US1672970A

US1672970A - Machine switching telephone system

Info

Publication number: US1672970A
Application number: US477894A
Authority: US
Inventors: Jr Samuel B Williams
Original assignee: Western Electric Co Inc
Current assignee: AT&T Corp
Priority date: 1921-06-16
Filing date: 1921-06-16
Publication date: 1928-06-12
Anticipated expiration: 1945-06-12
Also published as: FR552837A; GB181705A

Description

June 12, 1928.

MARGINAL 5. B. WILLIAMS, JR

MACHINE SWITCHING TELEPHONE SYSTEM Filed une 16. 1921 '7 Sheets-Sheet 1 June 12, 1928. 1,672,970

s. B. WILLIAMS, JR

MACHINE SWITCHING TELEPHONE SYSTEM Filed June 16 1921 7 sne ts sneet MAiEl/V/IL awk- 14 iffy June 12, 1928. 1,672,970

s. B. WILLIAMS, JR

MACHINE SWITCHING TELEPHONE SYSTEM Filed June 16 1921 7 Sheets-Sheet 5 AMEN/VAL fi amwi My June 12, 1928. 1,672,970

s. B. WILLIAMS, JR

momma swmcruue TELEPHONE SYSTEM Filed June 16, 1921 v sheets-Sheet 4 MACHINE SWITCHING TELEPHONE SYSTEM led June 16. 1 1 7 Sheets-Sheet 5 a -W w/y June 12. 1928. 1,672,970

S. B. WILLIAMS, JR

MACHINE SWITCHING TELEPHONE SYSTEM Filed June ts--Sheet //7 venfor; 50/1708/5 MW/am; Jr:

June 12, 1928.

1,672,970 s. B. WILLIAMS, JR

MACHINE SWITCHING TELEPHONE SYSTEM I Filed June 16' 1921 7 Sheets-Sheet 7 SENDER A SENDER SENDER CONTROL cmcun' Patented June 12, 1928.

UNITED STATES PATENT OFFICE.

SAMUEL B. WILLIAMS, JR., OF BROOKLYN, NEW YORK, ASSIGNOR TO WESTERN ELEC- TRIO COMPANY, INCORPORATED, OF YORK.

NEW YORK, N. Y., A CORPORATION OF NEW MACHINE SWITCHING TELEPHONE SYSTEM.

Application filed June 16,

This invention relates to telephone systems and particularly to machine switchingsystems wherein connections are established by means of mechanisms of the type generally known as c-ross-bar switches.

The object of this invention is to improve automatic telephone systems of the type employing register controlling mechanisms arranged in common to a plurality of selective switches and connectable to desired ones of said switches to selectively control the same to establish conversational connections.

Another object of the present invention is to improve subscriber controlled machine switching telephone system by increasing its flexibility or the ease with which the varying conditions of traflic may be accommodated without deranging the system.

A feature of the invention relates to a system employing selective switches having coordinate rows of contacts and intersecting bars for operating said contacts together with common register mechanisms for controlling the operation of said switches.

One special feature of this invention is the arrangement of trunks. By using mechanisms of the general type of cross-bar switches, it has become possible to do away with set grouping of trunks, since no trunk hunting is required. Accordingly the trunks may be grouped together or they may be scattered in any manner. The equivalent trunks of a group may or may not be placed physically adjacent one another.

Thus when traffic conditions in a certain group of trunks become abnormal, more trunks may be added to the group without re-arranging the system.

The invention. is shown in placed, Figs. 1, 2 and Figs. 6, 5 and 4 side under Figs. 1, 2 and 3, respectively. diagrammatically illustrate the circuits for a preferred embodiment of the invention. Fig. 1 shows two telephone lines and a primary switching arrangement, together with a master switch circuit for piloting the connections; Fig. 2 shows a secondary switching arrangement whereby trunks from the primary switching arrangement may be connected to either outgoing or incoming trunks. There is also shown a master switch arrangement for piloting connections through such secondary switching arrangesix figures which 3 side by side, and by side and directly 1921. Serial No. 477,894.

ment. To the right is shown an incoming trunk selector together with a ringin arrangement for ringing the bell of the called subscriber. Fig. 3 shows a sender selector with the necessary master switch for pilotmg a connection. To the left is shown a trunk selector for extending a circuit from an outgoing trunk leading from the secondary switching arrangement of Fig. 2 toward the incoming trunk selector of Fig. 2.

The part of Fig. 4 to the left of the vertical broken lineand below the horizontal broken line shows the thousands selector marker with a master switch for piloting the connection through the trunk selector. Fig. 5 and the part of Fig. 4 to the right of the vertical broken line and tLbOWi the horizontal broken line show a sender for controlling the thousands marker and the line marker, the line marker being shown in Fig. 6 along with a master switch for piloting the connection therethrough. Fig. 7 is a diagram-. matic illustration of the system.

In general the operation of this system is as follows:

A telephone subscriber call starts the operation of a series of relays and cross-bar mechanisms which cause a line to be extended through the primary and secondary switching arrangements of Figs. 1 and 2 to an outgoing trunk in Fig. 3, and thence through the sender selector at the right of Fig. 3 to an idle sender. The subscriber upon dialing sets the sender of Fig. 5, whereupon the thousands marker of Fig. 4 causes the selection of a trunk through the thousands selector shown at the left of Fig. 3, and the selection of a line marker corresponding to the selected trunk. The line marker is also set into operation by the setting of the sender, whereupon the called line is tested and if found idle, a series of relays and cross-bar mechanisms are set into operation to extend the called line through the primary and secondary switching devices to an incoming trunk and thence upon initiating a through the incoming trunk selector to theof the called subscriber, the conversational circuit is completed through a repeating coil shown in the center of Fig. 3.

. Special attention is called to the arrangement of the trunks in the thousands selector to the left of Fig. 3. The trunks connected to the switch-

bars

341 and 349 be long to one group and illustrate the principle whereby the trunks may be physically scattered in any manner. Thus, the switchbar 348 is physically interposed between switch-

bars

341 and 349. If the thousands marker indicates a connection going in the direction taken by the trunk connected to bar 341 and this particular one is busy, then a circuit is extended instead of through the armature and back contact of relay 339 to the magnet 340, through the armature and front contact of relay 339 to the armature and back contact of relay 347, skipping the relay 346. In this manner the trunks in a group of equivalent trunks may be placed in an manner whatsoever and since no trunk huntlng action takes place, this arrangement may be adapted for as many or asfew trunks in a group as traffic conditions warrant and the changing from time to time of the number of trunks in a group, according to the variation of traflic.

