US2176600A - Remote control system - Google Patents

Description

N. F. AGNEW REMOTE CONTROL SYSTEM Qct. 17, 1939.

4 Sheets-Sheet 1 Filed Oct. 8, 1952 OFFL'CQ PanelfVoJ.

INVENTOR [Vormazz E'Aqzzaw BY 1:11:15 H1; ATTORNEY Qct. 17, 1939. AGNEW 2,176,600

REMOTE CONTROL; SYSTEM Filed Oct. 8, 1932 4 Sheets-Sheet? Ib I. I I

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Oct. 17, 1939. N. F. AGNEW REMOTE CONTROL SYSTEM Filed Oct. 8, 1932 4 Sheets-Sheet 3 5 m d K. As w P. 4 d 5 P 1 6c 2d R. w. Q m

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N. F. AGNE W REMOTE CONTROL SYSTEM Filed Oct. 8, 1932 4 Sheets-Sheet 4 LJZB E LHA 12 LAHR LBHR US l

.J YER INVENTOR Norman EAgzzow.

3% dam H15 A TTORNEY Patented Oct. 17, 1939 UNITED STATES PATENT OFFICE REMOTE CONTROL SYSTEM Application October 8, 1932, Serial No. 636,882

60 Claims.

My invention relates to remote control systems for the control from a central point of selected devices at remote points, and for also indicating at said central point the condition of said devices and other devices at remote points. Apparatus embodying my invention is particularly adapted for, though in no way limited to centralized trafiic control systems for railroads, in which trail-lo governing devices along the trackway are controlled from a dispatchers ofiice, and the conditions of such devices and associated apparatus are indicated in said ofiice. In its specific embodiment, my present. invention relates to a centralized trafiic control system of the type which employs apparatus which is normally inactive but which when set intooperation establishes communication between a control office and each of a plurality of field stations in turn during a single cycle of operation.

My present invention is an improvement upon the system disclosed in my copending application Serial No. 451,668, filed May 12, 1930, for Remote controlling'apparatus. One object of my present invention is to provide an arrangement whereby the sources of energy for the line circuits connecting the oflice and the stations are wholly located at the ofiice so that the only sources of energy required at the field stations are those employed for the operation'of local apparatus. Another object of my present invention resides in the provision of a normally closed line circuit in a system of this character for connecting the ofiice and each station. Other objects and features of my invention will become apparent as the description proceeds.

I will describe one form of apparatus embodying my invention, and will then point out the novel features thereof in claims.

In the accompanying drawings, Figs. 1 and 2 when arranged vertically with Fig. 2 below Fig. 1, form a diagrammatic view illustrating one form of ofiice equipment employed in a centralized traflic control system embodying my invention. Figs. 3 and 4, when arranged vertically with Fig. 4 below Fig. 3, illustrate the corresponding apparatus for one field station. Figs. 1 to 4, inclusive, when arranged with Figs. 3 and 4, respectively, at the right of Figs. 1 and 2, form a complete diagrammatic view of the system as arranged for the control of one field station. When the apparatus is employed to control a plurality of stations, the apparatus at each station is exactly similar to that illustrated in Figs. 3 and 4, and the diagrammatic View of the system may be extended to include additional stations by arranging additional copies of Figs. 3 and 4 at the right of Figs. 3 and 4 illustrating one station. For each field'station, the oflice equipment includes a panel containing individual control and indication devices, as shown included within the 5 dotted line rectangle entitled Panel No. 1 in Figs. 1 and 2. Each additional station requires a similar panel, and the complete ofiice equipment for a plurality of stations may be included in the diagrammatic view by inserting additional copies of the drawings of the panel in Fig. 1 at the right of Panel No. 1. Fig. 5 illustrates a novel form of relay employed in the apparatus shown in Fig. 2.

Similar reference characters refer to similar parts in each of the views.

The apparatus at the station which is con trolled from the ofiice may be of any suitable form, but for purposes of illustration, the centralized traflic" control system of my invention has. been arranged in such a manner that it includes tralfic controlling .and indicating apparatus at a contro'l'office and apparatus which may be installed at each of a plurality of stations spaced at intervals along the line of a railroad, '25 and the system is'arranged to provide continuous indications at' the office of the condition of each of the switches and signals in the controlled territory, for indicating the passage of each train through. the territory, and to provide facilities whereby an operator at the dispatchers office may operate track switches and arrange train meets without stopping trains, without the use of train orders, and without the necessity of communicating with trains except by controlling the railway signals which govern train movements over the switches.

For purposes of illustration, I have, in Fig. 4, shown a typical group of apparatus adapted to control track switch W and a group of associated signals governing 'trafiic in both directions over the switch, and have also shown apparatus adapted to cause the transmission of indications of various station devices to the dispatchers office. The switch W is located in a track section IT, customarily referred to as the detector section, which has a track circuit with the usual 'tr'ack battery BI and a track relay TR. It is to 'be understood that the normal direction of traffic over this section is from left to right and that 50 this traific is governed by the three-arm signal at the left-hand entrance to the section. At the right of section IT, I have shown an adjacent section 3T having a track circuit with the usual track battery B3 and a track relay LAR, and at 55 the left, a section 2T, customarily referred to as the approach section, which has a track battery B2 and track relay RAR. The movement of traffic through section II. from right to left against the normal direction of traffic, that is, from section 3T or 4T, is governed by the dwarf signals LI-IA and LHB located at the right-hand entrances of section IT.

In order to simplify the disclosure I have in many instances illustrated relay contacts on the drawings remote from the relay windings which control them. In every such case, I have applied to the contact, the reference character used to designate the relay which operates it, and in addition, I have applied a separate reference character to each contact of the relay. I have also in each case employed lower case letters for the purpose of designating relay contacts and capital letters or figures to designate relays, thus, for example, relay TR at the top of Fig. fl has three contacts a, b and 0, shown directly beneath its coil, and also has a contact d in the circuit of relay WR at the bottom. of Fig. 4, and a contact 6 shown at the lower right-hand corner of Fig. 3. The designation TR over this last-named contact distinguishes it from another contacts bearing the designation e, such for example as contacts e of relays NKR, LAR, and RAR which are shown just above it. The relays which are shown in Fig. 4 are preferably of the well known types customarily employed in railway signaling circuits and these relays are in part controlled automatically as a result of movement of traffic] through the territory, and are in part controlled manually through the medium of my remote control apparatus by means of the six control relays of the group illustrated at the bottom of Fig. 3 of which certain contacts are included in the circuits of Fig. 4.

For each of the signals governing traffic over section IT, I provide a signal relay as shown in the upper portion of Fig. 4. Each signal relay has the designation HR, with a prefix identifying the signal which it controls, for example, relay RAHR controls the right-hand signal RI-IA, while relays RBHR and RCHR control signals BBB and RI-IC, respectively. Similarly, signal relays LAI-IR and LBHR control signals LHA and LHB, respectively. I provide a signal indication relay RGP or LGP for the signals for each direction, and each is arranged to be energized when the associated signals indicate stop. I also provide approach locking relays for each direction, designated RMR and IWLR, respectively, which are employed in such a manner as to prevent the operation of switch W under certain conditions. Associated with these approach locking relays is a time element relay TER whose function will be made manifest during the detailed discussion of the circuits. For the control of switch W, I provide a polarized switch control relay WR.

As illustrated in Fig. 4, all signals are at stop, and it is to be assumed that the normal switch stick relay NWSR has been energized by the operator so that relay RWSR is deenergized, and that the switch has been moved to the normal position by switch motor M and has opened the operating circuit for motor M. Switch W is controlled by a dual selector switch machine having a selector lever DS which in one position closes its contacts a and b and also couples the shaft of the motor armature l6, by means not shown, to the mechanism for moving the switch, so that the switch is thereby adapted for power operation. The selector lever in another position opens the contacts a and b and connects a hand throw lever to the switch mechanism in lieu of the motor so that the switch may then be operated manually. The switch operating mechanism. is provided with a circuit controller WP controlling two switch indication relays NKR and RKR, respectively. When the switch is locked normal, contacts n and n of WP, which are in the circuit of relay NKR, hereinafter traced in detail, are closed. When, however, the switch becomes unlocked at the beginning of its movement from normal to reverse, these contacts are opened and when the switch completes its movement and becomes locked in the reverse direction, a similar pair of contacts 1 and r of controller WP, which function in a similar manner with respect to the reverse position of the switch, become closed to energize the indication relay RKR.

It is to be understood that a local source or sources of direct current are provided at each location but for simplicity I have illustrated the circuits diagrammatically and in lieu of showing the local source and the wires leading thereto in detail, I have shown only the terminals of the sources which I have designated in each case by the reference characters B and C.

I will now trace in detail the circuits of Fig. 4.

Since all signals are deenergized, a circuit is closed for relay RGP from terminal B, back con tacts c of each of the relays RAHR, RBI-IR and RCHR in series and the winding of relay RGP to terminal C, so that RGP is energized. Relay LGP is energized over a similar circuit including back contacts 0 of relays LAHR and LBHR. Since the approach sections 2T and 3T are un occupied, track relays RAR and LAR are energized and a. circuit is closed for relay RM'R from terminal B, contact a of relay RGP, contact 0 of relay RAR, the winding of relay RMR to terminal C. Since the switch is normal, relay NKR is energized over a circuit from terminal B, contact b of dual selector DS, wire ll, contact 71 of controller WP, left-hand contact I) of relay WR, winding of relay NKR, back contact at of relay RKR, contact n of controller WP to terminal C. Relay LMR is energized over a circuit from terminal B, contact a of relay LGP, contact c of relay LAR, contact 2 of relay NKR, and the winding of relay LMR to terminal C.

Track relay l TR is provided with a slow pickup slow release repeater relay TZ having a circuit from terminal B, contact I) of dual selector lever DS, wire H, contact a of relay TR and the winding of relay TZ to terminal C, so that TZ is energized when section IT is unoccupied provided the switch selector lever is not in the hand-throw position.

Assuming that the normal switch stick relay NWSR is energized, a circuit is closed for switch control relay WR from terminal B, front contacts d of relays NWSR, RMIR, LMR and TR, winding of relay WR, front contact (1 of relay TZ, back contact (1 of relay RWSR, resistor RID, to terminal C.

