US1609616A

US1609616A - Telephone system

Info

Publication number: US1609616A
Application number: US510016A
Authority: US
Inventors: Herbert M Friendly
Original assignee: Individual
Current assignee: Individual
Priority date: 1921-10-24
Filing date: 1921-10-24
Publication date: 1926-12-07
Anticipated expiration: 1943-12-07

Description

Dec. 7 1926.

H. M. FRIENDLY TELEPHONE SYSTEM 3 Sheets-Sheet 1 Fiql Inventor Herb ert-P'I-Friendh MN. Ill.

3 Sheets-Sheet 2 Inventor HE Pb erfl ffiliq JL I H. M. FRIENDLY TELEPHONE SYSTEM origin-a1 Filed Oct. 24. 1921 NWN nmw w new mom mow \MN NW 7 WN nhu m MN n. ll. mwfi QHN W\N H N a U 1 Now M mu @m w wan mm .*NN IL Dec. 7 1926.

I'll I I NM \NM l EN NnN 3N &

Dec. 7, 1926. I 1,609,616

H. M. FRIENDLY TELEPHONE SYSTEM original Filed Oct. 24. 1921 3 Sheets-Sheet 5 3L m [\J Patented Dec. 7, 1926.

- UNITED STATES J 1,609,616 PATENT OFFICE.

nannaar it. FRIENDLY, or cmoaeo, rumors,

TELEPHONE SYSTEM;

Applloatlon illed October 24, 1921, Serial No. 510,016. Renewed April 27, 1926.

The present invention relates to automatic telephone systems in which selector switches are'employed. More specifically, the invention relates to an improved method-and aparatus whereby mechanism of selectors can dispensed with, and ap aratus units involving essentially the disp aced mechanism provided for temporary association with the selectors so that when a selector is seized,

it, in efiect, constitutes a complete selector,.

so far as operative elements-are concerned.

In incorporating the present invention, I provideapparatus units in smaller number, one fifth as many, for example, as there are selectors, and then organize the e uipments so that any selector which may e seized will have anappar'atus unit operatively associated with it. Therf, after the selector has completed its selective operations and has seized a selected trunk, the associated apparatus unit will function automatically to disass'ociate itself from the temporarily associated selector, and rotate selectively and associate itself with a disengaged selector,

and incidentally place the latter said selector in a condition for seizure by a co-operating switch having access thereto.

The apparatus unit contains the relays which are used in controlling the directive and selective operations thereof, and there fore, the only rela that is required to be permanently associated with the selector, and, therefore, form a art of the selector unit, is the switching re ay.

In order to make the disclosure as simple as possible, I have chosen a selector circuit, well known in the art, and have introduced such changes therein as are needed, in order for it to operate in accordance with the present invention.

It will appear that selectors of the present invention may be co-operated with selectors of well known types, that is, they may seize or be seized by selectors of a well known type, and, therefore, may be used as a selector of any numerical or er.

Referring to the drawings Fig.1 is the apparatus unit and co-operative bank contacts of the present invention.

vFig. 2 is the selector of the present invention, shown as co-operating with a second selector, and the said second selector co-operating with the connector, which latter has access to a subscribers telephone lines.

Fig. 3 shows a calling telephone leading into a lineswitch of the present invention, the sa1d lineswitch having access to the first selector-shown in" Fig. 2, and other selectors not shown.- 7

Fig. 4 shows the way the sheets of drawings are to be assembled to display the telephone system of, the present invention, the lines running toward themargins thereof registering with'lines rnnning toward the mar ms of adjacent sheets, being understoo to be continuations of the same lines.

Fig. 2 shows a modification of the selector B for use if the second selector is of a type similar to B, and not involving a complete unit as does selector SS.

The telephone T is of the general class, and in fact, of the exact type as the telephone designated A in U. S. Patent No. 13,901, re-issued to Frank Newforth, April 13th, 1915.

Lineswitch C is ofthe general class as shown in U. S. patent to Lamb, No. 1,193,- 160, granted August 1st, 1916.

The first selector shown in Fig. 2 when in cooperation with Fig. 1 as an assembly is of the general class shown in U. S. patent to Keith and Erickson, No. 815,321, granted March 13th, 1906, of course, modified in mechanical and circuit details to operate on the well known so-called two-wire principle, and in accordance with the present invention. i

The second selector SS belongs to the same class as the selector shown in Figs. 1 and 2 as an assembly, and it may be assumed to be of the exact type as selector E of the said cited patent to Newforth.

The connector CON may be assumed oi the exact type as connector H of the said cited patent to Newforth.

The telephone T may be assumedas like telephone T Referring further to Fig. 1, the apparatus unit A has access through its wipers and (ea-operating bank contacts with a plurality of first selectors of which selector B is one,

' the wipers of the apparatus unit being shown as resting upon the bank contacts of the connecting conductors to said selector B. The connecting conductors shown leading toward the lower edge of the sheet containingv Fig. 1 are to be assumed as extending:

to the corresponding bank contacts of an apparatus unit similar to A (not shown). However, as will appear presently, the wipers of thesaid apparatus unit, not shown,

will not, and in fact cannot, be resting on the bank contacts corresponding to the said conductors. That is to say, where a plurality of apparatus units have common access to the conductors of a plurality of first selectors, two apparatus units cannot simultaneously rest their wipers in co-operative relation with the same first selector.

While one apparatus unit could probably serve a plurality of say ten or more first selectors as B, in order to avoid calls being blocked due to coincident calling, two or more apparatus units similar to A would ordinarily be employed to guard against such contingency, the number required de pending upon the density of the traffic.

It will, therefore, be manifest that each of the four sets of bank contacts shown cooperative with apparatus unit A refer to a first selector similar to B, and it will be further understood that there probably will be ten or more such sets and corresponding first selectors commonly accessible to the apparatus units associated with the selector group.

Referring to selector B, off-normal set FON operates on the first off-normal movement of the shaft thereof. Off-normal set SON operates on the second vertical off-normal step of the shaft thereof, attention being called to the fact that where an apparatus 'unit is in seized relation with the selector as shown in the drawings, the off-normal set F ON will be in an operated state because, as will appear presently, the shaft of the first selector B is automatically caused to be stepped one step off-normal consequent to its seizure by an apparatus unit. The last said function is to unguard the seized selector, it being understood that the selectors are normally guarded against seizure by a lineswitch and are only unguarded when seized by an ap aratus unit, therefore, the off-normal set F N will normally have its contacts closed instead of open as shown.

