US1169736A - Telephone-exchange system. - Google Patents

Description

F. SCH OENWOLF.

TELEPHONE EXCHANGE SYSTEM.

APPLICATION FILED 050.16, 1908.

3 8 Patented Jan. 25, 1916.

I1 SHEETS-SHEET 1.

N g T) M Q THE COLUMBIA PLANOGRAPH co., WASHINGTON, D. c.

F. SCHOENWOLF.

- TELEPHONE EXCHANGE SYSTEM.

I APPLICATION FILED DEC 16, I908. 1,1@9,36, Patented Jan. 25, 1916.

ll SHEETS-SHEET 2- THE COLUMBIA PLANOGRAPH 60.. WASHINGTON, D. c.

F. SCHOENWOLF.

TELEPHONE EXCHANGE SYSTEM.

Patented J an. 25, 1916.

APPLICATION FILED DEC.16, 1908- ll SHEETSSHEET 3- x v E H V W 7 v I H coLuMBlA PLAPfOGRAPH c F. SCH O ENWOLF.

TELEPHONE EXCHANGE SYSTEM.

" m Patented Jan.25,1916.

H SH'EETS-SHEET 4- THE COLUMBIA PLANOORAPH CO WASHINGTON, D- C.

F. SCHOENWOLF.

TELEPHONE EXCHANGE SYSTEM. 'APPILICATION FILED DEC. 16. 1908.

n SHEETS-SHEET 5.

Patented Jan. 25,

THE COLUMBIA PLANOORAPH ,C0., WASHINGTON, D. C.

F. SCHOENWOLF. TELEPHONE EXCHANGE SYSTEM. APPLICATION FILED DEC.16. 1908.

Patented J an. 25, 1916.

ll SHEETSSHEET 6.

THE COLUMBIA PLANOGRAPH 60., WASHINGTON. D. c.

F. SCHOENWOLF.

TELEPHONE EXCHANGE SYSTEM.

APPLICATION FILED 020.16.1908.

Patented Jan. 25, 1916.

I I SHEETS-SHEET 7- 11: COLUMBIA PLAl zOaRAPH cm, WASHINGTON, D. c.

F. SCHOENWOLF.

TELEPHONE EXCHANGE SYSTEM.

APPLICATION FILED 05016. 1908.

H SHEETS-SHEET 8.

F, SCHOENWOLF. TELEPHONE EXCHANGE SYSTEM.

APPLICATION FILED DEC-16, 1908.

Patented Jan. 25, 1916.-

II SHEETSSHEET 9- F. SCHOENWOLF. TELEPHONE EXCHANGE SYSTEM.

I916. u suzns-suan 1o.

Patented Jan. 25

APPLICATION FILED DEC-16,1908- THE COLUMBIA PMNOORAPH C04, WASHINGTON, DI c. I

magma,

F. SCHOENWOLF. TELEPHONE EXCHANGE SYSTEM.

APPLICATION FlLED DEC-16; 1908, 36. Patented Jan. 25, 1916.

ll SHEETS-SHEET ll- THE COLUMBIA PLANOGRAPH C0,, WASHlNGTON, D. C.

pivrrn s ra rns rnrnivr erosion.

FRED SCI-IOENWOLF, OF CHICAGO, ILLINOIS, ASSIGN OR, BY MESNE ASSIGNMENTS, TO KELLOGG SWITCHBOARD & SUPPLY COMPANY, A CORPORATION OFILLINOIS.

TELEPHONE-EXCHANGE SYSTEM.

Specification of Letters Patent.

Patented J an. 25, 1 916.

Application filed December 16, 1908. Serial No. 487,814.

To all whom it may concern:

Be it known that I, FRED SCHOENWOLF, residing in Chicago, county of Cock, and State of Illinois, have invented new and useful Improvements in Telephone-Exchange Systems, of which the following is a speci iication.

My invention is adapted for use in connection with automatic or semi-automatic systems and l have illustrated it as embcdied in systems of the former class.

More specifically, it has to do with what are often referred to as two wire systems, in that the signaling currents are transmitted by causing breaks in a metallic circuit so that the use of a third or common return crnductor, now commonly employed to permit signaling over the two sides of a metallic circuit separately, is not required. I am aware that the systems of this general character have hitherto been proposed and the present invention is found in the manner in which the transmission of the signaling currents is effected over the various circuits, in the combination of the circuits with the selective devices employed, and in certain arrangements provided.

The object of the invention generally is to provide a simple and efiicient structure of the character hereinbefore mentioned and more specific references will be made to the various features of the invention in connection with the detailed description, and in the claims.

Referring to the drawings, Parts 1, 2 and 3 of Fig. 1, when adjacently disposed, constitute a complete circuit diagram for an automatic telephone system embodying the invention. Parts 1, 2, 3 2111(14: of Fig. 2, when adjacently disposed, constitute a second complete diagram illustrating an autrmatic telephone system embodying the invention, employing selector mechanisms'of a character varying from those of Fig. 1.

