US1425728A - Telephone-exchange system - Google Patents

Description

H. G. WEBSTER.

TELEPHONE EXCHANGE SYSTEM.

APPLscATlor.' FILED MAR. 9l 1908.

Patented Aug. 15, 1922.

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H. G. WEBSTER.

VTELEPHNE EXCHANGi-SYSTEM. APPLICATION FILED IvIAII. 9, 190'8.

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H.- G. WEBSTER. TELEPHONE EXCHANGE SYSTEM.

APPLICATION FILED MAR. 9, 1908.

Patented Aug. 15., 1922. E

`I4 SHEETS-SHEET \4.

H. G. WEBSTER.

TELEPHONE EXCHANGE SYSTEM.

APPLiCATlON FILED MAR. 9, 1908.

1,425,728. Patented Aug. 15,1922.

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TELEPHONE EXCHANGE SYSTEM.

APPLICATION FILED MA-R. 9| |908..

Patented Aug. 15, 1922.

H. G. WEBSTER.

TELEPHONE EXCHANGE SYSTEM. APPLscATloN FILED MAR. 9, 190s.

1,425,728. l' PatentedAug. 15, 1922.

14 'sHEETs sHEET 1.

H. G. WEBSTER. l TELEPHONE EXCHANGE SYSTEIV..

APPLscATloN FILEDMAR. 9, 190s.

H. s. WEBSTER.

TELEPHONE EXCHANGE' SYSTEM.

APPLscATloN FILED MAR. 9, 190s.

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H. G. WEBSTER. TELEPHONE EXCHANGE SYSTEM.

APPLICATION FILED MAR. 9| 1908.

1,425,728. Patented Aug. 15,1922,

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TILEPHONE EXCHANGE SYSTM.

APPLlcATloN FILED MAR.9.1908.

1,425,728. Patented Aug. 15, 1922.

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TELEPHONE EXCHANGE SYSTEM.

APPLICATION FILED MAR. 9, 190B.

Patented Aug. 15, 1922.

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H. G. WEBSTER.

TELEPHONE EXCHANGE SYSTEM.

APPLxcATloN FILED MAR. 9. 190s.

1,425,728. Patented'Aug. 15, 1922.

14 SHEETS-SHEET 13.

H. G. WEBSTER.

TELEPHONE EXCHANGE SYSTEM.

APPLICATION FILED MARKS, 1908. E

1,425,728; PatentedAug. 15,1922.

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HARRY G. WEBSTER. CHICAGO. ILLINOIS, ASSIGNOR, BY MESNE ASSIGNMENTS, TO KELLOGG SWITCHBOARD & SUPPLY COMPANY, A CORPORATION F ILLINOIS.

TELEPHONE-EXCHANGE SYSTEM.

Application led March 9,

To all who/1L f may conce/w.'

Be it known that I, HARRY (i. ins'rma residing in Chicago, in the county' of Cook and State ot' Illinois. have invented new and useful Improvements in Telephone-Exchange Systems` of which the Afollowing is a specitication.

My invention relates to systems in which selective switches are employed in building up the connections from the calling subscribers lilies to the called subscribers` lines. and I employ, in organizing the system ot' my invention. selective switches divided into two general classes. First, what may be alled automat-ic switches which. when traveling. stop when engaging conductors of pre-determined electrical characters, no directive impulses being employed for their operation: while switches ot' the second. class have the conductors associated with them. arranged in different groups and are operated in response to directive impulses to select a group ot' conductors. whereat'ter they are automatically controlled to select contacts forming terminals of idle conductors.

Generally stated the object of my invention is to provide a telephone exchange system in which connections are built up with `the aid ot' operators at one central otlice who, by suitable calling devices. control the directive switches to complete the desired connections. and in such system' toprovide an organization of co-operating automatic. and directive switches ot' such character as t0 provide a relatively small number of switches and conductors.

A further object of my invention is to pro-l vide means whereby subscribers, whose lines terminate in exchanges at a distance from the exchange wherein the operators are located, may, by means of. two-wire trunks extending` from their exchanges to the, operators exchange. manifest calls at the operators positions; and the operators working out over the'same trunks over which the calls came in may adjust directive switches at the branch exchanges to connect the calling lines with any desired called lines and thereafter free the trunk lines for further use, thus securing a desirable economy in the use of the trunk lines.

