US1107145A - Telephone-exchange system. - Google Patents

Description

Patented Aug, 11, 1914.

3SHEETSSHEET 1.

E. B. CLEMENT.

TELEPHONE EXCHANGE SYSTEM APPLIGATION FILED JUNEZZ, 1906.

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TELEPHONE EXCHANGE SYSTEM APPLIUATIOB FILED JUNE 22, 1906 3SEEETS SHEET 2.

CLEMENT. TELEPHONE EXCHANGE SYSTEM:

APPLICATION FILED JUNE 22, 1906.

UTE stares Par EDWARD E. CLEMENT, O VIASHINGTON, DISTRICT OF CGLUMBIA, ASSIGNS'R, BY

MESNE ASSIGNMENTS. TO FREDERICK C. STEVENS, OF ATTECA, NEW YORK TELEPHONE-EXCHANGE SYSTEM.

Specification of Letters Patent.

Patented filing. it,

To (ZZZ whom it may concern:

Be it known that I, EDWARD E. CLEMENT, a citizen of the United States, residing at ll ashington, in the District of Columbia, have invented certainnew and useful linprovements in Telephone-Exchange Systems, of which the following is a specification, reference being had therein to the accompanying drawing.

My invention relates to telephone exchange systems and has for its principal ol ject the improvement of such systems by decreasing the number of operators required for a given number of lines and facilitating their W01; to the highest possible degree.

In order to attain my object I employ a combination oi apparatus and circuits, portions of which are of the well known manual type and other portions automatic in their operation, such combinations being known as semi-automatic A very important corollary or subsidiary object of the invention is to increase the capacity of existing exchange switch-boards of the manual type and to render it possible to convert them into semi-automatic equipments, at the same time increasing their efficiency as well as their capacity.

Other objects will appear from tln description hereinafter.

Briefly stated, my invention comprises a system in which the subscribers lines terminate on the usual answering jacks in a manual switchboard, but instead of being provided with multiple acks for connecting purposes, the lines are provided with multiple terminals in automatic switchesot any desired or suitable type. The operator is provided with cord circuits of a single-plug type and terminating before the operator in an answering plug. The usual supervisory lamp and relay for this plug are provided as well as a controlling relay, a cutoff and line relay for each line, and an operators listening key. From the answering plug of each cord :1 pair of trunk conductors extend directly to an automatic selector switch containing multiple terminals through which the subscribers lines may be called. Associated with the cord is a group of keys by which the operator may direct groups of impulses over the trunk to control the move ments of the automatic switch or switches, and finally, automaticapparatus associated with the switching device tests the wanted lines and sends out ringing current in case the line is found clear.

This system is applied to existing manual plants by severing the ordinary cord circuits and using them as I have described, each end of the ordinary cord circuit furnishing one complete terminal for an automatic trunk. The subscribers lines are then disconnected from the multiple jacks, preferably at the intermediate distributing frame, so that the multiple jack strips and their cable may be removed bodily. Experience demonstrates that an operator when relieved, as in this case, of the burdens of testing, ringing and supervising, can do more than twice the work and can handle more than twice as many lines as under the old system. Thus, each operator can handle two positions, so that only half the number of operators are needed to manage the same switchboard, but where the capacity of the board is to be increased. answering jacks and lamps are added in the panels eft vacant by the removal of the multiple jacks. The number of automatic switches required, and the anmunt of cable and subsidiary apparatus, relatively small in cost when the increased capacity and the great eiliciency of the service are taken into account.

hi invention is illustrated as to one embodiment in the accompanying drawings in which- Figure 1 is a diagram of a subscribers line and a central oilice switchboard circuit in which it terminates, together with an answering plug and a portion of the cord circuit thereof. Fig. :2 is a similar diagram complemental to 1 showing a trunk ex tending from the cord circuit to an automatic switch. Fig. 3 is a diagram of the operators controlling circuits and keys.

The system of my invention is herein illustrated and described as applied to an exch ngc of but one hundred lines, but it is to be understood that the number of lines is limited only by the selecting apparatus oi:

Figs. 2 and 3, the selective apparatus of- Fig. 2 being of any desired type. 'Many types of impulse-controlled selective and connective apparatus are now known to the art, some of them providing for indefinitely large exchanges by a system of successive selective devices, the subscribers lines being found only in the last connector of the series of switches; lVith devices of Fig. 2 adapted to respond to impulse control, in a manner well known to the art, the devices of Fig. 3 require a similar extension in that the .sets of keys must be increased to provide for the sending of as many sets of impulses as the devices of Fig. 2 require, but the extension of the apparatus of Fig. 3'is simply the'duplication of the sets of keys already shown in that figure.

