in detail reference will be made to the accompanying drawing conventionally illustrating the apparatus in the tower and the apparatus associated with one passing siding only of a railway system having the invention applied thereto.

Referring to the accompanying drawing the invention has been shown applied to one passing siding PS only, of a railway system having a large number of passing sidings, which railway system may be either a double track system or it may be a single track system employing wayside signals of the absolute-permissive type, it being understood that the rest of the passing sidings employ duplicate apparatuses except as to the alternating current transmission line TL energized by a generator Gand the common return wire CL, which lines extend through the entire portion of the railway system governed by a single dispatcher located in the dispatchers office DO. Referring particularly to the railway system the track rails 3 of the main track and the rails l of the siding are divided into block sections in the usual way by insulating joints 5, so as to constitute the usual track circuits each including a track relay and a source of current. Of these detector relays the detector track relay DTE and DTW only have been shown, and these have been shown conventionally by dotted lines.

The entrance of a train into the east end of the track or side track of the passing siding PS is governed by the main signal I and the takesiding signal I and the departure of a train from the main track and side track, respectively, is governed by the starting signals 2 and 2 Similarly, the entrance and departure of trains at the west end of the passing siding PS is governed by signals 1, i 8 and 8 The east end of the passing siding PS includes a track switch ES and the west end of this same passing siding includes a track switch WS. These track switches are preferably operated by switch machines through the medium of control relays DC and AC all in a manner as more clearly pointed out in the application of S. N. Wight, Ser. No. 120,423 filed July 3, 1926 which control mechanisms and circuits are conventionally shown by dotted lines I 4 and I5 through contacts 4d of these relays. Similarly, the signals I, I 2, 2 I, I 8, and 8 are controlled in accordance with the condition of contacts 45 of the control relays DC and AC and in accordance with the position of the track switches ES and WS, in a manner as described in said Wight application, and as shown conventionally by dotted lines l6, l1, I8 and I 9. The present invention relates principally to the manner in which the polar control relays AC and DC are controlled from a distant dispatchers ofiice over the same line Wire, and how the occupancy of detector track circuits containing track relays DTW and DTE are transmitted to the dispatchers ofiice over this same line wire, and for this reason the control circuits for the switch machines and the signals associated therewith controlled by the control relays AC and DC have not been specifically illustrated. In this connection it may also be pointed out that the way-side signals may be entirely omitted and the dispatching information transmitted to the engineer through the medium of signals located in the engine cab controlled in any suitable manner, as for instance, shown in Fig. 19 of said Wight application.

At the west end of the passing siding PS is provided a control relay AC of the three-position type, which is preferably a relay responsive only to alternating current and of either the dynamometer or induction type, having its one winding connected in series with the line wire LW and having its other winding connected across the AC transmission line TL. Similarly, there is located at the east end of the passing siding PS a three-position or polar control relay DC, which preferably includes either a permanent magnet or a locally energized direct current electro-magnet and which relay has its winding connected in series with the line LW. The control relay AC is controlled in accordance with the position of the lever WL having contacts Ill and I I, and the control relay DC is controlled by a lever EL having contacts l2 and I3. In the dispatchers ofiice is also located a miniature track layout having a passing siding ps and including, among other things, miniature indicating lamps IW and IE, which indicate the condition of occupancy of the detector track circuits associated with the west and east end of the passing siding PS, respectively. The various features of the present invention are believed best understood by considering the operation of the system.

Operation-With the levers WL and EL, located in the dispatchers office D0, in their neutral normal position, as shown,.the way-side signals associated with such levers are in the stop position shown, this for reason more clearly pointed out in the Wight application above referred to. Also, with these levers WL and EL in their normal neutral position, the indicating lamps IW and IE associated with the miniature passing sidings ps are extinguished. This is the case in spite of the fact that the contacts 55 and 42 of the indicating relays ACI and DCI are closed, and is true because their energizing circuits are open at contacts Ill and I2, respectively.

