US1579835A

US1579835A - Automatic telephone system

Info

Publication number: US1579835A
Application number: US467476A
Authority: US
Inventors: Winfred T Powell
Original assignee: STROMBERG CARLSON TELEPHONE
Current assignee: STROMBERG CARLSON TELEPHONE; STROMBERGCARLSON TELEPHONE MANUFACTURING Co
Priority date: 1921-05-06
Filing date: 1921-05-06
Publication date: 1926-04-06
Anticipated expiration: 1943-04-06

Description

w. T. POWELL AUTOMATIC TELEPHONE SYSTEM April 6, 192s.

Filed May e. 1921 3 Sheets-Sheel'l l .IOZW ur... wDlOumw INVENTOR www-RED T POWELL ATTORNEY April 6, 1926.

W. T. POWELL AUTOMATIC TELEPHONE SYSTEM Filed May 6. 1921 5 Sheets-Sheet 2 INVENTOR WINFBED 'n POWELL ATTO NEY A ril 6 1926.

p w. T. POWELL AUTOMATIC TELEPHONE SYSTEM Filed May 6. 1921 3 Sheets-Sheet I5 INVENTOR WIHFRED T. POWELL Patented pr. 6, 1926.:

` UNITED STATES,

PATENT orner..

WINTRED T. POWELL, or ROCHESTER, NEW Yonx, ynssieivon To THE STnoiviBEnG- CARLSON TELEPHONE MANUFACTURING COMPANY, F ROCHESTER, NEW YORK, Ai*

CORPORATION oF NEW YORK.

AUToMATIc TELEPHQNE SYSTEM.

Application led May 6,

To all 107mm t may concern.'

Be it known that I, VVINFRED T. POWELL,

l a citizen of the United States, residing at Rochester, in the county of Monroe and State of New York, have invented certain new and useful Improvements infAutoniatic Telephone Systems, of which the following is a full, clear, concise, and exact description.

This invention relates to telephone systems and more particularly to telephone systems employing automatic switches in establishing .telephone connections.

numerical switch was employed to connect a linejor trunk to a trunk, it was'necessary to provide a separate switch for each of said lines or trunks. This arrangement, While eliicie'nt in operation, is necessarily expensive because of the number of switches employed. v

' sented two separate line switches which are known as secondary line switches and function to further extend calling lines to idle Anumerical switches. At the extreme right of this ligure, there is indicated a connector switch anda wanted, Sub-station.-

Iii Figure 2 .the invention isapplied to what is commonly known as a call distributing system. At the left of the dotted line of Figure 2 thereA appears two incoming trunks which terminate` atY one end in the brushes of a Single primary line switch. The other end of each of these trunks terininates at a distant oiiice through which a calling line may be extended by automatic switches orby operators cord circuits at operators positions located thereat.V In the center of Figure 2 there appears two secondary line switches which function to extend a trunk circuit Selected by the primary line. switch to an idleiiuineii'cal switch which may be either a selector switch ory a connector switch depending on the sizeof v indicated. `In former telephone systems where a noni921'. semina. 467,476.

a wanted sub- .G0 'Figure 3 represents a modified form ot the invention shown in Fig. 1 and discloses' primary and secondary line switches, while at the extreme right of this figure an abbreviated disclosure of the connector switch is 'The line switches used iii this system may be of a structuresubstantially similar tov that disclosed in the patent to Clement 1,107,153 patented August 11, 1,914, while the mentioned selector and connector switcliesfniay be substantially similar to those disclosed in Patents 815,321aiid 815,176

A granted toKeith, Erickson andI-rickson on March13,1`906 `The line relayL.y It. and the n cut-cli' relays C. O. are arranged to be inteinr` locking as disclosed'in the patent to Lamb 1,193,160 granted August 1,` 1916. l

Uien this invention is yused in a system of the character disclosed in Figure 1 that is a ro-called full automatic telephone sys-` tem, the subscribers telephone lines may be is provided and therewill therefore be provided primary line switches for each group ctl00v linesf Each primary line For the kuse of eachv lswitch `will have access to 2O secondaryline switciies and these in turn will haveaccess to 10 numerical switches. These numericalv` switches may be first selectors ii, the system is large in size or connector switches iii'the system is relatively small.y It will be understood that the invention is not limited to this arrangement or to rthe number of lines or trunks individual to: a primary line switch. f y

It is` believed that the invention will best be understood by describing the method ot establishing a telephone connectionlrom a ca-lling sub-station'atiiyto a wanted station indicated at B. .Vhen the calling subscriber at A. removesk his receiver :troni its switch hook, aciicuitfis" vclosed for the line relay V42 extending from grounded battery, winding ot .this yline relay, inner, upper back Contact ,and armature otthe cut-soif relay 3 over the lower side of the calling subscribers line and through .the sub-statien circuits in series of the calling'sub-fstation, over .the uppery side of the calling line, uppermost armature and back contact of the cut-ott relay 3 to ground. The line Arelay 2 is energized in this circuit and closes an operating circuit for the motor mag-net 4 of the line switch Whichcircuit extends from grounded battery, Winding of the motor magnet, its armature and back contact, outermost front Contact and armature of the line relay 2' inner loire' back contact and armature ot the cut-oit relay 3 through `the test brush 5 and test terminals such as 6 of busy trunks to ground at the iii'ont contact .andi armature of Slo-u7 'releasingrelays such as 7. The motor magnet 4. thus advances the brushes 5, 8, y9, 10, '11, and 12 i-n -a rotary direction vuntil:thetet'brush 5 engages a test termi-nail which is characterized by the absence vot potential which indicates that the vtrunk which is indiyidualto this test terminal is idle.

