US2479684A - Means for reducing code distortion in coded signaling systems - Google Patents

Description

Aug. 23, 1949. A. HUFNAGEL 2,479,684

MEANS FOR REDUCING CODE DISTORTION IN CODED SIGNALING SYSTEMS Filed Aug. 20, 1947 .B 0 ,zazocl fi EZH a BMW B 0 ijabp 750T U Hg I --VS 3 lg Fig; 1

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Andi/i age] BY His Aitorzzey Patented Aug. 23, 1949 MEANS FOR REDUCING CODE DISTORTION IN CODED SIGNALING SYSTEMS Andrew Hufnagel, Penn Township, Allegheny County, Pa., assignor to The Union Switch & Signal Company, Swissvale, Pa., a corporation of Pennsylvania Application August 20, 1947, Serial No. 769,718

8 Claims.

My invention relates to coded signaling apparatus and particularly to improved means for causing the contacts of a repeater code following relay to occupy each of their two positions for substantially equal time intervals irrespective of variations in the operation of the controlling relay.

In some types of coded signaling apparatus as, for example, coded track circuit signaling systems for railroads, code detecting means is employed to detect code following operation of a relay. The code detecting means is constructed so that it operates most satisfactorily if the contacts of the controlling relay occupy each of their two positions for substantially equal time intervals. In systems of this type the means for supplying coded energy to the track rails at one end of a section of railway track is arranged so that the impulses of energy are supplied at a uniform rate, such as 75 or 180 times per minute, and the lengths of the impulses and of the intervals between successive impulses are of substantially equal duration. However, because of changes in the voltage of the track batteries, in ballast resistance, or other operating conditions, or the necessity of repeating the coded energy through one or more out sections, the energy received by the code following track relay at the other end of the section may be distorted in Wave form so as to cause the relay contacts to occupy one of their two positions an abnormally large proportion of each cycle with the result that the code detecting means governed thereby may not operate properly.

An object of this invention is to provide means governed by a code following relay for operating a repeater relay so that the periodically operated contacts of the repeater relay will occupy each of their two positions for Substantially equal periods of time even though the periods during which the contact of the code following relay occupies one of its two positions are materially longer or shorter than the periods during which it occupies the other of its two positions.

A further object of theinvention is to provide improved means of the type described which is relatively immune to changes in operating conditions.

Another object of the invention is to provide improved means of the type described which is arranged so that the repeater relay does not consume energy when the code following relay by which it is controlled is not responding to coded energy.

A further object of the invention is to provide means of the type described which is arranged so that on the start of code following operation of the code following relay the repeater relay will not respond to cause operation of the code detecting means until the code following relay contacts have operated several times.

Another object of the invention is to provide improved means of the type described which is arranged so that defects or irregularities in the circuits of the repeater relay cannot result in code following operation of this relay except in response to operation of the controlling relay, and cannot result in operation of the repeater relay at a more rapid rate than the controlling relay.

A further object of the invention is to provide improved means of the type described for controlling a repeater relay so that the repeater relay will respond to operation of the controlling relay at different code speeds and will compensate for inequalities in the closed periods of the contact of the controlling relay regardless of the code speed at which the controlling relay is operated.

Other objects of the invention and features of novelty Will be apparent from the following description taken in connection with the accompanying drawings.

I shall describe one form of my invention and shall then point out the novel features thereof in claims.

In practicing my invention, I provide a repeater code following relay of the polar stick type and employ this relay to govern the code detecting means or perform other functions. In one Dosition of the contact of the control relay I connect the winding of the repeater relay across the terminals of a source of direct current in series with a condenser so that energy of the polarity effective to move the contacts of the repeater relay to one position is supplied through the relay winding during the charging of the condenser. In the other position of the contact of the control relay contact the condenser is connected across the terminals of the winding of the repeater relay so that energy stored in the condenser discharges through the relay winding and is of the polarity effective to move the contact of the repeater relay to its other position. The rate of response of the contact of the repeater relay varies in accordance with the level of the charge built up in the condenser and this varies in accordance with the proportion of the time during which the contact of the controlling relay occupies each of its two positions with the result that the repeater relay automatically compensates for variations in the operation of the control relay.

