US1541387A - Telephone system - Google Patents

Description

June 9, 1925. 1,541,387

L. POLINKOWSKY TELEPHONE SYSTEM Filed Jan, 5, 1925 2 Sheets-Sheet 1 i l l l I b 53 7/:

. TWHJr? a Fa/m/mws/ry' June 9, 1925. I 1,541,387 L. POLINKOWSKY TELEPHONE SYSTEM Filed Jan. 5, 1925 2 Sheets-Sheet 2 GOOOOOQODOGQOOOOOOOOO oooe'oooooooucooocoo ooooooooooeooc'oaoasob azgnmuuuu 0 0000000 12157415 111419-10 ooooooooo Patented alone 9, 1925.

warren stares PATENT OFFICE.

LIPA POLINKOWSKY, ornnTwEar, BELGIUM, ASSIGNOR T0 WESTERN, ELECTRIC,

COMPANY, INCOBPGRATED, OF NEW YORK, N. Y., A CORPORATION NEW YORK.

rrnnnrnonn SYSTEM.

Application filed January 5, 1923. Serial No. 610,752.

To all whom it may concern." v

Be it known that I, LIPA PoLrNKowsKY, a citizen of Russia, residing at Antwerp, Belgium, have invented certain new and useful Improvements in Telephone Systems, of which the following is a full, clear,concise, and exact description. v

This invent-ion relates to telephone exchange'systems and part-ic'ularlyto automatic telephone systems such as are employed for small private branch exchanges.

Heretofore such systems have either employed switches havingmovement in two directions or switches rotatable in one direction only over a bank of contacts. In those systems in which the switches have movement in two directions such switches are of a complicated construction and consequently expensive and liable to get out of order easily, while in those switches in which the brushes have movement in" one direction only, the brushes must be moved in response t a large number of operations ofthe dial switch of the calling subscriber to enable a 7 reasonable number oflines to be accessible to the switch.

It is the principal object of the present invention to provide an improved system of this character in which the apparatus em ployed may be of very simple construction and which may be operated under the control of an impulse transmitting devicein a simple manner to establish a connect-ion to one of a number of lines. i v

In accordance with this invention a telephone system comprises a selecting switch operable to extend a connection to one of a plurality of lines accessible thereto, said switch being operable for a digit 'of the designation of the' desired line under the control of the calling party and then to be moved automatically and independently of the calling party until a prod tcrmined position is reached depending upon the digil tiist called, the switch being movable from this position in responseto the remainder of the designation of the desired line to extend the connection thereto. Further, the switch may comprise a plurality of sets of brushes first digit.

during the call being determined by the digit first called.

In accordance with afurther feature of:

this invention a plurality of switching devices are arranged to be associated with the calling line, the particular switch taken into use during the call being determined by the digit first called, as is also the position from which this switch shallbe moved for the remainder of the designation of the desired line. i a

Incarrying this invention into effect the selecting switch preferably takes the form of a final selector switch adapted to extend connections directly to called subscribers lines and comprises a plurality of sets of line and test brushes adapted to be moved over a corresponding number of sets of contacts, by the operation of a stepping magnet. This magnet is adapted to receive impulses under the control of the usual line relay which is in turn controlled by the usual dial switch of the calling subscriber. Certain of the contacts engaged by the switch brushes are connected to certain controlling relays of the switch, so that upon the switch being operated for a particular tens digit representing'the first digit of the designation of the desired line,certain of these controlling relays are energizer.

After the switch has been moved in response to the impulses transmitted for the first digit, 'a circuit is closed for the stepping magnet independent of the control of theline relay, which circuit passes in series through contacts controlled by the magnet itself; ation of the controlling relays and causes the magnet to operate automatically to step the brushes quickly from the position to which they are set by the impulses representing the A sensitive relay is provided, the circuit of which is'controlled by the controlling relays and which extends over certa'inconta'cts in the switch bank, so that the relay is energized quickly immediately a particular one of these contacts is reached This circuit is closed by the o1 ersponse to the impulses representing the units" digit.

' In thepreferred form of the invention the connecting circuit terminates in two or-more final selectorswitches which are arranged in parallel each having its own stepplngy magnet and 1 sets of 1 brushes.

pulses for the first digit and-determines the energization of certain controlling re-- lays whichin turn determine the switch which shall be subsequently used in the extension'of the call and also the position from A particular switch 1S operated 1n response to the- 1m-* which said switch'shall be moved for the" remainder of the designation of the desired liner The dialing and busy' tones are preferably generated by a single apparatus consisting,

of a set of'relays which operate in succession to openandclo'se a circuiti'throu-gh windinn ofa t necoil to ene-rate a tone in the secondary winding thereof.

Ringing'currentuis also generatedby an apparatus consistlng of a setot relays and a ste J 'in 'inas nevooeratingzto ste a brush C D L L,

over a set. of contacts arranged in a circle to causean intermittent puls'atingelectromotiveforce to be generated-1n the secondary winding of the ringing transformer;

Theaccompanying drawingformed by" placing Fig. 2 to-the right-of Fig. 1, illustrates one form of'theinvention in which the connecting circuit terminates'in'a pair of final selector switches. modified form of subscribers circuit, usedin connectionwith a group of eqnivalentdines.

The invention is ofsuch' a-naturethat it-v Will bemore fully understood by a-desc-r1ption of thewoperation of the system. Upon the subscriber Lt-"SU-lZJSiJELtIOH T removing his receiver, the line relay 10 energizes in a circuit from battery, left hand winding ofrelay 10, 11 through the callingpartys stae tion and backthrough :11h right hand wind-. ing of relay 10 to cart-in The relay 10, upon Fig. 3 shows a is provided for the purpose of enabling the test relay 16 of the line finder switch LF to operate quickly in series with the cut-off relay. Relay 35, upon energizing, closes the circuits of the stepping magnets 36 of the line finder switches similaritothe line finder switchLF of the connectingcircuit' shown in the drawing. This circuit may be trace-d from battery 36, 36 35 3 1 16", to earth. Thestepping magnets thereupon-operateto 7 rotate the 'brushesa; b, c and'tl of the line find-erw switches with which they are associated over the contacts in their banks in search 1 ofthe-terminalsof the calling line, the stepping magnets automatically opening their own energizing-circuits at their contacts a" at'each energiz'ation. The brushes ofail free line:finder switcheshaving access'to the group of subscribers lines -of which the-calling line is one, thereforehunfl for the calling 3' line and-whnthe terminals-ofthe calling. line are found the test relay' energizes in a circuit Wl'iiehmay be. traced-from battery, left hand:windi'ngof the cut-oft relay- 11, 10, test terminal and brush 0, 39*, 341", winding; of test relay 16-, 35, resistance 1 to earth. The test-relay;16"together with the cuto-fi relay 11, operate-in this circuit. The test relay 16' opensat 1 its contact .7) the circuit before tracedfor the steppingmagnet36-so that the brushes of the line finder switch LF are brought to 'rest iir engagement wit-lithe cont-acts of the desired line.

