US1563630A - Telephone system - Google Patents

Description

Dec. 1, 1925. 1,563,630

- E. E. HINRICHSEN TELEPHONE SYSTEM Filed Dec 29, 1920 5 Sheets-Sheet l Dec. 1

E. E. HINRICHSEN TELEPHONE SYSTEM Filed Dec; 29, 1920 5 Sheets-Sheet 2 /m en for: [dwaro f. H/hn'chsen.

50? YUM/my TELEPHONE SYSTEM Filed Dec: 29, 1920 5 Sheets-Sheet 3 bmt Dec. 1 1925. 1,563,630

' E. E. HINRICHSEN TELEPHONE SYSTEM Filed Dem 29, 1920 5 Sheets-Sheet 4 Dec. 1, 1925- E. E. HINRICHSEN TELEPHONE SYSTEM Filed Dec. 29, 1920 5 Sheets-Sheet 5 &R W

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FFIQE.

EDWARD E. HINRICHSEN, 0 NEW YORK, N. Y., ASSIGNOR TO WESTERN ELECTRIC COMPANY, INCORPORATED, OF NEW YQRK, N. Y., ,A. CORPORATION OF NEW YORK.

TELEPECONE SYSTEM.

Application filed December 29, 1920. 'Serial No. 433,751.

To all whom may concern.

Be it known that I, Enwann E. HINRIOH- Sun, a citizen of the United States, residing at New York, in the county of New York, State of New York, have invented certain new and useful Improvements in Telephone Systems, of which the following is a full, clear, concise, and exact description.

This application relates to telephone systems, and particularly to machine switching systems in which the connections are made by means of relay mechanisms.

A feature of the invention is a common pilot circuit by means of which the presentday line relay, with a single contact, may be employed instead of a multiple contact relay which has been required in the allrelay systems heretofore devised.

Another feature of the invention is a method of controlling the trunk allotter relays. Such relays operate under two different conditions; first, when a trunk is selected by a subscriber for an outgoing); call, and second when the trunk is taken on an incominn call or seized by the attendant subscriber. Under the first condition the operation of the relay is delayed by short circuiting its winding through its own back contacts until the connecting relays have functioned. Under the second condition, the operation is not delayed but is carried out as soon as the trunk is selected.

Another feature of the invention resides in the use of a new method in accomplishing the change-over from group selection to individual line selection which consists in a reversal of the method heretofore used, that is, by energizing a relay at the beginning of the primary selection and deenergizing it entirely during the secondary selection. By the use of such a method certain economies are effected.

Another feature of the invention consists in anovel scheme for numbering the terminals of a selecting switch. Broadly stated this method consists in connecting several lines to one terminal, the sum of whose (ligits equals be number of steps taken to reach the said terminal and differentiatingbctween the different lines connected thereto by approaching said terminal in different manners. For instance, the selection of the ninth terminal may serve to select a line nurn'b rcd l8. '1. 36 and so forth. in pick;

ing out any of the first three numbers, a group selection is made which is characterized by the first digit of the number and then an individual line selection is made which is characterized by the last digit of the numher.

The drawings consist of five sheets and six figures. The sixth figure represents the manner in which the five sheets are to be placed together in order to produce a full diagram of the circuits employed in carryinc; out this invention. Specifically, Figure 1 shows two groups of subscriber lines and the relay mechanism employed in connecting said lines to a trunk circuit; Figure 2 represents the relay mechanism employed in conmeeting the lines to a link circuit and a link circuit to the lines; Figure 3 represents a link circuit; Figure 4 represents the trunk circuit, and Figure 5 represents the code circuit.

The system embodied in the drawings provides for an exchange system of twenty-one lines capacity, the lines being divided intothree groups of seven lines each.

The numbers of the lines and the manner 7 in which they may be reached is set forth in the following table Effective position of arm Effective Group Tfige position of arm TU relays (in Fig. 1) and by providing the corresponding leads from the terminals traversed by brushes 221 and 219.

he tenth terminal traversed by brush 219 is reserved for central ofiice trunk calls and is not used in connection with any of the lines of the system. In the two groups of lines shown two lines of the first group, numbered 13 and 1st respectively and two lines of the third group, numbered 31 and 32 respectively are illustrated, the last being used as the attendant operators line.

In many respects this disclosure is similar to the disclosure embodied in the application of E. E. Hinrichsen, Serial No. 396,143, filed July 14, 1920, Patent 1,507.116, granted Sept. 2, 192a, so that a detailed description of all of the keys and functions thereof in the trunk circuit will not be given here.

It is believed that a clear understanding of the invention may be had from the following detailed description of the operation of setting up calls in various directions within this system.

Initiation of a call by a subscriber and the seizure 0 f a link circuit.

Let it be assumed that substation 113 initiates a call. Upon removal of the receiver from its switchhook the circuit for line relay 201 is closed, whereupon line relay 201 attracts its armature. A circuit is now closed for group relay 202 from ground, winding of relay 202, armature and front contact-of relay 201,.resistance 203, winding of-relay 2041 to battery and ground. Relay 204, attracts its armature and grounds the winding of relay 205, which is individual to the link circuit shown in Figure 3. Relay 205 attracts its armatures. A circuit is now closed from ground, armature and front contact of relay 202, outermost left hand armature and front contact of relay 205, winding of relay 206 to battery and ground. Relay 206 attracts its armatures and connects the calling line through its outermost set of four left hand armatures to the intermediate link circuit 207. At the same time a circuit is established from ground, winding of relay 202, armature and contact of relay 201, middle left-hand armature and -front contact of relay 205, winding of relay 208 to battery and ground. Relay 208 attracts its armatures and extends the inter mediate link circuit 207 to the link circuit of Figure 3.

The ,energization of .relay 204; besides causing the energization of relay 205, extends a ground from the armature and front contact of relay,.204c,.left-hai id armature and back contact of relay209, the back contact and-innermost right-hand armature of relay 209 ,conductor 210 and winding of relay 301 to battery and ground. Relay 301 through its right-hand armature places a ground on conductor 302 which is the test wire of the link circuit. Ground is extended over conductor 302 through the armature 211 of relay 208, armature 212 of relay 206 to the winding of the cut-off relay 213 and thence to battery and ground. Relay 213 attracts its armatures and causes the deenergization of line relay 201 whereupon the original circuits for the energization of relays 202, 20 1-, 200 and 208 are broken. As soon, however, as relays 206 and 208 have extended the ailing subscribefis line to the link circuit, the supervisory relay 303 is energized through the calling subscribers loop circuit, whereupon a ground is extended from the contact and left-hand armature of relay 303 to conductor 304. outermost left-hand armature and back contact of relay 21 1, righthand winding of relay 209 to battery and ground, and in parallel with the right-hand winding of relay 209 through front contact and innermost right-hand armature of 209 to the winding of relay 301. Relay 209 now looks itself in a circuit extending from ground, the front contact and outermost armature of relay 209, the conductor 215, front contact and left-hand armature of relay 301, conductor 305, left-hand winding of relay 209 to battery and ground. Thus it will be seen that the continued energization of relay 209 depends upon the energization of relay 301, and the continued energization of relay 301 depends upon the energization of 209.