' Fig. 3, Parts 1 and 2, when placed with Part 1 to the right of Fig. 1, Part 1, and 3, Part 2, to the right of Fig. 3, Part 1, constitute a third diagram showing a modified system embodying the invention. Figs. a, 5 and 6 are, respectively, a left elevation, a front elevatirn and a right elevation of a selector for use with the circuits of Figs. 1 and 3. Fig. 7 shows off-normal combina tions of said selector, and Fig. 8 primary adjusting mechanism thereof, Figs. 9 and 10 are respective top and side views-of se-- lector mechanism for the circuits of Fig. 2.

lectors at C, said last-mentioned contacts being for use when the line is a calling line. As calling lines, the lines are divided into groups of one hundred, and the contacts 23, 2t, of the lines of each hundred line group are multipled before the wipers 27, E28, 29 of a suitable number of line selectors C, say, ten per hundred lines. At the line selectors, the said contacts 23, 24k .25 are preferably arranged in ten groups of ten contact sets each, primary movements of wipers 27, 28, 29 in one plane being first effected to seek out the group containing the contact set of a calling line, whereafter secondary movements are caused in a second and intersecting plane to seekout the individual contact set of the calling line. Each sub-group of ten lines ofa hundred is provided with multiple common or group contacts 26 before a group selecting wiper 30 at each line selector; andfor each such subgroup often lines, a common relay 20 is provided, controlling, by its armature 21, the selectable condition of the multiple group c ntacts 26 of the sub-group of lines. Said relay 20 is rendered common to a sub-group of ten lines by the conductor 20 having ten branches, one to each line relay LR of the lines of the sub-group.

The line selectors C of a hundred line group are normally at rest; and on initiation of a call from any line, a master switch mechanism B is actuated to transmit a starting impulse to an idle line selector C which then seeks outv the terminals of the calling line. The master-switch B is common to the one hundred lines of its particular group, being so rendered by the common conductor 22 connected with a master-switch relay 22, said common conductor having one hundred branches, one extending to each line relay LR of the h nd d nes Each l ne se e tor the contacts 32, 34;, to seek out the contacts of C is provided with a set of stationary contacts 32, 3jat master-switch B, and the wipers 31, 33 are adapted, by virtue of'being mounted upon the customary rotary shaft 7 provided with a rotary ratchet for receiving thrusts of an armature-controlled pawl of magnet MM, to be driven step by step over an idle line selector C after the master-switch B has started a previously engaged line selector. As will more fully appear, the normalcondition of wipers 31. 33 is one wherein they engage contacts 32, 34: of an idle line selector C; Thus assuming-an exchange of ten'thousand lines, there will be one hundred groups of one hundred calling lines each.

Each such group will have its individual master-switch B and, say, ten line selectors C assigned to it, making a total of one thensandflineselectors. .Each line selector 0111 the presentembodiment of the invention has associated with it a first-selector D so that I there will be, inall, one thousand first selcc-- tors. The function of a first selector'is the usualone of being adjustable under substation control to select a group of multiple contact sets connected to second selectors assigned for connections to a particulargroup off lines, in the present case a thousand, whereafter its wipers 92, 93, 94: are automatically adjusted to select contacts of an idle second selector. I The function of a second selector in the ten thousand svstem now assumed is to select a group of multiple contact sets, terminals of connectors of the wanted hundred, and then to select the individual terminal set of an idle connector.

A connector is adjusted responsive to substation impulses to select a group of contact sets forming terminals of the lines of the tens group, co-ntain ng'the set of the wanted subscribeig and is then further adjusted responsii e to an additional set of impulses to select the individual multiple terminals of the Wanted line.

'tothe first selector D, the relay PR is an impulse relayladapted to be controlled by interruptions caused in the line circuit at the substation of. a calling line when such first selector has, by its associatedline selector 'D, been connected with the calling line.

Said relavPR is theon'ly're'lay ofth'e first selector directly influenced by the directive interruptions caused by the substation calling device, and said relay PR controls, by suitable electrical and mechanical connections, the primary adjustment of wipers 92, 93, 9i of first selector D to select the required group of multiple contacts 95, 96, 97. To initiate the secondary travel of the wipers 92, 93, 94:, a secondary relay SR is provided, constructed so as to be slow to release its armature when its circuit is interrupted. Its winding is connected tothe wiper 89, normally engaging the contact 87 and adapted to move over the contact projections of the bank segment 88, said wiper 89 accompanying the wipers 92, 93, 9i in their primary travel. As will be observed, the segment 88 is normally grounded at and for each primary step of the switch wipers the wiper 89 passes over a contact projection of 88- into an open circuit relation, so that with successive steps of wipers 92, 93, 94-, the wiper 89 is alternately grounded and ungrounded; and when the primary travel of the wipers ceases, the wiper 89 will be resting in one of its open circuit positions. As long as asubstation calling device is one ating, primary steps of wipers 92, 93. 9t, 89

will be produced with rapidity such that the wiper 89 will not rest in one of its open circuit positions long enough to permit the I armature of magnet SE to retract. lVhen, however, the calling device at the substation reaches normal and comes to rest, the wipers of first selector D, including 89, remain stationary an appreciable time, the armature of relay SR presently retracts and closes a circuit which initiates the secondary travel of the first selector D to select an idle contact set of the selected group.