Upon the closure-of the contact a of the testprela-y 16 the-resi-stance 1 is short-circuited-andnpon the closure of the contact a of thev cutoff relay 11, alocking circuit is provided for these twoa'clays from battery, ,bothwindings ofcutoff relay .11, 11, test terminalaand brush 0, 39, 3 1 16, 16 earth. The test relay is of low resistance and the short-circuiting of the resistance 1 at its con-tact a'causcsthepotential .upon the test terminal-to-be such a's to maintain the callingclinebusyagainst all other seeking line finder switches; The cutoff relay 11 upon energizing opens at its contacts 03 and f the circuit before tracedfor the line relay 10 so that this relay now deenergizes and 7 opens at its contact: a thecircuit for the relay '35. Thisrelay deenergizes and opens at its contacts a, the circuits of the stepping .magnets 5360f all the other hunting. line finder switches. The line relay 10 also opens at its contacta the circuit of the cut- 129 off relayll, butthe latter relay has locked up: as before describedat its contact a over a circuit including the test'relay 16'sothat energizing, closesat itscontact- 0 a circuit] for the relay35 from battery, 35, 10, earth. Relay 1O alsocloses-at its contact a a cirr cuit connecting the cut-off relay 11. to the test term-inalof the calling line. Connectedacross the. left-hand winding ofthe cut-oi? relay 11 is a non-inductive resistance which relay: 11 is maintained energized The relay 13'is normal-1yShort -circuited at the contact 5 of the test relay 16'so that as soonas. the test-relay 16 energizesand opens itscontact I), rel-ayj 13'energiz'es over a circuit in. series-with the winding of the stepping magnet 3'6"fro1nbattery, 36, 36 35 i- 34;", 13, earth, the winding of relay 13 being of sufiicient resistance to prevent the stepping magnet energizing in series therew th.

Relay 13 closes at its contact (6a locking circuitifor itself independently of the relay 34 and at its contacts 9 and Z connects the stepping relay 1 1 to the calling line so that battery is supplied to the line through the two windings to the stepping relay in series.

The relay 1a energizes in series with ,the

FSI, 30", normal tern'iinalengaged by brush of the second final selector switch FSII, 28 25 17, earth. Relay 17, upon energizing, closes atits contact 0 a circuitconnecting the test relay 16 to the test terminal independently of the relay 34, this circuit being traceable from brush 0 of LF, 39, 17, 16, 16, earth. At its contact a relay 17 prepares the circuit for the stepping magnet 37 of the first final selector switch FSI which circuit extends from battery, 37, 31 24, 17, 1e, 13, 23, to earth, this circuit being opened at this time at contact d of the relay ll and contact a of the relay 23.

The relay 19, upon energizing, closes a locking circuit for itself at its contact a through the relay 50 of the tone apparatus TA shown at the lower left-hand corner of the drawing. This circuit may be traced it'i'om battery, 50, right-hand winding of 19,

19, 26", 15, to earth. The relay 50, upon en j;

ing tone transmitted lfl'Olli the secondary ergizing, closes a circuit at its contact for the relay 51 of the tone circuit from battery, 51, 51*, contact. (6 of key 52, 50, earth. A circuit is also closed from battery through the primary winding of the tone coil 53,

contact bot key.52, 51 ,jcontact a of key 52,

50, to earth. The relay 51 energizes in the circuit previously traced and opens at its contact I) its own energizing circuit and the circuit before traced extending from the primary winding of the tone coil 53. Upon opening its contact I) the relay 51 deenerglass and will consequently again close itsv contact Z). ing through the primary winding of the tone coil 53 is intermittently broken and consequently an alternating electromotive force is generated in the secondary winding of the tone coil. The energization of the relay 19causes the closure of its contact a and c and this operation connects the sec-- ondary winding of the tone coil 53 to the calling line. The calling subscriber hears the tone in his receiver and is thereby informed that he may operate his dial switch in accordance with the first digit *of the called number.

In thisiiianner the current How The circuit traced through the relay 50 and contact e of relay 191naintains this relay energized. At its contact 9 relay 19 closes a circuit for the relay 3% which ex- 9 tends from battery, 19 resistance 60, 345,17,

The relays 34 and 19 are arranged to energize slowly so as to insure that the relay earth.

17 will close its front contacts before relay 3% opensits back contacts.

Upon the relay 3 ienergizing it closes a locking circuit for itseli' at its contact 0, this circuit being traceable from battery, 3e, resistance (30, 34, 17, to earth.

cuit to earth for the relay 1? which may be traced from one side of relay 1?, contact g of 34, 15, to earth. This short circuit is, however, maintained open at the contact 65 of the relay 15 which is maintained energized at contact a of the stepping relay'l l as long as the receiver of the calling party is oil this book. The relay 3e by opening its contact 7 opens the circuit-oi the left-hand operating winding of the relay 19 and by closing its contact 0, closes a circuit for the relay 23 from battery, 23, 34?, normal contact engaged by brush 9 or the final selector switch FST, 30", normal contact engaged by brush 5 of second final selector switch FSII, 28?, 255 1?, earth." The relay 23 upon energizing, closes at its contact a the inipulse circuit extending through the stepping magnet 37 ot' the first final selector switch.

FSl from battery, 37, 31, 24, .17, 1 1 13, 23, earth, his circuit being maintained open at the contact (Z of the stepping relay 11. a

Upon the calling party hearing the dialwinding to the tone coil 53 he operates his dial switch for thelirst digit of the called 'subscribers number. ihe first series of im with corresponding contacts in the bank of the switch. The position to which the brushes of this switch is set in. accordance with the first digit determ nes the closure of particular circuits determining the subsequent operation of the switch in a manner which will be hereinafter more "fully described. 7

Upon the calling subscriber releasing his dial switch the circuit of the stepping relay 14 is broken a number of times in accordance with the digit dialed and the circuit of the stepping magnet is closed from battery,

37, 31 24, 17, 14:, 13, 23 to earth, this circuit being closed at the contact (Z o1 the relay 1% at each deenergization of the relay. At each impulse the relay 14L opens its The relay 34 b t ClOSlILQ' its contact )10 ares a short cirticular set of contacts thereof in accordance with a number of impulses transmitted for the first digit of the called number. The relay 24 is constructed to operate quickly but to release its'arn'iature slowly so that it energizes immediately upon the first closure of the impulse circuit upon the deenergization of the relay 14 and-at its contact a closes a circuit for the relay 26 from battery, 26, 2 1, earth.

Relay 26, upon energizing, closes at its contact 0 a circuit for the relay 25 from battery, right-hand winding of relay 25, 26", to earth. Relay 25, upon energizing opens the connection from the calling line through the cord circuit'to the brushes of the final selector switches FSI, FSH, and at its contact f it disconnects the test brushes 9 and from the winding of the relay 17. Relay 26 upon energizing maintains the stepping circuit independently of the contact a of the relay 23, this circuit now being traceable from battery, 37 31 24:, 17, le 26, 15, to earth. At the end of the first series of impulses the stepping relay 14 remains de energized for a short period of time during which the calling party winds up his dial switch in accordance with the second digit of the called subscribers number and the relay 24cthereuponbecomes deenergized and opens at itscontact a the circuit of the relay 26 and this relay in turn opens at its contact 6 the circuit before traced for the relay 25 so that relays 26 and 25 now deenergize.

WVith the particular arrangement described the calling subscriber may dial any one of the digits 2, 3, 4, 5, 6,7, 8 and 9 as the first digit of the called partys line, the

digits 0 and 1 being reserved-for callsto.

the attendant as hereinafter described. The operation of the switch and the various controlling relays ei'iergized'in response to the dialing of the various first digits will now be described.

6" dialed (18' tons (li f it.

