US1249583A - Telephone-exchange system. - Google Patents

Description

J. L. WMGHT.

VELEPHONE EXGHANGE SYSTEM.

APPLICATION FILED DEC. 9, i912. 1L

H SHEETS-SHEET l.

J. L. WRIGHT.

Patented Dec. 11, 1917.

H SHEETS-SHEET 2.

J. L. WRIGHT. TELEPHONE EXCHANGE SYSTEM.

APPLICATION FILED DEC. 9 I912- LE%Q @@& Patented Dec 11, 1917.

I. SHEETS-SHEET 3.

J. L. WRIGHT.

TELEPHONE EXCHANGE SYSTEM. APPLICATION FILED DEC-9,1912.

I l SHEETS-SHEET 4.

J. L. WRIGHT.

TELEPHONE EXCHANGESYSTEM. APPLICATION FILED 050.9, 1912.

Patented Dec. 11, 1917.

H SHEETS-SHEET 5- RII'Y6 BHCK TONE BUSY TO/YE J. L. WRIGHT.

TELEPHONE EXCHANGE SYSTEM. APPLICATION FILED DEC-9,1912.

Patented Dec. 11, 1917.

n SHEETS'SHEET 6.

J. L. WRIGHT.

TELEPHONE EXCHANGE SYSTEM. APPLICATION FILED mac. 9. I912.

I 1 SHEETS-SHEET 7.

54/5 Y TONE Pateilted Dec. 11, 1917.

J. L. WRIGHT.

TELEPHONE EXCHANGE SYSTEM. APPLICATION FILED DEC-9.1912.

Patented Dec. 11, 191?.

H SHEETS-SHEET 8- J. L. WRIGHT.

TELEPHONE EXCHANGE SYSTEM.

APPLICATlbN FILED DEC. 9, 1912.

Patented Dec. 11, 1917.

H SHEETS-SHEET 9.

J. L. WRIGHT. TELEPHONE EXCHANGE SYSTEM. APPLICATION FILED 0150.9. I912.

Patented Dec. 11, 1917.

ll SHEETS-SHEET l0.

.1. L, wmmw. TELEPHONE EXCHANGE SYSTEM. APPLICATION FiLED DEC. 9 i952.

Pmmnibedl 1m 111,193?

I! SHEETS-SHEET I S- TAWW I arosnrn L. WRIGHT, or cLnvnLAnD, OHIO, assmnon, JBY MESNE ASSIGNMENTS, 'r

' JAMES R. GARFIELD, TRUSTEE, or CLEVELAND, OHIO.

. TELEPHONE-EXCHANGE SYSTlEM.

To all whom it may concern:

Be it known that I, Josnrnr- 1L. Wn onmr, a citizen of the United States, and resldent of Cleveland, county of Guyahoga, State of ()hio, have invented certain new and useful Improvements in Telephone-Exchange Systems, of which the followingis a specification.

My invention relates to telephone-exchange systems and especially to that class known as semi-automatic. -In systems of I i this class automatic switching mechanism is employed for efi'ecting connections between calling and called subscribers. The switch- 1 a as follows:

The method of calling or automatically picking out an idle trunk leading to a private branch exchange, or where subscribe-rs have'more than onetelephone, listed under one number;

i The method of trunking between exchanges whereinzthe switches are controlled entirely over two wires;-

The method of re 'stering or indicating the condition of tra 0 so as to show the number oftrunks in use, and also the number of lines waiting to become connected to trunks; g

Means controlled by the operator in case of false calls, or grounded lines, etc., so that such lines can be removed from the primary trunks and cleared back to the line equipment individual to the lines. This prevents tying up the trunking equipment. Only enough of this trunking equipment is ordinarily provided for taking care of the maximum number of connections.

In case of abnormal conditionswhen there are a large number of defective lines all of the primary trunks would become connected to such lines and prevent the legitimate calls receiving attention.

I have shown the various features applied to a semi-automatic system butit nat- Specification of'JLett ers Patent. Pattgmtmfl Mpg, 11L 11%11 Application filed December 9, 1912. Serial No. 735,810. 1

a full automatic system My invention is illustrated in the accompanying drawings wherein:

Figure 1 shows a subscribers line equipment, control circuit and meter device.

F1g. 2 shoWs a primary and first selector clrcuit. 1

3 shows a second selector circuit.

Fig. 3 shows a two-wire trunk for use between exchanges. y

Fig. 4 shows a connector circuit'equipped for party line selective rin 'ng.

Fig. 4 shows a private ranch exchange connector.

Fig. 5 shows the line and control circuits of the called subscriber.

Fig. 6 shows the key-set control circuit, the tlme element control device, and meter for registering the condition of the various trunks.

Fig. 7 shows the circuit of the operators key set switch and its associated shifting switch.

Fig. 8 shows an operators key-board and sending device.

Fig. 9 shows the arrangement of the various sheets when a subscriber calls for a line in the same exchange.

