US2170141A - Centralized traffic controlling system for railroads - Google Patents

Description

Aug. 22, 1939.

w. D. HAILES El AL 2,170,141

CENTRALIZED TRAFFIC CONTROLLING SYSTEM FOR RAILROADS 8 Sheets-Sheet 1 Filed March 31, 1951 INVENTORS WD. Haile: and D. FIDeL Lon;

' BY MM m their A oRN'EY FIG. 1. B.

Aug. 22, 1939. w. D. HAILES ET AL CENTRALIZED TRAFFIC CONTROLLING SYSTEM FOR RAILROADS Filed March 31, 1931 8 Sheets-Sheet 2 INVENTOR5v .Hmiles and DFDe Long their ATTORNEY I Aug. 2 2, 1939.

F IG. LC.

w. D. HAILES ET AL 2,170,141

CENTRALIZED TRAFFIC CONTROLLING SYSTEM FOR RAILROADS Filed March 31, 1951 8 Sheets-Sheet 5 INVENTORS WDHaJ/es and DeLang BY M then- ATTORNEY w. D. HAILES ET AL ,170,141

Fild Marh 51, 1951 8 Sheets-Sheet 4 INVENTORS W.DHa.iles and .DFDeLO BY MM @4022 their ATTORNEY CENTRALIZED TRAFFIC CONTROLLING SYSTEM FOR RAILROADS.

A Aug. 22, 1939.

Aug. 22, 1939. w. D. HAILES ET AL CENTRALIZED TRAFFIC CONTROLLING SYSTEM FOR RAILROADS Filed March 51, 1951 v 8 Sheets-Sheet 5 M23 MQQWWMZ INVENTORS WDHaJ/es and DFDe L ng their ATTORNEY Aug. 22, 1939. w. D. HAILES ET AL CENTRALIZED TRAFFIC CONTROLLING SYSTEM FOR RAILROADS 1931 8 Sheets-Sheet 6 Filed March 31,

INVENTORf)- WDHai/ea and .DFDe Lon gv BY WM their ATTORNEY 1939- w. D. HAILES El AL 2,170,141

CENTRALiZED TRAFFIC CONTROLLING SYSTEM FOR RAILROADS Filed March 31, 1951 8 Sheets-Sheet 7 M23 zghmm 20228 M/ SQ u a mm #Q E Mm mm R a m E e [H .m H m m. R w w I. h S m VRw mi m3) ZSKvRm Qumil kmJ MDHHIQ JOQFZ 00 Aug. 22, 1

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Filed March 31, 1931 8 Sheets-Sheet 8' TYPICAL OPERATION CHA 12T i10 of ste 'Fii-sz .sre Second .ste

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Incoming I P relay conditioned held conditioned held conditioned PR, relay up I conditioned held conditioned held M relay down conditioned held conditioned held 51 relay up up and held 5:532:13; held 3:32:12; t

INVENTOR5 Haile: and D. FDe Long their ATTORNEY :operated; and the various signals :tion of N. D. Preston et al., -May 24, 1930, now U. S. Letters Patent 2,129,183 igranted Sept. 6, 1938, permitting the operator to exercise his supervisory control over the operation switches and signals Patented Aug. 22, 1939 UNITED STATES PATENT OFFICE OENTRALIZED TRAFFIC CONTROLLING SYSTEM FOR RAILROADS William D. Hailes and ester, N. Y.., assignors Darrol F. De Long, Kochto General Railway Sig- This invention relates to centralized trafiic control systems for railroads, and more particularly pertains to the communication part of such a system, by means of which an operator is able to govern traffic controlling devices at various points along a railroad, and is informed of the progress of trains and the operated conditions of the traflic controlling devices.

a A centralized trafiic control system, generally speaking, is employed to enable the operator to govern train movements, over that portion or territory of a railroad which is under his supervision, by causing operation of the switches and signals at various points in this territory, soas to permit trains to move in any way he may desire. In such a system, the various track switches are usually operated by power, under the control of the operator, with suitable provision for local approach locking and the like, so that the switches may not be improperly and unsafely are automatically controlled in accordance with traffic conditions and the positions of the switches, as is usual with automatic block signalling practice, subject to the control of the operator, who may hold any signal at stop, regardless of the automatic control, or may allow any signal to clear, provided the location of trains makes it safe for such signal to be clear.

In other words, the centralized trafiic control system contemplated by this invention may be said to comprise a communication system, such for example as disclosed in the pending applica- Ser. No. 155,304 filed of the switches and signals, together with a suitable signalling system, such for example, as dis- .closed in the pending application of S. N. Wight,

3, 1926, now U. S.

Ser. No. 120,423, filed July 7 Letters Patent 2,082,436, granted June 1, 193"],

providing the necessary block signal and interlocking protection, so that the operator can direct the movement of trains by the indication of signals without written train orders.

The present invention relates more particularly to improvements in the communication part of such a system, whereby increased facility is obtained in the operation thereof and in adaptation of such a system to problems of practice.

1 In practice, it may happen that the track located throughout the territory under thesupervision of the operator, may

be unevenly distributed so as to make it con venient for certain of these trafilc controlling devices to be grouped together to comprise a field station, which devices are preferably operated or controlled from the same field station equipment. In a communication system of the -5 coded duplex type, communication is established between the controloifice and the several field stations along the railroad over a comparatively small number of line wires, by utilizing special combinations of current impulses in the form of a code to select the stations one at a time, and/or register the several field stations, one at a time,

in the control oflice. After the selection or registration of a particular field station, communication is then held between that station and the 5 control ofiice.

One function of the system, after the selection of a particular station, is to enable the operator to condition at will a relay or similar control device for each switch or signal at such selected '20 station, in such a way that each switch may be shifted 'to' either position, and each signal caused to indicate clear or stop, as may be desired by the operator, subject to the control of the signalling system, which prevents the switches and signals being unsafely operated. This function of thesystem may be referred to as the transmission of controls.

One function of the system, after registration of a particular station, is to transmit indications .30 of the existing operated positions or conditions of the switches and signals, and the presence or absence of trains on various track circuits, to- .gether with indications of such other conditions as may be of value to the operator. This func- .tion' ofthe system may be referred to as the transmission of indications.

Although a coded duplex type communication 'system is preferably provided to transmit a particular number of controls and/ or indications for 40 each cycle of'operation, it may happen that a greater number of track switches and other trafiic controlling devices are located at certain field stations, than can be adequately handled by a single field station equipment during the same cycle of operation.

In view of this, it is proposed, in accordance with the present invention, that the traffic controlling devices at such stations-be divided into groups with the system so organized as to be able -.50 to transmit the number of controls or indications associated with any particular group during a single cycle of operation. In other words,

a field station may be said to be comprised of a single group of controls and/or a single group of v66 indications, or a plurality of such groups. With the communication system of the duplex coded type, either the groups of controls are transmitted, one group at a time for each cycle, and simultaneously therewith the groups of indications are transmitted, one group at a time for each cycle, or the control and indication groups are transmitted separately, one group at a time for each cycle. This function of the system to distinguish between the groups of controls and indications of a field station may be conveniently termed group selection, and isaccornplished after the selection of the field station bythe transmission of a code characteristic of the particular group of the station with which communication is to be held. r a

In a selective type communication system where the step-by step mechanisms are synchronously operated from a control office .by im.- pulses transmitted over a stepping circuit, and a message or .indication circuit is employed to transmit indication impulses from any particular field stationto the control office on each step, such for example as in the coded duplex system disclosed in the above mentioned application of N. D. Preston et al., Ser. No..455,-304, nowrU. S. Letters Patent 2,129,183 granted Sept. 6, 1938, the step-by-step mechanism must respond to a particular impulse on the stepping circuit before the message circuit can be conditioned to transmit the indication for the corresponding. step.

