US1681035A - Automatic telephone system - Google Patents

Description

J. E. GARDNER AUTOMATIC TELEPHONE SYSTEM Original Filed Aug. 12. 1921 2 she t -she t- 1 Jul-m E Bardnsr Aug. 14, 1928. 1,681,035

J. E. GARDNER AUTOMATIC TELEPHONE SYSTEM Original Filed Aug 12, 1921 2 Sheets-Sheet 2 Jul-m E. Gardner W 5]? Patented Aug. 14, 1928.

UNITED} STATES, IrATEnroFFlcE;

JOHN E. GARDN R, or wttxmsnune, rmtusynvaum, ,ASSIGNOR,' BY MESNE .AS- sienunnrs, r0 auromamc ELECTRIC me, or cnrcaco, rumors, A consonarron or DELAWARE.

euronarrc TELEPHONE SYSTEM.

continuation otapplieeticn Serial No. 684,821, filed February 25, 1924, and a refiling of application Serial No. 491.745, filed August 12, 1921. This application filed April 22, 1925. I Serial No. 24,915.

The present invention is the same as the inventiondisclosed in in prior application, Serial No. 491,745, file August 12, 19 21, and relates in general to automatic telephone systems. It has for itsprincipal object the provision of new and. improved circuits for connector switches used in' such systems whereby the operationsof these switches are rendered more satisfactory. Certain features shown and described but not claimed in this application are being claimed in my pend ing applicatiomSerial No. 694,821, tiled February 25, 1924. v A

A feature of theinvention has'to do. with the provision of new circuit arrangements in the connector switches whereby when a connection is cxtendedto a called line and after the conversation is terminated the called subscriber in. hanging uptakes the guarding potential off the mu'ltipletest contacts associated with his line. though theconnector is still maintained operated. If the called subscriber now removes his receiver in order to initiate another call the connector and all the other switches used in the connection are immediately released. Or should another connectorswitchzestablish a connection with the called line whilethe-first connector is in its operated position the first connector as well as the other switches used in the extension of the previously established con-. nection will be released.

Another feature of this connectorcircuit is that in case the connector switch does not; completely extend the connection to the called line after it is reached,that is, if the corn nector does not function properly, it is held locked in its o eratedposition even afterthe calling subscr ber hangs up, though allg'the other switches are released and an alarm is given to the attendant inorder to call-the trouble to his attention. In addition to this the connector switch is made busyso that 1t cannot be used for another call until the trouble is cleared. The connector also operates in this manner in case the line is open shows a calling station A, the individual line switch 0, and the selector E, whileFig. ishows the connector H and a called station In the drawings the invention has been shown applied to a small system of 300 lines capacity and therefore the selectors in the systemneed only have access to three groups of trunk lines leading to connector switches. It will, however, be evident that this system may be readily enlargedto any desired'size by providing more bank contacts in the selectors of the system. f a Referring now to the drawings, in Fig.1 is shown. a substation A of the usual automatic type the associated line of which terminates at the exchange in individual line or trunk selecting; switch C. Theline switch C is of the Well known rotary type which does not restore to normal but maintains its wipers in, engage: ment with thetrunk line last used. The line switch C, in common with a. plurality of other line switches: has access to selector swi-lt ches one of these selectors being shown at J V The selector switches are similar in mechani cal construction to the rotary line switches. However, these, selectors have thirty contacts in their banks instead of the usual twenty-five as have'the ordinary line switches. These thirty contacts are then divided into three groups of ten contacts each thus providing ten trunks in each group inaccordance with the usual practice. The selector E has access to trunk lines terminating in connector switches in the various groups, one of these connectors being shown atlfl, Eig. 2.;: a V

The connector switch H i's'of the usual Strowger vertical and rotary type and has access to called sub'scril'ierslines one ofthes beingshown at A", l I

, Thesubstation A is similar to the substationA already described andflits associated line terminates at the exchangein the individual-line switch C.

Having briefly described shown in the drawings, a detailed explanationof its operation will nowbe given. For this purpose it will be assumed that the subscriber at substation A desires to call the subscriber at substation A.

the apparatus In order to do this the subscriber at substation A will remove his receiver and operate his calling device in accordance with the three digits of the number which is assigned to the substation A. hen the receiver is removed at the substation A a circuit is completed for the line relay 16 of the individual line switch C over the line conductors 11 and 12 in series. Relay 16, upon energizing. at its armature 25 completes a circuit which includes the switching relay 15 and the motor magnet 17 in series and at its armature 26 connects the test wiper 31 to the above circuit at a point midway between the switching relay and the motor magnet. The operation of the line switch C now depends upon whether or not its wipers are associated with an idle trunk line. If the associated trunk line is busy there will be a ground potential present upon the contact engaged by the test wiper 31, switching relay 15 will be short eircuited and the motor magnet '17 being supplied with direct ground via said test wiper will operate as a buzzer to advance the switch wipers 3()32.' inclusive, step by step until they are rotated into engagement with a. set of bank contacts associated with an idle trunk line. However, in the present case it will be assumed that the trunk line with which the line switch wipers are associated when the receiver is removed at substation A-is idle, and it will be assumed further that this trunk line is the one shown in the drawings terminating in bank contacts 33-35, inclusive. Under these conditions there will be no ground potential present upon the test contact 34 engaged by the test wiper 31, motor magnet 17 will not operate, and the switching relay 15 not being short eircuited will immediately energize in series with the said motor magnet. Relay 15, upon energizing, disconnects the line conductors 11 and 12 of the substation A from the winding of the line relay 16 and from ground, respectively, and extends them by way of armatures and 22, wipers and 32, bank contacts 33 and 35, to the winding of the line relay 52 of the selector E and to ground, respectively.