It should be noted that while the system shown is a single office system or a four digit system the invention is not to be restricted thereto but may be extended to a larger or multi-ofiice system.

The switching means employed herein are referred to as cross-bar switches and may be of the type of construction shown in the patent to J. N. Reynolds #1,238,194, issued August 28, 1917.

Referring particularly 'to the diagram of Fig. 7, the subscribers lines 700 appear as calling lines in cross-bar line switches 701 having access to trunks leading to secondary line switches 702. The line switches 702 have access to trunks which extend to group selector switches 703, 714, etc. The group selector switches have access to numerical groups of trunks which lead to trunk selectors 704. These trunk selectors in turn have access to trunks leading to secondary line switches 705, which in turn have access to trunks leading to the primary line switches 706 and 720. These latter switches have access to the subscribers lines 707 as called lines. From the drawing it will appear that the lines may occur both as calling and called lines in the same primary line switches, but for clearness in illustration the usual convention has been employed in the diagram of Fig. 7 whereby the calling and called lines are shown as appearing in different switches.

After a subscribers line has been extended automatically through a primary line switch and a secondary line switch, a sender selector switch 798 is operated to further extend his line to an idle one of the senders 709, 710, 711, etc. The selected sender is responsive to impulses sent-over the line to record the designation of the wanted subscribers line. The device 712 is common to a number of senders and serves to supply ground potential through the senders to operate the group selector switches. The preference switching arrangement 713 is provided in order that. the preference among the senders may be varied whereby. no one sender will have a permanent preference over other senders-in the event of a number of senders attempting simultaneously to control the establishment of a connection.

After the record has been received in the sender, it controls the group selector switches 703, 714, etc., to select the desired group of trunks leading in the proper direction. Thereafter the sender is connected through a

device

715, 716, 717 to the proper one of a number of

line markers

718, 719, etc. Each line marker relates to a numerical group of lines as called lines which may appear in one or more of the primary line switches 706, 720, etc. After the marker is associated with the sender, the called subscribers line is marked in accordance with the record set up in the sender and the

switches

706, 705 and 704 are operated to extend the called line into connection with the chosen idle trunk in the proper numerical group leading from the group selector 703.

Following this, the sender selector 708, the sender 709 and the marker are restored to their normal condition and the conversational connection is held under the control of the subscribers line.

The establishment of a connection from substation 100 to substation 101, will now be described. When the subscriber at substation 100 removes his receiver from his switchhook, a circuit is established from ground, the inner left hand armature and back contact of magnet 102 over the loop of the substation 100,. back contact and out-- er left hand armature of magnet 102, right hand winding of.line relay 104 to battery. Relay 104 becomes energized and establishes a connection from battery, right hand low resistance winding of magnet 102, the left hand low resistance winding of line relay 104, front contact and inner left hand armature of line relay 104, back contact and inner left hand armature of relay 105, back contact and armature of relay 106, left hand armature and back contact of relay 107,

zti

ergized at this stage. Relay 108 establishes a circuit from battery, the left hand winding of relay 107, contact and armature of relay 108, back contact and armature of relay 123, back contact and left hand armature of relay 110, outer right hand armature and back contact of 'relay 115, conductor 109 to ground through the winding of relay 112. Relay 107 in attracting its arn'lature's causes the dee'nergization of relay 108 and stops the flow of current through the right hand winding of magnet 102. The adjust-- ment of

relays

107 and 108 is such that the locking circuit through the right hand winding of relay 107 is closed before the operating circuit through the left hand winding of relay 107 is opened at the contact of relay 108. A circuit is now established from battery, the right hand winding of relay 107, front contact and right hand armature of relay 107, back contact and right hand armature of relay 114, winding of relay 110, outer right hand armature and back contact of relay 115, conductor 109 and thence to ground through the winding of relay 112. Relay 110 becomes energized in this circuit and holds relay 107 energized through its right hand winding while opening the circuit of relay 107 through its left hand winding. Relay 110 in attracting its armatures extends the ground on conductor 109 through the back contact and outer right hand armature 'of relay 115, left hand armature and front contact of relay 110, armature and back contact of magnet 113, right hand armature and back contact of relay 117 winding the slow releasing relay 119 to battery. Relay 119 becomes energized and through its armature connects the ground on conductor 109 to the winding of relay 118, which in turn connects the ground of conductor 109 to the winding of relay 117. Relay 117 attracts its armatures and locks up to the ground on its right hand armature previously described. The movement of its armature Opens the circuit of relay 119 and this relay becomes deenergized after a. period determined by its adjustment. In the mean time relay 110 through its right hand armature connects ground on conductor 109 to the left hand armature of relay 115, through the back contact thereof and from thence through the winding of slow release relay 116 to battery. Relay 116 becomes energized, and attracting its armatures establishes a circuit from ground on conductor 109 through the contact and left hand armature of relay 116, the brush 124 and its first contact, armature and back contact of relay 121, the winding of magnet 120 to battery and ground. Magnet 120 controls the trunk bar 122 so that this trunk bar is actuated at this point. The trunk bar magnet 120 is now locked in a circuit from battery, winding of magnet 120, inner left-hand armature and front contact of magnet 120, left hand high resistance winding of relay 115, outer right hand armature and back contact of relay 111, front contact and right hand armature of relay 110 to ground on conductor 109. As long, however, as relay 121 remains deenergized relay 115 does not become energized since it has the same ground potential connection to each side of its left hand winding.

204, back contact and armature of relay 206,

left hand armature and back contact of relay 207, winding of relay 208, conductor 209, back contact and inner right hand armature of relay 21.1, winding of alarm relay 212 to ground.

Relays

208 and 212 become energized in this circuit but magnet 202 is not sufficiently energized in this circuit to attract its armatures.

