Electrical signaling system

July 29, 1947.

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P. L. C. CORNU

ELECTRICAL SIGNALING SYSTEM

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Filed March 1, 1943

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Patented July 29, 1947

2,424,554

UNITED STATES PATENT OFFICE

2,424,534

ELECTRICAL SIGNALING SYSTEM

Pierre Lucien Charles Cornu, Paris, France, assignor to International Standard Electric Corporation, New York, N. Y., a corporation of Delaware

Application March 1,1943, Serial No. 477,648

In France August 23, 1939

Claims. (Cl. 177—311)

2

The present invention is concerned with im- control station and the controlled station, such provements in control, signaling and/or similar systems, the purpose of which is to eliminate for all practical purposes any possibility Of a wrong control or wrong signaling while obtain- 5 ing immediate signaling of trouble likely to affect the operation of the system.

One of the objects of this invention is to provide a system in which the energy required for the transmission of control or signaling is trans- 1® mitted from the controlled station to the control station and retransmitted either transformed or ; not from the control station to the controlled station in order to cause the desired control or signaling. 15

A further feature of this invention is presented in the fact that the energy required for the transmission of control or signaling is transmitted from the controlled station to the control station in the form of alternating current, transformed 20 into continuous current at the control station and returned in this form to the controlled station in order to cause the desired control or signaling.

A still further feature of the invention is pre- 25 sented in the fact that the alternating current energy is transmitted from the Controlled station to the control station over two conductors of a line linking the two stations, transformed into continuous current at the control station, ³® and sent back to the controlled station over the two line conductors in order to effect the desired control or signaling.

A still further advantage of the invention resides in the fact that the energy transmitted 35 from the controlled station to the control station is utilized during the interval between con- g j trolling or signaling operations to effect a continuous testing of the installation and signaling any trouble developing and likely to affect its ⁴⁰operation.

Another feature of the invention resides in the &lt; fact that the polarity of the continuous current applied to the line conductors during the interval between controlling operations, to effect the con- ⁴⁵tinuous testing of the line and associated equipment, is reversed at the moment of transmitting the control or the signaling current.

Still another feature of the invention is found in the arrangement in the control or signaling 30 circuit of telephone circuits allowing establishment of telephone communication between the communication being under no circumstances capable of producing interference with the control or signaling functions of the system.

These, as well as other objects and advantages of this invention will be apparent from the following detailed description of one embodiment thereof, which is not given in a limiting sense, but rather by way of example.

This invention resides substantially in the combination, construction, arrangement and relative location of parts, all as will be described in detail below.

In the accompanying drawing the single figure comprises a schematic and diagrammatic illustration of the embodiment thereof selected for the purpose of disclosing the invention.

The control station has been generally indicated by the reference numeral PCM and the controlled station is generally indicated by the reference numeral PCE. The line comprising the conductors Li and L2 extends between the two stations which may be separated any required distance as indicated by the broken line portions of these conductors. The signal and/or control current is supplied from any suitable alternating current source by the fused line Zi, to the primary of the transformer Tl. The secondary of this transformer is connected as shown through proper protection devices such as fuses to the controlled station end of the line conductors Lf, L2. These conductors extend to the control station and are connected to the primary of a transformer T2. The secondary of this transformer has its terminals connected across the input terminal of a suitable rectifier Re. As those skilled in the art will appreciate, the rectifier may be of several acceptable forms, and may include as illustrated a plurality of rectifying devices connected in a bridge circuit as shown. A circuit for the signal lamps Lai and La2 is arranged as shown in conjunction with the switches 12, 15, 22 and 31, as will be later described.

The positive terminal of the rectifier Re is connected by a line to the movable contact of switch which is also connected by a wife to one terminal of the magnet i. The other terminal of this magnet is connected to one of the contacts of a. switch Cm. The other terminal of this switch is connected to the negative terminal of the rectifier and to the movable contact of switch

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11. The signal or alarm circuit comprising the conductors Al and A2 includes the series switch 14 and the shunt switches 21 and 32. The back contact of switch 13 is connected to the magnet 2 which is grounded as shown. The back contact of switch 11 is connected to the magnet 3, which in turn is connected to the mid-point of the primary of the transformer T2. This point is also connected through a condenser Co2 ;to the secondary of a transformer t-2 ⁵for -coupling the telephone equipment P2 to the line. The other terminal of the secondary of transformer 12 is grounded as shown.