Relays 303 and 301 having been energized are so held under the control of the calling subscriber, and relays 201, 202, 20 1 may become deenergizedby the energization of the cut-off relay 213, as hereinbefore pointed out.

'llhe energization of relay 209 also acts to extend the starting wire 216 to conductor 21.? which leads to a lett-hand armature of a relay similar to 209, which is individual to another link circuit similar to the link circuit illustrated in Figure Ellie ground placed on conductor 302 by the right-hand armature of relay 301 is extended through the outermost right-hand armature and back contact of relay 300 to conductor 30?, and thence through the innermost right-hand arnurture and front contact of relay 200, the winding of relay 206, to'battery and ground to hold this relay energized after its original energizing circuit has been broken. This ground is also extended from conductor 30? through the middle right-hand armature and front contact of rcla 200 to conductor and thence through the innermost righthand armature ant front contact relay winding of relay 208, to battery and gro nd to hold this relay energized after its original.

energizing circuit has been broken.

'il'he ground placed on conductor 302 by the right-hand armature of relay 301 is also extended through the left-hand armature and back contact of relay 308, the normal contacts of the right-hand armature of relay 309 to conductor 310, thence through the arm 219 and its normal contact to conductor 220, from whence it is extended to the winding of relay 009, to battery and ground, causing the energization of relay 309. This transfers the ground on conductor 310 to conductor 311, whereupon it is further extended through the arm 221 and its normal contact to conductor 220 to maintain the relay 309 energized.

The ground on conductor 305 is extended through the outermost left hand armature and back contact of relay 306 to the conductor 312 and thence to one terminal of relay 313. This relay, however, is short-circuited by the ground placed on the other winding through the front contact and right-hand armature of relay 303, so that 313 does not become energized at this time.

Thus the line relay 201 originally becoming energized causes the energizaion of the group relay 202 and the pilot relay -41. These two relays cause the encrgization of relay 205 and consequent energization of relays 206 and 208 to extend the calling subscribers line to the link circuit. The super visory relay 303 and the holding relay 301 now become energized and they establish a holding circuit for relays 206 and 208, a circuit for advance relay. 209, cut-oil relay 213. The line relay, the group relay and pilot relay beconie deenergized, leaving the connection in a stable condition, wherein the cutofl' relay 213, relays 206 and 208, supervisory relay 303, the holding relay 301 and the advance relay 209 are energized. Relay 309 is energized and locked in position through the movement of its own armatures. The connection is now in condition for the receipt of impulses for extending the link circuit to a called line.

Estcrblisiunent 0 f a. connection. to (my called Zine wit/m2 the private branch 0 f can change.

Let it be assumed that a call is to be established to substation 131 designated by the digits 3 and 1. The calling subscriber at substation 113 will manipulate his sender to interrupt his line three times in quick succession. These three interruptions will be transmitted to relays 301 and 303 in the form of three interruptions of their circuits, but relay 301 being slow to release will not be affected thereby. The relay 313, however, will affected since it is a quick relay. Each deenergization of the line relay removes the short-circuit from around r) g) the winding of relay 31.3 for a correspond ingly short intervaland relay 313 will attract its armatures three times in quick succession. Upon the first movement of its armatures, a circuit will be closed from ground, the inner left-hand armature of relay 313, conductor 314:, winding'of stepping magnet 222, to battery and ground, which causes the energization of the stepping magnet and the consequent movement of the switch arms 219 and 221 to their first posi tions. Through the outermost left-hand armature of relay 313, the slow to release relay 303 is energized. Relay 308 removes ground from conductor 311 and opens the original energizing circuit of relay 309, but relay 309 being slow to release holds its armatures attracted until the armature of relay 308 has reached its front contact, whereupon relay 309 becomes locked to the ground 011 conductor Relay 308 being slow to release does not respond to the three separate impulses, transmitted by relay 313, but the stepping, magnet does respond and causes the arms 219 and 221 to step on to their third contacts. Shortly after this series of impulses has ceased, relay 308 becomes deenergized and the ground on conductor 302 is connected through the left-hand armature and back contact of relay 308, the alternate contacts of the right-hand armature of relay 309, conductor 311, group switch arm 221 and its third contact, winding of relay 223 to battery and ground. Shortly after the deenergization of relay 308, relay 309 becomes deenergized. 1%. locking circuit for relay is now established from the ground on conductor 302 through the inner right-hand armature and front contact of relay 223.

The calling subscriber now manipulates his sender to send a single impulse. This causes the deenergization for a brief period of relay 303 and the consequent euci'gization of relay 313. The energization of relay 313 results in the energization of relay 303 and the stepping magnet 222. Stepping magnet moves the switch arms 219 and 221 to their fourth positions. Relay 309 being deenergized at this time, a circuit is established from ground conductor 302 to the left-hand armature and front contact of re lay 308, left-hand arn'iature and back contact of relay 309, winding 315 to battery and ground. Relay 315 prepares the circuit for test for the busy or idle condition of the called line. Shortly after this impulse, relay 308 becomes deenergizcd, whereupon a circuit is established from ground conductor 302, armature and back contact of relay 308, the normal contacts of the right-hand armature of relay 309, conductor 310, switch arm 219 and its fourth position contact, winding of relay 22a to battery and ground. Relay 224.- becomes energized and. locks it self to the ground from conductor 302 Called subscriber busy.