Let us assume that there is a west-bound train approaching the passing siding PS and that the dispatcher wishes this train to take the main track and proceed through the passing siding. To accomplish this, the dispatcher will move his lever EL to the right, and since the track switch is already in the main track position this track switch will not be operated, but the signal I will be caused to assume its clear position, providing trafiic conditions in advance are clear, this because the control relay DC is energized toward the right hand main track position through the following circuit:beginning at the battery 29, wire 2 l Winding of the indicating relay ACI, wire 22, winding of the indicating relay DCI Wires LW and 23, winding of the relay AC, Wire 24 contact 25 of the detector track relay DTW Wires 25 and 21, front contact 28 of the detector track relay DTE, wire 29, winding of the control relay DC (causing this relay to assume its right-hand energized position) wires 36, CL and BI, contact H of the lever WL, wires 32 and 33, contact I3 of the lever EL in its right-hand position, wire 33 back to battery 20.

With this circuit completed, not only is the control relay DC energized to its right-hand position but the indicating relay DCI, which responds only to direct current, also assumes its right-hand position, and for this reason the indicating lamp IE is not illuminated even though contact I2 has been closed. If the West-bound train in question is to pass through the passing siding PS, as has been assumed, the signal I must also be clear. In order to clear the signal I the dispatcher will move his lever WL to the right-hand position and in so doing will momentarily open the circuit which was just traced but will complete the same circuit with the righthand portion of the secondary winding of transformer T connected in series therewith. In other words, alternating current of a particular relative polarity is superimposed upon the direct current flowing in the line circuit. This AC current will cause control relay AC to assume its righthand energized position, thus causing the signal I to assume its clear indicating condition, providing trafiic conditions in advance are favorable. Not only is the alternating current relay AC energized but the indicating relay ACI is likewise energized to its right-hand position, thereby maintaining the indicating lamp IW extinguished in spite of the closure of contact Id.

Let us now assume that the west-bound train in question passes the signal I, and in so doing treads on the detector track circuit containing the track relay DTE. The entrance of the train on the detector track circuit containing this track relay DTE causes the contact 28 thereof to drop thereby deenergizing the control relay DC. This dropping of the contact 28 will, however, not cause deenergization of the control relay AC because the substituted partial circuit comprising, wires 37 and all, condenser 38 and inductance 39, has the capacities of the condenser and induc tance so chosen that the two units in series are resonated to the frequency of thealternating current employed, so that the flow of alternating current there through is not materially, if at all,

diminished. The line circuit as now changed includes the condenser 38 in series, and for this reason direct current cannot flow in this circuit even though this circuit has impressed thereon direct current potential supplied by the battery 20, and the direct current indicating relay DCI will assume its deenergized condition and will cause illumination of the indicating lamp IE through the following circuit:beginning at the terminal B of a suitable current source, such as a battery, contact 22 of the lever EL, wire 41, contact 42 of the indicating relay DCI, wire 13, indicating lamp IE to a common return C connected to the other side of such battery.

The illumination of the indicating lamp IE informs the dispatcher that the train in question is entering the east end of the passing siding PS. As soon as the rear end of the train clears the detector track circuit containing the track relay DTE the indicating lamp IE is again extinguished for obvious reasons. As the train in question enters upon the detector track circuit containing track relay DTW at the west end of the passing siding PS, it causes dropping of the contacts 25 and 46 thereby causing the control relay AC to be shunted through these contacts 25 and 46 in series, and also causes the original line circuit to be broken at the front point of contact 25. Dropping of contact 46, however, reestablishes the circuit slightly modified by inserting the tuned unit, comprising the inductance 50 and the condenser 5| in multiple, in series with the line wire LW.

With the unit Fall-51 tuned to potential resonance, as distinguished from current resonances, included in series with the line wire LW the alternating current is decreased to such a value that the indicating relay ACI assumes its deenergized position, thereby completing the following circuit for illuminating the indicating lamp IW:-beginning at the terminal B of a suitable battery, contact ll) of lever WL in its right-hand position, wire 54, contact 55 of the indicating relay ACI in its deenergized condition, wire 56 indicating lamp IW to the common return wire C connected to the other side of said battery. The dispatcher is thus informed by the illumination of the indicating lamp IW that the westbound train is now occupying the detector track circuit containing the track relay DTW.