Assume a call from telephone T to telephone T the telephone number of latter being 1111. Upon the calling party T initiating the call by removing the receiver from the switch-hook, a circuit can be traced from the winding of slow-releasing relay 301, armature 302, conductor 303, telephone T conductor 304, armature 305 to its grounded resting contact, relay 301 actuating. Assume that private bank contact 307 constitutes ground potential due to selector B being busy; or it does not have an apparatus unit associated with it; or the bank contact 307' constitutes ground potential due to the off-normal set SON being operated. A circuit can be traced from ground received by wiper 308 or wiper 309 to conductor312, armature 313, armature 314, armature 315.to the winding of the motor magnet M the said motor magnet operating and thereby breaking its energizing circuit, whereupon it will retract and drive the wipers 308 to 311 (inclusive) a step into engagement with the successive set of bank contacts (not shown) leading to another first selector, the said op- Due to the slow-releasing characteristic of relay 301 a circuit can be traced from its armature 319, conductor 320, winding of relay 318, armature 315, winding of motor magnet M to grounded battery, relay 318 actuating,

while the motor magnet M remains normal,

due to its marginal adjustment. Ground from conductor 320 will be applied to armature 313, and over conductor 312 to wiper 308, to place a busy guard of ground potential on bank contact 307, so that other line switches commonly accessible to selector B over conductors to 321 will be barred therefrom. Armature will disassociate wiper 309 from conductor 312. The object of the latter novel function will appear presently. Bearing in mind the operate-cl condition of off-normal set FON at the time selector B is seized by line switch C, a circuit can be traced from the upper winding of relay 101, conductor 102, wiper 103, bank contact 104, conductor 105, armature 201, conductor 323, bank contact 327, wiper 310, armature 302, conductor 303, telephone set T conductor 304, armature 305, wiper 311, bank contact 328, conductor 32 1, armature 202, conductor 203, bank contact 106, wiper 107, conductor 108 to the lower winding of relay 101, the latter relay actuatin A cirunit can now be traced from groun ed armature 109 to the winding of slow-releasing relay 110, the latter relay actuating. A circuit can now be traced from grounded contact 112, conductor 113, Wiper 114, bank contact 115, conductor 116, conductor 321, bank contact 307, wiper 308, conductor 312 to conductor 320, the said ground being applied to conductor 320 before armature 319 has retracted, and, therefore, relay 318 is maintained actuated dependent upon ground being maintained on conductor 321.

Upon the calling party manipulating the calling device at telephone T in accordance with the first digit 1, relay 101 will deactuate and reactuate one time responsive thereto, whereupon armature 109 will apply a ground impulse to conductor 117, wiper 118, bank contact 119, conductor 120, armature 205, conductor 206, bank contact 121, wiper 122, armature 123, winding of slowreleasing relay 124, wiper 125, bank contact 126, conductor 127 to the winding of vertical magnet V, the vertical magnet operat armature 208 on. rotary magnet R conductor 209, bank contact '134, wiper 135 to grounded armature 136 on relay 129. Upon the retraction of armature 128 following the said impulse to the vertical ma net V a circuit can be traced from grounded conductor 113, armature 128, armature 137,

- wiper 138, bank contact 139, conductor 140 to the winding of the rotary magnet R the rotary magnet operating to rotate the wipers 212 to 214 one rotary step, into engagement with bank contacts 215 to 217, respectively. Consequent to the rotary magnet R operating and attracting its armature 208, the traced locking circuit for relay 129 is opened so that relay 129 will deactuate. However, if bank contact 215 constitutes ground potential, due to the secondselector SS being busy, the said ground will be applied through wiper 212, armature 218 to conductor 209, armature 208, oft-normal 207, conductor 132, bank contact 131, wiper 130 to the winding of relay 129, causing it to actuate and look over the before traced circuit to armature 136, whereupon the before traced circuit energizing the rotary magnet ,R will be reestablished and the rotary magnet will operate to advance the .wipers an additional rotary step, the wipers 212 to 214 engaging the successive set of bank contacts leading to a second selector of the group containing second selector SS, and if the wiper 212 encounters ground potential on the second co-operating bank contact, indicating that the corresponding second selector is also busy, the relay 129 will be caused to reactuate and lock. The rotary magnet R will reoperate, as in the manner hereinbefore descrlbed, to advance the wipers 212 to 214 an additional rotarystep, the described cycle of operations reoccurring as long as the wiper 212 encounters ground potential. The selector B will seize in the manner as will be described presently, when the wiper 212 fails to receive ground potential.

In this connection attention is directed that when the shaft of the selector, B moved from the first off-normal vertical position under directive control of the calling device at telephone-T the off-normal spring set SON operated, and, therefore, a-circuit' is then'traceable from grounded conductor321,

off-normal spring 222, resistance 223, armature 224 to the upper winding'of relay 225. The "adjustment of relay,225,' in iew of rc- 'sistan'ce 223, is such that the said relay 225 is-not now fully operatively energized, so that armature 226 thereof isthe. only arma-w ture operativelyafi'ected. .However, the said armature 226 does not engage its working contact but does disengage its :rerting contact, the latter function being to prevent the release magnet R becoming energized by way of off-normal spring 227. In this connection it will be noted that the lower winding terminal of relay 225 is grounded by way of conductor 321, and it will also be noted that whenever the relay 129 is actuated, the upper terminal of the lower winding of. relay 225 is grounded by way of conductor 209, bank contact 134, wiper 135 to grounded armature 136. Also, that the said upper terminal of the lower winding of relay 225 will be grounded by way of armature 218 and wiper 212, provided the said wiper 212 is resting on a grounded bank contact. the said upper terminal of the lower windving of relay 225 is grounded and the rotary magnet R is retracted, ground potential will exist on the terminal of relay 129, and,

therefore, if the ground is removed from the said upper terminal of the lower winding of relay 225, the said winding and the winding-of relay 129 will become energized in series. The characteristic and adjustments of the said relays is such that relay 225 will operative'ly energize from its lower winding when in series with relay 129, but the relay 129 will not operate under this condition. It will thus be clear that if at any time after relay 124 deactuate; following the last vertical impulse, relay 129 is deactuated and wiper 212 does not at the same time'receive ground potential, the upper terminal of the lower winding of relay 225 will not constitute ground potential and the latter said winding and the winding of relay 129 will be in series relation to the grounded conductor 321, and as hereinbefore set forth, the relay 225, and not the relay 129 will be operatively energized.