If now the operator deenergizes NWSR and energizes the reverse switch stick relay RYVSR, a circuit is closed similar to that just described except that terminal B is connected to the front contact d of RWSR and the current flow is in the reverse direction through the winding of relay WR to the back contact (I of NWSR, resistor R10 to terminal C so that relay WR is energized in the reverse direction. When this occurs, its polar contacts b, c, d and 6 become closed to the right and the motor circuit is closed from terminal B,

contacts a and d of relay WR, armature l6, contact e of relay WR, contact r" of controller WP, field winding ll of motor M, contact a of selector lever DS to terminal C so that the motor is energized to reverse the switch, and at the completion of its movement the motor circuit is opened at contact 1*" of controller WP. If now RWSR is released and NWSR is energized, relay WR becomes energized in the normal direction so that its polar contacts becomes closed to the left, as shown, and a motor circuit is closed similar to that just traced except that the current flow through armature IE will be in the opposite direction and the circuit will include contact n" instead of r, and will be opened when the switch completes its movement to normal.

As soon as the switch becomes unlocked in its movement from the normal to the reverse position, relay NKR is deenergized, and when it has completed its movement to reverse, a circuit is closed from terminal B, contact I) of dual selector DS, wire I l, left-hand contact 7 of controller WP, right-hand contact 0 of relay WR, winding of relay RKR, back contact d of relay NKR, lefthand contact r of WP to terminal C, so that RKR is energized. While the switch is in transit, controller WP operates to connect contacts n to n and contactsr to r so that the wires leading to each indication relay are short-circuited. Contacts b and c of relay WE are also provided with jumper connections so that RKR is shortcircuited when WR is normal unless NKR picks up, and similarly NKR, is short-circuited when WR is reversed unless RKR picks up, as is obvious from the drawing, thus providing protection against inadvertent operation of the switch indication relays when the switch control relay and switch controller do not agree in position.

If with the apparatus in the position shown in the drawings, we assume that the operator picks up the right-hand signal stick relay RHSR, the signal relay RAl-IR will become energized to clear the associated signal RHA. Each of the signal relays, such as RAHR, controls a signal lighting circuit from the terminal B, back contact a of the si .ial relay, through stop signal lamp R to terminal C, and with a circuit from terminal B and front contact a of the signal relay through a proceed lamp G to terminal 0, so that lamp G will be lighted to indicate proceed or lamp R to indicatestopaccordingaswhetherthesignalrelay is energized or deenergized. The circuit for signal relay RAHR is from terminal B, back contact I) of relay TER, front contact 0 of relay TR, front contact 'b of relay LGP, front contacts a of relays NKR and LAR, winding of relay RAE-IR, back contact 0 of relay USE, front contact d of RI-ISR back contact at of LHSR, front contact 6 of NWSR, back contact e of RWSR, resistor R9 to terminal C. If relay RWSR is energized in place of NNSR, and the switch is reversed, signal relay RBHR will be energized in place of RAHR, the circuit for RBHR being from terminal B, back contact I) of relay TER, front contact 0 of relay TR, front contact I) of relay LGP, front contact a of relay RKR, winding of relay RBHR, front contact c of relay Rl-ISR, back contact 0 of relay LHSR, front contact 0 of relay RWS-R, back contact e of relay N'VSR; resistorR9 to terminal C. It follows that signal RI-IA may be cleared when the switch is normal and the sections IT and ET are unoccupied and that signal RHB may be cleared when the switch is reversed and the section IT is unoccupied. When the switch is normal, the operator may clear signal RHC in place of RHA by picking up stick relay USR in addition to picking up relay RHSR. When relay USR and relay RHSR are both energized, relay RCHR may be energized over a circuit similar to that already described for relay RAHR except that it includes back contact 1:: of RAHR, front contact 0 instead of the back contact of USB and does not include a contact of relay LAR. It follows that the operator may clear signal RHC when the switch is normal and IT unoccupied even though 3T is occupied.

Referring now to the signal relays for the opposite direction, it is obvious from the drawing that the circuits for the signal relays LAHR and LBHR are similar to those already described and differ only in that the control is arranged for the opposite direction of trafiic. It is also obvious that when any one of the right-hand signals is cleared, relay RGP becomes deenergized, and when one of the left-hand signals is cleared, relay LGP is deenergized, and that the circuits are so arranged that it is not possible to clear a signal unless the opposing signals indicate stop and the switch is locked in the indicating position in agreement with the route set up by the operator as indicated by the positions of the switch and signal stick relays.

It is to be noted that in the signal relay circuits just described those relay contacts which are controlled automatically by traffic conditions at the station by relays of the railway signaling type are segregated on one side of the windings of the signal relays, while the contacts that are employed to effect manual control are segregated on the other side of these windings. If the manually controlled relays were omitted, it is obvious that the signal relay windings could be connected together and to terminal C on the lastmentioned side without detracting in any way from the safety of operation of the signals, and hence it follows that with the circuits as arranged the safety of the system is not jeopardized in any way by crosses or'other failures of the control relay contacts, so that these relays are preferably of a small quick-acting type having clearance between contacts smaller than provided in the usual railway signaling relays. This arrangement not only effects economy in apparatus, but due to the higher speed of operation of the smaller relays permits a marked increase in the speed of operation of the control system.

When the operator has cleared signal RHA, relay RGP is released as already explained, and this in turn releases relay RMR which opens its contact d in the circuit of relay WR and prevents manual operation of the switch while the signal is clear. A similar condition em'sts when any one of the other signals is clear, as is obvious from the drawing. If when signal RHA is clear, a train enters section 2T, relay EAR. will be deenergized and if the operator now desires to change the route, and puts signal RHA to stop, relay RMR will not pick up to release the switch because its circuit will be open at contact 0 of relay RAR. However, when the operator puts signal RHA at stop, RGP picks up and closes a circuit from terminal B, contact a of RGP, back contact a of relay RMR, winding of time element relay TER to terminal C. Relay TER becomes energized and opens its back contact b disconnecting the terminal B of the source of energy from the signal relay circuits and at the same time sets a time element mechanism into operation which after an adjustable interval usually of from one to four minutes closes contacts a and o of relay TER in the pick-up circuits of relay RMR and LMR, respectively. It follows therefore that in the situation described, relay RMR will eventually become energized to permit the switch to be operated but that this will occur after a time sufficient to permit the approaching train to stop before passing the signal or to have entered section IT. If signal RHA is put to stop due to a train passing it and entering section IT, relay RGP picks up and relay RMR becomes energized as soon as the train in section IT enters 31, so that relays TZ and LAR are deenergized. This circuit is from terminal B, contact a of relay RGP, back contact d of relay LAR, back contact 12 of relay TZ, winding of relay RMR to terminal C. When the switch is reversed, contact (1 of relay LAR in the circuit just described is shunted by the contact e of relay RKR so that relay RMIR will become energized as soon as the train enters section IT. In any case, it will be noted that the switch can not be operated while the train is in section IT by reason of the open contacts d of relays TR and T2 included in the circuit of relay WR. Circuits similar to those just described are provided for the other approach looking relay LMR, which may be energized when the train moving from section 3T enters section 2T, over a circuit from terminal 13, contact a of relay LGP, back contact at of relay RAR, back contact 0 of relay TZ, winding of relay LMR to terminal C, or it may be energized when LHA is put to stop, provided section 3T is unoccupied, over a circuit including front contact 0 of LAB. and front contact e of N'KR. Relay LMR also may be energized by the closing of contact 0 of relay TER and is provided with a circuit for operating relay TER from terminal B, front contact a of relay LGP, back contact a of relay LMR, front contact b of relay RMR, winding of relay TER to terminal 0.

It is clear from the foregoing that the five control relays which I have described constitute means by which the operator may set up a route over switch W and may selectively clear any one of the five signals shown in Fig. 4. The sixth control relay, which is relay NHR, is employed by the dispatcher to open the holding circuits of the signal stick relays to cause any signal that may be clear to return to the stop position.

My system also provides, for the guidance of the operator, indications of six devices at the station, each indication being controlled by means of a relay contact, which may be either opened or closed depending upon the condition of the controlling device. As illustrated, my system provides indications of the normal and reverse positions of the switch, left-hand and right-hand signal indications, and indications of the condition of the track section including the switch and of one adjacent section approaching the switch.

The dispatchers oilice equipment preferably comprises a control board consisting of a number of similarly arranged panels each assigned to one station as illustrated by the typical panel No, 1, which is adapted to control station apparatus arranged as shown in Fig. 4. As shown in the lower portion of Fig. 1, the panel includes a two-position switch control lever WK for selectively controlling the switch stick relays NWSR and RWSR, a three-position signal control lever I-IK for selectively controlling the signal control relays LHSR, RHSR and NI-IR, an auxiliary key UK for controlling relay USR, and a spring return delivery key DK, which may be operated momentarily in order to effect a control of the relays in accordance with the positions of the control levers. The panel also includes, as shown in Fig. 2, indication lamps TE and AE for indicating the condition of the track sections IT and 2T, respectively, of Fig. 4, two switch indication lamps NWE and RWE for indicating that switch W is in the normal or reverse position, respectively, and three signal indication lamps LHE, NHE and RHE for indicating respectively that a left-hand signal is clear, that all signals are at stop, or that a right-hand signal is clear.

Before proceeding to a detailed discussion of the circuits by means of which communication is maintained between the office and the stations, I will first briefly explain the general plan and organization of my system.

Connecting the oflice and each station in turn, I provide three line wires, a message wire X, a stepping wire Y, and a common return wire Z.

