US949881A

US949881A - Alarm and current-saving apparatus for automatic exchanges.

Info

Publication number: US949881A
Application number: US41449808A
Authority: US
Inventors: Albert M Bullard
Original assignee: Western Electric Co Inc
Current assignee: AT&T Corp
Priority date: 1908-02-06
Filing date: 1908-02-06
Publication date: 1910-02-22
Anticipated expiration: 1927-02-22

Description

A. M. BULLARD.

ALARM AND CURRENT SAVING APPARATUS FOR AUTOMATIC EXCHANGES.

APPLICATION FILED FEB.6, 1908.

Patented Feb. 22, 1910.

. corrected.

UNTTED @TATEtd r orricn.

ALBERT M. BULLARD, OF NEW YORK, N. Y., ASSIGNOB. TO VIESTERN ELEG'IRIG COMPANY, OF CHICAGO, ILLINOIS, A COR-PGRATION OF ILLINOIS.

ALARIVI AND CURRENT-SAVING APPARATUS FOR, AUTOBIATIG EXCHANGES.

oiasei.

Application filed February 6, 1908.

Specification of Letters Patent.

Patented Feb. 22, 1910.

Serial No. 414,498.

To all whom it may concern:

Be it known that I, ALBERT M. BULLARD, citizen of the United States, residing at New York, in the county of New York and State of New York, have invented a certain new and useful Improvement in Alarm and Current-Saving Apparatus for Automatic Exchanges, of which the following is a full, clear, concise, and exact description.

My invention relates to automatic telephone exchange systems, and its object is to provide improved means for calling attention to an abnormal condition, such as an accidental ground connection which may exist on any line of the exchange, and to prevent the waste of current which would otherwise result from the existence of such ground connection.

i he invention is applicable more especially to automatic exchanges such as that described in Patent No. 826,310 granted to me July 17th, 1906, having so few lines that it would not be economical to keep a repair man at the place or town where the system is installed. It is possible to so design a system of this description that the apparatus and the central battery will seldom need pcrsonal attention. The lines, however, particularly when they are of overhead construction, are liable to become grounded in various ways, and if the battery side of a line becomes grounded, a very appreciable portion of the energy of the battery may be wasted before the trouble is discovered and The loss of current is considerably greater in an automatic exchange than it is in a manual exchange because the selecting mechanisms in the local circuits of the line relays require a comparatively heavy current for their operatiom-much greater than that which would flow in any line circuit. however short.

in accordance with the present invention, I provide in the local circuit of the line relay of each line a protective device which in response to an abnormal flow of current will cause the supply of current to both the line circuit and local circuit of the affected line to be cut off, thus stopping the waste of cur rent, and will also cause a signal to be given at some point where there are persons in attendance, as at a neighboring manual exchange, so that the difficulty may be discovered and corrected without delay. I also preferably provide means whereby, if the trunk line leading to the manual exchange is busy at the time the trouble occurs, the signal will be postponed or stored up, so to speak, and made manifest only when the trunk line becomes free.

I will describe my invention more particularly by reference to the accompanying drawing, which is a diagram illustrating the circuits and apparatus of one of the lines of an automatic telephone exchange including a trunk line extending from such automatic exchange to a distant manual exchange; an operators cord circuit at the manual exchange being also shown.

The circuits and apparatus of the automatic exchange system shown in the drawings are in general the same as those shown in Figure 1 of my prior patent above referred to with the addition of certain apparatus and circuits hereinafter described, for the purpose of accomplishing the results above outlined. The same reference characters and letters which are used in Fig. 1 of my said prior patent are also applied to corresponding parts in the drawing of the present application, and the general characteristics and mode of operation of the automatic exchange will be apparent by refer ence to that patent. In the system shown, the selecting mechanism associated with each line of the automatic exchange is operated by stopping and holding magnets which are connected in a local circuit 5, 6, 8 con trolled by the line relay 0. In the selecting operation this local circuit is intended to be opened and closed very rapidly and not to remain continuously closed for any considerable period of time. It is true that the local circuit for the holding magnet is kept closed during conversation after the selecting operation has been completed, but at that time the high resistance relay 7c is included in the local circuit so that an excessive flow of current does not then occur. Normally, however, the relay 7c is short-circuited by the branch 8 controlled at the back contact of the line relay a. It is evident that in the system shown if an accidental ground connection should exist on the battery side 2 of the subscribers line, as at the point marked 50, the line relay 0 would be continuously excited and there would be an opportunity for serious waste of current in the local circuit 5, 6, 8 except for the provision hereinafter to be described.