Let it be assumed that line 131 is at this time busy, and ground will therefore be found on the third conductor connected to the cut-off relay 226. This ground will be extended through the outermost left-hand armature and front contact of relay 223, the outermost left-hand armature and front contact of relay 224, conductor 22?, innermost left-hand armature and front contactof relay 315, the normal contacts of the innermost left-hand armature of relay 300, left-hand winding of relay 306 to battery and ground. Relay 300 becomes energized in this circuit and locks itself throu 'h the alternate contacts and innermost leit-hand armature of relay 306 to ground on conductor Through its innermost right-hand armature and front contact, the relay 000 extends a ground through the outern'iost left-hand armature and front contact of relay 315 to the right-hand winding of relay 316 causing the energization of relay 316. A busy tone is transmitted from the source of busy tone 317, back contact and outermost righthand armature of relay 318, condenser 319, right-hand winding of relay 316 to battery and ground. Through induction, busy tone is transmitted through the condensers 320 and 321 to the calling subscribers line. It .ill be noted that the busy tone will be transmitted to the calling subscriber immediately that he has seized the link circuit of Fig. 3 and if he recognizes it before he begins to dial he will take it as a dial tone. If it continues after he has dialed he will take it as a busy tone and hang up his receiver. If the called line is idle, as will be shown hereinafter, this tone will be cut off by the energization of relay 318 immediately after he has dialed. The calling subscriber will now replace his receiver on his switchhook and the relay 303 will become deenerglZGtl. Ground being remover from conductor 3011-, after a short interval, the ri lit-hand winding of relay 209 will become deenergized and relay 301 will be released. llclay 301 besides holding the ground on conductor 302 also functions to hold the switch arms 219, and 221 in their advanced positions and when relay 301 becomes deenergixed, the switch arms 219 and 221 will be returned to normal. The deenergization of relay 301 also causes the removal of ground from conductor 302, whereupon all relays tied to this conductor will become deenergized and the connection returned to normal.

Called subscriber- 2'(ll@ commotion successfully established.

Let it be assumed on the other hand that the called subscribers line 131 is found idle. Absence of ground on the third conductor leading to relay 220 prevents the operation of relay 306 at this time, therefore, when relay 308 becomzs deenergized and moves its armature to its back contact, opening the energizing circuit of relay 315, this relay becomes deenergized. Conductor 227 is new extended through the innermost left-hand armature of the back contact of relay 315 to conductor and from thence through the right-hand winding of relay 300 to ground. Since the other end of conductor 22? was connected to a winding of a cut-off relay 226 from thence to battery and ground, these two relays and 306 will become energized in series. The energization of relay 30G establishes a circuit from ground, the front con armature o lay 300, the outermost lefthand armature and back contact of relay 315, win ling of relay 318 to battery and ground. Relay 318 by attracting its lefthand armatures causes ringing current to be applied to the called line. By moving its right-hand armatures, relay 313 extends the third conductor 227 into connection with conductor 302, so that a direct ground connection will be placed upon the third conductor leading to cut-off relay 220, and the right-hand winding of relay 306 will become short-eircuited. Belay 300 has, however, in the meantime locked itself to the ground on conductor 302 through its innermost left hand armature and alternate contact leading to its left-hand winding. Through the outermost right-hand armature and front contact, relay 318 provides a path of high impedance through the condenser 31$) for the transmission of ringing tone to the calling subscriber.

Ringing current is transmitted from a source of ringing current 323, the left-hand winding of ringing relay 32 the back contact and innermost left-hand arniuiture of relay 32 i, the front contact and innermost left-hand armature of relay 313 through the contacts of relay and 223, the bell at the subscribers station 131, the contacts of relays 223 and the outermost left hand armature of front contact of relay 318, the outermost left-hand armature and back contact of relay to ground. Current flowing in this circuit is insufllcient to cause the encrgization of relay 324: until the subscriber at station 131 removes his receiver from his switclnhook. lVhen the subscriber responds, relay 324; becomes energized and locks up to the ground of corn *ct and innermost right-hand ductor 302 through its innermost right-hand armature and front contact, right-hand winding to battery and ground, and by the movement of its left-hand armatures cuts off the ringing current from the called subscribers line. The called subscriber is supplied with battery current for talking purposes through the windings of supervisory relay 316.

The connection is in a stable condition and conversation may proceed.

At the end of the conversation, the calling subscriber replaces his receiver on its hook whereupon relay 303 will become deenergized. causing the return to normal of all relays energized in this connection, as hereinbefore described.

Restricted seroz'ce subscriber attempts to set up a trunk connection.

Substation 119 has been shown as connected for restricted service, that is, as a station from which no trunk calls are allowed. Such service is rendered possible by disconnecting the ground connection from the fourth wire; in this case conductor 223. It will be noticed, that the ground provided for connection to conductor 228 is not connected, as is the ground connected to conductor 229. The function of this will appear hereinafter.

The subscriber at station 119 initiates a call as hereinbefore described in connection with station 113, and is connected to the link circuit of Figure 3. lVhen the subscriber at station 119 wishes to call the central office, he dials the single digit 0. This results 111 the sending of ten impulses which will set the brush arms 219 and 221 on their tenth contacts, but the switch arm 221 not having rested upon any of its associated group of contacts will have no effect on the apparatus upon the deenergization of relay 308.- Shortly after the deenergization of this relay, relay 309 retracts its armature, whereupon a circuit is established from ground on conductor 302, armature and back contact of relay 308, normal contact of the right-hand armature of relay 309, conductor 310, switch arm 219, its tenth contact, conductor 230, winding of relay 214, Winding of relay 215 to battery and ground. Relays 214 and 215 are energized in series in this circuit. Relay 215 extends the ground from conductor 302 through its front contact and right-hand armature to the winding of relay 214, thus locking relays 214 and 215 to conductor 302. Ground on conductor 304 is now extended through the outermost lefthand armature and front contact of relay 214, conductor 235, left-hand armature and back contact of relay 101 and winding of relay 102 to battery and ground, in parallel with relay 102 through the outermost righthand armature and back contact of relay 101, winding of relay 401 to battery and ground. Relays 101 and 401 are energized in this circuit and attract their armatures.

Station 119 being connected for restricted service ground on conductor 228 is absent and therefore no ground will be found in the right-hand armatures of relay 214. Hence no circuit for the trunk connecting relays will be established, and the connection from the test relay 306 through the innermost lefthand armature of relay 214 and right-hand armature and front contact of relay 102 will remain open. Upon the energization of relay 214, relay 301 becomes deenergized, whereupon the relays locked to conductor 302 become deenergized. The line relay 201 becomes deenergized, and the calling line seizes the next idle link circuit. Thus the attempt of a subscriber, at a restricted service station to call the central office, will fail. Since a tone is continuously transmitted to the calling subscriber from the link circuit until an idle line is encountered, which tone serves a dial tone before dialling and as a busy tone after dialling it will be apparent in the present instance that as soon as the' calling subscriber has been switched to another link circuit in the manner described he will recognize the tone as a busy tone and therefore abandon any further attempt to establish a connection to a central ofiice trunk.

Establishment of (a central office call.