Wire X is normally open, while the wires Y and Z complete a normally closed line circuit extending from one terminal of a source of energy LB at the ofiice through contact a at a starting key SK, the winding and front contact a of line relay OR at the ofiice, contact a of switch CK, thence over line wire Y, through the winding of a line relay R and front contact c of a stepping relay S at the first station, thence over outgoing line Y to the incoming line wire Y at the next station and so on, through each station in turn. At the last station, the outgoing wire Y is connected by means of a jumper I4 to the common return Wire Z which completes the circuit back to the ofiice to the other terminal LC of the same source of energy. This normally closed line circuit may be interrupted by momentarily opening starting key SK at the office, or by the release of relay S at one of the stations. Relay S is released as the result of a change in position of one of the six indicating devices at the station. When one of the S relays is released, it opens its contact 0 so that all of the line relays release simultaneously and each line relay releases its associated S relay. Each line relay also operates the first relay of a chain of counting relays which it controls. At a station, these counting relays are designated by the reference figures I to 1, respectively, and at the ofiice by references BI to 01, respectively. The energization of relay I at each station causes the transmitter relay T at the corresponding station to be energized, while at the oflice, the energization of relay 0| causes relay OT to be energized. At each station, therefore, the incoming portion of the line circuit becomes closed from wire Y through the winding of relay R, contact a of relay T, resistor R5 to line wire Z while the outgoing portion of the line circuit leading to the next station remains open at contact 0 of relay S. At the office, the portion of the line circuit leading to the first station is closed through contact b of relay OT which bridges contact a of relay OR so that a stepping circuit is closed and relay OR at the ofiice and relay R at the first station become energized. This causes chain relays 02 and 2 to become energized. Relay 2, when energized, causes relay T to be released to open the line circuit. This releases OR and R and causes 03 and 3 to be energized. The operation of the odd-numbered chain relays thus causes the line to be closed, and the operation of the even-numbered chain relays causes the line to be opened, so that each of the chain relays at station I and in panel No. I at the ofiice, are operated in turn. At the station, the operation of the last chain relay, which is relay I, causes relay S to be energized, so that, when OT picks up, a stepping circuit is closed from the ofiioe through the first station to pick up relay R at the second station to operate relay 2 at the second station, for, as will be remembered, relays I and T at the second station operated when the stepping line first opened. As already explained the ofiice panel for the second station is similar to panel No. I and is connected in series at the right of panel No. I, so that relay 02 of the second panel will be operated simultaneously with relay 2 at the second station. In this manner the operation proceeds, station by station, until relay S at the last station picks up to complete the normally closed line circuit through jumper I4. When this occurs the final relay 08 of the office chain becomes energized and all the relays become restored to their normal inactive condition.

The apparatus so far described thus constitutes a synchronous selector by means of which a series of circuits may be controlled one at a time in sequence over message wire X between the offi'ce and at each station in turn. In addition to this function my stepping circuit is so arranged that it also serves as a means of communication to transmit certain of the indications from the sta tion to the ofiice. This is accomplished by controlling the relative length of the stepping impulses in accordance with the position of station devices. When my system is arranged with three consecutive impulses per station, as herein illustrated, my stepping circuit therefore provides for the transmission of three indications, one for each of the chain relays 2, 4 and E. As illustrated, the system is so arranged that if the switch is reversed the second impulse is prolonged, if the track section IT is occupied, the fourth impulse is prolonged, while if the approach section 2T is occupied, the sixth impulse is prolonged, while under other conditions, each of these impulses is a short impulse.

Simultaneously with the transmission of the three indications over the stepping Wire Y from each station in turn, the three remaining indications are transmitted over the message wire X, thus for example, during the first impulse when relays OR, R, 02 and. 2' are energized, a circuit is closed from one terminal LB of a source of energy at the office, contact of relay 02, winding of message wire line relay RX, contact 0 of relay OR, back contacts 11 of relays 03, 05 and 91, line X, resistor R8, front contact b of relay R, contact e of relay 2, contact f of the normal switch indication relay NKR, wire I5, line wire Z to terminal LC of the source of energy, at the office so that line relay RX becomes energized provided the switch is normal. In a similar manner RX will become energized when relay M is energized, provided the signal indication relay LGP is energized, and again when 06 is energized, provided relay RGP is energized. Relay RX at the ofiice controls indication relays as hereinater described. From the foregoing, it will be clear that when the apparatus is set into operation by momentarily opening wire Y, it operates through a complete cycle during which six indications are transmitted from each station in turn to the office.

When the operator desires to efiect the control of station apparatus, he moves the control levers of the panels for the stations at which he desires to eifect controls to the desired positions and operates the keys DK of these panels to pick up the corresponding delivery relays D. This serves to connect the terminal LB of a source of energy of one polarity to certain of the lever contacts, and the terminal LN of a second source of energy of opposite polarity to the remaining lever contacts. He then momentarily opens the starting key SK and thereby opens line Y and initiates a cycle of operation of thesystem as already described, to cause the transmission of indications from each station in turn; but in this case, control impulses of selected polarity are included in the series of impulses transmitted over the message circuit. The control impulses alternate with the indication impulses over wire X, and are transmitted only when the stepping line is open, and odd-numbered chain relays are energized at the ollice and station. Thus, for example, just after the first indication impulse is transmitted, the stepping line is opened, releasing relays OR and R, and chain relays 03 and. 3- become energized. If relay D of Panel No. 1 is now energized and the normal contact 12 of switch lever WK is closed, a circuit is completed from terminal LB, contact c of relay D, contact n of lever WK, front contact d of relay 03, back contacts d of relays 05 and 01, wire X, resistor R8, back contact 2) of relay R, Winding of polar relay PR, contact e of relay 3, winding of neutral relay 3NR, contacts e of relays LMR and RMR, wires I5 and Z, to terminal LC at the office, causing relay 3NR to be picked up and left-hand contact a of relay PR to be closed to complete a local circuit at station I to energize relay NWSR. If lever WK is in'the reverse position, a circuit is closed similar to that just described except that it extends from terminal LN, over contact b of relay D, contact 1' of lever WK andas already traced over Wire X to energize relay 3NR and to cause contact a of relay PR to close to the right and to thus complete a local circuit for energizing RWSR in place of NWSR. It is thus evident that two controls may be effected in accordance with the polarity of the impulse transmitted over wire X when relay 03 is energized. Two controls may be effected in the same way when relay 5 is energized and two more .when relay I is energized. After the control impulses have been transmitted, relay D is released by the' chain relay which operates next in sequence after relay Ill, thus when the system is employed to control but one station, relay D is released when the final relay 08 of the chain picks up and opens its back contact 01. When the system controls a plurality of stations, this is also true of the last panel, but relay D of each panel except the last will be released when the first chain relay 02 of the next succeeding panel picks up and opens its back contact d. It thus follows that the controls transmitted during one cycle of operation are not repeated during a succeeding cycle.

It is to be understood that my system is not restricted to the control of the particular combination of apparatus that I have described but may be employed to control any suitable combination of apparatus; for example, the station apparatus when arranged to provide three steps per station as illustrated, may be employed to control two separate groups of signals, or to control two switches, or'to indicate six track sections. In one commercially useful modification of my system, wire X is omitted, as well as all apparatus controlled over wire X; relays 2 to 5, inclusive, at each station and relays 02 to 05, inclusive, of each panel are omitted; the remaining apparatusconstitutes a two-wire system for continuously indicating at a centralpoint the condition of a large number of track sections each at a different location along a railroad, which eificiently employs but a small amount of apparatus per station. This apparatus, however operates in exactly the same manner as when it forms a part of the more complete system as herein illustrated.

In addition to the relays already described, my apparatus includes a bridging relay OL at the office, and a similar relay L at the station, which relays are energized intermittently but remain picked up for the duration of the cycle of operation of the apparatus, and are ararnged to drop out and reset the system to normal at the end of the cycle or in case the apparatus is unable to complete a cycle. The ofiice apparatus also includes a slow release relay IL, which belongs the first interval of the cycle, to insure that the relays L at each station have released in case imperfect operation has occurred, and the preceding cycle has not been completed. It also includes a slow release relay 2L, which is employed to register the prolonged indication impulses transmitted over the stepping line. The oiiice equipment also includes relays LP and XP, which operate the indication relays in the panel illustrated in Fig. 2. Each panel includes six indication relays each having the reference character K, with a prefix identifying the device at the station initiating the corresponding indication. Each indication relay controls an indication lamp identified by the reference character E with corresponding prefix, and the track and approach indication relays TK and AK also control an annunciator bell A through the medium of a bell relay AP, which bell is arranged to give a momentary audible indication whenever an approach section becomes occupied. A manually operable key XK is provided, and when this is closed, operation of the bell also occurs when a detector track section becomes occupied.

The station apparatus also includes a normally energized starting relay ST, which becomes deenergized in response to a change in position of any of the indicating devices at the station to initiate the cycle of operation of the apparatus.

The relay circuits include a number of asymmetric units designated Ir to H1, inclusive. Each of these units is so arranged in the circuit that it provides a high resistance to the flow of current from the power source and at the same time provides a low resistance closed circuit including the winding of one or more relays, through which the relay current may continue to flow after the power source is disconnected so that the inductive energy in the relays is discharged gradually with the result that no sparking occurs when the controlling contacts are open. Certain of the relays are shown conventionally on the drawings as slow release relays but each of these relays is timed to release slowly by reason of the short circuit through the relay winding and an asymmetric unit in lieu of the short-circuited winding or ferrule customarily employed. The relays employed in the remote control apparatus of Figs. 1, 2 and 3 with the exception of relays PR and TS in Fig. 3 may be of any suitable type of quickacting relay such for example as the relay illustrated in Patent No. 1,815,947, issued July 28, 1931, to L. V. Lewis. Relay PR is a two-position direct current polar relay of the permanent magnet stick type, while relay TS as well as the relays of Fig. 4 are of the type customarily employed in railway signaling circuits.

I will now trace in step-by-step fashion the operation of my remote control apparatus in receiving indications from a station, but will for simplicity first describe the stepping operations only. I will assume that the station apparatus is in the condition shown in Fig. 4, and a train enters approach section 2T so that relay RAR becomes released. Referring now to Fig. 3, it will be noted that relay R is energized over the normally closed stepping circuit as already described, and relay S is energized by a stick circuit from terminal B, contact a of relay R, resistor R6, contact 0 of relay ST, contact a and winding of relay S to terminal C. Relay ST is energized over a stick circuit from terminal B, back contact 0 of relay TS, front contacts a of relays RAR, RGP, LGP, NWSR and NKR, resistor R1, contact a. and winding of relay ST to terminal C. When relay RAR becomes released, the stick circuit of relay ST just described is opened for a short time, sufficient however to cause it to become released, for the reason that relay ST is a quick-acting relay energized but slightly above its release point by reason of the resistor R"! in its stick circuit, while relay RAR is a much larger relay and is relatively slow in operation. Relay ST when released deenergizes relay S which releases and opens its contact 0 in the stepping line. Relay S releases comparatively quickly in this case because its stick circuit includes a resistor R6 so that it is not highly energized and its stored energy is dissipated through asymmetric unit Sr in a relatively short time. When the stepping line is opened, the line relays R at each station, and relay OR at the oifice are released, and the S relays at each remaining station release quickly and open their 0 contacts so that line Y becomes sectionalized. At each station, when relay R releases, a circuit is closed from terminal B, back contact a of relay R, back contact b of relay L, back contacts 0 of relays 5 and 3, winding of relay I to terminal C. Relay I picks up and completes a circuit which is the same as that just traced as far as relay I and extends then over front contact a of relay I and back contacts b of relays 2 and S, front contact 0 of relay I, winding of relay L to terminal C. Relay L picks up and opens the pick-up circuits just traced but completes a stick circuit for itself from terminal B, back contact a of relay R, front contact 2) of relay L, front contact 0 of relay I, winding of relay L to terminal C and completes a stick circuit for relay I from terminal B, back contact a of relay R, front contact b of relay L, back contacts b of relays S and 2, front contact a and winding of relay I to terminal C, so that relays I and L are energized as long as relay R remains deenergized. When relay I -picks up, a circuit is closed from terminal B, front contact 0 of relay L, contact 6 of relay I, winding of relay ST to terminal C to pick up relay ST and a circuit is closed from terminal B, front contact d of relay I, winding of relay T to terminal C, so that relay T at each station picks up and closes its contact a to complete the portion of the stepping line circuit leading in the direction of the office as already described.

