US2082463A - Train dispatching system for railroads - Google Patents

Description

June 1, 1937.

N. D. PRESTON ET AL 2,463 TRAIN DISPATCHING SYSTEM FOR RAILROADS Filed March 14, 1929 3 Sheets-Sheet l g/am ATTORNEY 3 Shets-Sheet 2 N D. PRESTON ET AL TRAIN DISPATCHING SYSTEM FOR RAILROADS Filed March 14, 192

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N. D. PRESTON ET AL 2,082,463

TRAIN DISPATCHING SYSTEM- FOR RAI LROADS Filed March 14, 1929 E F W I 3 Sheets-Sheet 3 CiIIII-IZIIIII Patented June 1, 1937 UNHTED STATES assists PATENT @FEHQE TRAIN DISPATCHING SYSTEM FOR RAILROADS Application March 14, 1929, Serial No. 347,011

37 Claims.

This invention relates to systems for dispatching' trains on railroads, in which the operation of switches, signals and other traffic controlling devices, are under the control of an operator or dispatcher, the invention being more particularly directed to a system of communication to and from the dispatchers oflice for obtaining the desired indications or controls.

In one type of a communication system for 1Q transmitting indications or controls to and from the dispatchers ofiice, circuits or communication channels are automatically set up in rapid sequence over a pair of line wires extending from the dispatchers ofiice along the railroad, and the 15 desired indications or controls are transmitted independently at difierent times over these channel circuits. This type of communication system is conveniently termed the synchronous type, as. distinctive from other forms of communica- 20 tion. systems using various combinations of code impulses.

In a system for dispatching trains or handling railway traffic, it is essential that the dispatcher be advised of the movement of trains on the railroad under his supervision. This reporting of train movements, commonly referred to as OS-ing trains, is. readily obtained with the synchronous type system, without the complication of lock-out means or the like to prevent interference be- 30, tween the indications given by trains entering or leaving track sections simultaneously, since the momentary channel circuits, over which the OS indications. are transmitted, are set up sequentially, so that, several trains may enter or leave track sections simultaneously without any interference between the OS indications.

It is this problem of OS-ing trains which renders the synchronoustype system specially adaptable for train dispatching; and the principal object of." the present invention is to expand, improve and adapt the synchronous type communication system to the condition and requirements of train dispatching systems.

In accordance with the present invention, it

( is proposed to use relays, in lieu of rotating circuit controlling devices, for sequentially setting up the momentary channel circuits. Such a bank ofv sequentially operated relays for channel circuit selection is considered to be highly desirable 5 0 for the way-station equipment, and can also be advantageously used for the equipment in the dlspatchers ofilce, although at such a location various forms of rotary or step-by-step switches may be adopted.

55; One object-of the-present invention is to economize in the number of relays required at the Way stations for channel circuit selection by organizing the system so that communication takes place between the dispatchers office and each one of the way stations in turn, so that the number of relays required at any station need not be more than required to select the number of channel circuits required for the controls or indications at that station alone. This station selection is accomplished in accordance with the present invention by automatically sectionalizing the line circuit, over which the impulses are sent to operate, synchronously, the channel circuit selecting equipment at the dispatchers office and at the way-stations, in such a way that the channel selecting relays at each way-station in turn, and

at only one way-station at a time, are operated by the impulses over this line circuit in synchronism with the corresponding portion of the channel selecting equipment at the dispatchers ofiice. The various functions and advantages of this sectionalizing scheme, such as isolation of channel circuits, flexibility in permitting expansion of the original installation to any desired number of stations, or channel circuits at any station, are more conveniently discussed after the invention has been explained in more detail.

Further objects of the invention are: to provide a system which is in operation only as long as controls or indications are to be transmitted; and to incorporate other desirable features and functions required of a system for handling rai1- way trafiic.

As illustrative of one specific embodiment of the invention, we have shown in the accompanymg drawings one specific organization of devices and circuits, in a diagrammatic and conventional manner, more with the object of making it easy to understand the principles and operation of the system, rather than for the purpose of showing the particular construction or arrangement preferably-employed in practice. It should be understood that this specific disclosure of the invention is merely typical or representative, and that the particular means herein shown and described is susceptible of considerable modification and adaptation without departing from the invention.

In the. accompanying drawings, Fig. 1 shows the equipment for the dispatchers ofiice; Fig, 2 the equipment for; the first way station located nearest, the. dispatchers. office; and Fig. 3 part of the equipment for another way station. These figures, when placed end toend, show in part the complete equipment, a complete system for a number of stations comprising a duplication of some of the devices and circuits shown.

Considering first the equipment in the dispatchers office, this comprises in general a suitable track diagram, with lamps or other indicators showing train movements; manually operable levers, by means of which the dispatcher may control the operation of the switches, signals, and the like at the various way stations; channel circuit selecting equipment, preferably in the form of relays, which equipment has a capacity for all the channel circuits for the whole system; a suitable power operated rotary circuit controlling device for providing the impulses of the proper polarity and direction for the functioning of the system; and devices and circuits for automatically setting the system into operation, whenever any lever is moved to a new operated position, or whenever any change takes place in train location, together with means for automatically stopping the operation of the system when all of the indications or controls have been transmitted or cleared out.

As representative of the track diagram, Fig. 1 shows the passing siding PS, with a lamp 5 located near one end, which is to be lighted when a train is present on the usual short detector track circuit at the corresponding end of the siding in the field. Of course, in practice, this track diagram will consist of a large number of stretches of track, either single or double, and passing sidings, and the like, according to the character of the portion of the railway under the supervision of the dispatcher.

As representative of the manually operated. levers, Fig. 1 shows a lever L, arranged to be moved up and down to either of two extreme positions, for the control of a power-operated switch at the end of the siding just above this lever. Another lever L movable from an intermediate or middle position shown, to the right or left, to either of two extreme positions, is typical of the type of lever preferably employed for controlling the signals at the corresponding end of the distant siding, and for selecting the direction in which traffic may be permitted to move at that end of the siding.

The levers L and L and all other levers in the dispatchers ofice, are each provided with contacts momentarily closed during movement of each lever from its existing position to some other operated position. In the simple form diagrammatically shown, a switch arm 6 is suitably connected to the lever L so as to move therewith, and engages a contact 1 momentarily as this lever is moved from one extreme position to the other. Similarly, the other lever L has connected thereto a switch arm 8, which engages one of two contacts 9 momentarily, whenever this lever is shifted from any existing position to another operated position.

These levers L and L make and break contacts, which are shown diagrammatically as arrows engaged by the lever itself. In the case of the lever L there is also a supplemental contact arm i6 engaging contacts in each of the three different positions of that lever.