Suppose, on the other hand, the station 113, which is connected for full service, had initiated a call for the central office, then after relay 214 has been energized a circuit will be established from ground, conductor 229, the outermost left-hand armature and front contact of relay 206, the outermost left-hand armature and front contact of relay 208, the outermost right-hand armature and front contact of relay 214, conductor 231, front contact and outermost right-hand armature of relay 206, conductor 232, outermost left-hand armature and front contact of relay 102, winding of relay 103, to battery and ground, resulting in the energization of relay 103. A parallel circuit will also be established from the ground on the innermost right-hand armature and front contact of relay 214, conductor 233, front contact and outer-most right-handarmature of relay 208, conductor 234, armature and front contact 104 of relay 102, winding of relay 105 to battery and ground, resulting in the energization of relay 105. 2

Relay 401, having become energized, ground is placed on conductor 402, resulting in the lighting of busy lamp 403, and resulting also in the extension of ground through the contacts 404 of key 405 to conductor 406, thence through the innermost right-hand armature and front contact of Cir 408, innermost ri 'ht-hand armature and back contact of relay 400, outermost lefthand armature and back contact of relay 410, middle armature and front contact of relay 105, armature 106 of relay 103, through the loop of station 113, armature 107 of relay 103 and its front contact, innermost lefthand ari'nature of relay 105, back contact and innermostleft-hand armature of relay 410, back contact and outermost right-hand armature of relay 409, normal contact of the innermost ieft-hand armature 408, righthand winding of relay 407 to ground. 13elay 407 becomes energized in this circuit and through the movement of its armature places ground on conductor 411.

Relay 407 also causes the energization of relay 414 in a circuit extending from ground, front contact and right-hand armature of relay 407, normal contacts of the innermost left-hand armature of relay 414, contacts 415 of key 416, winding of relay 414 to battery and ground. Relay 414 locks up in a circuit from ground, front contact and right-hand armature of relay 401, alternate contacts of the innermost left-hand armature of relay 414 and thence over the circuit just described.

Shortly after the establishment of these connections, and through the movement of the outermost left-hand armature of relay 214, relay 301 becomes deenergized, thereby removing the ground from conductor 302 and restoring the link circuit to normal. The cut-off relay is now held in a circuit from ground, battery, winding of relay 213, outermost left-hand armature and front contact of relay 103, outermost left-hand armature and front Contact of relay 105, conductor 412, outermost left-hand amature and back contact of relay 413, normal contacts ofv the outermost right-hand armature of relay 410, conductor 402, left-hand armature, front contact of relay 401 to ground.

A circuit is now established for relay 306 from ground, right-hand winding of relay 306, conductor 322, innermost left-hand armature and front contact of relay 214-, conductor 236, right-hand armature and front contact of relay 102, outermost right-hand a mature and front contact of relay 103, conductor 108, front contact and outermost right-hand armature of relay 105, resistance 109 to battery and ground. Relay 306 becomes energized and through the movement of its outermost right-hand armature re moves ground from conductor 307, thus causing the deenergization of relays 200 and 208 and completing the restoration to normal of the seized link circuit.

As the holding relay 301 becomes deenergized, the switch arms 219 and 221 are returned to normal, whereupon the ground is removed from conductor 230 and ground having been removed from conductor 302, relay 214 becomes deenergized, whereupon ground is removed from conductor 235. Relay 101 has, up to this point, been shortcircuited. The ground now being removed from its right-hand armature, it becomes energized in a circuit from ground on conductor 402, the winding of relay 101, resistance 107 to battery and ground. Helay 102 becomes deenergized. Relay 401 remains energized in its circuit from ground, battery, winding of relay 401, outermost right-hand armature and front contact of relay 101, conductor 411, right-hand armature and front contact of relay 407 to ground. Conductor 235 is extended to conductor 140, and thence to a left-hand armature of a relay similar to 101 which is individual to another trunk crcuit, so that the next call for a trunk will be switched to the next idle trunk line.

Upon the energization of relay 407, a circuit is closed from ground, back contact and innermost left-hand armature from relay 500, conductor 424, lef-hand armature and front contact of relay 407, back contact and intermediate left-hand armature of relay 429, tip conductor of the trunk, contacts 430 of key 431, contacts 432 of key 416, contacts 433 of key 434, back contact and outer left-hand armature of relay 550, winding of relay 551 'to battery and ground. Relay 551 attracts its armature and closes the starting circuit, if this trunk leads to an automatic office, or closes a circuit for the lighting of a line lamp if this trunk leads to a manual office. In the first case this trunk will be extended to a selector switch through the action of a non-numerical switch, and in the second case this trunk will be connectedto by an operators cord circuit. In either case relay 550 will become energized to cut-01f relay 551 and ground will be placed on the tip conductor and grounded battery on the ring conductor. A circuit will then be established from ground on the tip conductor, contacts of key 434, contacts 435 of key 431, right-hand and left-hand windings of relays 423 in series, back contact and inner right-hand armature of relay 418, contacts 436 of key 434 to battery on the ring conductor of the trunk. Relay 428 is energized in this'circuit, and through the movement of its armature places a ground on the winding of relay 10 which becomes energized. Relay 410 causes the energizai'ion of relay 500 in a circuit ineluding ground from contact and outer right-hand armature of relay 419, conductor 422, left-hand armature and back contact of relay 514, winding of relay 500 to battery and ground. Relay 500 by moving its armatures, places a shunt across the trunk in place of the ground on the tip, this shunt extending from the tip conductor, intermediate left hand armature of relay 429 and its back contact, front contact and left hand armatures of relay 407, conductor 424, in ner left hand armature and front contact of relay 500, conductor 421, ring side: of the trunk.

Relay 41.? now becomes energized in a circuit including the ground on the tip conductor at the central office contacts 433 of key 434, contacts 432 of key 416, contacts 430 of key 431 over the shunt circuit just traced, contacts 4"? of key 431, contacts of hey 416, winding of relay 417, contacts 436 of key 434 to battery of the ring conductor of the trunk at the central oflice. The energization of relay 417 results in the energization of-relay 418 which places the resistance 42'? around the winding of relay 417 and through the movement of its inner right hand armature cuts off relay 428. Relay 418 maintains relay 419 energized.

It will be noted that the subscriber station 113 now has direct control over relay 407 and through the agency of relay 407 has control over any apparatus at the central office through which battery current is fed to the trunk line.

Vi e will assume that the central office connection is a selector switch of some form which is responsive to interruptions in the line circuit, therefore if the subscriber of station 113 manipulates his dial the impulses created thereat will be transmitted to the central office selector through the movement of the left hand armature of relay 407.

