US1437356A - Electromechanical telephone system - Google Patents

Description

W. T. POWELL.

ELE'CTROMECHANICALTELEPHONE SYSTEM.

APPLICATION- FILED JAN-11.1919.

4:37, 356 o Patented Nov. 28, 1922.

INVENTOR ATTORNEY to the set of terminals in the connector switch conductors also connected as has been said,

- latter case there will be no response by the called-for party and no operation of the connector switch circuits of apparatus under the called subscribers substation control. ,However, the called line individual switch will not be caused to move tocause its wipers to make connection with the terminals of the outgoing or terminating trunk circuit leading "from the connector switch bank, and connection will only be made to a source of busy tone current, common to a plurality of line circuits, so that there. will be pro- 3 ected back through the circuits of the called line switch and through the circuits ofthe connector switch, as CN, and through the circuitsof the calling line switch L, back to the calling subscriber, the busy tone apprising the subscriber that the called-for line isbusy. I

If the present invention is used in asystem having only 100 lines, there will be 100 v line switches, such as L and M, one of which connectors, and other 10 contacts serve as is individual to each line. Each line switch is provided with 20 sets or" fixedcontacts, 10 of which serve as terminals for trunks leading to directly operated switches, such as terminals for incoming trunks which are employed when a line is called. Since 1t has been assumed that 10 per cent trunking is employed, there .will be 10 connector switches, each one of which has access to 100 terminals corresponding to the lines of the system. In the present arrangement the socalled talking contacts and test contacts are t not multipled between the several connector switches, only the so-called starting conductor, such as-63, being multipled between the 10 connector switches. Two of these multiple d connections from the starting conductor 63, are shown near the bottom of the drawing' It will be understood that the number of lines of the system as well as the number of the incoming and outgoing trunks and connector switches may be varied according to the sine and demands of the system, and that the mentioned numbers are merely used for purposes of description. 7

In order to facilitate a better understanding ofmy invention and the objects thereof, a description will now be had of the operation of the same made under the assumption, that it is the subscriber at the substation A that desires to make a call, and that a connection is desired with the subscriber at the substation B located upon a line having the line switch M, and the line number of which line is assumed to be #20.

The subscriber at substation A, upon removing his receiver r, closes an energizing circuit for the line relay LR of the line switch L as follows: ground at G, contact 1 of the cut-off relay CO, line conductor T, contact 2 of the substation hook switch, transmitter TR, receiver 7' calling device CD, line conductor R, contact 3 of the 'cut- 01f relay CO, winding of the line relay LE to the source of current.

The line relay LR operates and closes the following circuit: ground G, contact 1 of cut-off relay CO, contact 4 of line relay LR, winding ofstepping magnet ST, contact 5 of said stepping magnet, resistance coil RE to the source of current. Assuming the trunk upon which the wipers 6, 7, 8, 9 and 1.0 of line switch L are resting, to be busy, this above traced circuit will cause the stepping magnet ST to energize, break its own circuit at contact 5 and to then retract its armature. This causes the wipers 6, 7, 8, 9 and 10 to be stepped tothe second'row of terminals where nothing is found to cause the stepping magnet ST to remain deener-- gized, therefore it will continue to step the wipers forward until the fifth row of terminals is reached which are assumed to be the terminals of the first idle trunk tested by the line switch, L. Here the switch will be stopped because groundG'A will place a shunt around the stepping magnet winding 14, through the resistance of the winding 22 of the cut-otfrelay, CO which is low enough to prevent the stepping magnet ST from again operating. This circuit is traced as follows: ground GA of connector CN, contact 16 of relay IMP, contact 18 of relay BL, normally closed shaft contact 19, test trunk 20, which is multipled to a correspond ing contact of'all line switch banks of the group, terminal 15, wiper 6, contact 12 of relay LR, low resistance 22 of relay CO, contactZe of relay CO, to one side of the stepping magnet winding 14. The other side of the stepping magnet winding 14 has ground G on it as before traced. The stepping magnet winding 14 does not get sufficient current to energize its I armature, therefore the wipers 6, 7, S, 9 and 10 of line switch L remain on the trunk leading to connector CN. This same ground, GA, which was traced to the coil winding 14; also goes through contact 5 of stepping magnet ST, resistance coil REto the source of current. This circuit, which includes winding 22 of relay CO, causes the cut-off relay CO to operate and disconnect the line switch battery bridge from the calling line at contacts 1 and i The line conductor T is extended by way .winding of relay RL- to battery.

