US1557993A - Automatic telephone-exchange system - Google Patents

Description

Oct. 20, 1925. 1,557,993

A. H. DYSON AUTOMATIC TELEPHOIiE EXCHANGE SYSTEM Filed July 12 11 Sheets-Sheet .1

Oct. 20, 1925. 1,557,993

A. H. DYSON AUTOMATIC TELEPHONE EXCHANGE SYSTEM Filed July 12, 1906 11 sheets sha'et 2 Oct. 20,1925. f v A 1,557,993

A. H. DYSON AUTOMATIC TELEPHONEEXCHANGE SYSTEI Filed July 12, 1906 11 Sheets-Sheet 5 Oct; 20, 1925. 1,557,993

A. H. DYSON AUTOMATIC TELEPHONE EXCHANGE SYSTEI Filed Ju1y 12, 1906 Sheets-Shoot 4 Oct. 20,1925. 1.557593 A. H. DYSON AUTOMATIC TELEPHONE EXCHANGE SYSTEM Filed Jul 12, 1906 11 Sheets-Sheet 5 Oct. 20,1925 1.557.9 3

A. H. DYSON AUTOMATIC TELEPHONE EXCHANGE SYSTEM Filed July 12 1906 11 Sheets-Sheet 6 Oct. 20, 1925.

A. H. DYSON AUTOMATIC TELEPHONE EXCHANGE SYSTEI Filed-Julylz, 1906 11 Sheets-Shoot '7 A. H. DYSON AUTOMATIC TELEPHONE EXCHANGE SYSTEM Oct. 20, 1925- 1906 11 Sheets-$11661. 8

Filed July 12 Oct. 20, 1925.

1,557,993 A. H. DYSON AUTOMATIC TELEPHONE EXCHANGE SYSTEI 11 Sfiets-Sheet 9 Filed July 12 1906 Oct. 20, 1925. 1,557,993

- A. H. DYSON AUTOMATIC TELEPHONE EXCHANGE SYSTEM Filed July 12, 1906 11 Sheets-Sheet 10 Oct. 20, 1925. 1,557,993

, A. H. DYSQN AUTOMATIC TELEPHONE EXCHANGE SYSTEM Filed July 12 1906 11 Sheets-Sheet 11 till Patented Oct. 20, 1925.

UNITED STATES ALFRED H. DYSON, or CHICAGO, ILLrnoIs, A-ssIe NoR, BY MESNE KELLOGG SW ITCHBOARD &

1,557,992; PATENT orrics.

ASSIGNMENTS, TO

SUPPLY 00., A CORPORATION OF ILLINOIS;

AUTOMATIC TELEPHONE-EXCHANGE SYSTEM.

Application filed July 12, 1906. Serial No. 325,830.

To all whom it may concern.

Be it known that I, ALFRED H. DYSON, a citizen of the United States, and resident of Chicago, county of Cook, and State of Illinois, have invented new and useful Improvements in Automatic Telephone-Exchange Systems, of which the following is a specification.

My invention relates more particularly to a structure including the provision of party line service in connection with automatictelephone systems, but is in no sense limited by any such party line features. I have illustrated my invention in such a system employing a plurality of switches successively operated for completing each connection between callin subscribers lines and e called subscribers lmes.

As is well known, in commercial automatic systems of this character, subscribers lines are ordinarily'divided into groups of one hundred, each group having their line terminals multipled to bank'contacts 01, say, ten connectors each of which is capable of connecting with any line of the hundred group. The calling subscriber, by appro-' priate mechanism controlled from his substation, selects the group of connectors wanted, and, after a connector of that group has been automatically individualized to his line, operates the same to complete the de-' sired. connection. Thus in an exchange of ten thousand subscribers lines, there would be one hundred groups of one hundred lines, each group having its appropriate less numerous group of connectors. tion of ten connectors to one hundred lines is arbitrary.

For clearness of illustration, I shall assume my invention to be employed in an exchange of ten. thousand subscribers, sup

plied with four party line service. There would thus be twenty-five hundred individual lines, each having four stations connect-- ed'to it. j-- I For commercially satisfactory party line service, non-interfering selective, ringing is required, and one system of this character (that disclosed in patent to Wm. W Dean,

No. 779,533, dated January 10, 1905-, title, Party line telephone system) I shall refer to as employed in connection with my invention, though other systems may readily be employed.

This system operates upon the well-known The proporv1050. After the conclusion of principle of tuned bells responding separately to ringing currents of different pre determined frequency.

' In the system I have assumed, the ten thousand party line subscribers would be divided into groups of one hundred subscribers each and a particular group of connectors would be assigned to each group of subscribers. Each one hundred line group would include subscribers only whose substationbells respond to one particular frequency of ringing current.