In this connection it will be manifest that at the time selector B seizes, by reason of relay 225 actuating, a circuit can be traced from grounded conductor 321. lower winding of relay 225, armature 224, to the upper winding of relay 225, the lower winding of'relay 225 at this instant being energized through battery derived through its upper winding and a parallel circuit from the winding of relay 129, upper armature of re lay 110, wiper 130, bank contact 131, conductor 132, oft-normal spring 207. armature It will also appear that whenever 208 of the rotary magnet of R conudctor 209 to the said upper terminal of the lower winding of relay 225. But, as will appear presently, the winding of relay 129 is forthwith disassociated by reason" of the automatic disassociation of the apparatus unit consequent to the seizure to the selector B, whereupon the two win-dings of relay 22 will become energized in series from the battery permanently attached to the upper winding thereof, without affecting attachments.

Assume that at the time wiper 212 first encountered bank contact 215, the second selector SS was idle, and, therefore, contact 215 did not constitute ground potential, and that in view of the foregoing statement the relay 225 will thereon operatively energize both of its windings and the selector will be in a seized condition. A circuit can now be traced from armature 201, wiper 213, bank contact 216, conductor 230 to the battery winding of the line relay in the second selector SS (being relay 47 in the cited patent to N ewforth) and from the ground winding of the said relay, conductor 231, bank contact 217, wiper 21 1 to armature 202, the said circuit including the traced path through telephone T The line relay in the second selector SS will now be actuated and its dependent slow-releasing relay (corresponding to relay 18 of the cited patent to Newforth) will also be actuated causing conductor 232 (corresponding to the conductor leading to terminal 114 of the cited patent to Newforth) to become grounded; this ground being communicated to bank contact 215, Wiper 212, armature 218, conductor 321 to bank contact 307. This ground is applied back from the seized second selector before ground is removed from conductor 116 due to the disassociation or the apparatus unit A from first selector B, as will appear presently, and that, therefore, no lapse of ground potential will occur to conductor 321, and, therefore, the lineswitch C would be maintained seized dependent upon ground being maintained on conductor 322. Armature 218 being attracted, the ground received from wiper 212 would be applied to the lower winding terminal of relay 225 maintaining relay 225 energized and the selector B seized, also dependent upon ground being maintained on conductor 332.

At the time the shaft of selector B moved vertically from the first oti-normal position into the second vertical off-normal position, wherein its wipers 212 to 214 are in alignment with the first level of bank contacts, re-

sponsive to the directive control of the calling party at telephone T through the calling device thereat, ground is applied from offnormal spring 235 to conductor 322 to bank contact 306. In View of armature 325 of lineswitch C being attracted, this is to no operative purpose with respect to lineswitch C, but as will appear presently, it has an object with relation to other lineswitches having common access with lineswitch C to selector B Assume that while the shaft was moving from the first Off-normal position under directive control, the position it occupied when seized by the lineswiteh (J, as win be clear presently, the calling party at telephone T replaced the receiver on the switch-hook thereat to terminate the service. The relay 101 will deactuate, followed by its dependent relay 110, whereupon'a circuit can be traced from grounded armature 109, conductor 117, wiper 118, bank contact 115), conductor 120.

armature 205, conductor 200, bank contact 121, wiper 122, armature 123, wiper 151, bank contact 152, conductor 153, off-normal spring 227 to the release magnet Re the release magnet operating to restore the shaft of selector B to normal position. Conscquent to the shaft restoring to normal position, off-normal spring 235 will disconnect the ground applied to conductor and bank contact 306 and its multiples just before the shaft reaches the first vertical offnormal position. When it leaves the first oft-normal position in its restoration to the normal position, grounded oil-normal spring 2&0 will apply its ground to conductor The very brief lapse of ground potential to conductor 321 may or may not permit the lineswitch C to unseize by permitting relay 318 to deactuate. However, the selector B, as will appear presently, is in readiness to be seized by a lineswitch in seizing relation to the selector B at the instant of the lapse of ground potential to conductor 321.

Upon the retraction of the upper armature of relay 110, relay 225 will deactuate. Ground from contact 112 is removed from conductor 321, but ground from off-normal spring 240 is applied to conductor 321 at aboutthe same time and maintained until the vertical magnet V is energized from armature 109, as before described, to disengage oft-normal spring 240 to unground conductor 321 so that relay 318 will retract if it has not done so during the lapse of ground to conductor 312 referred to. The selector B, by reason of

conductors

321 and 322 not now constituting ground potential, is seizable by a lineswitch; lineswitch C, for example, if the party at telephone T reinitiates the call, py lremoving the receiver from the switch- Assume that the selector B seized, as described, and that the lineswitch C and the selector B is maintained seized dependent on the line relay in the second selector SS being maintained energized in the path including the calling telephone T. A circuit can be traced from grounded armature 226, conductor 237, bank contact 141, wiper 142, conducits energizing-circuit at armature 145 t 6 on. Upon the retraction of the armature 10 in the drawing. 1 The ap aratus unit A and oft-the motor magnet M, the wipers of the apparatus unit A will be driven one step so that they engage the next set of; bank contacts to the right of those shown as engaged its contained relays whic control the selector B, first directively and then, automatically selectively, 1S Il0W disassociated from the selector B, and is in testing or hunting engagement with a selector of the group containing the selector B throughconnecting conductors corresponding to those leading from selector B and terminating in the bank contacts shown engaged by the wipers of the apparatus unit A, hearing in mind that another or other apparatus units have access to the selector B and other selectors of its group through the common connecting con ductors leading to the said bank contacts in the apparatus unit A.

To simplify the descriptions, it will now be assumed that the wipers of the apparatus unit A have been resting on' the set of bank contacts on the left of those shown asengaged in the drawing, and that due to the corresponding selector having become thereafter seiied, they advanced to the position shown in the drawing, in the manner as desbribed with relation to motor magnet energizing consequent to the selector B seizing.