The present invention provides means, so that the condition to be transmitted for each stepis set up on. the preceding:step, with this condition made efiective ,to condition the message circuit immediately upon the application of an impulse to the stepping circuit and simultaneously with the operation of the step-by-step mechanisms. This feature of the present invention serves to decrease the time period required for each step.

A further object of the inventionis to provide a communication system of the selective type, which is normally at rest, but which may be initiated into operation by a change in indication conditions at any one or all of the several field'stations, with provisions made so that the operator. may suppress or prevent certain field stations from thus initiating the system for registration in the control office, whenever he may desire.

A further object of the invention is'to provide a communication system of the selective type having four neutral lines for accomplishing the selective control, whereby the system is made more immune to inductive surges due either from operation of the system or from external causes.

A still further object of the invention is to provide a communication system of the selective type having two lines for accomplishing the selective control. This feature of the invention is accomplished by having a direct current polarized control circuit with an alternating current message or indication circuit superimposed thereon.

Other objects, purposes and characteristic features of the present invention will be in part obvious from the accompanying drawings, and in part pointed out as the description of the invention progresses.

In describing the invention in detail, reference will be made to the accompanying drawings, in which similar parts throughout the several views are designated by like reference characters provided with distinctive exponents, and in which-- Figs. 1A, 1B, 1C and 1D,..when arranged with Fig. 1B beneath Fig. 1A, with Fig. 1D beneath Fig. 1C, with Figs. 1A and 1C placed end to end, and with Figs. 1B and 1D placed end to end, illustrate the apparatus and circuits for the control ofifice of a communication system constructed and arranged according to the present invention;

Figs. 2A and 2B when placed end to end illustrate the equipment of a typical field station having a distinctive code call, with its controls and indications'divided into several groups, each group of which is provided with a distinctive code call for its selection;

Fig. 3 shows the arrangement of line circuits as modified according to the present invention to provide a system having four neutral lines;

Fig. 4 shows the arrangement of line circuits as modified according to the present invention to provide a system having two line wires; and,

Fig. 5 shows a Typical Operation Chart which gives in a graphic form the sequence of operation of certain relays in the system.

For the purpose of explaining the nature of the present invention, there has been shown in the accompanying drawings one typical embodiment of the invention illustrated as controlling a single track switch and its associated signals; but the same principles and functions of the invention, and the same apparatus and circuits may be employed, or may be readily adapted by obvious modifications, for the control of the switches, signals, or other traffic controlling devices for all kinds of track layouts, and for receiving such indications of the positions or conditions of these trafiic controlling devices, track circuit occupancy and the like, as may be desired.

For the purpose of simplifying the illustration and facilitating in the explanation, the various parts and circuits constituting the system of the present invention have been shown diagrammatically and certain conventional illustrations have been employed, the drawings having been made more with the purpose of making it easy to understand the principles and mode of operation of the system, than with the idea of illustrating the specific construction and arrangement of parts that would be employed in practice. Thus, the various relays and their contacts are illustrated in a conventional manner and symbols are used to indicate connections to the terminals of batteries or other sources of electric current, instead of showing all the wiring connections to these terminals.

The communication system of the present invention may be said to comprise a control ofiice conveniently located with respect to the territory under supervision, and a plurality of field or way stations distributed along the railroad at convenient points. Each of the several field stations is connected to the control ofl'lce by three line wires (in the form shown in Figs. 1A, 1B, 1C, 1D, 2A and 2B namely, a stepping and control line, a message or indication line, and a common return line. These line wires are connected together so as to complete two separate circuits with a common return connection which circuits include each of the field stations and control ofiice. These circuits are conveniently termed a stepping circuit and a message circuit.

In the form shown in Figs. 1A, 1B, 1C, 1D, 2A and 2B, the stepping circuit accomplishes two functions, namely, that of operating the step-bystep mechanisms, and that of controlling the switches and signals. These two functions do not need to be combined or executed over the same circuit, but may be provided with individual circuits me. similar manner as shown in Fig. 3 of the accompanying drawings, later to be explained.

The stepping and control line circuit includes at each field station, and at the control oifice, a polar line relay L which is of the three position biased to neutral type; and the message line circuit includes at each field station and at the control oflice, a message relay M of the neutral type. At each field station two neutral contacts respectively operated by a neutral pulsing relay 1? and a neutral pulsing repeater relay PR are also included in the message line circuit.

The stepping and message circuits are supplied with direct current from suitable sources located in the control oflice, and represented by batteries BT and BT respectively. The field stations do not supply current to any of the line circuits of the system. This supply of direct current for the line circuits may be storage batteries with suitable trickle charge or periodic charging means, motor generators, or any other suitable source of electrical potential. It is to be understood, that the voltage required from these sources will vary with the length of line wire, the size of the line wire, and the resistance of the relays included in the circuits, with the particular values ascertained in accordance with the usual engineering practices.

Sources of direct current are required at the control oflice and at each of the field stations for supplying energy to the circuits local thereto, such as for the operation of the switches, signals and other devices at the particular location. Storage batteries, maintained charged through rectifiers from a suitable power line, are preferably employed for this purpose, in accordance with common practice.

Although the line circuits have been shown as supplied with energy from suitable battery sources, local circuits have been designated as supplied with energy from battery sources indicated by symbols. The symbols and are employed to indicate the positive and negative terminals respectively of a suitable battery or other source of direct current; and the circuits with which these symbols are used, always have current flowing in the same direction. The symbols (3+) and (B) indicate connections to the opposite terminals of a suitable battery or other direct current source which has a central or intermediate tap designated (CN) and the circuits with which these symbols are used, may have current flowing in one direction or the other depending upon the particular terminal used in combination with the intermediate tap (CN).

All of the operations of this communication system (as shown) are performed by relays; pref- V erably of the tractive armature type. Certain of these relays, such as the line relays L, are of the three position biased to neutral polarized type. When such a polar relay is energized, its armature is shifted from its biased-to-neutral deenergized position to an operated position, in one direction or the other, according to the polarity of the current supplied to the windings of the relay. The contacts of these three position-polar relays are shown conventionally, and for convenience it is assumed that the contact fingers of these relays are moved to the right by the application of positive current, and to the left by application of negative current, when the left hand terminals of these relays are taken as the points of application.

Certain other of the relays, employed throughout the system, are of the two position polar magnetic stick type, the armature of each relay being held by the magnetic attraction :of the permanent magnet incorporated within the relay, in the position to which the armature was actuated upon the last energization of the windings of the relay. The contact fingers of these two position polar relays are similarly conventionally shown, and are also assumed to be moved to the right by an application of positive current and to the left by an application of negative current, when the left hand terminals of these relays are taken as the points of application.

The various other relays employed throughout the system and shown conventionally, are preferably of the neutral armature type commonly used in telephone practice. Some of these relays require two independent windings; and some need slow releasing characteristics, which is obtained in the usual manner by the provision of short circuit windings. It is to be understood that all of the relays are of course constructed in accordance with recognized practice to have the necessary operating characteristics, quick operation of all the relays except the slow releasing relays being desirable to increase the speed of operation of the system. The slow releasing relays have been conventionally designated by heavy base lines, although such designation merely indicates a relative degree of speed of operation with respect to the other relays employed in the system.

