US1107154A - Telephone-exchange system. - Google Patents

Description

E. E. CLEMENT. TELEPHONE EXCHANGE SYSTEM. APPLIOATIOH IILED NOV. 23, 1906 RENEWED DEC. 81, 1010.

1,107,154. Patented Augi11,1914.

2 BHEETB-BBEET 1.

' Wilma:

Patented Aug; 11,191L

2 BKEETB SHEET 2.

noanroz ITED STATES PATENT OFFICE.

EIl'iJVARlD E. CLEMENT, OF WASHINGTON, DISTRICT OF COLUMBIA, ASSIGNOR, BY

liftESll'E ASSIGNMENTS, TO FREDERICK C. STEVENS, OF ATTIGA, NEW YORK.

TELEPHONE-EXCHANGE SYSTEM.

Patented Au 11, 1914.

application filed November 23, 1905, Serial No. 288,776. Renewed December 31, 1910. Serial No. 600,278.

during the idle hour.

it is the primary object of my present invention to arrange a system having mam and auxiliary switchboards, or what I may call main and equalizing switchboards, so

that individual overflow calls will be automatically trunked to the auxiliary board, and at a certain time, the chief operator or traliic manager of the exchange may throw into operation all of the automatic devices so that the entire load thereafter will be taken off the main switchboard and put on the auxiliary switchboard.

In carrying out my invention, 1 provide the usual line answering jacks and multiples if so desired, with cord-circuits and their equipment on the main switchboard positions. In addition, I provide one or more automatic answering switches, which i call primary selectors, for each position, these being normally inactive, but capable of being rendered active in any one of three ways. The first way is by means such as a grounding lug individual to each switchboard position, so that any one or more positions can be plugged up to be handled automatically, while other positions continue to "be handled manually. A second way is hyhaving a. controlling relay for each primary selector or group of selectors, connectcd to talre current so that an excess of our rent due to an excessive number of calls will energize said relay to automatically render its prinuu'y selector active. The best form for this I have found to be a solenoid, controlling the selector circuit, and itself con nected in the common return from the line lamps on its position. Such a solenoid can be adjusted with nicety, so that one, two, or more lamps can be permitted to light without working the solenoid; but the rise of current beyond one, two, three or whatever the number of lamps may be, due

to the lighting of additional lamps, that is to additional calls, will effectively energize the solenoid, and so throw the overflow calls onto the primary selector trunk and the auxiliary switchboard. The third way is by having a series of relays, their contacts working in parallel with the grounding plugs or their various positions, each relay controlling the selectors on one position or one section of the switchboard, and all the relays having their magnets in a common circuit leading to and controlled by the chief operator or traffic man, whereby at stated times, such as during the busy hour, or during the idle hour, all the primary selector switches can be thrown in or can be thrown out at will.

The auxiliary switchboard in this system, which takes the overflow calls, may have multiples of all the lines in the exchange, for connective purposes, but I preferably provide it with automatic connector switches containing line multiples, the auxiliary operators having number senders in their cord-circuits, so that they may be relieved of the necessity for testing a line to ascer-. tain if it is busy; for picking out the line and sticking the plug into its individual jack, and from ringing the wanted subscriber. These three demands being eliminated, the auxiliary operators can handle almost twice as many. calls as they would if they had such demands to meet.

My invention is illustrated in the accompanying drawings, wherein- Figure 1 is a diagram of a subscribers station and a portion of the main switchboard, together with a trunk to the auxiliary switchboard. Fig. 2 is a diagram co1nplementary to Fig. 1, showing the circuits of the auxiliary switchboard.