In the second selector E, the primary adjustment of wipers 92 93 94 is also produced responsive to substation circuit iuterruptions actin on the primary relay PR at first selector D. For second selector E, a. secondary relay SR is provided having the associated wiper 89 the normal contact 87? and the contact segment 88", the whole coiiperating in a manner similar to that before outlined with respect to relay SR, and itselements 87, 88, 89, to initiate secondary travel of second select-or E after the primary adjustment has been completed.

At the connector F, the circuit changes requisite to shift the impulse wire L from the primary magnet PM to the secondary ma net SM at the proper time are controlled by a secon ary relay SR and an associated wiper 110, having normal contact 108 and the segment 109, in a manner evident from the preceding, it being understood that the wiper 110 travels with. the connector wipers l ial, 14-5, 146 during their primary adjustment. The same relay SR serves, when the secondary adjustment of the connector wipers is completed, to transmit the impulse necessary for the testing of the called-for line, said relay SR during secondary travel being controlled by the wiper 120 and the circuit connection extending through the segment 121. The wiper 120 travels with the wipers of the connector when they are stepped in their secondary direction. it will be observed that the socalled slow-release relays, which I have throrghout the diagram designated by SR, receive their energizing current at all times over local circuits so that none of them are at any time dependent for current upon the limbs of the telephone line. This is a preferred arrangement for the reason that the circuits of these relays can always be pro vided of certain definite fixed resistances, it being well known that when relays of this character are placed in circuit with sub scribers lines of diii'erent resistances and capacities, their certainoperations in the manner required cannot be absolutely relied upon.

Although I have illustrated the relays as provided with acoppershell about the cores to render them slow to release their armatures, it will be understood that I do not desire to be limited to the use of this method of construction for slowing up the retraction of the relays armatures, since the use of secondary windings for the same purpose is well known, as well as other commonly employed expedients, any of which will be within the scope of the present invention.

To describe the system embodying the invention mor in detail, and first referring to Fig. l, the equipment at substation S includes the usual transmitter, receiver, condenser and callbcll, and the usual switchhool: 1, adapted in the present instance to be raised to cut out the call-bell and complete the talking circuit when the receiver is taken down. A calling device l is also provided having the locking pawl 5 fastened to the armature of the magnet 2, whose winding also serves as the substation impedance coil in the usual. manner. The calling device l is represented diagramn'iatically as a rotary dish having teeth of insulating material and a notch engaged by the pawl 5. Said de vice 4 is for clockwise rotation by hand to bring a number of teeth, corresponding to r the digit to be transmitted, below impulse spring 3, so that, when released, the associated spring returns the dial to the normal point, whereby breaks are produced at con tact 3 in number corresponding to the number of teeth brought below said spring. Such breaks are employed for the directive adjustments of the first and second selectors nd the connectors; and by successive actuations of dial 4;, a calling subscriber is enabled to produce a number of sets of breaks in the circuit of line limb 6 to adj ust the on change apparatus to complete connection-to the wanted called line.

At the exchange, the line relay LR is provided having the functions, when operated, of grounding the multiple called contacts 8 at the connectors to render them busy, to unground the multiple calling contacts 23 at the line selectors to render them selectable, to operate the group relay 20 to unground the multiple group contacts 26 to render them selectable, and to operate the master-switch relay 22 to start the line selector C whose contacts said master-switch engages. Thus on removal of the receiver at substation S, current flows from ground through LB, 14, 15, 6, 3, the upper contacts of hook- lever 1, 2, 7, 18, to battery l3. Relay LR- then operates and, by armature l2, disconnects itself from the line and locks through contact 17 and over common wire 22 in series with relay 22, operating said relay which grounds the starting wiper 31. Armature ll grounds the multiple contacts 8, while armature 13 ungrounds the private contacts 23 and operates the group relay 20 by current over the common conductor 20, so that the armature 21 ungrounds the multiple group contacts 26 of that sub-group of ten lines in which the calling line S has its contacts 23, 24, 2-5.

The line selector C includes the primary relay PR, adapted to be controlled by the group wiper 30, and said relay controls the primary magnet PM which causes the primary adjustments of the wipers to select the sub-group. Further, a secondary relay SR is provided adapted to be controlled by the individual private wiper 27, which relay controls the secondary magnet SM by which the secondary adjustments of he wipers 27, 28,29 to select the individual contact set of a calling line out of a subgroup, are effected. The selector C also includes the primary oil"- normal (PO) switch contacts 36, 37, shifted from their normal position on the first primary movement of the wipers, and the secondary off-normal (SO) switch contacts 4%, 45, d6, shifted from their normal position, shown, on the first secondary movement of the wipers. Said PO and S0 contacts are restored to normal by the restoring operations of the wiper mechanism.