In applying the present invention to the system shown, a device is provided in the local circuit 5, 6, 8 of each line, adapted to respond to a continuous flow of current such as would result if the line relay 0 should remain continuously excited; and this device in its response is adapted to bring about the opening of the circuit or circuits in which the current is wastefully flowing, and will also bring about the giving of the alarm signal. The responsive device may be of any suitable kind, but as the time of application of current should be a necessary factor in its operation, in order that it may not respond to the ordinary intermittent selecting impulses, I prefer to use a heat coil of the ordinary type. Such a device comprises a coil of wire wound upon a spool in which a pin 53 is held under tension by easilyfusible solder. The pin normally holds a spring 52 away from a contact anvil or plate 27, but when released permits these parts to come together and close an electric circuit. As shown, the circuit 29'is adapted to be closed by the contact device of the heat-coil 26. This circuit includes a low-resistance winding of a relay 30, and a fuse 25 is also provided in this circuit which is adapted to be blown when the circuit is closed through said low resistance relay winding; the blowing of the fuse serving to disconnect the central battery from the line and local circuits of the affected line. The current will flow long enough however to cause relay to attract its armature, which controls locking circuit including a high resistance winding 31 for said relay. This locking circuit has two branches, one through a back contact of a signal-controlling relay and through a resistance 33 to earth, and the other through the winding of said relay 3? through conductor 34:, back contact of relay 70 wire 86, and back contact 3'? of line relay 0 of the trunk line to earth. The relays which are directly associated with the trunk line are the ordinary relays such as are provided for each line of the automatic exchange, the only special relays required for the present invention being relays I50 and 32, which are not individual to any line but serve for the whole exchange.

The alarm signal to be given upon the response of relay 32 is preferably the mere display of the line signal associated with the trunk line at the manual exchange coupled with the application of the ordinary busylouzz current to the trunk line, to warn the operator of the trouble when she makes con nection with the trunk line in answer to the signal. It is evident however that the alarm or signal to be given in response to the operation of the protecting device 26 of any line may be of any desired character, whether visual or audible, or both, and at any desired place.

Relay 32 is adapted when excited to apply ringing current from the grounded generator it through lamp 39 and contact -10 to the line wire ll of the trunk line from which the annunciator drop or line signal are is normally connected in a branch to ground from the springjack at the manual exchange. Relay 32 is also arranged to close a contact 44 governing a circuit 45 through the wind ing 25* of the busy-test and lockout relay t associated with the trunk line. This lockout relay when excited closes a contact 46 controlling a locking circuit through its own winding, and also closes a contact 43 which applies busy-buzz current from induction coil 1! to the line wire 42 of the trunk line.

It will be understood that the heat coils or other responsive devices 26 for each line are not the usual heat coils which in practice are included in the line circuit, but are special devices locaed in a local circuit. l lach line may of course be provided with the ordinary protective devices such as lightning arresters, heat coils, or sneakcurrent arresters and fuses, in addition to the special equipment herein disclosed. ll hile several batteries each marked 7) are illustrated in the drawing for the sake of simplicity in showing circuit connections, these batteries in practice may be and preferably are one and the same.

The operation of the alarm and currentsaving equipment is as follows: if the bat tery side 2 of any line becomes grounded, accidentally or otherwise, the relay 0 of such line is immediately excited and closes contact 28. This completes a local circuit from the central battery 7) through the line fuse contact 28 of line relay 0, conductor 5, heat coil 25, normal contact of test relay t, conductor 0, holding magnet (Z and stepping iagnet c of the selector, and thence by conductor 8 through a back contact: of relay Z and back contact of relay (4 to earth. The operating n'iagnets (Z and c of the selector are of low resistance, and the volume of current going through the heat-coil 26 will cause the operation of said h it-coil in about one minute prorided the ground is not removed from the line. lVhcn the heat-coil operates, the spring 52 closes against its front contact plate 2? and thereby con'ipletes a circuit from conductor 5 through conductor 29 and the low 'esistance winding of relay -30 to earth. The closure of this low res stance circuit 5, 29 causes the line fuse 25 to be blown, thereby disconnecting the central battery 6 from the subscribers line and local circuit, thus preventing further waste of current. Relay 00, in drawing up its armature, closes a circuit from battery Z) through the high resistance locking winding 31 of said relay, through a back contact of relay and resistance to earth. The re sistance is introduced to reduce the amount llt) of current flowing in this circuit and also to permit the subsequent operation of relay 32 which, if the resistance 33 were omitted, would be short-cireuited.