Referring to the drawings, A is one subscribers station, and A is another, both equipped with the ordinary apparatus employed in common battery systems. These two stations are shown connected to a central oflice in which operators connective circuits 0 are provided, each of these comprising the answering and calling plugs P, P, a listening and ringing key not shown, answering and calling supervisory lamps s,

8 and controlling relays therefor, S

r and S"S Each cord-circuit is separated tery B is bridged across end three insulated springs 79", 72

by a pair of condensers C, and the main batthe two ends as usual between the pairs of relays, the two branches of the battery circuit being 1, 2, 3 and 1, 41, 5. Further description of the ordinary cord-circuits is not thought to be neces Each line is equipped at the central ofiice with a line-relay M, a lamp signal'm, jacks J and a cut-cit relay N. These are all of a type and are arranged in a manner well understood by those skilled in the art. The

line G7 is normally connected to the linerelay M and ground, the relay being connected on its other side to the battery wire 1, connected to the live side of battery B. When the cut-off relay N is energized the line is connected to the extensions 8-9 leading to the jacks, and simultaneously to the extensions 8090 leading to individual contacts 79, p in an automatic primary selector switch P The peculiarity of the two-wire multiple circuit I have shown is that the cut-off relay N is in every case energized over one side of the talking circuit, or that portion thereof'leading to the connection terminals and normally disconnected from the line. Hence this cut-off relay may derive current either from a cord- I circuit or from the battery connections through the circuit of the primary selector P The function of this primary selector is to pick out and make connection with a calling line, plugging the same onto a trunk -11 leading to a jack J on an auxiliary or equalizing section of the central ofi'ice switchboard, thereby doing automatically what the operator does manually, when she trunks a call. The switch P is auxiliary to the operator O, and is intended to pick up calls that the operator cannot handle and trunk them onto a' switchboard where they can be handled. It comprises a spindle 79 which may either be constantly rotating or intermittently rotated as required. The latter condition is preferable because of the economy in power. The spindle carries an electromagnct shell p having on its upper head a tube 7? in which a plug 72 is fitted to slide, and as the spindle turns, the shell, tube and plug all turn with it, being engaged together by the armature p, which is carried on the shell and which has a stud 7/ taking into'a notch in the collar fixed en the spindle 79 when the armature is retracted. The armature has an upwardly extending lever 79 which carries at its lower 79, and at its upper end extends through a slot in the underside of a tube 71 to engage the plug 79", whereby as the armature is attracted upwardly by the magnet the plug will be shot out radially from the spindle. The armature 1) has a central perforation through which the spindle passes, and the magnet structure is supported on the spindle by means of a split collar 39", which takes into an annular groove in the spindle and turns freely therein. Around the spindle is a continuous ring of what I may denominate line answering jacks J Each of these comprises a pair of line springs 11, p, a local test or call contact 72 and a pair of trunk springs 72 -7). In addition to these, I provide a pair of continuous contact rings p", p, which extend entirely around the circle of jacks, afiording constant connection through the springs p, p with windings of magnet p. This magnet 79'' has two windings, one connected at one end to the spring 1) and at the other end to the spring 72 through the wires 12 and 13, respectively; and the other winding connected from thespring 29 on one side to the shell of the magnet and thence to the spindle, which is grounded as shown, on the other side. These two windings are indicated diagrammatically in dotted lines, in Fig. 1. The first, which I have marked 14: in the figure, is the energizing winding which responds to the call of a subscriber and stops the switch, shooting the plug p into his line-jack J 2 when the spring 79 rests on his contact The other winding 15 is what I shall call the holding or controlling winding, being connected back through the wire 16 to the spring 79 through the ring 71 to the wire 17, which is carried along with the trunk wires 10, 11 and terminates on the front contacts of the relays S" and S.

The relays S and S are bridged across the trunk 1011 just as the relays S, S are bridged across the operators circuit, with the main battery B between them, the circuit being: B, 1, 18, 19, S 20, 10, and from the other side: 11, 21, 22, 23, and ground. The wires 18 and 19, and the wires 22 and 23 are normally joined through the back contacts of the relay S, this relay itself beng included in a wire 24 leading to the sleeve contact of the trunk jack J on the auxiliar" swirhboard. The two springs of this jack constitute terminals of the trunk wires 10, 11, and the jack has associated with it a signal lamp m connected on one side to ground and on the other through wire 25 to front contact of relay S Thus, it will be observed the locking circuit of the switch P is controlled by either or both of the coils S", S, while the lamp circuit 25 is controlled by the relay S and this in turn by the relay S.