As representative of the channel circuit selecting equipment in the dispatchers office, there are shown in Fig. 1 three relays l, 2 and 3, and their connected circuits. These relays provide for five momentary channel circuits which are assumed to be enough for one typical station or track location at one end of a siding. These three relays and their interconnecting circuits ing in the winding.

are duplicated to provide the number of chan nels required for the whole system. It should be understood that instead of a series of sequentially operated relays, as shown, groups of relays for channel selection in the dispatchers office may be used in the manner shown and described in the application of O. H. Dicke and F. B. Hitchcock, Ser. No. 346,731, filed March 13, 1929.

These relays as i, 2, etc., are of the polarized dead-beat type. In other words, the contact finger of these relays (shown conventionally) are moved from one extreme position to the other in accordance with the polarity of the direct current flowing in the winding of the relay, and these fingers are biased by their spring tension or otherwise so as to remain in their existing extreme position when there is no current flow- Also, the upper two contacts of each of these relays are make-beforebreak contacts, as conventionally shown by the legend make-before-break, so that as a matter of fact they break their circuits beyond the center, and may also be conventionally called break-beyond-center contacts.

The rotary circuit controlling device, as shown in Fig.1, comprises a shaft S, indicated conventionally by dot and dash lines, which is arranged to be driven by a suitable electric motor M through a friction clutch CL. As shown, it is contemplated that this motor M would be constantly operating, tending to drive the shaft S, and that the clutch CL will be slipping while the shaft is stationary and the system is not operating. Obviously, devices (not shown) might be added to provide for automatically starting and stopping the motor when the system is not in operation or idle.

On this shaft S is a contact arm l2 adapted to engage two contacts IE to complete a starting channel, but only in the initial or idle position of the shaft. The shaft also carries two other contact arms 14 and i5 engaging contact rings it and ll, so as to make up circuits during the entire revolution of the shaft, except at the gaps in these rings.

The shafts carries an arm A, arranged to engage and be held in the initial starting position shown by a gravity latch l8 released by the energization of a release magnet B. This arm A carries an electrically connected pair of contract springs i9 and 20 insulated from the arm A, one engaging the half rings 2! and 22, and the other engaging two groups of stationary contacts 23 and 24.

The equipment for automatically starting and stopping the system comprises an alternating current generator G, preferably of a relatively high frequency, such as three hundred cycles, an alternating current relay AC of suitable construction responsive to such frequency, and two relays LV and ST interconnected with and controlled by this relay AC, the momentarily closed contacts 6l, 8-9 of the levers L and L and the contact arms [4 and E5 on the shaft S, in the manner more conveniently explained in connection with the discussion of the operation.

A system of this invention requires four line wires from the dispatchers office along the track to each of the way stations. These wires are a common C, a signal or message Wire SGL, and two impulse or stepping wires, SW-| and SW--2.

In the dispatchers ofiice, are two non-biased polar relays LR and LE one included in series 10 the stepping wires SW! and SW2. For convenience and simplicity, the connections to the terminals of these batteries are marked B+ and B. There is another supply of direct current of opposite polarities, indicated by the batteries 2? and 28, for operating the channel selecting relays I, 2, 3, etc. Other circuits, indicated conventionally as terminating at plus and minus are connected to the same or an additional source, depending upon the voltage and current requirements.

Referring now to Fig. 2, which shows a typical equipmentf or a way-station, it is assumed that this way-station will be located at one end of a passing siding P, and is employed to control the operation of a suitable power operated switch machine (not shown) and the clearing of signals 3,0, 3! and 32, subject to track circuit control, and for transmitting to the dispatchers office an indication of the occupancy of the 20 usual detector track circuit, having a track relay T. The operation of the switch machine is intended to be controlled to its normal or reverse position by a dead-beat polar relay SM with suitable provisions for approach and detector locking. The clearing of the signals 3ll32, subject to track circuit control and the position of the switch, is intended to be controlled by a dead-beat polar relay SG, when in one position (to the right as shown), the clear- 4 ing of the signals for opposite directions of trafiic being determined by the position of the contact finger or armature of thedead-beat polar relay TD. The switch control relay SM, the signal ,clearing relay SG, and the traific direction relay TD are controlled over channel circuits from the dispatchefls office; and the electrical connections between these relays and the switch machines and signals take various forms, such as shown, for example, in the application of S. N.

,. 59 Wight, Ser. No. 321,185, filed November 22, 1928.

Associated with the track relay T and controlled thereby are neutral relays 33 and 3 3, for controlling the automatic starting of the system from this way station.

. .5 5 The two impulseor stepping line wires SW!,

and SW.2, are connected ateach way-station, as shown in Fig. 2, with the fingers 35 and 36 of a slow acting polar relay SL of the dead-beat type. A polar line relay LR, is connected to contacts of v these fingers 35 and 36 of the relay SL. The contact fingers of this relay LR are biased to assume the neutral position when de-energized.

,At each way-station is a bank of dead-beat polar relays, constructed like the channel circuit selecting relays l, 2, ,3, etc., in the dispatchers charged ,by rectifiers and a trickle charge alter.-

nating current line in the usual way. As shown, two batteries 31 and 38 are employed to supply current for operating the channel circuit select ing relays, these batteries having the middle tap or terminal indicated as N. Another pair of hat: teries cats are shown for providing current of different polarity and of appropriate voltage, for transmittingan' indication of track circuit conditions to the dispatchers office over the signal wire and common, these batteries having a 10 middle tap connected to the common wire C. Some of the local circuits are indicated as terminating at positive and negative v(), which may be the terminals of either of these sets of batteries, .or a separate battery, depending upon l5 the voltage and current requirements.

Fig. 3 shows part of the equipment for another way-station, which is assumed to be the Way station next adjacent to the station shown in Fig. 2, and providing controls and indications forthe 2. opposite end of the same siding. The system may be installed or extended with as many other way stations or control points as desired.

Operatio-1i.-The circuits and parts are shown in the drawings in the normal or idle condition 2. of the system, which exists when there is no control to be transmitted from the dispatchers ofiice to any way-station, nor any indication of a change in the track circuit conditions to be transmitted from any way-station to the dispatchers office. In this idle .or non-operating condition of the system, the shaft S is held stationary in the initial position shown by the latch l8 engaging the arm A. The motor M is running, and I tends to drive the shaft s through the friction 3:

, clutch CL.

The slow acting polar relay SL at the first station adjacent to the dispatchers ofiice, shown in Fig. 2, was last energized with a polarity of current, assumed to be positive, to place its cont tact fingers 35 and 35 to the right. At the next station No. 2, (Fig. 3), the contact fingers 35 and 36 were left in the left-hand position. At sta tion No. 3 the contactsof the relay SL are in the right-hand position, at station No. 4 in the left- 5 -5 hand position, and so on.