Upon the callingsubscriber transmitting the dig-it 6 as the first or tens digit of the scribed to move the brushes of the switch six steps into engagement with the'sixth set of-contacts in its bank. lVhen nowat the end of the series of impulses the relay 25 deenergizes in the manner before described a circuit is completed from battery, through the left -handwinding. ofthe relay .33, 18 25 28,brush f engaging the normal contactof the final selector F SH, brush f, of the first final selector switch FSI and the sixthcontact in the row of contacts over which it moves and into engagement with which contactit has been-moved by means of the'tens series of impulses, right-hand winding of relay 27, 26 'to earth. Relay 27 thereupon operates and closes at its contact 0 a locking'circuit for itself from battery, 34", resistance 60, 27, both windings of relay 27, 26", to earth. At its contact 9 relay 27 also closes a circuitfor the relay 18 from battery, 18, 20 27 15, to earth. The relay 18 thereupon energizes and closes a locking'circuit for itself at its contact 9 inclependently of relay 27 from battery, 18, 20 18 15, earth. 7 7

Relay 18 also closes a circuitfor the relay of the ringing apparatus shown at the right-hand'lower corner ofFig. 1 from battery, 10, 18, 25, 26, 23", to earth, but at contact a of relay 2? an energizing circuit is closed for relay 25 from battery, right-hand winding of 25, 27 to earth, so that the relay energizes and again opens the connection from the calling. line to the brushes of the first and second final selector switches'FSI and F5311 in the manner before described and prevents the relay 40 from energizing. A circuit is also closed at contact 6 of relay 2? for the stepping magnet 37 of'the final selector switch FSI from battery, 37, 31 37 38, 27 25, 26, 23" to earth. This circuit includes-contact 3' which is controlled by the magnet 37 so that the stepping magnet now operates automatically in the circuit described to step the brushes of the first final selector switch FSI automatically from the position to which they were set in response to the. tens digit into engagement with the eleventh set of contacts in the bank, which is the second normal set of contacts upon which the-brushes may come to rest, the magnet interrupting its own circuit at each step taken by opening contact a. Upon the eleventh set of contacts in the bank of the first final selector switch being reached, a circuit is closed for the quick operating sensitive relay 23 from battery, 23, eleventh contact engaged bybrush f/ of FSI, 30 first normal contact and brush of the second final selector switch FSH in normal position, 28 25 26, 27, to earth. The relay 23 operates immediately the brushes of the. final selector switch FSI reach the eleventh set of contacts and opens the circuit before traced for the stepping magnet 37 of this switch at its contact 6. The calling subscriber will'cause the brushes of the final selector switch FSI to be moved from the eleventh or second normal contacts by the P am transmission of the units impulses in the manner hereinafter to be fully described and as soon as the subscriber begins to transmit these impulses the relays 27 and 25 will deenergize.

7 dialed as tens digit.

Should the calling subscriber transmit the digit 7 as the tens digit these impulses will actuate the stepping magnet 37 of the first final selector switch FSIiu the manner be fore described and will cause the brushes of this switch to be moved into engagement with the seventh set of contacts in the bank. In this position circuits are closed to cause the relays 27, 25 and 18 to be energized in a manner similar to that before described when the digit 6 was dialed and the stepping magnet 37 will be automatically actuated so as to cause the brushes of the first final selector switch FSI to be moved from position 7 into engagement with the eleventh set of contacts in the bank. l/Vhen the final selector switch FSI is set to position 7 a circuit is also closed at the brush 6 for the relay 29 which may be traced from battery, right-hand winding of relay 29, contact 7, brush 0, normal contact and brush 6 of final selector switch FSII, 28, 25, 18 right-hand winding of 33 to earth. Relay 29 energizes and at its contact 0 closes a locking circuit for itself including the slow operating relay 28 from battery, 28, right-hand winding of 29, 29?,

15 to earth. The relay 29 is arranged to be quick acting so that it will operate before relays 27 and 25 operate while the relay 28 being slow to operate insures that :the' relay 27 will energize and close a locking circuit for itself before the relay 28 opens its back contacts. Relay 28, upon energizing, disconnects the brushes e f and of the second final selector switch FSII and the brushes 0, f and g of the first final selector switch FSI at its contacts h, d and f, respectively, and at its contacts a, c and c connects up the brushes 6 7, g of FSH and 0,, f, and g, of the final selector switch FSI. As, however, the brushes of the second final selector switch FSII remain in engagement with their normal contacts, the switch not being operated during this call, the brushes 0,, f, and g, are the brushes which are used in extending the connection to the line of the called party. It will, of course, be understood that all the brushes of the final selector switch FSI will be moved over their associated contacts but as the brushes 6, f and g are disconnected and the brushes 6,, f, and g, only connected to the talking circuit, the latter set of brushes are those which are used. In this particular instance the second final selector switch FSII remains inoperative with its brushes in engagement with their normal contacts throughout the call. The stepping magnet 37 of the final selector 'mal or eleventh contacts in the bank'and when these contacts are reached a circuit -is closed for the quick acting sensitive relay 23 from battery, 23, 32 eleventh contact in the bank engaged by brush normal contact and brush 9, of FSII, 28 25*, 26, 27 to earth. Relay 23 energizes innnediately the brushes reach the eleventh or second normal contact and opens in the manner before described the circuit of the stepping magnet 37 so that the brushes are brought to rest in engagement with the eleventh set of contacts. The switch FSI is now in a position to be moved by the units impulses as will be hereinafter described.

' 8 dialed as the tens digit.

Shouldthe calling party transmit 8 as the tens digit the brushes of the first final selector switch FSI will be moved 8 steps from normal into engagement with the eighth set ofcontacts in the bank of the switch. In this position a circuit is closed as when the switch was operated for the digit 7 for the relay 29 and this relaycloses at its contact 0 a locking circuit for itself including the slow operating relay 28 which also energizes. A circuit is also closed for the relay 32 which may be traced from battery, left-hand winding of 33, 18, 25", 28, f and normal contact engaged thereby, f and the eighth contact engaged thereby, left-hand winding of 32,26", earth. Relay 32 upon energizing closes a locking circuit from battery, 3%", resistance 60, 32 both windings of relay 32, 26 'to earth. Relay 32 upon energizing also closes acircuit for the relay 27 which may be traced from battery, 3%, resistance 60, 32, both windings of relay 27, 26", to earth. Relay 32 opens at its contact the circuit for the sensitive relay 23 which would otherwise exist to the. eleventh set of contacts in the bank of the switch. The stepping magnet 37 is now energized in a circuit from battery, 37, 31, 37 38 27 25, 26 23*, to earth, so that the brushes of the first final selector switch FSI are now moved from position 8 to which they were moved in response to the transmission of the tens digit of the called line. When the eleventh contacts are reached it will be remembered that the circuit of the relay 23 is now opened at the contact 7 of the relay 32 so that the brushes of the first final selector switch FSI are moved past the eleventh set of contacts and the stepping magnet 37 continues to operate to step the brushes of the switch on until the first normal set of contacts with which they are shown in engagement inthe drawings, is reached. In this position a circuit is closed for the sensitive relay 23 lit) from battery, 23,'normal contact engaged by brush 9 of F SI, normal contact and brush 9 of final selector switch FSII, 28*, 25 26 27, to earth. Relay 23 energizes immedi' ately the first normal contacts are reached 77 digit of the, desired partys number the ln'ushesof the first final selector switch PSI and opens at its contact Z) the circuit before traced for the stepping magnet 37 oi the first final selector switch so that the brushes brushes of the; first final selector switch FSI flbeing disconnected at contacts k,.d and fof and contact 9 engaged thereby, lefthand relay 28. The second final selector switch FSII remains in its normal position through out the call. r

.9" dia led as ten-s digit.