Referring first to Fig. 1, A is a subscribers station equipped with the usual talking and signaling apparatus such as may be found in every modern common battery exchange-system. This comprises a trans mitter, receiver, switch-hook, ringer and condenser, with or without an induction coil according .to the make of the instruments used: In the diagram no induction C011 is shown, however. The line wires are marked 1.-2-and extend to the central office C where they terminate upon the contacts of the cutoff-relay N. These contacts are shown as armatures, but commercially they are usually contact springs controlled by the 3 armature of the relay. They are normally electrically as shown, connecting the wire 1 to ground on one side, and wire '2 to line relay M and thence by Wire 5 to the battery Ben the other. When the subscriber removes his telephone from the hook, current will flow through the line relay, energizing it and lighting the lamp on by closing the branch circuit 6 to ground, Passing from front contacts of the cut-off relay are two extension wires 7 and '8 terminating at the answering jack- J I and having parallel connections 9 and 10 to the multiples or connecting terminals 8 which are in the banks of several automatic switches, presently to be described.

Cooperating with the answering jack J is an answering plug P having tip and sleeve contacts through which the cord conductors 11 and 12 pass as far as the condensers c, and 1 being inductively connected therethrough to the trunk conductors 13- and 14 leading to the automatic switch S of Fig. 2. Connected between the battery and the sleeveside 11 .fi-the cord circuit is the relay R whichcontrols the battery supply to the armature contacts of, the supervisory relay Rflwhile passing through its own coils is the supply of current both for the subscribers station in talking, and for the cut-off relay N which is usually made with 500 ohmsresistan ce in its windings, composed of many turns of fine wire connected in a ground tap through the sleeve Wire 7 of the line extension. The supervisory relay R on the other hand is tapped off to ground from the tip side 12 of the 0 1rd circuit, and "ClIIQCtIYICOIIlZIOlS the supervisory lamp '1' associated with'the plug P.

The trunk iretap-14 extend to a selector or connector switch or switches, 6f which that shown in Fig. 2.is given as an example. As to their mechanical parts, the switches are of the type shown in patents to Keith and Erickson, 815,176 and 815,321, both dated March 18, 1906; with the exception that I prefer not to employ a so-called side switch shown in those patents, using purposes of control. The main mechanical features, however, are the same, hence 1 have not thought it necessary to describe this type of switch herein except diagram matically. The banks of contacts 8, are in curved rows, each switch containing one or moreof these rows as shown in the said patents, and having a spindle s carrying wipers s which are adapted to be broughtinte connection with any pair-of contacts in any row by a double motion of the spindle,- one component of the motion being vertical produced by a ratchet controlled by the magnet 8 and the other component being rotary produced through a circular ratchet by the so-called rotary magnet 8 The trunk 1314 shown in the diagram, leads to the connector switch S, shown in Fig. 2, and this switch is operated by means of impulses over the two sides of the trunk, 9 in a manner which is generally familiar to those acquainted with the art. In order to do this I provide the operators with impulse transmitters or senders. For eonvenience I will first describe this arrangement as it is shown in Fig. 3, and will then proceed to point out its effect upon the apparatus of Fig. 2. In Fig. 3, Q Q, Q, Q Q Q, ,Q, etc., are a set .of wheels mounted on and turning with a common shaft, which may be driven in any suitable manner. The wheel Q", puts battery and ground alternately on the Wire 29, which for purposes of illustration represents the metallic shaft connection between the wheels. The wheel Q, which is insulated from the shaft is grounded, has an insulating spot in its periphery, and controls by means of this spot the locking and unlocking wires 30 and 31, in a manner which will appear from the statement of operation. The wheels QQ'QF, Q Q Q etc., are number wheels, tlre first one having one tooth, thesecond two teeth and so on up to ten teeth. (For simplicity of illustration only five wheels are shown). Around these wheels are three sets of pens, connected to the three sets of keys K, K K As the wheels revolve from the nor--- mal position of rest in which they are shown in the figure, they first make connection their buttons or keys, K, transmit the tens digit of any number, the next set transmit the units digit, and the third set transmit 130 with the upper pens, 9, then with the'pens then with those, 9 The first set with th ringing number for party-line work. only finishes setting up the number, but by All this will appear more clearly from the closing the springs, 7:, puts ground on the statement of operation.