It will be noted that relay 407 also has control over the switch shown in Figure 5. A circuit is now' established from ground, left hand winding of relay 502, the front contact of the outer left hand armature of relay 500, conductor 411 to ground at the right hand armature and front contact 'of relay 407. Relay 502 is normally short-cir cuited but when relay 407 retracts its ar1natures, the left hand winding of relay 502 will be included in a circuit from conductor 411, resistance 501 to battery and ground and in parallel therewith winding of relay 401 to battery and ground. Upon the establishment of such a connection relay 502 will become energized and will attract its armatures. Through its left hand armature it will close a circuit from ground through the windin of relay 503 to battery and ground. Relay 503 will become energized in this circuit. Through its left hand armature relay 502 will also place a ground on the winding of a stepping magnet 504, which is furthe connected through the resistance '505 to grounded battery. Relay 502 locks up in a circuit including grounded battery its right hand winding, front contact and right hand armature of relay 502, armature and back contact of magnet 504, front contact and left hand armature of relay 502 to ground.

Thus the energizing circuit for magnet 504 a will be maintained until it has completed its stroke at which time it will open the looking circuit of relay 502. By this time, relay 40'? will again have attracted its armatures so that-the left hand winding of relay 502 become short-circuited and this relay becomes deenergized. Magnet 504 will therefore respond to each impulse which vibrates the armatures of relay 407. The relay 503 will respond to the series of impulsesas a whole and after relay 502 has become deenergized for a sufficient period of time, it will become deenergized.

When employing the code circuit shown in Fig. 5 and it is desired that the attendant have supervision over certain calls, the contacts of the code switchbanl: over which. brushes 508 and 509 pass and which correspond to certain digits of such calls are connected'tothe con ductor 517, otherwise these contacts are not so connected. The contacts or terminals associated with each of the brushes 508 to 511 inclusive, are divided into two groups, separated by a vertical intermediate row of contacts including contact 520. As shown in Fig. 5, it will thus be seen that each of the groups contain three contacts or terminals, the remaining terminals of the groups being omitted for simplicity and economy of space.

In the operation of the code switch, through connections between conductors 517 and 519 to the terminals of the switch traversed by brushes 508, 509 and 511, such switch is caused to continue its operation until the complete code has been transmitted after which circuits are closed to light the line lamp associated with the trunk employed thus calling in the operator. The connection through the central oifice is not disturbed except at the instance of the operator. In case a code is transmitted which does not require the operator to be brought in, as when the brushes of the code switch encounter terminals to which no connection to conductors 517 or 519 is made, then the code switch ceases its operation and a connection between the calling subscribers line and the central office trunk is established so that the impulses are not then repeated but are transmitted directly. As an example of the operation of the code itch a four digit code connection will now be described.

in response to the series of impulses corresponding to the first digit dialed, the code switch stepped to engage the brush 508' gaged thereby, conductor 517, and from thence to ground on the conductor 422 through the left and arn'iature and alternate contact of relay 003, this circuit being established before relay 503 releases. at the termii'iation of the series of impulses. When relay 503 releases, a locking circuit for relay 512 is established from grounded battery, through the winding, front contact and outer right-hand armature of said relay, and the alternate contact of relay 503 to ground on conductor Brush 506 is now engaged with segment 521 and when relay 503 releases, ground is extended throu h its right-hand armature, brush 500, segm it 521, winding of relay 513 to grounded battery, this relay being adjusted for slow operation and release. The closure of the front contact of relay 513 establishes a self-interrupting circuit for motor magnet 50% extending from grounded battery, through the resistance 505, armature, contact and armature of magnet 50%, right-hand armature and back contact of relay 502, front contact and armature of relay 513 and from thence to the contact of relay 503 over the energizing circuit for relay 513. The motor magnet then operates to Step the switch until the brush 506 engages contact 520, whereupon the operating circuit for said motor magnet will be opened and the switch will come to rest.

The second series of impulses is now transmitted and relay 503 again operates in response to the first energizat-ion of relay 502 to open the locking circuit for relay 2 which then releases. Motor magnet 501 is operated in response to the energization of stepping relay 502 and the brushes of the switch are then stepped over the contacts of the SGCOlK group. Brush 506 is now in e: k moment with segment 522 and brush 5t?) uith a contact in the second group associated therewith. If this latter contact is connected to the left-hand armature and alteii ate contact of relay 503 through conductor 517, relay 512 again operates and locks up in the same manner as previously described and relay 513 again operates to close the previously mentioned self-interrupting circuit for motor magnet 5041 whereupon the switch is stepped to its normal position. Upon reaching this position, the right-hand armature of relay 503 is connected through the brush 506 and its normal contact, the inner left-hand armature and relay 512 from brush 508 to the brush 509 through the outer right-hand armature and front contact of relay 515.

The series of impulses corresponding to the third digit of the called number is now transmitted and the code switch again operates to engage its brushes with the associated contacts of the first group. With relay 515 energized and locked up, should brush 509 engage a contact in the first group connected to the conductor 517, relay 512 will then energize through the outer righthand armature and front contact of relay 515 and will lock up when relay 503 releases at the termination of the series of impulses. with segment 521, relay 513 operates as before to cause motor magnet 50% to step the brushes of the switch to the intermediate vertical row of contacts including'contact 520.

The fourth digit of the desired number is now dialed to again step the brushes of the code switch over the second group of the associated contacts. The contacts of the second group over which brush 509 passes and which correspond to certain digits of numbers requiring supervision are connected to the conductor 517. Such contacts as justmentioned in the second group associated with brush 511 are connected to conductor 519 which extends to the right-hand winding of relay 51 1. Therefore, should brushes 509 and 511 engage such contacts as mentioned above, when the switch is brought to rest at the termination of the fourth set of impulses, relay 512 again energizes and locks up and upon the release of relay 503, relay 513 again energizes. This relay being slow to operate, a circuit is closed before said-relay can open its back contact, which circuit extends from ground, through the right-hand armature and contact of relay 503, brush 506, segment 522, the armature and back contact of relay 513, the inner right-hand armatures and front contacts of relays 512 and 515, brush 511 and the contact engaged thereby, conductor 519, and the right-hand winding of relay 511- to grounded battery. Relay 51% energizes in this circuit and locks up through its righthandwinding, innermost right-hand armature and alternate contact to ground at the conductor 22a The cnergization of relay 51 1 opens the energizing circuit for relay 500 and the locking circuit for relay 515 With brush 506, in engagement and these relays thereupon release. Relay 512 being still energized and locked up, ground 011 conductor 422 is extended through the normal contact of relay 503, which releases at the termination of the series of impulses, through the outer right-hand armature and front contact of relay 512, front contact and middle right-hand armature of relay 514, conductor 425, back contact and outermost left-hand armature of relay 438, and the line lamp 439 to grounded battery. The line lamp is lighted in this circuit to inform the attendant that a call requires supervision.