Should the calling subscriber transmit the digit 9 as the tens digit of the calledvsnb-r --scribers number the brushes of thefirst final selector switch FSI will be moved into engagement with the ninth set of terminals in .the :bank of the switch and in this position a circuit will-be closed for the relay 32 from battery,left-hand winding of 33, 18 25, 28%; and normal contact engagedthereby, f

' ofthe switch automatically into engagement with the-eleventh set er contacts the circuit of the 'relay23 is not closed in this position and the stepping magnet 37 operates to ro- .tate the brushes of the switch back into engagement with their first normal contacts with which they are shown in engagement in the drawings. l/Vhen this position is reached a circuit is closed for the relay 23 from battery, 23, 34?, normal contact engaged by brush 5 30?, normal contact engaged by brush 9 2 8, 25, 17, earth. The relay 23 immediately energizes and opens at its contact 6 the circuit for the stepping magnet 37 of the first final selector switch PS1. The brushes of this switch have thus been restored to normal position, from which position they are moved in response to the transmission oi? the units impulses, and as the relay 29- was not energized relay 28 remains deenergized and brushes 7 and g are connected to the talking circuit at contacts in d and f of the relay 28 so that these brushes are used in the extension of the call to the called partys line. The second final selector switch FSII remains inoperative throughout the call while the brushesc f, and g, of the first final selector switch remains,disconnected.

f2 dialed as (the tcns dz'git.

Upon the transmission oi 2 as the'first willbemovcd by the operation of thennignet 37 in the manner bet'ore described into engagement withthe second contacts in the banlg and at the end of this series-of impulses upon the deenergization of relay 25 a circuit is closed for the relays 31 and 23 from battery, 23, 32, lefthand winding of 31, second contact engaged by brush got the first final selector switch PSI, 30 normal contact engaged by brush g -of the second final selectorswitch F811, 28, 25, .17, to earth. A circuit is also closed'ifor therelay 27 from battery, left-hand winding of relay 33, 18 25 2 i, fflnormal contact engaged thereby, brush and second contact engagedthereby, right-hand winding of .27,

26, to earth. Relay 27 upon operating closes at its contact a a c1rcu1t for the relay '25 from battery, right-hand winding of relay 25, 27, to earth. At its contact 9 relay 27 also closesa circuit tor therelay 18 from battery, 18, 20 27$, 15 to earth. As the sensitive relay 23 is energized the circuit for the automatic operation of the stepping magnet .37 for moving the brushes of the first finalselector switch IFSI automatically from the position to which they'are set to the second, or on to the first normal contact is maintained open at contact Z) of the relay 23 so that the brushes now remain in engagement with the second seto'f contacts in their bank,

Relay 31 upon energizing closes a locking circuit for itself through its middle and right-hand windings trom battery, 3 1, 31, 31, to vearth and prepares a circuit -tor the relay'3O by opening a short circuit therearound at its contact The relay 31 also disconnects at its contact -d the stepping magnet 37 of the .first final selector switch FSI and closes at its contacto the circuit of the stepping magnet 38 of the second final selector switch FSTI, this circuit now being traceable from battery, 38, 31, 2 l, 17 9,71 9,

133 23 to earth, so that the units impulses of the called partys number will be transmitted to stepping magnet 38 and will oper ate the second final selector switch ESE inst ad of the first final selector switch Fill; As the relay 23 is deenergized the brushes f and g will be the brushes used in extend ing the connection to the desired subscribeus line and these brushes will remain in en gageinent with their first normal contacts, in which position they are shown in the drawings, until moved therefrom in response to the units impulses inthe manner hereinafter to be more fully descri'xd.

3 dialed as tens digit.

Should the called partys number comprise the digit 3 as the tens digit, the calling subscriber upon operating his dial switch in accordance with this digit will cause the brushes of the first final selector switch FSI to be removed from their normal position into engagement with the third contacts in the bank in the manner before described. In this position a circuit is closed for the middle winding of the relay 31 from battery, 3%, middle winding of relay 31, 32, contact 3 engaged by brush r of the first final selector switch PSI, 30 normal contact engaged by brush of the second final selector switch FSH, 28, 25, 17, earth. Relay 29 is also energized in a circuit from battery, right-hand winding of 29, contact 3 engaged by brush got the first final selector switch FSI, normal contact engaged by brush 6 of the second final selector switch FSII, 28 25, 18 right-hand winding of relay 33 to earth. Relay 29 closes a locking circuit for itself at its contact through the slow operating relay 28 from battery, 28, left-hand winding .of 29, 29, to earth.

' Relay 28' disconnects the brushes 0 f and g and c, 7 and g from the talking circuit. A circuit is also closed for the relay 27 from battery, left-hand winding of 33,182 28, 7' and normal contact engaged thereby, f and contact 3 engaged thereby, right-hand winding of relay 27, 26 to earth. A circuit is also closed for the relay 23 from battery, 23, 32, brush g and contact 3 engaged thereby, normal contact engaged by brush 28 252.17 to earth. relay 23 operates before relay 27 and opens the stepping circuit for the stepping magnet 37 so that the brushes of the first final selector switch FSI do not move from engagement with the third set of contacts in their bank and as the relay 28 is energized the brushes e and of the second final selector switch FSII are connected to the talking circuit so that these brushes are used in the extension of the call.

dtcded as the tens digit.

'Upon the calling subscriber operating his dial switch in accordance withthe digit 4 constituting the tens digit of the called numher the brushes of the first final selector switch FSI are moved into engagement with the fourth set of contacts in the bank of the switch and in this position a circuit is closed for the relay 31 which may be traced from battery, 3%", middle winding of relay 31, 32, contact 4c engaged by brush 9, of the switch FSI, normal contact engaged by brush of the second final selector switch FSII, 28 25 17, to earth. Relay 31 energizes and locks by closing its contact a. A circuit is also closedfor the relay 27 from battery, left-hand winding of Y 33, 18 25 28, brush f engaging the norofthe .first final selector switch FSI, righthand-winding of relay 27, 26 to earth. The relay 27 closes its contact 0 thereby locking itself directly to battery in a circuit from battery, 3 1-, resistance 60, 27 both windings of relay 27, 26 to earth. Relay 27 also closes at its contact (t a circuit for the relay 25 from battery, right-hand winding of 25, 27, to earth. The relay 25 thereupon energizes and opens the connection between the talking circuit and the brushes of the final selector switches. A circuit is also'closed for the relay 18 from battery, 18, 20 27 15, to earth. The operation of the relay 31 disconnects at its contact d the stepping magnet 37 of the first final selector switch F SI from the impulse circuit and substitutes therefor the stepping magnet 38 of the second final selector switch FSII. A circuit is now closed for the stepping magnet 38 from battery, 38, 31, 37 38 27 25,

26 23", to earth. This circuit it will be noted includes the self-interrupting contact a of the stepping magnet 38- so that this stepping magnet now operates automatically to f step the brushes of the second final selector switch FSII from their normal position in which they are shown in the drawing into engagement with the second normal or eleventh set of contacts in the bank. hen this second set of normal contacts is reached a circuit will be traced for the sensitive relay 23 from battery, 23, 32, second normal or eleventh contact engaged by'brush of FSI'I, 28 25 26, 27 to earth. The relay 23 immediately energizes upon the brush reaching the eleventh terminal and opens at its contact 6 the circuit of the etc 3 oin ma l b C!) net 38 so that the brushes of the final selector switch FSII are brought to rest in engagement with the eleventh set of contacts in the bank and from this set of terminals they are adapted to be moved in accordance with the units impulses in the manner hereinafter described.