Both at the control office and at the field stations certain code jumpers have been illustrated as full line connections between two terminals, when they are connected in active positions placing positive potential on the associated buses; while certain others of these code jumpers have been illustrated as dotted line connections between two terminals, when they are connected or located in inactive positions, so as to leave the associated buses deenergized.

The control oflice equipment.-The equipment for the control oflice comprises a suitable control machine which is provided with manually operable levers, indicating lamps, indicating bells, track diagrams, automatic recorders, and various other devices which may be employed to advantage, so as to enable the operator by simple manipulation to control the switches, signals, or other traffic controlling devices. of the system at the various field stations, and also have before him such information of the response of these traffic controlling devices, and of the occupied or unoccupied condition of the various track sections, as will make possible the most efficient movement of traffic.

Neither all of the parts, nor a specific arrangement of the parts of the control machine have been shown; but certain control levers, relays, indicating lamps, and various electrical connections therefor, have been shown diagrammatically as typical or representative of what can be suitably employed in a control machine in accordance with the communication system of the present invention.

In the diagrammatic arrangement shown (see Fig. 1A), a control lever SML, movable to either of two positions, and operating contacts iii and II, is illustrated for the control of a single track switch. Similarly, a signal control lever SGL, movable to any one of three different positions,

and operating contacts I2, l3 and I4, is illustrated These two control levers SML and SGL are representative or typical of those used for other switches and signals, or other similar trafiic controlling devices. v

For each field station, a cut-out control lever COL, movable to either of two positions, and operating contacts l5 and IE5, is illustrated for governing the corresponding field station to prevent or allow that station to initiate the system and transmit indications, as may be desired. Such station cut-out control levers COL may be located on the control panel adjacent the switch and signal control levers. (as shown), so as to be easily manipulated by the operator; or may be located on a separate panel adjacent certain associated relay cabinets, so as to be operated only by a maintainer in the event that a station for one reason or another falsely monopolizes the message circuit.

Although levers have been shown for the control of their respective contacts, other similar mechanical means, such for example, as knobs, dials, push buttons or the like, may be employed for the control of, contacts. for accomplishing similarpurposes as those illustrated.

A miniature track diagram, corresponding with the actual track lay-out in the territory under the supervision of the operator, is preferably made a part of the control machine, and positioned directly over the control levers. As representative of such a track diagram, there is indicated in Fig. 1A, a single miniature track switch ts which is intended to represent the actual track switch TS in the field. It is desirable that the control levers associated with each of the switches may be so positioned with respect to the miniature switches on the track diagram, as. to make it easily understood to which switch they belong.

Small indicator lamps of the telephone switch board type, suitably disposed on this track diagram, are lighted to indicate the presence of a train on a corresponding portion of the track. As illustrative of such indication means, the indicator lamp I is. shown controlled in accordance with the occupancy of a detector track section located adjacent the track switch TS shown in Fig. 2B. This indicator I is controlled by an indicating relay ml which is in turn controlled through the medium of the communication system, as hereinafter described.

The positions of the switches in the field, whether the signals associated with such switches indicate clear or stop, and various other annunciator indications (not illustrated), are also preferably provided for the purpose of informing the operator as to the conditions existing in the territory under his control. Such additional indications may be controlled by indicating relays 1B and IE and such other similar indicating relays as may be necessary to be provided for the number and nature of the indications desired.

As heretofore pointed out, the communication system of the present invention is of the duplex coded type where a given number of controls and/or indications are transmitted during each operating cycle. Due to the uneven distribution of switches, signals and the like, in the supervised territory, one field station may have a greater number of controls and/or indications than can be conveniently transmitted during one cycle. The controls and indications at such a field station are divided into groups, each such group including the number of controls or indications which the system can transmit during any one cycle? Thus, any particular field station may include a single group of controls and/ or a single ,groupof indications, or a plurality of such groups, any one of which may be transmitted during a single operating cycle.

Those control levers, which determine the controls of a particular group, together with a storing relay SR, a code determining relay CD and a code determining repeater relay CDR, may be said to comprise the code and control determining means for that group. In other words, there is a bank of relays SR, relays CD and relays CDR; shown as relays SR SR SR CD CD CD and CDR CDRF, CDR with the relays having corresponding exponents comprising the relays for each group of controls irrespective of whether such group is one of a plurality of similar groups, or the only group associated with a particular field station.

Each storing relay SR has a stick circuit normally energized through contacts on the control levers of the corresponding group. The movement of any control lever of a particular group momentarily opens the stick circuit of its corresponding storing relay, thereby causing it to be deenergized, in which condition it remains until the code call for the corresponding group has been transmitted.

The code selecting or code determining relays CD are arranged in a bank with interlocked circuits connecting them to their respective storing relay SR, so that only one of these code determining relays CD may be energized at a time, irrespective of the number of storing relays which may be deenergized as the result of the operationof several control levers of difierent groups. These code determining relays CD with their corresponding repeating relays CDR, when energized one .at a time, connect a plurality of control buses MM, 402, 403, 404, 495, 406, 37, 4138, 409, 4H), 4H and M2 respectively to the code jumpers and control lever contacts of the corresponding groups, to thereby condition the system for'the transmission of code calls and controls, in a manner more fully explained hereinsponding field station in order to transmit the cut-out control to that station. Although the embodiment of the-present invention illustrates the manner in which a particular cut-out control lever is associated with a particular group of a field station in order to obtain the necessary initiation of the system and selection of that station, such cut-out control lever could be provided with its own distinctive group code call. In Fig. 1A, the lever COL is shown as having a contact IS in the normally closed stick circuit of the storing relay SR thereby associating that cut-out control lever with the first group for the station shown in Figs. 2A and 2B insofar as the initiation of the system and the first transmission of the cut-out control is concerned; while the contact corresponding to contact 431 of the code deter mining relay CDR, for this and each other group of that station connects the control bus 4% to the contact [5, so theproper cut-out control is maintained for each selection of that station.

ill

' corresponding group of field indications.

The control ofiice equipment alsoincludes a bank of station registering or decoding relays (see Fig. 1B), which are responsive to the code calls, communicated to the control oifice over the message circuit, of stations having new indications to transmit, such stations being registered or identified one at a time on this bank of stationregistering relays. In the particular arrangement shown, this station registering bank of relays comprises a bank of pilot relays PT PT PT 'PT and PT and a bank of station relays C C C etc., one for each station, the arrangement .of relays shown being applicable for thirtyone stations, but being capable of expansion to provide for any desired number of stations. The particular arrangement shown provides for thirty-two code calls, but the thirty-second is not assigned to any station for reasons pointed out in the pending application of N. D. Preston et al, Ser. 100,455,304, filed May 24, 1930, now U. S. Letters Patent 2,129,183 granted Sept. 6, 1938.

Although only the station relays C C C etc., to C have been shown having circuits selected through contacts on the pilotrelays PT, it is to be understood that the succeeding relays C, C etc., to C are similarly connected,

such connections being merely indicated for the' sake of simplicity. Also, each of the relays C is provided with a repeater relay CR, shown as relays CR CR etc..' to CR A station stick relay STS is provided to maintain energized the particular selected station relay C for each cycle of operation in which the corresponding station is registered in the control office.