of contact 27 of relay CO, wiper10, terminal 28, trunk wire 29 and winding of 1mpedance @011 B to ground GB at connector CN. Line conductor R is extended by way of contact 30 of relay CO, Wiper 9, terminal 31', trunk-wire 32 and winding of impulse relay IMP to the source of current. The closed circuit of the substation A in addition to the above traced circuit causes the energization of relay IMP, which in turn operates relay RL over the following circuit: ground GA, contact 17 of relay IMP and The instant that relay IMP operates, this particular connector CN is made "busy to other call ing line switches like L because ground is taken off the test trunk 20 by the opening of contact 16. Ground will not again be placed on trunk 20 until disconnection is made. is kept off of trunkEZIO during the iinpulsing of relay IMP because of the fact that relay RL, which is slow releasing, holds its armature attracted, and maintains contact 18 opened while relay IMP vibrates its contacts. Upon disconnection this ground GA is not placed on trunk-20, to. cause this trunk to test idle, until the shaft of connector CN reachesnormal and closes oii normal contact 19.

When the relay C of line switch L operates, as previously described, it opens its own low winding 22 at contact 24 and closes its own high resistance winding 23 which looks itself over the following circuit ground GC, contact 33 of connector release magnet REL, holding trunk 34, terminal 35 and wiper 8 of line'switch L, high winding 23 0f relay CO, contact 21 of relay CO, contact of stepping magnet ST, resistance RE to the source of current. Theoperation of relay CO also disconnects the stepping magnet circuit ST from the trunk 36 of connector UN at contact 26 and places the common busy tone wire 37 on the trunk 36, through contact and condenser 38, for a purpose to be later described. The operation of the relay CU also allows line relay LE- to retract'its armatures by openingits circuit at contact 3. 7

Assume the number desired by the calling subscriber at substationA to be 20 and that number 20 is the substation shown at I3. The calling subscriber now operates his calling device for the first digit 2 of the called number, whereby the substation impulse springs (not shown but well understood) areoperated twice momentarily, each time bi'ea'lring'tlie circuit of the connector impulse relay IMP. The relay R-L of the connector being slow releasing does not deenergize during the momentary interruptions of its cirguit by the impulse relay IMP, and consequently each time the latter deenergizes, an impulse is transmitted through the primary magnet PM. This circuit extends from ground GA, contact 16 of relay IMP,

contact 39 of relay EL, winding of changecircuit for operating the magnet ESQ ex tends from ground GD, contact of relay CH, winding of magnet ESQ, resistance coil 46 to the source of current. After the last impulse is delivered, the relay CPI-releases and opens the circuit for magnet ESQ, which, upon deenergizing, permits the side switch wipers 40,47 and 48 to advance from first to second position. The movement of the side switch wiper 40 tronriirst to second position transfers the impulse circuit from the primary magnet PM to the secondary magnet SM. i

The calling subscriber now operates his calling device for the last digit 0, in response to which the connector impulse relay IMP operates to transmit ten impulses through the secondary magnet SM in series with the relay CPL-whereby the shaft wipers 41, 42, 43 and 44 are rotated onto the contacts of the desired line. The said circuit extends 'from ground GA, contact 16 of relay IMP, contact 39 of relay EL, winding of relay C'l-l, side switch wiper 40 and second position thereof, winding oi seeondary magnet SM to the source of current. The relay CH operates in response to the impulses for this digit in the same manner as for the previous digit to cause the escape magnet ESQ to advance the side switch wipers 40, 47 and 48 one more position, i. e., from second to third position.