The keys, K, K are of the so-called self-latching selective ringin type now in common use on manual switchboards, and employ the principle shown in the patent to 5 m, lIo. 605,097 granted June 7, 1898. l 'l hen any key is pressed down it pushes buck the latch and releases the one that was previously dowinthen latching itself. The eye of each row are thus-interlocking, the ows being independent; thus one key of each row remains depressed. Each set of has a common wire, this for the sets K being marked 32, these two being ogether and carried to a hack conrelay Ps while that for the set o the same relay, separately conpressing the keys, and then the signal is started at is about to strike its pen by the relay,

final locking position. The

remains energized. The trick of this is in the arrangement of the spring pens 9, n the wheel C3. This wheel is rotated with the others in the direction of the arrow, and its insulating spot passes first nder the spring pen g momentarily writing ground mi of that and the wire 31, then under the pen g taking ground off of that.

In calling to number wanted, which we will assume to be 32-3, the operator plugs into the calling aclr, then presses down but-' ton No. 3 of the set K; 2 of the set, K and l lo. 3 or" the K The buttons of the sets K ant K have their several individual wires connected to the springs on the several individual wheels Q, Q3, etc, and the effect of pressing down the buttons as mentioned is to connect the pen or" the through the springs of the butwire 82. A r the same time the pen g of the wheel Q} connected through the springs k of the button 1 6 to the w re 33 and the spring 9 of the wheel Q3 con-- nected through the springs 70 of the button bite the wire 32. The also have what I may call starting springs it". Keys of the type shown in Ham, cited, pass downward through a maximum travel and return slightly to engage the locking shoulder. I take advantage of this and so adjust the springs 7c max mum travel and return,

that they close at the break upon the slight being open when-the key is in its springs Z2,

- however, remain closed when the key is locked. or ringing set, the number is ready for transmission when any one of them is depressed, hence any one of these buttons not through up, and both lock, the

.Lhe numhersto be sent are set up.

the beginning of a rotation of the shaft, when the first tooth of each wheel set of buttons, K"

call This set of buttons beingthe last,

starting wires 3'? and 38, which pass to the two relays, 3*, R respectively, and thence the common return wire 39 to battery B and ground. Both the relays pull locking circuit of the relay B being as follows: B, 39, R 7*, 30, 9, Q. and ground- The locking circuit of R is as follows: B, 39, R", 1' 31, g, Q and ground.

Having thus set up the signal in condition to be started at of a revolution of the main shaft, the operators work is finished. She pays no further attention to the connection until the subscribers have completed their conversation and have hung up, whereupon the relay t in Fig. l lets go, and the lamp, 7', lights to call for disconnection. The operator then pulls the plug P.

The signal having been set up asdescribed, the apparatus of Fig. 3 then operates as follows: The wheel, Q, in revolving will bring the insulating spot under the pen,

and put it the bcglnning 5 at first, and might thereby cut oil the relay, ll, prematurely, but this is provided for by making a branch locking circuit 310 which controlled through a contact of the armature r and a. ground wire 36 of the starting relay Bi Hence, as long as the relay ll is energized, the relay ll cannot be affected. Moreover, it will be observed that the wires 32 and 33 remain disconnected from'tho wires 15l6 until the relay ll is energized, while the relay R is deencrgizcd. This condition is br--1gl1t about when the insulating spot reaches the pen 9 he relay R then lets go, and we have a continuous circuit from wire as follows: 32 34, 1' 16, and to trunk wire 1%. /Ve also have a circuit for wire 33 as follows: 33, T 35, r 15, and the other trunk wire Tho insulating spot reaches the pen 9* just before the first tooth on each wheel reaches its pen q; hence as soon as the above desired condition isattained, the set of battery impulses which has been deter fined by the key is of the set K", comes over the wire 32 to the wire 16 and so onto the wire 1% of the trunk, through which it passes into Fig. 2 to the relay R which will be presently described, and which I shall for convenience the vertical relay. At the end of this group of impulses, the teeth on the wheels the pens g and so the next group of ground impulses determined by the key 70 will pass onto the wire 33 and so to the wire 15 and' the trunk wire 13, through which they reach the relay R in Fig. 2 which will also be presently described and which I shall for convenience call the rotary relay. The names of these two relays are quite accurate in this system,'because the relay B does will have gotten around to really produce a vertical motion of the switch S, while the relay R produces a rotary motion thereof. At the end of this second group of impulses, the teeth on the wheels have gotten around to the third set -of pens g and the battery impulses determined by the keys then come through the wire 32 onto the wire 16 and so again to the trunk wire 14 and to the vertical relay R. After this, the insulating spot on the wheel Q. reaches the spring 9 and momentarily cuts off the ground therefrom. Since the relay R is already deenergized, this breaks the locking circuit of the relay R and it'lets go, disconnecting the wires 15- 16 from the wires 3534, and leaving the apparatus free for another operation.