Let us assume that at this time, namely, with the detector track relay DTW deenergized, there is a following train entering upon the detector track circuit containing detector track relay DTE, and that both of these detector track relays assume their deenergized position. Under this condition the line circuit includes both alternating and direct current potential, but the constants of the circuit are such as to allow no direct current and very little alternating current to flow. This line circuit with both levers to the right and both detector track relays deenergized may be traced as follows:beginning at the secondary winding of the transformer T, wire 33, contact l3 of the lever EL, wire 34, right-hand portion of battery 20, wire 2!, winding of indicating relay ACI, wire 22, winding of indicating relay DCI, wires LW and 60, contact 46 of the detector track relay DTW in its deenergized condition, wires 6i and 52, the unit 5!35l tuned to potential resonance (restricting flow of alternating current), wires 63 and 21', contact 28 of the detector track relay DTE in its deenergized condition, wire 3?, condenser 38, (blocking the flow of direct current) inductance 39, wires 49, CL and 3|, contact H of the lever WL in its right-hand position, back to the right-hand terminal of the secondary winding of transformer T.

No direct current can flow in the circuit just traced for the reason that the condenser 38 is in series therewith, and very little, if any, alternating current can flow in this circuit by reason of the tuned unit 58-5! tuned to potential resonance is included in series therewith. For this reason, both of the indicating relays ACI and DCI will assume the deenergized condition and the indicating lamps IW and IE will be illuminated, indicating to the dispatcher that both of the detector track circuits of the passing siding PS are occupied.

Obviously, if the lever LE is moved to the lefthand position direct current of the reverse polarity will flow and the control relay DC is energized to the left-hand position. Likewise if the lever LW is moved to the left-hand position the alternating current supplied to the line LW is of reversed relative polarity as compared with the local windings 65 and 6B of the relay ACI and AC, respectively, and therefore these relays A01 and AC will assume their left-hand energized position. It is, of course, understood that with the control relay AC or DC energized to the left-hand position the corresponding track switch is operated by a suitable switch machine SMW or SME to the take siding position, in which event the corresponding dwarf signal of takesiding signal is cleared depending on the direction of trafiic set up.

In connection with the direction of trafiic just mentioned, it is to be understood that the direction of trafiic travel is determined by the sequence of operation of the various levers located in the dispatchers ofiice through interlocked relays, all in a manner as described in detail in the Wight application above referred to.

Although switch machines have been conventionally shown, it should be understood that the invention may be applied to systems where the track switches are thrown by hand or where spring switches are used.

Having thus shown rather conventionally and described how two switch machines and eight signals may be controlled, and the condition of occupancy of two detector track circuits may be indicated, over a single line circuit, in any combination or sequence of controls and indications without interference, and having shown how train movements may be governed over an entire railway system by a single dispatcher, it is to be understood that the particular circuit arrangements and devices selected have not been chosen to illustrate the scope of the invention or the particular arrangement preferably employed in practicing the invention, but have been selected for the purpose of illustrating the nature of the invention in a simplified and direct way; and it is further desired to be understood that changes, modifications and additions may be made to adapt the invention to the particular conditions encountered in practicing the same, all without departing from the spirit and scope of the invention or the idea of means underlying the same, except as demanded by the scope of the appended claims.

What I claim is:-

1. In a train dispatching system, the combination with a line circuit containing a relay responsive only to alternating current and a relay responsive only to direct current in series and located at a distant way station, means at a local dispatchers ofiice for applying alternating current or direct current or both to the line circuit including said relays in series, an alternating current indicating relay and a direct current indicating relay located at said dispatchers oifice connected in series with said line circuit, and means at said way station for stopping the iii) flow of direct current without interfering with the flow of alternating current or reduce the flow of alternating current without interfering with the flow of direct current to cause de-energization of one or the other of said indicating relays.