By the engagement of the side switch wiper 48 with its third positioncontact point, a connection is completed for energizing the escape magnet as follows :ground GD, side switch wiper 48, and third position contact thereof, winding of magnet- ESC, resistance coil 46 to the source of current. This energizes the escape magnet but does not allow the side switch wipers to move away from the third position as they are advanced upon the release of the escape magnet. Side switch wiper 47 completes a circuit to cause the called line switch M to step around to a point on its bank corresponding to the connector CN which connected with it. i. e., the line switch M at this time will advance to the sixth row of contacts on its bank (of those shown) I wipers 49 and at which point called line switch wipers 49, 50, 51, 52 and 58 will rest on terminals 54, 55, 56, 57 and 58 respectively. As the connector wipers 41, 42, 43 and 44 are now resting on contacts 59, 60, 61 and 62 respectively, it will be seen that connection may now be established between calling substation A and called substation B. The circuit for causing line switch M to advance to the point associated with connector CN, as above described, is as follows: ground GE, low resistance impedance coil X, side switch 47 and third position thereof, connector wiper 44, terminal 62, trunk wire 63, contact 64 of relay 0C of called line switch M, winding 65 of stepping magnet TS, contact 66 of magnet TS, resistance coil PS to the source of current. This circuit causes the magnet TS to advance in the same man nor as described for the calling line switch L, .until the wipers reach the sixth row of terminals when they will be stopped by the following circuit :-ground GE, low resistance impedance coil X, contact 67 of relayTT, contact 68 of relay CL connector wiper 41, terminal 59, trunk wire 69, terminal 57 and wiper 52 of called line switch M, contact 70 of relay LE, low resistance winding 71 and contact 72 of relay 0G to one side of stepping magnet TS. The other side of TS also goes to ground GE as previously traced, therefore, as the stepping magnet TS is shunted by the low resistance winding 71 of relay ()0, it will not again operate. This above traced, circuit which went through winding 71 of relay QC, in addition to causing line switch M to stop on the sixth row of terminals, causes relay 0G to operate. Relay 06 looks over the following circuit :-ground PE, winding of impedance coil K, side switch wiper 47 and third position thereof, winding of relay TT, connector wiper 43, terminal 61, trunk wire 73. terminal 56 and wiper 51 of line switch M, high resistance winding 74 of relay 06, contact 75 of relay OC, contact- 66 of magnet ST, resistance coil RS to the source of current. This circuit causes relay TT to operate whose functionwill be later described.

Relay CO, in operating, removes the line switch M battery bridge from the called line by opening contacts '76 and 77. Relay 00 also extends the called line conductors V and W to the line wipers 41 and 42 of the connector CN by way of 50 of called line switch M. Relay QC also extends the common battery busy tone wire 3'7 by way ot'pondenser 78, contact 79 of relay 0G, trunk wire 63, con nector terminal 62, connector wiper 44 to side switch 47. The tone will not be heard by the calling party at this time because it is held disconnected from the calling line by contact 67 of relay TT.

called line switch M, line switch wiper 50, I

contact 82 of relay 06, called line conductor.