A bank of group selecting pilot relays GS is employed to register the code call of the particular group transmitting from the particular station which is registered for that cycle of operation by the station registering relays C. The embodiment of the present invention utilizes three steps for group registration, upon which the group selecting relays GS .GS and GS are respectively controlled. This arrangement is applicable for a maximum'number of eight groups of'indications for each station, but the same principles of arrangement may be extended for as many steps as necessary toprovide the desired number of E 'O D 1 Associated with each station registering relay C is a bank of indication group relays IG, one for each group of the corresponding station, shown as the relays 1G IG etc., to IG for the stations relay C These relays IG are connected to their respective indication group selecting buses 50!. 502. 503, 504, 505, 506, 501 and 508 through front contacts of their corresponding station repeating relays CR when the corresponding field station has been registered. Thus, one indication group relay IG for the station registered is energized in accordance with the group code call registered by the relay GS. This selected indication group relay IG is maintained energized for that cycle by an indication group stick relay IGS.

Each indication group relay IG has associated therewith'a bank of indication storing relays IR of the polar magnetic stick type. Each such bank of relays includes a number of relays equal to the number of indications to be transmitted by the The indication storing relavs IR of each suchbank are connected to the indication buses 609, Bill and 6! I, one bank for each cycle, through front contacts of the corresponding indication group relays IG and front contacts of the corresponding station relay C. Illustrative, of such a bank, indication relays 1R IE and IR are shown associated with the relay 1G which relays are respectively controlled'in accordance with track circuit conditions, signals clear or stop, and switch position-of the corresponding trafiic controlling devices shown in Fig. 2B.

These relays PT, GS and'IR are energized or left deenergized'on each step during a cycle of operation in which they are to be controlled, in accordance with the particular polarity applied to each over their respective indication buses Sill, 602, 603, 604, 605, 606, 601, 608, 609, M0 and (ii I.

The control oflice equipment also includes a suitable number of counting or stepping relays, arranged in a bank and energized sequentially one at a time bythe impulses applied to the steppi-ngcircuit. These stepping relays count ofi the' steps during each operating cycle of the system. Although relays have been shown employed 'for this purpose, any other suitable step-by-step mechanism could be used. 'In the particular arrange-ment shown, providing for five station selecting steps, one transfer step, three group selecting steps and three control and indication steps, there aretwelve relays a, b, c, d, etc., including a last step relay LS. It is to be understood that this is only one arrangement, and that the number o-f'stepping relays would be chosen in practice to fit the number of steps required for selection of the stations, and the number of control and indication steps required for the vari-' ous individual station, as well as the number of steps required for selection of the groups of controls and indications for each station.

An extra step relay ES is associated withthe last step relay LS in a manner to cause the relay LS to-be deenergized on the last step prior to the advent of the system into the period of blank.

The control oflice equipment also includes suitable means for applying impulses of a selected positive-or negative polarity at the proper time spaced intervals, to the stepping circuit. Although some other suit-able means might be employed for this purpose, an impulsing relay 'IM is provided to operate in conjunction with the stepping relays inthe control office, the line relay L and. the half step relay HS in a manner to provide impulses time spaced in accordance with the actual response of the system.

The polarity of eachimpulse applied to the stepping circuit, is determinedby a polarity se-.

lecting relay PS,-which is in turn controlled by a code sending relay CS. This code sending relay CS is energized or deenergized on the successive steps by the code jumpers'associated with the particular code selecting relay CD (with its repeater 'CDR) then energized, and by the positions of the associated control levers SML, SGL and COL, in a manner more fully explained hereinafter.

The control oflice equipment further includes relays ST and CC for stopping and starting the system, a quick acting line repeater relay LR", a slow acting line repeater relay SL a half step relay HS", and various bus wires and connections discussed more fully in connection with the operation of the system.

Included within the control ofiice equipment are three indicator lamps l1, l8 and I9, which are associated with the relays L CS and M respectively, in a manner that the operator may ascertain whether or not the system is in operation causing steps to be taken, whether the system is responsive to controls, and whether the system is transmitting indications.

Field station equipment.A field station comprises a number of traffic controlling devices together with the equipment necessary to establish communication between that field station and the control office. The number and type of traffic controlling devices at the various field stations of the system may vary, so that any particular station may include a single group of controls and/or a single group of indications, or a plurality of such groups arranged in various combinations.

A field station having a plurality of control groups and a plurality of indication groups has been chosen as representative of every other combination, and is illustrated in Figs. 2A and 2B of the accompanying drawings. The equipment, for such a field station, necessary to establish communication between that station and the control ofiice comprises, station selecting apparatus, control group selecting apparatus, indication group selectingapparatus and the trafilc controlling devices associated with each group.

The station selecting apparatus for each station includes the same arrangement of relays, the several stations differing from each other merely in certain station code jumpers or connections which are set to fit the code call assigned to the particular field station location. This station selecting apparatus is preferably arranged in a unit cabinet, so as to be quickly replaced by another unit in the event that a particular unit fails to properly respond.

This station selecting apparatus (see Fig. 2A) includes for each field station, in addition to the line relay L and message relay M already pointed out, a quick-acting line repeating relay LR, and a slow-acting line repeating relay SL, these relays being energized whenever the line relay L is energized with current of either polarity.

An impulse storing relay IS, of the polar magnetic stick type, is arranged to be energized with positive or negative polarity depending upon the polarity with which the line relay L is energized, to thereby store the impulses placed upon the stepping circuit subsequent to the deenergization thereof.

Each field station selecting apparatus includes a bank of stepping or counting relays, energized sequentially one at a time, upon the successive energizations of the stepping circuit irrespective of the polarity of such energizations, and operated in synchronism with the stepping relays at the control ofiice and at each of the other sta' tions. The arrangement shown provides six such stepping relays l, 2, 3, 4, 5 and 6, the number of these relays depending upon the number of steps required for the particular embodiment of the present invention. The particular embodiment illustrated, employs only six stepping relays at each station, although twelve stepsare necessary for each cycle, by reason of the fact that each such bank of stepping relays iscaused to operate through thesecond time for each. cycle of operation in which the corresponding station equipment is selected. Each bank of stepping relays is caused to be responsive to energizations of the stepping line, irrespective of the polarity, by reason of its control through the neutral line repeating relay LR together with a half step relay HS which is of the two position polar magnetic stick type.

The repeat operation of the stepping relay bank at each station is accomplished by a transfer relay TR and a transfer repeater relay TRR which relays are energized whenever the station is selected to receive controls and/0r transmit indications.

The station selecting apparatus for each station further includes two station selecting relays, one relay S0 for selecting the station for the transmission of outgoing controls from the control office, and the other relay SI for selecting the station when it is registered or identified in the control office for transmitting its indications. These selecting relays SO and SI are either selected or dropped out by the code calls trans mitted over the stepping and message circuits respectively by comparison of these transmitted code calls with the code call arbitrarily assigned to the station.

The pulsing relay P and a pulsing repeater relay PR are suitably governed on each step' in accordance with code jumpers of the correspond h ing selecting steps and in accordance with the indications of the station upon the corresponding indication transmitting steps.

The station selecting apparatus also includes a change storing relay CHS, which is suitably err-'- ergized whenever new indications are present at the corresponding field station ready to be transmitted to the control ofiice, and a station cut-out relay'COR. controlled by the operator for preventing that station from transmitting indications to the control oilice. The control group selecting apparatus is also preferably arranged in a unit cabinet suitably connected with the station selecting unit and the associated trafiic' controlling devices,so as to be readily detached.

The control group selecting apparatus (see Fig. 23) includes a number of group selecting pilot relays G governed on the corresponding group selecting steps in a manner to select the proper control group relay CG after the completion of the transmission of the corresponding group code call. For the field station illustrated, the'co'ntrol group selecting equipment includes group selecting pilot relays G G and G control group relays CG CG C6 0G C6 CG" and CG, which arrangement is merely illustrative of that organization which might be used, and is made to correspond with the arrangement of group registering relays in the control office. The control group relays CG have associated therewith, a control group stick relay CGS which is energized after the completion of each group code call to maintain the selected control group relay CG energized for the remainder of the operating cycle.