2. In a train dispatching system, the combination with a railway signal system including a passing siding, signals associated with each end of said passing siding; a relay responsive only to current of one character for controlling the signals at one end of said passing siding; a relay responsive to current of another character for controlling the signals at the other end of said passing siding; a dispatchers ofiice; two indicating relays in said dispatchers office one responsive only to said current of one character and the other responsive only to current of said another character; a circuit including all of said relays which circuit if energized by current of one character will cause the two relays responsive thereto to assume the energized position and if energized by current of said another character will cause the remaining two relays to assume an energized position; means at the dispatchers office for energizing said circuit with current of said one character, current of said another character, or currents of both characters; and means at said passing siding for blocking the flow of current of one character without blocking the flow of current of said another character.

3. In a train dispatching system, the combination with a railway signal system including a passing siding, signals associated with each end of said passing siding, a relay responsive only to current of one character for controlling the signals at one end of said passing siding, a relay responsive to current of another character for controlling the signals at the other end of said passing siding, a dispatchers office, two indicating relays in said dispatchers oflice one responsive only to said current of one character and the other responsive only to current of said another character, a circuit including all of said relays which circuit if energized by current of one character will cause the two relays responsive thereto to assume the energized position and if energized by current of said another character will cause the remaining two relays to assume an energized position, means at the dispatchers office for energizing said circuit with current of said one character or current of said another character or currents of both characters, and means at said passing siding for blocking the flow of current of either character without blocking the flow of current of the other character.

4. In a train dispatching system, the combination with a railway signal system including a passing siding, signals associated with each end of said passing siding, a relay reponsive only to current of one character for controlling the signals at one end of said passing siding, a relay responsive to current of another character for controlling the signals at the other end of said passing siding, a dispatchers oifice, two indicating relays in said dispatchers oifice one responsive only to said current of one character and the other responsive only to current of said another character, a circuit including all of said relays which circuit if energized by current of one character will cause the two relays responsive thereto to assume the energized condition and if energized by current of said another character will cause the remaining two relays toassume an energized condition, means at the dispatchers office for energizing said circuit with current of said one character or current of said another character or currents of both characters, and means at said passing siding for blocking the flow of current of one character only, blocking the flow of current of the other character only or blocking the flow of current of both characters depending on trafiic conditions of said passing siding.

5. In a train dispatching system, the combination with a railway system including a passing siding; signals associated with each end of said passing siding; a relay responsive only to current of one character for controlling the signals at one end of said passing siding; a relay responsive to current of another character for controlling the signals at the other end of said passing siding; a dispatchers ofiice; two indicating relays in said dispatchers office one responsive only to said current of one character and the other responsive only to current of said another character; a circuit including all of said relays which circuit if energized by current of one character will cause the two relays responsive thereto to assume the energized condition and if energized by current of said another character will cause the remaining two relays to assume an energized condition; means at the dispatchers ofiice for energizing said circuit with current of said one character, current of said another character or currents of both characters; and filtering means in said circuit and at said passing siding for permitting the flow of current of one character while restricting the flow of current over another character.

6. In a train dispatching system, the combination with a railway signal system including a passing siding, signals associated with each end of said passing siding, a relay responsive only to current of one character for controlling the signals at one end of said passing siding, a relay responsive to current of another character for controlling the signals at the other end of said passing siding; a dispatchers ofiice, two indicating relays in said dispatchers oflice one responsive only to said current of one character and the other responsive only to current of said another character, a circuit including all of said relays which circuit if energized by current of one character will cause the two relays responsive thereto to assume the energized condition and if energized by current of said another character will cause the remaining two relays to assume an energized position, means at the dispatchers ofiice for energizing said circuit with current of said one character of said another character or currents of both characters, filtering means at said passing siding for permitting the flow of current of one character without permitting the fiow of current of said another character, and means for rendering said filtering means active under certain conditions of traffic only.