Subscribers lines would still be arranged in groups of one hundred each having their terminals multipled to connector banks. Instead, however, of having one group of connectors capable of making connection with them, there would be four such groups of ten connectors each, the line terminals being multipled to forty connector contact banks. Each of the four groups of connectors have their ringing apparatus connected to a ringing machine of a different frequency, and current is projected over a called line of the frequency appropriate for ringing the bell of the substation wanted, without ringing the other bells on the line In general terms, for party line service, each groupoi one hundred subscribers is represented at the exchange by its own individual group of connectors, just as in single line systems; In making a call for subscriber 1050, whose number is in the group 1000l100, for instance, the calling subscriber wouldselect and employ a connector of the group appropriated to those numbers 10001100 and operate it to connect with line 50 of the line group. Ringing current of frequency #1, we will say, is now projected over the called line and rings bell the conversation, the lines are disconnected and the calling subscriber makes a second'call. Assume the wanted subscriber is number 1150 in the group 1100-1200. This may be considered a substation on the same line as 1050 just before called; The calling subscriber selects and employs a'connector of the group assigned to subscribers 1100-l200. This connector willhave access to terminals of the same lines as that emplo'yedi't'or connecting to 1050, and will be brought to connect with line 500i the same line group, i e., the same line. But this connector of group 1l00-1200 be projected over the called line and bell No. 1150 is now rung.

Having indicated in a general way the arrangement of apparatus employed n carrying out my invention, I will'nojv mention some of the problems more particularly involved in the provision of such serv ce.

As is well known, it is necessary, in order to prevent existing conversations from be ing interfered with, to arrange the structure of an automatic telephone system so that when lines are busy, other subscribers shall fail in endeavors to get into communication with them. Furthermore, a calling line is made to test busy soon after a call is indicated. This is moreover especially desirable in party line service, since, were it not so, while party A of a line is making his call, party B might be called up by some one else and the line taken away from A.

From these considerations arise the problem of enabling a calling subscriber to, connect a selected connector to his own line and ring out over that line to call a substation on the same line, without sacrificing the preferred method of operation whereby a calling line is made busy soon after a call is initiated, and held so until the calling or called subscriber releases it. In accordance with my invention, I provide mechanism for rendering the calling line busy after a subscriber initiates a call, and mechanism including means operated whenever connection is made with a called line, whether the same or another, for momentarily (and only so) removing the test potential from the connector bank contacts of the calling line. Thus in calling ones own line, the line will test idle at the moment the connector is to complete its circuit, while a call from any other line will find the line busy unless it chances to make co-incident; connection, a circumstance of necessarily rare occurence.

The ordinary practice has been in automatic telephone systems to release or destroy an existing connection by simultaneous grounding er the substation line limbs, accompli hed whenever the substation receiver is replaced on the hook, This will not do for party line service inasmuch as during a coniersation, a n -d1 party on either one or the connected lines,'whe might desire to make call and so remove his receiver, would, on hearing conversation proceeding, replaceh'js receiver, t-herebygrounding the two line limbs and disconnectingthe lines. To prevent this, I have arranged the structure of my invention in such manner that release is accomplished, after connection has been made, only when one of the connected lines has its circuit conductively broken, the arrangement being such that; when the circuit of either one of a connected line pair is opened, all switches employed in the connection are restored,

Until a connection is actually completed, however, the replacing of a receiver at any substation on a line will, by grounding the line limbs, release the switches. Thus no subscriber can, after partially making a call, leave his receiver off the hook and prevent other subscribers on his line from restoring the common apparatus to normal.

The general ob'ect of my invention is to provide an efficient and simple structure for supplying party line service in automatic telephone systems of the described character, embodying the advantages and combinations more particularly pointed out in the specific descriptions of the drawings and in the claims.

In the drawings, I have elected to illustrate my invention in combination with common battery automatic telephone systems, which systems, as well as the party line structures, are of my invention. I shall describe the party line system in connection with three such systems, differing principally in the manner whereby a first selector is brought into operative relation with the calling substations, it being understood that, in either system, are first selectors individual to telephone lines employed.

The first of these systems is one wherein each subscribers line is provided with a simple switch individual to it, operated on the removal of a substation receiver to select an indifferent idle first selector and place it under control of the telephone line.

The second system differs from the first in that no switches individual to subscribers lines are used. In this second system, first selectors are assigned, in groups of ten, to one hundred subscribers lines, which selectors are in permanent association, each with its own auxiliary switch, which I shall call a line selector. In accordance with this second system, when asubscriber at a calling substation removes his receiver, he operates a mechanism common to the group of one hundred lines among which hislinc is included, which starts an idl line selector in search of bank contacts ofdiis line, which appear in association with the line selector wipers. The line selector seeks these contacts cut and gagenrent with them, thereby placing an idle first selector in operative relation with the calling substation line Salient features of my invention, common to both systems, are the employment or a single pair ofrelays adapted for operation by directive currents transmitted from the substation, which relays control tl e operatlng magnets of the first selector, second selector and connector successively, thus doing away with relays for each switch. Another feature common to the two systems is a structure employed "for releasing the switches employed in the connection, its arrangement its wipers come to rest in en- (Lil being such that the release of all switches employed in a connection is accomplished when either subscriber of two connected lines replaces his receiver.

My invention includes also certain novel arrangements of substation calling apparatus arranged for employment in connection with the central office systems. As will be understood from the description of these, a time interval is required between the initial substation switching operation to cause the placing of a first selector in connection with a calling line and the time when the first set of directive switching impulses is to be sent and the calling device is especially arranged to secure such interval.