The most essential feature of the invention is now reached. This is the control of the energizing coil 14 in the primary selector P so that normally it will be inactive and irresponsive to line calls, but it may be rendered active and responsive when occasion demands. This coil terminates at one end, as I have said, on the spring p, which is being carried constantly around over the line contacts 7), so that if a line is calling and its relay M by pulling up has raised the potential of the contact p, current may be taken through the wire 27, contact 2, and spring 7)", by the coil 14, provided that the coil has a ground on the other side. This is the point. The other side of the coil terminates on the spring 7), and this is constantly in contact with the ring 39 which I may term the ground ring. If this ring is grounded the coil 14 will be energized to plug in on the jack J of a calling line. Otherwise not. There are three ways in which this rin may be grounded, which I have illustrated in Fig. 1. The first of these is by ground plug X, which has a metal head adapted to be inserted in a jack to bridge the contacts thereof and so put ground on the wire 28. The second way is by means of a ielay or ground switch X, whose circuit 29 is controlled by a key K adapted to be manipulated by the chief operator or traflic manager. I have shown three of these relays, controlling respectively ground branches 30, 31 and 32 supposed to lead toprimary selectors P at the same or at different positions. The idea is that the trafi'ic man may render one or all of these switches permanently active by closing the switch K. If selection is to be had, that is if some selectors are to be thrown in and others not, then I may provide a regular set of ground wires 30, 31, 32, etc.,'leading to strips on a simple switchboard which can be plugged up to ground by the traflic manager in any desired order or combination. I do not limit myself either to the relays X or the equivalent switch device, however, as any switching means may be'employed which will give the proper control over the grounding of the several selector wires 28 and their ground rings 3).

The third way in which the ring may be grounded is by means of the relay X automatically controlled, and set to respond when the work on its position reaches a certain predetermined point. I have shown this relay as a solenoid with its winding connected in the common return .33 from the line-lamps m, m, m on the position to which the selector P is appropriated and connected. This solenoid has a core 0: which is normally down, and which will not pull up without a certain definite amount of current, this being determinable by the winding of the solenoid and the weight applied on the core. It may be assumed that the simultaneous lighting of three lamps will not pass sufficient current to effectively energize the solenoid, but if an additional lamp lights, the extra current which thus passes will cause the solenoid to pull up its core, closing the branch 34 on .the ground wire 35, and thus putting ground on the rin 1) through the wire 28.

uppose that We have ten pairs of cords and plugs O, and three primary selector switches P assigned to each position, then the solenoid X would control the ground wire 28 for the three selectors, P of its position, and would render the active by grounding their rings 79 whenever there are more than three lamps burning on the position at once, a condition due it is to be supposed to the overloading of the operator. The additional calls will thus be picked up by the primary selectors and automatically trunked to the auxiliary switchboard, whereby lamps we will light for line signals, and these overflow calls will be handled by the auxiliary operators in the ordinary way.

The idea of providing individual grounding plugs X, is to permit individual positions to be vacated by their operators and plugged up to the automatic selectors. When the load drops somewhat, it is thus possible to take off a portion of the operators, to plug up the selector switches at their positions, and thus to divide the work between the main and auxiliary boards. As I have stated, all these ground plugs X may be grouped under the control of the trafi ic manager or chief operator.

The idea of providing the relays X or their equivalent switches is to enable all of the primary selectors in the central oiiice to be rendered active at once, which will occur when the entire load or a large proportion thereof is to be handled on the auxiliary board. I

The solenoid X need not be included in the direct path of the current from the lamps m, m, m, etc'., but may be shunted by such a resistance as will permit a suitable portion of the current to pass the solenoid, and yet will maintain an independent path to ground for the lamps, in case of any accident to the winding.