Let it be assumed that the first idle trunk circuit tested by the primary line yswitch is that indicated i-n'iigure 1 yat, which time when 4the test brush `5 engages the test terni'inal 13 there will be no guarding potential on this test terminal due to the fact that relay 7 and relay 11i are not operated.

As a result of this condition, and since the line relay 2 has removed'the obstruct-ion from the path of the armature of the cutotl i'elay 3 it will be fully operated cin a circuit extending from ground, through its upperwinding, inner front contact and armature of the line relay 2 back contact, armature and winding ottheniotor magnet et, to grounded battery. The cut-ott relay 3 thus attracts its'armature and at its upper armatures opens the operating circuit of the line rela-y 2, but this relay is of the Vtype that is slew in releasing its armatures and therefore remains operated for a relatirely short interval. liet the upper armatures and liront contacts of the cut-oit relay 3, the callingr line is extended through the brushes S and 9 ot the primary line.l switch" to the select trunk circuit hy which acircuit is closed for energizing the slow releasing relay 7 from grounded battery Which is completer through both sides in series Aof the extended -connection including the calling line and trunk terminating at ground at the upper,- niost armature and back contact of `the relay 14.

The relay 7 is operated in this circuit to attract its armature and through its inner armature and contact 15, it applies a guard ing' potential to the test terminal 13 of Athe trunk that has` just been seized and also closes a circuit from ground through the .known manner. description to outline the operation ot'tliese armature :of relay 7 and its contact 15, test terminal 13, test brush 5, inner lower arniature and front contact of the cut-oitq relay 3 its lower winding to grounded battery. Under the control of this last described circuit the cutei rela-y is held operated during the period that the connection is mainu tained..

lVith the relay 7 operated a circuit is closed forthe motor magnet 16 of the secondary line switch Which is now associated with the calling line. This circuit is traceable iirom grounded ybatt-ery Winding ot the motor magnet 1'6, its back Contact and armature, outer armature and front Contact ot the lline relay 7, 'lower back contact and arn-iaturc ot' relay 14, test brush 17, and test terminal such as 18 of busy trunks. rl-his busy condition, as in the previous instance., Ais indicated by the presence ot ground. 'potential on the test terminals of busy Vtrunk circuits. Y Let it be assumed that the first idle; trunk circuit tested by the test brush 17' is that indicated in Figure 1, and when this test `takes place the relay 14 which has been shortcircuited, by ground applied through the test terminal 18 and test brush 17 is now operated in a circuit completed from grounded battery, 'Winding o" the motor magnet 16 its armature, and back contact Winding of the relay 14:, front contact 19 and armature of: the relay 7. to ground; The motor magnet 16 is not operated in this last `described circuit, but the relay 111 is operated to attract its armatures and thereby interrupts the operating circuit oi. the slow releasing relay 7 and also functions 4to further extend the calling line to the

brushes

24 and 25 of the selected secondary line switch and through the terminals ot the selected trunk Yto an impulse relay such as 22 associated with the numerical switcli ofthe trunk just seized.' fFlic impulse relay 22 of this last inen l suitch Will be operated over the ':ircuit indicated to attract its armature and close a circuit 'for actuating the slou' vi'1 relay. 23. This relay when operati .E apply aglioldiiig ground and guar-fling poten tial-tothe test terminal 1S hy Which the relay 1l will new be locked operatedin a circuit extending from grounded battery windingA oi the motor inagnet`16, its back contact, and armature, Winding oi the relay 14k louer front contact and armature of this relayY through the -test brush 17 and the test termina-l. 18 to ground as mentioned.

rlhe .calling subscriber at il. will now operate his dial to/transmit series ot impulses to actuate, the numerical switches such as the connector herein indicated to causethese switches to extend the connection to la called telephone line in the well It is Ynot necessary in this lif) lli

' relay terasse;

called line is testedand if found idle sig nailed. This portion of the system may operate in the manner disclosed in the men-.

tioned Lamb patent.y A

It will be noted that when Vthe primary line switch seizes the secondary line switch the brushes otl which-are indicated at 17, 24 and 25, brushes 11 and 12 of the primary line switch extend the line whose sub-station is indicated at D, to the secondary line switcn indicated at the lower portion otFigure 1 Thus whenever the subscriber at A. or D.

initiates a call, the non-numerical vswitch individual to these two lines, extends them to idle secondary line switches.