Assuming that the trunk line is not in use at the time when the accident occurs, relay 32 will be immediately operated over a circuit in multiple with a resistance 33 which may be traced through the winding of relay 32 to conductor 84, through back contact 35 of relay if of the trunk line, thence over conductor 36 and through the normal contact 37 ot the line relay 0 of the trunk line to earth. Relay 32, in attracting its armature, disconnects the branch containing the resistance 33 and leaves the circuit for relay 3O dependent upon the continuity of the other branch controlled by relays k and 0 as previously traced. Relay 32 also by closing contact 40 applies current from the ringing generator G through the resistance lamp 235) to line wire 41 ot' the trunk line and so to the anmmciator 49 at the distant manual exchange, thus displaying the line signal to the operator. The signal-controlling relay 32 also by closing contact 44 applies current from battery b in a circuit through conductor l?) and winding Z of the test relay to earth. lV hen the operator at the manual exchange answers the signal given by the 'talling ot the annunciator drop, the insertion oi her answering plug closes a metallic circuit over the trunk line which causes the relays and a to be operated. TV hen relay 0' breaks the contact 37 it also makes a contact 18 by which current is applied from the central battery 6 through the fuse 25 of the trunk line, contact 4:8, heat-coil 17, front contact -16 of relay 6 through the winding 5' of said relay to earth. Relay t thereby remains excited. The heat coil 47 associated with the trunk line is not operated at this time because of the high resistance of wind ing 25. The relay 25 by maintaining contact closed applies busy-lnizz current from the induction coil a, over conductor 12 through condenser m to the line wire l2 of the trunk line and thence through the open ators telephone apparatus at the manual exchange and back over line wire 41 and through relay a to earth. Relays 30 and 32 are now released by the opening of contact 3? of the line relay 0', the further excitation of these

relays

30 and 32 being unnecessary. The OtIJQlZttOl upon hearing the busy signal immediately following the display of the line signal of the trunk line will know the nature of the trouble at the automatic ex change and will see that a repair man is sent to investigate and correct the difiiculty. In small exchanges to which this invention is applicable there will be so few lines that it is obviously unnecessary for the number of the line in trouble to be transmitted to the distant operator, as a glance at the battery fuse panel at the automatic exchange will tell which fuse has been blown. hen the operator withdraws her answering plug from the spring jack of the trunk line the relays 0 and a will be released. The relay 0 will in turn release the relay 25. The entire apparatus of the trunk line is now restored to normal condition so that the trunk line will be available for its legitimate use.

If a trunk line is in use when the subscriber's line of the automatic exchange becomes grounded, the notification to the operator at the manual exchange will be deferred until the trunk line is free. During the use of the trunk line the circuit for relay 32 is broken at the contact 37 of line relay 0' of the trunk line, but relay 30 remains excited by current flowing through its winding 31 and through the back contact of relay 32 and resistance to earth. It at the time the trouble occurs the line relay 0 of the trunk line is being rapidly operated to open and close. its contacts, as in the process of selection, the relay 32 will not respond, because it is made slightly sluggish in its operation by the provision of a copper jacket upon its core. As soon as the trunk line is free, however, the relays 0" and 70 are restored to normal condition. whereby the circuit is completed for relay and the notification given to the operator at the manual exchange as before described.

It the trunk line for transmitting the signal to the manual exchange operator should become grounded on its battery side 4-2, the heat coil 47 ot' the trunk line will be oper ated, and will blow the fuse and cause the operation of the relay 30 as before described in connection with an ordinary subscribers line. The line signal will be displayed before the operator and the busy tone will also be heard except in the extremely rare case of a ground connection 01 practically Zero resistance at a short distance from the exchange. Furthermore, the operator will find the trunk line dead because the fuse has been blown. Relay If will be maintained excited by current flowing in its winding 2* until the inspector clears the trouble. Relays and 32 will also remain operated until then.

it will be observed that the heat coil or similar responsive device is placed not in the line circuit but in the local circuit con trolled by the line relay. @ne of the principal advantages of this arrangement is that the current variations between minimum and maximum in the local circuit are relatively small as compared with the current variations in the line circuit. he variations in the local circuit are caused only by variations in the electromotive force of the central battery, which in a well-designed exchange are small. The Variations in the line circuit result not only from variations in the electromotive force of the battery, but also from variations in line resistance, and shunts upon the line due to accidental grounds.