In the drawings, Fig. l is a diagram of a section of railway track equipped with coded track circuit apparatus embodying my invention, and

Fig. 2 is a fragmentary view showing an alternative way in which the repeater relay may be employed. 7

Referring to Fig. l'oi the drawings, there is shown therein a section of railway track through which traflic normally moves in the direction indicated by the arrow, that is, from left to right. The track rails I and 2 of'the track section are separated'from the rails of the adjoining sec tions by insulated joints 3. Because of the length of the section it is divided into subsections BT and AT by insulated joints 3. Each of the subsections has a code following track relay TR con nected across the track rails at the entrance end of the subsection and operated by coded energy supplied over the track rails of the subsection from a track battery TB at the exit end of the section. The track relay BTR at the entrance end ofthe subsection B I governs the repeater relayTP which operates through the decoding transformer EDT to govern the relays IE and ID which control the circuits of the lamps of the signal S at the entrance end of the section. The track relay ATE governs the supply of energy fromthe battery BTB to the rails of subsectionlBT.

' .The supply of energy from battery ATB to the rails of subsection AT is governed by a contact of the transmitter relay CTM, and the circult of relay CTM is governed by a contact of a relay 2H which is governed by traiiic conditions in advance so as to be picked up when and only when the section in advance is not occupied. The means for controlling the relay 21-1 is not a part of this invention and this relay may be governed in the same manner as the relay lH. When relay 21-1 is picked up, energy is supplied to relay C'IM over a circuit governed by a contact of code transmitter IBQCT, and when rela 2H is released energy is supplied to relay CTM over a circuit governed by a contact of the code transmitte'rlECT.

The code transmitters IBQCT and lliCT have contacts which are continuously operated between open and closed positions in such manner as tooccupy each of their two positions for substantially equal time intervals. The contacts of code transmitter ESQCT are operated at a rate such as to be closed 180 times a minute, and the contacts of the code transmitter 550T are operated at a rate such as to be closed '75 times a minute.

Each end of the tracl; section is provided with a suitable source of direct current, such as a storage battery, not shown, the positive and negative terminals of which are designated B and C, respectively.

As shown, the relay 2H is picked up and causes relay CTM to be controlled by the code transmitter .E'EECT. During the open periods of the contact of code transmitter EBUCT, the supply of energy to relay CTM is cut off and the contact of relay CTM is released and interrupts the supply of energy from battery ATE to the rails of subsection AT. Accordingly, the contact of track relay ATR is released and interrupts the supply of energy from battery BTB to the rails of subsection BT with the result that the contact of track relay BTR is released.

When the contact of code transmitter lEuCT closes, energy is supplied to relay CTM and its contact closes with the result that energy is supplied from battery ATB over the rails of subsection AT to the winding of track relay ATR and the contact of relay ATR, picks up. When relay ATR picks up, energy is supplied from battery BTB over the rails of subsection BT to the Win-1b ing of relay BTR and the contact of relay BTR. picks up.

When the contact of code transmitter moves to its open position, the relay CTM re leases and interrupts the supply of from the battery ATB and relay ATR releases to interrupt the supply of energy from the battery BTB with the result that relay releases. As long as the section is vacant the relay BTR continues to be operated, as explained above, by energy supplied over the section rails, the rate of operation of the relay contact being termined by the rate of operation of the relay CTM.

The repeater relay 'IP, which governed by the relay BTR, is of the polar stick type and it has contacts which are moved to one position when energy of one polarity is supplied to the relay winding, and are moved to their other position when energyof the other polarit sup plied tothe relay winding, while the relay contacts, when moved to either position, remain in that position until energy of the polarity eifective to move the relay contacts to their other position is supplied to the relay winding.