It will also be assumed that the selector B is in seized relation, as described, having been previously operated. Therefore, con ductor 237 will constitute ground potential received from armature 226, so when wiper 142 engages bank contact 141, the latter will apply the ground potential received from conductor 237 to bank contact 141, wiper 142, conductor 143, armature 144, armature 145 to the winding of the motor magnet M, the motor magnet operating, and upon its retraction causing the wipers to be advanced an additional rotary step, the wiper 142 selectivelytesting for an ungrounded bank contact, the cycle of operations with respect to the motor magnet M causing the wipers to be advanced, continuing until wiper 142 fails to find a grounded bank contact, indicating that the wipers then rest upon a set-of bank contacts correzponding to a selector which has not seized, though, as will appear presently, it may have been seized by a lineswitch, and perhaps be under operation in extending a connection. Under the latter assumedconditions, one of the other apparatus units would be associated with it, and, therefore, the local conductor 146, which is local to the group of apparatus units serves only to multiply tie and ground the bank contacts corresponding to 148 of the said leasing t units, as will appear. There will be a conductor correspondin to 146 for each set of bank contacts accessible from the units. If an apparatus unit is in seized relation to the set of bank contacts concerned, ground from its armature corresponding to 151 will serve to ground conductor 146. When themotor magnet M attracts its armatures, a circuit' can be traced from grounded contact 149 to the winding of slow-releasing relay 150, so that armature 151 completes a circuit from wiper 147 to conductor 143 when the motor magnet operates, and due to the slow-releasmg characteristic of relay 150 its armature 151 is held in engagement with its working contact for an appreciable time afterthe retraction of the armatures on themotor magnet M. That i's, when the wipers advance consequent to the retraction of the motor magnet, the wiper 1471will be in testingen gagement with its co-operatin bank contact and with the armature 145 of t e motor magnet, it being remembered that the wipers of the apparatus unit A advance conse uent to the retraction of the motor magnet id, and, therefore if the relay 150 were not slow-rehe described test circuit would be open at armature 151. In this connection it will be noted that after the apparatus unit has rotated to the set of bank contacts that do not have a bank contact engaged by wiper 147 or a bank contact engaged by wiper 142 constituting ground potential, the motor magnet M will not reenergize and the relay 150 will thereafter reactuate and apply ground through wiper 147 to the engaged bank contact and common conductor 146. A ground can now be traced from armature 226, conductor 153, bank contact 152,- wiper 151, armature 123, wiper 122, bank contact 121, conductor 206, ofl-normal spring 241 to the winding of the vertical magnet V the vertical magnet operating to step the shaft to the first off-normal position, and incidentally operate the off-normal set FON, thereby opening the last traced circuit. A parallel circuit to conductor 206 may be traced through armature 205, conductor 120, bank contact 119, wiper 118, conductor 117, grounded armature 109, though the latter circuit path is opened with the former one at off-normal spring 241.

From the foregoing descriptions it is now clear that the apparatus unit A, while hunting, will pass all bank contact sets in which wipers 147 or 142, or both, encounter ground thereat, and that the contact engaged by wiper 142 will constitute ground potential it the corresponding first selector is in a seized state with respect to a second selector, and that the contact engaged by wiper upon bank contacts of the correspondin first selector, regardless of the condition 0 selector.

' mature 226,

the said first selector. It is thus clear that where a plurality of apparatus units'have common access to a plurality of first selectors, it will be impossible for two apparatus units to become operatively related to the same selector, coincidentally. It is also clear that as soon as a selector, which has been operated by an'apparatus unit, has seized, the said apparatus unit forthwith automatically functions to disengage itself and engage itself with the first engageable Assume that after the second selector SS has been seized by the first selector B, as described, the calling party at telephone T desires to terminate the service, and replaces the receiver thereat on the switch-hook. The line relay in selector SS will deactuate and cause ground potential to be removed from conductor 232. This opens the energizing circuit as traced for relay'225 offse- 'le'ctor B and relay 318 of line-switch C,

whereupon said B and C will unseize, and a circuit can be traced from grounded arconductor 153, off-normal spring 227 to the winding of release mag net R the release magnet operating to restore the shaft of selector Bf to normal. Bearingin mind that there is no apparatus unit associated with selector B since it was if disassociated, inthe manner described, con sequent to the seizing of the selector B, and that, therefore, there will be no circuit established to the winding of the vertical magnet-3V as before described, when the restoration of selector B was effected by the calling party at telephone T replacing the receiver on the switch-hook before the selector B seized, but after it has been partly operated directively, the shaft of the selector B will remain atnormal, and, therefore, ground will be applied from off-normal spring 240 to conductor 321, and to bank contact 307 and multiples thereof, guarding the selector against seizure by a lineswitch of the group containing lineswitch C. For it is manifest that if the selector B were seized at this juncture it will not be in operative condition by reason of there' being no apparatus unit associated therewith, so that a hunting lineswitch will pass over the contacts corresponding to the selector B, and seize thcontacts corresponding to a selector having the apparatus unit A, or another apparatus unit, associated with it, and which has not yet been seized by alineswitch.

It will appear that at the time the selector B unseized in the last foregoing description referring thereto, ground was removed from conductor 321, and, therefore, were not the wiper 309 provided on the lineswitch G, and other lineswitches of its group, together with grounded ofi-normal spring 235 on the first selector B, there would be an appreciable time, while the shaft of the selector is restoring, wherein the selector would not be guarded against seizure until conductor 321 is grounded by oif-normal spring 240 upon the shaft receding below the first off-normal position. The seizing of the selector by a lineswitch at this time, as has been referred to, would vitiate the call involved since the selector B has no controlling relays associated with it. However, due to the

wipers

308 and 309 of lineswitch C (and the lineswitches of its group, similarly,) being tied through armature'325, the ground on conductor 322 received from off-normal spring 235 will be the same as if conductor 321 were directively grounded. Ground is maintained on eonductor 322 throughout the time the selector B is operated regardless of the'condition of conductor 321, but due to armature 325 being attracted while the lineswitch .C is seized, the said ground on conductor 322 has no operative effect, so that when the ground is removed from conductor 321 as described, the lineswitch G will unseize. Of course, the descriptions specific to the lineswitch C will apply to any lineswitch of its group co-operating the first selector B or any selctor of its group. T

Assuming that after the second selector SS has been seized, as set forth, the calling party at telephone T manipulates the call-.

ing device thereat in accordance with the second digit 1, the second selector SS will operate in the well known manner to extend the connection through bank contacts 251 to 253 to connector CON, and upon the calling party manipulating the calling device corresponding with the last two digits 1- 1, the connector will operate to set'its wipers 254 to 256 upon bank contacts 257 to 259, corresponding to the line leading to the called telephone T the cut-off relay 260 operating to disassociate the lineswitch associated therewith, in the well known manner. The connector will seize and apply ringing current to vibrate the ringer 261 at telephone T in the well known manner. Upon the party at telephone T removing the receiverfrom the switch-hook, the calling party at telephone T and the called party are in talking relation.

The release of the connection will be effected by-the calling party, in the well known manner, wherein ground will be removed from

conductors

262, 232, and 321, conseuent to the restoration of the connector V 301?, jvhereupon the second selector SS, the first selector B and the lineswitch C will unseize, the selectors restoring their shafts to normal.

In the foregoing descriptions the apparatus units cooperated with first selectors wherein the second selectors were of a well known type. It is manifest that second selectorswith co-operating apparatus units similar to the first selectors and the r cooperating apparatus units may be substltuted for the second selectors of well known type, v

as described with relation to selector B wherein the ground applied through offnormal spring 235 guards the selector at bank contact 306 (and multiples) until the ground applied by off-normal spring 240 guards the selector at bank contact 307 (and multiples).