The line relay 52 is immediately energized over the calling subscribers line loop and, upon operating, at armature 65 completes a circuit for the slow acting relay 53. The latter relay, upon energizing, at armature 68 prepares certain impulsing circuits in the selector E and at armature 66 places ground upon the release trunk conductor 49, thereby establishing a holding circuit for line switch C. This holding circuit extends from ground onrelease trunk conductor 49, test contact 34, test wiper 31, armature 21 and its front contact, through the winding of the switching relay 15, and thence through the winding of the motor magnet 17 to battery. It will be understood that the above traced holding circuit is completed before the slow acting line relay 16 has had time to deenergize. A branch of this holding circuit extends by way of the private normal conductor 28, to multiply connected test contacts in the banks of connector switches which have access to the line of the substation A whereby the said line is protected from intrusion in the usual manner.

The calling subscriber at substation A may now operate his calling device in accordance with the first digit of his desired number. By this operation a series of interruptions is produced in the circuitof the' line relay 52 of the selector E which retracts its armature a corresponding number of times. At the first retraction of its armature 65 an impulse of current is sent over a circuit extending from ground by way of back contact and armature 62. armature 65 and its back contact, armature (3S and its front contact, armature 71 and its back con tact, armature 79 and its back contact, and through the lower winding of the first counting relay to battery. The lower Winding of relay 55 is of high resistance and has a low number of turns; thus it is only strong enough to attract the armature 78 thereby completing a circuit which extends from ground by way of armature 67 and its front contact, armature 70 and its back contact, armature 78 and its front contact, through the upper and lower windings of relay 55 tobattery. However, as long as the armature of the line relay 52 is in a retracted position the upper winding of relay 55 is short eircuited and the above traced circuit is ineffective. When the line relay attracts the armature 65, the two windings of the first counting relay 55 are immediately energized in series and all the armatures on the relay are operated. Relay 55, upon operating at, its armature 77 prepares a point in the testing circuit. at armature 79 transfers the impulsing lead to the second counting relay 56. at armature 81 prepares a point in the circuit of the switching relay 50, and at armature 82 places ground upon the conductors 100 and 101, whereby the second and third common sections of the bank corresponding to all the trunk lines in the second and third groups and adapted to be engaged by the. wiper 94 are grounded. The slow acting relay 58 is energized in multiple with the counting relay 55 and at its armature 76 maintains the previously mentioned test circuit opened and also the circuit of the relay 50.

At this point it will be well to describe how the trunk lines accessible from the selector E are dix ided into groups. In this case it is necessary that the selectors have access to three groups of trunk lines. In

addition to the usual line andztest banks provided for switches of 'this rotary con striiction there is anextra LSBt of bank contacts and an "extra Wiper to er'igagethem. This extra set of baiilc'contac'ts is divided intothree groups of ten trunks each, all the contacts of each group being iiniiltiply connected. Thus it will be seen that as soon as ground is placed upon the conductors 100 and 101 all the contacts associated fwith the trunk lines in the second and third groups in this extra bank adapted to be engaged by the wiper 94 are grounded. The purpose of this will "appear fully'hercinafter.

Returning now lto the "operation or the line relay 52 up'onthe next retraction and attraction of its armature thejsecondfcounting relay 56 is energized "in a nia unersiniilar to relay 5 5. Relay 56*, upon 'en ei gizing', "at armature 85 eiztends the inipulsi'ng lead to the third counting may; armature '86 disconnect-s ground froin the conductor T01 whereby ground :is removed from an the contacts in the secondgroup in the bank adapted to be engaged by wiper 94'. At the front 'contact'of armature 86,?relay 56 places ground upon conductor 102 thereby l-turning all the contacts associated with the first group of "trunk lines in the contact bank adabte'dtobe'enga'g ed by wiiper 94. Assuinin that digit 2 has beeh called by the calling subscriber the line rela -52 will new maintain its 'arma-tures attracted; The slow acting relay 58 is maintained e ergized tliroughout the series of impulses jvvhichfconstitute the first digit-of the desired number and shortly the a termination thereof deenergizes, It war be apparent that when ground is (placed upon theva ious ro of contacts faaplted to beengaigedlbythe' r 94-thlit, as theswi'tch have no; norinal position, the said wiper ivillgbe grounded. he "stepping relay '51 is theflebyyerimgized and upon operating, "at armature 69 prepares a point "in the circuit of '*the *rothry i'nagn'et 59 andat armature 6f n s a point in the testing circuit of test ipei- 93. ii the switch Wipers "are stiandii'i g in a group other than that whichis called by thejcalling subscriber there will bea ground poteut'iaipi-es e'nt upon the contact eiigagedby the Wiper 94 and the stepping relay 51 will lie energizedas previouslymentioned. Then; relay 58 u on deenergizingya't its armature 76 completes the circuit of the motorir'rnagnet '59.