Referring to the drawings, Fig. 1 shows diagrammatically circuits embodying my invention; Fig. 2 shows a varying circuit structure; Fig. 3 shows a plan view of a line selector bank; Fig. at shows a modification of the structure of Fig. 2; Figs. 5, 6 and 7 show side and front views of line selector mechanism; Figs. 8, 9 and 10 show similar views of a connector mechanism; Fig. 11 is a sectional view of a line selector; Figs. 12 and 13 illustrate release and special switch mechanism of a first selector; Fig. 14 shows detail of a primary off-normal switch; Fig. 15 illustrates the special ringing mechanism of a connector; Fig. 16 winding mechanism thereof; Fig. 17 is starting mechanism; and Fig. 18 its circuit changing combination; Fig. 19 shows the circuit changing mechanism of special releasing mechanism for a first selector; Figs. 20 and 21 show front and side views of a private sw1 ch; Figs. 22 and 23 show slmilar views of a master switch;

Fig 2a is a front view of the calling device; r ig. 25 is a rear view thereof; Fig. 26 shows special governor mechanism for the device; Fig. 2? is a top view of the calling device; Fig. 28 is a view thereof on the sectional line indicated in Fig. 27; Fig. 29 shows the governor of the calling device; Fig. the friction member thereof; and Fig. 31 the receptacle of said member.

In Fig. 1, four substations A, B, C and D are indicated, station A being diagrammatically shown in full, B, C and D being indicated only by their branch conductors from limbs P and S. These are connected by the line limbs P and S with the private switch E at the exchange; Each substation includes the usual condenser and call-bell normally held in bridge of limbs P and S by hook lever A, the latter being adapted, on removal of the receiver, to place the bell in open circuit and connect the transmitter in metallic circuit with the line. The calling device 1 is provided, diagrammatically shown as a disk with teeth of insulating material, capable of clockwise rotation by the hand of the subscriber and adapted, when thereafter released, to be returned by the as sociated spring, its insulated teeth then operating upon spring 2 to connect limb P of the line to ground G intermittently a number of times, corresponding to the extent of rotation and the number of teeth thereby brougat beneath spring 2. After the last tooth of dial 1 has passed above 2, a tooth at the left of the dial closes momentarily limb S to ground C by operating spring 3, in its return t dial is in other than normal position, the pin thereon moving with it allows spring 1 by its tension to disengage spring 1', whereby limbs P and S are temporarily disunited during the substation switching operations. An arm 5, fastened to hook lever 1, moves over the top of spring 6 when the receiver is removed; and upon the subsequent replacing thereof, presses spring 6 to a position where it is connected with the two associate springs; and ground G is thereby temporarily applied to both line limbs P and S. As the hoolclever descends to normal, arm 5 passes over the top of spring 6 which then disengages its associate springs. Substations B, C and D have each equipment identical with that of A, as have also substations A, B, C and D at the right of Fig. l.

The exchange apparatus of Fig. 1 includes the private switch E, individual to the calling line and capable, when a call is initiated, of bringing an indifferent idle first selector under control of the calling line. The lines may conveniently be divided into groups of one hundred lines each, each line being provided with its private switch including the wipers 21, 24.- and 27, adapted to engage multipled terminals of an appro priate number of first selectors, say ten. A first selector circuit is shown at F. Its passive terminals 23, 26 and 29 are shown as multipled a single time, but it will be understood that they would in fact be multipled one hundred times, once to each private switch of the one hundred lines the selector is to serve.

There would be associated with wipers 21, 24 and 27, nine additional sets of contacts 28, 26 and 29, each leading to a difierent first selector.

The principal function of a first selector in a ten thousand line system is to respond to the thousands digit impulses transmit-- ted from the substation and move its wipers under their influence to a group of contacts associated with them and tiplicd terminals of longing to a vlimited group of subscribers, one thousand in number. As 'we have supposed an exchange of ten thousand subscribers, the wipers 63, 64: and 65 of first selector F would have accessible to them ten such groups of second selector terminals, one for eachone thousand subscribers in the exchange. The number 0 normal as shown. When the forming mulsecond selectors be of second selectors for each thousand group, appearing by their terminals at a first selector, is ordinarily ten, and a first selector contact bank may therefore comprise one hundred second selector terminals arranged in ten groups of ten each.

The group of second selectors of the appropriate one thousand having been selected, wipers 63, 64 and are caused to move over the terminals of the group, passing by terminals of busy switches and stopping in engagement with terminals of the first idle second selector.

The terminal contacts 78, 79 and 80 of second selector G are shown multipled a single time, but it is to be understood that they would in practice he multipled to a large number of first selectors, say one hundred.

The function of the second selector G is to respond to the hundreds digit impulses transmitted from the substation and move its wipers under their influence to an associated group of contacts forming ter1ninals of connectors belonging to a particular limited group of subscribers, one hundred in number. As a second selector is assigned to a particular one thousand subscribers, it has accessible to its wipers ten groups of connector terminals, one group for each one hundred subscribers of its thousand. A group of second selector bank contacts will ordinarily include terminals of ten connectors.