At station I, the apparatus remains in this condition until the stepping line, now open t tact a of relay OR at the office, again becomes closed by the operation of the office apparatus. At each remaining station, the apparatus remains in this condition until the stepping line is closed as the result of the energization of relay S at the next preceding station.

At the office, when the stepping line first opens, relay OR releases and a circuit is closed from terminal B, back contact b of relay OR, back contact 0 of relay OL, winding of relay IL to terminal C. Relay IL picks up and completes a circuit from terminal B, back contact b of relay OR, contact a of relay IL, winding of relay 0| to terminal C. Relay IJI picks up and completes a circuit which is the same as that just traced as far as relay Ill and extends then over front contact a of relay 0 I, back contact I) of relay 02, back contact a of relay 2L, winding of relay OL to terminal C. Relay OL picks up and at contact 0 opens the circuit of relay IL and closes a stick circuit for relay O'I from terminal B, back contact b of relay OR, front contact 0 of relay OL, back contact I)- of relay 82, front contact a and winding of relay ill to terminal C, and closes a stick circuit for relay OL from terminal B, back contact b of relay OR, front contact 0 of relay OL, back contact a of relay 2L, winding of relay OL to terminal C, so that relays OL and DI are held energized. Relay IL remains picked up for a relatively long interval due to the closed circuit including its winding and asymmetric unit 31" and then releases and remains deenergized for the remainder of the cycle of operation of the apparatus, closing its back contact b to complete a circuit from terminal B, back contact b of relay OR, front contact 0 of relay OL, back contact I) of relay IL, winding of relay 2L to terminal C. Relay 2L picks up, and operates its contact a to connect relay OL to the open front contact b of relay OR. Relay OL, however, remains picked up due to the flow of current through its winding and asymmetric unit Ir. When relay 2L picks up, a circuit is completed from terminal B, contact d of relay OL, front contact 0 of relay OI, contact b of relay 2L, winding of relay OT to terminal C. Relay OT picks up and closes a circuit from terminal B, its contact a, through lamp CE to terminal C. Lamp CE is a cycle indicator and is lighted each time that the relay OT picks up during the cycle of operation of the system. Relay OT also closes its contact b and since OL is now energized, the stepping circuit becomes closed from terminal LB, contact a; of relay OL (in parallel with contact a of key SK), winding of relay OR, contact b of relay OT, contact a of key CK, line Y to station I, winding of relay R, contact a of relay T, resistor R5, line Z to terminal LC at the oiiice, thereby initiating the first stepping impulse of the cycle and causing relay OR at the office and relay R at the first station to become energized. The resistor R5 in this branch of the stepping circuit is preferably of such a value that the resistance of the stepping circuit will be the same as that of the normally closed line circuit; this is to say, the resistance of R5 is made approximately the same as that measured between terminals Y and Z, at the station, so that all stepping impulses will be of uniform strength irrespective of the distance of the station from the ofiice.

At the station, when R picks up due to the first impulse, a circuit is closed from terminal B, front contacts a of relays R and L, contact b of relay I, winding of relay 2 to terminal C. Relay 2 picks up and establishes a stick circuit the same as that just traced except that it includes back contact b of relay 3 and front contact a of relay 2 in place of contact b of relay I. Relay 2 opens the closed circuit including the winding and front contact a of relay I, back contact b of relay 2, asymmetric unit Itr and relay I releases. A circuit is then closed from terminal B, front contacts a of relays R and L, back contact a of relay S, back contact 0 of relay I, winding of relay L to terminal C, so that relay L, held picked up by reason of the closed circuit through its winding and asymmetric unit 81', becomes reenergized. When relay I releases, it opens the circuit for relay T, and relay T releases and opens the line to the office, terminating the first impulse.

At the oifice, when OR picks up, due to the first impulse, relay 2L is deenergized, but remains picked up due to the flow of current through its winding and asymmetric unit 5T. A circuit is now closed from terminal B, front contacts b of relays OR, 0L and III winding of relay 02 to terminal C. Relay 02 picks up and establishes a stick circuit which is the same as that just traced except that it includes back contact 12' of relay B3 and front contact a. of relay 02 in place of contact b of relay Ell. Relay 02 opens the closed circuit including the winding and front contact a of relay GI, back contact b of relay 02, and asymmetric unit 21" so that relay 0| releases. When OR picked up, relay OL became reenergized over a circuit from terminal B, front contact b of relay OR, front contact a of relay 2L, winding of relay OL to terminal C. When relay BI releases, relay OT is deenergized and releases. This, however, does not open the line circuit which is now completed through contact a. of relay OR so that the stepping line remains closed until opened at the station, as already described in the preceding paragraph.

At the station, when the line opens, at the end of the first impulse, relay R releases, but relay L remains picked up due to the flow of current through its winding and asymmetric unit ST. A circuit is now closed from terminal B, back contact a of relay R, front contact b of relay L, back contact I) of relay S, back contact a of relay I, front contact b of relay 2, winding of relay 3 to terminal C. Relay 3 picks up and establishes a holding circuit from the same source but including its front contact a and back contact b of relay 4. Relay 3 opens the closed circuit including the winding and front contact a of relay 2, back contact b of relay 3, and asymmetric unit 91' and releases relay 2, and a circuit is then closed from terminal B, front contact cl of relay 3, back contact d of relay 2, winding of relay T to terminal C; Relay T picks up and again closes the line to the ofiice to initiate the second impulse of the cycle.

At the office when the line opens at the end of the first impulse, relay OR releases but relay OL remains picked up due to the flow of current through its winding and asymmetric unit Ir. Relay 2L is reenergized, and a circuit is closed from terminal B, back contact b of relay OR, front contact 0 of relay OL, back contact a of relay I, front contact I) of relay (i2, winding of relay 03 to terminal C. Relay 03 picks up and establishes a holding circuit from the same source butincluding its front contact a and the back contact I) of relay 04. Relay 03 opens the closed circuit including the winding and front contact a of relay 92, back contact I) of relay 03 and asymmetric unit M and releases relay I12. When relay 03 picks up, it again energizes relay OT, over a circuit similar to that previously described except that it includes front contact 0 of relay 03.

It will be noted from the foregoing description that the stepping operation is governed wholly by the station, and that each time that the line at the station becomes closed, the station apparatus causes it to be opened. Each time the line is opened, the station apparatus causes it to become closed. On the other hand, the'stepping apparatus at the office merely serves to hold the line open, when opened by the station, long enough to permit the office chain relays to function, thereby insuring that the ofiice chain relays are held positively in step with station chain relays.

The operation of the stepping apparatus during the remaining steps transmitted by station No. 1 is similar to that during the step just described; that is, when the line is closed for the second impulse, relays 4 and 04 pick up, causing relays 3 and T to be released to open the line, whereupon relays 5 and 05 pick up and relay 4 releases and relay T is energized to again close the line. This causes relays 6 and 96 to pick up, then relays 5 and T release to open the line. This causes relays l and 01 to pick up and relay 6 releases. This is the last step at station No. 1, and a circuit is now closed from terminal 13, back contact 0 of relay 6, front contact 0 of relay 1, winding of relay S to terminal C. Relay S picks up and a circuit is closed from terminal B, back contact a of relay R, front contacts b of relays L and S, back contact 0 of relay I, winding of relay L to terminal C to maintain relay L picked up and the stepping line Y is closed through the winding of relay R, contact 0 of relay S to line Y, to initiate the first stepping impulse to the next succeeding station. When relay R picks up, a stick circuit for relay S is closed from terminal B, front contacts a of relays R, L and S, winding of relay S to terminal C. Relay S is highly energized over this circuit, since resistor R6 is shunted, and is therefore held picked up by the current flow through its winding and asymmetric unit 91" during the intervals between succeeding impulses of the cycle when R is deenergized.

Returning to the operations already described, it will be noted that on the first step, when relay I is energized, relay L is energized over back contact a of relay R. After the stepping operation starts and while relays 2 to l, inclusive, are being energized, relay L is intermittently energized over its own front contact and the front contact of relay R. It follows that if the line becomes steadily opened while the stepping operation at a station is in progress, relay L at that station becomes released thereby deenergizing the chain relay circuits, which include front contacts of relay L, and restoring the station apparatus to the same condition as when the line was initially opened. However, after the stepping operations at a station have been completed, relay S is energized, and during the transmission of impulses by each of the succeeding stations, relay L remains picked up due to its intermittent energization over the front contact of relay S and relay S remains picked up due to its intermittent energization over the front contact of relay R. It follows that if the line becomes steadily opened the apparatus at intermediate stations is restored to the same condition as when the line is initially opened.

From the foregoing description it will be clear that when relay S becomes energized at the first station, line Y is closed from the omce through the winding of relay R and contact 0 of relay S at the first station, winding of relay R and contact a of relay T, and resistor R5 to line Z at the second station so that relay R at that station will pick up to energize relay 2 while at the same time, relay OR at the office will pick up to complete a circuit over front contact b of relay 0'! to energize relay 02 of the second panel, and

relays 2 to I, inclusive, at the second station, and relays 02 and 61 of the second panel at the office will operate in synchronism, then relay S at the second station will become energized to extend the stepping line to the third station, and so on in an obvious manner until the cycle is completed.

The stepping cycle is completed when relay S picks up at the most remote station and connects line Y to line Z over wire l4. When this occurs, relays R and OR become steadily energized. Relay L at each station then releases, opening its contact a so that a resistor R6 and contact 0 of relay ST become included in the stick circuit of each relay S, and these relays again become quick release. At the office, relays 2L, 0L and 08 release consecutively. The apparatus is then in its normal inactive condition. At the oflice, if the line becomes steadily opened during operation of the apparatus, relay 0L is deenergized and releases, opening the circuits for the chain relays and for relays 2L and LP. Relay IL then picks up, and the office apparatus restores itself to the same condition as when the line is initially opened.