Fig. 1Q shows the arrangement of the sheets when a subscriber calls for a private branch exchange, or a subscriber who has more than one telephone. d

Fig. 11 shows the arrangement of the sheets when a subscriber calls for another subscriber in a difi'erent exchange.

Referring to Fig. 1, the subscribers stat1on at A is equipped with apparatus usual in common battery exchanges. The line wires from this station terminate at the central oflice in a line relay 2. The line relays urally follows that they can be applied to Y of the operators key-set switch one hundred lines and starts to rotate whenever a call originates and will continue to rotate until an idle primary switch is found.

12 is arelay'controlled by the operator for removing the line relay 2, and the cutoff relay 1. When this relay 12 is energized, it locks' itself through the subscribers telephone, or in case of rounded or short-circuited lines, this re ay will also remain energized. The action of this relay renders the line busy against other calls. When the line is cleared, or the circuit opened, relay 12 drops back and places the hue and cutoff relays in condition to perform their regular functions.

Referring to Fig. 2 primary switch C for picking out the calling lines is shown. This switch first rotates and will continue to r0- tate until the row wiper 64 picks out the busy row contact.

After this contact is reached the switch will cease rotating and step vertically until the individual busy test contact leading to the line relay 2 is found.

The first selector switch is shown at D, and responds to impulses from the sending device to rotate and then steps vertically to pick out an idle trunk leading to the second selector switch.

The wipers 63 of the switch C and wipers 56 of the switch D are joined as indicated by the heavy lines for conversational purposes. The tip and sleeve conductors are separated by the condensers 43 and 44. Relay 23 and the retardation coil connected respectively to the free and grounded side of battery supply talking current to the calling subscriber. 21 is the starting relay of the primary switch C, and corresponds to the line relay 2,. (Fig. 1,) as it controls the action 22 is the row test relay, while 24 is the individual test relay. 25 is operated when the key-set switch picks out the trunk and remains energized while the impulses are being transmitted. 27 is the test relay of the first selector D and remains energized while the test wipers 57 are passing over busy contacts. Relay 28 is energized whenever either therotary or vertical magnets of the switch C are operated, or when the vertical magnet of the switch D is operated. The circuits .of these magnets are normally completed through the back contacts of relay 28, and so, therefore, when it is actuated the magnet circuits are-broken. The action set up between the 'relay and the magnets .cause the latter to vibrate and step their respective switches.

The resistance coil 42 is placed in series with the rotary relay 29. This relay receives impulses from the sending device and operates magnet 34 causing the switch D to rotate. When the magnet 34 operates, it

(Fig. 7).

341, back to the callin closes its ass ciated contact springs and places ground between the coil and the winding of relay 29. This action shunts out relay 29 and serves to regulate its action, or as soon as the magnet. completes its stroke the relay which controls it is disabled. This arrangement avoids the necessity of fine adjustment between the repeating relay, the magnet and the sending device. This ground being placed to the winding at each impulse removes any static charge that may have accumulated on the impulse conductors.

Referring to. Fig. 3, the second selector switch at E is operated first in a rotary direction to pick out, the row, and then in a vertical direction to pick out the idle contact in the row. This switch is similar to the first selector switch shown at D and serves to pick out an idle connector switch. 81 is the repeating relay and is in series with the regulating coil 86. 82 is the interrupter relay corresponding to relay 28 (Fig. 2). 83 is the test relay, which is held energized while the test wipers of the switch E are passing over busy contacts.

Referring to Fig. 4, the connector switch G is provided with a set of wipers 390 which engage contacts leading to the tip and sleeve conductors of the called lines. The switch is also provided with a set of wipers 391 engaging contacts leading to the cut-off relays. This wiper also serves as a test wiper over which the condition of the called-for line is controlled. 305 and 310 are the repeating relays and respond to impulses from the operators sending device. Each one of these relays is in series with an individual regulating resistance coil. 315 is a control relay and serves to remove the relay 325 and the retardation coil 335 from the wipers while the switch G is passing over busy contacts. 320 is the tip battery supply relay and is actuated when the called subscriber answers. 340 is the ringing relay operated by the commutator 370 when the wipers of the switch G engage contacts of the called-for line. This relay is cut off by the action of relay 330 which-is controlled by relay 320 when the called subscriber answers. 345 is the busy test relay and is actuated when a busy line is found. Under these conditions, thls relay locks itself to ground through the test wire 306.. The action of this relay connects a suitable busy tone signal which is connected to thewwire subscriber, notifying him that the calledor line is busy. The action of this relaycloses the .circuit of the release magnet 365 thereby restoring the switch G. I

A controlling arty-line selecting switch is shown at F. he contacts and wiper of the portion J out on the generators 356, 357, 358 or 359 to either the tip or sleeve contacts f 1 ,aaatea of the ringing relay 340. The contacts and wiper of the portion I serve to restore the selecting switch to its normal, or. idle position-at the proper time. The contacts and wiper of the portion H serve to connect ground to either the tip or sleeve contacts of the relay 3 10. When the portion J connects generator to the tip contact, the portion H connects ground to the sleeve contact and .release the connector switch G after the called subscriber hangs up his receiver or when the calling subscriber hangs up, in case the called subscriber does not answer.