I have shown terminals 91, 93 and 95 of a connector H in Fig. 1 as multiplied a single time, but it will be understood that they will in fact be mutiplied to a large number of second selectors, ordinarily one hundred times.

The function of a connector H is to respond to the tens and units digit impulses transmitted from the substation and move its wipers under the influence of the tens digit impulses to a group of ten line terminals among which the line of the wanted subscriber is included, and thereafter under influence of the units digit impulses move the wipers into engagement with the terminals of the particular line with which the wanted subscribers substation is con nected.

The terminals 7, 8 and 9, shownat circuit I in Fig. 1, would in the four party line selective ringing system of my invention ordinarily be multi'ple'd to the contact banks of forty connectors, which, as indicated in the general statement of my invention, would be divided into four groups, the switches of each group connecting with the same one hundred sets of line terminals, but the connectors of each of the four groups being arranged to supply ringing current of a different frequency to whatever line one of them may be connected. to, for the purpose of ringing selectively the bell of one of the four substations on the line.

As the circuit features are the principal part of my invention, the mechanical features being subordinate thereto, 1 shall first describe Fig. 1; and for purposes of illustration, I shall assume that subscriber A desires to enter into conversation with subscriber D whose number is 2345 and whose bell is tuned to respond to current of frequency #4.

It is to be understood that all apparatus in Fig. 1 is shown at normal.

Subscriber A first removes his receiver, hook-lever 4 engaging its opposed contact and conductively uniting the line limbs P and S. This causes relay 13 to attract its armatures, circuit being traced from ground G through normal wiper contact 2524, upper armature of relay 15, over limb P, through hook-lever 4, returning over limb S, lower armature of relay 15, normal wiper contact 27-28, winding of relay 13 to bat tery 130.

The attracted left-hand armature of relay 13 is now connected to ground G and has closed circuit from said ground via right armature of relay 17, through vibratory magnet 14 to battery 130. Magnet 14 is thereby actuated and effects a forward offnorinal step of wipers 21, 24 and 27, the former, 21,, engaging permanently grounded contact 22 and establishing a locking path for current through the now attracted rightarmature of relay 18, the relay winding and to battery. Vipers 24 and 27 advance upon contacts 25 and 28 without disengaging them, ready to be moved to engage the first set of first selector contacts 23, 26, 29, on a second actuation of magnet 14.

The first movement of the wipers also caused off-normal switch springs 10 and 11 to disengage one another and to make contact with their respective opposed contacts. Spring 12 is also shifted to engage its alternate contact. The movement of spring 11 connects G with the multiple contacts 7 at the connector banks, alternating their potential to render them buy, while the movements of springs 10 and 12 complete circuit from G through relay 15 to battery, which relay, by attracting its arm'aturels, disconnects wipers 24 and 27 from limbs P and S so that the said wipers are in open circuit while passing over contacts 26, 29, of busy first selectors, in order to prevent interference with existing conversations.

Relay 13 continuing energized, magnet 14 vibrates its armature a second time, which moves Wipers 21, 24 and 27 to engage contacts 28, 26 and-29 of the first selector of the group. If this switch is idle, contact 23 is in the condition shown, insulated from ground. Viper 21 having left contact 22 and engaged open contact 28, circuit is broken through relay 13, Whose retracted left armtaure opens the circuit of magnet 14, preventing further actuation thereof and hence further movement of the wipers. The retracted left armature of relay 13 also causes relay 15 to be (ls-energized, whose armatures thereupon connect Wipers 24 and 27 with line limbs P and S.

The retracted right armature of relay 13 has now connected ground G through release magnet 16 with wiper 21 and contact 23 and all its multiples, to render the first selector busy.

Thus if it is supposed that a second private switch such as E is started by the removal of the receiver at its substation, wiper 21 of such switch, upon leaving its contact 22 to engage a multiple of contact 23 of Fig. 1, will find said contact grounded through magnet 16 at Gr of the private switch of A. Circuit will therefore be continued through relay 13 of this second private switch, its magnet 14 will again vibrate its armature, moving wipers 21, 24, 27 along to engage terminals 23, 26, 29 of the next first selector, when wiper 21 again tests the switch and the foregoing is repeated till an idle set of selector terminals is reached.

Release manget 16 is of relatively low efliciency and when placed in series with relay 13 of another private switch, as just described, does not attract its armatures, al though said relay l3 continues energized.

Subscriber A now operates dial 1 to transmit two current impulses from G, through spring 2, over limb P, upper armature of relay 15, contact 2 1-26, spring 30, its normal contact, upper armature of relay 3 1, through primary relay PR to battery. The twice attracted armature of PR causes t'ansmission of two current impulses from ground, through spring contact 5150, switch spring 55, primary magnet PM to battery. PM is thereby twice actuated and moves wipers 63, 6 1., 65 two steps to pro):- imity with a group of contacts such as 78, 79 and 80,"terminals of second selectors belonging to the second thousand group of subscribers.

lVith t 1e first primary step of wipers 63, 64-, 65, primary off-normal switch spring 57 engages its opposed contact, while spring is shifted to its alternate position.