Magnet 59 operates to' i-ota te the switch wipers into engagement with the next set of bank contacts thus openin the circuit; bf the stepping relay 51*. -As*thfe switch'wipers have been assuiried to be stand-ing in a group other than that desired therewi'll bea ground potential presentupoh this test contaet provided, ofcourse, that the switch wipers have not been rotatedinto engalgemeht' with the trunk lines of the" second group ahd step ping "relay 51 will doeaga n energized to cont, pletethe circuit of "the rotary magnet 59. The alternate operation of the stepping relay 51 and the rotarymagnet 59 will continue until theswitch wipers are rotated into selec= tiv'e relation with the group of trunks which terminate in the connector switches that have access to the desired 'sub'scrib'ers' line; the digit 2 was called by a calling subscriber thefirst and third groups of bank contacts adapted to be engaged by the rest Wiper 94 Willbe grounded and the switch wipers will be rotated by the operation of the stepping relay 5 '1 until they are brought into selective relation with the first trunk linein tlik second group. This second group of bank contacts adapted to be engaged by the test wiper 94y'will not 'begrounoled, there will be nocircuit completed for the stepping relay 51 and the test wiper 93 will now come into operation. If the first trunk line in the second group is busy there will be a ground potential present upon the test contact "ongaged by the test wiper 93 and a circuit is completed which extends fro1n the said grounded test conta'ct'by way of test Wiper 93, armature 61 and its back contact,,f1'ont contact and armature 77 armature 6 and its back contact, back contact and armature 83 armature76 and its back contact, and thence through the "winding of the niotor magnet 59 tobatt'ery. Themotor magnet 59 is thereupon operated to advance the switch wipeisinto engagement with the next set of bank contacts in the selected group"a:nd at the same time breaks'its own circuit at armature =83. If this 'nexttrunk lineis busy theassoci ated' test contact fwill be grounded and the motor magnet -59 will operate as before. The Operation of inagnet 59 will continue until the switch wip'ers'are rotated lllll into engagement with an idle trunk line.

However, it will be assumed in the present casethatthe first tru'nk line in the second group is idle and it will be assumed further that this is the trunk line shown in the drawings "and terminating in bank contacts 9698, inclusive. It will benoted that the switching relay 50 whosev'circuit is completed by the rdeenergization of slow actilng' relay 58 is short circuited' by ground from the various test 'con'tao'ts duringthe trunk selecting operation of the switch; NVhe'n this idle trunk-its found there will be no ground potential present upon the test contact 97, motor magnet '59 not operated, and the switchinggrelay 50 "being no longer short circuitcd is in'in e'diately'energiz'ed in series withthe s'ai'd motor magnet. Relay 50, upon energizing, at armature 62 disconnects ground from the front contact or armature 69 and opens the'cii'cuit of the slow acting relayv533 at "armature 61 opens the testing circuit, att-li'e front contact of thisarrnature closes *a lockin g 'circu-itior itselt, and for switching relay 15 of the line switch C, and at armatures 60 and 63 disconnects the incoming trunk conductors from the winding of the line relay 52 and from ground, respectively, and extends them by way of the said armaturcs, w pers 92 and 95, bank contacts 96 and 98, trunk conductors 105 and 107, and thence through the upper and lower windings of the line relay 126 of the connector H.

Line relay 126 is immediately energized over the calling subscribers line loop and, upon operating, at its armature 142 completes the circuit of the slow acting relay 127. The latter relay, upon energizing, at armature 143 prepares the operating circuits of the connector H and at armature 144 places ground upon the release trunk conductor 106 thereby completing a holding circuit for switching relays 50 andv15. This holding circuit extends from groundon release trunk conductor 106, test contact 97, test wiper 93, armature 61 and its front contacts, through the winding of the switching relay 50, back contact and armature 83, armature 76 and its back contact, and thence through the winding of the motor magnet 59 to battery. A branch of this holding circuit joins the previously traced holding circuit of the line switch C. It will be understood that the above traced holding circuit is completed before the slow acting relay 53 has had time to deenergize. It will be seen that relay 53, upon deenergizing, opens the locking circuits of the various counting relays which have been energized in response to the digits sent by the calling subscriber and these relays then deenergize to remove ground from the various groups of contacts in the bank adapted'to be engaged by the wiper 94 and to restore certain other circuits in the selector E to normal.

The calling subscriber may now operate his calling device in accordance with the second digit of the desired number. By this operation a series of interruptions is produced in the circuit of the line relay 126 of the connector H and this relay deenergizes a plurality of times in response thereto. At the first retraction of its armature a circuit is completed which extends from ground by way of armature 142 and its back contact, armature 143 and its front contact, oif normal springs 148 and 159, through the winding of the low resistance slow acting relay 128, and thence through the winding of the stepping magnet 186 to battery. The above is the circuit over which the first vertical impulse is transmitted. However, upon the first vertical step of the shaft the OK normal springs are shifted vand the remaining impulses to the vertical magnet traverse a new circuit which is the same as the one previously traced except that it includes the OE normal springs 148 and 149 and armature 124 and its front contact, relay 128 being new in an operated position. The vertical magnet 186 operates to raise the switch wipers 190-192, inclusive, step by step until they are placed opposite the desired level of bank contacts in which is located the contact set associated with the substation A. The vertical magnet also raises the release link on its first energization to permit the double dog to engage the shaft. The double dog, in addition to retaining the shaft, moves the spring 139 into engagement with its associated contact, thereby preparing a locking circuit for switching relay 134. The slow acting relay 128 is energized in series with the vertical magnet and maintains its armature attracted throughout the vertical movement of the switch and at the termination thereof deenergizes and transfers the impulsing circuit to the rotary magnet 187.

The calling subscriber may now operate his calling device in accordance with the third and final digit of his desired number. As before, a series of interruptions is produced in the circuit of the line relay 126 which retracts its armature a corresponding number of times. At each retraction of this armature 142 an impulse of current is sent over the following circuit: ground, armature 142 and its back contact, armature 143 and its front contact, off normal springs 148 and 149, armature 124 and its back contact,,back contactand armature 168, armature 179 and its back contact, and thence through the winding of the rotary magnet 187 to battery. Magnet 187 operates to rotate the switch wipers into engagement with the set of bank contacts associated with the desired line which, we will assume, are the bank contacts 193-195, inclusive, in which is terminoted the line of the subscriber A. The slow acting relay 133 is energized in multiple with the rotary magnet and operates at its armature 170 to connect the test wiper 191 to the test relay 132.