When theswitch F is in its normal 'position, the wiper of the portion H rests on the contact 334, thewiper of I on the contact 336, while the wiper of J, rests upon the contact 338. j

A suitable ring-back tone test is connected to the wire 392' which in turn is connected to the trunk back to the calling subscriber during each actuation of the ringing relay 34:0. This signal being connected in this manner notifies the calling subscriber that the party he called for is being rung.

The repeatingrelay 305 is regulated or controlled by the action of the vertical mag.-

net of theswitch G and also by the action of the stepping magnet 360 of the swltch F.

' Relay 310 is controlled or regulated by the action of the rotary magnet of the switch Gr.

Fig. 5 showsa subscribers station at AA connected to the regular line equipment and as the circuits shown are identical to that of and engage contacts leading to primary trunks over which the impulses are transn Fig. 1, they need not befidescriloed.

Referring to Fig. 6; the switch shown at Y corresponds to the switch W, Fig. 1) and serves to pick out an idle secon ary or keyset switch. 1

' The switch X is a time element control and comes into action when relays 130 and 132 have been held energized for an abnormal length of time. Relay 132 is energized as soon as an idle secondary switch is picked out, and should only remain energized long enough for the secondary switch (Fig. 31 to pick out thetenth contact in thetent row.. xThe magnet 77 causes 'the switch AX to ste whenever the contact springs 36 are close These'springs or contacts can" be controlled by any suitable timed. circuit closer-or the contacts can be located on the sending'machine. t

' We will assume that relayst132 and. 130 have been held energized beyond the time necessary for the secondary switch to perform its proper functions: 'When the wiper l 00 reaches one of the contacts connected to the wire 139, the circuit of relay 78 is closed through the contacts of relay 132. The switch X continues to step at each closing of the contacts 36 and when the wiper w reaches one of the contacts to which the relay 76 s connected, then this relay is operatedjand performs the following functions: Ground is connected to"'wire 149 through the wiper and contacts of the lower bank of the switch W, (Fig. 1) to Wire 60, operating relay 29 (Fig. 2) thereby causing the switch l) to take one step. Ground is also connected to wire 144 to the release magnet 166 of the secondary switch M, thereby causing it to return to its normal position. The wires 18 and 148 are opened thereby disconnecting,

relays 5 and 21. The falling back of this latter relay disconnects relays 130 and 132 (Fig; 6) thereby unlocking relay 7 8 and no further action takes place. r lit a calling subscriber is connected tothe primary switch C and a faulty connection takes place as just described, he-can upon hanging up his receiver'restore the switches C and D and originate another call.

The switch X performs no functions with regular connections, unless the secondary switch and the primary trunk should become tied up, whereupon this switch comes into play and releases the apparatus. a

Referring to Figs; 7 and 8, a secondary switch, operators key-board and sending device are shown. The switch M carries the wipers 167, 168, 169 and 162. This switch loperatesin the same manner as. switch C (Fig. 2) as it rotates first to pick out the group in which the calling. trunk is located, and then stops vertically to pick out the trunk in the group. The wipers 167 are connec'ted to the tip and sleeve side of the trunk mitted in order to operate the various 'se- .lector, and connector switches. .168 is the row wipe'r'and serves to pick out the group I of ten in which the calling primary trunk is located. Relay 154 is connectedto the in dividual test wiper and serves -to -pick out the particular :trunk in the group calling.

' Relay 156 is'the signal relayand is placed in-serie's with relay 25 (Figihf) when such a trunk isrpickedout. en relay 156 .is energized,..the'. circuits of the two lamps,

.243 and 2 14' (Fig.3) are .closed'and notifies .the operator ofa. call. 152 is the starting relay and corresponds to relay 21 (Fig. 2)

as it is e ergizedi'as soon as the switchY I picks out the switch M. 153 is-the-row test relay operated when the row wiper engages anactive contact. Relay responds when r v the operator presses the, answering button 248, thereby connecting her telephone set across the tip and sleeve conductors of the trunk. 157 is actuated when the operator presses the starting button 247. The action of this relay disconnects relay 155 and connects the starting wire controlled by the cam 231 to the stepping magnet 161, thereby causing the Wipers of the switch Z, shown at the portion N O and P, to rotate. The stepping magnet 161 is operated once at each rotation of the sending device and connects the impulse wires from the key-board in their regular order. The order in which these impulses are transmitted is: as follows: At the first rotation of the sending device, impulses corresponding to the thousands are sent over the tip side of the trunk, and at the second rotation a single test impulse is sent over the sleeve side of the trunk. At the third rotation impulsescorresponding to the hundreds are sent over the tip side of thetrunk and at the fourth rotation 21 single test impulse is sent over the sleeve side of the trunk. At the fifth rotation impulses to operate the selective party line switch are sent over the tip side of the trunk and at the sixth .rotation the tens impulses are sent over the sleeve side of the trunk. At the seventh rotation the units impulses are sent over the tip side of the trunk and at the eighth a single test impulse is sent over the sleeve side of-the trunk.