Each control group relay CG has associated therewith a number of function relays which are connected through front contacts of that control group relay to the respective control buses, but for the sake of simplicity, the function relays have been'shown only for the first control group of the field station illustrated. Although these relays have been specifically shown as a switch machine function relay SMR, a signal relay SGR and a direction relay DR associated with'the control group relay CG and employed for controlling the track switch TS and its associated signals, it is to be understood that other similar relays in the same or other groups may be employed for the same or other purposes.

The indication group selecting apparatus is also preferably arranged in a unit cabinet suitably connected with the station selecting unit and the associated traffic controlling devices, soas to be readily detached. This indication group selecting equipment includes a change relay CH for each group, shown. as relays CH CH and CH and a group determining relay GD for each group, shown as relays GD GD and GD These relays CH and GD are arranged in a bank with interlocked circuits so organized, that only one of the group determining relays GD may be energized at a time, irrespective of the number of change relays CH which may be deenergized. In other words, each change relay CH is associated with the traffic controlling devices of its: corresponding group in a manner that when a new indication is present in. such group, this change relay CH is deenergized, which in turn energizes th corresponding group determining relay GD if no other group determining relay GD is energized, and the system is in. the period of blank.

Illustrative of the indications which may be arranged to comprise a single group, the devices,

associated with the track switch TS which are indicated in the control ofiice, have been shown as including, a track relay T associated with a detector track section TK adjacent the track switchTS, a signal relay SIG associated with the signals adjacent the track switch TS in a manner to be energized whenever all of the associated signals are at stop, and a switch position repeating relay WP of the polar-neutral type, which is en rgized with one polarity or the other in acdance with the extreme locked position of the track switch TS. Associatedwith each track relay T is a corresponding track storing relay STR' em loyed for purposes hereinafter pointed out.

with the first group of this field station, and is provided with a suitable switch machine SM, such as disclosed for example, in. the patent to W. K. Howe, No. 1,466,903, dated September 4,

Such a switch machine SM issupplied with operating current from a local battery and is preferably equipped with a dual control selector permitting hand operation of the switch points disclosed in the application of W; K. Howe,

Ser. No. 354,039, filed April 10, 1929, now 'U. S.

Letters Patent 1,852,573 granted April. 5, 1932. The operation of each such switch machine SM is controlled byits corresponding function control 1 -ay SMR which relay is of the two position .lar magnetic stick type, its energization being under the control of the operator through the mediiun of the communication system of this invention. 1

Each track switch is provided with suitable signals, such for example, as those shown. for the track switch TS. The signals SE and SW are provided to govern east and west main line movernents respectively, and signals SE 'and SW are provided to govern diverging route movements in east and west directions, respectively. These signals are governedby their associated track circuits, the position of the associated switch points, subject to the supervisory control of the operator, through the medium of their corresponding function control relays SGR and DR. The con- The track switch TS is shown as. associated and indications associated therewith may be grouped in any desired manner to most expediently meet the requirements of practice.

Besides the various relays and devices, each station includes a plurality of control buses NH, 182, 103, I04, 105 and. 105, a plurality of indication buses 802, 803, 804, 855 and 806, and

various other wiring connections. Also, the various relays, devices, buses, connections and the like, are either suitably arranged in unit cabinets as described or are housed in. any other suitable manner to best meet practical needs, and

are provided with terminal boards, lightning protection and such other means as may be necessary to meet standard signal engineering requirements.

It is believed that other characteristic features and functions of the system of the present invention will be best made apparent by considering the operation of the system under various conditions.

Operation of the system The general scheme of operation of the system taken as a whole, will be briefly outlined before discussing in detail the various steps which may occur in the operation thereof.

Although the system could be operating continuously, it is preferably arranged (as shown), so as to be normally at rest when no controls are to be transmitted from the control oflice and no indications are ready for transmission from any of the several field stations. The relays and circuits are shown in the drawings: in the positions assumed, when the system is in its normal at-rest condition, the stepping circuit being deenergized, and the message circuit being steadily energized.

When the system is at rest, or in a period of blank, it may be set into operation from the control ofiice for the transmission of new controls to any particular field station, or it may be initiated into operation automatically at any field station having new indications to transmit to the control office. When the system is thus set into operation either manually or automatically, the system operates through what is conveniently termed a cycle of operation and then returns to an at-rest condition.

Each operation cycle of the system is divided into two parts, namely, a selecting part and a transmitting or communicating part. The selecting part of the cycle includes the transmission of the station and group code calls to select a particular group of controls or indications within the particular station with which communication is to be held; while the second part of the operating cycle is the part in which the actual communication is held between the control oifice and the particular group of controls or indications selected during the first part of that cycle.

In describing the operation of the system in detail, it is convenient to discuss the several steps individually under separate heads, first explaining the operation of the system for the transmission of controls from the control office, then the operation of the system for the transmission of indications.

Although the embodiment of the present invention includes the features of two-way transmission, superiority of code, and various other features of a selective coded duplex type system, as disclosed in the above referred to application Ser. No. 455,394, these features will be explained only in sufficient detail to point out their relation and application to the devices, features and functions included within the present invention.

Manual staTting.With the system at rest, the operator may transmit controls to any group of controls for a particular station, which he may desire, by positioning the control levers corresponding to the particular traific controlling devices which he desires to control.

For the present, the provisions made for calling the field stations and groups of controls for such stations, one at a time in a predetermined order, in case one or more control levers of different groups of the same or diiierent stations are actuated simultaneously or in rapid succession, will not be explained; but rather the movement of control levers for only one group of controls for a particular station will be considered.

In the control machine illustrated (see Fig. 1A), the control levers SML, SGL and COL are associated with the first group of controls for the particular field station shown in Figs. 2A and 2B, by reason of their association with the relays SR CD and CDR which, in combination with certain code jumpers, determine the proper code calls for the selection of that station and that particular group of controls 'of the station.

The actuation of any control lever of a particular group of levers from one position to another, momentarily opens the stick circuit of the corresponding storing relay SR. The relays SR. are made suificiently quick acting so that their contacts will assume deenergized positions, if their stick circuits are opened for an interval of time equal. to the shortest time in which the contacts of the associated levers may be moved from one position to another.

For example, the stick circuit for the relay SR is traced from through contact I 6 of lever COL in either extreme position, contact l2 of lever SGL in any one of its three positions, contact [ii of lever SML in either extreme position, front contact 28 of relay SR lower winding of relay SR to If the operator moves any one or all of the levers SML, SGL and COL to new positions, the stick circuit for the relay SR is momentarily opened until the levers have assumed their new positions, which is sufficient to cause the contacts of this storing relay to assume deenergized positions.

With a storing relay, such as SR deenergized, the corresponding code determining relay, such as CD is energized through a circuit which is closed only with the system in an at rest normal condition. This pick-up circuit for the relay CD is traced from through back contact 2! of the last stepping relay LS, back contact 22 of the relay ES, wires 23 and 24, back contact 25 of cycle controlling relay CC, wire 26, back contact 27 of relay ST, wire 28, front contact 29 of storing relay SR wire 30, front contact 3! of storing relay SR wire 32, back contact 33 of storing relay SR upper winding of relay CD to The relay CD is maintained energized through a stick circuit from through back contact 2| of stepping relay LS, back contact 22 of relay ES, wires 23, 34, 35 and 36, front contact 3! of relay CD lower winding of relay CD to The relay CD is maintained energized by this stick circuit until the end of the operating cycle upon which it effectively causes the code calls and controls associated therewith to be transmitted.