It will be seen that on the grounding of wiper 31 on the energization of relay 22 before mentioned, current will flow from ground through the engaged contact contact 37, primary relav PR to battery 13, and the operated relay PR attracts armature 39 to connect the relays winding, the group wiper 30, and armature 38 to complete the generator circuit of primary magnet PM which receives an impulse to advance wipers 27, 28, 29, 30 a primary step, so that the group wiper 30 engages the first multiple group contact 26, Thi first step shifts con-- group contact 26 is encountered.

tacts 36, 37 to their alternate positions, the opening at 37 breaking the, initial energizing circuit'ot relay Pit so that it now depends for continued enei'gization upon grounds encountered at successive group contacts 26 engaged by wiper 30. The multiple group contacts 26 or non-calling sub-' groups W-lll be grounded at the .armatures 21 of the respective group relays 20 so that in the present case the wiper 30, moving from contact to contact, w ll maintain relay energized so that magnet PM receives successive current impulses until the fifth As this pertains to the sub-group of the calling line S, whose group relay 20 is energized, it is ungrounded at attracted armature 21. Circuit through relay PR is'opened and its .armatures are retracted, whereof 38 prevents further impulses through magnet PM and the i rimary adjustment of the switch wipers'ceases. During the primaryadjust ment, the wipers 27, 28, 29 move from right to left below the edge of their contact bank anddo not engage any contacts. Circuit may now be traced from ground through normal contact 38, contacts 36, &9, -15, secondary relay SE to battery, which relay operates and, by armature a1, connects its winding through contact 52 with the individual private wiper 27. Armature 42 closes generator circuit through secondary magnet SM to ground at 50 and said magnet produces a first secondary step of wipers 27, 28, 29 upward to engage the first contact set 23, 24, 25 of the selected sub-group. This first step shifts the SQ contacts 4%, 4-5, 4:6 to their alternate positions, the shifting of contact 45 opening the initial energizing circuit of secondary relay SR which now depends for its continued energization upon grounds at contacts 2-3 of non-calling lines engaged by the wiper 27 as the wipers move step by step, engaging successive sets of contacts 23,245, 25. The relay SR will thus continue energized and magnet SM will receive successive current impulses, each impulse causing a step of the switch wipers until wiper 27 engages the contact 23 of the line circuit of the line S. As this is ungrounded as before explained, the relay SR will deenergize as soon as wipers 27 28, 29 reach the "contacts 23, 2%, 25 of said-callingline, and the opening of alternate contact as prevents further actuation of secondary magnet SM so that the switch wipers remain in engagement with the contacts of the calling line. v

To prevent premature closing'of circuit through release wire 54, relays PR and HR at D are operated when relay SR at first energizes by current from ground through re 64, 5s,47 i0, 51, is-is, 5c, 67, an to battery, the relay E35, by armature 62, looking itself to ground through contacts 70, 73,

normal contact 48, and to battery through relay RR. These extensions occur by virtue of the 1nakebefore-break spring combinations diagrammatically illustrated, without the armatures of relay PR being permitted to be retracted.

It will be seen that when the subscriber first removes his receiver, the magnet 2 is momentarily energized in circuit with line relay LR and the calling device 4; is consequently unlocked. This is for a mrment only, however, since as soon as relay LR is fully energized, it terminates temporarily, by the opening of normal contact 14-, the flow of current over the line. Obviously, while the line selector is making its selection, no current flows over the line, but as soon as such selection is completed and the circuit of relay PR." is extended to the line conductors, the magnet 2 energizes and with draws the pawl 5 so that the device 4- may be rotated by hand.

On the operation of cut-off relay said relay looks through contacts 19 16, 23-27, 52 and 4d to ground. Its armature 17 decnergizes relays LR and 22; and on the retraction of armature 11 of relay LR, the ground already traced to contact 23 is extended to the multiple private contacts 8 at the connectors, continuing them busy. Armatures 15 and 18 have disconnected rclay LR from the line so that it remains deenergized. On the retraction of armature 13, the group relay 20 de'nergizes and its retracted armature restores the unsclcctablc condition to the multiple contacts 20.

lVhen relay SR first deenergizcd as before described, the ground at normal c011- tact 50 was connected through normal contact i2 and the now closed contact 46 with the contact 34 oi. the particular line elector C at master-switch B, so that current i lowed through the selecting wiper 38, motor relay MB to battery, and said relay energizes to close generator circuit through motor magnet MM-via alternate contact Said incignet drives wipers 31, 33 step by step over the contacts 32, 34:, in search of the set of an idle line selector. Until such set is found, the wiper 33 will be engaging successive grounded contacts 34. and so hold the circuit MM so that the wipers 31, 33remain' in en the construction may be such that each contact set 32, 34- appears a number of times in a circular bank, the bank then being built up of a number of segments having dupli cate contact sets in them.

Relays PR and RR being now held up by current over the line, relay RR having by its armature 62 further established a locking circuit for itself extendin through contacts 70, 73 and 84, the subscriber at S actuates the dial land releases it four times, each operation resulting in a number of openings at 3 corresponding to the units of one of the digits of the called number. Each actuation of dial at causes a corresponding number of deenergizations of relay PR, while the relay REL continues energized because of its locking circuit. Assuming the called number to be 2345, the first set of breaks at 3, two in number, deenergizes relay PR twice. The first retraction of its armatures transmits an impulse from ground through contact 63, normal contact 60, contact 72, through primary magnet PM, to battery and over a parallel path through normal control -87 89, secondary relay SR to battery. The r sulting actuation of magnet PM brings wipers 92, 93, 94 adjacent tothe first group of multiple second selector contacts, and the wiper 89 is moved over the first projection of segment 88 to a between-contact position so that the circuit of secondary relay SR is open at wiper 89. The relay SR, being constructed to be slow to release its armature, is at this time prevented from releasing its armature because a second deenergization of relay PR occurs quickly, whereby another actuation of magnet PM is produced and the wipers 92, 93, 94: are moved adjacent to the second group of second selector contacts 95, 96, 97, assigned to the second thousand in the exchange. Wiper 89 movesv simultaneously across a second contact projection of segment 88 into the next open circuit position. In this step, it makes contact with the second projection of 88 for a moment and, as the projections are grounded at normal contact 85, current is again passed through relay SR before its armature has time to retract.