After all of these impulses have been delivered, then at the next rotation of the sending device, the wiper of the switch Z passing over the portion P closes the circuit of relay 158 which in turn causes the stepping magnet 161 to rapidly vibrate and cause the switch to rotate until it reaches its normal position. Just before reaching this position,

the circuit of the release magnet 166 of the switch M is energized thereby restoring the switch to its normal position. 7

Relay 163 corresponds to relay 28 (Fig. 2) and causes the magnets 164, 165 and 161 to vibrate and step their respective switches. The operators key-board shown in Fig. 8 consists of five rows of buttons, each row having ten buttons. Number one button of each row is connected to a contact, operated by the cam 232. Number two button of each row .is connected to a contact, operated by the cam 233. Corresponding buttons in each row are connected to the 'same contact. The

contact controlled by the cam 232 is closed just long enough to keep the relay 160, (Fig. 7) energized, while one impulse is being transmitted by the commutator 242. If

energized, impulses are connected to either the tip or sleeve side of the trunk, depending upon the position of the arm in regard to the contacts of the portion N.

The buttons, or keys, shown in the five rows R, S, T, U and V (Fig. 8) are of the usual locking and indicating type. When any one button of a certain row is pressed, it will release the button formerly pressed. The buttons 246, 247, 248, and 249 are of the non-locking type and the contacts controlled by them are only closed while the button is being pressed.

Referring to Fig. 3, the two-wire trunk selector, which in this instance is used as a second selector, is shown. The equipment shown to the left of the dot-dash line is located at one exchange, while the equipment shown to the right is located at another exchange. The trunk extending between the exchanges is composed of but two wires over which the impulses are transmitted and the release control exercised.

Relay 510 is slow acting and has its circuit closed by the action of relay 511. This latter relay becomes energized as soon as the trunk selector is picked out by the first selector. As soon as such a selectionis made, ground is connected to the test wire thereby energizing relay 511, which in turn closes the circuit of relay 510.

When the first selector switch is restored, ground is removed from the test wire and relay 511 falls back first, after which the slow I relay 510 has its circuit opened. After relay 511 falls back, and before relay 510 breaks its contacts, ground is connected to the tip and sleeve conductors extending to the distant exchange and also to the test wire leading to the contacts in the banks of the first selector switches. Ground being placed onthe tip and sleeve conductors at the same instant causes the release of the switch EE at the distant exchange. Ground being placed on the test contacts of the first selector switch renders the trunk busy for a sufiicient length of time for the switch EE to restore.

Referring to the equipment shown to the right of the dot-dash line, the switch EE is provided with wipers which engage the tip and sleeve conductors leading to connector switches and. also with a test wiper. This switch acts in the same manner as the first selector switch shown at D.

The two repeating relays 512 and 513 are connected respectively to the tip and sleeve conductors through the contacts of relays 502'and 503 and also through the contacts of relay 516. Relay 512 responds to the impulses from the sending device, and closes the circuit of the rotary magnet of the trunk selector EE while the action of relay 513 .closes the circuit of the test relay 514. The

action of the test relay closes the circuit of naaaaea the cut-ofi' relay 515 preventing clicks or interference while the wipers of the switch EE are passing over busy trunks.

At the first rotation of the switch EE and after relay 501 operates, the circuit of relay 516 is closed and maintained through the reslstance coil 520. The wire'joining the coil and the relay is connected to the test wiper ofthe trunk selector through the back con- 502 is operated, relay 512 will remain connected to the tip conductor of the trunk, until after the operation of relay 516.

Relay 501-is operated by relay 513 which in turn operates relay 503 thereby partially disconnecting relay 513 from the sleeve conductor. Relay 513, however, is also connected to the sleeve conductor through the back contacts of relay 512. Relay 503 has its circuit maintained and locked through the back contacts of relay 512.

Relay 512 responding to the set of impulses, which is to o erate the rotary magnet of the switch E remains connected to the tip conductor through the contacts of relay 516. Relay 513 responding to the test impulse. for stepping the switch EE vertically, remains connected to the sleeve conductor while the impulse is being delivered.