In carrying out the plan of employing the said novel second selectors, a modification as shown in Fig. 2 consisting of the introduction of an armature 275 and wiper 276 on relay 225, so that a hunting first selector as B, for example, will have its wipers 212 and 276 tied together through armature 275, so if the second selector is guarded by a ground being on its conductor corresponding to conductor 322 of selector B under the conditions described in connection with selector B, the testing first selector will be barred against stopping and seizing, and it will, therefore, selectively rotate off the grounded contact engaged by wiper 276. However, since armature 27 5 is attracted during the time the selector is seized, wiper 276 will have no operative efiect after the seizure.

In view of the fact that the directive and selective operative periods of a selector in linking a connection does not ordinarily occupy more than about one second, and that the holding time of the connection subsequent thereto in many exchanges averages more than a minute, it is manifest that where the essential control relays are adapted to have common, temporary relation with a group of selectors, and that they will become disengaged immediately after their service has been completed, and that will forthwith associate with a next selector, a very great economy in equipment, space, and maintenance is attained.

I claim A 1. In a switch, abusy test wiper and an auxiliary busy test wiper, cooperating'back contacts for eachsaid wiper to bar the seizure of the switch, and means in the switch effective consequent to its seizure for 'disabling one said wiper while maintaining the operative condition of the other said wiper.

2. In aswitch, a busy test wiper and an auxiliary busy test wiper, cooperating bank contacts for each said wiper to bar the seizure of the switch, and means in the switch for disabling one said wiper while maintaining the operative condition of the other said wiper.

8. In a switch, a busy test wiper and an auxiliar busy test wiper, respective coopcrating ank contacts for each'said wiper to bar the seizure of the switch, each said wiper for testing for a busy condition of the bank contacts, and means whereby the switch will be barred from seizing if either of said wipers encounters a said busy condition.

4. In a switch, a busy test wiper and an auxiliary busy test wiper, respective cooperating bank contacts for each said wiper to bar the seizure of the switch, each said wiper for testing for a different specific condition of the bank contacts, and means whereby the switch will be barred from seizing if either of said wipers encounters a said specific condition.

5.. In a switch, a busy test wiper and an auxiliary busy test wiper, respective cooperat-lng bank contacts for each said wiper to bar the seizure of the switch, each said wiper for testing for a different specific condition of the bank contacts, means whereby the switch will be barred from seizing if either of. said wipers encounters a said specific condition, and automatic means for disabling one of the wipers consequent to the other said wiper encountering a said specific condition.

6. In a telephone system, a first switch, a second switch accessible from the first switch, two test terminals of the second switch each of which will manifest a difi'erent specific condition of the second switch, the test termlnals being subject to test by the first switch through respectively cooperating test contacts, and means whereby if either said specific condition of the second switch exists when its test terminals are tested by the said test contacts the first switch will be barred from seizin the second switch.

7. In a te ephone system, a first switch, a second switch accessible from the first switch, two test terminals of the se"ond switch each of which will manifest a different specific condition of the second switch, the test terminals being subject to test by the first switch through respectively cooperating test contacts, and means whereby if either or both saidspecific conditions of the second switch exists when its test terminals are tested by the said test contacts the first switch will be barred from seizing the second switch.

8. In atelephone system, a first switch, a second switch accessible from the first switch, a plurality of test terminals of the said second switch each of which will manitest a different specific condition of the seclit) Iii)

minal of the second switch when tested by said test contacts the first switch will be barred from seizing the second switch.

9. In a telephone system, a first switch, a second switch accessible from the first switch, a plurality of test terminals of the said second switch each of which will manifest a different specific condition of the second switch, the test terminals being subject to testby the first switch through respectively cooperating test contacts, means whereby if any said specific condition is manifested by the condition of a test terminal of the second switch when tested by said test contacts the first switch will be barred from seizing the second switch, and means for causing the first switch to seize the second switch consequent to testing if none of the said specific conditions exists.

10. In a telephone system, a first switch, a second switch accessible from the first switch, a plurality of test terminals of the said second switch each of which will manifest a different specific condition of the second switch, the test terminals being subject to test by the first switch through respectively cooperating test contacts, means whereby if any said specific condition is manifested by the condition of a test terminal of the second switch when tested by the said test contacts. the first switch will be barred from seizing the second switch, and means for causing the firstswitch to seize the second switch consequent to testing if none of the said specific conditions exists and to thereupon apply a said condition to one of said terminals.

11. In a telephone system, a first switch, a second switch accessible from the first switch, a plurality of test terminals of the said second switch each of which will manifest a different specific condition of the second switch, the test terminals being subject to test by the first switch through respectively cooperating test contacts, means whereby if any said specific condition is manifested by the condition of the test terminal of the second switch when tested by the said test contacts the first switch will be barred from seizing the second switch, and means for causing the first switch to seize the second switch consequent to testing if none of the said specific conditions exists and to thereupon apply a said condition toone of said terminals from a said test contact and to disable the other said test contact.

12. In a telephone system, a first switch, a second switch accessible from the first switch, a plurality of test terminals ofthe said second switch each of which will manifest a different specific condition of the second switch, the test terminals being subject to test by the first switch through respectively cooperating test contacts, means whereby if any said specific condition is manifested by the condition of a test terminal of the sec-,

ond switch when tested by the said test contacts the first switch will be barred from seizing the second switch, means for causing the first switch to seize the second switch consequent to testing if none of the said specific conditions exists and to thereupon apply a said condition to one of said terminals, and means for unseizing the first switch consequent to the termination of a C(ZIItHlII condition of one of the said termina s.

13. In a telephone system, a first switch, a second switch accessible from the first switch, a plurality of test terminals of the said sec ond switch each of which will manifest a different specific condition of the second switch, the test terminals being subject to test by the first switch through respectively cooperating test contacts, means whereby if any said specific condition is manifested by the condition of a test terminal of the second switch when tested by the said test contacts the first switch will be barred from seizing the second switch, means for causing the first switch to seize the second switch consequent to testing if none of the said specific conditions exists and to thereupon apply a said condition to "one of said terminals, and means for causing the first switch to unseize consequent to the termination of the said ap plied condition regardless of the condition of any other said terminal but to be barred against reseizing the second switch dependent upon the condition of the said other terminal. I

14. In a' telephone system, a first switch, a second switch accessible from the first switch, a plurality of test terminals of the said second switch each of which will manifest a different specific condition of the second switch, the test terminals being subject to test by the first switch through respectively cooperating test contacts, means whereby if any said specific condition is manifested by the condition of the test terminal of the second switch when tested by the said test contacts the first switch will be barred from seizing the second switch, means for causing the first switch to seize the second switch consequent to testing if none of the said specific conditions exists and to thereupon apply a said condition to one of said terminals, and means for causing the first switch to unseize consequent to the termination of the said applied condition while a condition exists for barring the second switch against subsequent seizure by the firstswitch.