From the foregoing description of the operation of the stepping circuits it is evident that if a failure of the stepping line circuit occurs while the apparatus is at rest, a cycle of operation will be initiated. If a failure occurs while the apparatus is operating, it will be stopped when the cycle of operation has progressed to the loca tion of the failure, and in either case, the apparatus will operate in its usual manner to transmit impulses from each station on the office side of the point of failure. When the point of failure is reached and the line becomes steadily open, relay S at each station that has completed its portion of the cycle will release, causing relay L at each station and relay OL at the ofiice to release, thus reestablishing the conditions existing at the beginning of the cycle, and in this manner will initiate a new cycle. Thus when the apparatus is unable to complete a cycle, it will operate repeatedly through the available portion of the cycle.

By this means the fact that a line failure has occurred as well as its approximate location is made manifest to the despatcher so that he can take steps to have the defect promptly repaired.

He may stop the repeated operation of the apparatus by opening key CK, and until the defect is repaired he may operate the apparatus to transmit controls to and receive indications from the available stations by closing One important feature of my invention resides in the normally closed stepping circuit as herein described, which is so arranged that it becomes opened at each station in response to the initial operation of the apparatus. Another important feature resides in the operation of the office apparatus associated with each station by apparatus located at the station, by means of circuits which are so arranged that they are rendered available only when the apparatus at the next preceding station has completed its operation. In this manner, positive and reliable operation of the system is assured. Another feature is the provision of a closed circuit system, which in the event of failure of the closed circuit remains in operative condition out to the point of failure.

As already explained, a. cycle of operation is initiated when relay ST is released at a station and a pick-up circuit is closed for each relay key CK at intervals.

ST during the first interval of the cycle, which is opened again at each station when the station transmits its first impulse. If now, a change in position of any of the devices at a station occurs after a cycle has started, relay ST at that station will be released, provided the change occurs after the pick-up circuit of the relay has been opened and if relay ST is released, relay S will become deenergized at the end of the cycle when relay L is released, and the apparatus will be caused to run through a second cycle of operation. It is clear that by this arrangement, a new cycle is initiated when the indications transmitted do not agree with the positions of the transmitting devices at the end of a cycle.

During the operation of the stepping apparatus as described, indications are transmitted each time line Y is closed, each indication having a character determined by whether the stepping impulse is relatively long or short, and at the same time, an indication is transmitted over line X depending upon whether line X is closed or open, as I will now describe. At the station, when relay 2 is energized, relay l is released and its front contact it opens the circuit of relay T which releases quickly if relay RKR is deenergized so that its contact 1 is open. The stepping circuit therefore remains closed for a relatively short time and slow release relay 2L at the office does not release. When relay 4 picks up, similar conditions exist so that this is also a short impulse, provided contact b of relay TS is open. Since we have assumed that section 2T is occupied and relay RAR is deenergized, it follows that when relay 6 picks up and relay 5 is released to disconnect the source of energy from relay T. The winding of relay T is however now included in a closed circuit from terminal C, asymmetric unit Ilr, back contact a of relay RAR, front contact at of relay 6, back contacts (2 of relays 4 and 2, winding of relay T to terminal C so that relay T remains energized for a time due to the gradual discharge of its stored inductive energy and the stepping line remains closed for a relatively long period. At the office, slow release relay 2L becomes released and a circuit is closed from terminal B, front contact (2 of relay 0L, back contacts 0 of relays 0| and 2L, winding of relay LP to terminal C, so that relay LP becomes energized. When the line opens, relay OR releases and picks up relays 01 and 2L; the latter relay opens the pick-up circuit for relay LP, and relay 0'! establishes a holding circuit for relay LP from terminal B, front contact at of relay OL, front contact c of relay 01, resistor R2, front contact a and winding of relay LP to terminal C.

Referring now to Fig. 2, it will be noted that each of the odd-numbered chain relays has a contact 9 controlling one of the indication relays RWK, TK and AK. When relay 0'! picks up, a circuit is closed from terminal B, contact 17 of relay LP, wire 9, front contact 6 of relay 01, winding of relay AK to terminal C, so that relay AK picks up and establishes a stick circuit which is closed as soon as relay 0'! releases, from terminal B, front contact a of relay AK, back contact e of relay 0T, winding of relay AK to terminal C. If, now, relay RAR at the station becomes energized, its contact 0 will cause relay ST to be released and the apparatus will be caused to run through a cycle in which the impulse transmitted when relay 6 at the station is energized will be short, because relay T will in this case be caused to release quickly, so that at the office, relay 2L will not release and LP will not pick up, and when 01 becomes energized, the stick circuit for relay AK will be opened and relay AK will be released. Relay AK controls an approach indication lamp circuit from over its pick-up circuit during the time relay' 0'! is energized and the holding circuit of relay AK is open. Relay AK therefore is intermittently controlled, but continuously indicates the condition of approach section 2T. When AK picks up, annunciator bell A is also caused to ring as hereinafter described in detail.

When the line becomes closed, the odd-numbered chain relay, in this instance, relay 01 is released so that relay LP is deenergized and becomes available for registering a long impulse when relay 2L again becomes deenergized. From Fig. 2, it is obvious that relays RWK and TK are controlled by relays U3 and D5 in exactly the same manner as AK is controlled by relay 01. Each of these relays controls an indication lamp RWE and TE, respectively, in the same manner as lamp Ali] is controlled. It is evident that if the reverse switch indication relay RKR is energized, its contact 1 is closed and relay 2L will release when relays I32 and 2 are energized, and when relay 03 becomes energized, relay RWK will pick up and establish its stick circuit and light lamp RWE. If track section IT is occupied, relay TZ will be deenergized and a circuit is closed from terminal B, back contact b of relay TZ, wire l2, winding of relay TS to terminal C, so that contact b of relay TS will be closed and relay 2L will release when relays D4 and 4 are energized, and relay TK will become energized to light lamp TE when 05 picks up.

One feature of my invention resides in the circuits of transmitter relay T which, as I have described, are arranged so that at times relay T releases quickly and at other times releases slowly. Prior remote control systems have used relatively short and long impulses and have employed a slow release relay in addition to a transmitter relay. In the arrangement herein disclosed one of these relays is dispensed with and the relative length of the line impulses is determined by a single relay.

Another feature of my system resides in the circuits for relay S, which are so arranged that during the cycle of operation of the apparatus, relay S is a slow release relay and at other times it is a quick release relay. Thus one relay performs the function of two ordinary relays of fixed characteristics.

It is to be noted that the portion of my system so far described, taken by itself, forms a complete and operative system for indicating in sequence at a central office the condition of each of a plurality of remotely located devices at a plurality of spaced stations, and that this indication system employs only one communication channel. More specifically, it employs only a simple direct current line circuit having but one line wire and a common return, for stepping and indicating,

For simplicity, I have arranged the apparatus herein disclosed so that the closed circuit periods of current in the line are of selected length to indicate the condition of station devices. Methods of signaling by selecting the length of open circuit periods intervening in a series of impulses are well known in the art, and it is to be understood that it is a mere matter of choice whether the indications are transmitted when the line is closed, or when it is open, ether method coming within the scope of my invention.

Another feature of my invention resides in the employment of a stick relay OR in the line circuit at the office, so arranged as to provide a positive check upon the operation of the apparatus which it controls to insure that the office ap paratus is held in step with that at the stations.

Referring now to the indications transmitted over the message wire X, when relays 02 and 2 are energized, if we assume that the switch is normal so that indication relay NKR is energized, as shown, a circuit is closed from terminal LB, contact c of relay 02, winding of relay RX, front contact 0 of relay OR, back contacts d of relays e3, 05 and Ell, line X, resistor R8, front contact I) of relay R, front contact e of relay 2, contact of relay NKR, wires I 5 and Z to terminal LC at the office so that relay RX picks up and establishes a holding circuit from terminal LB, contact 0 of relay 02, winding and front contact a of relay RX, resistor R! to terminal LC so that RX remains energized after the stepping line is opened and relay OR is released, until relay 02 becomes released to open its contact 0. When relay RX picks up, it closes a circuit from terminal B over its contact I), the winding of relay XP to terminal C and the latter relay picks up and establishes a holding circuit which is closed when the next odd-numbered chain relay picks up and is the same as that described for relay LP except that it includes resistor R3, front contact a and winding of relay XP. Relay XP is thus held energized after the stepping line opens and E3 is picked up and 82 released and a circuit is then closed from terminal B, front contact b of relay XP, wire ID, front contact 1 of relay 03, winding of indication relay NWK to terminal C, so that relay NWK remains energized, maintaining the circuit from terminal B, and its contact h, lamp NWE' to terminal 0. If, new when relays C2 and 2 picks up, relay NKR at the station is deenergized so that its contact 1 is open, relay RX will not pick up and relay XP will not be energized so that when relay 03 picks up, the holding circuit for NWK, which extends from terminal B and its front contact a over back contact 1 of relay E33 and the winding of NWK to terminal C, will be opened when relay E13 picks up, deenergizing relay NWK to extinguish lamp NWE. The signal indication relays LGP and RGP are provided with contacts as shown in Fig. 3 which control the transmission of indications over wire X, when relays 3 and B, respectively are energized in the same manner as that just described. As shown in Fig. 2, the J contacts of relays 05 and 0'! control indication relays LGK and RGK in the same manner as relay NWK is controlled by relay 03. However, the lamp circuits controlled by these signal indication relays are differently arranged. The signal circuits shown in Fig 4 are, of course, arranged that it is not possible to clear two opposing signals simultaneously, so that it follows that RGP and LGP', and consequently, the indication relays RGK and LGK, can not be deenergized simultaneously, unless a failure of the apparatus occurs. The back contact of each of these relays is therefore employed to light a lamp to indicate that the corresponding signal is clear, and the lamp is prevented from lighting due to a failure of the apparatus by including a front contact of the other indication relay in the circuit. For example, when relay LGK is deenergized, a circuit is closed from terminal B, front contact b of relay RGK, back contact 0 of relay LGK, lamp LI-IEI to terminal 0. When lamp LI-IE is lighted, it therefore indicates that a left-hand signal is clear. Lamp REE has a similar circuit, and when it is lighted, it indicates that a right-hand signal is clear. When both LGK and RGK are energized, a circuit is closed from terminal B, front contact 17 of relay RGK, front contact 0 of relay LGK, lamp NEE to terminal C, so that lamp NHE when lighted indicates that all signals are at stop.