Before I take up Fig. 2 for description, I will first briefly point out the essential mechanical {features of the typical automatic connector switch. The use of this switch with the system shown in Fig. 1 is not at all obligatory. In fact, so far as the main essential features of the present invention-go, they are all shown in Fig. 1.

That is to say, the jacks J may be located on the auxiliary switchboard as answering jacks in the usual manner, with their line lamps m closely associated with them, and above them may be placed multiple panels containing multiple jacks of all the lines in the exchange. With such an arrangement the auxiliary board would be similar in its appearance and operatlon to every other sectlon of the mam exchange switchboard.

The only difference-would be that whereas upon any given position at an ordinary section of the main switchboard, the subscribers operator could identify the jacks J as belonging to individual subscribers, upon the auxiliary positions the pperators could identify the jacks J only as associated with individual positions of the main board, for obviously any subscribers line rangement upon both the main and auxiliary switchboard sections would be that any operators could be assigned to any positions of either board without varying their work and without the necessity of teaching them any new methods of operating. However, in the present case as in the companion application, filed November 21, 1905, Serial No. 288,369, I include semi-automatic features, shown in Fig. 2, in order to expedite the work of the, auxiliary operators,

and to simplify theparts exposed to wear on the auxiliary board, which will have to be renewed much more frequently than any other part of the switchboard equipment, since according to my invention it remains in service continuously, and for a great part of the time is worked to its maximum limit. I consider it one of the most valuable features of my invention thus to concentrate depreciation and wear upon a definite unit of switchboard which can be rebuilt without changing the main switchboard.

The automatic connector switch F which is illustrated diagrammatically in Fig. 2 is of the general type described in the patent to Keith and Erickson 815,176, of March 13, 1906. It comprises a spindle f bearing wipers f adapted to engage contacts 7. The spindle may be stepped up vertically by means of the vertical magnet f and may also be rotated by means of the rotary magnet f Circuits of the various parts of the switch are regulated by a side switch com prising switch arms f and 7 7' and f.

These arms are all moved together on a common pivot and are setback to zero, that is, in the position shown in Fig. 2,'when the switching mechanism is released, in the manner hereinafter set forth.

Referring now to the diagram in Fig. 2, the arrangement of the switch F will be rstood from the foregoing statement, in connection with the following: The ma ae c 7", f and f are controlled by the relays f and f The side switch magnet f is controlled by the rotary relay f Magnets f and f are merely bridging magnets or choke coils, across the calling end of the switch trunk, included in the connection 30, 31, of the main battery B, through which talking current is supplied to the called subscriber. The vertical and ro tary relays f and f are permanently bridged on the answering end of the switch trunk, which is separated from the calling end by the condensers G. g is the ringing relay, connected to the last contact point of the sideswitch-arm f on one side, and to the battery wire 32 on the other. f, as already stated, is the release magnet, controlled by the relay f which in turn has its circuit closed in either one of two ways, first by both the relays f and f being onergized at once; second, by being connected to the second point of the side switclrarni f by the relay f" and in response to the last rotary impulse for testing the line wanted after it has been selected.

P and P are the answering and calling plugs, respectively, of a pair on the auxiliary board, connected by theconductors 33, 34, 35 and 36, which include the condensers C. The plug P has three contacts, a tip, ring and sleeve, marked 2, p, 19 The tip and ring are connected to the wires 33 and 35, while the sleeve is connected through wire 37 to a cut-off or release relay F, the armature is shown as grounded, and normally resting against the terminals of the wires 38 and 39, which are tapped onto the cord-conductors 34 and 36.