15. In a telephone system, a first switch, a second switch accessible from the first switch, a third switch having access to the second switch, a plurality of test terminals of the said second switch each of which will manifest a different specific condition of the second switch, the respective test terminals and third switches, means whereby if any said specific condition is manifested by the condition of a test terminal of the second switch when tested by the said test contacts of the first switch the said first switch will be barred from seizing the second switch, means for causing the first switch to seize the second switch consequent to testing if none of the said specific conditions exists and to thereupon apply a said condition to one of said terminals and its multiples to bar the third switch from seizing the second switch, and means for causing the. first switch to unseize consequent to the termination of the said applied condition while a condition exists for barring the second switch against subsequent seizure by the first switch or the third switch.

16. In a telephone system, a first switch, a second switch accessible from the first 2 switch, a normal inoperative condition for the second switch, an operative condition of the second switch, a seized condition of the second switch, a first and a second test terminal for'the second switch accessible for test from the first switch, means for barring the first switch from connecting to the second switch controlled from a condition of either one of said terminals, means whereby a normal inoperative condition of the second switch will aifect the first said terminal so as to bar the second switch from seizure by the first switch, means whereby an operative condition of the second switch will render both said terminals in condition for the seizure of the second switch by the first switch, and means whereby a seized condition of the second switch will bar the said second switch from seizure by the first switch due to a condition of its said second terminal.

17. In a telephone system, a plurality of selective switches having individual driving mechanisms, a plurality of control relay sets less in number than the number of selective switches, associating switches for interchangeably interconnectingthe control relav sets and selective switches temporarily, self actuating means for operating an associating switch after a selective switch has been actuated to associate its control relay set with another selective switch for. operation but leaving the first selective switch actuated,

18. In a telephone system, a plurality of selective switches having individual driving mechanisms, a plurality of control relay sets less in number than the number of selective switches, associating switches for interchangeably interconnecting the control relay sets and Selective switches temporarily,

self actuating means for operating an assocrating switch after a selective switch has been actuated to associate its control relay set with another selective switch for operation but leaving the first selective switch actuated, and means for restoring the latter said actuated switch.

19., In a telephone system, a plurality of selective switches each having individual driving mechanism, a plurality of control .relay sets less in number than the number of selective switches, associating switches for interchangeably interconnecting the control relay sets and selective switches temporarily, cooperating antecedent selective switches, self actuating means for operating an associating switch after a selective switch has been actuated to associate its control relay set with anotherselective switch for operation but leaving the first selective switch actuated, means for restoring the latter said switch, and means for guarding the latter said switch against seizure by a said co-operating selective switch until it has restored and a said control relay set has become associated therewith.

20. In a telephone system, a plurality of switch elements, sets of contacts respectively corresponding to each switch element, common control mechanism interchangeably cooperative with the switch elements through the respective sets of contacts to render a cooperated control mechanism and a switch element a complete operative switch, means whereby the control mechanism can be cooperative with but one switch element at any one time, and means whereby the control mechanism will be automatically discon nected from the switch element when the switch becomes operated, and automatic means for cooperating the control mechanism with another of said switch elements consequent upon the control mechanism becoming disconnected from a switch element.

21. In a telephone system, a plurality of switch elements, sets of contacts respectively corresponding to each switch element, common control mechanism interchangeably cooperative with the switch elements through the respective sets of contacts to render a cooperated control me hanism and a switch element a complete operative switch, means whereby the control mechanism can be cooperated with but one switch element at any one time, means whereby the control mechanism will become automatically disconnected from the switch element ronsequent upon the switch becoming operated into a predetermined state, and automatic means for cooperatin the. control mechanism with an idle one of said switch elements consequent upon its becoming dsconnected from an operated switch element.

22. In a telephone system, a plurality of switch elements, sets of contacts respectively ing the control mechanism with an idle one of said switch elements'consequent upon its becoming V disconnected from an operated switch element and means for restoring an operated switch element under directive control regardless of the said control mechanism being or not being cooperated with a concerned switch element.

23. In a telephone svstem, a plurality of switch elements, sets 0 contacts respectively corresponding to each switch element a plurality of common control mechanisms interchangeably cooperative with the switch elements through the respective sets of contacts to render a. cooperated control mechanism and a switch element a complete operative switch, means whereby a said one of the control mechanisms can be cooperative with but one switch element at any time, means whereby a cooperated control mechanism will become automatically disconnected from a switch element when the switch element becomes operated, and automatic means for cooperating the control mechanism with another one of said switch elements consequent upon its becoming disconnected from a switch element.

24. In a; telephone system, a plurality of switch elements, sets of contacts respectively corresponding to each switch element, a smaller plurality of common control mechanisms than switch elements interchangeably cooperative with the switch elements through the respective sets of contacts to render a cooperated control mechanism and a switch element a complete operative'switch, means whereby a said one of the control mechanisms can be cooperative with but one switch element at any time, means whereby a cooperated control mechanism will become automatically disconnected from a switch element when the switch element becomes operated, and automatic means for cooperating the control mechanism with another one of said switch elements consequent upon its becoming disconnected from a switch element.

25. In a telephone system. a plurality of switch elements, sets of contacts respectively corresponding to ea h switch element, a common control mechan sm interchangeably cooperative with the switch elements through wipers of the control mechanism and regis operating a control mechanism with a switch. I

element and for disassociatin the control mechanism from the switch e ement consequent to a predetermined state of the switch occurring and for then automatically cooperating the'control mechanism with another switch .element to form an alternative switch.

26. In a telephone system, a'plurality of switch elements, sets of contacts respectively corresponding to each switch element, a

plurality of common control mechanisms interchangeably cooperative with the switch elements through wipers of the control mechanisms and registering said sets of contacts of the switch elements, a said switch elementand a cooperated control mechanism together forming a complete switch, means whereby a control mechanism can be cooperated with but one element at a time, means whereby but one control mechanism can be cooperated with a single switch element at anytime,

and propelling means for cooperating a control mechanism with a switch element and for disassociating the control mechanism from the switch element consequent to a predetermined state of the switch occurring and for thereupon automatically cooperat-, ing the control mechanism with another switch element to form' an alternative switch.