When the relay CD is energized, it picks up its repeating relay CDR through front contact 38 included in a circuit obvious from the drawings. Also, with the code .determining relay CD energized, a circuit for energizing the starting relay ST is closed from back contact 39 of relay SL, wire 40, winding of relay ST, wires M, 52 and 43, front contact 44 of relay CD to The starting relay ST closes a pick-up cir-' cuit for the cycle controlling relay CC from through front contact 45 of relay ST, wires 46 and 41, winding of relay CC, to The cycle controlling relay CC is maintained energized throughout the cycle of operation, thus initiated, by a stick circuit closed from. through back contact 2| of stepping relay LS, back contact 22 of relay ES, wires 23 and 24, front contact 25 of cycle controlling relay CC, wires 48 and 41, windings of relay CC, to

The energization of the cycle controlling relay CC immediately starts the system into operation by placing the first impulse upon the stepping circuit. However, before considering the manner in which the stepping circuit receives its successive impulses, it is convenient to consider how the polarity of these impulses is determined or selected in accordance with the code of the station to be selected, the code of the group tobe selected and the controls to be transmitted.

Polarity selection of stepping impulses-The communication system of this invention is provided with suitable means for energizing the stepping circuit with direct current impulses of either positive or negative polarity, the particular polarity applied being predetermined in accordance with the code calls and controls to be transmitted during the respective parts of the operating cycle.

The polarity selecting relay PS pole changes the impulses applied to the stepping circuit as supplied by the impulsing means from battery ET.

This relay PS is of the two position polar magnetic stick type, having'its contacts actuated to right or left hand positions by reason of the polarity of potential applied to its windings with the relay CS deenergized or energized respectively. Negative impulses are applied to the step ping circuit with contacts 49 and 50 of this relay PS in right hand positions; while positive impulses are applied to the stepping circuit with contacts 49 and 50 in left hand positions.

With the relay CS deenergized or energized, (B) or (B+) are respectively placed upon the relay PS during the deenergized condition of the stepping circuit (message or execution period of each step) through a circuit including back or front contact 5| of relay CS respectively, wire 52, back contact 53 of relay LRP, wire 54, winding of relay PS, to (ON) The code sending relay CS is energized or left deenergized upon each step, to select the desired polarity of the impulse for the next step,

in accordance with the energized or deenergized condition of the respective control buses 40 l, 402, 403, 404, 605, 406, 401, 408, 409, AID, 4H and M2. When the system is at rest, for example, the relay CS is connected from through winding of relay CS, wire 55, to the control bus 40I through the back contacts of all of the stepping period of blank in accordance with'the energized or deenergized condition of this code bus. Thus, the polarity of the first stepping impulse may be determined by the energization or deenergization of this control bus 4M prior to the actual response of the system to initiation.

When the first impulse is applied to the stepping circuit, the stepping relay a is picked up, irrespective of the polarity of this first impulse, in a manner later to be explained, and this connects the relay CS through front contact III of stepping relay a to the control bus 402. If this bus is energized, the next or second impulse applied to the stepping circuit will be positive; while, if the control bus 402 is left deenergized, the second stepping impulse will be negative.

When the second impulse is applied to the stepping circuit, the stepping relay b is picked up and the stepping relay it drops, irrespective of the polarity of the second impulse, which connects the relay CS to the control bus 493 through back contact III of relay a and front contact I! of relay b.

In the same manner as explained for the com trol buses 40! and 402, the code sending relay CS is connected to the remaining control buses upon the successive steps, and depending upon whether these buses are energized or deenergized, the code sending relay CS is energized or left deenergized thereby determining whether the stepping impulses shall be positive or negative.

The control buses are selectively energized or deenergized, to provide the desired code calls and controls, In the embodiment of the present in .vention, the control buses 41H, 402, 493, 404 and 405 are controlled in accordance with the code call jumpers of a particular station for each cycle through front contacts of the code determining relay CD corresponding to that station; the control bus 496 is controlled in accordance with the cut-out lever of a particular station for each cycle through front contacts of the corresponding code determining repeater relays CDR of the corresponding station; the control buses 40?, 408 and 409 are controlled in. accordance with. thecode call of the particular group of controls for the station through front contacts of the corresponding code determining repeating relay CDR; and the control buses 4I0, 4H and M2 are controlled in accordance with the control levers of the corresponding group of controls through front contacts of the corresponding code determining repeater relay CDR.

In the arrangement shown, providing for five station selecting steps, one transfer step, three group selecting steps and three control steps, twelve control buses are necessary; but it should be understood that arrangements of code buses, similarly controlled by contacts of similar stepping relays could be provided for various other arrangements of code calls and controls.

As the impulsing means, for applying a series of time spaced impulses of selected polarity to the stepping circuit, includes the operation of the stepping relay bank in the control oifice to thereby regulate the time spacing of the impulses in accordance with the actual response of the system, an understanding of the operation of the stepping relay banks is necessary before considering how the series of impulses is actually applied to the stepping circuit.

Operation of stepping relay banIc.The stepby-step means at the control office and at each field station comprises, a number of neutral relays forming a stepping relay bank, together with a half step polar magnetic stick type relay. The application of a series of impulses to the stepping circuit causes the stepping relays of each bank to sequentially operate in synchronism with the stepping relays of every other such bank, irrespective of the polarity of the impulses.

Assuming for the present that a series of time spaced impulses of selected polarity can be suitably applied to the stepping circuit with the first impulse of relatively long duration to mark the beginning of the series or cycle, in a manner later to be explained, we will consider the operation of the stepping relay bank with more specific reference to the relay bank of Fig. 2A, as the operation of this bank is typical of all others.

With the system normally at rest, or in the period of blank, the half step relay HS is energized with positive potential from (B-) through back contacts 56, 51, 58, 59, 60 and 6| on the stepping relays 6, 5, 4, 3, 2 and 1 respectively,

winding of relay HS, back contact 62 of relay Thus, whenever the system. is atrest, the relay HS is always returned to its nor- LR, t0 (CN).

mal position in readiness for initiation of the system into a cycle of operation.

The line relay L, included in the stepping circuit, is of the three position biased-to-neutral polar type relay, which actuates its contacts: to

one extreme position or the other in accordance with the polarity of the impulse applied to the stepping circuit, but irrespective of the position to which the contacts of the relay L are operated, the relays SL and LR are energized in series, as obvious from the drawings (see Fig. 2A). The application of the first impulse to the stepping circuit results in the energization of the quick acting line repeating relay LR with the slow acting line repeating relay SL responding to this impulse a short time thereafter. This closes a pick-up circuit for the stepping relay I from through polar contact 63 of relay HS in a right hand position, wire 64, front contact 65 of relay LR, Wire 66, back contact 61 of relay SL, wires 68 and 69, lower winding of stepping relay I, back contact 12 of stepping relay 2, to

Upon the energization of the relay SL, this pick-up circuit of the stepping relay I is opened at back contact 61, but its stick circuit is completed from through front contact 13 of relay SL, wires 14, I5 and 16, front contact I1 of stepping relay I, upper winding of stepping relay I, back contact I2 of stepping relay 2, to This arrangement requires that the contact I3 of relay SL preferably be made before back contact 6'! is opened.

The energization of the stepping relay I closes a'pick-up circuit for the stepping relay 2 through front contact 18, but as the same polarity is applied. to both terminals of the lower winding of the stepping relay 2, it remains deenergized.