W, condenser is, ringer W1, hook switch contact S4, conductor V, contact 83 of relay OC, line switch wiper 49, terminal 54, trunk wire G9, terminal 59, connector wiper 41, contact 68 of relay CI, contact 85 of relay TT, re-

sistance coil 86, ground, ground GH, through the battery, common resistance COll 87 to the other side of the generator GN. Because of the low resistance coil 86 included in the re turn path for this signaling current, part of it will be forced through condenser 92, trunk wire 29, terminal 28, line switch wiper 10, contact 27 of relay CO, line conductor T, substation apparatus A, line conductor R, contact 30 of relay CO, line switch wiper 9, ter minal 31, trunk wire 32, winding of relay IMP, through the source of current to ground GL. This causes an audible signal to be given the calling subscriber, notifying him that the called partys line is being rung. Upon the response of the called subscriber at substation B, relay TP, which is included in the above traced signaling circuit, operates because of the closed path for direct cu1- rent which is formed by closing contact 88 at the hook switch. Relay TP, upon energiz ing, releases the escape magnet ESC, allowing side switch wipers 40, 47 and 48 to advance to the fourth position. This circuit is traced as follows :ground GG, contact 89 of relay TP to the side of the escape magnet ESQ which goes to the source of current through resistance coil 46. This short circuits magnet ESC and causes it to release.

Relay CI now energizes over the following circuit :ground GD, side switch wiper 48 and fourth position thereof, winding of relay CI to the source of current. In passing it may be said that this above circuit is also closed when side switch wiper 48 is in the second position thereby energizing relay 01. This is for the purpose of preventing ground, through low resistance impedance coil X, being extended by way of contact 67 of relay TT, contact 68 of relay G1 (which would otherwise be deenergized), connector wiper 41, a terminal like 59 being contacted with as wiper 41 advances over it, trunk wire 69, line switch terminal 57, wiper of some line switch like M resting unused at this point, contact 70 of relay LE, low resistance winding 71 of relay ()0, contact 72 of relay 0C, contact 66 of magnet TS, resistance coil RS to the source of current. If this could happen a relay DC of line switch M would be energized unnecessarily as a connector passes over a contact upon which the line switch was standing. By operating relay G1, which disconnects the low resistance path to ground this condition 'is avoided. The ground GF' through winding .90 of .coilfi'B is connected in this circuit but because of the hlgh resistance winding 90 of coil A'B being in series with the very low res stance winding 2'1 of (relay QG, the latter will not operate.

The called subscrifber now gets talking current as follows; ground GF windmg 90 of talking bridge coil'AB, connector wiper ll, terminal 59, trunk wire 69, l nesw1tc'h' termina]. 54;, line switch w per 49, contact 83 of rei lay QC, conductor VQsub tatiOn 'B, conductor VlQcontact 820i relay 06, line switch ,wipcr 50, terminal 55, trunk wire .81 termiualGOi connector wiper 42 contact '92 of relay (ll, winding 91 of coil A13 to the source or currentf: The calling subscriber gets talking,

currentthrougih relayIMP and battery feed coil "B the circuit or which was previously traced, The voice currents pass between the two through condensers 92 and 93.

I a "If the called "line switchM is busy when", the connector CN lands on the terminals associated with it, the connector sideswitch will advance to the third positionin the same manner as when calling anv idle line switch.v

' If the called lineswitch is busy either because of anoriginating or terminating call, its cut-off relay ()0 w ll be in ts energized ;positicn, therefore when connector side" switch wiper a7 reaches the third position, I

gthe' ground GE, which on a connection to an iidleline caused the line switch to step, will now find an open point atcontact Glofrelayf 106, and stepping magnet TS .of the called Iline switch M will not .be disturbed. The

calling subscriber will getthe busy tone as follows :ground "GKf'winding 94 of busy induction coil IND, busy tone interrupter BT, through the source of current to ground at .GJ. Thiscircuit induces a tone into, the

winding .95 of busy induction coil IND which is caused .to flow over the following circuit z ground G'IQwinding 95 of busyin- 'duction coilfIND, wire37 condenser .78,

t ct 5.0, new 169; ine s tc Wipe W .3 t unk 1 i i32, r lay IM .0 @0114 contact 79 of relay OC, trunk wire63, termina l62,;connectorwiper M side switch wiper Hand third position thereof, impedance coil to ground GE. Because off the high irnpedance of c 'il'X, part .of thls tone current ivillibe. forced'by way of contact 67 of relay cc ta tfi fofrclay .Cfiy i e c n u t I, su

st tion apparatus line conductor R, conhec or 9N, throug th ourc of ur to telephone at A, the calling subscriber will hear the busy tone. a