Associated with the calling plug I is a sender, or number transmitter, which I have indicated diagrammatically at with a spindle 0, carrying teeth 0' and 0 coiiperating with springs 0 these springs being connected through wires 40 and 41 with the two cord-conductors 34 and 36, and the spindle being grounded through the wire 42. In operating this form of sender the button 0 is pressed down, and a pin 0 passing into a slot 0 in the tubular upperend of the spindle 0, turns the latter so that the teeth 0 do not touch the springs 0 in going down. In coming back, however, the inner spindle carrying the button 0" is pressed up by a suitable retracting spring not shown,

and its first movement upward turns the sleeve back so that the teeth 0 and 0 turn into contact with the springs o I do not of course limit myself to the use of this special sender. as any suitable type may be employed. The idea is that by pressing down the button a greater or less distance any number of impulses up to ten may be sent by the teetlro contacting with the spring 40, and always at the end of every set of such impulses a single impulse will be sent by the one tooth 0.

In a cord-circuit of Fig. 9., the relays S'" and S correspond precisely to the relays S and S in Fig. 1. They jointly control the supervisory lamp s and this lamp indicates to the auxiliary operator when the calling subscriber has hung up, the control of the connection being given to him. Whenthe plug P is thereupon pulled out from the pol: J, the relay F lets go and grounds both cord-conductors 34 and 36, thereby energizing both relays f and f of the automatic switch F, which energizes the release relay f and the release magnet f, to restore the switch.

With the cord-circuits of .plu s P, P, described, the automatic switch released and restored until the auxiliary operator has actually pulled the plug P. I have shown a second cord-circuit in Fig. 2, however, in which the calling subscriber is enabled to release the switch F himself, by momentarily or permanently hanging up his receiver. This is particularly useful where the calling subscriber desires to make an immediate recall, that is another call for another connection. In such case, with the circuits previously described he would either hang up until the operator had pulled, the plug P, which he would have no means of knowing, or he would announce to theoperator that he desired a recall, by moying his switch-hook up and down to make and break his circuit, and thereby flash the lamp Then the operator, perceiving this lamp to flash, would restore the switch F by pulling the plug P-*, but would immediately go back again to the jack with the same plug, coming in with herlistening key at the same time and asking for the new number wanted. With the second cord-circuit, having the terminal plugs P and P, the op rator need not pull either plug, but in response to the flash of the supervisory lamp she simply comes in on her listenin key 'and gets the new number Wanted. If this number is in the same hundred as the last one called, she leaves the plug 1? in the jack J 4 and picks out the new subscriber by manipulating her button 0 as before. If the new subscriber wanted is in another hundred, she shifts the plug P to ajaek J 4 of that hundred, and then manipulates the button 0 to send the required tens and units digits.

In order to avoid the necessity for pulling the plug P to restore the switch F, I take the return wire 370 from the magnet F, and instead of connecting it directly to the battery, as in the cord-circuit 1, P, I carry it to a front contact of the relay S The re sult is that when the subscriber desiring a recall vibrates his switch-hook, the magnet F will vibrate as therelay S vibrates its armature, and simultaneously with the flashing of the lamp The vibrations of the relay F will put ground on the conductors 38 and 3S) repeatedly, so that the relays f and f will pull up to closethe circuit of the release relay f and thereby actuate will not be the four that are unattended to.

the release magnet f. The automatic switch F being thus restored, obviously the operator need only ask what number is again required. At the same time, it will be observed that the operator also has control of the automatic switch F, so that the called subscriber cannot be indefinitely hung up or locked out through accident or malice on the part of the calling subscriber. If the lamp 8 does not light, but the connection remains up an unreasonable time, the operator pulls the plug P and the switch F is at once released.