ieferring now to Fig. 2, I will briefly describe the switch operation. The switch spindle controls a pair of springs s which it opens when it is down in its normal position of disuse, for restoring purposes, as will presently appear. 3 is the release magnet of the switch, which when energized removes the detent pawls from the respective ratchets of the spindle, .9, allowing the spindle to drop down and rotate back to zero, as fully described in the patents referred to. This release magnet is under the control of the relay R which in turn is controlled by the relays R and R. It is also under the control of the test relay R. R is a ringing-selection control relay, R is a trunk cut-off relay and R is a ringing relay controlledby the connnutator X which is common to the entire exchange. R is a slow acting relay, preferably a solenoid, which connects the test relay R, as controlled by the first ringing impulse, and at the same time opens the generator circuit 40-4l, while the proper current is being selected. R to R, inclusive, are selective relays for enabling one or the other of the ringing generators, G, G, G and G ,to be connected onto the ringing contacts of the ringing relay, R the particular generator being determined by the number of impulses received through the relay R which operates the relays R R R R R R, in succession, each of them looking as it operates. v

The operation of this trunk scheme is as follows: In selecting the'number we have assumed 323: we have first three impulses over the wire 14 to the relay R, then twov ground impulses over the wire 13 to the relay R", and then three impulses again over the wire 14 to the relay R. The first three impulses coming over the wire 14 caused the relay R to pull up three times, each time closing the following circuit: B, 42, 43, 44, s", 45, 46, 47, and ground to battery. The vertical magnet 8 steps the spindle s of the switch up three steps, so that the wipers-.94 staald opposite the third row of contacts. Two impulses thencome over wire 13, affecting the relay R which pulls up twice, the first time closing the following circuit: B, 42, 48,.R, 49, 50, armature of R 51 to ground and to battery. The relay R instantly pulls up, cutting ofi? the vertical magnet, 8 and locking itself by the following path: B, 42, 48, R 9*", 52, 50, 51 and ground-back to battery. The vertical magnet s is therefore cut ofi for the rest of the transmission. The rotary magnet 8, however,gets current each time the relay, R is energized, over the following path: B, 42, 43, 44, s, 53, 54, 55 and ground back'to battery. The rotary magnet 8* turns the spindle .9 two steps, so that the wipers 8 rest on the second pair of contacts in the third row, or No. 32. Three impulses now come over the wire 14, causing the relay R again to pull up three times. Each time it closes the following local circuit: B, 42, 56, R 57, 46,47, and ground back to battery. As a branch of this same circuit, the wire 58 comes in from battery wire 42 and goes to 57, 46, 47 and ground, so that the solenoid R is energized as well as the relay R At this point in the development of the connection immediately following the closure of the contacts of relay R at tliebeginning of thefirst generator-selection impulse, two things occur simultaneously:

(1.) The solenoid R attracts its core, opening the wires 4041 and closing the switch (32 whereby a test circuit is formed through elements 13,42, 62, R 63, to upper 8', which at this moment is resting in contact with the line selected through the agency of vertical and rotary magnets s 8*,- if the line be busy then a circuit will exist from upper wiper s to the'tip of the plug and through the relay R to ground in case the line tested has called or to another wiper s and thence through a trunking equipment following the'path through contact of R, contact of R conductor 14 and winding of R to ground if that line has been called; in either case the test relay R will be energized and in turn will energize the release magnet 8. If, however, the selected line with which the test wiper rests in contact is not busy no cir-. cuit will exist from that test wiper to ground and the test relay R wild not be energized; a branch, path from the con-' ductor 63 exists through the talking conductor of the trunk to the left hand contact of relay R and thence to an armature contact of relay R where itterminates open, but subsequent to the energization of relay R as about to be described, this branch path passes to the inn contact of the left hand armature of that relay and thence over the conductor 41 to the right hand switch of the solenoid R which during the test period is open, and thus test .with respect to those wheels relay R has its circuit open at all points anclrthe design of the device as a whole is that no. energization of that relay may result when the line selected is in a condition of disuse and subject to use in the connection now being established.