Other objects of the invention are to se cure certain more specific improvements in the mechanism of the various switches employed and in the circuits by which their adexchange.

Specification of Letters Patent. Patented Aug', 15, 1922,

190s. seriai No. 419,981.

justment is secured, together with certain improvements to be more particularly pointed out in the specific description and in the claims.

In describing my invention, I. shall assume a telephone system embracing several different exchanges located, it may be. in different sections ot a large city, the 'exchanges being divided into two classes. First, a. class of main exchanges to which I shall refer as A exchanges, each such exchange embracing a. large number of subscribers lines. In the system as drawn out, the mechanism for each such A exchange is adapted for a maximum of 10,000 lines per Secondly, exchanges of a class which I shall designate B exchanges which may be branch exchanges having a relatively small number of subscribers each, the system as drawn out being arranged for a maximum of 1,000 subscribers per B ex- Y change.

rIhe various A and B exchanges being part of the same system, it is obvious that each subscriber must be enabled to secure connections to thesubscribers of his own main or A exchange and to the subscribers of each other main exchangeand also to the subscribers of each branch or B exchange. Similarly, the B exchange subscribers must have facilities for securing connections to the subscribers of each A exchange and each B exchange including subscribers of that B exchange in which their lines terminate.

In large telephone exchange systems of the character which I have indicated, it has been found that a relatively small number of calls from any exchange are for subscribers of the same exchange; in fact, in large cities, the percentage of trunking callsto the total number of calls handledvvill amount to eighty per cent and Will sometimes run as high as ninety per cent. In .these systems, with the ordinary methods of operation, each trunking call requires the services of two operators, one in the originating exchange and one in the exchange in which the called subscribers line terminates. It is apparent that in the operation of such an exchange, the employment of tWo operators nfor eighty or ninety per cent of the calls produces a very high charge for operators Wages and Will a so rende-r the completionl of connections relatively slovi7 and,

as has been demonstrated,vmuch more subject to error. thanin systems where but one operator is employed to complete eachgcon- .nection. From these considerations, I have deemed it advisable, in -organizing'the system of my invention, to arrange the structure so that each call, whether from the subscriber of an A exchange, or from the subscriberofa B exchange, will be extended tof of maintaining a widely scattered corps ofworkers.

As will hereafter more fully appear, the

l trunk lines, which are employed between exchanges, are in each case composed of but two wires each, whether they beemployed as incoming trunk lines oras outgoing trunk lines, and this is also true of the trunk lines extending from the B exchanges, each of which is capable of use as an incoming trunk line or as an out-going trunk line, as required.

Referring tothe drawing, I show diagrammatically in Fig. 1 an A subscribers substation connected with its line circuit at the exchange, together with circuits ofI an A line selector which makes connection with the line as a calling Aline, and the circuits of an A link selector which is joined to the line selector and seeks out and makes connection with ya two-Wire trunk leading to the operators `exchange. The incomlng trunks I have called A link trunks, and Fig. Qillustrates the circuits of one of these, Fig. 2a showing the circuit arrangements of an impulse transmitting device for use by the operator, while Fig. 2b is a plan view of the keyboard of the same. In Fig. 3 I have illustrated the circuits of a pair of A link connectors .which are automatic switches connected in parallel to an outgoing trunk line and serve, at the proper time, to connect a first selector, by means of an associated two-wire ` trunk comprising conductors 177 and 178, with the out-going terminals of the A linktrunk at the operators position. In Fig. 3a is shown an A link connector connected to a B first selector. In Fig. 4, is illustrated an A first selector which is operated responsive to directive impulses trans.

mitted from 'an operators position to select a group of trunks assigned for connection to the thousand lines among which the called line is included,l and then an idle trunk from a group, said A first selector corresponding circuits of one of said trunks.