The operation of my system will be understood from the foregoing description, but I will briefly trace one connection through its various steps, pointing out the methods of handling the call upon the main and mixiliary switchboards. .lVe will assume that subscriber A desires to talk to subscriber A. He takes down his receiver, his relay M lights the lamp m, and if none of the auxiliary contrivances are in use, the operator 0 in Fig. 1 will answer the call and complete the connection in the ordinary way with plugs P, P. Assuming next that the solenoid relay X is in servlce, as shown in Fig. 1, let us assume also that there are three calls unattended to ahead of A, that is there are three lamps burning, with which his lamp makes four. Current through the three lamps already burning was insuiticient to pull up the solenoid core,'but immediately upon the relay M pulling up to light the lamp m, the additional current in return wire will effectively energize the solenoid, and a circuit is partially completed for the energizing coil 14 of the primary selector P, as follows: ground, 35, 34, 28, p 72, 13, 14, 12, p. The switch spindle, in turning carries the spring p over successive contacts 79 until it comes to one of This may not be the contact of subscriber A, but it 7 will be. some one of the four. Upon touching this, the circuit of energizing coil 14 is completed through thelive contact 7) and wire 27 to the front contact of relay M and to battery wire 1, battery 13 andground. The coil 14 thereuponef'ectively energizes the coil and shell of the magnet 79, pulls up the armature p, and thereby simultaneously uncouples the magnet from the spindle and pushes the plug 72" into the jack J spreading apart the springs 79, 29", causing them to make contact with springs p, 7). I should here state that the springs 29, 72 all around the circle are connected together. Theinstant plug 7f is inserted, the trunk circuit 10 11 is connected to the line conductors 80-90,an(l a circuit for the cut-oil relay N is established as follows: B, 1, 18, 19, C 20, 10, 79 y), 80, 8, N and ground. The relay N then cuts oil the magnet M, which in turn cuts ofl the lamp m and the wire 27 from thebattery, and the contact 29 becomes and puts battery on the wire 17, so as to feedcurrent back to the winding 15 of the selec- W h PT", as follows: B, 1, 18, 26, 260,

16, 15 and armature of S, P P

ground through the frame of the switch.-

The movement of the plug 12 and its asso;

ciated parts are sluggish, due to friction and inertia, hence the very brief interval of time:

which elapses between the cutting off of current from the winding 14 and the cutting on of current through the winding 15 18 m-- suflicient to permit the retractlou of the plug, which remains held in the jack J 2 as" long as current is supplied to the wire 17.- Tlierelay'S being in the path of current through the sleeve side of the trunk, pulls, up, and lights the lamp wa associated Wltll the 'jackJ on the auxiliary"'switchboard,f

through the following circuit:;fl3,'l, 18, 26,;

armature of S 25, m and ground. Thus the instant the plug 10 cuts into the linejack J and the lamp m of the main switchboard isexjtinguished, the call is simultaneously transferred to the lamp 'm, on the auxiliary switch-board. It is perhaps unnecessaryfor me to point out at this stage more than I have already done the use of the relays X or the'plugs X, in grounding the wire 28 when thesolenoid X is either out of service, or not present. I have assumed a condition where -a plurality of line lamps simultaneously burn on the main switchboard, but of co urseit may be desired to render the selector switch P active when no lamps are"burning,or an insuflicient number to energize solenoid X In the night hours for instance, when it' is desired to dispense with the old-fashioned patrol, the switch K may .be' closed and all the selector switches P ln the central oflice thereby rendered active, leaving these ,switches the sole means of picking up and connecting calling subscribers on all parts of the main switchboard. With verylight business a single operator at the" auxihary board will thus have all the 'busine'ss brouglit to her, and that without any perceptible loss of time.

I have statedlth'at there may and preferably will be a plurality of switches P, P for each position. The tubes and springs of these switches'and the' notches which take their studs. 29 are set indifferent annular positions around the spindle "p lVhere three switches are set upon one spindle, they would be 120 degrees apart, and assuming one hundred line-contacts per switch,

each line having its contacts passed? over three times in a revolution of the spindle,

by the three springs p of the three switches,

the longest timethat need-elapse'between thecall and the sticking of the plug p wis.

a very small fraction overone second. It

has beenfound in. practice that switches of this character can be relied upon to test fifty contacts per second, with careful adjustment, and, as the above stated figure would require the testing of only about thirty per second, it is believed to be conservative.