Relay 513, however, completes the circuit of relay 501 which in turn operates relay 516. The operation of relay 516 opens one path to the tip and sleeve conductors through'which the relays 512 and 513 respectively are connected. a

After all of the impulses for operating the switch lElE have been delivered and the firstimpulse of the set to operate the connector also operates relay 512, the first impulse of the set to operate the connector in operating relay 512 causes it to at once become disconnected from the tip conductor as relay 516 is now operated. At the next set of impulses sent over the sleeve side of the trunk to operate the connector, the relay 513 is at once disconnected.

' From the foregoing it will be noted that relays 512 and 513 only remain connected to the tip and sleeve conductors while the switch EE is being operated, but at the first impulse of the set belonging to the connector, they are at once disconnected.

When the calledsubscriber answers, ground is connected to the test wire at the connector switch with which the test wiper of the switch EE is in engagement. This ground shunts out relay 516, thereby placing the condensers in series with the tip and sleeve conductors of the switch EE. When relay 516 is energized these condensers are short-circuited so the impulses can pass throu h and operate the connector switch.

Re erring to Fig. 4 the private branchexchange connector is similar to the regular connector shown in Fig. 4. The impulses are transmitted in the same manner and in the same order. The private branch exchange connector is reached through the regular first and second selector switches. The main difference between this switch and the regular connector switch is that when the test relay 445 is operated instead. of releasing the switch, itsimply causes the circuit of the vertical magnet to be automatically interrupted. This action causes the switch to step vertically until the test wiper engages an idle trunk or line, whereupon the test relay falls back and the switch comes to rest with its wipers engaging contacts leading to an idle trunk.

Relays 405 and 410 are the repeating re lays which respond to impulses from the sending device. 415 is the control relay operated by relay 410 and serves to disconnect relay 425 and the retardation coil 435 from the wipers, while the switch is passing over busy trunks. Relay 420 and retardation coil 435 are connected respectively to the free and grounded side of battery and thus furnish talkin current to the called subscriber. 440 is the ringing relay which connects generator current of the frequency selected by the switch FF to the called line or trunk. Relay 425 is placed in series with the cut-ofi relay of the called line and when energized serves to connect the tip relay 420 to the tip conductor and also to close the circuit of the rin ing relay 440. 445 is the test relay operate by relay 405 when the test impulses are transmitted. This test relay when operated closes the circuit of relay'410 which in turn closes the circuit of'the vertical magnet of the switch GGr, causing it to step vertically until the test relay is released. This relay 445 is released when the wiper 491 engages an idle contact and as soon as such a contact is found, relay 445 falls back, releases relay 410 which disconnects the vertical magnet causing the switch GG to come to rest with its wipers resting on contacts of an idle trunk.

Lines appearing in the banks of the private branch exchange switch can also be multipled into banks of the regular connector switches. one of such lines can be called to predetermined numhers from the regular connectors, or the first idle one picked out through the private branch exchange connector.

With this arrangement any With such a switch as shown in Fig. 4, more than one private branch exchange can be located in the same row of contacts. An exchange having but three trunks can be connected to the lower set of contacts in'the bank. To call this exchange the last digit would end in one. A blank contact will follow the third contact after which a second branch exchange can become connected to the remaining contacts. In order to call the second exchange, it will be necessary to have the last digit of a number end in five.

The bank contacts can be split up or arranged in a manner to suit the number of trunk lines leading to private branch exchanges.

Under ordinary conditions there would be provided ten per cent. primary switches shown in Fig. 2 for serving a group of one hundred lines. These switches which first rotate in order to pick out a group of calling lines, is provided with a row test wiper Which engages a set of row contacts. There is a separate row contact for each group of ten lines, and it therefore follows that for one hundred lines, there would be ten row contacts. Associated with each row contact there are ten individual. test contacts. The primary switch C first picks out the group of ten lines through the medium of the row contact and then the individual line through the medium of one of the individual test contacts associated with the row contact; As soon as the switch C steps vertically, the row wiper moves with the switch spindle and leaves the row contact.

Each group of ten primary trunks shown in Fig. 2has a control switch Y for picking out an idle secondary or key-set switch. The test wir'es connected to the contacts of the Y switch are multipled to contacts in other Y switches, but the Wire 141 leading from a bank of the Y switch is individual to a row contact in the-key-set switch M and is not multipled to contacts of other Y switches. As soon as the switch Y picks out the switch M, ground is placed on the row contact oi the selected M switch only, thus preventing interference in case other Y switches associated with other groups of trunks are searching for key-set switches M at the same time. In no case is ground placed on more than one row' contact of any one key-set switch at the same instant. ,This method allows calls tocome in from different groups of trunks at the same time, without interference.

In Fig. 1, the switch W, however, is individual to one hundred lines and serves a group of .ten primary switches, or more, as the case may be. The row contacts of the primary switches of a particular group are multipled.

The percentage and grouping of the various switches can be increased, or decreased,

to suit traffic conditions. The operators are provided preferably with three key-boards, each key-board having its individual switch M.

The cams on the sending device (Fig. 8) shown at 230 to 241, inclusive, may be common to a group of key-boards. The com- Inutator 242, however. is preferably individual to one key-board or to one operator.