Let it now be assumed that, after the calling line kwhose sub-station is indicated at A. has been extended through an idle secondary line switch to an idle numerical switch, the

subscriber at D. now initiates a call. At the time when the receiver is removed from the switch hook at the sub-station at D the line relay 26 is energized over the two sidesA of the calling line in series in the manner that has been previously described in connection with the calling line A. Y lVith the line 26 energized ja lbrealr point, in the operating circuit of the motor magnet 4 lis closed but since the test brush 10 is now in engagement with the test terminal 4270i? a trunk leading to an idle sec-- ondary line switch, the motor magnet 4 will not be operated but the cut-oit relay 28 will be energized in a circuit from grounded battery winding of the motor magnet 4, inner armature and front contact of line relay 26 lower winding of the cut-oil' relay 28 to ground. The cut-oill rel-ay 28 when thus energized attracts its armatures and thereby opens the energizing circuit of the line relay 2G and extends the calling line D. to the brushes 11 and 12 of the primary line switchand thence through these brushes to the selected trunk leading to the idle secondary line switch. The extension of this circuit completes an energizing circuit for the relay 29 which attracts its armatures and closes a holding circuit for the cutsoi relay 28. This circuit is traceable from grounded battery upper winding of this relay, its

,tront contact and armature through the test brush 10,-test terminal 27,' contact 30 and armature of the relay 29 to ground. Under the control of this circuit, the cut-oli relay 23 is maintained operated during the connection. lVith relay 29 actuated a circuit completed for the motor magnet 31 of the secondary line switch closed from grounded battery winding of this motor magnet, its back contact and armature outer armature and front Contact of they slow releasing relay '29,- upper back contact and armature of relay 32 ,test brush 33 of the secondary line switch and` throughtest terminals such as 34 to ground at engaged trunk circuits leading to numerical switches.- Under the control of" this circuitthemotor magnet- 31 `advances the brushes 33. 35 and 36 ofthe secondary line switch until an idle trunk is located which will be indicated l by the absence or' ground potential on its test terminal 34. `When such a trunk is located, the relay 32 will bev operated in a circuit extending from grounded battery winding of the motor magnet 31, its back Contact and armature, winding of the relay 32, front contact 37 and armature ot relay 29 to ground. It will benoted that previous to the `.location of this idle trunk the relay 32 wasr short. circuited by ground on the test terminals ofbusy trunks so that it remained inactive. At this time, however, the relayr 32 is operated and extends the primary trunk circuit to the seized secondary trunk circuit at which time an impulse relay similar to 22 is energized and this in turn actuates a slow releasing relay similar to 23 which applies ground potential to the holding trunk. The

closure o1 this holding circuit locks the relay 32'in its actuated condition. The op- .erating of relay 32 ofcourse interrupts the energizing circuit of the relay 29 causing this relay to deenergize and remove the holding ground Ywhichhas been applied to the test terminal 27, but at this time a substitute holding ground is applied to the test terminal 27 through the test vbrush 33 and the test terminal such as 34 of the trunk that has been seized. j y

The apparatus and circuits are now in con; dition to,V receive the impulses :trom the dial of the calling. sub-station at D. Vand in re sponse to these impulses numerical switches are operated in the well known `manner to extend the calling line to the wanted station. The testing and the release voperations at these numerical switches will take place in the manner now well known.

At the termination` of the conversation when the calling subscriber at, station A. replaces his receiver on its switch hook the impulse relay 22 of the iinal numerical switch will deenergize and shortly afterwards this will eiect the deenergization of the slow` releasing relay 23. This relay, when it retracts its armature removes the holding ground which has been applied toA the test terminal 18 as a result oit which the relay 14 andfcut-etia relay will: cle-energize this system are ot the stay-put type they will remain in rengagement with the trunk circuits last used. The apparatus is now in condition to care for succeeding calls.

Let it be supposed that it is desired to call and since the non-numerical lswitches of' station A. f Then'a connectorswitch such'as f (lll wanted line is engaged as a calling line, ground `potential `is applied through the innermost iront contact and armature .oit the cut-eti rrelay 3 and test brush 5. It this line is idle it willbe seized and the .cut-ofi relay energized i-n a circuit including its lower winding and conductor 42. at this time the line relay 2 has not been yoperated. so that its arma-ture will prevent the 4complete yattraction of the armatures of cut-oil' relay and thus only its contacts c -are opened.

liet it -be assumed that when the subscriber substation A; initiates a call, :the trunk terminating in the secondary line switch brushes 35 and 36 Ilias been seized by another telephone line terminating at a substation similar to D. Under thiscondition when the test brush 5 engages the Atest terminal 13 corresponding to the pair trunks terminating in secondary line switch brushes 24e, 25, and .36, the line switch of Fig. l is prevented from seizing this vpair of trunks one of which has .already been seized. The guarding condition on test terminal @Bis afp )lied as .ollowsL-Since it is assumed lthat the kline corresponding to that rterminating at substation D has seizeda trunk while the line .corresponding :to that terminating `in substation A is idle, then ground is applied through 'fthe upper armature .and front contact ota relay similaivto 28, outer varmature and back contact of a relay similar yto 2` inner, lower .back Contact and armature of a relay siinilarto 8 and throughaftestbrush similar to 5 at the primary line :switch which has seized one of this pair otrtrunks to -test terminal 13. In this manner the primary line switch of Fig. l is :preventedfrom seizing a vpair of trunks one of whichwhas already been seized.