to a certain extent to the first selectors known in purely automatic telephone systems. Fig. 4 illustrates a B first selector. Fig. 5 illustrates an A second selector adapted for operation after the adjustment of the A first selector to select a group and then an idle trunk therefrom assigned for connections tothe hundred out of the previously se* lected thousand among which the called subscribers line is located. In Fig. 6, are illus-Y trated circuits of a connector for selecting the tens and units of the called subscribers number, said circuits also comprising a party line switch for selectively ringing. the stations of a poly-station line. Fig. 7 illustrates a B second selector for use in selecting B link trunks-that is, out-going trunks to the B exchanges; Fig. 8 illustrating the Fig. 8a shows an operators link-circuit which I have designated the B cord trunk, together with the circuits controlling a call signal for indicating nin-coming calls from the B exchange subscribers, said B cord trunk being employed for receiving and completing the calls from B subscribers. In Fig. 9 Ihave illustrated the circuits of a B third selector located at a B exchange; and in Fig. 10 I have illustrated the circuits of a B line connector, also located at a B exchange. In Fig. 11 I have illustrated the modification of the circuits of an A first selector; Fig. 12 shows mechanism that may be employed for the selective switches, said figure being a top view thereof; and Fig. 13 is a detailed view showing the arrangement of the switch wipers upon the switch shaft. Fig. 14 shows the manner in which the figures are to be arranged for considering the operation of a connection from an A subscriber to an A subscriber; Fig. 15, the arrangement in which the figures are to be arranged in considering the connection from an A subscriber. to a B subscriber; Fig. 16, the arrangement of the figures for connecting a B subscriber to an A subscriber; Fig. 17, the arrangement for connecting a calling B subscriber in one B exchange to a called B subscriber in another B exchange; and Fig. 18, the arrangement for connecting a calling B subscri er in a certain B exchange with a B called subscriber in the same exchange. Fig. 19 is a skeleton view showing the general organization of the various mechanisms arranged in accordance with the invention, and Fi 20 a similar view of a connection from a subscriber to another B subscriber in the same exchange.

In organizing the system I have had in mind to reduce the operators work to a minimum in order that each operator may handle a maximum number 'of calls and the item of operators hire be correspondingly reduced. `Thus the operators who receive calls from A exchange subscribers are re-- quired only to ascertain the number of the subscriber desired and to thereupon press down a number of buttons of a keyboard associated with the A link trunk upon which the call is manifested, the depression of the buttons counting out the number` of the called-for subscriber. Thereafter the operator has nothing to do with the connection. The operation of' adjusting the various switches to make connection with the called line, the ringing of the called subscriber, the transmission -of the busy signal back to the calling subscriber if the called line be busy, and the restoration of the entire mechanism used in the connection being automatically Controlled without requiring any attention whatever from the operator.

In the case of the operators who handle calls originating in the B exchanges, the operator is required to insert a plug within a spring-jack of the B link trunk employed and then operate the proper buttons to count out the called subscribers number, and the operator is also required, at the proper time, to Withdrawl the answering plug she used.

Referring first to Fig. 19, the structural relation of the various switches will be more specifically referred to. At D 1 have indicated a calling subscriber-s station and line, said line being provided with passive multiple called terminals at the le-ft and passive multiple calling terminals at the right, said called terminals bei-ng preferably grouped together with those of ninety-nine other lines before the wipers of a suitable number of connectors, and said calling terminals being grouped together with those of ninetynine other lines before the wipers of a suitable number of A line selectors, which may number ten for each hundred lines. One of these 1 have indicated at E, and at G I have indicated a master-switch whichis effective, when a call is initiated over any line of the one hundred linegroup, to start an idle A line selector E to seek out the multiple calling terminals of the calling line and to rest in connection with them. The A line selector E has its A link selector Findividual to it, said A link selector being started simultaneously with the starting of the A line selector to seekout multiple terminals of an idle A link trunk leading to the operators eX- change.

It may be stated that, in Fig. 19, the automatic switches have been indicated by circles with the conventional wiper symbol attached, whi'e the directively operated switches have been indicated by squares with the wipers Symbols. In the said Fig. 19, the trunk lines for which two conductors only are required have been indicated by dotted lines.

The A link selector F may have before it the multiple contacts of one hundred A link trunks, which may extend to a number of operators positions vat the exchange. For

'sition begins to receive calls. Thus on the removal of the receiver at substation D, the

`A line selector, E, selects its line and the A link selector, F, selects a link circuit extending to an idle operators position; and when this connection is completed, a lamp associated with the A link trunk is displayed, and the operator inquires the number of the wanted subscriber. Each A link -trunk preferably has its individual impulse transmitting device which may consist of six rows of buttons, each row consisting of ten buttons, one for each of' the numbers from 1 to 9, and a button for the zero which is represented by ten impulses. The operator depresses one button ineach of the first live rows to count out the called-for subscribers 'number and then depresses a button in the sixth row which determines the exchange to which the A link trunk shall be extended and causes it to be connected over a twowire trunk of that exchange, whereafter the five previously depressed buttons control means for counting out the number of the called-for subscriber by sets of. current impulses which adjust selective switches at the distant exchange to complete the required connection.