Referring to Fig. 2, it will be noted that the stepping wire SW| is connected through the finger 35 of the relay SL to the right, wires 4,3, and M, to the line relay LR, at this station, and 5. .thence to common. This stepping wire SW-.I, extending to the other stations, is broken at the fingers 1550f the relays SL. In other words, the stepping wire SW-l extends from the dis- W patchers ofiice to station No. 1, where it stops. The other stepping wire SW2, leading to the contact finger 355 of the relay SL at thefirst station, shown in Fig. 2, is carried through contact 35 of the relay SL at that station, in the right hand position and thence over to station No. 2, where it is passed on through the contact finger 35 to station No. 3, and so on. .In other words, the stepping wire SW-2 is completed through ,the relays SL at all of the stations. Putting it another way, in the normal or inactive condition of the system, as shown, one stepping wire SW is sectionalized and stops at the first station,

where it is connected to the line relay LR at that station, whereas the otherstepping wire .EiWQ continues through all of the stations. x

Automatic starting.-Tne system is automatically set into operation either upon .niovementlof anylever in the dispatchers ofiiceto a new opera atedposition, or whenatrainentersforlleaveslgn 4Z5 one of the detector track circuits and causes a change in the corresponding track relay T.

Whenever any lever is shifted by the dispatcher to a new operated position, the contacts associated with that lever, such as 6 and l for the lever L, are momentarily closed, and thereby establish a circuit for energizing the relays LV and ST. If the lever L, for example, is moved from the upper extreme position shown to the lower position, for the purpose of operating the corresponding switch machine to the other position, during movement of this lever, the contacts 6 and l' are momentarily closed and establish a circuit for energizing the relays LV and ST which may be traced, starting at plus contacts 6 and 1, wires 45, 46, 4'! and 4B, relay LV, wire 69, upper winding of relay ST. The relay ST is independently stuck up by a stick circuit through the arm l5 and ring [1, wire 53, front contact 54, wire 55, and lower winding of relay ST.

When the relay ST is energized, it establishes a circuit through its front contact 56 and wire 5'! for energizing the release magnet R, to attract the latch i8, and release arm A, so that the shaft S may rotate. The shaft S continues rotation until the release magnet R is de-energized.

During the first part of the movement of the shaft S from its initial position, the stick circuit for the relay LV and upper winding of the relay ST in series, is broken at the contact arm i4; and near the end of the revolution the stick circuit for the lower winding of the relay ST is broken at the contact arm i5. In this connection, it should be noted that the gaps in the rings l6 and ll are in staggered relation, the arm i l being in the gap of ring l6 at the beginning of a revolution and the arm [5 being in the gap of the ring I! at the end of the revolution. If any lever is operated to a new position, after the shaft S has been set into operation and at any time during its revolution, the relay LV is again energized and stuck up, maintaining the upper winding of the relay ST energized and its front contacts 5 1 and 56 closed, during the time the contact arm 15 is out of engagement with the ring 17, at the end of that revolution. Thus, the release magnet R is maintained energized, and the shaft S makes another revolution. This same operation continues until one complete revolution of the shaft S has occurred, during which no lever has been moved to a new position, whereupon the relay ST opens its front contacts just before the end of the revolution, de-energizing the release magnet R in time for the latch i8 to catch the arm A. In other words, the relays LV and ST, with this particular method of control, insure one complete revolution of the shaft S following any new lever movement, thereby assuring that the channel circuit for such lever shifted to a new position will be set up, irrespective of the point in the revolution of the arm A that the channel circuit for that newly moved lever is set up.

The system is also automatically set into operation whenever the track relay T at any of the stations is dropped or picked up. For example, when the track relay T at the first station shown in Fig. 1 either drops or picks up, its contacts 60 are momentarily closed and energize the relay 33 over wires BI and 62, the contact 63 being constructed, as indicated conventionally, so as to be closed during the movement of the armature of the relay T between its upper and lower positions. The relay 33, when energized, is maintained energized by a stick circuit including the back contact 63 of the relay 34, wire 64, front contact 65 of relay 33 and wires 66 and 62.

Whenever the relay 33 at the first station, or a corresponding relay at any other station, is thus energized, the starting channel circuit is set up between the dispatchers ofice and the way-station in question, including the alternating current generator G, which results in the energization of the relay AC. In the case of the first station shown in Fig. 2, this starting channel circuit may be traced as follows; starting at C through the front contact 6'! of the relay 33, condenser 68, adjustable choke or reactance 69, wire 50, contact H of the relay I wires 12 and 13, contact 14 of the relay 3 Wire 15, contact 16 of the relay 2*, wire 11, finger T8 of the line relay LR, in its neutral or die-energized position, wire 19 to the signal or message wire SGL to the dispatchers office, thence along wire to the relay AC, wire 8|, contacts I2 and I3, operated by the shaft S, wire 82, generator G, wire 83, condenser 84, reactance 85, and wire 86 back to the common. The condensers 68 and 84 and the reactances 69 and are so proportioned or adjusted as to provide a ready path for the alternating current provided by the generator G. These condensers of course block the passage of direct current, so that it is assured that the starting operation will occur only on account of the flow of the alternating current.

The energization of the relay AC closes its front contact 81 to supply current from positive wire 88 to the wire 41, thereby energizing the relays LV and ST in the same way as if a lever had been shifted. As soon as the shaft S starts, its arm I2 disengages its contact I3 and breaks this starting channel circuit at the dispatchers ofiice, thereby cutting off alternating current from the signal wire SGL. Also, the operation of the first relay of the channel selecting group at the way station (relay 1 for the first way station shown in Fig. 2) shifts the contact H, as hereinafter explained, to interrupt this starting channel at the station in question.

While the system is operating, trains may enter or leave the track circuits; and to assure that any such change in track circuit conditions will be indicated in the dispatchers office, it is necessary to store or retain such change, and bring about continuing operation of the system, until the indications for the particular track relay operated have been transmitted. This is accomplished by the relay 34, which maintains the relay 33 energized, irrespective of when it is operated, until the selection of channels, including the OS channel, for the corresponding station has been completed, whereupon relay 34 is energized and breaks the stick circuit for relay 33.

If, at the end of the revolution of the shaft S, when the contacts 12 and I 3 close, the relay 33 at any of the stations is energized, the alternating current starting channel circuit carries current to energize the relay AC and cause another revolution. Consequently, there must be one complete revolution of the shaft S following any change in the track circuit conditions.