Following the two impulses over limb P, a single impulse is transmitted from G, through spring 3, over limb S, traversing the lower armature of relay 15, contact 2729, spring 32 and its normal contact, lower armature of relay 34;, the winding of secondary relay SE to battery. The momentarily attracted armature of SR closes contacts 5152 and 5354. The closure of the latter completes a circuit from ground at switch E, through right winding of relay 17, right armature of relay 13,

contacts 2123, 5354 and to battery through resistance 35. Release magnet 16 at E is in a branch extending to this circuit, but due to its sluggi-shness and the presence of resistance 35, does not attract its armatures at this time. The 'armatures of relay 17 are attracted momentarily,armature 18' temporarily removing the busy groundfrom contact 7. Each time secondary relay SR is actuated by an impulse transmitted from the substation, this process is repeated. Thus for. four momentary periods during the establishment of a connection, once following the transmission of each set of digit impulses, a calling line has its guarding potential temporarily removed.

Returing now to the operation of switch F, the temporary closure of contact 5152 causes a current impulse from ground through said contact, spring 56, busy relay BR to battery 130. BR attracts its armatures, whereof 60, engaging its opposed contact, completes a circuit from ground G through spring 57, spring 58 and its opposed contact, armature 60 and its opposed contact, through secondary magnet SM to battery 130. SM being provided with a vibratory circuit attracts and releases its armature, moving wipers 63, 64. and (now on open circuit at contacts 59 and 62) to engage contacts 78, 79 and 80, terminals of the first second selector of the previously selectedgroup. If this switch is idle, then contact 78 is on open circuit, as shown at G, busy relay BR loses current, and armature 60 falls back to prevent a second actuation of secondary magnet SM and hence further movement of the wipers. The other armatures also fall back, whereof 60 places G7 in connection with wiper 63 and contact 78 and its multiples, via spring 57 and spring 58 and the latters opposed contact, to render the second selector busy.

W'ith the first (and in this case, the only) actuation of SM, secondary off-normal switch springs 55 and 56 are moved to disengage their normal contacts, cutting the primary magnet PM and the busy relay BR out of operative relation with the primary and secondary relays PR and SR.

Supposing,now, that a second first selector F is brought to engage multiples of contacts 78, 79 and 80. Viper 63 of this second switch will find ground from G of the selector Fig. 1 thereon; its busy relay BR will be locked by current from ground Gr of Fig. 1, to wiper 63 of the second switch, via the right armature of its release ma net RM and its normal contact; armature 61 and its opposed contact through BR to battery. All armatures of the busy relay of this second switch will therefore remain attracted, armature 60 continuing the vibratory circuit of secondary magnet SM'of this other switch, which will advance its wipers 63, 64., 65, to engage the next contacts of the group of second selector terminals. If this switch is idle, the busy relay will be demagnetized and the wipers arrested. If busy, however, another locking circuit will be established through the busy relay, its armatures will remain attracted, and successive vibrations of the armature of the secondary magnet will occur till wiper 63 reaches an idle terminal, when cir cuit through the busy relay of the second switch willbe broken and its armatures retracted.

Returning now to the calling subscriber at A, he next operates his dial to transmit from G, over limb P, current impulses corresponding in number to the hundreds digit of the called subscriber. These three impulses trave1se the winding of primary relay PR, following the before traced path. Three attractions and releases of the armature of PR transmit three impulses from ground through contact 51-50, armature 59 and its contact (contact 55 is now open), through (Mr-79 contact 82, the primary magnet PM of the second selector G to battery 131. Magnet PM, responsive to these three impulses, causes three movements of wipers .90, 92, 9 1, to bring them to proximity to a group of ten sets of'contacts 91, 93, 95, terminals of ten connectors, which connectors are provided with one hundred sets of bank contacts forming terminals of lines to which telephone substations of the two thousand three hundred group areconnected. The ringing connections of these connectors are all alike and extend from a ringing generator of such frequency as to be'capable of ringingthe bells of the one hundred substations numbered as above, only, the bells of such substations being properly attuned to respond to generator currents of this frequency, while the bells of other substations that may be connected to the same lines, will be incapable of responding to the particular frequency of the generator connected to said connectors.

The first actuation of PM at G also caused off-normal switch springs 81 and 88 to be shifted toengage their associate. contacts, while spring 89 is also shifted.

An impulse over limb S from G, following the third impulse over P, energizes secondary relay SR, and an impulse flows from ground, through contact 5152, contact 62, contact 80, contact 83, the busy relay BR at G to battery 131.