Since now the subscriber at S has to await the complete return of dial 4 to normal before selecting a new hold, and must then operate the device again, suflicient time elapses, while wiper 89 is on open circuit,

i for the relay SRto retract its armature-and for the resulting selection of an idle contact set 95, 96, 97, out of the selected group to take place before another set of deelnergizations of relay PR begins. On the de'c'nergization of relay SR, its retracted armature closes circuit from contact 85, through contact 71, contact (said contact, along with 7%, having been shifted on the first primary step) through busy relay BR to battery B, energizing said relay, which, by armature 81, connects itsell through normal contacts 77, 86 to wiper 92. Contact 82 completes a generator circuit for secondary magnet SM which will be successively actuated as long as the relay BR remains energized, each actuation of said magnet moving wipers 92, 93, 9t a secondary step to engage a dilierent contact set 95, 96, 97, until the set of an idle second selector is encountered, wiper 89 at this time remaining at rest. The multi ple private contacts 95 of busy second selectors E will be grounded, and as wiper 92 passes over such busy contacts, relay BR will have successive locking circuits es tablished through it and will remain energized. As soon as an idlethat is, un-

grounded-contact 95 is engaged by wiper 92, relay BR will necessarily deenergize, since the secondary oil-normal, SO, contacts are shifted on the first secondary step, at which time the original energizing circult of relay ER is opened at 71. On the deenergization of relay BR, further actuations of magnet SM are prevented and the wipers 92, 98, 94 remain engaging the contacts 95, 96, 97 of the selected idle second selector. The retraction of armature 811 immediately places ground on the private contacts 95, rendering the selected contact set busy to other first selectors D at which it may have multiples. During the secondary selection, the locking circuit of relay ER is opened at contacts 73 and 83, so that the relay depends for its energizing upon current which will be flowing over the line circuit extending to S. As soon, however, as the talking circuit, indicated throughout the drawings by the heavily marked conductors, is reestablished at contacts and 83 on the deenergization of ER, a locking circuit for relay HR is extended through contact 83, contact 9l97, 78 and to normal contact St at second selector E.

The subscriber at S will now actuate dial 4 to cause three breaks at 3, resulting in three deenergizations of relay PR and the transmission of three impulses from ground and at contact 63, over wire L, contact 80, contact 9396, contact72 and in parallel through magnet PM and sec; ondary relay SR At E, the mechanism and circuits are "its ' substantiallylikethose of "first selector D, and. like parts at E fhave been given reference characters corresponding to those at D, except that exponents are added. The .5; operations of the second selector E to select the third group of contact sets of con- 'nectors, those assigned for connections to lines 2300 to 2399 inclusive, the-selection of an idle contact set 101, 102, 103, out of the group and the placing of a busy ground upon the private contacts 101 of the sei lectcd connector, F, will be sufiiciently plain from the description of the operation of the "first selector. 'When the selection of an idle connector F has been completed, the wipers 92 93 9-1 will be at rest engaging contacts 101, 102, 103 ofthe selected connector; and the relay RE which, during the secondary selection by switch E, had its locking circuit opened and wasenergized by current over the closed calling line circuit, will have a locking circuit established extending through contacts 94:97, 9i 103, to ground at 106. The subscriber at S now actuates thedial ft to cause four breaks at 3 and four deencrgizations of relay PR occur. The. resulting impulses from ground I at 63 traverse contacts 93-96 and 93-102, contact 112 and magnet PM to battery, the 30 four resulting actuations of said magnet causing four steps of wipers 1 14:, 1 15, 146 to select the fourth group of multiple terminals 8,9 and 10. A further effect of the actuations of magnet PM is to step wiper 110 across four contacts of segment 109 to a position between the fourth and fifth contact projections. The first impulse energizing magnet PM ,fiowed in part through contact 108110, relay SR to battery 13 so that said relay became energized and, because 'of its slow'release character, remained energized While the wiper 110 was making its steps across the contact projections of segment 109, which segment is grounded at normal contact 119'. During the three breaks nowbeing madeat contact 3 at S, following the first one, a locking circuit for relay BB is continued,'extending as before to conductor L of switch F, but now 50 completed through alternate contact 115 and to ground at 119.