One terminal of the winding of the relay is connected to the negative terminal C of source of direct current at this location The other terminal of the winding of the TP is connected to one element of the condenser Q, the otherelement of which is connected to the movable contact of the track relay When the movable contact of the track relay BTR, is picked up, it engages a stationary contact which is connected to the positive terminal B of the local source of direct current, and when the track relay movable contact is released it engages a stationary contact which is connected to the negative terminal of the local source of direct current,

Accordingly, when the movable contact of the track relay BTR is in its picked-up position, the condenser Q and the winding of relay T? are connected in series across the terminals of the local source of direct current, and as long as the potential between the elements of the condenser is less than that between the terminals of the local source of direct current energy, energy from the source is supplied to the condenser to increase the charge between the corn denser elements. This energy is supplied in the form of an electric current which flows through the Winding of relay TP from left to right and causes the contacts of relay '1? to move to their left-hand or normal position.

The resistor shown between the terminals of the winding of relay TP is of a relatively high value, and serves merely to prevent arcing at the contacts of relay BTR, Which would otherwise be caused by the inductance of the winding of relay TP.

When the movable contact of the track relay BTR is in its released position, the supply of energy from the local source of energy to the condenser Q is cutoff and the condenser is connected across the terminals of the winding of the relay TP with the result that energy stored in the condenser causes current to flow from the left-hand terminal of the condenser through the winding of relay TP from right to left to the right-hand terminal of the condenser. The direction oi flow of this current through the winding of relay TP is such that it moves the contacts of the relay TP to their right-hand or reverse position.

As long as the track relay BTR responds to coded energy the contacts of the relay T7? are operated to their normal position by energy supplied from the local source of current to the condenser during the picked-up periods of the track relay, and are operated to their reverse position by energy supplied from the condenser during the released periods of the track relay.

As a result of this operation of the contacts of relay TP energy is supplied through the decoding transformer IDT to relay IH and keeps its con- 4 tacts picked up, as explained in Letters Patent of the United States No. 2,237,788, issued April 8, 1941, to Frank H. Nicholson et al. In addition, as a result of operation of the relay TP energy is supplied from the transformer IDT through the resonant rectifier unit I80DU to the relay ID. The unit I80DU is arranged and proportioned so as to supply to relay ID energy efiective to pick up the relay contacts when and only when the relay 'I'P is operated substantially at the I80 code rate. As relay TP is being operated at this rate, the relays ID and IH are both picked up and establish the circuit of the green lamp G of signal S.

When a train enters subsection ET, the relay BTR. releases and remains released with the result that the contacts of relay TP move to their right-hand position and remain in that position and energy ceases to be supplied through the transformer IDT to the relays III and ID and they release to interrupt the circuit of the green lamp G and to establish the circuit of the red lamp R of the signal S.

When the train advances into subsection AT,

the relay ATR is caused to remain released and does not cause energy to be supplied from battery ATB so that relay BTR. remains released when subsection ET is vacated.

When the train advances into the adjoining section in advance, the relay 2H releases and causes relay CTM to be operated by the code transmitter 'I5CT with the result that when subsection AT is vacated, the relay ATR is operated by energy of 75 code frequency and supplies energy of this code frequency from battery BTB to the rails of subsection BT so that track relay BTR operates at the 75 code rate. When relay BTR. is operated at the 75 code rate, the relay TP also operates at this rate and energy is supplied through the transformer IDT to pick up relay IH, but not to pick up relay ID. When relay I H picks up, the circuit of the red lamp R is interrupted and energy is supplied over the back contact of relay ID to the yellow lamp Y of signal S. When the train vacates the adjoining section in advance, the relay 2H picks up and transfers control of the relay CTM from the code transmitter 150T to the code transmitter IBOCT with the result that energy of this code frequency is supplied from battery ATB to the rails of subsection AT. Accordingly, the relay ATR operates at the 180 code rate and causes energy of this code frequency to be supplied over the rails of subsection BT so the relays BTR. and TP operate at the 180 code rate and the energy supplied through the transformer IDT keeps relay IH picked up and picks up relay ID to light the green lamp G of signal S.

The relay TP operates in such manner that its contacts occupy each of their two positions for substantially equal periods of time regardless of inequalities in the picked-up and released periods of the contact of relay BTR.