Figure 2 shows the same :principle applied to the distributionfof.calls from the incoming trunks to the other trunk circuits. In tl 's arrangement `the vincoming `trunks may terminate atl distantlautomatic otlice or may terminateiat-jacks-in'operators positions atidistantolices. In thisarrangement two incoming trunks terminate in the brushes of a primar y line switch :and this switch functions as soon as one of these incoming trunks is seized to select an idle secondary line switch.

At ,is believed that the operation of the systemdisclosed-in Figure 2 will ,best be understood by describing the method oit extending an incoming trunkcircuit to a wanted station, such as that indicatedat SE Let it be assumedthat acallingiline `(not shown) has been extended, Veither.manually or automatically to the incoming trunkcircuit whose conductors are designated bythe numeral 50. As soon asthis portion ofthe connection has been extended a circuit is completed for the slowrelease'relay 51 eX- tending from grounded battery,A its lupper tact and armature of the relay 52 test brush 55 of the primary line switch and test term,-

inal 56 which iscommon to a pair of trunk circuits leading to secondary line switches and thence to ground as will be described. t will be pointedout further in .this de scription that lwhenever a trunk circuit is' seized, a .relay such as 571er 5S is energized to apply ground potential to its terminal, such as 56 individual to this pair `of trunk circuits.

liet it be assumed :that :the ,rst pair ot idle trunks tested by the primaryline switch are those shown in Figure 2. As a result ot this'idle condition, guarding potential will be absent from the test terminal 55. As aresult of which the operating circuit ot the notor magnet 5d is incomplete and this magnet will stop the'brushes o'ithe switchin engagement with Ythe terminals of the ,pairof trunks here shown. e

At this ytime the relay 52 vwhich has vbeen short circuit-ed is now operatedin acircuit completed Afrom ground, upper `winding oit' the relay 52, Contact 53 and armature of relay 51; back Contact armature and winding of the motor magnet 5l to grounded battery.

r he relay 52 is operated in this circuit but themarginal motor magnet will not be energized in series with this last named relay. As soon as therelay is operated it interruptsthe operating circuit oi the slow releasing relay 5l but this .relay remains eneroizedjtora short period to :maintain the original operating circuit of the relay 52. At the `upper armatures and :trent contacts ot' the relay 52, a circuit is completed through the brushes :3Q-and (S0 ot the primary line switch and through the upper armatures .and back contacts of .the relay 6l to ground and through vthe winding olf slow releasing relay 57 to vgrounded battery. 'The :relay is operated in this 'circuit and at its inner armature and contact 62 it applies ground potential to the test terminal 56 of the selected pair of trunks to prevent Athem from being yseized by lother primary line switches. Also this ground potential is extended through thetest brush 55 .and the innermost armature r,and front Contact oi relay 52, vlower winding of this y 'mature and 'front Contact or' relay 57, Contact G4 and armatuure of relay 61, test brush (55 to ground 'at test terminals, such as 66fof busy trunks terminating at the secondary It will be noted'at` thistime line switch. thatthe relay Glfis short circuited by this lastdescribed circuit. The moto'r'magnet, however, is operated and advances its-brushes G5, 67, 68 and 69 until the vtest brush 65 engages a test terminallGG characterized by the absence of potent-iai which condition indicates that this trunk is-fidle. "When such an idle trunk is reached the operating circuitA ot the motor magnet 63 is no longer completed and the short circuit aboutjthe relay 6l is no longer 'eli'ective so that this relay is now energized in a circuit closed from grounded battery, winding, armature and back contact ci themagnet 63, winding otl relay (Si, contact and armature otrelay 57 to ground. Then the relay 61 is thus operated to attract its armatures, thev energizing circuit of the relay 57 is interrupted and since this relay is slow releasing in its cl'iaracteristics it will remain operated for a short interval to maintain the energizingcir- V cuit of the relay 6l. At the uppermost varmatures and front contacts of relay 6l, the connection is further extended to the brushes (i7 and 68 and through both windings in series ot impulserelay 72 associated Vwith the rst numerical switch to ground and battery. This relay is energized vin this circuit and etl'ects the operation ot vthe slow releasing relay 73 which operates inthe well known manner to apply av holding ground `to the trunk' circuit just seized andffurthei' to prevent the release of the selected numerical switch.