The reason for this quick action is that the first movement of the armature p uncouples the magnet-from the spindle, and as the parts are balanced and the peripheral speed of rotation of the tube p3 is. less than i three inches per.- second, there is so little effective momentum that it is negligible.

In cases where the force is beingreduced on the mainboard, or. where .forany, rea-.

son part of the operators are withdrawn, a

plug or plugsX maybeused to. ground the wire28. The lamp wa indicating acall on-the auxiliary switchboard, ifthat' switchboard be equipped with multiple-contacts, etc., the

operator 0 inserts, tests, connectsand rings off in ,a well-known manner. If,.however, the board 1S equipped as shown 111,

Fig. 2 with semi-automatic apparatus, the operation then proceeds as follows: The

plug P is inserted in thejack J, and current at once flows by the following pathz.

B (Fig. 2), 370, s 35, 10, so, a, cut-oif relay N and ground. It also flows through 370,1 37, 79 J, 24, S and ground. a The I relays F and S are thereupon energized. F HTQIDOVGS the ground from wires 38 and 39. S cuts ofi the relays S and S, andsimultaneously puts battery on the wire 17 to pull up the selector switch I, as follows: B, 1, 18, 17, 7)", 72 16, .15 and ground through the frame of the switch. Up to this point theswitch l? was controlled by the calling subscriber, andif he had hung up, so that relay S had lost current, ,he would have released it, butnow the relay S takes control, and itin. turn held up over the wires 243'7,' whosecontinuity is determined by the operator 0 in Fig. 2. The

operator 0 being thus connected with the calling subscriber, comes in. through her listening key on the cord conductors 33-35 and gets the number wanted,- ,We will assume this to be i l- 68, the number of subscriber A, for instance. The operator inserts the plug P in the jaclrJ of group No. 44, all 'of. which have trunks l3-44; leading to automatic switches F, in which are found multiple terminals f (see Fig. 1) of subscribers lines numbered from 4400 to The operator then pushes down button 0 so that six teeth pass the springs o, and iureturningthese send six impulses its tip side eit 'S, S or S of a cord-circuit. Such a on in place of the vertical magnet-f The operator then sends the final number 8' in the same manner, and the magnet turns the wipers f around to contacts No. 8,

which being in the 6th row belong to line N o. 68, and these being in a No. 44 switch, the whole number of the line is 4468. If the line is busy there will be a ground on er through a magnet f of an automatic switch, or through a relay I round will complete a circuit through t e ti wiper the arm f, the contacts 53, and the re ay f when the last rotary impulse due to the tooth 0 f" is thereby energized. The completion of this circuit will energize magnet f to release and restore the switch. If there be no ground on the tip side of the wanted line, however, this test circuit will not be completed, and the switch wipers will remain on the line contacts. The operator may then ring the wanted subscriber by moving the button 0 up and down indiscriminately, or she may be provided with a key to ground the conductor 34, which is the preferable arrangement. Upon the completion of the conversation, if the cordcircuit P P be used, the lamp 8 lights when the calling subscriber hangs up, and the operator pulls the plugs, always pulling the plug P first. This breaks the continuity of wires 2437 and releases the relays S and F. The former takes battery off wire 17, and as the relay S remains deenergized owing to the subscriber A having hung up, the switch I gets no current, its armature p is retracted to recngage the stud with the notch in its collar, and the switch resumes its round of testing. ()n the other hand the second relay F grounds the wires 38 and 39 simultaneously, which energizes both relays f and f sinn'lltaneously, which closes the circuit of the release relay f which closes the circuit of the release magnet f, and finally this releasesthe switch, which re turns to zero or normal position. If the cord-circuit P P be used, the switch .F is released as soon as the calling subscriber hangs up or flashes his lamp 8. Vith this exception the operation is the same as in the other case.