The energization of relay 208 establishes a circuit from battery, the left hand winding of relay 207, the front contact and armature of relay 208, the back contact and armature of relay 223, the back contact and left hand armature of relay 210, the inner left hand armature and back contact of re lay 215 to ground on conductor 209 supplied through the winding of relay 212. Relay 207 opens the energizing circuit of relay 208, and stops the flow of current through the right hand winding of magnet 202. A circuit is noW established from battery, right hand winding of relay 207 front contact and right hand armature of relay 207, back contact and right hand armature of relay 214, winding of relay 210, inner left hand armature and back contact of relay 215 to ground on conductor 209, resulting in the energizetion of relay 210 and the holding of relay 207. Relay 210 establishes a circuit from ground on conductor 209, the back contact and inner left hand armature of relay 215. the left hand armature and front contact of relay 210, the armature and back contact of magnet 213, the right hand armature and back contact of relay 217, winding of relay 219 to battery and ground. Relay 219 connects the ground on conductor 209 to the winding of relay 218 which in turn connects the ground on conductor 209 to the winding of relay 217. Relay 217 locks up to the ground on its right hand armature and opens the energizing circuit of slow releasright hand armature and back contact of relay 241, switch brush 224, outer left hand armature and back contact of relay 221, winding of trunk bar magnet 220 to battery and ground. Trunk bar magnet 220 controls the trunk bar 222 so that this trunk bar is actuated at this stage. Trunk bar magnet 220 when energized establishes a circuit from battery, winding of magnet 220, inner left. hand armature and front contact of magnet 220, left hand high resistance winding of relay 215, outer left hand armature and back contact of relay 211,-right hand armature and front contact of relay 210 to ground on conductor 209. Relay. 215, however, does not become energized at present since the same ground potential of conductor 209 is connected to both sides of this winding.

Magnet 220 becoming energized connects ground from its outer left hand'armature to conductor 226 of trunk 300 which is thereupon extended through the right hand winding of trunk relay 304 to battery and ground. Relay 304 attracting its armature establishes a circuit from battery, right hand low resistance winding of magnet 302,- left hand low resistance winding of relay 304, front contact and inner left hand armature of relay 304, back contact and inner left hand armature of relay 305, back contact and armature of relay 306, right hand arlnature and back contact of relay 307,

winding of relay 308, conductor 309, winding of relay 312 to ground.

Relays

308 and 312 become energized in this circuit but due to the resistance of relay 308, the current flowing through the right magnet 302 is insufficient to cause the energization of magnet 302. Relay 308 in becoming energized establishes a circuit from battery, the right hand winding of relay 307, the front contact and armature of relay 308, the back contact and armature of relay 323, the back contact and right hand armature of relay 310, the outer left hand armature and back contact of relay 315 to ground on conductor 309 supplied through the winding of relay 312. Relay 307 is energized in this circuit and by attracting its armatures opens the circuit for relay 308 and stops the flow of current through the right hand winding of ma et 302. Relay 307 upon energizing estab ishes a locking circuit for 210, the outer left handhand winding of 5 itself from battery, left hand winding of relay 307, front contact and left hand armature of relay 307, back contact and left hand armature ofrelay 314, windin 310, outer left hand armature an back contact of relay 315 to ground on conductor 309. Relay 310 attracts its armatures thereby opening the original energizing circuit for relay 307. Relay 310 connects the ground on conductor 309 through the back contact and outer left hand armature of relay 315 right hand-armature and front contact of relay 310, armature and back contact of magnet 313, armature and back contact of relay 317, winding of slow releasing relay of relay 319 to battery and ground. Relay 319 becomes energized and connects the ground on conductor 309 to the winding of relay 317 which then locks up to the ground on its right hand armature and opens the energizlng circuit for relay 319. Relay 319 becomes deenergized and retracts its armatures after a definite interval determined by its adjustment.

In the mean time a circuit is established from ground on conductor 309 to the left hand armature and front contact of relay 310, right hand armature and back contact of relay 315, winding of relay 316 to battery. Relay 316 becomes energized and extends a connection from ground on conductor 309, left hand armature and front contact of relay 316, brush 324, left hand armature and back contact of relay 321. winding of magnet 320 to battery and ground. Magnet 320 establishes a locking circuit from battery, winding of magnet 320, inner left hand armature however, has the same ground potential from conductor 309 connected to both sides of the winding so that it does not energize at this stage. i

The magnet 320 controls the trunk bar 322 so that it is actuated at this time. The energization of magnet 320 also connects round to the outer left hand armature of magnet 320 thence through the winding of relay 321 to battery. Relay 321 becoming energized opens the original energizing circuit of magnet 320 so that relay 315 is no longer short circuited and it therefore becomes energized. A circuit is now established from battery, the right hand low resistance winding of magnet 302, the left hand low resistance winding of relay 304, front contact and inner left hand armature of relay 304, back contact and inner left hand armature of relay 305, back contact and armature of relay 306, armature and front contact of relay 307, low resistance left hand winding armature an contact of relay 315, front of relay 315, inner left hand A circuit 1s now established from battery,

- resistance 328, windin of magnet313, the left hand armature an front contact of relay 317 and armature of relay 319 to ground on conductor 309. As soon as relay 319 becomes deenergized magnet 313 steps the brush 324 on to its next contact and thereby varies the order of preference for the o eration of the trunk bars. The operation of magnet 313 opens the locking circuit of relay 317 so that it becomes deenergized.

Magnet 302 upon attracting its armatures extends ground through the inner left hand armature and front contact of magnet 302, the front contact and outer left hand armature of relay 304, winding of relay 306 to battery and ground. Relay 306 in attracting its armature closes a locking circuit as follows: Battery, through the winding and contact of relay 306, right front contact of so relay 307, left winding and front contact of relay 315, left contact of relay 316, to round on conductor 309. After an interval ollowing the operation of relay 315, the slow releasing relay 316 releases, opening the cm cult of

relays

306 and 315 and these relays release. Relay 316 also opens the circuit of

relays

307 and 310, permitting these relays to deenergize. As will be explained later, the original operating circuit'of relay 306 is opened prior to the release of relay 316 to insure the release of relay 306 at the time said relay 316 deenergizes.