Assuming that the desired line is busy at the present time, there will be a ground potential present upon the test contact 194, and a circuit will be completed extending from the said grounded test contact, test wiper 191, resistance R, armature 170 and its front contact, normally closed springs controlled by armature 177, and thence through the winding of the test relay 132 to battery. Relay 132, upon energizing, prepares a point in its locking circuit at armature 167 which is completed immediately upon the deenergization of the slow acting relay 133 and at armature 169 places a] busy tone upon the lower heavy talkingconductor. In this manner the usual audible signal is returned to the calling subscriber in order to inform him that the desired line is busy and he will replace his receiver thereby releasing the operated-switches in a manner which willibe described hereinafter;

It willlnow be assumed that when the switch Wipers 19.0.192, inclusive, of ithe con nector HT are rotated into engagement with the bank contacts 193-195, inclusive, the line of the substation Avis idle. .Under these conditions there will be no ground potential present upon the test contact engaged by the test wiper-l9landrthere willbe no circuit completed forthe vtest relay 132i 'lhenimmediately following the cleenergization of the slow acting relay 133 a circuit: is completed which extends from ground on-release trunk conductor 106, armature 167 and its back contact, upper winding offswitching relay 134, back contact and armature 170, resistance R, testwiper'191, testcon tact 194, through the winding ofthe-switehing and cut-oil" relay 200 of the-line switch C and thence through thewinding of the mo tor magnet- 202 to battery. The switching relay 134 and the cut-oif'relay 200 are ener gized over this circuit: However, dueto a mechanical interlocking device controlled by the armature of the line relay 201Jwhich is now normal, the relay 20.001113 partially'at'f tracts its armatures,that is, enough to disconnect the line of the substation A" from its normal battery and ground connections in the line switch C;

In the connector H, relay- 134, upon operating, establishesa lockingcircuit for itself to ground on release trunk conductor 106 at armature 180, at armature 181 places direct ground upon the test wiper 191, at armature 177 opens the testing circuit offithe test relay 132, at armature 17 6 opens-a point in the circuit of the release magnet, atartna ture 184 places an additional ground upon the release trunk conductor 106 and at armatures 175 and 183completesjtlieringing-circuit. Ringing current is "now interniittently projected out on the called line 'until "the subscriber at substation A answe'rs.f'Another result of the energization of'relay 13 i is that a circuit is completed which extends from ground by wayof back contactand armature 162, front contact and, armature 182, conductor 197', through the lamp 198', and thence through the winding 'off'relay 205 to battery. Relay205 is energized over this circuit and, upon operating, at its arma ture 220 closes the circuit of the solenoidS. If the ringing circuit is completed for'the substation A the ring up relayv 131 will be immediately energized. Relay 1 31, upon operating, establishes a; locking circuit for itself at armature 161, at armature 162 opens a the previously traced circuit of? the relay 205, at armature 158 closes a'point'in'the release circuit, and at armature short circuits its upper winding.

If for any reason the called line wasr oplen the ring 'up relay 131 wbuldnot be ener gized andithecircuit of :the relay 205. would be ma ntained closed; As was mentioned previously, the A relay 205,1 upon operating,

closes the circuiti'of the solenoid S. The

for a considerable time on "account f the dash pot 215-which, though it does not allow the plunger 1210 to v pull 7 up quickly does not -retardwitsrestoration. However, as the relay 131;? in the" connector switch is not operated-thecircuit of the relay 205 will be maintained closechand the solenoid S will finallypull the plunger 210 into its operated position thereby causing the cam 214 thereon to force the sp'ring213 into engagementwith its working cont act. Ground is thereby placed on "the conductor 207' and a signal is given to the 'atten'dant. It should be imentinned at this point-that the lamp 198 i is common to a group o'tc'onnector switches which have; access toga group of ealled lines and lights in series 'witlrj therelay 205. The attendant, upon hearing the alarm, will look t6 see what lamp suchas 198; is lighted in Orderto" determine in what group the con necthr swit'ch "giifiing 'trouble is located. The attendant will be-able] t o ascertain what connector switch is in I trouble 7 listening in on'the operatedconnector switches and after" finding the connector in trouble, he will "infer-m the calling subscriber to callthe desired" number 1 afisdrhe later time. p

When I the calli'ng subscriber replaces his receiver, which may occur shortly "after the operation of the connector switch'fas' he will ha'rino rin ing induction,- br in compliance with-therequest of the-attendant, the line relay 126 deem 1= i-ze and o ens the circuit ofth slow acting relay 127;. After the deen'efrgizat'ion of the-line relay 126and before theflenergiz'atio'n' of the slow acting relay 127 an impulseof current is sent to the slow acting 1-em ,1'-33; Rua 1'33 energizes at this time and removes' -one' ground from the release trunkconductor '106- at armature 170 andat armature 5 17 3; and "at armature 172 transfers thlbckihg circuit of the relay 134* from the: release trunk '106 to grounded armature 163. deenergization of the s1ow'act'ing relay 127; ground is removed from the r elease tru'nk "conductor106) The connectorswitch is not released att his time as the release magnet circuit is-opened at armature '176. "When ground"is remoyed from release trunk conductor 106 the holdingeippu'it for the"switching "relay of the selector-E and relay 1 5" oftlie line switch "C is opened and these*relays tleenergize. It will be noted that the wipersof the selector switch are In aintained 'in engagernent with the contacts 96 98, inclusivefwhich are the bank contacts/associated with the trunk line last used andthatthese samewipers or: the

lac

selector E have no normal position. The deenergization of relay 50 serves to restore the circuits of the selector E to normal. Relay 15, in the line switch (3, upon deenergizing, again connects the line conductors of the substation A to the winding of the line relay 16 and to ground.