The busy relay BB is thereby energized and attracts its armatures, the attactio'n of completing circuit from ground, through spring 88, spring 89 and its opposed contact, attracted armature 85, through secondary magnet SM to battery. The resulting energization of SM moves wipers 90, 92 and 94 to engage contacts 91, 93 and 95, forming terminals of the first connector of the selected group. If this connector is idle, as shown at H, contact 91 is on open circuit; and at the cessation of the impulse through BR, the relay is de-energized and its armatures retracted. The retraction of 85 opens circuit through secondary magnet SM, pre venting further vibration of its armature, whereby wipers 90, 92 and 94 are left in engagement with contacts 91, 93 and 95 of H. The armature 85, in engaging its normal contact, connects ground Gr through springs 88 and 89, the armature 85 and the rightarmature of release magnet RM tocontact 91 and its multiples, rendering the connector busy. The first actuation of SM also actuates secondary ofi-normal switch springs 82 and 83 to disengage their associated contacts, thus cutting the'primary magnet and the busy relay out of operative. relation with contacts79 and 80. i

Supposing now that a second second-selector similar to G brings its wipers to engage multiples of contacts 91, 93 and 95. In such case, wiper of this second switch will find ground G connected to the multiple of contact 91 engaged by it; a locking path for the busy relay BR of the second switch will therefore be established via its wiper 90, its armature 86, through the busy relay to battery. The busy relay of this second switch will therefore continue to hold its armature 85 attracted and its secondary magnet SM will continue in circuit, vibrating its armature a second. time to move the wipers90, 92 and 94: of this second switch to engage a set of contacts forming terminals of a second connector of the group. If this is busy, a locking path similar to that just described will be produced for ER, and the secondary magnet SM of the second switch will continue vibratingits armature until its wipers 90, 92 and 9 t. reach terminals of an idle connector.

Subscriber A new transmits four impulses from ground G, over limb P, through primary relay PR, the four resulting actuations of said relay transmitting four current impulses from ground through contact 5150, contact 59, contact 04 79, contact 84:, contact 92-93, spring 90 at con nector H, armature 98, primary magnet PM to battery, causing four actuations of PMF. These actuations are effective to move wipers 124:, 126 and 127 of the connector to a position adjacent to a group of contact sets in the connector bank, forming terminals of lines 11, 1-2, 43. etc. to 19 followed by 40, of the one hundred line group to which the wipers have access. It will be remembered that forty substations are connected to these ten lines. With the first of the four primary movements of the wipers, off-normal switch spring 10% engages its associated contact.

The single impulse over limb S, following the four impulses over limb P, causes secondary relay SR to transmit an impulse of current from ground, through contact 5152, contact 62, contact 80, contacts 87, 91-95, through spring 97 and its normal contact, contact 100, secondary magnet Si to battery. The resulting actuation of SM causes wipers 124., 126 and 127 to ad: Vance step toward the group of connector bank contacts selected. The normal position of these wipers with respect to the edge of the contact bank is such that two steps are required to bring them to engage the first contact set of a selected group. This first actuation of SM? caused secondary off-normal switch spring 96 to be shifted into engagement with its opposed contact, while spring 97 is shifted to disengage its normal contact, but not to an extent to bring it into engagement with its opposed contact, this engagement occurring only with the second energization of Sly .1 The purpose of this delay is to prevent a possible actuation of test relay TR, which might otherwise be momentarily ctuated by the impulse now being transmitted from sec ondary relay SR if the operation of 97 were rapid enough to engage its opposed contact before the impulse ended. Such an unintended energization of TR would cause the attraction and release of its armature, effecting the shifting of spring 103, controlled by the said relay, which .would cause the calling subscriber to be connected with the line he now proceeds to select, Whether said line were busy or not, as will be apparent from the description of the testing operation hereinafter made.

Subscriber A new transmits five impulses from G, over limb P, through relay PR, Which in turn transmits five impulses over the previously traced path, through contact 92-93, the current now flowing through spring 96 and its opposed contact, through armature 105 and its normal contact, secondary magnet SM to battery. Five resulting actuations of the secondary magnet are effective to move wipers 124, 126 and 127 successively into engagement with the first, second, third, fourth and fifth contact sets of the selected group. The last of these is a set forming terminals of the line to which the telephone of the wanted subscriber #2345 is connected.

A single impulse, flowing over limb S at the conclusion of the last of the five impulses over limb P, by energizing the secondary relay SR, causes an impulse to be transmitted over the previously traced path to and through contact 9495, thence by spring 97 and its opposed contact, through armature 108 and its normal contact, the left winding of test relay TR to battery. The test relay attracts its annatures.

Assuming first that the called line is idle, which is' the condition illustrated at I of Fig. 1, contact 7 is connected to battery 131, through armature 18, spring 12 and the winding of relay 15. Armature 101 has connected the right winding of the test rclay tothe same pole of battery 131 and hence no locking path for the said relay TR exists; and on the cessation of the inipulse transmitted through its left winding, the relay TR is Clo-energized, its armatures 101 and 102 falling back. The de-energization of the relay TB is also effective to throw spring 103 to engage its alternate contact, whereupon current flows from ground G through relay 105, energizing the said relay, spring 103 and its opposed contact, contact 12 1- 7, armature 18, spring 12, relay 15 to battery, energizing also relay 15, whose attracted armatures disconnect the called line from the private switch and connect it to the terminal contacts 8 and 9,.

now engaged by wipers 126 and 127.