The trunk bar magnet 320 now becomes deenergized but the line bar magnet 302 maintains the connection between the crossbars. The deenergization of magnet 320 opens the circuit of relay 321, but this relay being slow to release does not retract its armatures immediately. In the mean time a circuit is established from ground, front contact and outer left hand armature of relay 321, conductor 402, right hand armature and back contact of relay 500, conductor 403, the corresponding contacts of the crossbars to conductor 329 and thence in parallel through the winding of relay 330 and two windings in series of magnet. 302. Relay 330 disconnects the repeating coil 344 from the trunk leading from the secondary line switch and also the trunk leading to the thousands selector so as to leave a free pair of wires to the sender.

A circuit is also established from ground, the outer left hand armature and front contact of magnet 302, winding of relay 331 to battery. Relay 331 attracts its armature and extends a connection from ground, the front contact and armature of relay 331, conductor windingof relay 221 to battery and groun Relay 221 attracts its armatures and by opening the original energizing circuit of magnet 220 removes the short circuit from around the high resistance'winding of relay 215 which thereupon becomes energized. A circuit is now established from battery, right hand low resistance windin of line bar magnet 202, low resistance rig t hand winding of line relay 204, front contact and inner right hand armature of relay 204, back contact and armature of relay 206, left hand armature and front contact of relay 207, low resistance righthand winding of relay 215, front contact and right hand armature of relay 215, right hand armature and front contact of relay 216, to ground on conductor 209 supplied through the winding of relay 212. Line bar magnet 202 becomes energized in this circuit and operates the line bar so that the contacts of the two operated crossbars become engaged. A circuit is now extended from ground, inner left hand armature and front contact of relay 221, through the corresponding cross-bar contacts to con ductor 227, left hand winding of relay 121 to battery and ground. Relay 121 in opening the original energizing circuit of mag net 120, removes a short circuit from around the high resistance winding of relay 115 whereupon it becomes energized. A circuit is now established from battery through low resistance right hand winding of line bar magnet 102, the low resistance left hand winding of line relay 104, front contact and inner left hand armature of relay 104, back contact and inner left hand armature of relay 105, back contact and right hand arma ture of relay 106, left hand armature and front contact of relay 107, right hand low resistance Winding of relay 115, inner right hand armature and front contact of relay 115, left hand armature and front contact of relay 116, to ground on conductor 109, supplied through the winding of relay 112. The line bar magnet operates in this circuit and brings its contacts into engagement with the corresponding contacts of the trunk bar 122 so that the subscribers loop circuit is now extended through the contacts of the primary line switch contacts, the secondary line switch and the contacts of the sender selector switch through the back contacts and left hand armatures of relay 404 to the windings of relay 405 causing the energization of the latter relay. The energization of relay 405 results in the energization of slow releasing relay 400 and this in turn places a ground on conductor 401 to hold relay 321 energized.

Upon the energization of the line bar magcontact of relay 216, to ground at conductor 209. Ground on conductor 227 is also extended through the corresponding contacts of the line and trunk bar contacts in the primary line switch to hold the line bar magnet 102 energized through both of its windings in series.

Upon the deenergization of rela 219, the circuit of relay 218 is opened an after an appropriate interval this relay also retracts its armatures and a circuit is established from battery, resistance 228, winding of stepping magnet 213, left hand armature and front contact of relay 217, back contact and armature of relay 218 to ground on conductor 209. Magnet 213 steps the

brushes

224 and 229 of said switch thus changing the order of preference for the in and out trunk bars of the secondary line switch. The operation of this magnet also opens the holding circuit for relay 217 which thereupon deenergizes and in turn opens the energizing circuit for magnet 213. After the necessary interval, slow relay 216 releases and brings about a release of the relays associated with the secondary switch in a manner similar to that described in connection with the sender selector. As will be seen hereinafter, the original operating circuit of relay 206 is opened prior to the o eration of relay 216, which'causes the opening of the locking circuit of relay 206.

In a similar manner brush 124 is stepped to its second contact to varythe order of preference of the primary line switch and the controlling relays at that point become deenergized. At the time magnet 102 operates, it opens the circuit of line relay 104. Relay 104 is adjusted to hold its outer left contact closed for a brief interval following the closure of the inner left contact of magnet 102. Hence the relay 106 is operated in an obvious circuit and locks as follows: From battery, through the winding and contact of relay 106, left front contact of relay 107, right winding and contact of relay 115, left contact of relay 116, to ground on conductor 109: After an interval following the operation of relay 115, relay 116 releases and causes the release of relays 106 and 115.

Relays

107 and 110 are also released by having their locking circuit opened at the right contact of relay 116. Magnet 120 also releases and opens the circuit of relay 204, which in turn opens the original circuit of relay 206.

At the time ma et 220 releases, it opens the circuit of re ay 304 which opens the original circuit of relay 306. The slow relays 116, 216 and 316 are timed to release in such a manner that b the time relay 216 has released to open t 1e locking circuit of relay 206, the OII lIHIl circuit of relay 206 will have alread been opened by the release of relay 116. lso, by the time relay 316 releases to open the holding circuit of relay 306, the relay 216 will already have released to permit the opening of the original circuit of relay 306. Thus, relays 106, 206 and 306 are prevented from initiating a false operation of the control circuits.

The connection is now in a stable condition awaiting the receipt of impulses for selecting the called substation.

Let it be assumed that the number of the line leading to station is 5555 and the number of the line leading to substation 101 is 5554. The subscriber at substation 100 now manipulates his dial switch to send five impulses which are in the nature of five short interruptions of the line circuit. This results in the retraction of its armature by relay 405, five times in quick succession. Upon the first retraction a circuit is established from ground, armature and back contact of relay 405, back contact and outer right hand armature of relay 404, front contact and right hand armature of relay 400, outer left hand armature and back contact of relay 406, conductor 407, brush 501, and its first contact, winding of magnet 502, conductor 503, winding of slow releasing relay 504 to battery and ground. Magnet 502 and relay 504 become energized in this circuit. Rela 504 thereupon establishes a connection rom ground, armature and contact of relay 504, winding of magnet 505, winding of relay 506 to battery and ground. Upon the attraction of its armature by relay 405, the magnet 502 becomes deenergized and drives the switch arms controlled by it (shown in a "ertical line beneath it) on to their first contacts. Relay 504 being slow to release does not respond to this short break in its circuit. Five such impulses result in the placing of switch arm 507 on its fifth contact, thereby making connection to conductor 508. Relay 405 then maintains its armatures attracted for a comparatively long period before the receipt of the next series of impulses whereupon relay 504 releases is arlnature, opening the circuit for magnet 505 and rela 506. Magnet 505 becoming deenergized brings the switch arms controlled by it to their first contacts so that thecircuit through brush 501 now leads to magnet 509.