As explained above, when the contact of relay BTB, is picked up, the condenser Q is connected across the terminals of the local source of direct current in series with the winding of relay TP. The condenser Q is of relatively large capacity, such as 4000 mid, and its relationship to the inductance and resistance of relay TP is such that the condenser will not be fully charged during one picked-up period of the contact of relay B'IR and will not be fully discharged during one released period of the contact of relay BTR. In fact, with a condenser of such high capacity, it is found that the charge, and consequently the potential between the terminals of condenser Q, changes very little in value during a single pickedup or a single released period Of the contact of relay BTR.

When the movable contact of relay BTR is picked up, it can then be seen that a potential is applied across the winding of repeater relay TP, and that this potential is equal to the potential between the terminals of the source, minus the potential between the elements of the condenser. When the contact of relay BTR is released, a potential is applied across the winding of relay TP and is equal to the potential between the terminals of the condenser.

It is well known that when an electric potential is applied to a circuit containing inductance and resistance, the electric current does not reach its full value instantaneously, but increases logarithmically, at a rate which is determined by the potential applied. Relay TP is so designed and adjusted that the value of current required to operate it in one direction is the same as that required to operate it in the other direction. Because of the time required for the logarithmic rise of current in the winding of relay TP, when the contact of relay BTR moves to its picked-up or its released position, there is a delay period before the contacts in relay TP operate. This delay period will be the same in each direction of operation when, and only when, the potential applied across the windin of relay TP is the same in each direction.

It will be seen that with the movable contact of rela BTR picked up, condenser Q is charged through a circuit having given values of inductance and resistance, while with the movable contact released the condenser will discharge through a circuit having the same values of inductance and resistance. In such a circuit, and with a condenser Q having a relatively high capacity, when the movable contact is operating so that it occupies its picked-up and its released positions for substantially equal time intervals the rates of charge and discharge of the condenser will be the same, and th potential between the elements of the condenser will remain at a value substantially equal to one-half the potential of the source.

When the relay BTR is operating so that its movable contact occupies its picked-up and its released positions for substantially equal time intervals, with the contact of rela BTR picked up, a net potential equal to approximately one-half the potential of the source will be applied across the winding of relay TP, while with the contact of relay BTR released, the condenser potential equal to approximately one-half the potential of the source will also be applied to the winding of 76 relay TP, Since these potentials are equal the contacts of. relay T? will operate with equal delay periods in each direction, and will occupy their normal and reverse positions for substantially equal time intervals corresponding with the substantially equal time intervals of the movable contact of rel y B R- Ifoperating conditions are such that the movable contact of relay BTR remains in its released position longer than it remains in its picked-up position, then the charge in thecondenser becomes lower, and the potential between its elements stabilizes at some value less than one-half the potential of the source. This lowering of the condenser charge is due to the fact that the conthe condenser is abnormally low, the net potential across the winding of relay TP is abnormally high, and its contacts operate with a relatively short delay time. When the movable contact of relay .BTRreleases, the abnormally low potential between the elements of the condenser is applied across the winding of relay TP, and its contacts operate with a relatively long delay time.

The shortened delay time of relay TP upon picking up of the contact of relay BTR, and the lengthened delay time of relay 'I'P upon release of relay BTR, both operate to make the contacts of relay TP occupy their left-hand or normal positions for substantially as long as they occupy their right-hand or reverse positions.

In like manner, if operating conditions are such that the contact of relay BTR remains in its picked-up position substantially longer than it remain in its released position, then the charge in the condenser will stabilize at an abnormally high level for the reason that the condenser is charging for longer periods of time than it is discharging. Since the potential between the elements of the condenser is now abnormally high,

when the movable contact in relay BTR picks up I the net potential across the winding of relay TP is abnormally low, and the contacts of relay '1? will operate with a relatively long delay time.

On the other hand, when the contact of relay BTR. moves to its released position, since the condenser potential applied across the winding of relay TP is now abnormally high, the contacts in relay TP will operate with a delay period shorter than usual. The lengthened delay time of relay 'IP upon picking up of relay BTR and the shortened delay time upon release of relay BTB. both, operate to make the contacts of relay TP occupy their right-hand or reverse positions for periods substantiall as long as they occupy their left-hand or normal positions.