[After the fourth primary step of connector F, sufiicient time will elapse before the subscriber at S can operate and release his calling device, for relay SE to denergize (Wiper 110 being on open circuit) and the following circuit changes are produced. The closure of normal contact 115 connects ground at 119 through contact 107 (the primaryoff-normal switches beingshifted on the first primary step) through normal contact'113 and sectndary magnet SM to bat Lt.ery, .whereby a first secondary step of wipers 14-41, 1415, 14-6 will be produced to .bring them. to 211111 315 0 1 fl ie nt t but not in contact with, the first contact set 8, 9, 10 of the selected group. To this end, the position of the wipers of the connector, after adjustment to select a group, is two steps distant from the first set of the selected group. By this first step, the secondary off-normal SO contacts are shifted, the change at contact 113 disconnecting magnet 8M from armature 115. The first actuation of magnet SW1 mentioned also moves wiper 120 one step to engage the first contact projection of the segment 121, whereupon circuit was completed from ground at contact 119, through contact 121120, normal contact at 125, and locking relay LOR to battery, which relay energizes andclcses alternate contact 125, whereby said relay is locked through contacts 130 and 116 to ground. On the attraction of armature 126, ground through 1l9120 is extended to the secondary relay SR, which again encrgizes. When now the calling device at S is actuated to cause five breaks at 3 and five denergizaticns of relay PR, five impulses will flow from ground at 63 over wires L, L L through alternate contact 123 and secondary magnet SM causing five actua- 'tions thereof and five secondary steps of wipers 14: 1, 145, 1-16, after which said wipers will rest engaging the multiple contacts 8, 9, 10, of line No. 23-15, which extends to substation S. During such secondary adjustment, wiper 120 travels and secondary relay SR is having its circuit alternately closed and broken at the contact projections of segment 121; and at the end of the last step, the wiper 120 will be between the fourth and fifth projections of the ring and the circuit of relay SR will be opened long enough so that its armature will retract. During the secondary adjustment of connector F, the relay RR at D is held energized by a locking circuit extending through alternate ccntact 115 to ground at 119. On the present deenergization of relay SR the closure of normal contact 115 connects ground at 119 through alternate contacts 107, 113, 124, with the lower winding of test relay TR, momentarily energizing it. This circuit is, however, immediately broken, since the attraction of armature 130 of relay TR opens the locking circuit of relay LOR and contact 124- opens. By the attraction of armature 129 of relay TR, said relay is connected to wiper 14 1 now engag- 1 ing multiple contact 8 of the called line, for the purpose of testing said line. If said line is idle-the condition illustrated in Fig. 1-- battery B is, through cut-oil relay CO and normal contact 11, alone connected with contact 8; and since the upper winding of relay TB is also connected to battery B said relay de'e'nergizes and its armatures retract, the closure of normal contact 129 closing a circuitfrom ground through ringing control relay RCR, normal contact tacts 111, 118, 129, 1448, l1, cut-off relayi armatures, opening the normal battery con-f nections of the called line, while the attraction of armature 16 "connects the ground, traced from relay RCR, to the multiple private contacts 23 at the line selectors, continuing the called line unselectable there. 'ihe attracted armature 134 of relay RUR- connects constantly rotating interrupter I through contact 139 with generator relay GR and battery; and as said interrupter revolves, relay GR is aternately energized and deenergized, connecting and disconnect ing ringing generator with and from the called line to periodically ring its bell, the ringing current passing out over line limb 6, through condenser and bell at the substation, returning over line limb 7, contact 10-146, and coil 12'? to ground. When the called subscriber answers and the armature 137 is retracted, the answering relay AR operates by current from battery B through contact 133, normal contact 137, 145-9, over line limb (3, contact 3, transmitter and raised hook-lever at substation S, impedance 2, line limb 7, contact 10-146, contact 135 to ground. Upon the operation of relay AR, armature 131 actuates closing relay CR, which, by armature 1.40, locks'to ground at 116 and, by armatures 138 and 143, completes the talking circuit at the connector, whereby the ground traced through coil 127 and over the limbs of the called line is eX- tended over wire L to the left, conductors L and L, alternate contact 60, release-relay BB to battery, whereupon relay R11 energizes and its armature 68 operates reversing relay RV which, by armature 65, looks to ground over wire 53 and over a branch to ground at contact 74. By the attraction of the armatures of relay RV, the connections of battery B to the calling line are reversed, this reversal being useful when it is desired to employ any of the well known polarized auxiliary service devices in association with the calling line.