The midpoint of the secondary of transformer Tl is connected to the negative terminal .of ;a rectifier rl whose positive'terminal is connected to the magnet 4, which in turn is grounded at fits other terminal and connected to one contact of the switch cm I. The negative (terminal of ithe rectifier rl is connected to one terminal of a switch 41, the other terminal of which is connected to one terminal of magnet 5, and to the positive terminal of a rectifier rl. This terminal iis .-also.connected .to.the other [terminal of'switch ;cm:i ;and through .a .condenser :as .shown :to ground. The negative (terminal of [rectifier ir2 iis connected (through the (resistance JR -to ground. The (telephone equipment ;P I :is .connected 'to Lthe •transformer tl, the secondary of which .has One terminal grounded .and .the .cither terminal cconmected through. condenser .Col to 'the · midpoint of the secondary-.of transformer TH.

.As .diagrammatically '.illustrated 'in the .drawsings, the .contacts or (switches controlled (by the .various .magnets are shown sin .vertical (alignment therewith. Thus the switches 15, 4-2, 14, 43 jand 41 are .operated by the -.magnet ;f. .-Switches 22 and :,2:1 are.operated:by the (magnet >2. [Switches i3:l .and 32:are.OPeratediby:the magnet 3. -Switch 41 .is .operated :by :the .magnet 4. ,-Switch :51 :.is •operated :by magnet 5 .and .controls .the equip-ment -CM .or .a signal associated, therewith. -.The diagrammatic illustration of the .equipment CM is (provided .to indicate that either the -control thereof ,or .a signal in: connection .therewith is really (independent of the (nature of the (equipment, .as (Will (be obvious -to .one skilled in the (.art. The various magnets (and switches controlled thereby are represented .by well known electromagnet relays, of which many practical .forms are available.

The .operation Of this .system .will mow ’be described. When the system iis .in use the.mitermating current source connected to the conductors II and H is .supplying current to the (network. This current is applied to (the (transmission line (LI and L2 through the transformer Tl and (from the line through the transformer T2, across the input terminals of the (rectifier Re. This condition exists throughout normal-operation of the system. As a result .of this a -circuit will be completed to the relay magnets 2 and -4 as follows: from ground through magnet 2, the movable finger of switch 13 and the back contact -normally-engaging 'it to 'the (positive terminal of rectifier Re, from the negative terminal of this rectifier .through the movable contact of switch .11 and its back contact, magnet 3, midpoint of the primary of transformer T2 over the conductors Li and L2 in parallel to the midpoint of the secondary of transformer Tl and from there to and through the rectifier ri, and the winding of magnet 4 to ground. The magnets 2 and 4 in this circuit are energized while the magnet 3 remains de-energized owing to the relative resistance between it and the relays 2 and 4 and the number of ampere turns on these magnets respectively. Thus switches 31 and 32 remain in the position shown, but switch 41 is opened, switches 15 and 12 are opened, switch 14 is closed, switch 13 is on its back contact, and switch 11 is on its back contact. One of the results of this circuit alignment is as will be seen that signal (lamp Τι>α I Us (connected ..across the secondary of ‘transformer T2 -through-switches 31 and'22 and is therefore energized. So long as this light remains energized the operator at the control station is.signaled.that the circuit is in good operating condition.

?If -it be assumed that an open circuit on the iline comprisingthe conductors LI and L2 occurs, •it’follows that the circuit for magnet 2 is opened, with the result -that switch 22 first opens and ,-switch 21 which was open closes. Signal lamp Lal .is extinguished, indicating trouble on the line. The closing of switch 21 completes the ailarm -circuit Al—A2 setting a suitable alarm, not shown, in operation, further signaling to the operator that:spm.ething4s wrong with the line.