Channel selection-As the arm A is rotated from the initial position shown, impulses of opposite polarity are sent out first on the stepping wire SW--|, and then on the stepping wire SW-2, so as to operate the channel circuit selecting relays l, 2, 3, etc. in the dispatchers office sequentially, and also the channel circuit selecting relays at the several way-stations in turn, the

relays I, 2*, 3 at the first station being operated to shift their contacts to the opposite position from that shown, then the relays at the next station, and so on to the end of the line,

then the relays l 2*, 3 at the first station are again operated to bring their contacts back to the position shown, then those at the second station, and so on down to the end of the line, whereupon the parts are restored to the normal condition shown and the shaft S has completed one revolution.

Since this channel circuit selecting ope-ration in the dispatchers office and at the various way stations is merely a repetition of the same oper- 1'5 ations of the relays, an explanation of the operation of setting up some of the channel circuits for the first station, and the transfer to the second station, will be sufiicient.

-To facilitate the explanation, it is assumed 0 that the fingers or contacts of the polar relays move to the right-hand position with a positive impulse, and to the left-hand with a negative impulse.

When the arm A starts from its initial position shown, its contact fingers I9 and 23 connect the first contact of the group 23 (which is connected to the negative terminal of the battery) with the half ring 2|, which is connected by wire 58 through the relay LP,I to the stepping wire SW--I This stepping wire SW-I, as previously explained, is connected to the line relay LR at the first station, but at none of the other stations. This negative impulse on the stepping wire SW--I shifts the contact 93 of the relay LE in the dispatchers ofiice to the left, and also the contacts I II] and III of the relay LR, at the first station (Fig. 2) to the left.

Considering first the resultant operation in the dispatchers ofiice, the contact 30 of the relay LE) .19 to the left connects negative battery to the wire I03, thence through contact 92 of relay I, wires I04, I05, through relay I to the neutral N. This negative impulse shifts the fingers of the relay I from the right, as shown, to the left. In the left-hand position of the finger 92, current is conducted from the wire I33, along wire I06, through contact 95 of relay 2, wires Ill! and I08, through the relay 2 to. N; but since the contacts of the relay 2 are already in the left-hand or negative position, no movement of the contacts or relay 2 occurs.

In a similar Way, movement of the contact finger III) of the relay LR at the first station (Fig. 2) applies the negative impulse over wire II2 through contact H3 of the relay SL, wire II4, contact H5 of relay I wires H5 and Ill, relay I to N, thereby shifting the contacts of relay I to the left. In the same way current is also conducted, With the contact N5 of relay i to the left, along wire H8, contact H9 of relay 2 wires I23 and I2I, relay 2*, to N, but no movement of the contacts of relay 2 occurs, since these contacts are already in the left hand position.

5 This movement of the contacts of relays I and I sets up the first channel circuit between the dispatchers office and the first station. As shown, this first channel circuit is used for transmitting the OS indication, and may be traced 70 as follows: starting at C through the deadbeat polar relay I22 controlling the OS light 5 (see Fig. 1), wire I23, contact 3? of relay 2 to the left, wire I24, contact 94 of relay I (now shifted to the left), wire I25, to the signal wire SGL,

75 thence to the first station (see Fig. 2), thence over wire 19 to the contact I8 of the line relay LR, now in the left position, wire I26, contact I21 of the relay 2 to the left, wire I28, contact I29 of relay I now shifted to the left, wire I30, to contact finger I3I of the track relay T, and thence through the batteries 39 or 40 to the common C, depending upon whether the track relay T is then picked up or dropped. If the track relay T is picked up, the contact I32 of the OS relay I22 is in the position shown, and the lamp 5 is extinguished. If the track relay T is dropped, the opposite polarity of current is supplied over this channel circuit to the OS relay I22, shifting its contact I32 to the left and lighting the OS lamp 5.

It should be understood that the speed of movement of the shaft S is such that the stepping wire SWI is energized with an impulse of negative polarity, as just described, for a time sufficient to permit the relays I and I to respond, and also, to provide sufficient time for the transmission of the indication of the occupancy or unoccupancy of the track section to the OS relay I22.

In the next position of the arm A, a positive impulse is applied to the stepping wire SW-I, shifting the contacts of the two line relays LR (in the dispatchers ofiice) and LR (at the first station) to the right. This applies the positive impulse to the wires I03, H4, and energizes the relays 2 and 2 positively, over the circuits previously explained, and causes the contacts of these relays to shift from the left to the right, thereby setting up the second channel circuit, which is used for the control of the switch machine relay SM, dependent upon the position of the lever L. This second channel circuit may be traced as follows: commencing at C, through the switch machine relay SM (see Fig. 2), wire I35, contact I36 of relay 3 to the right, wire I31, contact I38 of relay 2 now shifted to the right, wire I39, contact I8 of the relay LR, now to the right, wire I9, signal wire SGL, wire I25, contact 94 of relay I, now to the left, wire I24, contact 91 of relay 2 now shifted to the right, wire I40, contact IIJI of the relay 3 to the right, wire Hi, to the lever L, and thence to common through positive or negative battery depending upon the position of the lever L.

When the contacts of the relays 2 and 2 are thus shifted to the right by this positive impulse, as just explained, the circuit is made up over wires I42 and I43 respectively, to the next relays 3 and 3*, so that upon the next impulse, which is negative, the contacts of the relays 3 and 3 are shifted to the left, thereby setting up the third channel circuit, which is similar to those already explained, and may be traced as follows: beginning at the terminal (3+), con tact II) of the lever L wire I50, contact IIiI to the left, wire I40, contact 91 of the relay 2 to the right, wire I24, contact 94 of the relay I to the left, wire I25, message wire SGL, wire I9, contact 18 of the relay LR to the left, wire I26, contact I27 of the relay 2 to the right, wire I5I, contact I52 of the relay 3 to the left, wires I53 and I2, contact 'II of the relay I a to the left, wire I54, winding of the signal relay SG to the common return wire C connected to the mid-point of said battery.

These three impulses, first a negative, then a positive, and then a negative, cause the three relays I 2 3 at the first station in Fig. 2 to shift their contacts to the dotted position, opposite to that shown; and since, in the instance assumed, there are only three channel selecting relays at the first way station, the next operation is to transfer to the second station. This transfer is accomplished by making the last impulse, which in this case is negative, a long impulse, as indicated by the enlarged third contact of the group 23. This long impulse maintains the line relay LR. energized long enough to permit the slow acting relay SL to shift its contacts, the relay SL being energized from battery 31 through contact H! of the line relay LR and wire I44. Movement of the contact 35 of the relay SL to the left, in response to this long negative impulse, disconnects the line relay LR from the stepping wire SWl, and connects this stepping wire through the first station to the second station. At the same time, the shifting of the contact 36 of the relay SL to the left connects the stepping wire SWZ to the line relay through the wires I45 and 44. In other words, the stepping wire SW--l is now carried through the first station to the second station, while the other stepping wire SW-2 stops at the first station and is there connected to the relay LR.