A circuit is now established from round, right hand armature and contact 0% relay inner right hand 321, conductor 408, conductor 409, brush 510 and its first contact, conductor 511, winding of relay 410 to battery and ground, resulting in the energization of the latter relay. Relay 410 looks up in a circuit from ground, armature and back contact of relay 411, outer right hand armature and back contact of relay 412, left hand armature, front contact and winding of relay 410 to battery and ground. Relay 410 in turn places a ground on the winding of relay 413 through its-inner right hand armature. Relay 413 attracts its armature and establishes a circuit from ground, inner right hand armature and back contact of rela 411, right hand armature and back contact. of relay 414, brush 415 and its first contact, the left hand armature of relay 413' and its front contact, right hand winding of relay 416 to battery. Relay 416 becomes establishes a circuit from battery, windlng of magnet 417, left hand winding of relay 416, front contact and left hand armature of relay 416, first contact and brush 418, winding of slow releasing relay 414, back contact and right hand armature of relay 411 to ground. Relay 414, in attracting its armature opens the original energizing circuit through the right hand winding of relay 416 and connects the ground on its right hand.

armature through the right hand armature of relay 416, brush 419 and its first contact, the outer right hand armature and front contact of relay 410, winding of relay 412,

. winding of magnet 420 to Battery whereby relay 412 is energized in series with the magnet 420. A circuit is also established from ground, inner right hand armature and back contact of relay 411, left hand armature and front contact of relay 414, right hand armature and back contact of relay 421, relay 422 to battery. Relay 422 becomes energized and establishes a circuit from ground, armature and frdnt contact of relay 422, middle left hand armature and contact of relay 412, conductor 423, through the corresponding confacts of. the sender selector switch, conductor 333, right hand armature and back contact of relay 334, winding of magnet 335 to battery and ground. Magnet 335 actuates the trunk bar 336. The operation of trunk bar magnet 335 closes a circuit from ground, winding of relay 337, outerleft hand arma ture and front contact of magnet 335, conductor 338, winding of relay 421 to battery and ground. -The operation of relay 421 establishes a circuit from ground, inner left hand armature of relay 421, outer left hand armature and front contact of relay 412, brush 507, conductor 508, outer left hand armature and front contact of relay 337, right hand armature and back contact of relay 339, right hand winding of magnet 340 to battery, whereupon magnet 340 becomes 1 energized and brings the cont-acts of the bar bars 336 and v armature of energized and e 34.1 into engagement with contacts of the trunk bar 336. Acircuit is now established from ground, right hand arinatureand front contact of relay 221, conductor 230 corresponding contacts of switch 341, front contact and left hand magnet 340, the left hand winding of magnet 340, the winding of relay 339, the righthand winding of ma net 340, to battery, so that when the groun onconductor 508 is removed, magnet 340 will remain energized through both of its windings in series and relay 339 will become energized. The energization of relay 421, opens the circuit of relay 422 which becomes deenergized in a short interval (determined by its adjustment) and removes the ground from conductor 423 and] opens the original circuit of trunk bar magnet 335. A substitute holding circuit is established before relay 422 retracts its armatures, from ground outer left hand armature and front contact of relay 421, normal contacts of the left hand armature of relay 411 "and thence over the circuit previously described and this circuit remains established until relays 411 and 334 are energized as will shortly appear. Upon the energization of relay 337 a circuit is completed from battery, winding of relay 334, front contact and inner left hand armature of battery and ground. Relay" 512 looks up through its front contact and inner right hand armature and back contact and left hand armature of relay 500 to ground on conductor 408. Relay 424 also establishes a circuit from ground the inner left hand armature and front contact of relay 424, winding of relay 411 to battery and ground. Relay 411,1ocks up in a circuit extending from ground, outer left hand armature and front contact of relay 421, inner left hand armature and front contact of relay 411 to battery and ground. Through its outer right hand armature relay 411 short circuits the left hand high resistance winding of relay 424 so that relay 334 now becomes energized. Relay 334 locks up through its front contact and left hand armature to the ground on conductor 230 and by means of its right hand armature opens the circuit of magnet 335. This magnet becomes deenergized and in retracting its armatures opens the circuit for relay 424 which now becomes deenergized.

The movement of its inner right hand armature by relay 411 opens the circuit for relay 414 and magnets 417 and 420 so that the corresponding being required to wait.

brushes 418 and 415 controlled by the magnet 417 move to their second positions andbrush 419 controlled by magnet 420 moves to its second position. Relay 416 heretofore held energized in series with ma net 417 becomes deenergized. Relay 412 held up 1n series with magnet 420 also becomes de-energized whereupon the deenergization of magnet results in the deenergization of relay 421 which in turn allows relay 411 to return to normal. This returns all of the relays of the connector master switch to normal.

All the above described action takes place in an extremely short interval of time so that the connection of the switch bars 341 and 336 is accomplished generally but not necessarily before the subscriber at station 100 dials his second series of impulses.

It may be noted at this point that the several senders are so arranged-that they may be only taken in use one at a time in the event two or more of them are attempting simultaneously to become associated with a group selector switch. For this purpose, a preference arrangement including the switches 417 and 420 is provided. The equipment below the horizontal broken line in Fig. 4 is common to all of the senders and may be associated with only one sender at a time. The preference switches serve to vary the preference of the senders in appropriating for use this common equipment.

\Vith the preference switches standing in a I if two senders are attempting to appropriate the common circuitsimultaneously, one of them, depending upon the position of the switch, will have preference over the other and will succeed, the other For each use of a sender, the preference switch is advanced one position, thereby changing the order of preference.