The two subscribers S and S are now in conversation, their transmitters beingenergized by current transmitted from the central ofiice through coils PR and RR for S and coils AR and 127 for S, W hen they finish conversation, they replace their re ceivers, openingthe conductive circuits at the respective substations. 1f subscriber S does so first, all the switches are restored except connector F, which remains to be restored by subscriber S. If subscriber S hangs up his receiver first, all the switches are restored except line selector C, which re mains to be restored by subscriber S. Assuming subscriber S to first replace his receiver, the circuit through relays PR and 122, con-l' fiRR will be opened and both relays willdenergize, since at this time there is no locl ,ing circuit completed for relay RR. On their deenergizations, their armatures retract and the release Wire 54 has ground through relay R at D connected to it and current will flow thereover through said relay R and through contact 44 at G, traversing the lower winding of release relay RR, which relay will operate and, by armature 49, energize release magnet RM, which withdraws the retaining pawls of line selector C so that said selector automatically restores to normal, the relay SR being held energized by current to ground at alternate contact 50 during restoration so that the wipers 28 and 29 will be on open circuit. On the restoration, the opening of the off-normal contacts will de'e'nergize relays RR and SR and magnet RM. When selector C begins to restore, the cut-ofi relay C0 of line S will deeenergize and its line circuit A will be restored to normal. On the operation of relay R at D, said relay, by armature 76, locked itself in series with busy relay BR, the joint operation of said relays, by closing alternate contacts 82 and 79, actuating the release magnet RM, on whose energization the first selector 1) restores to normal, whereby the opening of its off-normal contacts will deenergize the relays BR, RR, RV, and magnet RM. defore magnet RM had time to energize, an impulse of current flowed from battery B through alternate contact 77, contacts 86, 9295, 74, relay R and said relay energized, locking itself in series with relay BR, and the second selector E restores on the consequent actuation of release magnet RM2 in the same manner that first selector D restores. When now subscriber S replaces his receiver, the circuit of relay AB is opened; and on its deenergization, the closure of contact 132 passes current from battery B via attracted armature 142, relay R to ground, which relay energizes and, by armature 116, actuates release magnet RM which restores the connector F, the shifting to normal of whose ofi-normal contacts will deenergize the various relays. 1f subscriber S were first to replace his receiver, connector F would be restored as ust described. In the present case, the opening of the conductive circuit through the substation will deiinerg-ize the release relay RE at D, on whose deenergization current from battery B will flow, through normal contact 69, contact 66, relay R to ground, operating said relay, which will result in the release and restoration to normal of first selector D and second selector E as before. The line selector C remainsto be restored by sul scriber S. Let it now be assumed that when connection was made therewith, the called line was busy. In such case, ground, traced through release control relay RCR of some matically restore, as before described.

other connector F, will be connected to the multiple contacts 8, or ground at the line circuit A, or at some line selector C, which has already selected the line S, will be connected to said contact 8. In either case, the presence of ground upon the engaged contact 8 will cause the test relay TR to remain operated on its initial 'energization, whereby the busy interrupter I will remain connected to the upper talking conductor via attracted armature 128, and the calling subscriber will receive the busy signal and will accordingly replace his receiver. When he does so, his act will deenergize relays PR and RR, and switches C, D and Ewill all autlon the present instance, connector F also restores as follows: When relayR at E energizes, itsarmature 77 will cause an impulse of current to flow from battery B through contact 86 before the magnet R11 has time to open said contact, thence through contact 92"-101, contact 104, normal contact lll,

7, relay R 'to ground, which relay will energize and will restore the connector F by closing circuit through release magnet RM 'One featureof the present invention is found in the way the operated switch mechanisms are restored in case the calling subscriber replaces his receiver before all the sets of switching impulses are transmitted. Assuming the calling subscriber replaces his receiver before a line selector selects his line,

the selection will take place nevertheless be-' cause line relay LR is locked. The relay RR will have operated and will have locked to ground at 84. As soon as cut-otf'relay C0 of the calling line energizes, the relay PR will be deenergized, since no conductive circuit is extended for it through the substation. On its deenergization, a single impulse will be transmitted through magnet PM and first selector D will select its first group of terminals, whereupon relay SR will retract its armature in an obvious manner and initiate secondary travel of firstselector D by energizing relay BR. On the first secondary step, the locking circuit of relay RR will be opened; and since the substation line circuit is also open now, relays PR and RR will have their armatures retracted simultaneously, whereby relay R at D and HR at 'C will have their circuits closed through contact 59-61 so that the selectors C and D will both automatically release. Like release operations will occur if the calling subscriber replaces his receiver after his line has been selected, but before transmitting any impulses.

If the calling subscriber transmit the first set of impulses so that line selector D selects a second selector E of some group, and then replaces'his receiver, the second selector E will make one primary step and then commen'ce its I secondary travel, whereupon; the

locking circuit of relay RRtraced now through secondary off-normal contact 73, will be opened and relays RR and PR will have their armatures simultaneously retracted, the release of selectors (J, D and E proceeding in a manner obvious from the preceding description.

If the calling subscriber were to transmit two impulse sets so that selectors I) and E were caused to operate to connect through to a connector F, and then replace his receiver, obviously the connector F would make one primary step, whereafter the secondary relay SR would be deenergized as before, whereon the opening of alternate contact would deenergize relay HR at D and the selectors C, D, E and F would release as in the case where the called line was found to be busy.

In Fig. 2, I have illustrated my invention, a

hereinbefore described, as applied to a system using a different class of mechanical switches; and as the operation of the telephone system as a whole, and the application of the features of the present invention is considerably like that before described, a brief reference to the said Fig. 2 will be sufficient. In Fig. 2, the arrangement of the substations S and S are substantially like those in Fig. 1, although the line circuits A are somewhat different. The lines as calling lines are in this case provided with multiple calling contacts 150, 151, 152, at a number of line selectors C, and with multiple called contacts 8, 9 10 at a number of connectors s F. In addition to the switches of these classes, a first selector is indicated at D and a second selector at E. The arrangement of the selectors and the connectors, their general functions, and the trunk arrangements between them, are substantially like those of the classes of switches of like name in Fig. l and need not be more specifically referred to. In the mechanical switches employed for selectors and connectors in Fig. 2, each group of multiple terminal contacts is provided with a separate set of wipers. In Fig. 2, the selection of the group is effected by providing what may be called a primary set of wipers which has before it nonmulti- ,1};