It will be clear from the foregoing that each indication impulse received over wire X occurs while wire Y is closed and an even-numbered chain relay is picked up, and that when an indication impulse is received over wire X, relay XP becomes energized, an indication relay is operated to a position in agreement with the position of relay XP during the next succeeding interval when line Y is open and an odd-numbered chain relay is picked up, and at the beginning of the next following impulse, when line Y is closed, the holding circuit of relay XP is opened so that it is again placed under control of relay RX and is operated to a position in agreement with that of relay RX to register the next indication.

By the employment of the repeating stick relays such as LP and XP I obtain the advantageous result that the stick circuits of the indication relays do not become opened as the apparatus operates through its cycle, except in the case of those relays which are to be deenergized, and the system thus secures continuous energization of energized indication relays when there is no change in indication to be effected. A further advantage in connection with the employment of long impulses for signaling is that in the event that the apparatus stops during a cycle due to a failure of the apparatus, so that 21 is released to falsely register a long impulse, the operation of the indication relay in accordance with the false impulse is prevented. This is accomplished by the use of relay LP to store the indication until the next chain relay of the series is operated. Now if a failure occurs, relay OL- is released and the next chain relay is prevented from operating and relay LP is released, and. therefore the false indication is without effect.

Referring to Fig. 3, it will be note that line X is connected to line X through a front contact d of relay S, so that while indications are being transmitted from a station, any failure of the message line at a more remote point, such as a cross, open, or ground is without effect, when the transmission of a station is completed and releay S picks up, the message line is then completed to the next succeeding station. Resistor R8 in the branch of the message line at the station is a compensating resistor preferably oi the same value as the resistance of the portion of the message line circuit leading to the most remote station and is provided so that all impulses transmitted over wire X may be of uniform strength.

Returning now to the circuits for the annunciator bell A, one feature of my invention resides in the provision of simple means whereby bell A may be caused to sound momentarily each time any one of the approach or track indication relays becomes energized. Each of the indication relays TK and AK is provided with a continuity transfer, or make-before-break contact c which is illustrated in detail in Fig. 5 and comprises a flexible spring member 0 adapted to be moved by the armature of the relay, a fixed member or back contact 0" and an intermediate member 0 biased to make contact with (2" when the relay is deenergized. To the spring 0, I have added an inertia weight m so that when the relay becomes energized and spring 0 is moved upward rapidly against m, spring 0 will become compressed due to the inertia of the mass m, and will remain in contact with c, for an appreciable time before 0' is lifted out of contact with 0. Thus, when relay AK becomes energized, a circuit is closed momentarily from terminal B, contacts 0, c and c, resistor R4, winding of relay AP to terminal C. Relay AP is of relatively low resistance and since resistor R4 is in series with its winding, the time constant of its circuit is small so that it picks up rapidly and when energized momentarily, releases slowly by reason of the continued flow of current through its winding and asymmetric unit 71. Under these conditions, it will be noted that when the voltage of the local source of energy is high, and the speed of pick up of relay AK is thereby increased so that the period of contact between springs c and c" is shorted, the higher voltage will also be applied to relay AP, with the result that the length of time relay AP remains energized is substantially constant irrespective of voltage variation. When relay AP becomes energized, a circuit is closed from terminal B, contact a of relay AP, annunciator bell A to terminal C and when this circuit is opened, sparking of the contact of relay AP is prevented by reason of the discharge path provided for the current in the winding of bell A through asymmetric unit 51*.

When relay AK becomes deenergized, spring 0 moves downward rapidly for the reason that the armature portion of the relay is of small inertia, and is moved downward not only by spring a but by the other springs a and b of the usual type shown in Fig. 2 and which are structurally illustrated in Patent No. 1,815,947 to which I have referred. Spring 0, however, moves downwardly more slowly because its acceleration is diminished by the mass m, from which it follows that springs c and 0 separate almost as soon as 0 starts to move and therefore springs c and c are separated when 0 engages with back contact 0". It follows that the bell circuit is closed momentarily by relay AK only when relay AK becomes energized, and that it is not closed when relay AK is deenergized. When the manual key XK is closed, a circuit for relay AP is provided which includes the bell contact 0 of relay TK, as is obvious from the drawing. It is also evident that a plurality of indication relays may be connected to the circuits as shown, to operate relay AP without interference.

Referring now to Fig. 3, it will be noted that the circuits for controlling indication relay TK include a relay TS not provided in the circuits for the control of relay AK. This is for the reason that in practice the detector track section IT is usually very short, and it may occur that a short train will pass entirely through a section such as IT, and be out of the section before the indication transmitting circuit becomes available in the cycle of operation of the apparatus. Relay TS is therefore provided to insure that lamp TE will be lighted each time the train passes through section IT. As is self-evident, this expedient may 1 be applied to the control of other indications if desired. Assume now that relay TZ is deenergized momentarily and then picks up, TS will become energized and in picking up, will momentarily open at its contact 0 the holding circuit for relay ST which releases and establishes a holding circuit for relay TS from terminal 13, back contact I) of relay ST, front contact a and winding of relay TS to terminal 0 so that relay TS is held energized. The release of relay ST sets the apparatus into operation causing relays L and l to be picked up and relay ST to be energized but the holding circuit for relay TS is maintained from terminal B, contact 0 of relay L, front contact I) of relay ST, contact a and winding of relay TS to terminal C. When relay 4 is energized, the release of relay T is delayed by reason of the closed circuit from terminal C, winding of relay T, back contact d of relay 2, front contact d of relay d, contact I) of relay TS, asymmetric unit Hr to terminal C which results in picking up indication relay TK even though the relay T2 at that time is energized. At the end of the cycle of operation, relay L releases and deenergizes relay TS, and TS in releasing momentarily opens the holding circuit for relay ST to start a new cycle of operation during which indication relay TK will be released.

I will now assume that the apparatus of Fig. 4

is in the positions shown and that the operator desires to clear signal RHB to move a train from section 2T to section 4T. He will reverse lever WK to close contact 1" and will operate signal lever HK to close contacts 7 and 1" and open contact n and will then momentarily operate the delivery key DK, closing a circuit from terminal B, contact a of key DK, winding of relay D to terminal C. Relay D picks up and establishes a holding circuit from terminal B, and the back contact at of the relay 92 of the next succeeding panel, or in case the system includes but one station of relay (38, thence through front contact a and winding of relay D to terminal C. The operator then momentarily operates starting key SK to open the stepping line Y to initiate the cycle of operation of the system as hereinbefore described. As soon as relay 0L picks up, energy for the stepping line is rendered available by reason of the branch of the line circuit from terminal LB, front contact a of relay OL to the right-hand terminal of relay OR, and line energy is also available by reason of the connection to key SK as soon as this key is released by the operator.

The system now operates as already described to transmit indications from each of the devices in turn. However, the operation of the system as a result of the energization of relay D differs from that previously described in that control impulses are transmitted over wire X when relays 83, U5 and ll! are energized. Thus, when OR is released at the end of. the first stepping impulse, relays U3 and 3 are energized, and an impulse of reverse polarity is transmitted from terminal LN, front contact b of relay D, contact 1" of lever WK, front contact 11 of relay 83, back contacts d of relays 05 and (ll, wire X, resistor R3, back contact b of relay R, winding of relay PR, contact 6 of relay 3, winding of relay SNR, front contacts e of LMR and RMR, wires i5 and Z to terminal LC at the ofiice, causing 3NR to pick up and PR to close its right-hand contact a, and closing a local circuit from terminal B, contacts a of relays PR and 3NR, winding of. relay RWSR to terminal C. Relay NWSR, which has been energized over a circuit from terminal B, contact I) of dual selector DS, wire ii, back contact b of relay RWSR, front contact a and winding of NWSR to terminal C, now becomes released, and relay RWSR is held energized over a branch of the same circuit from wire ll, back contact b of relay NWSR, front contact a and winding of relay RWSR to terminal C. The circuit for relay SNR just described includes a group of contacts at the lower right of Fig. 3 which are for the purpose of preventing operation of the switch stick relays under certain conditions. For example, if. signal Rl-IB is clear, relay RGP and consequently RMR will be deenergized. If a train is approaching the signal, relay RAR will also be deenergized, and the circuit for SNR will be open at contacts e of relays RMR and RAR. Similarly, if signal LHA is clear, and the train is approaching it and is in section 3T, relays LMR and LAR will be released and the energization of 3NR is prevented. If signal LHB is clear, relays LMR and NKR are deenergized, and the operation of 3NR is prevented. It follows therefore that the operator is by this means prevented from inadvertently causing the signal to indicate stop in front of an approaching train as the result of an attempt to operate a switch. If, however, the train passes a signal and enters section lT, relay TR releases closing its back contact e which shunts the circuits just described and permits the operation of the switch stick relays, although of course, in this case the switch is not permitted to move until after the train passes out of the section IT, on account of contacts d of relays TR and TZ in the circuit of relay WR.

Returning now to the description of the control impulses, when the stepping line becomes closed to begin the second stepping impulse, relay R picks up, opening its back contact b to terminate the control impulse and then picks up relay 4 while at the same time relay OR picks up relay D4 which releases 63. When relay t3 closes its back contact an indication impulse may be transmitted to pick up RX. When relays OR and R release, at the end of the second stepping impulse, relay R opens its front contact I) to terminate the indication impulse and picks up relay 5, while relay OR disconnects RX and picks up relay 05. My system thus provides a definite positive spacing between the consecutive control and indication impulses. When )5 picks up a control impulse is transmitted similar to that last described but including contact 1' of signal lever HK, front contact d of relay E25, and at the station including contact 6 of relay 5, and winding of relay 5NR, to pick up RHSR as is obvious from the drawing. A holding circuit for RHSR is now closed from terminal B, front contact b of relay TR, wire l3, back contacts 22* of. relays Nl-IR and LHSR, front contact a and winding of relay RHSR to terminal C.

At the end of the third stepping impulse, no control impulse is transmitted in this instance so that relays USR and NSR remain deenergized. When relay RWSR picks up, it completes the circuit for switch control relay WR as already described to cause this relay to be energized in the reverse direction to operate motor M and reverse the switch.

Referring now to Fig. 3, it will be noted that the holding circuit of the starting relay ST includes a front contact 0 of relay RWSR which is now closed and bridges contact 0 of the normal indication relay NKR so that relay ST is not released when relay NKR releases at the beginning of the switch operation. However, since relay NWSR is now released and its contact 0 is open, the circuit of relay ST will be momentarily opened at contact 0 of relay RKR when the switch completes its operation and relay RKR picks up, and relay ST Will then be released to initiate the operation of the apparatus. When relay RKR picks up it also completes the circuit for signal relay RBHR, which releases relay RGP, so that the indications transmitted will indicate to the despatcher that the switch is reversed and that the right-hand signal has been cleared.