It will be seen, therefore, that the operation of relay TP is such as to automatically correct for variations in the operation of relay BTR so that the contacts of relay TP occupy each of their two positions for substantially equal periods even though the contacts of relay BTR remain picked up or released more than one-half of the time. Furthermore, the operation of relay TP to correct for variations in the operation of relay BTR is governed by the value of the energy in the con- ,8 denser Q and this varies in accordance with the extent of the difference between the length of the picked-up and released periods of relay Accordingly, the amount by which operation of relay ,IP varie from that of relay BTR is automatically regulated by the amount that operation of relay BTR varies from normal. As a result the amount of correction which is introduced into the operation of rela TP is automatically varied in accordance with the amount by which operation of relay BTR varies from normal.

The control of relay TP is such that the relay TP will operate in response to operation of relay BTR by coded energy of either or code r frequency, and so that relay 'IP will correct for unbalanced operation of relay B'I'R at both code speeds.

When relay BTR is operated by energy of 75 code frequency its movable contact occupies its picked-up and released positions for relatively long periods. During the picked-up periods of thecontact of relay BTR energy is supplied to condenser Q, and because of the relatively long period during which the contact of relay BTR, is picked up, the condenser Q will be charged to a relatively high value. During the released periods of the contact of relay B'I'R. energy from the condenser discharges through the winding of relay TP, and because of the relatively long period during which the contact of relay BT55 is released, the energy in the condenser Q falls to a relatively low value.

Accordingly, at this time the energy in the con denser Q fluctuates between relatively wide limits, d on each change in the position of the contact of relay BTR. the effective value of the energy supplied to relay "SP is relatively great and the contacts'of relay'TP move relatively promptly.

When relay BTR. is operated by energy of 180 code frequency, its contact occupies its picked-up and released positions for relatively short periods with the result that the charge in the condenser Q does not build up to a very high value during the picked-up periods of relay BTR and does not decrease to'a very low value during the released periods of relay BTR. Accordingly, at this time the energy in the condenser Q fluctuates between relatively narrow limits and on each change in the position of the relay BTR the effective value of the energy supplied to relay TP is relatively low and the contacts of relay TP move less rapidly than when relay BTR is operated by energy of 75 code fre- \quency. However, the change in the rate of re- "sponse .of relay TP afiects movement of the relay contacts to both positions and'does not interfere with uniform operation of the relay contacts.

As previously explained, if the contact of relay ".Bmxrcmains in either of its two positions substantially longer than it remains in its other posi tion, the charge in the condenser Q is altered so that the relay TP responds less promptly to move.- ment of the contact of relay BTR to the position which it occupies the larger part of the time than it does to movement of the contact of relay BTR to its other position. This is true regardless of whether the relay BTR is operated by energy of 75 or 180 code frequency so the relay TP corrects -,f.or unequal operation of relay BTR at both code speeds.

As explained above, when the contact of relay CTM is closed, energy is supplied from battery ATB over the rails of subsection AT to pick up the contact of relay ATR. When the contact of relay Q M opens. thesupp y of ener y from1bat amt-s4 tr'y ATB'is interrupted and relay ATR releases. Similarly, when relay ATR picks up, energy from battery B'IB picks up the contact of relay BTR, and when relay ATR releases and interrupts the circuit of battery BTB is interrupted and relay BTR releases.

When the contact of relay CTM closes so that energy from battery ATB is supplied to relay ATR, the contact of relay ATR does not pick up instantaneously. Instead there is a slight delay between the instant of closing of the contact of relay CTM and the instant of closing of the front contact of relay ATR. This delay is not constant and is affected by variations in operating conditions such as variations in the voltage of the battery ATB and variations in the resistance of the track ballast. Similarly, the relay ATR will not release instantaneously on opening of the contact of relay CTM, and the time required for relay ATR to release will vary with variations in operating conditions. Because of these factors the periods during which the contact of relay ATR is picked up may not be as long as the periods during which the contact of relay CTM is closed.