Returning now to the operation of the connector switch H when the slow acting relay 127 deenergizes the circuit of the slow acting relay 133 is opened. Relay 133, upon deenergizing, at armature 173 again 6011-. neets ground to the release trunk conductor 106 over the following circuit; ground by way offront contact and armature 184, back contact and armature 173, back contact and armature 188, to release trunk conductor 106. Another result of the deenergization of relay 133 is that the locking circuit of the switching relay 134 is. transferred to the release trunk conductor 106 at the normally closed springs controlled by armature 172. The replacement of ground upon release trunk conductor 106 serves to prevent the connector switch H from being seized, and used in another call. \Vhen the attendant has cleared the trouble he will operate the armature of the release magnet thereby restoring the switch shaft to normal. The springs 139 are a kind of off-normal springs but they are adapted to be controlled directly by the vertical and release magnets, that is as soon as the vertical magnet operates the spring 139 engages its working contact andias soon as the armature of the release magnet is operated the spring 139 disengages its working contact. This spring 139 may be mounted on the double dog of any Strowger switch. By the operation of spring 139 the locking circuit of the relay 134 is opened and this relay deenergizes thus restoring the circuits of the connector H to normal at the same time removing ground from the release trunk conductor 106 and thus again rendering the connector H accessible to the selector switches. Another result of the deenergization of the relay 134 is that the circuit of relay 205 is opened and this relay deenergizes opening the circuits of the solenoid S which immediately restores to normal, as the dash pot 215 has no appreciable effect upon the downward operation of the plunger 210.

The above described operations take place and an alarm signal is given to the attendant under various conditions some of which will be briefly pointed out. In case the generator lead is open the relay 131 will not energize and the attendant will be signalled as before described. If the line wipers of the connector H are open, or out of alignment, or if the line wiper cords are open, the relay 131 will not energize and the attendant will be signalled. This also happens in case the private wiper is out of alignment with the line wipers far enough so that when the switch is operated the private wiper and the line wipers become associated with different lines. That is, 1 the private wiper may be incorrectly positioned on the shaft so that it stands a step ahead or one or more steps behind the linewipers. .In this case the cut oil? relay 200 in the called line switch, the one engaged by the line wipers, is not operated and the ringing circuit is short circuited by the ground connection in the line switch. It will be seen that there are a number of other times when this alarm will be given to the attendant such as when the called line is grounded outside the central office and so on. However, as these conditions are perfectly obvious they will not be mentioned.

Should the calling'subscriber replace his receiver before the connector H has established connection with the desired line the line relay 126 will be deenergized and operate to open the circuit of the slow acting relay 127. The latter relay, upon deencrgizing, removes ground from the release trunk conductor 106 and' also closes the release magnet circuit over a path extending from ground by way of armature 142 and its back contact, armature 143 and its back contact, armature 135 and its back contact, back contact and armature 176, working contact of off normal spring 145 and said spring, and thence through the winding of the release magnet 185 to battery.

It will now be assumed that the connection was completely established and that the line of the substation A was not in trouble. Under these conditions the relay 131 will be energized and operatein the same manner as was before described. When the called subscriber answers the ring out off relay 130 will be energized over the called subscribers line loop. Relay 130, upon operating, at armature 152 establishes a locking circuit for itself, at armature 154 removes the direct ground connection from the private wiper 191, at armatures 156 and 155 opens the ringing circuit, and at the front contacts of these armatures finally completes the talking connection. The back bridge relay 125 is immediately energized over the called line and, upon operating, at armature 137 closes the circuit of the slow acting relay 120. at armature 135 opens a point in the circuit of the release magnet, at armature 141 again places direct ground upon the test wiper 191. During the interval that direct ground is rcmoved from the test wiper 191 the cut off relay 200 in the line Switch C is maintained operated and the called line protected over a circuit extending from ground on release trunk conductor 106, armature 167 and its back contact, upper winding of the switching relay 184 back contact and armature 170, resistance R, test wiper 191, test contact 194, through the winding of the switchill ingrelay 200 and thencethrough the Winding of the motor magnet 202 to battery. During the'interval between the energization of*re ground on release trunk'conductor 106, ar-

mature 167 and its backcontact, upper winding of the switchingrelay134, baclccontact and armature 170,-resistance R. front contact and armature 181, armature 154; and its front- \back bridge relay 125 is opened and this contact, armature 141 and its back contact,

working contact of eff normal spring 1 and the said spring, and thence through the, release magnet 185 to battery. Owing'to the combined resistance of theupper winding of the switching relay'134and the resistanceeR therelease magnet 185 doesnot operate atflthis time. Theconnection has now been completed andconversation may take place between thecalling subscriber and called subscriber, talking battery being supplied to. the calling subscriber from the windings of the'iine relay 126 and to the calledsubscriber from thewin'dings of the back bridge relay 125. 1