When relay 513 energized upon the release of relay 503, motor magnet 504 is again operated to return the switch to its normal position. The energization of relay 514 connects conductors 423 and.422 through the left-hand armature and front contact of said relay and a circuit is thereby established for relay 408 extending from grounded battery, through the winding of said relay the outer left-hand armature and contact of relay 414, conductor 423, front contact and left-hand armature of relay 514, conductor 422, front contact and outer right hand armature of relay 419. The energization of relay 408 extends the calling line over the trunk to the central office. The release of relay 500, upon the energization of relay 514, opens the bridge through which the impulses were repeated to the central oflice and again grounds conductor 424, the relay 500 being slow to release holds this bridge closed until the line is extended by the operation of relay 408. In this manner a connection which requires the supervision of the operator is established. Upon the operation of relay 408 the calling subscribers line is directly connected to the central o flice trunk so that other trains of impulses may be directly transmitted without being repeated at the left hand contact of relay 407.

If, at any stage in the selection of a called line, the code switch stops with its brushes 508 and 509 in engagei'nent withcontacts not connected to conductor 517, relay 512 will not energize and the release of relay 503 at the tern'iination of the series of impulses, grounds the brush 507 through the outer right-hand armature and back contact of relay 512 with the result that this ground is extended over conductor 519 to grounded battery through the right-hand winding of relay 514. The latter relay energizes with the same result as previously described and prevents any further operation of the code circuit. Under the circumstances justreferred to, if the contact not connected to conductor 517 is located in the first group, the switch will again operate as before upon the energization of relay 513 to step brush 506 into engagement with the terminal 520. In asniuch as relay 512 is not operated, relay 513 will continue to remain energized through the back contact and outer right hand armature of relay 512, contact 520 and the brush 506 to ground at the righthand armature of relay 503 and motor magnet 504 will therefore continue to step the brushes of the switch to their normal positions.

When relay 408 energizes to extend the calling line through to the central office, the supervisory relay 417 is included in the line circuit. The circuit for relay 407 is permanently opened upon the energization ofrelay 408 but relay 401 remains energized under the control of relay 408. Thus it will be seen that when a code is dialled which does not require the service of the operator, the calling subscriberS'line is directly connected to the central office trunk and the code switch is returned to normal. Returning now to the previously described case where the attention of the operatorwas attracted by the lighting of the line lamp'439, the manner in which such operator supervises the connection will now be described.

When the attendant operates listening key 440, in response to the lighting of the line lamp 439, relay 429 energizes and causes the energization of relay 438 over a circuit from ground, outer left hand armature and front contact of relay 417, inner right hand armature and front contact of relay 414, outer left hand armature and contact of relay 429, left hand winding of relay 438 to grounded battery. Relay 438 looks up and closes the ener gizing circuits for relay 441 to open the energizing circuit of the guard lamp 442. The energization of relay 438 opens the energizing circuit for the line lamp 439 which is then extinguished. The closure of the middle right-hand contact of listening key 440 also extends ground through the left-hand winding of relay 514, over conductor 420 to provideanadditional holding circuit for this relay.

WVhen the trunk is released at the end of the call, restoration occurs and the release of relay 419 opens the locking circuits for relays 512 and 514,, the former relay having remained energized after the last series of impulses which were transmitted in extending the call. With the release of relays 512 and 514, the code circuit is then in its normal position and ready to be operated upon the extension central ofiice.

To arrange the circuit to respond to three instead of four digit numbers, the necessary contacts in the first group associatedwith brush 511 are connected to conductor 519 so that relay 514 will operate through the front contacts and inner right-hand armatures of relays 515 and 512 before relay 513 has time to open its back. contact. The

switch. then steps with the brushes in engageof another call to the ment with the intermediate vertical row of contacts and remains in this position until the trunk is released and relay L19 deenergized, whereupon the locking circuit for relay 512 will be opened and this relay rcleases. Relay 513 is then operated through the back contact and outer left-hand arn1a ture of relay 512 with the result that the switch is stepped to normal as before.

hen arranged to operate in conjunction with numbers containing both two and three digits, relay 516 is provided and is adapted to be connected, through brush 510, to contacts in the first group corresponding to the first digit of two digit numbers to which the circuit is to respond. Therefore, upon the transmission of the impulses for the first digit, relay 512 operates through brush 508 and the contact engaged thereby which is connected to conductor 51?. Re lay 512 looks up as before and upon the release of relay 508 a circuit is moi'nentarily closed before relay 513 can energize and open its back contact, said circuit extending from grounded battery, through the winding of relay 516, brush 510 and contact engaged thereby which corresponds to the contact from the first group associated with brush 508, conduct-or 518, back contact and armature of relay 513, segment 521. brush 506, and the righthand armature and contact of relay 503 to ground. Relay 515 cuergizes and locks up through its contact and right-hand armature and the alternate contact of relay 51% to ground at the conductor 422. Upon the energization of relay 513, the switch is stepped, as before. to engage the brush 506 with the terminal 520 and the ground on said brush from relay 503 isthen extended through the outer left-hand armature and front contact of relay 512. lefthand, armature and contact of relay 516. back contact and oute mostright-hand armature of relay 514:, and the winding of relay 515 to grounded battery. Relay 515 energizes and locks up through its front contact and left-hand armature to ground on theconductor 4-22. Thesecond digit of the two digit number is then dialed and the proper contact for the second digit. located in'the second group associated with brush 511is connected toeonductor 519. The circuit then functions in the same manner as described in connection with thefourt-h digit of a four digit number. Should a three digit number be dialed, no contact in the second .groupassociated with the brush 511 is connected with conductor 510 when the second series of impulses is sent. Relay 514'. will, therefore, not energize at the end of-its series of impulses and the switch will bestepped to normal. The proper contact in the first group associated with the l: rush 511- is connected to conductor 519, and the switch then operates-as previously described in connection withthree digit numbers.

The code switch may be made to operate to light the line lamp 439 by the transmission of a single series of impulses. In this case, the proper contact in the first group associated with brush 508 is connected to conductor 517 and the corresponding con tact in the first group associated with brush 510 is connected to the left-hand winding of relay 514-. Vhen relay 512 operates and locks up as before, ground is momentarily extended until relay 513 operates upon the release of relay 503, from the right hand armature of this relay through the brush 506, segment 521, armature and back contact of relay 513, conductor 518, contact engaged by brush 510 and from thence through the left-hand winding of relay 51d to grounded battery. Relay 514 then operates as before to light the line lamp 439. The switch is then stepped to engage the brushes thereof with the intermediate vertical row of contacts, where the same stops until the trunk is released and relay silt) deenergized. The locking circuit of relay 512 is then opened and the latter relay releases where upon relay 513 is operated through the back contact and outer left-hand arn'iature of relay 512 to cause the switch to he stepped to normal in the same manner as previously described.