(2.) The relay 3 is energized over the path B, 42, 56, R 57, 46, 47 and ground. By the closure of the left hand armature'of relay R circuit is formed through elements B, 42, 56, armature of R 60, Winding of B 61, switch 3 and ground, energizingrelay R which looks itself energized over the circuit B, -12, armature and inner contact of relay R Winding of relay R 61, 8 and ground. This energization of trimk-connecting relay R connects the conductors 13, 14 of the trunk through to the outer contacts of the ringing relay R and through to the wipers s. This furnishes a path through test relay 3 as follows :B, to, 24, 62, R 63, talkconductor to left-hand armature of R back contact and talking conductor to armature of energized relay R conducto 14, winding of relay R and ground; however, this circuit is adapted to he opened by the attraction of the ii-matures of rela i, and it is the function of the connector switch that the opening of this circuit at R shall succeed its closing at R by a time limit so small that restoration of the connector switch is not permitted. It will be noted in the study of this time element that the test relay it must attain the degree of mugnctizatirn required to attract its armatre, must swing its armature through its full travel to close its Contact, and that subsecucntly to the closure of the contact of the release magnc, must reach its re- 7 ed degree of magnetization and must overcome the inertia of its armature and more it through some definite are before release of the switch S will be effected; this series of necessarily consecutive operations limits the durstion of the momentary l aise test here considered. The commutuc )1 X,

has been mentioned, is

'.' -d upon the shaft which carries the numbe, wheels and commutator devices is)", Q. i the commutator X is ad}:

ducting portion of X all connection with its brush #1? the that the energization of relay R cc It seen therefore that by the closing of the contacts of relay R b which current iiow through test relay it was permitted, current flow also was simultaneously provided for through path il, l), winding of R, contact and armature r, 5''? m and round. Thus current b through 1nd the w sumo through i suming equal speed in the operation of illllllltlllQS, relay R will have moved its armature and will have brokcudts back contact, thereby cutting otf curzeiit from relay R in ample time to prevent the rcstor; tion of the switch S by operation of release magnet 8, the break at thearmature of It probably occurring in time to prevent any contact whatever at the armature of relay ll. Thus a test condition is maintained with the test wiper s isolated from the winding of relay R" by the break at the armature of relay it, and the design and adjustment of the con'unutator X shall be such that the relay It is held energized throughout the maximum period occupied by gcnerator-selection impulses and until the opening of the circuit of tlie test relay R by the opening of the switch (12 upon release of the armature of the solenoid R The armature of the solenoid R is sluggish and does not open the switch 2 between the generatonselection impulses, so that the test circuit here described is maintained continuously during the period of generator-selection.

Leaving the various parts of apparatus in the condition now considered, we will follow the action of the appa utus in response to the generat r-selection impulses. In the instance assumed, since station No. 3 is to be called, three battery impulses will be received over the wire 1% operating the armature of the relay R successively three times, which in turn acts over the path 47, do, 57, it, etc. to operate the armatures of relay it in succession three times; the armature 1" through its front and back contacts eli'ects the selection of the desired ringing generator as follows: Upon attraction of r by the first g0nerator-selection impulse, it makes electrical connection with its inner contact, but inasmuch the wire (H- is open at the armature of relay R no complete circuit is closed. Upon the release of the arnmture r at cessation of the lirstgenerator-selcctizm impulse, circuit is closed through elcments'B, 2, 43, contact of R 60, 9', (15, contact of R winding of R and ground, energizing relay R which locks over the circuit 13,42, 43, contact of R, (30, (if), Armature and contact of R winding of ii and ground. If but one generator-selection impulse were received, the generator G would remain in connection. with conductor 40 ready for connection through conductor 41 to the ringing relay B. At the beginning of the second generator-selection impulse, relay R is energized and armature it which then locks over the circuit 13,42, 43, contact of R 60,69, armature contact and winding of R Upon the cessation of the second generator-selection impulse, the armature 1 is released, closing circuit over B, 42, 43, contact of R 60, 1