Upon the deenergization of the stepping circuit, the relay LR is deenergized, closing a circuit from (3+), through front contact 6| of stepping relay I, winding of relay HS, back contact 62 of relay LR, to (CN). This reversal of polarity upon the relay HS, causes it to actuate its contact 63 to the left hand dotted line position, in readiness for applying suitable polarity to the lower Winding of the stepping relay 2 toaccomplish its energization as soon as the relay LR is again energized closing front contact 65.

Upon the application of the next impulse to the stepping circuit, the relay LR is again energized, the slow acting relay SL of course remaining energized between the successive impulses, the pick-up circuit for the stepping relay 2 is closed from through polar contact 63 of relay HS in a left hand position, wire 64, front contact 65 of relay LR, wire 66, front contact 6'! of relay SL, wires 19 and 80, front contact 18 of stepping relay I, lower winding of stepping relay 2, back contact 8! of stepping relay 3, wires 82, 83, I5 and 14, front contact 13 of relay SL, to

Thisenergization of the stepping relay 2, opens the stick circuit of stepping relay I, at back contact i2, and closes its own stick circuit from through front contact 72, upper winding of relay 2, back contact 8| of stepping relay 3, wires 82, 83, i5 and 1 5, front contact 13 of relay SL, to

The energization of the stepping relay 2 also closes the pick-up circuit of the stepping relay 3, but as explained for the stepping relay 2, the same potential is applied to both terminals of the lower winding of stepping relay 3.

Upon the next deenergization of the stepping circuit, the relay LR is deenergized closing the energizing circuit for relay HS from (B), through front contact 6!! of stepping relay 2, back contact 6! of stepping relay I, winding of relay HS, back contact 62 of relay LR, to (CN). This actuates the polar contact 53 of relay HS to a right hand position.

Upon the application of the next impulse to the stepping circuit, the relay LR is energized, the slow-acting relay SL of course remaining energized between successive impulses, and the pickup circuit of the stepping relay 3 is closed from through polar contact 63 of relay HS in a right hand position, wire 6 3, front contact 55 of relay LR, wire 66, front contact 61 of relay SL, wires 79 and 89, back contact 18 of stepping relay l, front contact 84 of stepping relay 2, lower winding of stepping relay 3, back contact 85 of stepping relay 4, to

The energization of the stepping relay 3 opens the stick circuit of the stepping relay 2 at back contact 3! and closes its own stick circuit which may be understood by analogy to the stick circuits of stepping relays i and 2.

Upon the next deenergization of the stepping circuit, the relay LR is deenergized closing the energizing circuit of the relay HS, from (B+), front contact 59 of stepping relay 3, back contacts 68 and ti of stepping relays 2 and i respectively, winding of relay HS, back contact 62 of relay LR, to (CN).

This operation of the stepping relays is con.- tinued from step to step for as many steps may be required, causing the stepping relay banks to operate sequentially and in synchronism at the control ofiice and at each field station irrespective of the polarity of the impulses applied to the stepping circuit.

Impulsing of the stepping circuit-It has been explained, how the polarity of the impulses applied to the stepping circuit is determined or selected in accordance with the code calls and the controls desired to be transmitted by suitable control of a polarity selecting relay PS provided with pole changing contacts. Also, the operation of the stepping relays has been described. Therefore, consideration may now be given to the operation of the impulsing means for applying these impulses to the stepping circuit at the proper time spaced intervals in accordance with the actual response of the system.

The impulsing means is arranged toapply current of the selected polarity to the stepping circuit for a predetermined time interval, conveniently termed an operating or conditioning period, and then deenergized the stepping circuit for another predetermined time interval, conveniently termed the execution or message period. In other words, a step may be said to comprise the energization and deenergization of the stepping circuit. When the system is initiated from an at rest condition, the first impulse is made a long impulse with respect to the succeeding impulses to mark the beginning of the operating cycle; while the end of each operating cycle is made distinctive by the relatively long interval of time between the last impulse of one cycle and the first impulse of the next cycle. This interval of time between cycles of operation is conveniently termed the period of blank, or at rest period.

The energization of the cycle controlling relay CC (see Fig. 1D) in a manner above explained, causes the first impulse of that cycle to be placed upon the stepping circuit, with the polarity of this impulse determined by the position of the contacts of relay PS. The stepping circuit is traced, depending upon the position of relay PS, either from the negative terminal of the battery ET in the control oifice (see Fig. 1D), through front contact 85 of relay CC, wire 81, back contact 88 of impulsing relay IM, wire 39, polar contact 56 of relay PS in a right position, wires 91] and 9!, winding of line relay L through the stepping and control line to the first field station, through the line relay L at that station (see ig. 2A), and similarly through the stepping line and the relays at the remaining stations to the common return line at the last station, and thence back to the control ofiice, wires 92 and 93, polar contact d9 of relay PS in a right hand position, wire 9%, back contact 95 of impulsing relay IM, wire 96, front contact 9'! of relay CC, to the positive terminal of the battery BT or from the positive terminal of the battery BT through front contact 97 of relay CC, wire 96, back contact 95 of impulsing relay IM, wire 94, polar contact 49 of relay PS in a left hand position, Wires 98 and $5, winding of line relay L thence through the stepping and control circuit including the line relay L at each station to the common return line at the last station, and thence back to the control office, wire 92, polar contact 56- of relay PS in a left hand position, wire 89, back contact 83 of relay IM, wire 81, front contact 85 of relay CC, to the negative terminal of battery ET.

This application of potential to the stepping circuit causes the polar contacts of the line relays L to be energized either to right or left hand positions, depending upon the polarity, which in turn causes the energization of the line repeating reiays SL and LR irrespective of the polarity applied to the stepping circuit, as heretofore ex plained. The stepping relays at the control oflice and at each of the field stations are thus caused to take the first step, as previously explained.

The energization of the slow-acting line repeating relay SL (see Fig. 1D), causes the deenergization of the starting relay ST at back contact 39 which then drops away according to its slow-acting characteristics. With the stepping relay 0. energized and the starting relay ST response of the system.

deenergized, the impul'sing relay IM receives energy through a circuit from through back Contact 45 of relay ST, wire ml, polar contact )2 of relay HS in a right hand position, wire I63, upper winding of impulsing relay IM, wire Hi4, front contact !05 of stepping relay a, to

This energization of the impulsing relay IM opens the stepping circuit at back contact 88 and 95, which of course causes the deenergization of the quick acting line repeating relays LR.

The deenergization of the relay LR in the control ofiice causes the half step relay HS to assume a new position, for reasons previously pointed out, thereby opening the energizing circuit of the impulsing relay IM at polar contact I02 of relay ES. The deenergization of the impulsing relay IM causes the stepping circuit to be again energized with a polarity in accordance with the position of the relay PS which relay is also controlled while the relay LR is deenergized, as previously explained.

The energization of the stepping circuit causes the next step to be taken at the control office and at each of the field stations. As soon as the second stepping relay b has responded in the control ofilce, an energizing circuit for the impulsing relay TM is completed from through back contact45 of relay ST, wire llil, polar contact I02 of relay HS in a left hand position, wire I06, lower winding of impulsing relay IM, wire I 01, front contact I08 of stepping relay 1), back contact Hit of stepping relay a, to This energization of the impulsing relay IM again opens or deenergizes the stepping circuit thereby dropping relay LR etc., and thus actuating the half step relay HS".

This alternate energization and deenergization of the stepping circuit continues until the end of the operating cycle, at which time it is deenergized for a relatively long period of time to mark the end of the cycle. This period'of blank may be more conveniently explained in describing the end of the operating cycle which will be taken up under a separate heading.