Each out-going. A trunk is connected at its out-going end with anl A first selector N and at ,its answering end with an A link connector L, which latter has before it mul.- tiple terminals of one hundred A link trunks. Each A link trunk has multiple terminals K before a number of Avlink connectors L connected. to trunks extending to one distant exchange, a master-switch M being provided for the A link connectors L for one particular exchange, said masterswitch serving to start an idle A link connector to select multiple terminals of the A link trunk over which-a call is being extended. The A link trunk shown in Fig. 19 has, in addition to the` multiple terminals K which are selectable by a number of A link connectors L connected to A first selectors N of a second exchange, a masterswitch M being arranged to start an idle said A lilik connectors L2 will automatically seek out and connect with the terminals K2 ot' the A link trunk over which the call is being completed.

It is thus apparent that 'each A link Ltrunk has a. number of groups ot' multiple terminals K. K. K2. etc.. and it will have as many such groups 4as there are different exchanges. All of the said multiple terminals are normally unselectable by the A link connectors L. L and L2 respectively, having access to them, and the operator is enabled to render any group K or K or 1'2 selectable by its A link connectors. while leaving the other groups unselectable. For instance, to render the group K select-able` the operator may depress the button indicated at le., the depression of said button also operating the master-switch mechanism M to start an idle A link connector L to connectitstrunk to the terminals K. now rendered selectable, of'the A link trunk. The depression of key k, however. has no eifect upon the terminals K and K2 and they remain unselectable to their respective A link connectors. On the other hand. if the operator learns that the calling subscriber D desires to be connected with the line of a exchange, she will depress the button 71.2 and this will render the multiple contacts K2 selectable and will influ.

ence the master-switch mechanism B 2. associated with the switches L2, to start one of them which will seek out and connect with the terminal K2,` the A link trunk being thus connected'with. aB first selector N2 assigned for connection to the B exchanges. It is thus apparent that if the o )erator have ten buttonslzf, 71.2, h2, h4, etc.: slie may have access to ten groups of A link comie-ctors by means of their respective ten master-switches and may control distributively the selectable condition of ten groups of multiple terminals all belonging tothe same A link trunk. It will of course be understood that the master-switch mechanism M is not individual to a particular A link trunk` but that it is connected with branch wires to the but-- tons z. of one hundred A link trunks appearing before different operatorsthat is, to as many A link trunks as have multiple terminals before the master-switchs group of A link connectors.

Assuming thatthe calling subscriber D desires to be connected to subscriber D- namely, to a subscriber at a distant A exchange-the operator will depress the buttons as described, corresponding to the digits of the called number, the depression of button h. thereafter causing a switch L to connect with its set of contacts K, whereafter the transmission of the impulses will first adjust the A first selector N to select the thousand, the next set will adjust the second selector 0 to select the hundreds, the next set of impulses the connector .-P to select the tens, and the next set the same switch P to select-the units, whereafter the fifth set of impulses adjust the party line switch P to select the frequency of generator current to ring the called subscribers bell, whereafter the busy signal will betransmitted to substation D if the called line be`busy, or the bellof D rung if the called line be idle. Assuming the irst to be the case, subscriber D hearing the busy signal, replaces his receiver and his line and switches E, F, L, N, 0. P, P', are all restored to normal. s suming, however, that the called subscribers line is idle `and that he answersthe call, upon such answer the power to restore the switches P and P is taken froml the calling subscriber and turned t o the called subscriber so that when, at the conclusion of conversation, subscriber Dreplaces his receiver, the switches P and P will be restored` the other switches being restored when the calling subscriber hangs up.