'65, closed Contact of lower armature of energized relay It, back contact of lower armature of unenergized relay R winding of relay R and ground, energizing relay R which then locks itself through its own contact by current received over conductor 69 to ground as in the case of relays R and R. If no more generator-selection imulses were received, the effect of the' two impulses thus far followed would be to leave generator G connected to conductor 40 through contact of energized relay R, that being the proper generator for ringing the second station on a party line. At the beginning of the third and last generatorselection impulse; the armature r is again attracted, closing circuit over elements 13, 42,43, contact of R 60, 1' 64, closed contact of energized relay R closed inner contact of energized relay R, closed outer confact of unenergized relay R winding of relay R" and ground, energizing relay R", which then locks itself by current through its own contact and Winding over conductor 69 to ground. Upon the cessation of the third and last generatorselection impulse, the amature r is released, closing circuit through elements B, 42, 43, contact of R 60, r, 65, closed inner contacts of energized relays R and R closed outer contact of unenergized relay R Winding of relay R and ground, energizing relay R which then locks itself by current through its own armature. contact and winding from conductor 69 to ground. This leaves relays R and R" energized and leaves relay R unenergized, thus effecting the connectionof generator G to the conductor 40, and as the generator-selection impulses now cease, solenoid R releases its armature, opening the circuit of the test relay R and closingthe circuit between conductors 40-41, thus connecting the selected generator G over conductor 41 to the inner contact of the left hand armature of ringing relay R and thus through the upper wiper s and to the lineconductor of the selected line to ring the third station upon'the party line selected.

The ringing will continue until the insulatedportion of the'commutator X passes under the brush of that commutator when the circuit of the winding of relay R Will be interrupted and by release of that relays armature the circuit from the wipers s will ergized and to periods of non-ringing when the relay R 'is de'energized. Upon theanswering of the called sub-station, or of any substation upon that party line, during a period of non-ringing, current immediately will flow through elements 'B, 42, winding of R, 13, lower 5', line conductor, substation 70 bridge, return line conductor, uppers 14, winding of R and earth, energizing R and attracting its. armatures.

By theoperation of the left hand armature of R, circuit isclosed through ele-' 7 ments B, 42, left hand armature and inner contact of R, winding of R 54, contact and left hand armature of-R, 55 and ground, energizing R which then locks over the circuit B, 42, right hand armature and the condition of conversation and continues until the hanging up of the telephone 9 and the breaking of the substation bridge upon the called line; v

Upon the hanging up of the telephone and the breaking of the substation bridge upon the called line, disconnection of the 9 switch S is effected as follows: Circuit is interrupted over the return wire of the line and through relay R to ground, releasing the armatnres of relay R, but current continues through elements B, 42, Winding ofx R 13, lower wiper s, and the sleeve side of the connected line and the winding of its cut-off relay N to ground, maintaining the energization of the relay R. By the release of the left hand armature of relay R a re- 1 lease relay circuit is established through elements B, 42, left hand, armature and outer contact of deenergized relay R, winding of release relay R inner contact and armature 1 of relay R 51 and ground, energiz- 1 ing release relay R which, by closin its contact, energizes release magnets 3 wich effects immediate restoration of all parts of the switch S to the normal position of disuse. 1 A consideration of test conditions during the process of the connection is desirable. When the test wiper or upper wiper 8 connects with the test conductor of the line, no action is taken either to test for busy or to place a busy test upon the line until the wheels Q, Q Q etc., have in due course of progress begun to send the generatorselection impulses; at this time, by the action of the solenoid R the selected line is tested for busy condition, the testing for busy being continued throughout the receipt of the enerator-sele'ction impulses and the line bemg left unguarded against connection by other connectors; at the close of the V thereto. for an exchange of more than ill lines scribe generator-selection impulses, the test relay is taken off and the ringing generator is substituted. Fronr this time a busy test guard condition is placed upon the test conductor of the selected line, being alternately the potential of the selected ringing generator when the relay .R is energized, which is sutficient to energize any relay R which may test the line during the interval of ringing, and between the intervals of ringing the busy test consists of the ground cir' cuit through the relay R. If the line thus connected with be tested for busy by some other connector attempting a connection with it and during the interval of deenergization of ringing relay R, a current will flow from the connector then testing to the test conductor of the line, thence through the test wiper of the connector of Fig/ 2.

holding the line, and through back contact of relay R, front contact of R 28, and winding of R to ground. his current will be of suf icient strength to energize the test relay R of. the distant connector attempting to talte the line being held, and this will effect disconnection of that connector but it will not be of sufficient strength to energize the relay 1 1 inasmuch as by the energization and subsequent deenergization of that relay, the said testing current would also restore the holding connector of Fig. 2 to its normal condition of idleness.