27. In a telephone system, a plurality of switch elements, sets of contacts respectively'corresponding to each switch element, a common control mechanism interchangeably cooperative with the switch for connecting to the respective switch ele-" ments, means for normally guarding the switch elements against seizure by any of said switches, and means for unguarding a switch element consequent to its being cooperated with'a control mechanism. 7

28. In a telephone system, a plurality of switch elements, sets'of contacts respectively corresponding to each switch element, a comswitches for connecting to the respective 139 switch elements, means for normally guarding the switch elements against seizure by any of said switches, and means for unguarding a switch element consequent to its being cooperated with a control mechanism. 135

29. In a telephone system, a plurality of switch elements, sets of contacts respectively corresponding to each element, a common control mechanism interchangeably cooperative with the switch elements through elements through wipers of the control mechanism and 9 a registering set of said contacts, switches operated switch element will be thereby unguarded subject to connection by a said switch.

30. In a telephone system, a plurality of switch elements, sets. of contacts respectively corresponding to each element, a common control mechanism interchangeably cooperative with the switch elements through wipers of the control mechanism and regis tering said sets of.contacts, switches for connecting to the respective switch elements, a normal position of the respective switch elements at which they are guarded against connection by a said switch, and means whereby when a control mechanism cooperates with a switch element the cooperated switch element will be thereby operated off-normal to unguard it.

31. In a telephone system, a plurality of switch elements, sets of contacts respectively corresponding to each element, a common control mechanism interchangeably automatically cooperative with the switch elements through wipers of the control mechanism and registering said sets of contacts, switches for connecting to the respective switch elements, a normal position of the respective switch elements at which they are guarded against connection by a said switch, and means whereby when a control mechanism cooperates with a switch element the cooperated switch element will be thereby operated cit-normal to unguard it.

32. In a telephone system, a plurality of switch elements, sets of contacts respectively corresponding to each switch element, a common control mechanism interchangeably cooperative with the switch elements through wipers of the control mechanism and a registering set of said contacts, switches for connecting to the respective switch elements, means for normally guarding the switch elements against seizure by any of said switches, means for unguarding a switch element consequent to its being cooperated with a control mechanism, and means whereby after a switch element is seized by a said switch the switch element will be barred against connection from any other said switch.

33. In a telephone system, a plurality of switch elements, sets of contacts respectively corresponding to each element. a common control mechanism interchangeably cooperative with the switch elements through wipers of the control mechanism and registering said. sets of contacts, switches for connecting to the respective switch elements, a normal position of the respective switch elements at which they are guarded against connection by a said switch, means whereby when a control mechanism cooperates with a switch element the cooperated switch element will be thereby operated ofi-normal to unguard it, and means whereby after a switch element is seized by a said switch the switch element will be barred against connection from any other said switch.

34. Ina telephone system, a plurality. of connecting link elements, sets of contacts respectively corresponding to each connecting link element, common control mechanism interchangeably cooperative with the .link elements through any one of said sets of contacts to render a cooperated control mechanism and a connecting link element a complete connecting link, means whereby the control mechanism can be cooperated with but one link element at any time, and means whereby the control mechanism will become automatically disconnected from the link element consequent upon a predetcri'nined condition of the connecting link ensuing.

35. In a telephone system, a first switch, a second switch accessible from the first switch, two test terminals of the second switch each of which will manifest a different specific condition of the second switch, the test terminals being subject to test by the first switch, and means whereby if either of said specific condition of the second switch exists when its test terminals are tested by the first switch the first switch will be barred from seizing the second switch.

36. In a telephone system, a first switch, a second switch accessible from the first switch, a plurality of test terminals of the second switch each of which will manifest a difierent specific condition of the second switch, the test terminals being subject to test by the first switch, and means whereby if any said test terminal manifests any said specific condition of the second switch when its test terminals are tested by the first switch the first switch will be barred from seizing the second switch.

37. In a telephone system, a plurality of connecting link elements, sets of contacts respectively corre ponding to each connecting link element, common control mechan sm interchangeably cooperative with the link elements through any one of said sets of contacts to render a cooperated control mechanism and a connecting l nk element a complete connecting link, means whereby the control mechanism can be cooperated with but one link element at any time. means whereby the control mechanism will become automatically d sconnected from the link element consequent upon a predetermined condition of the connecting link ensuing, and means automatically controlled for connecting the disconnected control mechanism with another link element.

38. In a telephone system, a plurality of non-operative switch elements and corresponding sets of terminals therefor, an operating mechanism having a set of movable wipers for connection with the respective sets of terminals, a connected said mechanism and said switch element forming an operative switch, and means for automatically connecting and disconnecting the operating mechanism with the respective switch elements.

39. In a telephone system, a plurality of non-operative switch elements and corresponding sets of terminals therefor, a plurality of operating mechanisms each having a set of movable wipers for common connection to the said switch elements through a set of said terminals, a connected said mechanism and said switch element forming an operative switch, and means for automatically connecting and disconnecting the operating mechanisms with the respective switch elements interchangeably.

40. In a telephone system, a plurality of non-operative switch elements and corresponding sets of terminals therefor, an operating mechanism having a set of movable wipers for connection with the respective sets of terminals, :1 connected said mechanism and said switch element forming an operative switch, and means for automaticallv connecting the operating mechanism with the respective switch elements while the switch elements are idle, and automatic means for disconnecting the operating mechani m when its connected switch element has become operated.

41. In a telephone system, a plurality of switch elements. sets of contacts respectively corresponding to each switch element, a plurality of common control mechanisms in terchangcahly cooperative with the switch elements through wipers of the control mechanisms and registering said sets of contacts of the switch elements, a said switch element and a cooperated control mechanism together forming a complete switch, means whereby a control mechanism can be operated with but one element at a time, means whereby but one control mechanism can be cooperated with a single switch element at any time, and propelling means for coopcrating a control mechanism with a switch element and for disassociating the control mechanism from the switch element consequentto a predetermined state of the switch occurring.

42. In a telephone system, a plurality of switch elements. sets of contacts respectively corresponding to each switch element, a plurality of common control mechanisms interchangeably cooperative with the switch elements through wipers of the control mechanisms and registering said sets of contacts of the switch elements, a said switch element and a cooperated control mechanism together forming a complete switch, means whereby a control mechanism can be cooperated with but one element at a time, means whereby-but one control mechanism can be cooperated with a single switch element at any one time, propelling means for coopcrating a control mechanism with a switch element and for disassociating the control mechanism from the switch element consequent to a predetermined state of the switch occurring, and means for cooperating the disconnected said control mechanism with another switch element to form an alternative switch.

43. In a telephone system, a plurality of selective switches having individual driving mechanism, a plurality of control relay sets less in number than the number of selective switches, associating switches for interchangeably interconnecting the control relay sets and selective switches temporarily, and self-actuating means for selectively opcrating the associating switch after a selective switch has been actuated to associate its control relay set with another selective switch for operation but leaving the first selective switch actuated.