If the called line becomes idle while a connector CN is waiting on its terminals; the called line switch will immediately advance to the proper point when connection will be made as preyiousl-y described for a case where the called line .was not busy.

more than one connector is waiting on the terminals or" a line when it 'becomes idle, the called line switch can only connect with one of them (which will be the one corresponding [to the next nearest point onthe line switch bank) because the called line switch muststep to a different point on 1ts'bank for each connector which calls it and ,the lmeswitch wipers can only rest on oneset of terminals at a time.

After the conversation is completed, the connection is released, by the hang ng up of the call ng subscribers receiver, in the following manner: The .circuit for relay IMP is opened by contact 2' at the hook switch of 'substation A which allows relay ills [P to ,deenergizeand open the circuit for relay RL at contact 17. Relay RL, after short time, releases and closes a circuit from ground GA, contact 16 of relay IMP, contact 18 of relay BL, oil normal'contact -96, winding of release magnet REL .to the source of current. The magnet REL upon energizing. restores the. connector switch shaft and side switch to normal after which its own circuit is broken at off normal contact 96. The magnet REL, upon energizing alsoopensthe circuit leading to the winding '23 of the calling line switch out off relay CO. This circuit is opened at contact 33 or" magnet REL and allows the line switch out off relay GO to deenergize.

y The connector is now'in position to be again selected because there is agroundfiGA, through contact 16 of relay IMP, contact 118 of relay RL, 0E normal contact 19 on its test trunk 20.

Both the calling and the called line switches L andM remain where they were during conversation. until again used.

ilt will of course be understood that the lines having the substations A and B, may

u ua first s lect r, and i esi e se le t r swi h m hanism between h i Sw t es of a g up a dccnnect s tch such as UN, for a plurality of groups, that' t e ystem m y be m d of any size a fu lm y be had c the princip o n i hich re in ogu in th art a t .nr sent time y Vi tu 9 wh ch the ad a a s o such-t nking ci cu sin yhe ha a in a clit cn th dva tages of .my si j enid "9L- .Als th scir iut nc ud t er 431W be added ite a Q, as

In the embodiment illustrated, although the tirst'selector switch is notdescribed in detail, it is indicated by its switch wipers .connected to the conductors 29,32, 34 and 20, andwhich are shown in the drawing as e'n aging passive contacts of the connector switch, CH. lt Wllli be understood in the art how such engagementwill be controller by the calling switch mechanism, and no detailed description of such operation as maybe necessary to cause such engagement, will therefore herein be had. a

It will beunderstood, that if desired, the lines having the substations A and B may have common access by their respective line switches L and M to the same trunk circui't, such as the trunk circuit UN, for in 1 connector switch CN, may be multiply constance, in such a case the line switch sets o't contacts consistingct the contacts 28,-

Sl, 35,105 and 15 of the line switch L and which setof contacts are associated with the nected to the line switchset or contacts 28, 105 and 15 of the line switch M. Although I have. illustrated and described a specific embodiment of my invention for the purpose of imparting a clear under-% standing of the same, it will be understood that I am aware that numerous and extensive departures may be, made from the embodnnent illustrated without departing from the spirit or the invention, but what I claim as'my invention is defined in the followin claims:

1. n a telephone system, the combinae tion with a plurality of telephone lines. a

p urality of connector switches, calling line apparatus for directively controlling said connector switches means including a non.