Incoming call from central 077i(.:c to station Let it be assumed that now the trunk leads to a manual exchange and that the tip. ring and sleeve conductors of the trunk terminate in corresponding contacts of a multiple jack. When the trunk is so connected to the manual exchange, the code cir ouit shown, in Figure 5 is unnecessary and the connections shown as leading from Figure -.lto 5 will be as follows: Conductor 4-2-1- will be permanently grounded and conductors 422 and 123 will be connected together.

The operator at the central oflice will in sert a plug of an ordinary cord circuit into the jack leading to the trunk, whereupon the tip conductor will be grounded, the ring conductor will be connected to battery and the sleeve conductor will be grounded to operate the cut-off relay 550 to remove the line relay 551 from control of the line. Thereupon a: circuit will be established from ground on the tip conductor, contacts 433 of key 484:, contacts 435 of I'll, and left hand windings of line relay 1 in series, back contact and inner right hand armature of relay 418,, contacts L35 of lrey 434-, ring conductor of the trunk line to grounded battery. Relay 128 is energized. in this circuit and through the movement of its armature causes the energization of relay'tltl. Relay 4'19 places ground on C0llductor 402 causing the lighting of the busy lamp 403 and the energization of relay 101.

The operator at the central ofiice then projects ringing current on the trunk which finds a path from the tip conductor through contacts 433 of key 434, contacts 432 of key 416, contacts 430 of key 431, the back contact and outer right-hand armature of relay 408, condenser 445, right-hand winding of relay 446, contact 436 of key 434 to the ring conductor of the trunk line. Relay 446 responds to current in this circuit and attracts its arinatures, whereupon a locking circuit is established for relay 446 from grounded battery, the left-hand winding of relay 446, front contact and inner left-hand armature thereof, back contact and innermost left-hand armature of relay 429, normal contacts of middle left-hand armature of relay 438, conductor 402 to ground. This ground connection is also extended through the outer left-hand armature and front contact of relay 446, line lamp 439 to battery and ground causing the lighting ofthe line lamp.

The attendant subscriber at station 447 answers the incoming call by actuating her listening key 440 thereby bridging her telephone set across the tip and ring conductors of the trunk line. Thereupon a circuit is established from ground on the tip conductor, contacts 433 oft-key 434, contacts 4320f key 410, contacts 448 of key 440, telephone set 447, contacts 449 of'key 440, contacts 438 of key 416, winding of relay 417, contacts 436 of key 434 to grounded battery on the ring conductor of the trunk. Supervisory relay 417 is energized in this circuit and through its inner left-hand armature it causes the energization of relay 418. Relay 418 bridges the resistance 427 across the winding of relay 417 and at the same time disconnects the line relay 428 from the trunk leaving a connection extending from the tip conductor through the right-hand winding 428, the three windings of impedance coil 450 in series, the right-hand armature and front contact of relay 429 to the ring conductor of the trunk. Relay 429 is energized in a circuit extending from ground, contacts 451 of key 440, contacts 452 of key 434, winding of relay 429. The energization of relay 418 maintains relay 419 energized since the line relay 428 now has such high re sistance included in series with these windings that it becomes deenergized. The energization of relay 429 also breaks the connection between ground and line lamp 439 and the left hand winding of relay 446, whereupon the line lamp 439 is extinguished and relay 446 becomes deenergized, The connection is now in a stable condition awaiting further manipulation of the apparatus by the attendant subscriber at station 447.

The attendant subscriber thereupon actuates key 416 which severs her talking set from the trunk but leaves a low resistance holding connect-ion. Relay 417 becomes deenergized resulting in the deenergization of relay 418. The circuit is then closed from the tip conductor of the trunk contacts of relay 431, the right-hand winding of relay 428, the right hand winding of impedance coil 450, the left hand armature and contact .of relay 418, the left hand winding of imcontact of key 473, conductor 456, contact 111 and through the winding of relay 112. Relay 112 becomes energized in this circuit and locks itself in a circuit including battery, its own winding, front contact and its inner righthand armature, conductor 406, contacts 404 of key 405, conductor 402 to ground and a third circuit is established from ground, left hand contacts of key 473, conductor 457, contacts 114 of relay 110, winding of relay 103 to-battery and ground. Relay 103 becomes energized in this circuit and is then locked in a circuit including battery and ground, its own winding, its front contacts left hand armature, conductor 406 and thence to ground over the path pre viously traced. A circuit is now established from ground, the outer right hand contacts of key 473, contacts 455 of key 416, the back contact and outer right hand armature of relay 444, the right hand winding of relay 413, the back contact and right hand armature of relay 414 to battery and ground. Relay 413 is energized in this circuit and the test wire of the called line is connected through the test contacts which are 0011- nected through contacts 115 of relay 103. the outer left hand armature and front contact of relay 112, conductor 412, outer left hand armature and front contact of rela 413, normal contacts of the inner left hand armature of relay 444, left hand winding of relay 444 to battery and ground. If the called line is busy, ground will be found on the test conductor of the called line, and relay 444 will become energized whereupon it if will lock up in a circuit including battery and ground, its left hand winding, alternate contacts of its inner left hand armature to contacs 458 of key 405, contacts 459 of key 460, conductor 402 to ground, Another circuit is established from grounded conductor 402, contacts 461 of key 405, outer right hand armature and front contact of relay 413, winding of relay 410, contacts 462 of key 460, inner right hand armature and front contact of relay 413, back contact and outer right hand armature of relay 414 to battery and ground. Relay 410 locks up in a circuit from ground on conductor 402, contacts 401 of key 405, inner right hand armature and frontcontact of relay 410, winding of relay 410, and thence over the circuit just described.

Busy tone is now connected to the attendant subscribers telephone from a source of busy tone 463, the front contact and outer left hand armature of relay 444, condenser 464, front contact and inner left hand armature of relay 410, right hand armature and back contact of relay 400, back contact and inner left hand arn'iature of relay 408, contacts 465 of key 416, contacts 448 of key 440, subscriber station 447, contacts 449 of key 440, contacts 466 of key 416, left hand windmg of relay 407 to battery and ground.

' The attendant subscriber recognizes the busy tone and restores key 416 to normal so that She may converse with the operator at the central office and notify her that the line is busy. Upon the restoration of key 416, supervisory relay 417 becomes energized and line relay 428 becomes deenergized as hereinbefore described. The operator at the central oilice may then break the connection by removing her plug from connection with the trunk line and the attendant subscriber at station 447 may restore her listening key 440 to normal, whereupon the supervisory relay 417 will become deenergized. Relay 428 will fall to energize and in a short time, relay 410 will retract its armatures whereby ground is removed from conductor 402 and the connection is entirely restored to normal.