Having thus described my what I claim and ters Patent is:

1. In a telephone exchange system a main switch board, a plurality of subscribers is sent, and magnet invention, deslre to secure by Letlines connected thereto, operators connective devices on the main board, an auxiliary switch board and trunk connections therefrom with terminal automatic selective answering switches, multiple connections from the subscribers lines to the banks of said switches, and means associated with the subscribers lines to determine the activity or non-activity of said automatic switches, and thereby to determine the answering of the calls on the main or auxiliary board.

2. In a telephone exchange system a main switchboard, an auxiliary switchboard, means for normally receiving and answering calls on the main switchboard, automatic means for receiving and transferring calls by connecting the calling lines to the auxiliary switchboard, and means controlled in the operation of the main switchboard apparatus to determine such transfer of calls to the auxiliary board. M

3. In a telephone system a main switchboard having answering positions and submary selector switch associated with each position and containing terminals of the lines thereat, a trunk line from each primary selector switch to an auxiliary switchboard, with answering terminals thereon, and means to determine the activity of the primary selector switches in accordance with the condition of the load on the main switchboard.

4. In a telephone system a main switch-v board having answering positions and subscribers lines apportioned to each, a pri- -mary selector switch associated with each position and containing terminals of the lines thereat, a trunk line from each primary selector switch to an auxiliary switchboard, with answering terminals thereon, and means actuated by a predetermined increase in the load on any position of the main switchboard to render the corresponding primary selector switch or switches active.

5. In a telephone system a main switchhoard having answering positions and subscribers lines apportioned to each, a primary selector switch associated with each position and containing terminals of the lines thereat, a trunk line from each primary selector switch to an auxiliary switchboard, with answering tcrminals thereon, and means controlled by the subscribers in calling to render the primary selector switches active when a predetermined number of calls remain unanswered on the main switchboard.

6. In a telephone system a main switchboard having answering positions and subscribers lines apportioned to each, a primary selector switch asociated witheach position and containing terminals of the .lines thereat, a trunk line from each priscribers lines apportioned to each, a primaryselector switch to an auxiliary switchboard, with answering terminals thereon, and arelay connected to be controlled by current due to subscribers, calling so as to render a primary selector switch orswitches active, when a predetermined number of subscribers calls are unanswered on the main board. I v

7. In atele hone exchange system a main switchboard lgavingsubscribers line-terminals and lineisignals, an automatic primary 8. In a telephone exchange system, a plu ralityof subscribers lines: and a plurality of switching means to interconnect the same,

multiplejconnections from the lines to the several switching means, and controlling devices responsive to fluctuations in the calling load, adapted to determine the particular switching means to be used for any partlcular connection desired.

9. In a telephone exchangesystem, a manual switchboard and automatic switching devices, a plurality of subscribers lines having multiple terminals in both, and

means determined by load conditions to switch the lines for conversation through 7 either.

Copies of this patent may be'obtained for 10. In a telephone exchange system, a plurality of subscribers lines, a main manual switchboard for interconnecting the lines, and an auxiliary switchboard therefor with automatic answering means'and' automatic control.

11. In a telephone exchange system, a pluralit'y' of subscribers lines, a main manual switchboard for interconnecting the lines for conversation, and an auxiliary switchboard also adapted to interconnect the lines and automatically controlled by current changes due to calling load changes on the main switchboard. a I

12. In a telephone exchange system, a

plurality of subscribers lines, a main switchboard provided with manual connective apparatus, an auxiliary switchboard provlded with automatic answering sw tchmg means, and means at said'cen'tral station for determining the furtherance of a desired connection either through said manualconnective means or through said automatic switching means and independently 'of the manual connective means. A

13. In a telephone exchange system, a

plurality of subscribers lines, a' main switchboard provided with manual con -nective apparatus for normally inter'con- 'necting the lines, an auxiliaryswitchboard provided with automatic switches and means connection for automatically effecting through said switches as determined-bythe number of calls.

In testimony whereof I afiix my signature in presence of two witnesses;

EDWARD E.

Witnesses E. EoMoNs'roN, Jr., JAMES H. MARK.

five cents each, by addressing the Commissioner of Patents, Washington, G.

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