7. In a train dispatching system, the combination with a railway signal system including a passing siding, signals associated with each end of said passing siding, a relay responsive only to current of one character for controlling the signals at one end of said passing siding, a relay responsive to current of another character for controlling the signals at the other end of said passing siding, a dispatchers oifice, two indicating relays in said dispatchers oflice one responsive only to said current of one character and the other responsive only to current of said another character, a circuit including all of said relays which circuit if energized by current of one character will cause the two relays responsive thereto to assume the energized condition and if energized by current of said another character will cause the remaining two relays to assume an energized condition, means at the dispatchers ofiice for energizing said circuit with current of said one character of said another character or currents of both characters, two filtering devices the first restricting the flow of current of one character and permitting the flow of current of the other character, and the second restricting flow of current of said another character but permitting the flow of current of said one character, and means for rendering one or the other of said filtering devices active depending on trafiic conditions.

8. In a train dispatching system; the combination with a railway signal system including a passing siding; signals associated with each end of said passing siding; a relay responsive only to current of one character for controlling the signals at one end of said passing siding; a relay responsive only to current of another character for controlling the signals at the other end of said passing siding; a dispatchers office; two indicating relays in said dispatchers oflice one responsive only to current of one character and the other responsive only to current of said another character; a circuit including all of said relays which circuit if energized by current of one character will cause the two relays responsive thereto to assume the energized condition and if energized by current of said another character will cause the remaining two relays to assume an energized condition; means at the dispatchers office for energizing said circuit with current of said one character, of said another character or currents of both characters; and two filtering devices, the first of which restricts the flow of current of one character and permits the flow of current of the other character, and the second of which restricts the flow of current of the other character but permits the flow of current of said one character, and means for rendering one or the other or both of said filtering devices active depending on trafiic conditions.

9. In a train dispatching system; the combination with a railway signal system including two track switches comparatively close together; signals associated with each of said track switches; a relay responsive only to alternating current for controlling the signals at one track switch; a relay responsive only to direct current and controlling the signals at the other track switch; a dispatchers office; two indicating relays in said dispatchers office, one responsive only to alternating current and the other responsive only to direct current; a circuit including all of said relays, which circuit if energized by alternating current will cause the two alternating current relays to assume an energized condition, and if energized by direct current will cause the remaining two relays to assume the energized condition; means at the dispatchers ofilce for energizing said circuit with alternating current, or direct current, or both alternating and direct current; and means at said two sidings for blocking the flow of alternating current without blocking the flow of direct current, or vice versa.

10. In a train dispatching system the combination with a railway signal system including two track switches comparatively close together, signals associated with each of said track switches, a relay responsive only to alternating current for controlling the signals at one track switch, a relay responsive only to direct current and controlling the signals at the other track switch, a dispatchers office, two indicating relays in the said dispatchers ofiice, one responsive only to alternating current and the other responsive only to direct current, a circuit including all of said relays which circuit if energized by alternating current will cause the two alternating current relays to assume an energized condition and if energized by direct current will cause the remaining two relays to assume the energized condition, means at the dispatchers office for energizing said circuit with alternating current or direct current or both alternating and direct current, and means at the two sidings for blocking the flow of either alternating or direct current without blocking the flow of the other current.

11. In a train dispatching system the combination with a railway signal system including two track switches comparatively close together, signals associated with each of said track switches, a relay responsive only to alternating current for controlling the signals at one track switch, a relay responsive only to direct current and controlling the signals at the other track switch, a dispatchers ofiice, two indicating relays in the said dispatchers ofiice, one responsive only to alternating current and the other responsive only to direct current, a circuit including all of said relays which circuit if energized by alternating current will cause the two alternating current relays to assume an energized condition and if energized by direct current will cause the remaining two relays to assume the energized condition, means at the dispatchers ofice for energizing said circuit with alternating current or direct current or both alternating and direct current, and means at said two sidings for blocking the flow of either direct or alternating current or blocking the flow of both alternating and direct current.