In the present instance I have shown the exchange, or exchanges, to be of ten thousand lines capacity and in case of a larger exchange, it would only be necessary to add additional selector switches and-additional rows of buttons to the operators key-board.

In describing the operation of my system, I will first trace a connection from a calling subscriber to another subscriber in the same exchange, using figures 1, 2, 3, 4, 5, 6, 7, and 8 arranged in accordance with Fig. 9.

The subscriber at A removing his receiver closes the circuit of the line relay which in turn closes the circuit of the group relay This latter relay operating closes the circuit of relay 4 which in turn connects ground to one terminal of relay 5 and also closes the circuit of the stepping magnet 7. The stepping magnet 7 operating closes the circuit of relay 6' which in turn opens the.circuit of the magnet causing it to vibrate and step around the wipers of the switch W. This switch will continue to rotate until an idle primary switch such as shown at C (Fig. 2)

is found. As soon as such an idle switch is of the rotary stepping magnet 31 by the fol lowing path: Battery B, 80, back contact of relay 24, 71, contacts of relay 28, back contacts of relay 22, 31, to ground. The operation of magnet 31, causes the primary switch C to rotate until the wiper 64 reaches a busy contact to which is connected wire 13, leading to the contact of relay 3.

circuit'of relay 22 is closed as follows: Battery B, 80, contacts of relay 24, 71, 22, 64, 13, contacts of relay 3 to ground. Relay 22 operating disconnects rotary magnet 31 and in its place connects the vertical magnet 30, thereby causing the switch C to step vertically until the busy individual test contact is found. As soon as this contact is reached, the circuit of relay 24 is closed as follows: Battery B, 24, 68, 67, 11, contacts of relay 2, to ground, through the contacts of relay 1. Relay 24 operating opens the wire 71 disconnecting relay 22 which, in fallin back disconnects relay 24 from the wire 6% 115 As soon as the row contact.,is found, the

and connects it instead to wire 66. Relay 24 is now placed in series with relay 1 and the operating of this latter relay disconnects the line relay 2, which in turn disconnects the group relay 3. The operating of relay 24 connects battery to the windings of relays 23 and 25. The falling back of relay 22 connects ground to the retardation coil 26. Battery is supplied through this coil and relay 23 to the calling subscriber for talking purposes.

Relay 21 remains energized until the primary switch C finds the calling line and until the key-set switch M finds the calling trunk. Relay 21 when first actuated connects battery to the relay 130 over the wire 79 and also connects battery tothe individual test contact of the switch M over the wire 62.

Relay 130 operating closes the circuit of the stepping magnet 133 of the switch Y. This magnet operating closes the circuit of the interrupter relay 134, which causes a vibrating cil'ect between the magnet and the relay,'and the switch will continue to rotate until an idle key-set switch is found.

When such a switch is found as shown in Fig. 7, relay 131 is placed in series with relay 152 (Fig. 7) by the following path: Ground, contacts of relay 130, 131, 138, bank contacts of Y, 140, 152, 195, cam springs 196,

-by causing the switch M to rotate.

197, to battery" 18 through the operators jack 400. I

Relay 131 operating connects battery to relay 132 causing it to operate. The operation of this latter relay places ground on wire 138 thereby shunting relay 131. This direct ground placed on the wire 140, which is. multipled to other Y switches, renders the selected key-set switch M busy against other calls. The operating of relay 132 also connects ground to the row contact of the key-set switch M by the following path: Ground, 139, bank contacts of Y, 141, to row contact, (Fig. 7). Relay 152 operating connects ground to the rotary magnet 165 through the back contact of relay 163 there- This switch will continue to rotate until the row 5e contact is found, whereupon the circuit of relay 153 is closed by the following path: Battery B, contacts of relay. 152, 176, 153, 171, 168,141, 139, contacts of relay 132 to ground.

The action of the key-set switch M is identical with that of the primary switch 0.

The operating of relay 153 disconnects the rotary magnet 165 and in its place connects the vertical magnet 164 thereby causing the switch M to step vertically until the busy individual test contact is found. As soon as this contact is found the circuit of relay ,154 is closed as follows: Ground, 154, 172, 62, 80, contacts of relay 21 to battery B. The operating of relay 154 disconnects relay menace 152, therehy cutting 0d the magnets and causing the switch M to come to rest with its wipers engaging contacts leading to the calling primarytrunk, (Fig. 2). Relay 152 becoming disconnected opens the circuit of relay 153 and this latter relay in falling back 4 through the contacts of relay 24. The op erating of relay 25 disconnects relays 21 and 5. The releasing of the latter relay frees the switch W, placing it in condition to pick out other primary switches.