1 claim 1. In a telephone exchai'ige, the con'ibination with a source of current, and a line circuit connected therewith, of switching mechanism responsive to current in said line circuit and adapted for rapid intermittent op eration, a device responsive to a continued flow of current in said line circuit, but not responsive to rapidly-cl'ianging current, and means controlled by said responsive device for cutting cit the supply of current.

2. In a telephone exchange, the combination with a source of current, and a line circuit connected therewith, of a relay in the line, a circuit controlled by said relay, switching mechanism in said circuit adapted for rapid intermittent operation, a device in said circuit responsive to a continued How of current, but not responsive to rapidly-interrupted current, and means con trolled by said responsive device for cutting off the supply of current.

The combination with an automatic telephone exchange having line relays in. the subscribers lines and selecting mechanism in local circuits of said line relays, ot a responsive device in the local circuit of a subscribers line relay, said device being adapted for actuation only by a long-continued flow of current, and a signal controlled by said responsive device.

4t. The combination with an automatic telephone exchange, a manual exchange and a trunk line connecting them. of a protective device 26 associated with a line of the auto matic exchange, and means controlled by said protective device for ap nying current to the trunk line.

The combination -with an automatic telephone exchange, a manual exchange and a trunk line uniting them, of a signal associated with the trunk line at the manual exchange, a protective device associated with a line of the automatic exchange adapted to respond to an abnormal flow of current, and means controlled by said protective device for causing the operation of said signal.

6. The combination with an automatic telephone exchange, a manual exchange and a trunk line uniting them, of a line signal associated with the trunk line at the manual exchange, a protective device associated with a line of the automatic exchange, adapted to respond to an abnormal flow of current, means controlled by said protective device for causing the display of said line signal, and means also controlled by said protective device for applying a tone-producing current to the trunk line.

7. The combination with an automatic telephone exchange, a manual exchange and a trunk line uniting them, of a protective device associated with a line o1 the automatic exchange adapted to respond to an abnormal flow of current, a signal associated with the trunk line, means for operating said signal, and a relay associated with the trunk line arranged to bring said signaloperat-in means under control of said protective device, during the idle condition of said trunk line.

8. The combination with a telephone line t 42, of a signal-controlling device 32, a protective device responsive to an abnormal flow of current, a line relay and means for .exciting the same during the use of said telephone line, a circuit for .ignal controlling device controlled at a back contact of said line relay, and means controlled by said protective device for applying current to said circuit of said signal-controlling device, whereby upon the operation of the protective device the signal is not given until said telephone line is free.

9. The combination with an automatic telephone exchange system, a manual exchange and a trunk line uniting them, of a protective device associated with. a line of the automatic exchange, a signal controlling device 32, a relay 0 excited during the use of the trunk line, a circuit for said signalcontrolling device, controlled at a back contact of said relay 0, and means controlled by said protective device for applying current to said last-mentioned circuit.

10. The combination with an automatic telephone exchange, a manual exchange and a trunk line uniting them, a protective device associated with a line of ti e manual exchange, a relay 32, means controlled thereby for applying signal. current to the trunk line, a line relay for the trunk line excited during the use thereof, a circuit for said relay 32 controlled at a hack contact of said line relay, a relay 30 adapted to apply current to said relay 32 and having a locking winding in a circuit controlled at a back contact of said relay 32, and an energizing circuit for said relay 30 adapted to be closed by said protective device.

11. In a telephone exchange system, the combination with a source of current and a line circuit connected therewith, of switching mechanism responsive to current of one character in said line, a device responsive only to current of another character in said line, and means controlled by said responsive device for cutting off the supply of current.

In witness whereof, I hereunto subscribe my name this 30th day of January A. D., 1908.

ALBERT M. BULLARD.

\Vitnesses J. N. REYNOLDS,

A. P. PINKLER.