Assuming, however, that the calling subscriber D desires to be connected with a subscriber in the B exchange, the operator would have depressed the button 11,2, thus causing a switch L2 to select the terminals K2, whereat'ter the first set of impulses would adjust the B first selector N2, which may have before it ten groups of multiple contacts of B second selectors R, the B second selectors of each group being assigned for connection to a dil-ferent group of ten B exchanges. Thus the B rst selector N2 is common for connection to a group of one hundred B exchanges and is operated directively to select a groupl of ten and then an idle second selector R out of the group of ten. The second selector R is adjusted by the second set of impulses to select one of ten groups of multiple terminals of B link trunks, those of each group extending to a different B exchange, and then an idle B link trunk out of the selected group so that the connection is extended over an idle B link trunk to the wanted B exchange. At the B exchange, each trunk terminates in a switch S which I have termed a B trunk controller and pair comprising a B third selector T and a B line connector U,the said switches T and U at the branch exchanges being arranged in pairs, tb the end to be hereinafter described.

It should be stated at this point that each third set of current impulses transmitted comprises one extra impulse-that is, .one impulse more than there are units in the digit to be transmitted. This extra impulse is for the purpose of operating the B trunk 'controller S, and the A line connection P is arranged to take care of this additional impulse, without producing a wrong selection, by its Wipers being set back so that two imist pulses are required before the said A line connector P selects its first group ofcontacts.

The extra impulse reaching the B trunkpulses operates upon the mechanism of the third selector T to select a group of contactsforming terminals of B line connectors U, assigned for connection to the hundred corresponding to the wanted number. The fourth and fifth sets of impulses adjust the B line connector U to engagement with the multiple terminals of the calledfor line, whereafter the busy signal to the calling subscriber, if the called line be busy, the ringing of the called-for subscriber, and the release of the mechanism, occur as in the previous case. It is there fore seen that when the connection is being extended to an A-called subscriber, the fifth or linal set of impulses is used to adjust a party-line generator selecting switch, whereas when connectionv is extended to a B called subscriber, the fifth s et is employed to adjust the connector itself.l This is believed to be a novel feature.

As before stated, the B exchanges are preferably arranged each for one thousand lines, and the switches thereat include two classes of directively operable switches, namely, B third selectors T, T', in Fig. 19, and B line connectors Il, U. The switches at the B exchange also include two classes of automatically operated switches-namely,

B trunk controllers S, S, and a number of master-switches u.

At the B exchanges the lines are arranged, by having their multiple terminals grouped together, in groups of one hundred, according to their numerical values, and each group of lines may have ten or more. B line connectors U, each of which will be capable of making connection with multiple terminals of any line of its appropriate group. There would thus be for4 one thousand lines ten groups of lines of one hundredeach and ten groups of ten or more line connectors, one for each group of lines. The said line connectors are arranged for a double use.

`They may beI either directively operated responsive to current impulses transmitted over B link trunks, of they may be automatically operated responsive to the removal of a receiver at a. B exchange substation to connect a B link trunk with a calling B exchange subsribers line. For starting the B line connectors, U, to connect with calling lines, the master-switch, u, one for each group of lines, is so arranged that upon the removal of the receiver, it will only start a B line connector, U, whose pairedB third selector, T, is at that time engaged by the B trunk controller, S, of an idle link trunk. When the B line connector has selected a calling B exchange line, the connection over the B link trunk exists by way of a link permanently uniting its B third selector,

T, With'the B line connector, U, through the B trunk controller S then engaging the terminals of switch, T, and over the trunk to the B cord trunk operators position, where a signal is displayed and the operator answers by means of a cord connector. As soon as a B line connector is started in its automatic search of a calling line, the multiple terminals of the'B link trunk, whose B trunk controller S is engaging the switch pair Whose switch, U, has started, are madel busy at the B second selectors R at the operators exchange so that the trunk is instantly guarded from seizure at the B second selectors. The call being extended to the B operators exchange, thc oprator thereat may find that the calling subscriber desires his line to be connected with an A exchange subscriber. Assuming this to be the case, the operator at the B cord trunk position actuates buttons of her lcalling .device for that cord to cause an A link selector L for the appropriate exchange to select multiple terminals of the B cord trunk W- with which she answered, and the call is extended via the switch, L, the A first selector, N, the second selector. O, the connector, P, and the party line switch, P', just as be fore. The B cord trunk is provided with .two supervisory signals,one controlled by the calling party and. one controlled by the called party. lVhen the called subscriber D2 replaces his receiver, the switches P and P will be restored; and when the calling B exchange subscriber V replaces his receiver, the B trunk controller S is movedof the switch T and the answering supervisory lamp is displayed. Both lamps being now displayed, the operator withdraws the plug. The switches L, N and O are all restored to normal.