Relay 156 operating connects battery to wire 181, 183, thereby lighting the two lamps 243 and 244, (Fig. 8). 'As soon as relay 21 (Fig. 2) became disconnected, battery was removed from the individual test contact of the switch M, thereby allowing relay 154 to fall back. The falling back of relay 21 also opens the circuit of relay 130 which'in turn opens the circuit of relay 132 and allows the switch Y to be used by other trunks in picking out other key-set switches.

The lighting of the two lamps 243 and 244 notifies the operator of a call and she then presses button 248 which operates relay 155. The operation of this relay con-" nects her telephone set across the tip and sleeve conductors of the trunk. The action conductors of the primary trunk and allowing the operator to conversewith the calling subscriber.

The operator after getting the proper number from the subscriber, presses one button in each row corresponding to the number desired, and then presses the starting button 247 which closes the circuit of relay 157 by the following path: Ground, 247, 186, 157, 193, 170, 169, 59, 25, to battery 18, through the contacts of relay 24. Relay 25 againoperating opens the trunk conductors to prevent the calllng subscriber hearing the impulses.

The operating of relay 157 disconnects relay 155, extinguishes lamp 245, and causes the guard lamp 244 to light. The action of relay 157 also connects the starting wire 189,

connected to the contacts operated by the cam thetrunk 150 through the contacts of relay 160 and the portion N of the switch Z.

If number nine button in the .row It is pressed, relay 160 will be held. energized by '29 (Fig. 2) by the ollowing v the operation of cam 240 until nine impulses impulses closes the circult of the rotary magnet 34,causing the switch D to rotate and bring its wipers in line with a group of contacts in the ninth row.

As soon as the springs operated by the retary magnet34 are closed, ground is at once placed between the winding of relay 29 and the coil 42, thereby shuntlng out relay 29. This relay in falling back removes battery from the winding of magnet 34 itself. It

will be noted from the foregoing that if the impulses from the sending device had been a. trifle longer, relay 29 would be shunted out, just as soon as the magnet 34: completes its stroke.

Ground being connected in this manner after each impulse serves to dissipate any static charge which may have accumulated on the impulse conductors.

After the rotary impulses have been sent the starting cam 231 causes the switch Z to take another step, thereby connecting the impulse wire to the sleeve side of the trunk 151. Relay 160 is now held energized by the action of cam 230 until a single impulse is transmitted. This impulse operates the relay 27, (Fig. 2) by the following path: Ground, 242, 191, 190, 192, contacts of relay 160, 198, N, 151, 167, 61, relay 27, earn springs 40 to battery B.

Relay 27 is operated upon receiving this impulse and is held energized thereafter by the following path: Battery B, contacts of' relay 25, contacts of relay 27, 58, contacts of relay 28, 72, 32, 75 cam springs 11 to ground. The cam springs-41 were operated when the switch D took its first rotary step. The operating of relay 27 cl0ses the circuit of vertical magnet 33 by the following path: Battery B, contacts of relay 28, 71, contacts of relay 27, 33 to ground. Magnet 33 in operating closes the circuit of relay 28, which in turn opens the circuit of the magnet 33 itself. The action of this relay and magnet causes a vibrating efi'ect and the switch D steps vertically. When the circuit of relay 28 is closed by the action of magnet 33, the circuit of relay 27 itself is partially opened, but it will remain energized by the test wiper 57 engaging ground or busy test contacts." While the relay 28 is operated and the wiper 57 comes to rest on an idle contact, then relay 27 will at once become deenergized and disconnect the vertical magnet 33, causing the switch D to bring its wipers to rest on contacts leading to an idle second selector.

The controlling of the test relay 27 in the manner described insures a full step of the switch as the wi )er 57 fully en ages a test contact before relay 27 is opened by the action of relay 28.

As soon as the switch D takes its first vertical step, or while in the act of taking this step, the cam springs 40 are opened, thereby disconnecting relays 27 and 29, respectively from the tip and sleeve conductors of the trunk.

At the third rotation of the sendin device, impulses corresponding to the amndreds are sent over the tip side of the trunk corresponding to'the button pressed in the row S. These impulses operate relay 81 of the second selector switch E (Fig. 3). This relay is connected to the tip side of the trunk 90 through the cam springs 88. The action of relay 81 closes the circuit of the rotary magnet 85 causing the switch E to rotate and bring its wipers in line with contacts leading to connector switches.

At the fourth rotation of the sending device, a single test impulse is sent over the sleeve side of the trunk operating relay 83. This relay in acting closes the circuit of the vertical magnet 81, causing the switch E to step vertically until the test wiper 102 engages contacts leading to an idle connector switch.

The test relay 83 is controlled in the same manner as the test relay 27 (Fig. 2) and the rotary relay 81 and the rotary magnet are controlled and regulated in the same manner as the rotary and vertical magnets of the switch D.

The action of relay 305 completes the circuit of the shifting relay 330 as follows: Ground, from the test wire 306, contacts of relay 305, 317, Winding of relay 330, 318 to battery B, from the back contacts of relay 320.