44. In a telephone system, a switch, a trunk line subject-to seizure from the switch, two test terminals of the trunk line each of which will manifest a different specific condition of the trunk line, the test terminals being subject to test by the switch through respectively cooperating test contacts, and means whereby if either said specific condition of the trunk line exists when its test terminals are tested by the said test contacts the switch will be barred from seizing the trunk line.

45. In a telephone system, a switch, a trunk line subject to seizure from the switch, two test terminals of the trunk line each of which will manifest a different specific condition of the trunk line, the test terminals being subject to test by the switch through respectively cooperating test contacts, and means whereby it either or both said specific conditions of the trunk l ne exists when its testterminals are tested by the said test contacts the switch will be barred from seizing the trunk line.

46. In a telephone system, a switch, a trunk line subject to seizure from the switch, a plurality of test terminals of the said trunk line each of which will manifest a difi'erent specific condition of the trunk line, the test term nals being-subject to test by the switch through respectively cooperating test contacts. and means whereby if any said s ecific condition is manifested by the condition of a said test terminal of the trunk line when tested by said test contacts the switch will be barred from seizing the trunk line.

47. In a telephone system, a switch, a trunk line subject to seizure from the switch, a plurality of test terminals of the trunk line each of which will manifest a different specific condition of the trunk line, the test terminals being subject to test bythe switch through respectively cooperating test contacts, means whereby if any said specific condition is manifested by the condition of a test terminal of the trunk line when tested by said test contacts the switch will be barred from seizing the trunk line, and means for causing the switch to seize the trunk line consequent to testing if none of the said specific conditions exists.

48. In a telephone system, a switch, a trunk line subject to seizure from the switch, a plurality of test terminals of the said trunk line each of which will manifest a different specific condition of the trunk line, the test terminals being subject to test by the switchthrough respectively cooperating test contacts, means whereby if any said specific condition is manifested by the con dition of a test terminal of the trunk line when tested by the said test contacts the switch will be barred from seizing the trunk line, and means for causing the switch to seize the trunk line consequent to testing if none of the said specific conditions exists and to thereupon apply a said condition to one of said'terminals.

49. In a telephone system, a switch, a trunk line subject to seizure from the switch, a plurality of test terminals of the said trunk line each of which will manifest a different specific condition of the trunk line, the test terminals being subject to test by the switch through respectively cooperating test contacts, means whereby if any said specific condition is manifested by the condition of a test. terminal of the trunk line when tested by the said test contacts the first switch will be barred from seizing the trunk line, means for causing the switch 'to se ze the trunk line consequent to testing if none of the said specific conditions exists and to thereupon apply a said condition to one of said terminals, and means for causing the switch to unseze consequent to the termination of the said applied condition while a condition exists for barring the trunk line against subsequent seizure by the first switch.

.50. In a telephone system, a switch. a trunk line subject to seizure from the first switch, a normal inoperative conditionfor the trunk line, an operative condition of the trunk line, a seized condition of the trunk line, a first and a second test terminal for the trunk line accessible for test from the switch, means for barring the sw tch from connecting to the trunk line controlled from a condition of either one of said terminals,

means whereby a normal inoperative condition of the trunk line will affect the first said terminal so as to bar the trunk line from se zure by the switch, means whereby an operative condition of the trunk line will render both said. terminals in condition for the seizure of the trunk line by the switch, and means whereby a seized condition of the trunk line will bar the sa d trunk line from seizure by the switch due tothe condition of only its said second terminal.

51. In a telephone system, a plurality of connecting link elements, sets of fixed contacts respectively corresponding to each connecting link element, common control mechanism interchangeably cooperative with the linkelements through any one of said sets of contacts to render a cooperated control mechanism and a connecting link element a complete connecting link, a common set of movable terminals of the control mechanism cooperative with the respective fixed contact sets, means whereby the control mechanism can be cooperated with but one link element at any time, and means whereby the control mechan sm will become automatically disconnected from the link element consequent upon a predetermined condition of the connecting link ensuing.

52. In a telephone system, a trunk line, talking conductors of the trunk line, two test conductors of the trunk line, means for causing the respective test conductors to manifest a different specific condition-of the trunk line, switch meansfor effecting connection to the talking conductors of the trunk line, and means responsive to either said specific condition of the trunk line for causing the corresponding test conductor to bar connection to the talking conductors of the trunk line. r

53. In a telephone system, a trunk line, a talking circu t of the trunk line, a plurality of test conductors of the trunk line, means for causing the respective test conductors to manifest a different specific condition of the trunk line, switch means for effecting connection to the talking circuit of the trunk line, and means respons ve to any said specific condition of the trunk line for causing the corresponding test conductor to bar coni ection to the talking circuit of the trunk 54. In a telephone system, a trunk line, a talking circuit of the trunk line, a plurality of test conductors of the trunk line, means for causing the respective test conductors to manifest a different specific condition of the trunk line, switch means for effecting connection to the talking circuit of the trunk line, means responsive to any said specific condition of the trunk line for causing the corresponding test conductor to bar connection to the talking circuit of the trunk line, and means whereby only .the termination nected said switclrfrom the trunk line while maintaining the trunk line barred to the other said switches.

56. In a telephone system, a trunk line, a plurality of sets of fixed terminals of the trunk line, a plurality of switches, each switch specific to a said set of terminals, means whereby any said switch may connect to the trunk line through its specific fixed terminals, means for barring connection to the trunk line by more than one said switch at a time, and means for disconnecting a connected said switch from the trunk line while maintaining the trunk line barred to the other said switches and the disconnected switch. 7

57. 111 a telephone system, a switch, a trunk line subject to seizure from the switch, two test terminals of the trunk line each of which will manifest a different specific contest terminals of the trunk line each of which will manifest a different specific condition of the trunk line, the test terminals being subject to test by the switch, means whereby it either said specific condition of the trunk line exists when the test terminals are. tested by the switch the switch will be barred from seizing the trunk line, and

means whereby if both said specific condi tions of the trunk line exist when the test terminals are tested by the switchthe switch will be barred from seizing the trunk line.

59. In a telephone system, a switch, a trunk lme subject to seizure from the switch, a plurality of test termlnals of the trunk line each of which will manifest a difnals of said second switch, means whereby said first switch can be operated into selective relation to said second switch, means for said first switch to seize the selected said second switch, a plurality of said terminals for individually manifesting a different speclfic condition of said second switch, and means whereby it a said specific condition is manifested by oneof said test terminals said first switch will be barred from seizing said second switch when its terminals are selected.

In witness whereof, I hereunto subscribe my name this 21st day of October, A. D.,

HERBERT M. FRIENDLY.