12. In a train dispatching system the combination with a railway signal system including two track switches comparatively close together, signals associated with each of said track switches, a relay responsive only to alternating current for controlling the signals at one track switch, a relay responsive only to direct current and controlling the signals at the other track switch, a dispatchers oifice, two indicating relays in the said dispatchers office, one responsive only to alternating current and the other responsive only to direct current, a circuit including all of said relays which circuit if energized by alternating current will cause the two alternating current relays to assume an energized condition and if energized by direct current will cause the remaining two relays to assume the energized condition, means at the dispatchers oifice for energizing said circuit with alternating current, with direct current or both alternating and direct currents, and filtering means in said circuit and near said two track switches for permitting the flow of direct current while restricting the flow of alternating current or vice versa.

13. In a train dispatching system the combination with a railway signal system including two track switches comparatively close together, signals associated with each of said track switches, a relay responsive only to alternating current for controlling the signals at one track switch, a relay responsive only to direct current and controlling the signals at the other track switch, a dispatchers ofiice, two indicating relays in the said dispatchers oflice, one responsive only to alternating current and the other responsive only to direct current, a circuit including all of said relays which circuit if energized by alternating current will cause the two alternating current relays to assume an energized condition and if energized by direct current will cause the remaining two relays to assume the energized condition, means at the dispatchers office for energizing said circuit with alternating current, with direct current or both alternating and direct current, and filtering means at said two track switches for permitting the flow of direct current while restricting the flow of alternating current or vice versa, and means for rendering said filtering means active to have different filtering characteristics depending on traflic conditions.

14. In a train dispatching system the combination with a railway signal system including two track switches comparatively close together, signals associated with each of said track switches, a relay responsive only to alternating current for controlling the signals at one track switch, a relay responsive only to direct current and controlling the signals at the other track switch, a dispatchers office, two indicating relays in the said dispatchers office, one responsive only to alternating current and the other responsive only to direct current, a circuit including all of said relays which circuit if energized by alternating current will cause the two alternating current relays to assume an energized condition and if energized by direct current will cause the remaining two relays to assume the energized condition, means at the dispatchers oilice for energizing said circuit with alternating current or direct current or both alternating and direct current, and two filtering devices, the first restricting the flow of alternating current and permitting the flow of direct current and the second restricting the flow or" direct current while permitting the flow of alternating current, and means for rendering one or the other of said filtering devices active depending on traflic conditions.

15. In combination, a circuit including two relays one of which is responsive only to current of one character and the other of which is only responsive to current of another character; means for including a source of energy of said one character, of said another character, or sources of both said characters in said circuit; and controllable means for blocking the flow of current of said one character without blocking the flow of current of the said another character.

16. In combination, a circuit including two relays one of which is responsive only to current of one character and the other of which is only responsive to current of another character means for including a source of energy of one character, or another character, or sources of both characters in said circuit; controllable means for blocking the flow of current of one character Without blocking the flow of current of the other character; and other controllable means for blocking the flow of current of said other character without blocking the flow of current of said one character.

17. In a system of the character described, a track circuit, a signal governing traffic over said track circuit, a relay for controlling said signal, a control circuit for said relay governed from a distant point, means including said control circuit and responsive to the flow of direct current in said circuit for maintaining an indicating circuit at said distant point open while said track circuit is unoccupied, and other means responsive to alternating current flowing in said control circuit for indicating the occupancy of another track circuit.

18. In a train dispatching system, the combination with a siding, a detector track circuit at one end of said siding, signals governing traffic over said siding, a control relay, a line circuit controlled from a distant control point, manually operable means at said control point for energizing and de-energizing said line circuit to control said relay, means for opening said line circuit while said detector track circuit is occupied, an indicating lamp at said distant control point lighted so long as said detector track circuit is occupied and said manually operable means is in a position to energize said line circuit, another track circuit, and another indicating means including a source of alternating current rendered active when another track circuit near said siding is occupied.