In like manner the contact of relay BTR does not pick up and release instantaneously on picking up and releasing of relay ATR, and the periods during which the contact of relay BTR is picked up may be somewhat shorter than the periods during which the contact of relay ATR. is picked up, with the result that the periods during which the contact of relay BTR is picked up are considerably shorter than the periods during which the contact of relay CTM is closed. Hence, even though the contact of relay CTM is operated so that its closed and open periods are substantially equal in length, the picked-up periods of the contact of relay BTR may be considerably shorter than the closed periods of relay CTM.

As shown in the drawings, the track section is divided into two portions and the coded track circuit energy is repeated at one cut-section location. However, it may be necessary to divide the track section into a larger number of portions 50 that the coded track circuit energy must be repeated at more than one cut-section, and where this is done the distortion in the operation of relay BTR is increased.

The reduction in the length of the picked-up periods of relay BTR is caused primarily by the delay in the picking up of relays ATR and BTR on the supply of an impulse of energy over the track. Hence the amount by which the length of the picked-up periods of relay BTR is reduced is substantially the same when the relay is being operated by energy of '75 code frequency as it is where it is being operated by energy of 180 code frequency. However, although the amount by which the picked-up periods of relay BTR are reduced is substantially the same at both code speeds, this amount represents a much larger proportion of the picked-up period of 180 code than it does of a picked-up period of '75 code, and uneven operation of relay BTR. will result in release of relay ID before it results in release of relay IH.

Since the amount by which occupancy of the contact of relay BTR of one of its positions exceeds occupancy of the other of its positions is substantially the same at both code speeds, it follows that the correction which is required, and is provided by relay TP, is substantially the same at both code speeds. The equipment is arranged and proportioned so that the variations in the speed of response of relay TP are such as to cause of relay IH will not 10 the contacts of relay TP to occupy each of their two positions substantially one-half of the time even though the contact of relay BTR occupies one of its positions substantially less than half of the time.

The construction of the decoding transformer IDT and the resonant rectifier unit IBUDU is such that they operate most satisfactorily if the circuits of the two portions of the primary wind ing of the transformer IDT are established for substantially equal periods of time. The relay TP provides means for controlling the supply of energy to the primary winding of the transformer I DT so that the two portions of this Winding are energized for substantially equal periods of time regardless of variations in operation of the relay BTR. Accordingly, the relay TP makes reliable operation of the coded track circuit apparatus possible when conditions are such that the equipment could not be successfully operated if the circuit for supplying energy to transformer IDT is controlled by a contact of relay BTR. Furthermore, the relay TP makes the operation of relay ID possible under any track circuit conditions under which relay lI-I can be operated.

The operation of the means for controlling relay TP is such that after relay BTR has been re-' leased for a period and thereafter resumes code following operation, the relay TP will not follow operation of relay BTR until there have been several movements of the contacts of relay BTR. This prevents improper energization of relay IE or ID if relay BTR is operated by energy supplied during momentary loss of shunt by a train in the track section.

When relay BTR is released, the energy in the condenser Q discharges through the winding of relay TP and during occupancy of section ET the energy in the condenser Q is completely discharged or reduced to a very low level. At this time the contacts of relay TP move to their righthand position and remain in that position. During the first pick-up period of the contact of relay B'IR energy from the local source is supplied through the circuit of the condenser Q and of the winding of relay TP. The effective potential of this energy is relatively high because of the low value of the charge in the condenser and it causes the contacts of relay TP to move to their left-hand or normal position.

On this movement of the contacts of relay TP an impulse of energy is supplied through the decoding transformer IDT to the relay IH, but the equipment is designed so that the contacts pick up in response to a single impulse of energy from transformer I DT so the relay contacts remain released.

On release of the contact of relay BTR the supply of energy to the condenser Q is cut off and the condenser is connected across the terminals of the winding of relay TP and energy from the condenserflowsthroughthe relay winding. However, the energy supplied to condenser Q during one picked-up period of the contact of relay BTR does not charge the condenser to a value high enough to cause relay TP to be operated by energy supplied from the condenser when relay BTR releases. Accordingly, the contacts of relay TP remain in their left-hand position.