When the conversation is terminated both subscribers will replace their receivers; Inorder to describeithis releasing operation-1t will first-be amumedthat the calling subscriber replaces hisreceiver before the called subscriber. When the receiver .is replaced line relay 126 is opened and this relay deenergizes therebyopening the circuit of the slow acting relay127. After the deenergization of the line relay 126 and before the deenergization of the slow acting relayll27 an impulse of current i issent to'the slow. acting relay 133. .Ground .is-thus momentarily removed from theireleasetrunk conductor 106 easbefore described,- but there1ease1. of the energization of relay 125 and prior to the deenergi zation of-relay-129 an impulse/pf connectorH does nottake place asthe circuit ofthe release magnetisopened at armature 135. TheselectonEand the line switch 0 are released in the same manner a-s was previously described upon. ground being removcd from tlie-xrelease trunk 106. When the called subscriber:finally hangs up the circuit of the slow acting relayi129 opened, 7 ground is removed from the test wiper 191 and thecircuit of i the release magnet 185 is completed. This circuit extends" from ground by Way of armature 142 and its-back contact, armature 143 andits back contact,

back contactand armature .1135, armature 158 and its' front contact, working contact of off normal spring '145and the. said springpand thence through the rclease magnet 185 to" battery Itwill be noted that after the deeilrrentis sent to the test relay 132.- The operation of relay "132 serves noparticular function at this tlrnet Other results ofthe opened and these relays deenergize. operation of the spring 189 controlledby the will removehis receiver and operate his calldeenergization of -relay125 are that thelockingcircuitsofthe relays 130 and 131 are The release magnet serves to open the locking circuit of the relay 134. In this manner all the apparatus is released.-

It will now be assumed that the called subscriber replaces his receiver before the calling subscriber. When thereceiver isreplaced at substatlon A theclrcuit of the relay deener'gizes. Upon deenergizing, relay 125, at armature 137 opens the circuit of the slow'acting relay 129, and before the deenergization of this latter relay sends an impulse of current to the test relay 132. The latter relay, upon energizing, removesone ground connection from the test wiper 191 at armature 167, at the front contact of this""- removed from the testwi per 191 the cut off relay200inthe line switchC deenergizes" and again connects the'line of the substation A to the winding of'theline relay 201- and at the calhngsubstationthe circuit of the to ground. Now when the calling subscriber hangs-up therelease ofthe connectionwill take place in a mannersimilar to that already described. However, should the call- ..ingsubscriber maintain his-receiver off the hook, and the subscriber*at 'substationA desire to make a call,the latter subscriber ing devicejin the usual manner. W'henthe receiver is removed at substation A a circuit is completed for the-line relay 201 of the line switch G in multiple with the back bridge relay 125 of theconnector H. Relay 125, upon energizing, at armature 137' completes a circuit which extendsfrom ground, by way of the said armature and its front contact,-armature 166 and its front contact, working contact of off normal spring 145 andthe said spring, and'thence through the 'windingof release magnet 185' to-battery.

Magnetl85 operates torestore the connector H to normal. Another result of the operationofthis magnetis that atarmature188 "ground is removed from the release trunk conductor 106 and the *holding circuit of the switching relay in the selector E and the relay 15 in the line'switch C is opened. h The selector E and line switch C are-restored to normal in the same manner as waspreviously described. In the connector H, since ground is removed from release trunk conductor 106 the locking circuits of the relays 132 and 134 are opened. Relay 134 dcenerthe slow acting relay 127.

gizes and restores certain circuits in the con nector H to normal and disconnects the switch wipers from their connections in the connector H. Immediately upon the deenergization of the relay 15 in the line switch C the line relay 16 is again energized and the line switch operates in the usual manner to select an idle trunk extending to a selector switch which in this case is the selector E. \Vhen the calling subscribers line is extended to the selector E, a circuit is completed for the line relay 52 thereof which immediately energizes to close the circuit of the slow acting release relay The latter relay energizes and completes the holding circuit of the switching relay 15 in the line switch. When the calling subscriber hangs up the line switch C and the selector E are released in the usual manner. Immediately upon the deenergization of the switching relay 50 of the selector E the circuit of the line relay 126 in the connector H is opened and this relay deenergizes to break the circuit of Upon the deenergization of relay 126 and before relay 127 deenergizes an impulse of current is sent to the slow acting relay 133 which operates to maintain ground removed from the release trunk conductor 106 for a short interval. Upon the deenergization of slow acting relay 127, the circuit of the slow acting relay 133 is opened and also the locking circuits of the relays 130 and 131 are opened. Immediately upon the deenergization of the relay 134 the circuit of the back bridge relay 1:25 is opened and this relay deenergizes thus opening the circuit of the slow acting relay 129 and sending an impulse of current to relay 132. The operation of relay 132 serves to maintain the circuit of the rotary magnet open so that it does not receive an impulse of current upon the deenergization of the line relay 126. Another result of the deen ergization of the slow acting relay 127 is that a new circuit for the release magnet is completed which extends from ground by way of armature 142 and its back contact, armature 143 and its back contact, armature 135 and its back contact, back contact and armature 176, working contact of OH normal spring 145 and the said spring, and through the winding of the release magnet 185 to battery. In this manner all the apparatus in the connector H is restored to normal. It will be remembered that when the selector E and line switch C were released by the removal of ground from the release trunk conductor 106, the line switch C immediately operated to again connect with the selector E and this selector is rendered busy. In the present system, the release of the selector E serves to free the connector H so this connector may be used again.

The above operations take place when the calling subscriber persists in holding his receiver off the switchhook after the conversation is terminated with the called party and that called party desires to establish a connection for himself. The operation of the system when another connection is desired with the called line by another subscriber while the connector H is still in engagement with that line will now be described. As will be remembered the connector H is standing in operative connection with the bank contacts 193-195, inclusive, of the called line. However, there is no ground potential present upon the test contact 194 and another connector similar to H may establish connection with this line. Upon so doing, ground is placed upon a multiple test contact accessible to the other connector switch and this ground then completes a circuit which extends byway of the test contact 194, test wiper 191, front contact, and armature 181, armature 154 and its front contact, armature 141 and its back contact, working contact of off normal spring 145 and the said spring, and through the winding of the release magnet 185 to battery. Magnet 185 operates to restore the connector H to normal and removes ground from the release trunk conductor 106. The latter operation causes the release of the selector E and the line switch C in the same manner as was described above. In the connector H the various relays are restored to normal in a manner similar to that already described.