In Fig. 20, it is asumed that a calling subscriber 7 in a B exchange has removed his receiver, whereon the B line connector U selected the multipled terminal of the line and the call was extended over the permanent link, associating switch U with switch T, to the B link trunk having the controller S then engaging switch T, and that the operator at the B cord'trunk W Vanswered the call and ascertained that the called subscriber belonged to the same B exchange to which the calling subscriber belonged. The operator at V thereupon connected her calling mechanism operatively with the answering end of her lcord trunk and actuated keys corresponding to the last three digits of the called subscribers number. She then depresses a special starting lector T and sweeps over its contacts, comingk called subscriber D2 will be automatically rung or the busy signal extended. Immediately following the last impulse adjusting the B line connector U', the B trunk controller S of the B link trunk which was used, "is moved 'off the terminals of the B third seto rest engaging terminals of a B third selector T of an idle switch pair T, U, the B link trunk being then ready to be used for calls from or to subscribers of its vB exchange. In Fig. 2O the talking circuit established from the calling subscriber, V is shown by the heavily marked conductors extending through the switch, U, over its by-path to the switch, T, thence to a multiple contact forming a terminal of the connector, U',

and thence to the called subscriber, D2. When this connection is established, it is seen that the switch, T', of the pair, T', U', is not employed in the connection at all. Neither can it be selected by a B link trunk controller, S. Moreover, if at the time the switch T attempted to select the switch U', a controller S- was resting on a terminal of the switch T', said switch T would he automatically moved away from the terminaly thereof in Search of an unconnected idle switch pair T, U.l Thus for a connection of this character, the trunk to the operators exchange is used `for a short time onlynamely, only long enough for the operator to receive the order and to transmit the directive impulses back over the trunk. The -two subscribers V and D2, on re lacing their receivers, cause the switches, T, and U to be restored to normal, and the switch pairs may then be selected by a B trunk controller, S.

It is apparent that in order to get Cthe fulluse out of the trunks, a sufficient number of switch pairs, T, U, must be provided so that each trunk controller S, when moved ot terminals of a busy switch pair, may viind terminals of an idle switch pair so that it f may come to rest engaging them and so be available for use. The' switch pairs T, U, will therefore exceed in number the number of B link trunks for the exchange. It will also be understood as being within the scope of the invention that switches of the general character of the B line connector, U, may

vbe provided without any individually asso- In developing the system, I have arranged for the use of rotary switches exclusively for both the automatic and directive switches, the wipers or movable contacts being designedto make a complete circular revolution from a normal point around 'to the same normal point when restoration is to be made, the rotary movement being 'thus always in the same direction. For the automatic switches, short steps of the wipers only are employed. Thus, assuming switches having one hundred contact sets arranged in a circle, the switch would comprise wipers mounted upon a rotary shaft, said shaft carrying a ratchet provided with one hundred and one teeth and a magnet controlling an actuating pawl for driving the ratchet, shaft and wipers. In such case, one hundred ratchet teeth would be employed-for adjusting the wipers to engage one hundred contact sets included in the switch, and the additional ratchet teeth above the one hundredwould be for the purpose of bringing the wipers into the additional normal position, said position being one between the first contact set of the switch and the one hundredth contact Set.

In the case of the direct-ively operated switches, which are designed to permit of the selection of ten groups of contact sets, each group comp-rising ten contact sets, the contacts are arranged circularly, and the wipers are mounted upon a rotary shaft as before, the so-called primary movements of the wipers to select the group! wanted being effected by long step-s, each long step causing the wipers to advance a distance corresponding to eleven short steps, the wipers for each long step thus wiping over ten sets of contacts to a position between the set wiped over and the succeeding set. To select an individual idle contact set out of a selected group, the wipers are caused to make short steps, each such step being one-eleventh as long as the group-selecting steps, and each such Short step `moves the wipers from one contact set of a group to the next contact set,

`moving continually until an idle set is selected.

For producing the long or group-selecting steps, one magnet is used, while for producing the short steps another magnet is employed. Both of these magnets are true driving magnets, and in no part of its operation is the switch actuated by a stored 'power controlled by escapements, although such method would be within the'scope of the invention. For the first selectors, second se-

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