It should be noted at this point that if there are no available trunks leading to the fifth thousands group of lines, then a cirgiven position,

cuit will be established from ground, innerleft hand armature and front contact of relay 421, the outer left hand armature and contact of relay 412, brush 507 and its fifth contact, conductor 508, outermost left hand armature and contact ofrelay 337, armature and front contact of relay 339, thence in series through the armatures and front contacts of all other relays corresponding to relay 339 in the group of trunks leading in the desired direction, conductor 342, inner right hand armature and front contact of relay 412, winding of relay 406 to battery. Relay 406 will become energized in this circuit and complete a locking circuit from battery, winding of relay 406, front contact and right hand armature of relay'406, conductor 409, conductor 408, front contact and right hand armature of relay 321 to ground. Through its outer left hand armature relay 406 opens the impulse circuit to the sender, and through its inner left hand armature it connects a source of busy-tone through the condenser 425 to one winding of relay 405 whence it is transmitted by induction to the subscribers telephone instrument at substation 100.

If the subscriber hangs up his receiver, re-

lay 405 will become deenergized, resulting the hundreds digit of the called linel -This results in the setting of the brushes under the control of magnet 509 onto their fifth contacts. In a similar manner, the brushes controlled by the

magnets

513 and 514 are set onto their fifth and fourth contacts, respectively. At the end of the last series of impulses, brush 510-comesto rest on its fourth contact, whereupon a circuit is established from ground, right hand armature and contact of relay 321, conductor 408, conductor 409, brush 510, its fourth contact, front contact and outer right hand armature of relay 512, brush 515 and its fifth contact,

conductor 516, winding of relay 600 to battery. Relay 600 attracts its arinatures and establishes a circuit from ground, the inner left hand armature and front contact of relay 600,- winding of relay 601 to battery. Relay 601 in turn becomes energized and establishes a circuit from ground, the outer left hand armature and back contact of relay 602, the right hand armature and back contact of relay 603, brush 604 and its first contact, armature and front contact of relay 601, right hand winding of relay 605 to battery. Relay 605 becomes energized and thereby establishes a locking circuit for itself from battery, winding of magnet 606, left hand winding of relay 605, front contact and left hand armature of relay 605, first contact and brush 607, winding of relay 603, back contact and outer left hand armature of relay 602 to ground. A circuit is now established from ground, left hand armature and front contact of relay 603, the

outer left hand armature and front contact of relay 600, winding of rela 611, windin of magnet 612, to battery. Relay 611 an magnet 612 become energized. Upon the energization of relay 611 a locking circuit is completed from ground, outer left hand armature and front contact of relay 602 left hand armature and front contact of relay 611, winding of rela 611, winding of magnet 612, to battery. he movement of the outer left hand armature of relay 602 opens the original energizing circuit for relay 603, butv a substitute locking circuit is establi hed from ground, left hand armature'and front contact of relay 603, left hand armature and back contact of relay 617, front contact and right handarmatureof relay 603,.winding of relay 603, brush 607' and its first contact, left hand armature and front contact of relay 605, left hand winding of relay 605, winding of ma battery. A circuit is now established from ground, left hand armature and front contact of relay 603, left hand armature and back contact of relay 613,'right hand armature and front contact of relay 602, outer left hand armature and back contact of relay 614, winding of relay 615, to battery.

Upon the energization of relay 600, a circuit is established from ground, outer ri ht hand armature and front contact of re ay 600, conductor 539, brush 540, back contact and armature of magnet 505, winding of magnet 505, winding of relay 506 to bat.- tery and ground. This results in the automatic o eration of magnet 505 and the movement of its brushes on to their next contacts so that the original energizing circuit (through brush 510) of relay 600 IS opened. By this time, however, relay 602 has become operated so that relay 600 is held energized in a circuit extending from ground, left hand armature and front contact of relay 602, left hand armature and back contact of relay 611, inner right hand armature and front contact and winding of relay 600 to battery and ground. Upon the energization of relay 611, relay 600 becomes deenergized, thereby releasing relay 601, which, now that relay 603 has become ener ized, has no fu ther function to perform. elay 600 also opens the original energizing circuit of relay 611 and magnet 612.

Relay 611 establishes a circuit from ground, front contact and outer ri ht hand armature of relay 611, winding 0 magnet 517, to battery. Magnet 517 controls a large number of contacts which are closed upon the energization of this magnet.

It may be noted at this time that the relays shown in the space set off by the broken lines at the bottom of Fig. 6 relate to the particular sender shown in Fig. 5. There is a set of these relays in the marker for each at 606 to.

the primary line switch master switch is now busy relay 112 will be energized and the connection will remain inthe condition just described and no further action will take lace. If,,however, the rimary line switc master switch is idle and this connection may proceed, a circuit is established from battery, winding of relay 111, back contact and right hand armature of alarm relay 112, conductor 127, front contact and inner left hand armature of relay 602,-back contact and left hand armature of relay 617, frontcontact and left hand armature of relay 603, to ground. Relay-111 is energized in this circuit and establishes a circuit for relay 125, extending from ground, front contact and outer left hand armature of relay 111, winding of relay 125, to battery. Through its inner left hand armature, relay 111 islocked to the ground on conductor 127. Upon the energization of relay 125 a circuit is established from ground, front contact and outer left hand armature of relay 125, winding of relay 614 to bat tery. .Relay- 614 closes a circuit from battery, through the winding of slow-release relay 616, front contact of relay 609, left front contact of relay 614, right contact of relay 602, left back contact of relay 613, to ground at the left contact of relay 603. I

A circuit is now established from ground, winding of alarm relay 112, inner right hand armature and front contact of relay 111, brush 124 and its second contact, left hand armature and back contact of relay 128, winding of the trunk bar magnet 129, to battery.' Trunk bar magnet 129-controls the trunk bar 130 so that this is actuated at this stage. The actuation of the trunk bar ma et 129 also results in the establishment 0 a circuit from ground, front contact and inner right hand armature of relay 125, middle left hand armature and front contact of magnet 129, conductor 131, left hand armature and back contact of relay 212, winding of relay 211, to battery. Relay 211 looks up through its front contact and inner left hand armature to the ground on conductor 131 and establishes an energizing circuit for relay 241, extending from ground, front contact and outer right hand armatureof relay 211, winding of relay 241 to battery.