.As soon as the relay 73 is operated,` the` holding circuit for the secondary line switch is completed from ground at thearmature and t'ront` contact of the relay 73 throughithe test terminal 66 test brush 65, innermost lower armature,'front Contact and winding terr.

serves to apply ground potential ,to Vthe test et" relay Gl, ba cont-act armature and winding ot' the motor magnet 63 to grounded batlt will also benot-ed that this circuit terminal 66 to insure that the connection will not be disturbed at this point. 'y

"The appara-tus disclosed in Figure 2 is now in condition to be directively operatedY in response toV directive impulses transmitted from the distant office over the incoming circuit. In response to these impulses the nguineric'al 'switches such as selectors and con.1v

nectors will be diiectively operated to extend the connection to the wanted telephonelline, nthe sub-stationy of whichis indicated at E. The arrangement and operation of these numerical switches may be similart'o that disclosed in the'mentioned patent to Lamb, and

`for this reason it is not-necessary to describe 'the operation or lthe manner inA which` the wantedline is tested and= if idle, signalled; `Itis sutiicicnt to state that at the termination of Ythe conversation when the incoming trunltcircuit is opened either by the removal of the operators calling plug at the distant office (not shown) 'in the manual system or by the operationof the repeater (not shon n) ina fullautomatic system, relays such as 72 and 73 associated with theiinal numerical switch are released toremove ythe holding.

ground from t-he te-st terminal 66 so that the relay 61 will cle-energize. Similarly vthe holding circuit of the relay 52 which was extended through the test terminal 56 is f also opened sothatthe relay 52 also de-energizes. Since thek primary line switches and-the secondary line switches in this arrangement are also of the stay-put type, they remain in engagement with the trunks last used. Y Y

It will thus be seen-that whenever a, call isk extended over the incoming trunk circuit 50 or the `incoming trunk circuit 71k the primary line switch individual to these two trunlrcircuits vis operatedA to extend these circuits to anidle pair of trunlrc'irc-uits leading yto secondary line switches. f

It' the call originates over the incoming trunk 74 instead of over trunk 5,07 the relay 5l is energized in a circuit completed through its lower winding and over both sides of the incoming trunlfcircuit in series to ground.k

With relay 51 operated the motor magnet 54 yadvances the brushes of the primary linev switch as in the manner already-described.

Let it be assumedthat the incoming trunk circuit 50 has been extended to the secondary line switch shown inthe upper portion `of Figure 2 and that a call is then extended over the incoming trunk circuit 74. The relay 5l will not be energized since its operating circuit is open at the innermost lower contact and armature of relay 52 and therefore the motor magnet 54 will not be actuated so that the primary line switch is not moved from the pair of trunks already seized. The relay 58 will then be operated to close Yan energizing circuit for `the n'iotoimagnet 75 of the secondary linefswitch shownin the lower portion of Figure 2. y This motor magnet will then begop'erjated in the manner described in connection with the other secondary line switch of this disclosure to advance its brushes 76, 77, 78land 79 until its test brush 77 encountersv a test yterminal similar to 80,* which is characterized by the absence oaguarding potential 'at-which time the motor lmagnet 7 5 will cease tol operate and over the incomingptrunl; circuit will be ineli'ective to disturb the connection over the incoming trunk circuit 7 1 since the holding circuit for the primary line switch is controlled over parallel holding circuits independently controlled at -the numerical switches in succession of the extended connections.

` In the event that both the seconda-ry line switches of Figure 2 are in use simultaneously and it' one ofthese line switches is to be released before the other, a different releasing arrangement is provided from that previously described. It will ben'ot'ed that when the relays (S1 and 81 of the secondary line switches of Figure 2 are energized, indicating that these switches are in use, a circuit is completed from ground, at the arma-ture and front contact oit' relay/73, test terminal G6, test brush 65, innermost armature and front contacts of relay 61 and through the innermost, upper, front contacts and armature of relay 81, winding of this relay, back contact, armature and'windi'ng of the motor magnet to grounded battery. lt will thus be seen that if `it is desired to :release the secondary line switch at the lower portion of Figure 2 while the relay 01 o't the upper secondary line switch is operated, some means must be provided to release the relay S1. This is accomplished in the following manner. l'Vhen the release magnet R. E. L. associated with one of the numerical switches such as the connector switch, is operated, it completes a circuit from ground, its armature and front contact, Ytest brush 7 6, middle upper armature and front contact of relay 81, `lowerm'ost. front contact and armature of relay 61 winding` of the motor magnet 75 to grounded battery. This last described circuit is effective to short circuit the relay 81 causing it to deenergize and release the secondary line switch. Similarly if the secondary line switch at the lower part of Figure 2 is in use 1when it is desired to release the secondary line switch at the upper portion of this ligure, a similar circuit/is `completed to the brush 69 of that line switch to eect the deenergization of relay 61,.

ln the modified torni of the invention shown in Figure 3 this principle is applied to a `ful-l automatic system in which one line relay is provided for each pair ot' telephone lines, likewise also, the interlocking line and cut ott relaysl such as L. R. and C. O. or' Figure 1 have been associated with secondary line switches, so that their numberfs greatly reduced. lith this brief outline of the system ot Fig-ure 34 it is believed Lee-eea 'that the operation of the same will be best understood by describing the method of establishing a telephone connection from the sub-station such as M to a wanted substation such as that indicated at O. lVhen the subscriber removes his receiver from its switch hook a circuit is completed for the line -rela-y 100, extending `from grounded battery upper winding of this relay, innermost back contact and upper armature ot the cut ott relay 101, over the lower side of the calling line, and through the sub-station circuits i'n series and over the upper side of the calling line to ground at the uppermost armature a-nd back Contact of the' cut-oil relay. The line `relay is thus energized and at its lower armature and front contact closes a break-point i-n the operating circuit oi' the nrotor magnet 109. ,In the event that the brushes of the 'line switch are fin enga-gement with busy trunk circuits the test brush 10313 ot the line switch will be in engagement with the test terminal such as 10% com-mon to a pai-r ot' trunkcircuits which is characterized 'by the presence of ground potential. lVhen the line relay is thus energized to close lthe mentioned break point and with the test brush 103' in engagement wi-th a busy test terminal, an operating circuit is closed for the motor magnet 102 from grounded battery winding of this magnet, its back contact and armature, lower armature and front contact of the line relay 100 lowermost back contact and armature oit the cut-olf relay 101, test brush 103, test terminal 104 toA ground, at the front contacts and armatures of some one of the