:In-the '.event .that «the. .ground connection at (either station or ’both of them .developed a very .high resistant-.condition &lt;the same result, namely .the extinguishing of .light Lal and -the (.energization,of .the alarm will -follow, indicating that the system is not .operating (properly.

Should eitheror bothofthe line eonductorsiLI or L2,become,grounded, magnet'4 becomes shortoircuitedin ran obvious manner, with the result that magnet 3 is .energized to operate -switches 31 and 32. The operation of switch 31 opens -the [circuit .for Jamp Lal;·:extinguishing -it. The operation pf switch.32 will complete the alarm circuit Al—A2 giving a further signal of .trouble on .the line.

.-In’the event that ..energy either rceases 4o be (transmitted from the -controlled station PCE to .the .control station -PCM, or ceases for any reason-io .be .received at PCM, .the supply-of energy for the relay .2 will be cut off so that as-before, .lainp >Lal wilhbeextinguishedand the-alarm circuit will .be completed. Thus ft will be seen that so long as the signal by supervisory lamp -Lal .is energized the circuit 4s (in operating condition, .-but.assoon;asfit is_;extinguished -from .-any one ·of the .several (possible reasons explained above, trouble on the line will be -indicated.

In order to cause transmission &lt;of a control signal to ithe controlled statipn the switch Cm ds closed, completing a circuit for the magnet I Which is .held as long .as (this switch is closed. This circuit is obvious from the (drawing. The energization of magnet -I closes switches 45 and 42, opens switch 44, shifts (the .positive side of the rectifierRe:to .the-front contact of switch 13, and shifts the negative, connection of the rectifier to the (front contact of switch :11. The closing of switches 12 -and if 5 during this period -.maintains the .circuit for the supervisory lamp Lai. The opening of switch 14 breaks the signal alarm circuit during'this period. ’The operation· Of switches 4'1 rind-Ί 3 connects'the rectifier Re in circuit With them -and ground, as will be readily seen from the -drawings. At this time -magnet '4 is not effectively -energized -ana switch 4'1 is closed. The shifting of «witch 13 breaks the circuit for magnet 2 so that -switch 22 opens and switch 21 closes. The circuit -for magnet 3 upon ’the closing of switch '41 ‘is completed through switch 41, magnet &lt;5,. rectifier-r2 and resistance R to ground. Magnet '5 remains -energized but -magnet -3 does

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not remain energized owing to the high value of resistance R in series with the resistance of magnet 5.

The energization of magnet 5 closes switch 5I, causing the equipment CM to undergo the desired control, or causing the operation of the signal device associated therewith. When the signaling operation has been effectively completed switch cml is closed by the operation of the control or signal apparatus, so that rectifier r2 and resistance R are short-circuited. As a result the current for the magnet 3 is strong enough to energize the magnet so as to close switch 32 and operate switch 31. The closing of switch 32 does not complete the alarm circuit because switch 14 is open. However, the operation of switch 31 causes the signal lamp La2 to be energized through closed switch 15, the front contact of switch 31, and closed switch 12, indicating at the control station that the control signal’has been properly ^transmitted and the desired control or signaling at the controlled station has been effected. Upon the opening of switch Cm at the completion of this operation, the control circuit is broken and the parts returned to the normal position shown in the drawings, at which time, of course, the alarm circuit is open at switch 21 and the supervisory lamp Lal is operated.

Telephone communication can be effected over the circuit from either station PI and P2. The secondary of transformer t2 is grounded at one terminal and its other terminal is connected through the capacitor Co2 to the primary of transformer T2, over the line conductors LI—L2 in parallel to the midpoint of the secondary of transformer Tl, and thence through the capacitor Col and the secondary of transformer tl to ground. Thus the telephone circuit is ready for operation at all times without interference with the other functions of the circuits.

From the above description it will be seen that the subject matter of this invention can be applied in various physical forms without departure from the novelty thereof. For example, those skilled in the art will appreciate that capacitive coupling devices could be employed in place of the transformers without affecting the basic operation of the system. I do not, therefore, desire to be strictly limited to the disclosure as given herein for illustrative purposes, but rather by the scope of the appended claims.