Referring now to Fig. 3, it will be noted that the stepping wire SW-I is connected to the line relay LR, at that point the same as was true in the case of the first station at the time the arm A started. It will also be noted that the contacts H3 35 and 36 of the relay SL at the second station in Fig. 3 are at the left rather than at the right. It will also be noted that the normal po sition of the channel selecting relays i 5 and 6 in this station are opposite to those at the first station. Thus, even though the long negative transferring impulse is applied to the stepping wire SWi, longer than required for the relay SL to operate, and even though the line relay LR at the second station responds, its contact H0 in moving to the left applies a negative impulse to the relay i but produces no action, since the contacts of that relay 4 are already in the left hand position corresponding to such a negative impulse. This makes it possible to provide a long impulse of suficient duration to cause response of the slow acting relay SL, without causing any improper operation of the channel selecting relay at the next succeeding station.

After the transfer has thus been affected to the second station in Fig. 2, the next impulse produced by a further rotation of the arm A is positive; and this causes the contacts of the relays 4 (located in the dispatchers station but not illustrated) and l to shift in the same manner as previously explained, thereby setting up a first channel circuit, say the OS channel circuit, for this second station. The next succeeding negative impulse, shifts over the relay 5 in the dispatchers office (not shown) and the relay 5 at the second way station; and this same operation is repeated until the channels for the second way station have been set up,whereuponalong positive impulse is given to energize the relay SL at this second station, and pass on the stepping wire SWI to the next station, at the same time disconnecting the line relay LR from the stepping wire SWI and connecting it to the other stepping wire SW2.

This same operation of channel selection and transfer from station to station by long impulses continuously during the rotation of the arm A, until the last relay at the last station has responded. The arm A then is in its half-way position, and during its next movement applies positive and negative impulses via the other half ring 22 over wire M1 through the line relay LR to the stepping wire SW-2. At this time the stepping wire SW2 terminates at the first station, and is connected to the line relay LR at that station. The first impulse, being positive, restores the contacts of the relay I to the normal position shown, setting up the fourth channel circuit. The next negative impulse shifts the contacts of relay 2 to the normal position, setting up the fifth channel circuit for energizing the relay 34. The next long positive impulse shifts the contacts of the relay 3 to the normal position, leaving all of these relays now with their contacts in the normal position shown, this long positive impulse at the same time energizing the relay SL to shift its contacts back to the normal position shown, passing stepping wire SW--2 on to the next station, and sectionalizing the stepping wire SW-l at the first station. This same operation of stepping around the channel selecting relays at each station, and transferred from station to station, using the stepping wire SW-2, is carried on until the last relay at the last station has responded, whereupon the arm A has completed one revolution and one complete channel circuit selecting cycle has taken place. The switch machine relay SM when in its normal solid line position establishes a circuit to operate a suitable switch machine to the normal opsition, and. when in its dotted position establishes a similar circuit to operate the switch machine to the reverse position. Similarly, the relay SG (signifying signal control) establishes by its position clearing or non-clearing of the signals 30, 30 3| and 32, and the relay TD (signifying direction of travel) selects certain of these signals to set up the proper direction of train movement.

It will be observed that this system, as shown and described, provides for any desired number of channel circuits, but requires only channel circuit selecting relays at each station sufiicient for the channel circuits for that station only. The number of channel circuits employed at any station may be any number desired, provided that the same relative change in polarity to produce the desired transfer is maintained, in other words, an odd number of relays, as three, five, seven, etc. with any desired number of stations may be used depending upon the permissible limits of line wire, and the permissible time delay in obtaining response to a lever movement or change in track circuit conditions, it being evident that the greater the number of stations, and the greater the number of channel circuits, the longer the time intervening between setting up any given channel circuit successively, and the possible delay of response over that channel circuit. For example, if the first channel circuit of the system is, as shown, for the OS indication at, the first station, it can be readily seen that this channel circuit, after having once been set up, is not again set up until all of the other channel circuits have been set up, so that if there is a large number of stations and a large number of channel circuits, there may be a considerable delay in transmitting to the dispatchers ofiice an indication of a change in the track circuit at the first station. With these limitations, however, the system of this invention is flexible and may be originally installed or extended to take care of a large number of varying conditions. Any change in the system, after originally installed, will of course require a modification of the contact arrangement associated with the arm A, but it is not necessary to change the channel selecting equipment at the stations not effected by the change.

Another and very important advantageous feature of the system of this invention is that the line relay and the channel circuit selecting relays for only one station at a time are in operation. This not only reduces the Wear and tear on the devices, but also isolates the channel circuits at every station from all other stations. In this connection, it should be noted that the channel circuits, as previously traced, except the starting channel circuit including the condenser 68, each include the contacts 18 of the relay LR "at the corresponding station, so that no channel 7 connection is established unless this line relay manent derangement, due to sticking of relay contacts, crosses or grounds, or the like, at any station, which tends to leave an energized channel circuit connected across the signal wire and common at that station, such defect is limited to that particular station, and can not affect the proper operation at other stations, as would be the case in communication systems of the synchronous type, in which the channel circuits at the several stations are not isolated.

The channel circuits at the way-stations are connected through the contact 18 of the line relay LR in its positive and negative positions so that, upon shifting of this contact of the relay LR, the channel circuit previously made is at once broken, and remains broken in the opposite position of said COIitBlCt. Thus, even though the channel selecting relays in the disfpatchers ofiice respond before the channel selecting relays at the way-station then selected, there is no overlapping of channels, since the line relay LR at the way station, as soon as it operates, cuts off the previously existing channel. This feature is important, because with the long line wires and commercial apparatus there 7 is very likely to be some lag in the operation of the channel circuit selecting relays at that way station; and with rapid operation, if this feature were not provided, it might happen that a new channel would be set up at the dispatchers oifice while the old channel remained set up at the way station, resulting in overlapping of channels and possible false and improper control or indication. Since the line relay in the dispatchers oflice is in series with the line relay at the way station at which the channel .selection is taking place, it is assured that these line relays will be energized with the same current values and will operate simultaneously, with the result that the next existing channel at the way-station is automatically out 01f, before there is a chance for the channel selecting relay in the dispatchers oflice to be energized and respond.