'umerical switch to interconnect, a calling one ofthe said lines with an idle one of the said switches, a test wiper for the said con- .nector switch, passive contacts, one for each of the lines adapted to be engaged by the said test wiper, controlling apparatus for the said connector sw 1tches,a circuit for each of the lines leading to said contact for that line on each connector, switch, and means responsive to the continuity of the said circuit when the said test wiper engages a called line contact to extend atalking circuit from the calling line to the called line through the said connector switch.

closure of calling line circuit conductors to operate a calling line switch to connect with an idle one of the said selective switches through the calling contact set of the calla ing line switch, means under the control of calling line apparatus and connected selec tive switch to operate the calledline switch to cause'it to make connection with a called set of contacts of the called line switch, and means including wipers of said selective switch for interconnecting the said calling line switch calling contacts and said called line switch called contacts to extend a talking connection between the calling and called lines through all of .the'said switch contacts.

3. In a telephone trunking system, the combination with a plurality of telephone lines, line s vitches for the lines, active switch wipers for the line switches connected. to circuit conductors individual to the lines, successive sets of passive contacts for each of the line switches, some of the said sets being connected to circuit conductors leadto onetype of trunk circuit, other sets l; ,ing connected to circuit conductors leading to another type of trunk circuit, means responsive to a closure of the line conductors of a calling line to move the active switch wipers oi said calling line switch into engagement with a set oi contacts, whose connected circuit conductors lead to a trunk circuit of the first type, switching means responsive to the directive control of the call-v ing substation apparatus to completea conparatus to cause the said called line switch to advance its active switch wipers to make connection with the set or contacts connected to the trunk circuit of the second type with which thetrunk circuit apparatusof the said trunk circuit has made connection.

4;. In a telephone system, the combination with a plurality of telephone lines, substa-c tions for the said lines, a line relay for each of the lines in circuit with the line substation, a line switch for each of the lines, active switch contacts and passive switch contacts for the said line switch, propelling means for propelling the active switch contacts of line switch to cause them to make contact successively with different sets of passive switch contacts, the said passive contact set-s being in two groups, one group being incominc: contact sets, the other group being outgoing contact sets, astopping circuit for the said propelling means having two branches, one of the said branches being normally closed and the other of said branches being normally open, means responsive to the continued closure of the closed branch to cause the said active switch contacts to'be stopped when they engage the contacts of a par ticular trunk circuit associated with a given contact of one of the groups, and means responsive to the closure of the other branch and the opening of the first branch to cause tactso'f a line switch to cause them to make contact successively with-different sets of passive-switch contacts, the said passive contact sets being in two groups, one group being incoming' contact sets, the 'other group leeing outgoing contact sets, a "stopping circuit for the said propelling means having t wo branches, one 'of the said branches/being shimmy closed and the other of said branc'he's beingnormally-op'en, m'eans responf'srve 't'o the continued closure of the closed branch to cause the said active switch contacts to be stopped when theyv engage the contacts of a particular trunk circuit associated witha given contact of one of the groups, and means responsive to the closure of the 6therhranch-and the opening of the first branch to cause the said active contacts to stop when in engagement with the first engaged set of contacts of the other group, said line relay magnet for an associated line switch controlling the opening of one of the said branch circuits, and the closure of the other branch circuit.

6. In a telephone system, the combination with a plurality of telephones, a line relay for each of the lines, a cut-off relay for each line relay, a common source of busy tone current, a link circuit adapted to be connected with a calling line, a contact of the said link circuit adapted to make connection with a contact of a desired called line, and a busy tone circuit arranged to extend a connection between the said common source of busy tone current and the talking conductors of a calling line, including normally open contacts of the calling line cut-oftrelay, said link circuit contact, and said calling line lint: circuit connecting means.