19. In a dispatching system or the character described, a line circuit extending from a central control point to a distant siding and having a control relay therein, a manually operable circuit controller and a source of current for energizing said line circuit and located at said central control point, a direct current indicating relay at the central control point in said line circuit, an alternating current indicating relay at said central control point included in said line circuit, indicating means rendered active while said direct current indicating relay is de-energized and said circuit controller is operated, another indicating means controlled by said alternating current relay, a track relay at said siding acting when deenergized to open said circuit to de-energize said direct current relay and another track relay at said siding for blocking the flow of alternating current in said line circuit to effect de-energization of said alternating current relay.

20. In a train dispatching system, the combination with a railway track having adistant passing siding including a track switch at each end thereof, a switch machine for each of said track switches, signals associated with each of said switch machines for directing the movement of trams into and out of each end of said passing siding, a local dispatchers ofiEice, a line circuit connecting said dispatchers oflice and said passing siding and including in series two direct current responsive relays and two alternating current responsive relays one of each class of said relays being located at said siding and one of each class of said relays being located at said dispatchers ofiice, means at said dispatchers ofiice for energizing said direct current relays or said alternating current relays or both said direct current relays and said alternating current relays, means at said passing siding for restricting the flow of direct current only, alternating current only, or both direct and alternating current in accordance with 'track occupancy at one end, at the other end, and at both ends of said passing siding respectively, means for controlling the signals associated with one of said track switches by the direct current relay at said passing siding and controlling the signals associated with the other track switch by the alternating current relay at said passing siding, and signals in said dispatchers office controlled by said relays in said dispatchers oflice.

21. In a train dispatching system, the combination with a railway track having a passing siding, of a track switch associated with said passing siding, signals associated with said passing siding, a switch machine for operating said track switch, a dispatchers ofiice, a line circuit connecting said dispatchers office and said passing siding, a direct current responsive relay included in said line circuit and located near said switch machine for operating said switch machine, an alternating current responsive relay included in said line circuit and located near said signals for operating said signals, and means at said dispatchers office for independently operating said direct current and said alternating current relay or operating said relays simultaneously through the medium of said line circuit.

22. In a train dispatching system, the combination with a railway track having a passing siding, of a track switch associated with said passing siding, signals associated with said passing siding, a switch machine for operating said track switch, a dispatchers ofiice, a line circuit connecting said dispatchers ofiice and said passing siding, a direct current responsive relay included in said line circuit and located near said switch machine for operating said switch machine, an alternating current responsive relay included in said line circuit and located near said signals for operating said signals, means at said dispatchers office for independently operating said direct current and said alternating current relay or operating said relays simultaneously through the medium of said line circuit, means at said dispatchers ofiice distinctively detecting the flow of direct and alternating current in said line circuit, and means at said passing siding for distinctively blocking the flow of direct or alternating current in said line circuit.

23. In combination with a railway switch and a signal for governing the movement of traffic over said switch, a first manually operable lever,

a second manually operable lever, a pair of line wires extending from a point adjacent said levers to a point adjacent said switch, a first source of current, a second source for supplying current of a different character than current supplied by said first source, means for controlling the operation of said switch by current from said first source supplied to said line wires by said first lever, means for controlling said signal by current from said second source supplied to said line wires by said second lever, two track sections, a track circuit for each of said sections each including a track relay, a first approach indication means controlled through a contact of the first of said track relays by current from said first source supplied to said line wires by said first lever, and a second approach indication means controlled through a contact of the second of said track relays by current from said second source supplied to said line wires by said second lever.

24. In a traffic controlling system for railroads; a local ofiice and a distant way station; traffic controlling devices at said way station; two distinctive current responsive control relays at said way station for controlling said trafilc controlling devices; two distinctive current responsive indication relays at said office; a pair of line wires connecting said oflice and way station and interconnecting said relays; two correspondingly distinctive sources of current at said oifice; means for applying one, the other or both of said distinctive sources of currents to said pair of line wires to energize one, the other or both of said control relays; and traffic controlled means located at said way station for, when both of said sources of current are applied to said pair of line wires, controlling the flow of either of said sources of current through its corresponding indication relay without interfering with the flow of the other distinctive current.

OSCAR H. DICKE.

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