Relay 241 closes an obvious circuit for relay 608. Relay 608 locks in the following circuit: Battery, through the winding and front contact of relay 608, to

mature and front contact 0 relay 211% right hand armature and front contact 0 ay 241, brush 229 and its second position contact, armature and back contact of rela 233, winding of magnet 234 to battery. It agnet 234 controls the trunk bar 235 so that it becomes actuated at this stage. Thereupon a circuit is closed from ground ri ht hand armature and front contact of relay 614, conductor 619, outer left hand armature and front contact of magnet 234, winding of magnet 236 to butter Magnet 236 controls the trunk bar 237 o the trunk finder so that this trunk bar becomes actuated at this sta When relay 241 operates, it closes an o i 'ious circuit for relay 618. The relay 518 is now 0 erated in a circuit froin'battery, throu h tie winding thereof, contacts of relay 51 7, conductor 520, inner left contact of relay 614, to ground at the V left front contact of relay 618.

The energization of relay 518 establishes several circuits as follows: From ground, outer right hand armature and front contact of relay 518, brush 521 and its fifth position contact, conductor 522 through the corresponding contacts controlled by magnet 517 to conductor 523, winding of relay 620 to battery. Rela 620 becomes encrized in this circuit. Ytelay 518 also estab ishcs a circuit from ground, inner right hand armature and front contact of relay 518, brush 524 and its fifth position contact, conductor 525, coricspondin contacts controlled by magnet 517 to con uctor 526, outer left hand armature and front contact of relay 620, winding of relay 621 to battery whereupon relay 621 becomes energized. )1 third circuit is now established from ground, inner left hand armature and front contact of relay 518, brusb 527 and its fifth position contact, conductor 528, brush 529 and its fourth position eontact,conductor 530, through the corres ending contacts controlled 'b magnet 51 to conductor 531, outer 1e t hand armature and front contact of relay 621, winding of relay 622 to battery whereupon relay 622 becomes energized. Another circuit is established through the windings of magnet 103, conductor 132, the inner ri ht.

hand armature and front contact of re ay 622, conductor 532, through the correspon ing cont-acts cont-rolled b magnet 517 to conductor 533, fourth position contact and brush 534, front contact and outer left hand armature of relay 518, conductor 535, corresponding contacts controlled by magnet 517 to conductor 536. to the left hand armature of rela 615. These circuits are established round this time the energizing circuit for relay 615, is opened, but being slow to release,

it maintains its armatnres attracted for an interval. During this interval, therefore, the circuit just traced to the let t hand armature of relay 615 is connected to the front contact, and thence to the winding of relay 613. If the called line 5554 is busy, ground potential will be found on conductor 132 and relay 613 will become ener ized. 'lhereupon a circuit will be establisied from ground, inner right hand armature and front contact. of relay 613, front-contact and innermost right hand armature of relay 611, conductor 623 to the winding of relay 406, which. will result as before in connecting busy time to the calling line. 'The ener ization of relay 613 also establishes a eiicuit from ground, outer right hand armature of relay 613, winding of relay 617 to battery resulting in the energization of relay 617; clay 617, in attracting its left hand armature, opens the energizing circuit for relay 603, relay 605 and magnet 606, whereupon these relays and ma nets. become decncrgized.

ic deenergization of magnet 606 causes the arm 610 to more to its second position contact. The energization of relay 617 closes a circuit from ground, front contact: and outer right hand armature of relay 617 to the left hand windin of relay 602, and thence to battery, provi i iing a holding circuit for relay 602 so that its outer 1c 1 1 -hand arina ture wi i not again cause the energization of relay 603. The cnergization of relay 617 also owns a circuit for relay 11.1 which, througi its control of'relay 125, causes the deenergization of this latter relay.

The dcenergizatiou of relay 125 and magnet 129 removes the round from conductor l3l so that relay 211 ieconics dccncrgizcd resulting in the dccncrization of relay 2 11 whereupon the grount is removed from the winding of relay 608 and this relay in retracting its armature opens the circuit for relay 617, thereby causing the dccncrgization of relay 617 and relay 602. Relay 602 on deencrgizing opens the holding circuit for relay 611 and magnet 612, which thereupon bccome deenergized, magnet 612 driving the

arms

604 and 607 to their second positions. The dcenorgizat-ion of relay 611 opens the circuit for nnignet. 517 which upon retracting its armature opens the circuit. for the marking relays 620, 621 and 622 and the controlling relay 518. With these controlling relays dccncrgizcd. it is obvious how the trunk bar magnets 120. 234 and 236 now become dcenergized. The sender and marker have now been returned to normal. The circuit is now in the following condition. The calling line 5555 is connected through the primary and secondary line switches through the sender selector to the upon tie energization of relay 614, and at register in Fig. 5, and the loop at the sublil station 100 causes the continued energization of relay 405. Busy tone is transmitted to the calling linethrough. the front contact and inner left hand armature of relay 406 and this condition will be maintained until the subscriber replaces his 'receiver on its switchhook. When that happens, relay 405 becomes deenergized' causing in turn the net 505, windin of relay 506, to battery.

Relay 506 provides a substitute gro nd for that supplied at the front contact 0' relay 400, so that the relay 321 does not deenergize immediately. Magnet 505 being in a selfdnterrupting circuit, vibrates its armatures and drives the brushes controlled by it to their normal positions whereupon the ground on brush 537 is extended to brush 538 and the thousands register controlled by magnet 502 is returned to normal. Thereupon the ground on brush 538 is extended to the hundreds register until it is returned to normal, thence. to the tens registeruntil it is returnedto normal and finally to the units register until it is returned to normal. After the brushes controlled by magnet 505 have been returned to their normal position, relay 506 becomes deenergized and removes the ground from the winding of relay 321, whereupon this relay becomes deenergized. In retracting its armatures, relay 321 removes ground from conductor 402,, thus opening the circuit for the line bar magnet 302 and the relay 330 which become deenergized. Line bar magnet 302 in retracting its armature opens the circuit for relay 331 so that ground is now removed from conductor 332, resulting in the deenergization of relays 221, 121, the

magnets

202 and 102, thus restoring the entire connection to normal.