On the second movement of the contact of relay BTR to its picked-up position energy is again supplied to the condenser Q and flows through the winding of relay TP in the direction to hold the relay contacts in their left-hand position. As some of the energy supplied to the condenser spaces 11 during the preceding picked-up period ,of the contact of relay BTR' is still present in the condenser, the condenser is charged to a somewhat higher value during the second pickedup period of relay B'IR. than during the first picked-up period. During the second released period of reenergy is again supplied from condenser Q to relay T? but is not of. a value effective to more the relay contacts and they remain in their e t-ha d positions- 7 a LOn continued operation of relay BTR. the equipment operates as described. The condenser Q is charged during the picked-up periods of relay B'IRvand dischargesduring the released periods of relay BTR, the value of the charge in the condenser increasing with each picked-up period of the relay BTR, After several operations of the relay BTR the energy stored in the condenser Q is effective to operate the relay TP and thereafter the contacts of relay TP are operated netween their two positions in response to operation of relay B'IR and energy is supplied through the transformer IDT to pick up relay IH.

'If'while the section is occupied there is a loss of shunt so that relay BTR is operated by energy supplied over the track rails, the loss of shunt will not persist long enough to permit relay BTR to he operated enough times to cause code followrig operation of relaly TIE. Hence, at these times the may TP will not cause energy to be supplied a ue ls ithe tra sform r T w l y n IQ arid they remain released and hold the signal t s o Fig. 2 of the drawings there is shown a dif ferent way in which the repeater relay 'IP may be employed to overcome distortion oi the coded track 'cir'cuit energy. In this modification the relay is governed by the relay ATE and C011? trols the supply of energy from battery B'I'B to the railsof section BT. explained above, the contact of relay TIP. will occupy each of its two pesitions for substantially equal time intervals regardless of variations in the operation of the controlling relay, in this case relay ATR, Ac-

cordingly, the, impulses of energy supplied to the i s of i ti n'm W ot be d e'ed n le t be ause of, reducti n 'm the picked-.111 eri ds of the. contact of relay. ATE, As aresult the cont o relay 3TB will be pic ed up n ar y one: half of the' time and can directly control the s pp y of n r o cod ng m an e ih esh I have he ein i ust ate nd (16-. scribed only one. term oi coded signaling appae -i s. em ody my in n n t. is u de s od a n me o s cha e d od s may b madetherein within the. scope or the appended claims without departing iilrlom the spirit and scope of myinvention. 7

Having thus described my invention, what I 1 In combination a code following. relay having a ta t wh ehs o r d be wee a, r t and a second position in such manner that at times. said contactoccupies one oi its two positions substantially longer than it occupies the he of t J WQw it Pns a. P a ck r e relay having a contact which is moved to a first or a; second position according as energy of a first or a second polarity is supplied to a wind. ing or said relay, means effective on movement of the contact oi said code following relay to each of its positions to, supply, to a winding of said; repeater relay energy of a value which varies in cord n e with he ns h i th er o duri h ch sa d ede fo ow ng r l con act Owned the position-from which it was moved, the energy supplied tothe repeater relay being of one p la on m m n o the code fo owing relay contact to one position and being of the other polarity on movement of the code following relay contact to its other position, and decoding means responsive to movement of said repeater relay contact between its two positions.

2. In combination, a code following relay having a contact which is operated between a first and a second position in such manner that at times said contact occupies one of its positions substantially longer than it occupies the other oi its two positions, a polar stick repeater relay, means efiective on each movement of the contact of said code following relay to its first position for supplying to a winding of said repeater relay energy of normal polarity and of a value which varies in accordance with the period duringwhichsaid code following relay contact occupied itssecond position, means effective on each movement of the contact of said code following relay to its second position for supply? il to a winding of said repeater relay energy of reverse polarity and of a value which varies in accordance with th period during which said code o l w n relay onta t occ pi d its first position, and decoding means responsive to movement of a contact oi said repeater relay.