relays

105, 106, 107 or 108. Under the control of this circuit the motor magnet 102 advances its

brushes

109, 110, 111, 103, 112, 113 and 1 1-l until the test brush 103 encounters a test terminal, 10st which is characterized by the absence of ground potential indicating that its associated trunks are idle. Then such test terminal is reached the operating circuit of the motor magnet 102 will no longer be completed and the primary line switch will be stopped with its brushes in engagen'ient with the selected trunk circuits. At this time a circuit is completed from grounded battery winding of the motor magnet 102 its back contact and armature, winding ol' the cut off relay 101, upper front contact and armature or the line relay 100 to ground. Thecut offyrelay is energized in this circuit and at its upper armatures and back contacts it interrupts the operating circuit oi` the line relay 100, but this relay is of the slow rcleasing type and therefore holds its armatures operated for a relatively short interval to maintain the initial energizing circuit of the cut ott1 relay 101. At the uppermost armatures and Jfront contacts of the cut oit' relay,the conductors of the calling nline are extended to the brushes 109 and 1,210 of vthe primary line switch and through the terminals with which these brushes are in engagement to the two sides of the selected trunk and thence to ground at the uppermost armature and back contact of relay 105` anol to grounded battery through` the inner upper armature and back contact of relay 105 and the winding of slow releasing relay 106. The relay 106 is energized-in this circuit to attract its armatures and at its inner arma-k ture and contactfllv it closes a holding circuit for the primary line switchextending from ground through lcontact 104, test wiper 103, lower armature and front Contact of the cut oli relay 101, winding of this relay, arma* ture, back contact and winding of the motor n'iagnet 102` to grounded battery. rfhe closing of thel inner arn'iature and contact 116 of relay 106 applies a guarding potential to the line switch brush 111 and through the front contact and inner lower` armatureof the cut off relay 101 to the conductor 117 leading to the multiple contactsof the calling line at the various connector switches through which it may be reached as a called line. At the outer' armature and front contact of relay 106 a break point is closed in the operating circuit of the motor magnet 118 of the se'- lected line switch and in the event lthat the

brushes

119, 120, and 121 of this line switch are in engagement with a busy ktrunk leading to an engaged numerical switch the test terminal such as 122 of this trunk will be characterized by the presence of ground potential applied from the armature and front;

Contact of a relay similar to 123 at some one of the numerical switches in the connection. As long as thetest brush 121 is testing busy trunks an operating circuit is closed for the motor kmagnet y118 from grounded battery winding of this magnet, lits backcontact and armature, outer armature and front contact of relay 106, back contact anda-rmature of relay 105, test bruslr121 and test terminal such as 122 of the busy trunk to ground at the trout contact and armature of arelay similar to 123. yUnder the control oi. such operating circuits the motor magnet 11S advances its

brushes

119, 120 and 121 of the secondary line switch until an idle trunk is located. .p

Let is he assumed that .the iirst idle secondary trunk tested is that appearing in Figure 3, under which assumption when the test brush 121 enga ges the test terminalv122 due tov the absence of the vground potential on test terminal 122 the operating. circuit of they motor magnet 118 will no longer Vbecompleted so that it will stop the line switch lwith its brushes in engagement with this selected trunk.

It will be noted that as soon as the relay 106 is actuated a circuit is closed from grounded battery through the vwinding ot' the motor magnet 118, its baclficontact and armature, [winding of the relay 105, kfront contact 1116 and k'armature of relay 106 to ground, but this last described circuit Lis ineffective to operate relay 105 because of the short circuit completed Athrough the test j matures attracted for ak relatively short interval after its operating circuit kis broken. At the uppermost armatures and front contactsof vrelay 105 ythe connection from the calling line previously established, is now extended through the secondary line switch brushes`119 and 120, over. the two sides of the selected trunk and the winding-of the impulserelay such as 124 of the succeeding numerical switch to ground and battery. Relay `124e is. energized in this circuit and eliects the operation ot slow releasing relay 123 which attracts its armature to apply ground potential to the test terminal 122y of the selected trunk and also completes a holding circuit through its brush 121, inner lower armature and front contact of relay 105 winding of relay 105 armature back contact and winding of the motor magnet 118 to grounded battery. n