The connection of ground G by the shifting of spring 103, through wiper 124 to contact 7 and its multiples, has placed the called line in such condition that if it be now supposed that wiper 124.- of another connector is brought to engage contact 7, the ensuing energization of the'test relay of this other connector, by an impulse transmitted over limb S of the other calling line, will cause the test relay to be locked by a current flowing over a path that may be traced as follows: from ground G of the connector, Fig. 1, through its relay 105, its shifted spring 103, its wiper 124, through contact 7, thence to a multiple of said contact engaged by the Wiper 12a of the other connector now seeking connection with the called line, through the unshifted spring 103 of this other connector, through attracted armature 101" of its test relay TR to battery. This flow prevents the de-energization of the test relay on the cessation of the impulse through its left winding, its armature 102 continues attracted, and the busy signal is transmitted from machine 132 through armature 102, through spring 97 of the other connector and thence through the talking-circuit of the secondselector and the first-selector, there traversing condenser 133, through the receiver at the calling substation and back over limb P to battery,'notifying the subscriber that the line wanted is busy, whereupon he replaces his receiver and the apparatus he has used in attempting connection with the busy line is restored to normal, as hereinafter explained.

Returning now to the point where subscriberA brought the connector wipers to rest engaging contacts 7, 8, 9, of the line of D, the current flowing through relay 105 caused its armatures to be attracted. A

7 ground first result of this is the closing, by armatures 105 and 108, of two normally open contacts in the talking circuit about to be established. Armature 105 also connects 11 through contact 99, contact 106105", spring 96 and to the left via the upper talking conductor, through contact 59 at F, contact 50- 19, spring 31 and relay 3-1 to battery. Relay 34 is thereby actuated to bridge the battery 130 across the line of A via the windings of relay 36. The latter is therefore in turn actuated and its armatures are attracted, whereof 38 and 39 connect the relays windings with the calling line via springs and 13, while armature 40 completes circuit "from ground, through the armature of relay 16, to battery, actuating said relay. This re lay, on its subsequent de-energization, eti ected at the proper time as hereafter explained, releases the switches.

Returning to relay 105 at H, a further etl ect of its actuation at this time, caused by the attraction of armature 109, is the closure of circuit from ground, through said armature 109, spring 113 and magnet 116 of ringing device M to battery, energizing 116, a branch path of said circuit being also established through relay 115 energizing it.

The apparatus at M includes the notched disk 117 pivoted at its center, having fastened to it the circular rack 117 and cam 117". Toothed armature 118 of magnet 116 normally engages rack 117, holding the disk from rotation. Power is provided for the disk so that it continually ency to rotate in the direction of the arrow.

Magnet 116 having become energized as above described, armature 118 is attracted,

disk 117 is released and commences rota-' tion', spring120 immediately rising to ride upon the periphery of 117 and engaging spring 121, whereby ringing current of frequency #4, the same being. adapted to ring the bell at station D, is projected from the common generator 123, through contact 121120, the attracted upper armature of relay 115, contact 126-8, the attracted upper armature of relay 15, over limb P, through the bells of the substations of the line in parallel, returning over limb S, the lower attracted armature of relay 15, contact 9 127, the lower attracted armature ofrelay 115 and through the circuits of battery 131. As disk 117 completes a revolution, spring 120 rides down into a first notch to disengage spring 121. An instant later, it rides down into a second. and deeper notch in which position it closes contact 120122.

Assuming that at this time subscriber D, whose bell. alone was rung, has answered the call by removing his receiver. Instantly circuit is completed from ground G through the lower winding of relay 111,

through contact 122-120, upper armature release relay RR has a tendof relay 115, out over limb P, over the conductive path now established by the raised hook-lever at substation D, returning over limb S, the lower armature of 115 to battery. This current causes relay 111 to attract its armatures, 111 and 11 1 closingnormally open contacts in the connector talking conductors, while armature 112 contacts with spring 113 to lock its relay 111 by means of its upper winding and thereafter open the circuits of magnet 116 and relay 115, which become de-energized.

All this occurs instantly and while spring 120 continues in the deep notch of 117. The armature of magnet 116 would now be retracted, but is for a moment prevented by the detent ot' pivoted arm 119. This arm drops down oil from the raised portion ot cam 117 when disk 1.17 is first moved, and its pawl then engages armature 118, holding it against retraction.

hen now, under the present circumstances, disk 117 reaches the point of complete rotation (which it immediatel i does), arm 119 is lifted by cam 117 to release armature 118, which flies back and, engaging rack 117 stops the disk in the position shown, wherein spring 120 is in an intermediate position.

As soon as armatures 111 and 111 engage their associate contact-s, as before described, battery 131 was placed in bridge or" the line limbs P and S of subscriber D, through the windings of relay 110. The at tractedarmature of 110 opens the circuit before traced from ground G through relay 3 1, which relay is tie-energized, its armatures retracted, and springs 30, 81,-and 32, 33, are shifted to engage their opposed contacts. The shifting of springs 30"and 32 disconnect the windings of relays PR and SR and complete the talking circuit of first selector F. The shifting of spring 33 completes circuit from ground, through relay d1 to battery, and the armatures of said relay first engage springs 13 and 415 and then cause said springs to disengage their normal contacts. By this actuation of relay 11, the direction of the flow of current from battery 130 in the line of calling subscriber A is reversed.