7. In a telephone system, the combination with a plurality of telephone lines, substations for the said lines, line switches for the said lines, said line switches comprising a set of active switch wipers and sets of passive switch contacts adapted to be successively engaged by the movement of the said active switch wipers, means to move the said active switch wipers, the said passive sets of coin tacts comprising calling and called sets, means responsive to the connection of a sub station to a calling line circuit to cause the said switch wiper moving means to operate, a plurality of link circuits, incoming terminals and outgoing terminals for the said outgoing terminals of the diii link circuits,the incoming terminals and. the 'ent li-nk circuits hem connected todiil'erent. contact sets otthe dinerent line switches, means responsive to the electrical condition of an incomine contact of the set of contacts oi a given link circuit to s op the m :ent of a calling line switch-when its ctire switch contacts come into enpga neat with the said contact set, selective ,g means for the said erthe control of calling Subs to cause the movement of link circuit und station appara the called line s a itch active contacts, and controlling means associated with thesaid selective switching means to alter the electrical condition contact. of a set ot'contracts associated with the called line switch and with the said linlt circuit, which set of contacts is with reference to the said link circuit an outgoing set of contacts for the said called line switch, whereby the morement of the said called line switch is stopped when its active switch cont cts engage :the said outgoing contact set. I

in a telephone system, the combination with a plurality of telephone lines,v sub stations-tor the sai lines, line switches. for the said lines, said line switches comprisinga set ot QCi-lYQ switch wipers and sets of: passive switch contacts adapted to be successively engaged by the movement oi the said active switch wipers, means to move the said active switchwipers, the said passive sets of contacts comprising calling and called sets, means responsive to the connection of a substation to a calling line circuit, to cause the said si 1 wiper moving means to operate, a plurality of link circuits, incoming terminals and outgoing; terminals "for the said link circuits, the incoming, terminals and the outgoing terminals of the different link circuits being connected to different contact sets of the different line switches, means responsive to the electrical condition of an incon'iing contact of the set of contacts of a given link circuit. to stop the movement oi a calling line switch when its active switch contacts come into engagement with the said contact set, selective switching; means for the said linl: circuit under the control of calling substation apparatus to cause the movement of the called line switch act ve contacts, controlling means associated with the said selective switching means to alter the electrical condition oi a contact of a set or contacts associated with the called line switch and with the said link circuit, which set of contacts is with reference to the said link circuit an outgoing; set of contacts for the said called line'switch. whereby the movement of the said called line switch is stopped when its active switch contacts engage the said outgoing contact set and a calling circuit extended from the calling; line, through the said link circuit, through active contacts oi the calling and called line switches and passive incoming and outgoing contacts at the calling and called line switches respectively, for the said link circuit.

9. In a telephone system, the combination with a plurality of subscribers telephone lines, line switches for the lines, numerical switches adapted to be selected by a calling line switch, and means under the control of a numerical switch to cause the operation of a called line switch and a talking circuit established through contacts of the line switches of calling and called lines and ot said numerical switch.

10. In an automatic telephone system, a plurality of telephone lines, a single indi vidual line switch for each line, a numerical switch arranged for primary and secondary movements, outgoinglines from said numerical switch, means for causing the individual line switch of the calling line to seize said numerical switch, means to operate said numerical switch to seize an outgoing line, and means to cause the line switch oi the called telephone line to hunt forthe seized outgoing line, said calling and called line switches and said numerical switch bciug retained in the established connection.

11. In a telephone system, the combination with a plurality of subscribers telephone lines, line switches normally remaining in the position last used, and a nun'ierical switch adapted to be selected by a calling line switch, of means under the control of a numerical switch to cause the operation of a called line switch, and a talking circuit extending through the line switches of calling and called lines and said numerical switch.

12. ln a telephone system, the combination with a plurality of subscribers telephone lines, line switches for the lines, individual operating means for each 01 said line switches, and numerical switches adapted to be selected by calling line switch, of means under the control of a numerical switch to cause the operation of the line switch of the called line, and a talkingcircuit established through contacts of the line switches of calling and called lines and of said numerical switch.

In witness whereof, I hereunto subscribe my name this 9th day of Jan, A. D. 1919. VVINFRED T. .PONELL.

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