It will be noted that the holding circuit for the primary line switch is now completed to ground through the front contact a`ndar mature. of the, relay 105. rThe ap paratus is now in condition to receive di* rective impulses from the dial sender at the calling substation ybut it is not necessary to describe the operation of `the numerical switches such'asthe connector herein shown to establish the wanted connection, since suchoperation isnow ywell known in the art and' may be similar to that outlined in the mentioned patent ,to Lamb. n

ALetkit be assumed that` the ,subscriber at substation N. desires to establish a telephone connection d-uring the time that subst-ation M is calling; Y v Y Under the conditions assumed t-he `cutoff relay 126- ot the calling line N is in operatedrondition `since it kwas' energized in multiple with the cut Off relay 101, as soon as that relay was; operated. Also the brushes 113 and-114 of the primary line switch will be in engagement with -the terminals of the selected primary trunks since the prei-iously -mentioned operation of the primaryfline switchY was effective to select a pair of idle trunks. lVhen the subscriber at N Iremoves his receiver from its switch hook the slow releasing relay 107 of ythe secondary Alineswitch will be immediately energized in a'eircuit closedfrom grounded il U ino

` of' the, secondary' battery, winding ofthis relay, inner lower armature and back contact of rela-y 108 and through the tivo lines ot" the selected primary trunk and calling line in series to ground at the loivermost armature `and back contact oit relayv 108. Relay 107 at its inner armature and contact 128 applies a guarding potential through 4terminal 127, brush 112 upper front contact and armature ol the cut oli rela-yr 126 through the multiplev tern'iinals (not slroyvn) et the 'calling' line at a' group of vconnector svvitches, Also at this Atime the motor magnet 132 ine switch is operated in circuit completed from grounded battery, Winding ol' the motor magnet 132, its back contact and armature, outer armature and trent ctnitact ol' relay 107, inner upper back con-tact and armature ol relay 108,' test brush 12.9: and test terminals such as 133 ot busy trunks to ground at 'the liront Contact 'and armature' of a relay such as y123 at' the succeeding numerical switch. When such tan idle secondary triink is located it will be characterized by the ab-y sence ot 'ground potential at itsftes't terminal and the voperating circuit vof the Minotor n iagnet 132 rvill no longer be complete so that the 'secondary line s ivitch will stop its

brushes

1219, 130 and 131 in engagement with the` terminals 'of an idle secondary trunk. rlhe relay 108 which 'has been short circuited during the operation of the secondary line switch is now energized from grounded batteryI Winding ol the motor magnet 132 its 'back contact and armature ivindinjg of relay `108 contacty12`8 'and armature of relay 107 to ground. As soo'n as the relay 108 is energized in this circuit it is locked operated through its innermost upper front contact and armature, test brush 129 'and test terminal similar to 133 to -grour'id at the front Contact and 'armature of the relay similar ui 123 at the selected numerical switch. i l A lVhen a calling subscriber such as M deci des to terminate the connection, he replaces his receiver on its switch hook at which time a relay such as 124 of the inal numerical lsivitch has its operating circuit interrupted and d'e'e'nergizes to effect the release vol a relay such as 123 which has been holding the connection. The relay 123 on dcenergization removes the holding ground from the test terminal such as 122 which caiises the relay 105 of the secondary lin-e Sisyphe typ their hashes ieii'iaih `iiieii-gageinent With the terminals ot the trunks last used.

Let it be assumed that it is desired to call the line terminating at substation M. lVhen a connector switch (not shown) seizes this line, ground at the connector Will be applied to the conductor 117 s'o that a circuit is coinpleted through the louer Winding of the line relay 100 to grounded battery. The line relay 100 is energized in this circuit and if the tivo sets of brushes or' the primary line siv'itch are in ei'i'gag'ement with busy trunk terminals the motor magnet 102 will advance the brushes of the primary line switch until idle tru-nhs' are located by the test brush 103 'at ivhi'ch time the cut olf rel-ay 101 of the called line Will be operated in the manner already described. As soon as the contacts of relay 101aie thus operated the test con-- ductor 117 is extended through its inner loi'ver armature and front Contact, line sivitch brush 111, ivindin'g of relay 105, armature, back Contact and winding of the niotor magnet 118 to grounded battery, and since the relay 106 has not been operated prior to the operation of relay 105, this last named relay although energized will operate all its contacts except these marked c. It Will thus be seen that the relay 106 will not be operated when the called party removes his receiver from its switch hook and likewise the brushes 119A and 120 ot the secondary line s'ivitclr are not connected to the called line. The cut oil relay 101, however, is locked operated through the test brush 103 to ground at the loiif'ermost front contact vand armature of relay 105'.

Atthe termination of the Vcall to the line M. when the calling subscriber releases the connector, ground potential will be removed from conductor 117 so that the relay 105 Will release and at its lowermost armature and trontcontac't open the' holding circuit of the cut oit relay 101.