The subscribers A and D are now in corn versation, the talking circuit being traced from station A to D, through the exchange by way of the heavily marked conductors, battery being fed to the line of A through the windings of relay 36 from 130, and to the line of D through the windings of relay 110 from battery 131.

The condensers c and c are in the two talking conductors at the connector and, owing to their presence, there is no flow of direct current through the windings of the relay 16. This relay is differentially wound, so as to ofier no material impedance to the rapidly alternating voice currents. The left lill whose retracted armature connects grouiul G through contact 99, contact 106105 spring 96 via the upper talking conductor to the left, the left-hand winding of relay 46, spring 30 and its opposed contact, contact 4-3-4-2, armature 39 and the lower winding of relay 36 to battery 130. Relay 16 attracts its armature,lopening circuit through release relay RE (which has been energized during conversation). Onits vde=energization, RR by its retracted armature eil'ects a thrust of pawl 66, and the said pawl having, on the energization of RR, been brought to engage a tooth o'tits associated rack adjacent to that shown en 'aeed b I it disk 67 is rotated one step so that spring 68 rests on the periphery of 67, in which position it engages its associate contact, closing circuit from ground, through spring .68 and magnet 69 to battery. Magnet 69, armature 70 and arm T1 of apparatus L have the same mechanical tunetions with respect to disk 72, its rack and cam, that magnet 116 at H, armature .118

and arm 119 have to disk 11?.

As reagent 69 is now energized, disk 72 is allowed to rotate. Immediately after its start, spring 73 engages 7st, closing circuit through'relay RR from ground, via spring 68 and contact 7374 to battery, again ener'gizing ER. Spring 73 then rides upon the periphery, opening contact 73-71, and RR becomes de-energized, pawl 66 causing disk 67 to'advance a second stepwhenspring 68 engages a tooth of 67 and is therefore at normal. The movement of spring 68 de-energizes magnet 69, but disk 72 completes its rotation because of the interlock between 71 and '70, only broken at the completion ota revolution when its breaking will cause disk 72 to be arrested at its normal position.

As disk 72 starts on its rotation, spring v76 rides to the periphery, closing contact 75-76. Circuit is thereby closed tt'romG at switch E, through release magnet 1(3,"-retracted armature of relay l3, contact21-23, terminal of spring 54, contact 76-75, release magnet RM to battery. As magnet 16 and magnet RM are both of low resistance, the branch circuit through the right winding of relay 17 is not edective, by its shunting effeet, to prevent the attraction of the armatures of magnet 16, and release magnets 16 and RM are both fully actuated.

The attraction of the right armature of RM completes circuit through release niagnet RM. at switch "G, the cnergiaation of RM in turn completing circuit through re lease magnet RM at the connector H. The described ene-rgizations of the tour release magnets prepare their respective switch mechanism for their returns to normal as soon as the magnet shall become de-energized.

In addition to the mechanical efl'ects produced, described hereafter in connection with the 'n'iechanical drawings, circuit changes are produced by each release magnet to disconnect its switchs wipers ant place them on open circuit while being re stored, so that their necessary wiping over busy contacts may not interfere with other connections.

Magnet 16 at switch E, when energized, shifts spring 132 to engage its normal contact. Spring 11, being an cit-normal switch spring, is not restored till switch E reaches normal. Hence spring '12 completes the circuit of relay 15, whose attracted armatures hold wipers 2 1 and 27 on open circuit durin the release.

RM a switch F. when energized, shifts spring 58 to nor1nal,'and, off-normal spring 5? remaining temporarily connected to (i clay BB is energized and disconnects wipers and 65, pending restoration.

tiiiniiarly, RM shiftsspring 89 to energize BR.

.fit connector H,1nagnet RM when energized, shifts spring 103 to normal which opens the circuit of relay 105, whose retracted armature 109 causes relay 111 to be de-energized, whose armatures are retracted. 111 and 114 disconnecting wipers 126 and 127.

Returning now to apparatus L at switch 1", the above operations are all performed in a very brief space of time and before disk 72 completes a revolution. 1V hen a revolution is completed, contact 75-76 is opened as shown, and release magnets 16 and RH are (lo-energized, the former restoring switch in; the latter restoring switch F, its retracted armature also shifting springs 30, 31, and 32, to normal. i Ioreover, the de-energization of RM opens circuit through RM, restoring the second selector (1 The de-energization of RM opens circuit through RM which thereuponrestores the connector H. and all apparatus is then at normal.

If subscriber A replaces his receiver in advance of subscriber D, circuit is opened through relay 36 at first selector F, whose armature 40 opens the circuit of relay RR and'the release operations proceed as before.

It will be remembered that springs and 32 are shifted from their normal positions only on the response at the called substation. Relays PR andSR therefore remain in circuit with the ailing line up to that time. Subscriber A, it he tails to ecure a re- 1's,;'. 1 SPODSQ (2P 'cllzillgCS 111; 11111111 lit-cl 111i lllf:

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