, At the first vertical step of the switch E, the cam springs 88 are opened, thereby disconnecting relays 81 and 83 respectively from the tip and sleeve sides of the trunk.

At the fifth rotation of the sending device, impulses corresponding to the button pressed in the row V, (Fig. 8) are sent over the tip side of the trunk operating relay 310 of the connector switch G (Fig. 4). The action of this relay closes the circuit of the stepping magnet 360 of the party line distributing switch by the following path: Ground, contacts of relay 310 321, contacts of relay 330, 323, 360, 318, contacts of relay 320 to battery B. The switch r takes a number of steps corresponding to the impulses delivered. In the present instance, I have shown generator 356 connected to the first two contacts in the bank J so that if either one or two impulses are transmitted, this same generator will become connected to the sleeve contact in the ringing relay.

Isa

antenna 1f six or seven impulses are transmitted the same generator will be connected to the tip contact of the ringing relay. The contacts are arranged in this manner becauseone of the party line frequencies is also used for straight or independent line ringing. We

will assume that five impulses have been.

vice, impulses, corresponding to the button pressedin therow T are sent over the sleeve side of the trunk operating relay 305. This relay operating unlocks relay 315 and closes the circuit of the rotary magnet 355 by the following path: Battery B, contacts of relay 305, 3161, cam springs 380, 316, 355, to ground. The operation of the rotary magnet causes the connector switch Gr to rotate and bring its wipers in line with a group of contacts containing terminals of the desired line.

At the seventh rotation of the sending device, impulses corresponding to the button pressed in the row U are sent over the tip side of the trunk operating relay 310 again.

Theoperation of this relay closes the circuit of the vertical magnet 350 causing the switch G to step vertically and bring its wipers into engagement with contacts of the desired line. The action of relay 310 again energizes relay 315, preventing interruption while the wipers are passing over busy contacts. When the switch G takes its first vertical step, the, cam springs 380 operate and .-disconnect the rotary magnet 355.

At the eighth rotation of the sending device, a single test impulse is sent over the sleeve side of the trunk, operating relay 305 again. This relay now operating connects the test relay 345 directly to the test wiper 391. 1f the called line is busy, this relay 345 will become energized and lock itself to ground through the test wire.306. The action of this relay connects ground to the release magnet 365 thereby operating it and causing the switch G to restore. The action of this relay also connects a busy tone {P01111116 Wire 341. to the trunk 301 notifying the calling subscriber that the called-for line is busy.

1n case the line is not busy relay 345 w ll not be effected. Relay 305 in acting again unlocks relay 315, which, falling baclr places the relay 325 in series with thecut-off relay of the called line by the following path: Battery B, contacts of relay 315, 312, 325,

311, contacts of relay 305, 303, 391, 107, outod relay to ground. The action of the cutofi" relay disconnects the line relay and the action ofrelay 325 closes the sleeve sideof the trunk and disconnects the'repeating relay 310. This relay also connects battery to the winding of the tip relay 320 and also closes the circuit of the ringing relay 340 by the following path: Ground commutator 3 70, 340, 326, contacts of relay 325, 324C, contacts of relays 33O and 315, contact of relay 330 322, vertical magnet 350 to battery B. The vertical magnet 350 does not operate in series with, the winding of the ringing relay 310. The action of this ringing relay connects generator 359 to the sleeve conductor 30 1 and connects ground to the tip conductor 302, thus ringing the subscribers bell AA at intervals. At each actuation of relay 310 a suitable ring-back test is sent over the sleeve side of the trunk notifying the calling subscriber that the called-for party is bein rung.

At t e next rotation of the sending ,device, relay 158, (Fig. '7) is connected to battery through the bank P of the switch Z. The action of this relay connects ground to thev magnet 161 and also unlocks relay 157. Magnet 161 will vibrate rapidly and cause the switch Z to rotate until the Wipers reach their normal position. Just before reaching this position the wiper of the portion T connects relay 158 in series with release magnet 166. The action of the release magnet causes the switch M to restore. This switch restoring disconnects the operators key-set from the primary trunk and renders it available for other calls. When the called subscriber removes his receiver during the non-ringing interval,

and the talking circuit throughout the various figures is indicated by the heavy lines.

When the' called subscriber hangs up his receiver, relay 320 falls back after which the circuit of the magnet 360 is closed by the following path: Ground, commutator 353, 1, 398, contacts of relay 330, contacts of relay 315, 321, contacts of relay 330, 323, 360, 318 tobattery 13, through the contacts of relay 320. Magnet 360 will continue to vibrate until the wiper of the portion 1 rests on the contact 336. Just before this contact is reached, the wiper at H closes the circuit of the release magnet 305 by the following path: Battery 13, 365, 332, H, 327, to ground through the contacts of relay 315. The no tion of the magnet 365 restores switch G to its normal position.

The calling subscriber hanging up his re-

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