5 dia led as tens digit.

.switch FSII. In addition a circuit is closed for the relay 29 from battery, right-hand 29, '15, to earth. The ielay 28 thereupon gized which determine:

energizes and disconnects at its contacts 71,

(Z and fthe brushes 7' and g of the second final selector switch FSH and the brushes 0, f and g of the first final selecto switch PSI and connects up the remaining brushes. A circuit is also closed for the relay 27 which may be traced from battery, left-hand winding of 33, 18 2 28, l andnormal contact engaged thereby, and the fifth contact engaged thereby, righthand winding of 27, 26, to earth. Relay 27 thereupon energizes and closes a locking circuit for itself from battery, 3%, resistance (30, 27, both windings of relay 2?, 26", to earth. Relay 2? at contact (t closes a circuit "for the relay 25 '.roin battery, righthand winding ot-relay It, to earth. A circuit is also closed for the relay 18 from battery, 18, 20, 27 15, earth. A circuit is thus closed for the stepping magnet 38 of the second final selector switch F311, from battery, 3s, ar, 37 se 27 26 23 to earth. This stepping magnet thereupon operates to rotate the brushes cf the second final selector switch FSII eleven steps from their first normalposition in which they are shown standing in the drawing into engagement with their second normal or eleventh set of contacts in the bank of the switch-and in this position a circuit is closed for the re-- lay 23 from battery, 23, 32, second normal or eleventh contact engaged by brush of FSH, 28 25*, 26 27, to earth. Relay 6 gages the eleventh contact antL opens at its contact Z) the circuit for the stepping magnet 38 so that brushes of the second final selector switch 'FSII are brought to rest in engagement with the second normal set of contacts in its bank and from this position the brushes are stepped in accordance with the units impulses in the manner hereinafter to be described.

It will thus be seen that in accordance with the first or tens digit of the called partys number the brushes of the first final selector switch FSI are moved by means 01 the stepping magnet 87 into engagement with a particular set of contacts in the bank of the switch depending upon the number of impulses transmitted for the first digit of the called number. In this position various circuits are closed and relays ener- (1) which switch shall be used in the extension of the connectionto the desired line, (2) which set of A3 energizes immediately the brush y en-' brushes of this selectedswitch shall be operatively connected to the talking circult and (3) the posit-ion trom-which thebrushes ofthe selected switch sh-all be moved iniresponse to the transmission of the units'snng pulses. In the toll wingtable these opertions will be 'madeclear:

Normal position Tens Final selector from which digit switch Brushes selected. brushes are dialed. selected. moved for units impulses.

ping magnet 38 depending upon whether' {the relay 31 hasbeenenergized or not-during the operation of the-switchFSI-ior the tens impulses. It therelay 31 is-energized steppinginagnet 37 is'disconnected at its-contact '(Z and the stepping magnet 38 substituted therefor atcontact c of relay 31. The-relay 1% will deenergize-a number of times in responseto the dialing of the unit's impulses and will close-atits contact (Z the impulse circuit extending through the particular stepping magnet connected by the relay 31. This may bejtraced from battery, either through the stepping magnet 37and contact 31 or step- pinganagnet3S andcontact 31, 24, 17, 14, 13, 23%?130 earth. The connected stepping magnetthereupon operates to rotate the brushesof either the'first or the second final selectorswitches, 'from the posi- 'tion in whichthese brushes stand,in accordance with the units impulses. Upon the first impulse transmitted relay 2% energize-s and closes a circuit-for the relay 26 from battery, .26, 243,.toearth. Relay26 thereupon energizes and closes at its contact 6 a circuit for the relay 25 from battery, righthand winding-of relay 25,26 to earth. At the endot the units impulses the relay El deenergizes and opens the circuit before traced for relay 26 which in turn-deenergizes and by closing its inake-beitore-brealt contact connectsthe'right-hand winding ot the relay 25 to the test brush to be used in extending the call. This circuit may be traced for example from battery, right-hand winding of 26 25 ,28 and normal contact engaged thereby, brush en- 13 gaging the test terminal of the called line.

lot)

If this line is found busy, that is, if it is engaged in a call either as a called or as a calling line the test terminal of the called line will be connected either to earth through to he maintained energized in a circuit from battery, right-hand winding of 25, 26, 25*, 28 9 normal contact engaged thereby, g, and test terminal of the called line engaged thereby, low resistance winding of relay 17 or 16 to earth according as the called line is busy as a called line or a calling line, respectively.

As the relays 23 and 27 are deenergized at the end of the units selecting operation, a circuit is closed, upon the deenergization of the relay 26, with the relay 25 energized, for the relay 21 from battery, winding of relay 21, contact 27, 25", 26*, 23 to earth. The relay 21 thereuponenergizes and closes a circuit from battery, both windings of relay 20,- 21, 22, to earth. Relay 2O energizes and opens at its contact cl the circuit of the relay 18 so that this relay deenergizes. The relay 20 also closes a locking circuit for the relay 25 from battery, both windings of 25, 20 15", to earth. At its contact a. the relay 20 closes a circuit for the relay 50 of the tone circuitand relay 19 of the connecting circuit from battery, 50, right-hand winding of 19, 20, 15, to earth. The relay 50 initiates the operation of the tone circuit shown at the left-hand lower corner of the drawing and this apparatus thereupon operates in the manner fully before described to generate a tone in the secondary winding of the tone coil 53. The energization of the relay 19 causes the secondary winding of the tone coil to be connected tothe talking circuit at contacts a and 0 of relay 19 so that the calling subscriber now hears the busy tone and knows that the called line is busy and will thereupon hang up his receiver and release the apparatus in the manner to be hereinafter described. It will be noted that the tone circuit is used for generating both the dialing and busy tones but no confusion will result from this as the busy tone when transmitted occurs after the impulses have been dialed while the dialing tone will reach the calling subscriber soon after he lifts his receiver.