In summary, the conditioning period of the first step (interval of time during which the stepping circuit is energized) includes the pickup times of the relays L SL and 1M, together with the drop-away time of the relay ST, as compared with the conditioning period of every other step which includes the pick-up times of relays L", LR, a stepping relay and the relay IM. Thus, the conditioning period of the first step (energization of the stepping circuit) is longer than theremaining conditioning periods by the difference in the pick-up time of relays SL and LR together with the difference between the drop-away time of the relay ST and the pick-up time of any stepping relay.

The execution period of each step (interval of time between successive impulses of a cycle during which the stepping circuit is deenergized) includes the drop-away time of relays L LR, IM and the operating time of relay HS Thus, a series of time-spaced impulses, with polarities selected in accordance with the code calls and controls to be transmitted, is placed upon the stepping circuit causing a series of steps tocomprise a cycle of operation. As the impulsing means includes the step-by-step means, the impulses of each-series or cycle are therefore time spaced in accordance with the actual Sequence of station selection-It is apparent that only one combination of positive or negamore than one code call tobe applied to thesame circuit at the same time, the resultant code call would be false or mutilated in, such a man-.

ner as to select either the wrong station or the wrong group of a station.

The operator might be relied upon to actuate the control levers for the several stations and groups of such stations for controlling one group of a particular station at a time, so as to avoid such mutilation or interference of the code calls; but the system of this invention provides that the code calls shall be automatically sent out, one at a time on each operating cycle, regardless of the sequence or rapidity with which the operator may manipulate the control levers on the control machine. With such an arrangement, the operator can devote his attention to the making of plans for the handling of traffic and keeping such records and account of the trains and other details as may be required for the proper operation of a railroad.

This feature of automatic determination of which code call shall be transmitted during 'a' particular operating cycle, is provided by the storing relays; SR and the code determining relays CD through means of interlocked circuits allowing the energization of but one code determining relay CD regardless of the number of storing relays SR which may be deenergized as the result of the manipulation of several control levers to new positions simultaneously or in rapid succession.

For each group of levers, corresponding to a particular group of controls for a particular field station, there is a storing relay SR, a code determining relay CD, and a code determining repeating relay CDR. The actuation of any lever, in such a group of levers, to a new position momentarily opens the stick circuit of the corresponding storing relay which remains deenergized, until the code calls and controls associated therewith havebeen insured of transmis- SlO-Il.

While the system is at rest, or in the period of blank, the deenergization of any storing relay SR will pickup its corresponding code determining relay CD providing there are no other storing relays deenergized or code determining relays en-' ergized. The pick-up circuit for any relay CD in the bank includesa back contact of its corresponding storing relay SR, and front contacts of each storing relay to the right of it, which prevents its energization if any of the storing relays to the right are deenergized. With a particular relay CD energized, the relays CD to the right thereof are prevented from picking up'by reason of their pick-up circuits including a back contact on each of the relays CD to the left. For example, assuming the deenergization. of the storing relay SR subsequent to the deenergizacode determining relay CD inthe bank includes a back contact of its corresponding storing relay, a front contact of each storing relay SR to the right of it, and a back contact of each code determining relay CD to the left of it, besides the back contacts upon the relays LS, ES, CC

and ST which serve to prevent the energization of a code determining relay CD except during the period of blank.

If several of the storing relays SR are deenergi'zed' in rapid succession by operation of their corresponding levers, the relay SR first to be deenergized will pick up its corresponding relay CD, but thereafter the other relays CD will pick up in a sequence from right to left, as will be evident from the study of the circuits illustrated in Fig. 1A. As heretofore pointed out, each control and code determining means may be associated either with a station as a whole or with a group of controls for a station. This means that, if the operator actuates several levers simultaneously or in rapid succession, regardless of whether such levers are in the same group of levers for a particular group of controls of a particular station or in some other group for the same or a difierent station, the stations and groups within such stations are called in an order or sequence determined by the location of the corresponding code determining relay CD in this bank of interlocked relays.

Although these relays CD, as above explained, will be energized in a sequence from right to left, the several groups of levers may be connected to the relays SE in any desired order, thereby predetermining the order in which the stations and groups of such stations will be se lected. This feature makes it unnecessary for the operator to take count of the operating cycles of the system in order to properly move his levers, but rather he may move the levers in any manner he desires and the system automatically calls the stations and groups Within the stations, one at a time in a predetermined sequence, in accordance with the importance of the station as originally determined in making the connections in the interlocked bank of relays.

With only one code determining relay CD and repeater relay CDR energized at a time, the control buses Mil, 402 and 4&3 and so forth, will be respectively connected to one group of station code jumpers, one group of group code jumpers, and one group of control levers for any one cycle of operation. As the code sending relay CS is connected to the control buses 40!, 402, 403 and so forth, upon successive steps, each impulse of the series of impulses placed upon the stepping circuit will be of positive or negative polarity in accordance with those station code jumpers, group code jumpers and control levers associated with the particular code determining relay CD then energized for that cycle of operation.

For example, the energization of the code determining relay CD causes the transmission of a series of impulses comprising a cycle of operation as folloWs:(-), for the station code call; for the transfer step; for the group code call; and for the controls. This of course assumes that the levers and code jumpers are in the positions as shown, it being understood that one or more control levers must be moved to new positions to initiate the system and cause the transmission of controls, thereby changing the polarity of the corresponding control impulses. The movement of the switch machine lever SlVlZL from a normal position to a reverse position, for example, energizes the relay CD initiates the system, and causes the transmission of station and group code call impulses 7 together with a transfer step impulse as above pointed out, and a series of control impulses now having the polarities Station seZectzon.-When controls are to be transmitted from the control ofiice, the field stations are selected one at a time in accordance with the combination of positive and negative impulses applied to the stepping circuit for a certain number of steps; while the groups of controls within such stations are selected one at a time in accordance with the combination of positive and negative impulses applied to the stepping circuit for a certain number of succeeding steps.

As above pointed out, each impulse applied to the stepping circuit causes the step-by-step means at the control ofiice and at each of the field stations to take one step, irrespective of the polarity of these impulses. Since the polarity of the impulse causing each step may be made either positive or negative, a number of different combinations of impulses may be obtained depending upon the number of steps.

In other words, during the first or selecting part of the operating cycle, combinations of positive and negative impulses are transmitted, which combinations may be conveniently termed code calls. Each one of these code calls, transmitted during the selecting part of the operating cycle, may be termed a total code call and must be transmitted to select a particular group of controls of a particular field station, before such controls may be transmitted from the control ofiice. For convenience in discussing the selecting part of the operating cycle, those impulses of the total code call, transmitted to select the particular station, may be termed the station code call; while the remaining number of impulses of the total code call, transmitted to select the particular group within the station, may be termed the group code call.

In this type of code, a choice of positive and negative impulses on each of two steps gives four different combinations of impulses or code calls, three steps gives eight different code calls, four steps gives sixteen different code calls, five steps gives thirty-two different code calls, and so on, each additional step doubling the number of possible distinctive code calls. Such an arrangement of positive and negative impulses to obtain eight combinations or code calls for three steps is shown below in a Typical code table, which table may be extended for any number of steps.

Typical code table With a code call assigned to each field station, selection is made between half of the total number of stations on the first station selecting step, depending upon Whether it is a positive or a negative impulse. Similarly, on the second station selecting step, a selection is made between half of the stations remaining after the first selection, depending upon the polarity of the second impulse, leaving only one quarter of the total number of stations. This elimination of stations is carried on for as many steps as may

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