Having fully described and ascertained the features of the invention, what is considered to be new and desired to have protected by Letters Patent will be pointed out in the appended claims.

\Vhat is claimed is:

1. In a telephone system, telephone lines, automatic selector and connector switches, means controlled from a calling one of said lines for operating a series of said selector switches and a connector switch to extend a connection to a called one of said lines, and means controlled by the removal, the replacement, and the subsequent removal of the receiver on the called line for releasing said connector and selector switches.

2. In a telephone system, telephone lines, automatic selector and connector switches, means controlled from a calling one of said lines for operating a series of said selector switches and a connector switch to extend a connection to a called one of said lines, and relays in said connector switch responsive to the removal, the replacement, and the subsequent removal of the receiver on the called line for releasing the selectors and connector used in the extension of the connection.

3. In a telephone system, an automatic connector switch, called lines accessible thereto, means for operating said switch into connection with one of said called lines, a relay in said switch for supplying talking current to the called line, means controlled by other connector extendsa connection ,to the, 45 first called hne fr,clos1ng said release 0117- 60 i 8. In a telephone system telephonelines,

said relay for placing 1a guarding potential on the-connected called line, and lmeans controlled by the deenergizationofsaidrelay for removing said guarding potential from 5 the connected called line while still main taining said-connector position.

4. i In a telephone system, an automatic connector switch, called lines accessible switch in operated a r thereto, means for operating said switch into connection with one of said called lines a relay in-said switch for su plying talking-i current to the connected ca led line, meanscontrolled by said relay for placinga guarding potential on th'e connected called line, i.

and means controlled by the deenergization of said relay for removingsaid guarding-- potential from the connected calledline. I

5. In a telephone system, automatic con- I nector switches, called lines accessible'there-i to, means for operating one of said switches. into connection withone of saidtlines, means in said switch for placing a guarding potential on the connected called line, means controlled by the replacement .of the re ceiver on the called line for removing said guarding v potential, and means operative when another of said connectors is operated into connection with said called line 'for releasing the-first operated connector switch;

6. In a telephone system, automatic connector switches, called, lines accessible thereto, means for operating ,one' ofsaid switches int-o connection with one ofsaid called lines,-

a testwiperaforv said switch,meansoperative to place a guarding potential on the connected called lineby way ofsaid test wiper, means" controlled: by the replacement 4 of the receiver on the connected; s called line for 40 ,nremovingathe saidguarding potential, a release magnet in said switch, a circuit for b said release magnet including the test wiper, of said switch, and meansoperative when an- ,1

cuit.

7. In a telephone system,- automatic connector switches, called lines accessible thereto, meansfor operatingone ofisaid switches into connection with one of said called lines,

a test wiper for said switch, means operative to placea guarding potential on ther connected called line by way of said test wiper, means, controlled by thereplacement of the ,receiver on the connected called line for,

removing the said guarding otential, arelease magnet for the said sw1tch, ,and, a cir-' cuit for said release. magnet. including vthe test wiper of said switch. a,

automatic selecton and connector switches, means including-1a series ofs=said selector switches and a connector. switch for, establishing a connection betweena calling and a 05 lcalled one of said-lines means controlled by the establishment of the connection for, -placing guarding potential on the connected called line, means controlled'by the replacement of the receiver at the substation on the called line for removingsaid guarding po tential, means for operating anotherflconnector switch into connection with said called line,-and means responsive to the establislh ment of said second connection for releasing; thefirst operated series of switches. I

9. In a telephone system, ansautomatic connector switch, called 111185 4 accessible thereto, means for operating said switch into 1 connection with a called line, an alarm-signal, anda means 1n said connector switch meansif said called line is open torprea 8U -operative independent of :said operating venting the release of said switch and for closing the circuit ofsaid alarm.

10. In a telephone system, an automatic connector switch, called lines accessible theret'o, means for operating said switch into i connectionwith a 'called line, said means including a linerelay, and a means insaid connector switch operative independent of said line relay if said called line'is open for preventing the release of said switch."

11. In a telephone system, telephone lines, 3 automatic selector and connector switches,

means controlled from a calling one of said lines for operating a series of said selector:

switches and a connector switch to extend a connection to a called one of said lines, means in said connector controlled from said calling line for controlling the release of oneor more of said selectors,=and means in said connector switch operative if: said i called line is open forpreventlng the release of said connector switch without interfering r with the release of said selectors.

12. In a telephone system,telephone lines,-

automatic selector and connector switches,

means controlled from a calling one of said lIIIBS for operating a serles of sald selector switches and a connector switch to extend a connection to a called one of said lines, means in said connector controlled from said calling line for releasing the selector which precedes the connector in said connection,

and means in said connector switch operative if said called line is open for prevents ing the release of said connector switchybut allowlng the release of said series of selector switches.

13. In a telephone system, telephone lines, I automatic selector and connector switches,

means controlled from a calling one of said lines for operating a .series of said selector switches and a connector switch to extend a said series of selector switches, and means then operative for preventing said connector switch from being seized for another call.

14. In a telephone system, a calling line, a trunk terminating in an automatic switch, 'alled lines accessible thereto, said switch having wipers for extending connections to said called lines. contacts for said called lines in said switch, means controlled from said calling line for seizing said trunk line and for operating said switch in accordance with the number of one of said called lines, and means independent of control over any conductor of said trunk line and operative it said line wipers are out of adjustment so that they do not engage the contacts of the said called line for preventing the release of said switch over said calling line.