Should the called line be found free, no potential is found upon the test terminal thereof to maintain the relay 25 energized so that this relay deenergizes and a circuit will thereupon be closed for the relay of the ringing circuit apparatus RA shown at the right-hand lower corner of the drawing, from battery, 40, 18 25, 26, 23", to

earth. The relay 4O initiates the operation of the ringing apparatus. TlHSOPGIRlZIOI'I being as follows: The closure o-fcontact- 0 of relay 40 closes a circuit for the relay 41, from battery, 41, 43 40 to earth. Relay 41 there-upon energizes and closes at. its contact 6' a circuit for the relay 42 from battery, 42, 41, 40, to earth. The relay 42 closes at its contact 0 a circuit for the relay 43 from battery, 43, 42, 40, to earth. Relay 43 upon energizing closes a locking circuit for itself from battery, 43, 43347, 40, to earth. The relay 43 also opens at its contact 6 the energizing circuit of the relay 41 so that this relay now deenergizes and opens the circuits of the relay 42 at its contact 0 so that this relay deenergizes and causes the circuit to be closed for the steping magnet 47 from battery, 47, 43 42 40, to earth. The stepping magnet upon energizing opens its contact a there-by opening the locking circuit of the relay 43 so that this relay deenergizes and opens at its contact g the circuit before traced for the stepping magnet 47 whereby the stepping magnet deenergizcs and steps the brush 47 one step from the position'in which it is shown into engagement with the next contact to the right thereof. Upon the relay 43 deenergizing, the circuit of the relay 41 is again closed and this relay causes the relays 42 and 43 to energize as before describedv and close the circuit of the stepping magnet 47. The relays 41, 42 and 43 are con structed so as to attract their armature slowly and in this manner by properly adjusting the time of operation of the relays the stepping magnet 47 may be caused to step its brush 47 b one step from one contact to another in its bank at definite intervals of time.

The relay 40 upon energizing also closes a. circuit for the relay 44 from battery, 44, one of the contacts connected thereto engaged by the brush 47 40, to earth. The relay 44, upon energizing closes at its contact a a circuit for the relay 45 from battery, 45, 46 44 to earth. Relay 45, upon energizing, closes at its contact a a circuit for the relay 46 from battery, 46, 45 44 to earth. The relay 46 upon energizing opens at its contact (Z the circuit of the relay 45 so that this relay there-upon deenergizes and opens at its contact a the circuit of the relay 46. This relay in turn deenergizes and again connects the relay 45 to the contact of the relay 44. Relays 44, 45 and 46 are arranged to operate slowly so that the contact a of the relay 45 is opened and closed at definite intervals of time. Upon the deenergization of the relay 45 it closes at its contact 6 a circuit through the relay 46 from battery, primary winding of the ringing transformer 48, 45 ,44 to earth so that current flows through this primary winding. lVhen this circuit is broken upon the energization of the relay 45 current flowing through the prin'iary winding of the transformer 48 is'interrupted and current is thereby induced in the secondary winding of the ringing transformer; This operation is repeated as long as the relay 44 is energized, that is, as long as the brush li' of the stepping magnet l? engages'acontact connected to this relay. As shown in the drawings the first four contacts are connected to'the relay and the brush 47 is then moved over its entire set of contacts until it returns to normal before the relay 4% is again ener-- gized. In'the actual switch the last contact in-the row of contacts shown as being-connected to the relay 4 1, is preferably adjacent the first contact upon which the brush isshown testing in the drawings, that is, the contacts are arranged in a circle. Further, the brush 47 is of such a width that: it engages the nextsuccessive contact during its movement over the-bank of contacts, before leaving the first contact, that is, the circuit of the relay i t is not broken during the time the brush 4 7 passes over from one contact to another of the contacts connected to the relay. In this manner an alternating electrOmotiveforce is gen-' erated in the secondary winding of the ringing current transformer 48, the frequency of the alternations depending upon' the 'rapidity of the operation of the relay 45 18 27 sccondar vwindin of the rin in transformer 48 to earth. This current passes through the bell at the called substation and actuates the same to attract the attention of the subscriber thereat and this subscriber upon lifting his receiver and completing a metallic loop through the substation causes direct current to'be superimposed upon the alternating current from battery connected to the left-hand winding of relay 20. The superimposition of this direct current will cause the relay '20 toenergize, this relay having remained inert during the transmission of alternating current therethrough. The relay QO-upon energizing, opens at its contact (Z the circuit'of the relay 18 so thatthis relay deenergizesand opens at its contacts 0 and e the circuit'before traced for the ringing current so that ringing is stopped immediately upon 1 the response of the wanted party whether he lifts his receiver during a silent or during a ringing period. By openingits contact 6 the relay 18 opens the circuit of the relay 20 so that thi relay deenergizes and the slow operatin relay 19 is prevented from energizing;

Connection has thus been extended to the called line and conversation may take place between the calling and called parties. Currentis supplied-to the calling party through windings of the relay 1% while the called party is supplied through windings of the relay 33'.-

Release of connection.

At the end of the conversation the release of the apparatus takes place under the control of the calling party in the following manne-rJ Upon the calling partyrestoring his receiver to the switch-hook the relay 14 deenergizes and opens the circuit of .the relay 15 so that this relay deenergizes after a-short interval of time. 7 Relay15, by closing itscontact (Z short circuits the relay 17 through contact 9 of the relay 3st so that the relay 1'? now deenergizes and opens the circuit of-the test relay 16 at its contact 0. Relay 16:deenergiz,es and at its contact I) short circuits the relay 13-so that'this relay there upon deen'ergizes' and opens the connection to the calling line so that the calling line will now test free. Rel-( 13, upon deenergizing, closes a circuit for the relay 32' from battery, 34, 13, 31 left-hand winding of relay 82, 26", to earth. Should the relay 31 have been energized during the establishment of the connection the relay 30 is included in the circuit-just traced as the short circuit therearound is openedrat contact 31 and this relay will also energize therein. Relay 32- upon energizing closes a circuit for the relay 27' from battery, 34;, resistance 6O, 32, both windings of relay 27, 26, to earth. Relay 2? energizes and closes at its contact a a circuit for the relay 25 fr in battery, right-hand winding of relay 25, 27 to earth. 7

Should the relay 31 have been energized during the call which indicates that the final selector switch F811 has been used in extending the connection, is necessary first to restore thisswitch to normal and then the final selector switch F81 from the position in which the latter switch has been set in response to the dialing of the tens digit. The energization of the relay 2? causes a circuitto be closed during the energization of the relay 31 for the stepping magnet 38 of the second tina'l selector switch FSII from battery. 38, 31 37, 38, 27 25, 28, 23, to earth. The stepping magnet thereupon operates automatically opening its own energizing circuit at each energiza tionat its contact a to rotate the brushes 1,541fss7 6 f 9 6 and g of the final selector switch FSII from the position in which they are set after the dialing of the units impulses back to their first normal position in which they are shown standing in the drawing. l/Vhen the first normal position is reached a circuit is closed for the relay 23 from battery, 23, 30 normal contact engaged by brush 9 of the final selector switch FSII 28 25 26 27 to earth. The relay 23 immediately energizes upon the brush 9 closing this circuit and opens at its contact b the circuit before traced for the stepping magnet 38 so that the second final selector switch is brought to rest with its brushes in engagement with the first normal set of contacts.

Upon the relay 23 closing its contact a the right-hand windings of the relay 31, that is, the locking circuit of this relay are shortcircuited, the earth connection being from earth, 23", 13, 30, to the middle and righthand windings of relay 31, the other side of these windings being connected to earth through contact a of the relay 31. The relay 31 thereupon deenergizes and at its contact o it opens the circuitof the stepping magnet 38 and at its contact (Z substitutes therefor the stepping magnet 37. The relay 31 by closing its contact short circuits the relay 30 and this relay thereupon deenergizes. The relay 30 upon closing its contact b connects the normal contact engaged by brush 9 of the second final selector switch FSII to the brush 9 of the final selector switch FSIF The'circuit of the relay 23 is also opened at the contact a of the relay 30 so that this relay thereupon deenergizes.