I have thus described and stated the operation of one form of my invention. Many changes can be made therein without departing from the spirit thereof.

The equipment shown in the figures of the drawings herewith sullicicnt as regards the automatic switching for an cxchange of lines or less, in which there are say ten of the switches shown in Fig. 7 each line having ten multiple contacts 8 Th invention is obviouslv applicable to exchanges of any size houercr, by merely extending the circuits and increasing the operators in accordance with well understood rules. The particular form of switch employed is not material to the present in voution, nor are the switch circuits shown in Fig. 2 specifically necessary. 'lhcy may he the same as those commonly mnploycd in llu Strowgor system, using the switches shown in.the Keith and Erickson patents hereinbefore referred to. The number of submay be anything desired, and the switchl apparatus shown in Fig. 2 will he sv .inetrically increased proportionally The trunk lines l4.l. 3 of Fig. 1.

would pass to a first selector swita, which would be. controlled in the same manner as the swi ch illustrated in Fig. 2, by impulses over t ank wires, to pick out an auxiliary s which would then be controlled next step and so finally to selectthe line wanted. As this system of switching is familiar to those skilled in the. art, and i shown in Letters Patent, it is unnecessary for me to go further into it here. The plugs P in front of an operator do, not represent any particular group of subscribers but are merely terminals or" first selector or connector switches by which any subscriber in the exchange can be reached. An exchange of 100 lines with connector switches only is shown, but as l have stated, this might as well be 1,000 or IQQOGG. In case of numbers having more than two digits, however, the number of sets of buttons in the sending device of Fig. 3 would oi course have to be increased accordingly, one row of buttons and one additional set of contact springs on the sending device being added for each digit. Thus, for a 1,000 line exchange there would be four rows o buttons instead of three, in a 10,900 line exchange five rows and so on; one of the rows in each case being reserved for selective ringing as described herein.

My claims should be construed in view of the foregoing remarl-zs a they are not intended to be limited to any particular numher or arrangement of automatic switches or any particular number of subscriber lines in an exchange. The gist of the invention lies in the combination and arrangementof the line terminals, the trunk plugs, the

switches for completing the connections and the operator's sending circuits.

ll aving thus described my invention, what I claim and desire to secure by Letters Pat cut is:

l. in a telephone system, the combination of subscribers lines, an answering jack and a calling signal for each of said lines, auto. matic connector switcl es in which i'nultiples of said lines appear, trunks from switching plugs to said automatic switches the plug ends of said trunks being adapted to connect with said answering jacks, and a constantly-driven signal-sending device with locking signal-selecting keys for controlling the movements of said automatic switch to connect its trunk to the terminals of a desired line.

2. la a telephone system the combination of subscribers" lines. a calling signal and answering jack for each of said lines, automatic connector switches in which multiples of said lin'cs appear, trunks from answering plugs to said auton'iatic switches, and a constantly-driven s1 rial-sending device with a desired line.

In a telephone system, the combination of subscribers lines, a ack and signal tor each of said lines, automatic connector switches in which multiples of said lines appear, trunks to said automatic switches, a switch plug for each trunk for connecting the trunk to a calling line, and a constantly driven signal-sending device with a bank of'locking signal-selecting keys per trunk for controlling the movements of said automatic switch throughout "a plurality of successive directory digits to connect its trunk to the terminals of a desired line.

4. In a telephone system, the combination of subscribers lines, a calling jack and sig-. nal for each of said lines, automatlc connec- V tor switches in which multiples of said lines appear, trunks to said automatic switches, manual means for connecting a calling line to one of said automatic switches, and a constantly driven signal-sending device with a bank of locking signal-selecting keys, associated with each of said trunks for controlling the movements of the automatic switch of the trunk throughout a plurality of successive directory digits to connect the trunk with a desired line.

5. In a telephone system, the combination of subscribers lines, a jack and signal for each of said lines, automatic connector switches in which multiples of said lines appear, trunks to said automatic switches, plug ends on safil trunks to connect with said answering jacks, and a constantly driven signal-sending device with looking selecting number keys for controlling the movements of said automatic switch to connect its trunk to the terminals of a desired line.

6'. In a telephone system, the combination of-subscribers lines, a jack and signal for each of said lines, automatic connector switches in which multiples of said lines appear, trunks to said automatic switches, plug ends on said trunks to connect with said answering jacks, and a constantly driven multiple-signal-sendin'g device with locking se-- lecting number keys and associated with said trunks for controlling the movements of said automatic switches to connect the trunks to the terminals of desired lines.