In a train dispatching system, the devices 01 communication system are necessarily located at more or less isolated points along the railway track, usually in ordinary relay boxes and similar housings, where these devices are subjected to the jar and vibration of passing trains, to widely varying conditions of temperature and moisture, and also where it is impossible to make repairs or adjustments promptly. In other words, the way-station equipment for a dispatching system must operate under very unfavorable This invention makes it possible to use such simple relays, and still obtain the necessary num ber of channel circuits, without using an objectionable or prohibitive number of relays in the various stations.

For the purpose of explaining the nature of this invention, we have shown and described one specific organization of devices and circuits, with out attempting to illustrate or explain how other equivalent devices or circuits might be employed to accomplish the same function or result in accordance with this invention; and it should be understood that various modifications, adaptations, and substitutions, may be made in the specific embodiment of the invention herein shown and described, without departing from the the dispatchers ofiice and one at each station, 7

means for establishing a communication circuit including the line relay in the dispatchers office and the line relay at one only of the several stations in turn, and selecting means at each station controlled by the line relay at that station,

said selecting means at the several stations being operated only one at a time.

2. In a train dispatching system, a dispatchers oince, a plurality of stations, railway traff c controlling devices at each station, a line relay in the dispatchers office and one at each station, means for establishing a communication circuit including the line relay in the dispatchers office and the line relay at one only of the several stations in turn, and a group of relays at each station energized from a local source of current in response to operations of the line relay at that station for establishing circuits to control said traffic controlling devices at that station.

3. In a train dispatching system, a dispatchers office, a plurality of stations, railway trafiic controlling devices at each station, a line relay at each station, impulse means in the dispatchers office, and means operating automatically to connect said impulse means to the line relays of the several stations only one at a time, and a group of relays at each station controlled by the line relay at that station in response to the impulse applied thereto, said relays establishing in sequence a plurality of channel. circuits each including contacts of the line relay at that station closed upon energization thereof, whereby the channel circuits are completed only at one station at a time where the line relay is being operated.

4. In a train dispatching system, a dispatchers office, a plurality of stations, railway traffic controlling devices at each station, a line relay at each station, selecting means at each station governed by the line relay at that station, a stepping line wire extending from the dispatchers oflibe along the track and divided into sections terminating at each station, and means at each station controlled over said line circuit from the dispatchers oifice at times connecting the line circuit to the line relay at that station and at other times disconnecting said line relay and connecting together the sections of the line circuit at that station.

5. In a train dispatching system of the character described, the combination with a dispatchers ofiice and a plurality of stations, railway trafiic controlling devices at each station, impulse responsive means at each station for selectively establishing circuits for the control of said traffic controlling devices, a line relay at each station for governing said impulse responsive means at that station, a line wire extending from the dispatchers office along the track and having contacts therein at each station, said contacts when in one position making a break in said line wire at that station and connecting the end nearest the dispatchers office to the line relay at that station, said contacts in another position disconnecting said line relay at the operation of railway traflic controlling devices to govern train movements on railroads, the combination with a dispatchers office and a plurality of stations, of a line relay at each station, a line wire extending from the dispatchers oifice along the track, a polar relay at each station having contacts in said line circuit, said contacts in one position interrupting the line circuit at that station and connecting it to the line relays for that station, said contacts in another position disconnecting said line relay at that station and making the line wire continuous through that station to the next station, selecting means at each station operated by the corresponding line relay, and means for operating said polar relays at the several stations one at a time,

'7. In a train dispatching system of the character described, a dispatchers office, a plurality of stations, railway trafiic controlling devices at each station, a group of relays at each station, a line relay at each station operating the corresponding group of relays sequentially to set up channel circuits for the controlling of the traffic controlling devices at that station, and means for operating said line relays from the dispatchers office one at a time.

8. In a dispatching system of the character described, a dispatchers office and a plurality of stations, a line relay in the dispatchers office and one at each station, means including a polar relay for connecting the line relay in the dispatchers office series with the line relays at the several stations one at a time in sequence, and selecting means at each station operated by the corresponding line relay.

9. In a dispatching system of the character described, a dispatchers ofiice, a plurality of stations, a line circuit extending from the dispatchers ofiice along the track and divided into sections terminating at said stations, and means at each station operated automatically from the dispatchers office in response to an impulse of one character over the line circuit to connect the sections of said line circuit at that station and to disconnect said sections in response to an impulse of another character.

10. In a dispatching system of the character described, a dispatchers office, a plurality of stations, a line circuit extending from the dispatchers office along the track, a line relay at each station, a polar relay at each station operating in response to an impulse of one polarity over the line circuits from the dispatchers office to make a break in said line circuit at that station and also connect the line circuit leading to the dispatchers office to the line relay at that station, said polar relay operating in response to an impulse of the opposite polarity to disconnect the line relay at that station from said line circuit and close said break to extend the line circuit to the next station, and means in the dispatchers ofiice for applying an impulse of said one polarity and also impulses of said opposite polarity of a number corresponding to the number of stations.

1].. In a train dispatching system, a communication system of the synchronous type employing a line circuit comprising a signal line wire and a common wire, channel circuit selecting means in the dispatchers ofiice and at each station operable synchronously to establish in sequence channel circuits between the dispatchers office and said stations over said common and signal wires, said channel circuits being energized with direct current to transmit controls or indications, impulse means in the dispatchers office normally at rest for operating said channel circuit selecting means, and means for starting said impulse means into operation operated by alternating current flowing in said signal wire and common wire.

12. In a communication system for the remote control of trafilc controlling devices on railroads and for the transmission of indications from several way stations on the railroad to a dispatchers office, normally inactive means for establishing in rapid sequence a series of channel circuits between said dispatchers office and the way stations, said channel circuits including a message wire and a common wire, means for normally holding said communication system at rest, a starting circuit rendered available when said system is at rest, initiating means in said starting circuit, and means for causing the flow of alternating current in said starting circuit to operate said initiating means when an indication is to be transmitted from the way station.

13. In a centralized trafiic controlling system for railroads; the combination with a central office and a plurality of way stations, a line relay at each way station, a first line wire section connecting said central ofi'ice to the first way station, a second line wire section connecting said first way station to the second way station, a message wire connecting said central office and all of said way stations, means at said central office and at said way stations for closing a large number of message circuits each including said mesage wire sequentially and controlled by apparatus at said central station and the line relays at said way stations, station selecting means at each way station for disconnecting the line re- 1y at said way station and connecting the line wire section toward the rear to the line wire section in advance, and means for returning said station selecting means to its normal condition.

14. In a centralized traflic controlling system for railroads; the combination with a central office and a plurality of way stations, a line relay at each way station, a first line wire section connecting said central ofiice to the first way station, a second line Wire section connecting said first'way station to the second way station, a message wire connecting said central ofiice and all of said way stations, means at said central oifice and at said way stations forclosing a large number of message circuits each including said message wire sequentially and controlled by apparatus at said central station and the line relays at said way stations, time measuring station selectingmeans at each way station for disconnecting the line relay at said waystation and connecting the line wire section toward the rear to the line wire section in advance, and other sections of line wires connecting the first way station to the central office and .each way station to the next more distant way station for returning said station selecting means back to its normal position.