3, In combination, a code following relay having a contact which is operated between a first and a' second position in such manner that at times said contact occupies one of its positions substantially longer than it occupies the other of itspositions, a polarstickrepeater relay having a contact the rate of response of which varies in accordance wit the efieotive value of the en.-. ergy supplied to the relay, means effective on each movement of the contact of said code following relay to its first position for supplying energy or normal polarity to a winding of said repeater re1ay, means'efiective on each movementof the contact of said code followin relay to its second position for supplying energy of re-. verse polarity to a winding. of said repeater res lay, means ior varying the effective value of the ne gy supp i d. t aid repe t e y n m e ment of the contact, or said code following relay; to each of its positions in accordance with the length of the period during which said code following relay contact, occupied the other of its pos i ns. and d cod mea esponsive to movement of said repeater elay contact between stwo. p i i ns 4. In combination, a code following relay haw ing a, contact which is operated between a first and. a second position, a polar stick repeater relay, means efiecltive on movement'of; said code following relay to its first; position to supply energy, 0t normal polarity to, a winding of said repeater relay, means ei fective on movement of said code following relay to its second position to supply, energy of reverse polarity to a w'mding. of said repeater relay, decoding means re-. sponsive to movement oi a; contact, of said r e--v peater relaybetween its. normal and reverse po-. siti-ons, and means for causing the periods. duringwhichv the contact; of said repeater relay occupies its no im i a and reverse positions to be substantially qual even though the periods dur-c in-g which, the contact. of said code followingre lay occupies one of its. two, positions arev materialiy longer or shorter than the periods during: which it occupiesthev other of its two positions, a saidmeans. comprising means operativecn move-w ment of the contact of said code following relay to each of its two positions for varying the effective value of the energy supplied to said polar stick relay in accordance with the length of the last preceding period during which the contact of said code following relay occupied the other one of its two positions.

5. In combination, a code following relay having a contact which is operated between a first and a second position, a polar stick repeater relay, a condenser, a circuit for connecting said condenser across the terminals of a source of direct current in series with the winding of said repeater relay when said code following relay contact is in its first position, a, circuit for connecting said condenser across the terminals of the winding of said repeater relay when said code following relay contact is in its second position, and decoding means responsive to movement of said repeater relay contact between its two positions.

6. In combination, a code following relay having a movable contact movable between a first position in which it engages a stationary contact which is connected to one terminal of a source of direct current and a second position in which it engages a stationary contact which is connected to the other terminal of said source of direct current, said relay movable contact being connected to a terminal of said source of direct current in series with a condenser and the winding of a polar stick relay, and decoding means responsive to movement of a contact of said polar stick relay between its two positions.

7. In a coded track circuit signaling system, in combination, a section of railway track, a code following track relay connected across the track rails at one end of said section and having a movable contact operated between a first and a second position by energy supplied over the rails of said section, said track relay movable contact when in its first position engaging a first stationary contact which is connected to one terminal of a source of direct current and when in its second position engaging a second stationary contact which is connected to the other terminal of said source, said track relay movable contact being connected to a terminal of said source in series wih a condenser and the winding of a polar stick relay, and traflic governing means responsive to movement of a contact of said polar stick relay between its two positions.

8. In combination. a code following relay having a movable contact movable between a first and a second position, a condenser, a polar stick relay, said code following relay movable contact being effective when in its first position to establish a circuit for connecting the winding of said polar stick relay across the terminals of a source of direct current in series with said condenser in such manner that energy of one polarity flows through the winding of said polar stick relay during charging of said condenser, said code following relay contact being effective when in its second position to establish a circuit for connecting the winding of said polar stick relay across the terminals of said condenser in such manner that energy of the opposite polarity flows through the winding of said polar stick relay during discharge of said condenser, said condenser and the associated elements being arranged and proportioned so that while said code following relay is responding to coded energy the condenser is not fully charged during one period in which the code following relay contact is in its first position and is not fully discharged during one period in which the code following relay contact is in its second position, whereby on movement of the contact of said code following relay to each of its positions the effective value of the energy supplied to the winding of said polar stick relay varies in accordance with the length of the period during which said contact occupied the other one of its positions, said polar stick relay and the associated elements being proportioned so that the rate of response of the relay contact varies in accordance with the effective value of the energy supplied to the relay winding, and means responsive to operation of a contact of said polar stick relay between its two positions.

ANDREW HUFNAGEL.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,229,254 Nicholson Jan. 21, 1941 2,354,024 Jerome July 18, 1944

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