7. In a telephone system, the combination of subscribers lines, a jack and signal for each of said lines, automatic connector switches in which multiples of said lines appear, trunks to said automatic switches 'directly .from answering plugs, and a con stantly driven multiple-signal-sepding device for controlling the movcmeitsol an automatic switch to connect its trunk to the terminals of a desired line.

8. In a telephone system, the comliiimtion of subscribers lines, a jack and signal for each of 'said lines, automatic connector switches inwhich multiples of said lines appear, trunks to said automatic switches directly ircln answering plugs, and a constantly driven multiplesignal-scmling device for controlling the movements of an automatic switch throughout a plurality of successive directory digits to connect its trunk to the terminals of a desired line.

9. In a telephone system, the combination of subscribers lines, a jack and signal for each of said lines, automatic connector switches in which multiples of said lines.

appear, trunks to said automatic switches, single-plug manual switching means for connecting a trunk and a calling line, aconstantly driven signal-sending device, and locking signal-selecting keys associated with ,,said trunks for controlling the movements of an automatic switch to connect its trunk to a desired line.

10. In a telephone system, the eombination of subscribers lines, a ack and signal for each of said lines, automatic connector switches in which multiples of said lines appear, trunks to said automatic switches, manual switching means for connecting a 'calling line with a trunk to one of said automatic switches, a constantly driven signalsending device, and locking signal-selecting keys associated with said trunks for controlling the movements of an automatic switch' to connect its trunk to the terminals of a desired line.

11. In a telephone system the combination of subscribers lines, a jack and signal for each of-fsaid lines, automatic connector.

switches in which multiples of saidlines-appear, trunks to said automatic switches, manual' means for connecting a calling line with a trunk to one of said automatic'switches, a constantly driven signal-sending device, and locking signal-selecting keys associated with each of said trunks for controlling the movements of its automatic switch through a plurality of successive directory digits to connect 'that trunk to the terminals of a desired line.

12. In a telephone system, the combination of subscribers lines, a jack and'signal for each of said lines, automatic connector switches in which multiples of said lines appear, trunks to said automatic switches, a constantly-driven multiple-signal-sending device, manual means for connecting a call-- ing line to a trunk to an automatic switch, and sets of lOClflll signal-selectlng keys for each of said trun s whereby 1ts automatic switch may be controlled to-connect that trunk to the terminals of a desired line.

13. In a telephone system, the combination of subscribers lines, a jack and signal for each of said lines, automatic connector switches in which multiples of said lines appear, trunks to said aulomatic switches, a constantly driven multiple-signal-scntling device, answering plugs for connecting a trunk to a calling line, and sets of signal-selecting keys for each of said trunks whereby the automatic switch of that trunk may be conll'nllod throughout plurality oF successive directory digits to connect that trunk to the terminals of a desired line.

1%. ln a telephone exchange system, a plurality of subscriber" lines, a plurality of automatic switches ard a trunk for each, isingleplug switching means manually controll d by the operator for connecting an idle switch trunk to a calling line, automatic actuating means for the switches adapted to be manually preset so as whole number of the line wanted, and unitary means for each trunk manually con trolled by the operator for determining the application of said actuating means to said trunk, after setting up the number.

15. In a telephone exchange system, a plurality oi line circuits each having a telephone and signal device at a substation, and a terminal answering jack with an associated call signal at the central ofiice, a num ber of connective circuits each comprising an answering with said jack, automatic switching apparatus for selecting and connecting with a wanted line, and a trunk directly connected to and terminating in said plug at one end and sin'iilarly connected to the switch at the other, and controlling means for said switchto transmit the plug adapted to cooperate.

ing apparatus adapted to be manually actuated by an operator, and in turn to actuate the switching apparatus, together with a common battery source of energy supplying all of said elements including the talking circuit.

16. In a telephone exchange system, a subscribers line circuit terminating at a central otiice in an answering jack, an answering plug for said jack, an automatic switching apparatus adapted to connect with various subscribers lines, a connective trunk directly connected at one end to and terminating in said answering plug, and at the other end similarly connected to and terminating in said automatic switching apparatus, and means manually controlled at the central ofiice for actuating said switching apparatus, together with supervisory signal apparatus for the connector switch at the plug end of said trunk.

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

EDlVARD E. CLEMENT.

\Vitnesses:

E. Ennoxs'ron, Jr., Janus H. Mann.

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