15. In a centralized trafiic controlling system for railroads; the combination with a central ofiice and a plurality of way stations, a line relay at each way station, a message circuit connecting said central ofiice and all of said way stations, one line circuit divided into sections each section connecting two adjacent way stations, another line circuit also divided into sections each connecting two adjacent way stations, a line relay at each way station, time measuring two position means at each Way station for either connecting the line relay at such way station to said one line circuit and connecting the adjacent sections of said another line circuit together or connecting the line relay at such way station to said another line and connecting the adjacent sections of said one line circuit together, whereby the line relay at each way station may be individually connected to either said one or said another line circuit and a railway signal at each way station controlled over said message wire through the medium of said line relays.

16. In a centralized traffic controlling system for railroads; the combination with a central ofiice and a plurality of way stations, a line relay at each way station, a message circuit connecting said central oflice and all of said way stations, one line circuit divided into sections each section connecting two adjacent Way stations, another line circuit also divided into sections each connecting two adjacent way stations, a line relay at each way station, time controlled two position means at each way station for either connecting the line relay at such way station to said one line circuit and connecting the adjacent sections of said another line circuit together or connecting the line relay at such way station to said another line and connecting the adjacent sections of said one line circuit together, and means for effecting successive operation of said two position means to cause the line relays of said way stations to be successively connected to said one line wire and then successively connected to said another line wire and a railway signal at each way station controlled over said message wire through the medium of said line relays.

17. In a centralized traffic controlling system for railroads, the combination with a central oifice and a-plurality of way stations, a message circuit connecting said central office and all :of said Way stations, 'a stepping circuit, means 'for applying long and short impulses to said stepping circuit, and means at each way station responsive to said impulses to establish "a large numberof message circuits sequentially each including said message wire, said :long impulses selecting particular 'way stations: Zanjda said, short impulses including aaparticularicontrol relay at such selected way station in a particular message circuit at a particular time, and traflic controlling apparatus controlled by said control relays.

18.Ina centralized :traflic controlling system for railroads, a control oflice, aiplurality'of field stations, a line circuit connecting said control ofiice andsaid field stations, means at saidcontrol ofiice for impressing -a series of impulses having long or short positive and negative characters on said line circuit, station selecting means at each station selectively responsive to the characters ofysaid impulses, and .means at each station governed in accordance with the characters of said impulses after that station: is selected by its respective station selecting means.

19. In a centralized traffic controlling :system for-railroads; a control ofiice; aplurality'offield stations, each of said stations having a plurality of traffiocontrolling devices; a lineicircuittconnecting said control office and said field stations; means at said control oifice for impressing a series of impulses on said line circuit, said=series of impulses having long or short positive and negative characters; and means responsive to the characters of said impulses for selectively and successively rendering said trafiic controlling devices 'governable one at a time from said contro oflice.

20. In a centralized tra'fllc controlling system for railroads; a control ofiice; a plurality of field stations, each of which has .a plurality of traffic controlling devices; a. line circuit connecting said control office and said plurality of field stations; means at said control ofiice for impressing a series of impulses having'longorshort positive and negative characters .on said line circuit; station selecting means at each station selectively responsive tot-he character of some of said impulses for rendering said stations selected only one at a time; and means at each station operated by certain others of said impulses after that station isselected by its respective station selecting'means to render said trafiic controlling devices governable one at a time from said control ofiice.

21. In a centralized traflic controlling system for railroads; a central ofiice; a "field 1-station; normallyat rest step-by-step means at said central ofiice and at said field station; means'for operating said step-by-step means in synchroe nism, when initiated, for sequentially closing a plurality of channel circuits for transmitting messages between said central ofice and said field station; initiating means at said field station for initiating said step-by-step means into operation when there are new messages to be transmittedpfrom saidsfieldstation to said control omce and means for rendering said initiating means ineffective to initiate said stepeby-step means after said new messages have beentrans mitted only if said step-by-step means =are-still in synchronism.

22. In combination a first line wire connecting an office anda station, a movable device at said station, a normally deenergized relay at thestation, means operating in response ,to a change in theposition of said device to delivera starting impulse to said first line wire over a back contact of said relay, asecond line wire connecting said oflice and station, means at the office responsive to said starting impulse'for delivering another impulse -tosaid second line --wire forenergizing said relay, means "operating "when said re'lay is energized maneuver-an indication impulse to "the first line wire under the control of said device, and means at the ofiice selectively controlled by said indication impulse. r

23. In combination with a first line wire connecting an oflice and a plurality of stations, a series of movable devices at least one located at each station, a plurality of transmitting equipments one for each said device, means set into operation by a change in the position of any particular device for actuating the transmitting equipment associated with the first device of said series, means operating when any transmitting equipment is operated to deliver to said line wire an indication impulse under the control of the corresponding device, indication means at the office selectively responsive to each said indication impulse, and means located partly at the office and operating when any transmitting equipment preceding said particular device in said series is actuated to actuate the succeeding transmitting equipment.

24. In combination with a first line wire connecting an office and a plurality of stations, a series of movable devices at least one located at each'station, a plurality of transmitting equipments. one for each said station, means set into operation by a change in the position of any particular device for any station for actuating the transmitting equipment associated with the first device of said series, means'operating when any transmitting equipment is operated to deliver to said line wire an indication impulse under the control of the corresponding device, indication means at the oflice selectively responsive to each said indication impulse, and means at each station operated upon completion of operation of the transmitting equipment at that station to cause actuation of the transmitting equipment at the succeeding station. r

25. In a remote control system comprising an oifice and a series of stations connected by a line wire, a selector at the office, a selector at each station, means for synchronously operating the selectors at the ofiice and at each station comprising apparatus for transmitting a group of impulses from the office to one of said stations over said line circuit to actuate the selector at said one station in synchronism with the ofiice selector, a contact at each station for switching said line circuit extending to the office from said station tothe'next station at the completion of said groupfof impulses, and means for transmitting a group of impulses from the ofilce to said next station to actuate the selector at said next station in synchronism with the office selector, and means at each of said stations to initiate the operation of said ofilce selector to effect the operation of all of said station selectors in se- 26. In a centralized trafiic controlling system indication of such change of the-device at that station tos'aid ofiice, and'means ateach station for setting the selector apparatus for the next station into operation totransmit an indication to the ofiice to indicate the condition of the next succeeding station device.