Another condition other than the bus condition of the particular line calle which will cause the energization of relay 613 is the case in which all trunks leading from the primary line switch are busy. In this case a circuit will be established from ground, right hand armature and front contact of relay 121, right hand armature and front contact of relay 128 to the winding of relay 613 to battery, whereupon the busy' tone will be given to the calling subscriber in the manner just described.

Let us assume that line No. 5554 is idle, then conductor 132 will have no ground potential, and battery through magnet 103 will be opposed to battery through relay 613, and this relay will not become energized. In a short interval thereafter, relay 615 will retract its armatures, whereupon the circuit through the left hand armature of relay 615 will be switchedto the back contact and.

armature of relay 609, the front contact and outer left hand armature of relay 614, front contact and right hand armature of relay 602, back contact and left hand armture of relay 613, front contact and left hand armatureof relay 603 to round. This will cause the energization of ine bar magnet 103, so that the line 5554 will now be connected to trunk 201. A circuit will now be established from ground, outer left hand armature and front contact of relay 241, front contact and outer right hand armature of relay 125, outer left hand'armature and contact of magnet 129, conductor 134, left hand winding of relay 205 to battery, resulting in the energization of this relay. The energization of rela 125 results in the establishment" of a circuit from ground, the left hand armature and front contact of relay 603, left hand armature and back contact of rely 613, the right hand armature and frontcontact of relay 602, the back contact and right hand armature ofrelay 615, right hand armature and front contact of relay 618 (energized in response to the energization of relay 241) the front contact and innermost left han armature of relay 125, the left hand armature of relay 205, right hand winding of magnet 203 to battery, whereupon this magnet becomes energized and connects the contacts of switch bar 238 to the contacts of trunk bar 235, extending the line 5554 to the contacts of trunk finder bar 237. Relay 231 is energized in a circuit from battery winding of relay 231, conductor 232, corresponding contacts of switch-

bars

341 and 336, conductor 333, corresponding contacts of

switchbars

327 and 322, conductor 423, corresponding contacts controlled by magnet 517, conductor 537, back contact and left hand armature of relay 617, front contact and left hand armature of relay 603 to ground. The

energization of magnet 236, heretofore described, establishes a circuit from ground,

front contact and armature of magnet 236, front contact and armature of relay 231, winding of magnet 239 to battery. Magnet 239 actuates the line bar 240 so that the called line is now extended to the trunk bar 237. Magnet 239 also closes a circuit through its front contact and armature extending from ground to the winding of relay 244. Relay 244 becomes energized and places a ground through its front contact and inner left hand armature on the third conductor of the trunk leading to the called What is claimed is:

1. In a tele hone system, a plurality of trunk lines divided into groups of equivalent trunk lines, machine switching means comprising permanentl paired primary and secondary contact evices for making connections to said trunk lines, the trunk lines of said groups being promlscuously interspersed in their appearance in said switching means, and a starter wire arrangement 1ndividual to each group of trunk lines for controlling the operation of said switching means.

2. In a telephone system, a pluralit of groups of equivalent trunk lines, mac ine switching means comprising permanently paired primary and secondary contact devices for making connections to said trunk lines, the trunk lines of said gpoups being promiscuously interspersed in t eir appearance in said switching means, and means individual to each of said groups of trunk lines for controlling the operation of said switchin means to make a connection to the first id e trunk of a group.

3. In a telephone system, a tele hone line, non-numerical switching means or extending said line, numerical switching means for further extending said line, a plurality of groups of numerical trunk lines accessible to sa1d line through said numerical switching means, said trunks of said grou s being promiscuously interspersed in their appearance in said numerical switching means, a starter wire for controlling the operation of said numerical switching means lndividual to each group of trunks, and means individual to each trunk of a group for extending said starter wire to the next idle one of said trunks.

4. In a tele hone system, a tele hone line, non-numerical switching means or extending said line, a sender controlled from said line to pilot the further extension of said line, a sender selector for extending said line to said sender, machine switching means for extending said line in a direction ointed out by said sender, a marker contro led by said sender for initiating the operation of said machine switching means, ups of equivalent trunks leading from sai machine switching means, the trunks of said groups being promiscuously interspersed in their appearance in said machine switching means, and a starter wire individual to each of said groups controlled by said marker to control the operation of said machine switching means to instantaneously extend said line over the next idle one of the group of trunks directed by said sender.

5. In a telephone system, a calling and a called line means under control of said calling line or establishing a by-path connection between said lines, non-numerically controlled primary and secondary cross bar switches for extending said calling line to said means, and cross bar switches under control of said means for establishing a talking connection between said lines.

6. In a telephone system, a calling and a called line, means for establishing a bypath to said called line, primary and secondary switches for extending said calling line to said means, primary and secondary switches for extending said called line under control of said means, and other switches under control of said means for extendin said calling line to said extension of said called line.

7. In a telephone system, a callin and a called line, means under control 0 said calling line for establishing a by-path to said called line, primary andsecondar nonnumerical switches for extending sai calling line to said means, primar and secondar non-numerical switches sald calledline under control of said means, and other switches under control of said means for extending said calling line to said extension of said called line.

8. The method of establishing connections -between telephone lines wherein automatic switchin devices controlled by directors are employe which comprises selecting one of a plurality of non-equivalent directors in the same central oflice, thereby routing a call, and subsequently excluding the means employed in making the said selection from the connection.

9. The method of establishing connections between telephone lines wherein automatic switching devices controlled by directors are employe which comprises selecting one of a p urality of non-equivalent directors in the same central oflice, thereby routing a call, setting the selected director under substation control and thereby controlling the es tablishment of a connection.

10. The method of establishing connections between telephone lines wherein machine switching devices under control of directors are employed which comprises selecting by digit impulses one of a lurality of non-e uivalent directors, there y routing a cal, and subse uently excluding the .means employed in ma ing the said selection fromthe connection.

11. The method of establishing connections between telephone lines wherein machine switching devices under control of directors are employed which comprises selecting by digit impulses one of a plurality of non-equivalent directors in the same central oflice, thereby routing a call, settin the selected director under substation contro and thereby controlling the establishment of a connection.

12. The method of routing a call through the extension of a telephone line wherein machine switching devices under control of or extending