If, now, a train passes the signal, the signal stick relay RHSR is deenergized by the opening of contact b of relay TR. Relay TR also deenergizes relay TZ which then closes its back contact a connecting terminal B to wire I3 to prepare a holding circuit for the signal stick relays, so that these relays may be picked up by the operation of the apparatus while a train is still occupying section IT. However, if the operator desires to deenergize these relays to cause the signal to indicate stop, he may do so at any time by operating his keys DK and SK while the signal lever SK is on center and in which case a control impulse will be transmitted over the circuit from terminal LN, front contact b of relay D, contacts n' and n of lever HK, front contact d of relay 91, wire X, resistor R8, back contact b of relay R, winding of relay PR, contact e of relay 1, winding of relay 'INR, wires l5 and Z terminal LC at the office. Relay PR will close its right-hand contact a and complete a circuit from terminal B over contacts a of relays PR and ENR, winding of relay NHR to terminal C. Relay NHR will pick up and at its contact 2) will open the holding circuit for relay LHSR, RI-ISR, or USR momentarily to cause these relays to be released.

If, now, the operator desires to clear signal RHC, he operates signal lever HK to close con tacts r and r and closes key UK, and also restores switch lever WK to normal to close contact n, and momentarily operates keys DK and SK. This results in the transmission of a first control impulse from terminal LB, contact 0 of relay D and contact 12 of lever WK, over front contact (1 of relay 03, a second control impulse from terminal LN, contact b of relay D, and contact r of lever HK, over front contact 11 of relay 15, and a third control impulse from terminal LB, contact 0 of relay D, contact a of key UK, and contacts r and n of lever HK, over front contact d of relay 07. These impulses are transmitted consecutively and at the station energize respectively the relays NWSR, RHSR and USR as is obvious from the drawing.

One of the advantages of the employment of individual delivery keys DK in a system of this character is that it insures that none of the switch and signal stick relays at the station will become energized due to the operation of the apparatus except as a result of a deliberate act by the operator. For one example, if we assume that the operator gives a train crew permission to do switching at a station, the movement of a selector lever DS to the hand throw position causes its contact b in the circuits of relays NWSR, RWSR, NKR, RKR and TZ to open, so that the signals indicate stop, and occupied track and stop signal indications are displayed on the panel, and both switch indication lamps are dark. When the selector lever is restored to the motor position, a clear track indication will be displayed and the switch indication will be restored. The train, however, will not obtain a clear signal to permit it to leave the station until the operator, observing that the indications of the panel have been restored to normal, operates key DK so as to reestablish his control over the switch and signal at the station. For another example, assume that a train passes through a section; the signal stick relays become deenergized and will not again become energized to clear a signal for a following train unless the operator operates key DK, even though the apparatus operates through repeated cycles for the transmission of indications.

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

Having thus described my invention, what I claim is:

1. A centralized traffic control system for railroads of the synchronous selector type comprising an office and a plurality of stations distributed along the railway track, stepping apparatus for transmitting selected ones of a series of spaced control and indication impulses one at a time in sequence from the office to each station in turn during a single cycle of operation of said apparatus, a series of indicators at the ofiice including one for each indication impulse, and each operable to one position when a particular indication impulse is included in said series and to another position when said impulse is omitted; a plurality of stick relays at the stations, including one for each control impulse, and each perable to its energized position when a particular control impulse is included in said series, a plurality of stick relays at the ofiice, including one for each station, means controlled by each of said office stick relays for including selected control impulses in said series of impulses to operate corresponding stick relays at a particular station only, a manually operable key for energizing each oilice stick relay, and means at the ofiice and at each station for initiating the cycle of operation of said apparatus.

2. Remote controlling apparatus comprising a normally closed line circuit extending from a control office to a plurality of stations and including in series a normally energized line relay at each station, a transmitting contact at each station, and a normally energized sectionalizing relay having a front contact in the line circuit at each station, a holding circuit for each sectionalizing relay arranged to be opened if the associated line relay becomes deenergized means for opening the line circuit to deenergize each line relay, means at each station responsive to the deenergization of the line relay at the station for closing the portion of the line circuit from the office through the line relay and transmitting contact at said station, and means controlled by said line relay and transmitting contact for energizing the associated sectionalizing relay to restore the line circuit from the ofiice through said station to the next station.

3. In a remote control system, an oifice and a plurality of stations connected by a normally closed line circuit, sectionalizing means at each station effective when operated to open the portion of the line circuit leading from the office through said station to the next succeeding station, transmitting means at each station for shunting said open portion to permit the portion of the line circuit leading from the oiiice to said station to become closed, means for operating said transmitting means repeatedly provided each operation of the transmitting means causes said portion to become closed; means efiective when the sectionalizing means at any station is operated for operating the sectionalizing means at each of the remaining stations and for causing a first operation of the transmitting means at each station, and means at each station responsive to a repeated operation of the transmitting means at said station to restore the sectionalizing means at said station to thereby close the line from the ofiice through said station to the next succeeding station.

4. In a remote control system, an oflice and a plurality of stations connected by a line circuit, sectionalizing means at each station effective when operated to open the portion of the line circuit leading from the ofiice through said station to the next succeeding station, a contact at each station for shunting said open portion to permit the portion of the line circuit leading from the oiiice to said station to become closed, starting means at each station for operating the sectionalizing means at such station, means effective when the sectionalizing means at any station is operated for operating the sectionalizing means at each of the remaining stations, and means responsive to the operation of each sectionalizing means for closing the contact at the corresponding station.

5. Remote indication apparatus comprising a normally energized line wire connecting an ofiice and a station, manually controlled means at the office for at times momentarily deenergizing said line Wire, means operating in response to said momentary deenergization to produce a series of stepping impulses in the line Wire, indication means at the office selectively controlled in accordance with the character of said stepping impulses, and automatic means at the station for at times momentarily deenergizing said line wire.

6. In combination, a normally closed circuit including a line wire connecting an oiiice and a station, a series of movable devices at the station, means operating in response to a change in the position of any one of said devices to open said circuit, means responsive to the opening of said circuit for closing an indication circuit from the office to the station over said line wire under the control of one of said devices, and means responsive to the closing of said indication circuit for again opening said circuit and for closing an indication circuit from the office to the station over said line wire under the control of the next succeeding device of said series.

'7. In combination, a normally closed circuit including a line wire connecting an office and a station, a series of movable devices at the station, means set into operation by a change in the position of any device to open the line circuit, means set into operation by the opening of the line circuit to deliver to the line circuit an indication impulse under the control of the first device of the series, a plurality of indicators, one for each device, means responsive to each indication impulse to condition the indicator in accordance with such impulse and to connect the line wire with means for delivering an indication impulse under the control of the next device in said series.

8. In combination with a line wire connecting an office and a plurality of stations and included in. a normally closed circuit, a series of movable devices at least one located at each station, a plurality of transmitter relays one for each station, means set into operation by a change in the position of any particular device for opening said line circuit to actuate each of said transmitter relays, and means controlled by said transmitter relays when actuated for delivering to said line circuit a series of indication impulses including one for each device in turn, and indication means at said ofiice selectively controlled by said indication impulses.

9. In a remote indication system, an. oflice and a remote station connected by a single normally closed line circuit, a series of devices at said oifice and station, impulse transmitting means operating over said line circuit and initiated by the opening of said line circuit to actuate said devices, each to a position selectively determined by a particular impulse, and a plurality of mechanisms one for each of said impulses for selecting the device to be actuated to a position selectively determined by the next succeeding impulse.

10. In a remote indication system, an office and a plurality of remote stations connected by a single normally closed line circuit, a series of devices at said oiiice and stations, impulse transmitting means initiated by the opening of said line circuit to actuate said devices, each to a position selectively determined by a particular impulse, and a plurality of mechanisms one for each of said impulses and including at least one at each of said stations for selecting the device of which the position is to be determined by the next succeeding impulse, and means at each station effective when the last device at a station has been actuated for maintaining said line circuit closed from the office through said station to the next succeeding station.

11. In combination, a relay, a contact adapted to be closed at times to complete a circuit through the relay winding and a source of energy, a second contact adapted to be closed at times to complete a circuit including the relay winding and an asymmetric unit to provide a low resistance discharge path for the relay energy to delay the release of the relay when the first circuit is opened, and means for selectively closing said second contact.

12. In combination, a relay, a contact adapted to be closed at times to complete a circuit through the relay winding and a source of energy, a second contact adapted to be closed at times to complete a circuit including the relay winding and an asymmetric unit to provide a low resistance discharge path for the relay energy to delay the release of the relay, and means for selectively controlling said second contact to cause the relay to be quick in releasing when the first contact is opened provided the second contact is then open and to be slow in releasing when the first contact is opened provided the second contact is then closed.

13. Means for selectively controlling the release period of a slow release relay comprising a pick-up circuit for energizing the relay, a first stick circuit for maintaining the relay highly energized including the winding and a front contact of the relay and an auxiliary contact, a second stick circuit for maintaining the relay energized but slightly above its releasing point including the winding and a front contact of the relay and a resistor, a holding circuit including the relay winding and an asymmetric unit providing a low resistance discharge path to delay the release of the relay when deenergized in accordance with the degree to which it has been energized, means for momentarily closing the pick-up circuit to cause the relay to be picked up to be held energized provided one of said stick circuits is closed, and means for opening the said stick circuits to release the relay, and means for at times holding said auxiliary contact closed to cause the relay to be slow in releasing if the stick circuits are then opened.

14.. In a remote control system, an ofiice and a plurality of stations connected by a normally closed line circuit, a sectionalizing relay at each station normally effective when deenergized to release quickly to open the portion of the line circuit leading from the ofiice through said station to the next succeeding station, means for deenergizing each sectionalizing relay when the line circuit is opened, means operating progressively in response to said opening of the line circuit to transmit a series of spaced impulses from the oifice to each station in turn to reenergize each sectionalizing relay in turn to reestablish the normally closed line circuit, and auxiliary means at each station for preventing the sectionalizing relay at said station from releasing while said series of impulses is being transmitted unless said line circuit becomes opened for a period longer than the intervals between said impulses.