It irill be understood that the arrangements disclosed in this application are merely typical of applicants invention and the saine may be Widely varied Within the scope of the appended claims Without departing 'from the spirit ot the present invention.

that is claimed is z- 1. In a Atelephone system, an automatic sivi't'ch provided with sets ot brushes and fixed terminals, a pluralityot independent incoming circuits, one incoming` circuitterminating iii each set ot brushes, a plurality ottrunks t'eijiiiinating in said lixed terminals, means for rendering` trunks busy, and means l'or operating `a switch to extend its incoming circuits to idle trunk Acircuits in response to the initation ot a call oiier one ofmsaifdincoining circuits.

e. 'The method of extending @ii-cuits which consists in arranging circuits into groups a call over either of said incoming circuits 65 and sub-groups, arranging trunks groups, extending all the circuits of a suhgroup to seize idle trunks ot a group on the initation of a call over one ot said circuitseral incoming circuits and trunk circuits ter-k c minate, means controlled over the two sides et an incoming'circuit in series 'for operating said trunk limiting switch to Ventend the incoming circuits to idle trunk circuits, and means to extend said last mentioned trunks separately and conteinporaneously.

5. In a telephone system, a plurality ot independent incoming circuits, a plurality of trunk circuits, means including primary and secondary line switches for interconnecting incoming circuits and trunk circuits, each primary line switch heing connected to a group otincoming circuits, and means responsive to the initiation 0i a call over any ci said incoming circuits of a group for extending all of the incoming circuits of this group to idle secondary line switches.

G. In a telephone system, a plurality of independent incoming circuits, a plurality oi out vgoing circuits, a trunk-hunting nonnumerical switch in which said incoming circuits terminate and means including said non-numerical switch responsive to a call over any of' said incoming circuits for extending all of said incoming circuits to idle outgoing circuits.

7. In a. telephone system, a non-numerical switch provided with brushes and iiXed terminals, a pair oi incoming circuits terminating in said brushes, trunk circuits terminating in said lined terminals, means responsive to the initiation of a call over either ci said pair of incoming circuits for operating said switch, a single test brush for said switch, and means controlled through the same tor stopping said switch in engagement with idle trunks.

8. In a telephone system, a pair oi incoming circuits, a plurality oit trunk circuits, a non-numerical switch individual to said pair ot incoming circuits, means for advancing said switch on the initiation of into circuits.

busy,

-ior extending the saine to idle trunk circuits, and holding circuits 'for said switch controlled at any one of said selected trunk 9. In a telephone system, a plurality oft incoming circuits, a plurality ooutgoing circuits, a nonaiumerical'lswitch in which said incoming circuits terminate, said nonnumericalswitch 'functioning to` extend said `icomiiig circuits to idle outgoing circuits, a motor magnet for controlling the i-arious Loperations ot said noirnunierical switch, a relay controlled over any oi' said incoming circuits ttor initiating the operation of said meter magnet, and a relay controlledover any oi said outgoing circuits and held operated during a connection for discon necting said first relay from control of said incoming circuits.

10. In a telephone system, ank automatic switch provided withV sets ot brushes and passive terminals, a plurality of primary circuits, a primary circuitterminating in each set of said brushes, a plurality of secondary circuit terminating in said passive terminals, means `for rendering saidcircuits and means for operating a switch to extend its primary circuits to idle secondary kcircuits when a call is initiated over one ot said circuits.

l1. In a telephone system, a plurality oi incoming circuits, a plurality of outgoing circuits, a non-numerical switch in which several incoming circuits and several outgoing circuits terminate, and meansincluding a relay contrellahle'over th-e two sides of any one of a plurality of said incoming circuits in series ior operating said nonnumerical switch to extend each of its incoming circuits to a separate idle outgoing i circui ,12. In a telephone system, a pluralityr oi'1 rincoming circuits, a plurality of outgoing circuits, 'a non-numerical switch in which several incoming` circuits and several outgoing circuits terminate, means including.

a relay controllable over the two sides ot any one of a plurality or" said incoming circuit in series, and a motor magnet governed by said relay for operating said non-numerical switch to extend each ot its incoming circuits to a separate idle outgoing circuit.

13. In a telephone system, a plurality oi incoming circuits, a plurality of outgoing circuits, a non-numerical switch in which several incoming circuits and several outgoing circuits terminate, means including a relay controllable over the two sides of any one of a plurality of said incoming circuits in series, a motor magnet governed by said relay for operating said non-numerical switch to yextendr all ot its incoming circuits, to idle outgoing circuits and a cut-oil' relay operated responsive to the extension of said incoming circuits to disable said iirst relay.

14. In a telephone system, a plurality of independent incoming circuits, a plurality of trunk circuits, means including primary and secondary line switches vfor interconnecting incoming circuits and trunk circuits, said primary and said secondary line switches being of the type that remain in the position last used, each primary line switch being connected to a group of incoming circuits, and means responsive to the initiation of a call over any of said incoming circuits of a group for extending all of the incoming circuits of this group to idle secondary line switches.

15. In a telephone system, a primary line switch having two sets of brushes and sets of fixed terminals, a telephone line terminating in each of said sets of brushes, a plurality of trunks each terminating at one end in a set of tiXed terminals, a secondary line switch for the other end of each trunk, means for seizing one of said telephone lines as a called line, means responsive to such seizure for extending said called telephone lines to a secondary line switch, and a trunk release arrangement for controlling the release of operated switches.

In witness whereof, I hereunto suhscribe my name this 5th day of May A. D.

WINFRED T. POWELL.