15. In a telephone system, a calling line. a trunk terminating in an automatic switch, called lines accessible thereto, an alarm signal, said switch having wipers for extending connections to said called lines. contacts for said called lines in said switch. means controlled from said calling line for seizing said trunk line and for operating said switch in an attempt to establish connection with one of said called lines, and means independent of control over any conductor of said trunk line and operative if said line wipers are out of adjustment so that they do not engage the contacts of the said called line for preventing the release of said switch from said calling line, and for causing the operation of said alarm.

16. In a telephone system, a connector switch and means for operating it to connect with and signal a called line. a. release magnet in said connector, a circuit for said magnet, means for opening said circuit when the called line is connected with, and means operative only if the called line is conductive to signalling current for closing said circuit.

17. In a telephone system, a connector switch and means for operating it to connect with and signal a called line. a release magnet in said connector, a circuit for said magnet. means for opening said circuit when the called line is connected with. and means dependent on the continuity of the called line conductors for closing said circuit.

18. In a telephone system, a connector switch and means for operating it to connect with and signal a called line, a release magnet in said connector, a circuit for said magnet, means for opening said circuit when the called line is connected with, said means comprising a wiper connecting relay for.

nector normally controlled by the calling subscriber, means responsive auton'iatically when a called line is connected with for removing said releasing means from the control of the calling subscriber, and means for automati ally replacing said releasing means under the control of the calling subscriber in case the called line is in operative condition.

20. In a telephone system, means including an automatic connector switch for extending a calling line to any one of a plurality of other lines, releasing means in said connector normally controlled by the calling subscriber, means responsive auton'latically when a called line is connected with for removing said releasing means from the control of the calling subscriber, and a relay in said connector for testing the continuitv of the called line and for restoring said releasing means to calling subscriber control in case the test indicates that the said called line is in order.

21. In a telephone system. a connector switch and means for operating it to connect with a called line, an alarm. and means for operating said alarm in case the called line is grounded.

22. In a telephone system, a connector switch and means for operating it to connect with a called line. an alarm, and means for operating said alarm in case either conductor of the called line is grounded.

23. In a telephone system, means including a connector switch for connecting a calling and a called line. releasing means in said switch normally controlled by the calling subscriber, and means in said switch effective in case the called line is grounded for preventing the calling subscriber from operating said releasing means.

24. In a telephone system, means including an automatic switch for extendinL a connection to a called line. means in said switch for making the connected called line busy to other switches, and means for rendering the called line idle while the connection thereto is maintained.

25. In a telephone system, means including an automatic switch for extending a connection to a called line, means in said switch for making the connected called line busy to other switches, and means for rendering the called line idle while maintaining said switch in operated position.

26. In a telephone system, means including an automatic switch for extending a connection to a called line, means in said switch for making the connected called line busy to other switches. and means in said switch controlled by the called subscriber for rendering the called line idle while maintaining the switch in operated position.

27. In a telephone system, means including an automatic switch for extending a Jun connection to a called line, line and test wipers in said switch engaging the line and test contacts of said line when the line is connected with, means in said switch for placing a busy potential on said test wiper, and means for removing said potential while maintaining all said wipers in engagement with said contacts.

28. In a telephone system, means including an automatic switch for extending a connection to a called line, line and test wipers in said switch engaging the line and test contacts of said line when the line is con nected with, means in said switch for placing a busy potential on said test wiper, and means controlled over the called line for removing said potential while maintaining all said wipers in engagement with said contacts.

29. In a telephone system, means including an automatic switch for extending a connection to a called line, line and test wipers in said switch engaging the line and test contacts of said line when the line is connected with, means in said switch for placing a busy potential on said test wiper, and means in said switch controlled over the called line for removing said busy potential while maintaining said line wipers in engagement with the line contacts of said line.

30. In a telephone system, a connector switch for connecting a calling and a called line, said connector having restoring means under the control of the calling subscriber, and means controlled by the called subscriber for placing said restoring means under the control of a different calling subscriber.

31. In a telephone system, a connector switch for extending a connection to a called line, a second connector for connecting with the same line, and restoring means in said first connector responsive to the completion of the second connection.

32. In a' telephone system, a connector switch for connecting with a called line, said switch having a test wiper and a release magnet, means for placing a busy potential on said wiper when the called line is connected with, and means controlled over the called line for removing said potential from said wiper and for connecting the wiper to said magnet.

33. In a telephone system, an automatic switch, means including a line relay and a release relay for controlling the operation of said switch to connect with a desired line, a release magnet in said switch normally responsive to the deenergization of said relays, and means effective in case the line connected with is open for preventing said magnet from responding to the deenergiza tion of said relays.

34. In a telephone system, an automatic switch, means including a line relay and a release relay for controlling the operation of said switch to connect with a desired line, a release magnet in said switch normally responsive to the deenergization of said relays, means for removing said magnet from the control of said relays when the line is connected with, whether the line is open or closed, and means effective in case the line is not open for again placing said magnet under the control of said relays.

35. In a telephone system, an automatic switch, means for operating said switch to connect with a desired line, a release relay in said switch and means for maintaining it energized while the switch is in use, restoring means in said switch normally responsive to the deenergization of said relay, and means effective in case the line connected with is open for preventing said restoring means from responding to the deenergization of said relay.

36. In a telephone system, an automatic switch, subscriber controlled means for operating said switch to connect with a desired line, subscriber controlled means in said switch for controlling the release of said switch, and additional and independently operable means in said switch for controlling its release in case the line connected with is open.

In witness whereof, I hereunto subscribe my name this 14th day of April, 1925.

JOHN E. GARDNER.

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