Under these conditions, a circuit is closed for the stepping magnet 37 of the first final selector switch FSI from battery, 37, 31, 37, 38, 27 25 26", 23 to earth. The stepping magnet 37 thereupon operates automatically opening its own energizing circuit at each energization at its contact a, to step the brushes, e, f, g, 6 f 9,, of the first final selector switch FSI from the position in which these brushes are resting back to their first normal position in which they are shown in the drawings and when this position is reached a circuit is closed for the relay 23 from battery, 23, 34 normal contact engaged by brush 9, 30 normal contact engaged by brush g 28, 25", 26 27 to earth, so that the relay 23 immediately energizes and opens at its contact 7) the circuit before traced for the stepping ing of relay 3 1, the other side of relay 34 being connected to earth through the winding of the relay 17. The'relay 3 L thereupon deenergizes and opens at its contact 0 the circuit of the relay 32 and this relay, upon deenergizing, opens the circuit before traced for the relay 27 at its contact 0 so that the apparatus is now completely restored to its normal position.

Operation of final selector switch as rotary connector.

It may be desirable to arrange that the final selector switch which establishes the connect-ion to the desired line operates as a rotary connector switch over certain groups of contacts, the contacts of thisgroup being the terminals of lines located, for example, in the same room or office and which lines would be numbered successively. Such an arrangement permits the final selector switch, upon engaging the first or subsequent terminal of the group except the last, and finding the same busy, to rotate automatically until an idle line in the group is found so that the connection is extended to one of these lines without delay. It is of course arranged that in any case, if the last line in the group is free or busy, the final selector switch will be brought to rest with its brushes in engagement with the terminals thereof. I To carry this out it is necessary to provide the slow acting relay 21 and marginal relay 22. The lines of the group over which the final selector switch is desired to hunt, with the exception of the last line in the group, will be provided with suitable indi vidual resistances as 2, connected between the cut-off relay of the line and the test terminal of the line in each of the connecting switches, and 3 between the cut-off and the test terminal of the line in the line finder switch. Such a line is shown at T Fig. 3. The operation of this arrangement will be as follows, it being assumed firstly that the final selector switch FSI has extended connection to an ordinary line, that is, a line which is not one of the group over whirh this switch hunts, and has found this line busy. The relay 25 will be maintained energized over the test brush of the switch in the manner hereinbefore described and a circuit is thereupon closed for the slow operating relay 21 from battery, 21, 27", 25, 26*, 23, to earth. The relay 21 closes at its contact a a circuit for the relay 22 and and at its contact 0 a circuit for the relay 20. As, however, the line to which the connection has been extended is assumed to be an ordinary line, the test relay 22 which is marginal does not receive sufiicient current to cause it to energize, it being shunted by the connection to earth through the low resistance winding of the test relay 16 of the line finder switch should the desired line be busy in another"co-nnection as a calling 'line or through the low resistar'ice' winding of the relay 17 ot the connectorswitch should the desired line be en,f ;a g -;ed as a calle'd'line. although its circuit is closed at the contact (a of relay 21 does not open its contact-fl so that a circuit is now closed from battery, both windings of relay 20, contact 21, 22, to earth. The relay 20, upon energizing, closes at its contact 6 a locking circuit for the relay 25 in the manner bet-ore described and also at its contacta a circuit for the relay 19 so that thebusy tone is nowtransmitted to the called subscribers line by the connection of the secondary winding oi the tone coil 53 to the calling line at contacts (a I and c of therelay 19.

If, however, the line to which the con-- nection has been extended and found busy is a non-final line of the group of lines over which the final selector switch hunts, the connection 01? the resistance between the cut-oft relay. and the test contact in the final selector switch or the line tinder, causesthe potential upon the test terminal to be suflicient to cause the relay 22 to energize in a circuit" which may be traced fromthe test terminal and test brush such as g of the first final selector switch l Sl, 30 first normal contact and brush g oi the second final selector switch FSII, 28221", 22,-2() to earth. The relay 22, upon closing its contact 0, closes an energizing circuit for the stepping magnet 37 inserics' withthe relay 24L and opens at its contact (Z the circuit for the relay 20. The relay is arranged to attract its armature slowly so that the relay 22 opens its contact it before the relay 20 has time to energize.

The circuit of the ste'pping'inagnet 37 may now be traced from battery, 87, 31, 2-1:, 22, to earth. The relay 2st energizes in this circuit and at its contact acloses a circuit of the relay 26 from battery, 26, 24, to earth. The relay 26, upon energizing, opens at its contact In the-circuit before traced tor therelay 21 so that this relay deenergizes and opens at its contact a the circuit of the relay22. Bela-y 22 by opening its contact 0, disconnects the stepping magnet 37 so that this stepping magnet now deenergizes and moves the brushes at the first final selector" switch FSI one step from the position 'to which they are set at the end of the units impulses into engagement with the next set of terminals in the group of terminals orer which the final selector switch hunts. that is. into engagement with the terminals of the next line.

lVhen the relay 22 decnergizes and opens atits contact e the circuit of the stepping magnet 31' the relay 2i deenergizes. This relay thereupon opens the circuit of the The relay 22-, therefore,

relay '26 at 'itscontaetu and relay 26 upon deenergizing closesits "contact h and again completes the circu'itof the relay 21-. The relay 21 closes" its contact a and again connects there-lay22 tothe'tes'tlbrush" 9 It now this second line,'int.o engagen'ient with the terminals 'ofiwhich the brushes of the final selector Su' itcli hai ebeenmoved by the" operation of the; stepping magnet 37 as described, should be-idle, the'relay 25 will deenergize and open at it's contact 0' the circuit of the relay 21 so that this rel'z'iky remains deenergized and maintains the cir cuit of the relay 22 open at contact 0. It will be remei'nbered 'that--the"relay 18 was energized at contact got relay 2? upon the latter energizing and relay 18 then loo red up over a circuit rromtattery, 18, 20 18 15, to earth. Upon the 'de'ene rgization of relay 25 therefore; 'a'circtiit is closed from battery, 4-0, or the iinging apparatus, 18',25 ,26,23 earth. The relayio initiates'the operation of the ringing apparatus and ringing current is transm'ittfed-tothe line from battery; 20, 18", 25", 28, f and normal contact engaged thereby," f if FSI- is used to extend the call; through tl'iebell at the substation, 0, e 28*, 25, 18", 27 throughthesecon dairy winding x of the ringing transformer 4-8 to earth. The bell of'tlie substation .is' rung and uponthe res onse; of the party thereat direct current is superimposed upon the ringing current 'and the "relay 20 energizes as before "eiiplaihed to'disconnec't the relay 18 atits conta et'd andthis relay then (lo-energizes to disconnect the ringing current andcon'i-plete the through bonnection to the calledline.

It the second line, into engagement with which the brushes of the fina'lseleetor swi'teh are moved is also busy, there-lay 27 remains energizechand the relays 21 and 22 then operate in the manner described tocause the stepping'niagnetto operate until an' idle line of the groi'ip is'reach'ed or, if all the lines are busy, until the terminals or; the last line in the group are'engaged. This line will not' be provided with resistance between the cutoff relay and the'testterminal and the relay 22, therefore, does not energize and the stepping magnet remains deenergiz'ed' so that the brushes of the tina'l selector switch are not movedfrom't-he terminals of the lastline' in 't-l'iejgroup." A circuit is also closed for the relay 20 front battery, both \i indings oi therel'a'y' 20, 21, 22. to earth. The relay 2O causes'the' busy tone to be applied to the calling'line as in the nranner hereinbet'ore fully described so that the calling party is informed that all'lines' of the group are busy;whereuponfhe will hang up his receiver and release the" apparatus.