ple terminals, one set being connected with each of the sets of wipers which are assigned to the different groups of multiple terminals. Thus for example, in Fig. 2, Part 1, the line selector C will comprise ten groups of multiple contact sets 150, 151, 152, each set having a separate wiper set a, Z), c, of which two sets only are indicated. Each such wiper set is shown connected with short conductors with its individual contact set 153, 154;, 155, before the primary wiper set d, c, f, of the line selector C. In order to select the calling subgroup of lines, the wiper set d, c, f, and the group wiper g are clockwise rotated under the influence of primary magnet PM until they engage the contact set 153, 154, 155, ex tending to the wiper set of the subgroup containing the calling line, at which time the wipers g will be engaging the multiple group contact 156 of that subgroup, which contact will be on open circuit and will ac cordingly stop the travel of the primary wipers. Then, under the influence of secondary magnet all the sets of secondary wipers a, b, c, oi: all subgroups Wlll be caused to travel over their associated contact sets.

The wiper set previously selected by the primary wipers will be the only one not on open circuit, and, under the influence of its priv-ate wiper 0, will select the individual contact set of the calling line. This method of selection of the group and then of contacts from the group, involving the use of a secondary wiper set for each group of contacts and a set of primary wipers to pick'out' the group by selecting the secondary wiper set for that group, is employed throughout the first selectors D, the second selectors E and the connectors F.

Assuming the calling subscriber S desires to ccnve with subscriber S whose number will be assumed to be 2221, subscriber S first removes his receiver, operating line relay LR whose armature 13 ungrounds the private multiple contacts 152 and operates the group relay which ungrounds the multiple group contacts 156. Armature 11 places busy ground upon the private multiples 8 at the connectors, while armature 12 locks relay LR in series with the common master-switch relay 22 to start an idle line selector G. The attracted armature of relay 22 closes circuit from ground at normal contact through starting wiper 31, contact 3 of the engaged idle line selector, its primary off-normal contact-162, through contact 171, the relay PR to battery, actuating said relay PR, which closes an actuating circuit for magnet PM, under whose influence the primary wipers are rotated step by step. Armature 157 connects relay PR to the group primary wiper 9 so that as long as said wiper passes over group contacts 156 of non-calling sub-groups, it will establish successive lccking circuits for the relay PR, holdingsaid relay continuously energized. On the first step of the primary wipers, the primary oil-normal PO contacts are shifted, whereby the opening of contact 162 renders relay PR entirely dependent upon the wiper As soon as said wiper engages the ungrounded group contact 156, relay PR accordingly deenergizes and operates secondary relay SR- by current through contact 17:1',-159 to ground at 161.

By armature 165, relay SR now completes an actuating circuit for secondary magnet SM which steps the wipers a, b, c, in search of the individual contact set of the calling line, Until the selected wiperc engages the,

multiple contact 152 of an unselected calling line, relay SR will have successive locking circuits extended for it extending through normal contact 169, alternate contact 166, contact f-155, and through Wiper 0 to ground at successive engaged contacts 152. As soon, however, as wiper c engages the contact 152 of the calling line, the ungrounded condition of said contact will doenergizerelay SR, whose armatures will retract, preventing further actuations of magnet SM, the conductors L, L being at this time extended through to the talking con tacts 150, 151 of the calling line. On the initial operation of relay SR, alternate contact 164 was closed to conductively bridge wires L and L and to operate relays PR and RR at D before the secondary offnormal SO contacts were shifted, which shifting occurs on the first step of the secondary wipers, whereby contact 174 is opened to render relay SR solely dependent upon the circuit extended to the selected wiper 0. By this means, a premature oper ation of release relay HR is prevented. On the retraction of armatures 163, 164, battery through relay PR is, through the firstmentioned contact, connected with cut-oil relay C0 of the line, which relay, by armature 19 locks over contact 152-6, 155- contact 166-168, to ground at contact 175, which ground now maintains contact, 152 busy. Armature 18 extends the circuit of relay PR over the calling line, through magnet 2, unlocking the calling device and returning over conductor L through relay RR without permitting any retraction of the armatures of said relay PR. When relay RR first energized, its armature 1S9 operated the secondary relay SR whose attracted armature 202 closed the locking circuit for the relay RR extending through contact 192,.to ground at 213. 11611 now subscriber S causes the first set of two breaks at contact 3, each deenergization of relay PR will transmit an impulse from ground through contacts 189, 185, 193, 210, and winding 215 to primary magnet PM, which magnet will drive primary wipers g, it, 2'- and 89 two counterclockwise steps. Although wiper 89 at the conclusion of each step will have passed over one of the contact projections of the grounded ring 88 and be on open circuit, the relay Sit owing to its slow release character, will not deenergize until the completion of the second step whereby, during the transmission of the primary adjusting impulses, the relay BB has its locking circuit maintained closed. The first primary impulse flows in part through the locking relay 198 which, by armature 200, looks to ground over the wire 183 and,

by armature 201, prevents premature operation of primary release relay PER, which would otherwise energize when, on the first

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