27. In a remote control system including an office and a plurality of stations, a selector comprising a chain of counting relays at said office, a second selector comprising a chain of counting relays of which certain ones are at each of said stations, said selectors being normally deenergized and adapted when operated to close a series of contacts in sequence and to close corresponding contacts of different selectors simultaneously, means for transmitting impulses from said office to each of said stations in turn to operate said contacts in sequence, means controllable from said office or from any of said stations for initiating operation of said means; and means at each station for controlling devices at such station over circuits including contacts of the associated selector.

28. In a train dispatching system, a control ofiice, a plurality of field stations located at difierent distancesfrom the control office, a line wire having contacts therein at each station to form sections extending from station to station, said contacts at each station connecting sections of the line wire extending toward the control office either to said relay at that station or to the line wire section extending to the next station more remote from the control oifice, a line relay in the control office and a line relay at each station, and means including said line Wire for operating said contacts at said stations in turn only one at a time, whereby line circuits each including in series the line relay in the control office and the line relay at the corresponding station are established by the control office and one station only at a. time.

29. In a train dispatching system, a control ofiice, a plurality of field stations located at difierent distances from the control office, a common Wire, a line wire section extending from the control office to the'first station nearest the control ofiice, other line wire sections extending from station to station, means for connecting together said line wire sections to establish line circuits comprising, said common wire and sections of said line wire, said line circuits extending from the control 'office to each of said stations one at a time only, a relay in the control ofiice, a relay at each station, each of said line circuits including the relay in the control'office and the relay at the one particular station to which the line circuit then extends, and means including said line circuits and said relays for transmitting controls from the control office to the several field stations and indications from the field stations to the control oifice.

30. In a system of the character described, a control office, a plurality of stations, a line relay in the control office, stepping relays in the control oiiice-energized sequentially in response to the energization of said line relay, manually operable levers in the control oflice, partial circuits controlled'bysaid levers and selectively established by said stepping relays, a line relay at each field station, a common wire extending from the control oflice through the several stations, a line wire divided into sections extending from the control oifice to the nearest station and from station to station, means for connecting said line wire sections together to establish line circuits extending from the control office to each station in turn one station at a time only, said line circuits including in series the line relay in the control ofiice and the linerelay at'the corresponding station, control relays at the stations to be governed in accordance with the positions of said levers, a message line circuit connected to said partial circuits in the control office, and means at each station controlled by said line relay at that station for connecting the control relay at that station to said message circuit.

31. In a communication system of train dispatching, a control oflice, a plurality of field stations located at different distances from the control office, a line relay in the control ofiice, a line relay at each station, a line wire divided into sections extending from the control office to the nearest station and from station to station, a transfer relay at each station having contacts for connecting the line wire section extending toward the control office, either to the line relay at that station or to the line wire section extending to the nearest station more remote from the control office, means for energizing said transfer relays successively to establish line circuits extending from the control ofiice at each station in turn only one station at a time, said line circuits including in series the line relay in the control ofiice and the line relay at the corresponding station, and means including said line circuits and said line relays for transmitting current impulses between the control oflice and the several stations for controls and indications.

32. In a system of the character described, a control office, a plurality of field stations located at difierent distances from the control ofiice, a

line wire divided into sections and extending from the control ofiice to the nearest station and from station to station, a line relay at the control oflice, a line relay at each field station, impulsing means in the control office operable to apply time-spaced current impulses to said line wires, means at each station responsive to said impulses for alternately connecting the line wire section extending to that station to the line relay at the station and then to the line wire section extending to the next station more remote from the control office, whereby the line relay in the control ofiice is connected in series with the line relays at the several stations successively only one at a time, indication means in the control oflice, devices at the field stations having contacts operated in accordance with their operated conditions, a message circuit extending from the control oflice to the several stations, means including said line relays for connecting said indication means in the control office in turn one at a time to the contacts of the corresponding device in the field over said message circuit, and means for initiating operation of said impulsing means from any one of said stations upon a change in the operated condition of said device at that station.

33. A system of the character described, a control ofiice, a plurality of stations at different distances from the control ofiice, a common wire, a line wire divided into sections extending from the control ofiice to the nearest station and from station to station, a line relay in the control ofiice, a line relay at each station, impulsing means in the control ofilce for applying to said line wire time-spaced current impulses, means at each station responsive to the energization of the line relay at that station for disconnecting the line wire section extending toward the control ofllce from that line relay and connecting that line wire section to the line wire section extending to the next more remote station, whereby said line circuits comprising said common wire and sections of said line wire are established between the control oflice and each of said stations in turn only one station at a time, said line circuits including the line relay in the control ofiice and the line relay at the particular station then connected to the control ofiice, means including said line relays for transmitting current impulses between the control o-flice and the several stations for controls and indications, and means for initiating operation of the said impulsing means either in the control office or from any one of the several field stations.

34. A railway traflic indicating system comprising an ofiice and a plurality of stations at spaced locations along a railroad and connected by a single line circuit, synchronous selectors at the oifice and at each of said stations adapted to be controlled over said line circuit, a plurality of devices at least one at each of said stations, means responsive to a change in position of any station device to initiate the operation of each of said station selectors one at a time in turn in synchronism with said office selector in a single cycle of operation, and means controlled by said synchronous selectors to indicate the condition of each of said station devices at said oflice during said cycle.

35. A synchronous selector remote control system comprising a stepping line and a message line, a line relay in said stepping line, a chain of counting relays arranged to be energized one at a time in sequence as said line relay is actuated repeatedly, a series of control circuits, one for each alternate counting relay, each including one of said lines and a contact of the corresponding counting relay, a series of indication circuits, one for each intervening counting relay, each including one of said lines and a contact of the corresponding counting relay, means for transmitting distinctive control impulses over each of said control circuits, and means for transmitting distinctive indication impulses over each of said indication circuits, whereby control impulses and indication impulses are alternately transmitted.

36. In a centralized traffic controlling system for railroads; a line circuit connecting a control oifice and a plurality of field stations; a plurality of traflic controlling devices at each of the field stations; means for impressing a series of positive and negative impulses of long and short duration on said line circuit; and means at each field station selectively responsive to the composite positive and negative, long and short characters of said impulses for rendering said traffic controlling devices successively governable one at a time from the control oflice.

37. In a centralized traffic controlling system for railroads; a control office; a plurality of field stations; a line circuit connecting said control ofilce and field stations; means for impressing a series of positive and negative, long and short impulses on said line circuit; and means at each of said field stations selectively responsive to the composite positive and negative, long and short characters of said impulses for determining which one of said stations is to be in communication with said control omce at any one time.

NEIL D. PRESTON. OSCAR H. DICKE.

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