In the system just "describedthe connecting circuitterminates in two final selector switches PSI and FSH connected in parallel and each final selector switch is provided with two sets oi brushes, a connection being extended over a particular set of brushes of a. particular final selector switch depending upon the first digit of the. called number dialed. It will be readily understood that this principal may be extended in any desired manner and if desired the connecting circuit may terminate in any number of final selector switches connected in parallel and these final selector switches may be provided with anydesircd number of sets of brushes. iVith such an arrangement the particular set of brushes and particular final selector switch F8 to be used in extending the call would be connected up by the energization of controlling relays,the circuits of which are closed at one of the final selector switches which is operated in response to the impulses representing the first digit of the called subscribers number.

Should, however, it be desired to provide a system for dealing with a smaller number of lines, the connecting circuit may terminate in a single selector switch 'such' as FSI whichmay be provided with any desired number of sets of brushes and the particular set of brushes to be used would be connected up by means of relays which would be energized over certain brushes of this switch when operated for the first digit of the called subscribers number. Such an arrangement would necessitate suppression of the relays 28 to 31, inclusive, from the system illustrated in the drawing, together with the final selector switch FSH and its associated stepping magnet 38..

Calls to the exchange.

It may be desired to give facilities to certain 03E thesubscribers to the system for extending connections to a main exchange either automatically or under the control of an attendant. For this purpose an attendants board would be provided and all subscribers lines which are to be given facilities for making such calls under the control of the attendant would terminate upon said board in a jack in addition. to terminating in the terminals of line finder switches and final selector switches while lines which may establish connections automatically terminate at the attendants position in terminals of trunking line finder switches in the manner to be hereinafter described. To extend a connection to theexchange a subscriber of the first category would remove his receiver whereupon a line finder, such as the line finder LF would hunt for the calling line and would associate a connecting circuit therewith. A calling subscriber would thereupon dial the digit 0 and would move the brushes of the first finalselector switch FSI ten steps into engagement with the contacts O. In this position a circuit is closed from battery, left-hand winding of relay 33, 18, 25*, 28, f and normal contact engaged thereby, brush f and tenth'contaot O engaged thereby, brush (Z 01": line finder switch LF and test contact of thecalling line engaged thereby, thence through a calling lamp associated with the jack, of the calling subscribers line upon the attendants board to earth. The relay 33 energizes and locks itself from battery, 33", contact 0, brush 6, normal contact and brush e 28*, 25 18 33, earth. The attendant upon observing the glowing of the lamp'plugs into the jack, throws her listening key and communicates with the calling subscriber. The calling subscriber will give the attendant the number she desires in the main exchange and the attendant will plug into a trunk jack of a trunk leading to the main exchange and communicate with the attendant thereat or establish the connection herself by the operation of her dial switch connected to thetrunk through the usual trunk dialing key.

For calls from themain exchange ringing current projected over the trunk line may be arranged to operate a ringing current relay which would cause a lamp associated with the trunk jack to be lit at the attendants board. The attendant would then plug into this ack, ascertain the number of the desired line and establish connection by plugging into the ack of the desired line located upon ,her board.

It may further be desired to permit certain subscribers of the private branch exchange to extend connections to the main exchange automatically and the lines of such subscribers would be connected to contacts in the banks of trunking line finder switches at the attendants position, similar to the line finder LF in addition to a jack thereat. The right-hand back contact 6 of the relay 33 is inthis case connected to the contact 0 engaged by the brush 9 of the final selector switch FSI, the test terminal cl in the bank of the line finder LF remain-. ing disconnected so that the relay 33 remains deenergized. The subscriber at the private branch exchange, upon dialing the digit 0 to obtain a connection to the main exchange causes the brushes of the first final selector switch FSI to be moved ten steps into engagement with the tenth set of contacts in the bank of the switch and a circuit is closed for a starting relay 80 at the attendants board which, upon energizing, is adapted to close the starting circuits of the trunking line finder switches, to cause these switches to hunt to connect an idle outgoing trunk line to the calling subscribers line. This circuit may be traced from battery, through the starting relay 80 at the attendants position, 33, contact 0' engaged by brush 9 of first final selector to select a particular one of said switches, a particular brush set, and aparticular normal position, and means responsive to a subsequent operation of said impulse trans niitter to move the selected brush set of the selected switch from the selected normal position to connect with said called line.

9. In a telephone exchange system, calling lines, called lines, a pair of switches each capable of completing connections, means forextending a connection from a calling line to said switches, means under the control of the calling line for placing one of said switches in any one of a plurality of predetermined positions, means responsive to the placing of said switch in certain positions to render said switch operative to complete the connection to the called line, means responsive to placing said switch in other positions to render the second switch of the pair operative to complete said connection, and means under the control of the calling line for completing the connection by means of the operative switch.

10. In a telephone exchange system, calling lines, called lines, a pair of switches each capable of completing connections and each provided with a pair of brush sets, means for extending a connection from a calling line to said switches, means under the control of the calling line for placing one of said switches in any one of a plurality of predetermined positions, means controlled in accordance with the position taken by said switch for rendering one of the brush sets of each switch effective, other means for rendering one of said switches eifective, and means under the control of the calling line For completing the connection through the brush set of the switch thus rendered et tective.

11. In a telephone exchange system, calling lines, called lines, a pair of switches each capable of completing connections and each having two normal positions, means for extending a calling line to said switches means under the control of the calling line for advancing one of said switches to any one of a plurality of predetermined positions to determine which switch shall be effective and from which normal position it shall be operated, means for positioning the predetermined switch in said normal position, and means under the control of the calling line for completing the connection.

12. In a telephone exchange system, calling lines, called lines, a pair of switches each capable of completing connections, each switch having two sets of brushes and two normal positions, means for extending a calling line to said switches, means to give one of said switches a preliminary setting, means operated in the set position of said switch to determine the normal position from which subsequent selections shall be made, means also operated in the set position of said switch to determine which switch shall be used in such subsequent selections, means for placing said switch in said normal position, and means for operating said switch from said normal position to complete the connection to the called line.

13. In a telephone exchange system, calling lines, called lines, a pair of switches each capable of completing connections, means for extending one of said calling lines to said switches, means to give one of said switches a preliminary setting, means controlled in accordance with said setting for either rendering the said switch operative or for holding said switch in its set position to render the second switch operative, and

means under the control of the calling line to cause the operative switch to complete the connection.

14. In a telephone exchange system, calling lines, a pair of switches each capable of completing connections, each provided with a pair of brush sets and each having a pair of normal positions, called lines arranged in groups such that each group is characterised by the switch, brush set and normal position used in completing connections thereto, means "for extending a calling line to said pair of switches, means under the control of said calling line for placing one of said switches in any one of a plurality of predetermined positions, means operative in accordance with such set position to select the group in which the called line appears, means to position the particular brush set of the particular switch in the particular nor mal position characteristic of the selected group ct called lines, and means under the control of the calling line for operating said particular switch to complete the connection to the called line.

In witness whereof, I hereunto subscribe my name this 12th day oi Decenllfier A. I).,-

LIPA POLINKOVVSKY.

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