15. In a remote control system, an office and a plurality of stations connected by a line wire, a series of movable devices at least one located at each station, means set into operation by a change in position of any particular device for transmitting an impulse from the ofiice to the nearest station, means at each station rendered effective when an impulse transmitted to said station is terminated for initiating the transmission of an impulse from the ofiice to the next succeeding station, means at each station controlled by the movable device at said station for causing the impulse transmitted to said station to be relatively long when the device is in one position and to be relatively short when the device is in a different position, indication means at the office for said movable devices, and means for controlling said indication means in accordance with the relative length of said impulses.

16. A remote indication system for railroads comprising a plurality of devices distributed at spaced points along a railway, a single line circuit connecting each of said devices with a control ofiice, impulse transmitting means adapted to operate over said line circuit, means responsive to a change in condition of any of said devices to set said impulse transmitting means into operation to transmit a series of impulses, one to each device in turn, means for controlling the length of each impulse in accordance with the condition of the corresponding device, a series of indicators at the control office, one for each device, and means for selectively controlling each of said indicators in accordance with the length of the impulse transmitted to the corresponding device.

17. In combination, a normally closed circuit including a line Wire connecting an office and a plurality of stations, a series of movable devices at least one at each station, a series of indicators at the ofiice, one for each movable device, a series of impulse transmitters, one at each station, means set into operation by a change in position of any particular device for opening said circuit and for successively actuating said transmitters to deliver to said line wire a series of impulses, means at each station for controlling the length of each impulse delivered by the transmitter at such station in accordance with the position of the corresponding device, and means at the ofiice for actuating each of said indicators to one position or another, each in accordance with the relative length of a particular impulse of said series.

18. In a centralized traflic control system for railroads, the combination of a central office and a plurality of way stations along the railway track, of a master synchronous selector at the office, a wayside synchronous selector distributed along the track having a series of elements each corresponding to a different element of the ofiice selector, a portion of said series being located at each Way station, said selectors including stepping means for placing each element of the oifice selector in turn in communication with a corresponding element of a way station selector, and means controlled in accordance with the length of time that each element of the ofiice selector is maintained in communication with the corresponding element of a station selector for controlling an indicator at the ofiice in accordance with the condition of a railway traffic governing device at one of the stations,

19. A remote control system comprising an office and a plurality of stations, an impulse transmitter and a starting relay at each station, a normally closed starting circuit at each station including a front contact and the winding of the starting relay, control means at each station for momentarily opening the starting circuit to deenergize the starting relay at said station, starting means at each station responsive to the deenergization of any one of said starting relays to actuate said impulse transmitters to transmit an impulse to the ofiice from each of said stations in turn, in a single cycle of operation.

20. A remote control system comprising an office and a plurality of stations, an impulse transmitter and a starting relay at each station, a normally closed starting circuit at each station including a front contact and the winding of the starting relay, control means at each station for momentarily opening the starting circuit to deenergize the starting relay at such station, starting means responsive to the deenergization of any one of said starting relays to actuate said impulse transmitters to transmit an impulse to the ofiice from each of said stations in turn, in a single cycle of operation, and means controlled by said starting means for picking up each starting relay deenergized prior to the transmission of an impulse to the corresponding station during said cycle.

21. In combination with a line circuit, a winding and a front contact of a line relay in said line circuit, a second relay having a normally open front contact adapted when closed to bridge the contact of said line relay, a series of contacts, means controlled by said line relay for actuating said contacts one at a time in order in response to consecutive similar operations of said line relay, and means including said contacts for energizing said second relay.

22. In combination with a line circuit, a winding and a front contact of a line relay in said line circuit, a normally open contact adapted when closed to bridge said front contact, stepping means adapted to be operated by repeated deenergization and reenergiza-tion of said line relay, means controlled by said stepping means when operated by each dee-nergization of the line relay, to close said normally open contact, said means being also controlled by said stepping means, when operated by each energization of the line relay, to open said contact.

23. In combination with a line circuit, a winding and a front contact of a line relay in said line circuit, a normally open contact adapted when closed to bridge said front contact, stepping means adapted to be operated by repeated deenergization and reenergization of said line relay, means controlled by said stepping means when operated by each deenergization of the line relay to close said normally open contact until the line relay again becomes energized.

24. In a remote control system, a receiver comprising a line relay, a series of contacts adapted to be closed one at a time in sequence in response to repeated operations of the line relay by a series of impulses of current, means for prolonging selected ones of said impulses, a series of indication stick relays, one for each impulse, and means rendered effective at the termination of each impulse for opening the stick circuit of the corresponding indication relay, and for simultaneously closing a pick-up circuit for said relay only if said impulse is a prolonged element.

25. In a remote control system, a receiver comprising a line relay, a series of contacts adapted to be closed one at a time in sequence in response to repeated operations of the line relay by consecutive elements of series of spaced impulses of current, means for imparting a particular character to selected ones of said elements, a series of indication stick relays, one for each element, and means rendered effective at the termination of each element for opening the stick circuit or" the corresponding indication relay, and for simultaneously closing a pick-up circuit for said relay only if said element is of said particular character.

26. In a remote control system, a receiver comprising a two-position line relay adapted to be operated repeatedly by consecutive elements of a series of spaced impulses or" current, a slow release relay adapted to become released when the line relay remains in one of the said two positions for more than a predetermined time interval, a stick relay, means for picking up said stick relay when the slow release relay is released, a series of indication relays, one for each element, means rendered effective each time the line relay moves to the other of said two positions for energizing a selected one of said indication relays provided said stick relay is energized, and means for releasing said stick relay.

27. In a remote control system, a receiver comprising a two-position line relay adapted to be operated repeatedly by consecutive elements of a series of spaced impulses of current, a slow release relay adapted to become released when the line relay remains in one of the said two positions for more than a predetermined time interval, a stick relay, means for picking up said ti k relay when the slow release relay is released, means for reenergizing said slow release relay when the line relay moves to the other of said two positions, means for releasing said stick relay when the line relay is again moved to said one position, and indication means controlled by said stick relay.

28. In a centralized traflic control system for railroads, the combination with an office and a plurality of stations, a track circuit at each of said stations, a line wire and a common return normally completing a closed line circuit connecting the omce and each of the stations, selector apparatus at the office and at each of the stations effective to successively indicate the condition of occupancy of each of said track circuits in a single operating cycle by means of a series of current impulses transmitted over said line wire and common return, means at each station for momentarily opening said line circuit in response to a change in condition of any track circuit, and means responsive to the opening of said line circuit to initiate the operating cycle of said selector apparatus.

29. In a synchronous selector remote control system, an oflice and a plurality of stations, a stepping wire and a message wire connecting the ofiice and each of said stations, a plurality of movable devices at least one at each station, a plurality of indicators at the office, one for each device, synchronous stepping means controlled over said stepping wire for operating each of said indicators in turn over said message wire, each in accordance with the position of the corresponding movable device, sectionalizing means at each station efiective when operated to open the message wire to the next succeeding station,

r-1 means responsive to a change in position of any movable device for operating all of said sectionalizing means and for setting the synchronous stepping means into operation, and means controlled by the synchronous stepping means for restoring the sectionalizing means at each station in turn when the indicator corresponding to said station has been operated to prepare a circuit from the office over said message wire to the next succeeding station,

30. In a synchronous selector remote control system, an oflice and a plurality of stations, a stepping wire and a message Wire connecting the office and each of said stations, a plurality of electromagnetic devices at least one at each station, a plurality of control levers at the ofiice one for each device, synchronous stepping means controlled over said stepping wire for operating each of said devices in turn over said message wire, each in accordance with the position of the corresponding control lever, sectionalizing means at each station effective when operated to open the message wire to the next succeeding station, means for operating all of said sectionalizing means and for setting the synchronous stepping means into operation, and means controlled by the synchronous stepping means for restoring the sectionalizing means at each station in turn when the device at said station has been operated to prepare a circuit from the ofiice over said message wire to the next succeeding station.

31. Means for continuously indicating whether or not a contact is closed located at the remote end of an intermittently available line circuit, comprising an indication relay, a pick-up circuit and a stick circuit for said relay, a line relay and a source of current for said line circuit for energizing said line relay each time the circuit is rendered available and the remotely located contact is closed, a stick repeater relay, means for energizing said stick repeater relay when said line relay becomes energized, means for maintaining said stick repeater relay energized for a brief period after said line circuit has ceased to be available and for then releasing it, means for opening the stick circuit of the indication relay for the duration of said period and for simultaneously closing the pick-up circuit of said indication relay provided said stick repeater relay is then energized.

32. Means for continuously indicating whether or not each of a series of contacts is closed each located at the remote end of an intermittently available line wire, comprising means for intermittently connecting said line wire to each of said contacts in turn, a series of indication relays, one for each contact, a stick relay, means for opening the stick circuit of said stick relay each time said line wire is rendered available and for closing the pick-up circuit of said relay provided the contact then connected to said line wire is closed, means for closing the stick circuit or said stick relay if said relay is energized, when said line wire becomes disconnected from said contact, and for then operating the indication relay corresponding to said contact to a position in agreement with the position of said stick relay.

33. Means for continuously indicating whether or not each of a series of contacts is closed each located at the remote end of an intermittently available line wire comprising means for intermittently connecting said line wire to each of said contacts in turn, a series of indication relays, one for each contact, a stick relay, means for opening the stick circuit of said stick relay each time said line wire is rendered available and for closing the pick-up circuit of said relay provided the contact then connected to said line wire is closed, means for closing the stick circuit of said stick relay if said relay is energized, for the duration of a succeeding interval when said line wire is not available, and means for operating the indication relay corresponding to said contact to a position in agreement with the position of said stick relay.

34. A synchronous selector remote control system comprising an ofiice and a station, a stepping line and a message line connecting the office and said station, a line relay and a source of current at the oifice and a line relay at said station in said stepping line, a series of contacts at the office and a series of contacts at the station, each arranged to be closed one at a time in sequence as the corresponding line relay is actuated repeatedly, the odd-numbered contacts oi each series being closed when the corresponding line relay is deenergized and the even-numbered contacts of each series being closed when the corresponding line relay is energized, a plurality of intermittently available indication circuits each including said message line, a source of current, a relay at the ofiice, front contacts or" the office and station line relays, and corresponding evennumbered contacts of the series at the office and station respectively, a plurality of intermittently available control circuits, each including said message line, a source of current, a relay at the station, back contacts of the office and station line relays, and corresponding odd-numbered contacts of the series at the office and station respectively, and means for transmitting current impulses over said control and indication circuits when available.

35. A synchronous selector remote control sys-

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