If the called station 119 had roved to be idle, then battery would have been opposed to battery in the connection including the windings of'the cut-oif-relay individual to the-line 119 and the left-hand winding of relay 444. Relay 444 would have failed to energize so that when theattendant subscriber released key 473, relay 413 would become deenergized. Thereupon a circuit will be established from battery, the wind- 1 ing of cut-oif relay:individual to subscribefis line 119, conductor 412, theouter left-hand armature and back contact of relay 413, the alternate contacts of the outer right-hand armature of relay 410,the right-hand wind- 4 ing of relay 444to ground. Relay 444 becomes energized in this circuit and establishes a circuit from ground on conductor 402, inner right-hand armature and front contact of relay 444, back contactand inner right-hand iarznature ofrelay=413, winding of relay 409,

armature and back contact of relay 443, back contact and outer right-hand armature of comes deencrgized. It should be noted that upon the deenergization of relay 413 the .ircuit of relay 410 is opened but that before this latter relay retracts its armaturcs a circuit is momentarily established for relay 444, which circuit is thereafter immediately opened by the deenergization of relay 410, but relay 444 having attracted its armatures locks in a circuit from grounded battery, left hand winding of relay 444, alternate contacts of the inner left hand armature of relay 444 contacts 458 of key 405, contacts 459 of key 400 to grounded conductor 402. Ringing current is now con nected to the called line from. source of ringing current 400, left-hand winding of relay 443, front contact and inner righthand armature of relay 409, outer left-hand armature and back contact of relay 4410, middle left-hand armature of relay 112 and its front contact, front contact and armature 116 of relay 103 through the called substation 110, innermost left-hand armature of relay 103, innermost left-hand armature of relay 112. back contact and inner left hand armature of relay 410, outer right hand armature and front contact of relay 409 to ground. Current in this circuit is insul ticient to cause the energization of relay 44 3 until the subscriber at station 119 removes his receiver from its switchhook, whereupon a connection is established from battery, outer right hand armature and back contact of relay 414, right hand winding of relay 443, armature and front contact of relay 443, inner right hand armature and back contact of relay 413, front contact and inner right hand armature of relay 444 to ground on conductor 402, so that relay 443 becomes locked and relay 409 becomes short-circuited and deencrgizcd. The called subscriber now causes the energization of the line-relay 407, whereupon ground is placed on conductor 411, and thence through the front contact and outer right hand armature of relay 101 to winding of a relay 401. The called subscriber and the attendant subscriber may now converse and the attendant subscriber Will notify the called subscriber that a call is incoming from the trunk, whereupon the attendant subscriber restores keys 410 and 440 to normal. The restoration of key 416 establishes a circuit from grounded battery, Winding of relay 414, contacts 415 of key 416, normal contacts of the inner left hand armature of relay 414, right hand armature and front contact of relay 407 to ground. Relay 414 becomes energized in this circuit and is then looked in a circuit including the alternate contacts of its inner left hand armature and the right hand armature and front contact 401 to ground. Uponthe energization of relay 414, relay 408 becomes energized in a circuit leading from battery and ground, winding of relay 408, outer left hand armature and front contact of relay 414, conductor 423, now connected directly to conductor 422, outer right hand armature and front contact of relay 419 to ground. Relay 408 becomes energized and the connection between the central office trunk and the called subscriber is completed. The talking battery for the called subscriber is supplied from the central office and the supervisory relay 417 is energized in series with the calling substation. At the end of the conversation the called subscriber replaces his receiver on its switchhook thereby deenergizing the supervisory relay 417. This results in the deenergization of relay 418 and in a short time the deenergization of relay 419, whereupon the ground is removed from conductor 402 and the relay 408 becomes deenergized. Upon the retraction of its armatures, relay 408 removes ground from conductor 411 whereby the holding re lay 401 becomes deenergized and the coin nection is entirely restored to normal.

What is claimed is:

1. In a telephone system, a direction switch for controlling the establishment of connections to different lines, a pointer for said switch, and a plurality of points with which said pointer cooperates, each of said points being associated with a plurality of lines and means for causin the establishment of connections to di' erent lines by causing said pointer to approach said points in different manners.

2. In a telephone system, a direction switch for controlling the establishment of connections to different lines, a pointer for said switch, a point with which said pointer cooperates and means for causing the establishment of connections to different lines by causing said pointer to approach said point in different manners.

3. In a telephone system, a direction switch for pointing out the direction in which a connection is to be extended, a pointer for said switch, and a plurality of points with which said pointer cooperates, a plurality of telephone lines associated with each of said points, the designating number of each of said telephone lines being a number the sum of whose digits is equal to the designated number of said point.

4. In an all-relay telephone system, a plurality of telephone lines, a line relay associated with each of said lines, said relay being provided with a single armature and contact, a common pilot circuit responsive to said relays, and means whereby each of said relays controls a different circuit.

5. In a telephone system, a plurality of telephone lines, a plurality of trunk lines, a

relay associated with each of said trunk lines for determining the order of seizure of said trunk lines, relays for connecting said lines and said trunk lines, means responsive to a call from a line to a trunk line for delaying the operation of the trunk relay connecting means have been actuated, and.

means responsive to a connection from 'a trunk line to a line for immediately operating said trunk relay.

7. In a telephone system, aplurality of telephone lines, a plurality of trunk lines, a relay associated with each of said trunk lines for determining the order of seizure of said trunk lines, relays for connecting said lines and said trunk lines, and means responsive to a call from a line to a trunk line for shunting said trunk relay until said connecting relays have been actuated.

8. In a telephone system, a direction switch for pointing out the direction in which a connection is to be extended, a pointer for said switch, means for propelling said pointer in a plurality of consecutive stages each commensurate with a corresponding factor of the desired direction and means for altering the function of said pointer at each stage.

9. In a telephone system, a direction switch for pointing out the direction in which a connection is to be extended, a pointer for said switch comprising a plurality of brushes, means for propelling said pointer in a plurality of consecutive stages each commensurate with. a corresponding factor of the desired direction and means for rendering a different one of said brushes effective at each said stage.

10. In a telephone system, a direction switch for pointing out the direction in which a connection is to be extended, a pointer for said switch comprising a pair of brushes, means for propelling said pointer in two consecutive stages each commensurate with a corresponding factor of the desired direction, means for rendering one of said brushes effective during one stage and the other of said brushes effective during the second stage.

11. In a telephone system, a direction switch for pointing out the direction in which a connection is to be extended, a

pointer for said switch comprising a pair of brushes, means for propelling said pointer in two consecutive stages each commensurate With a corresponding factor of the desired direction means for rendering one of for transmitting said tone over the calling end of said link whereby it may be used as a dial tone before said link is extended and as a busy tone after an unsuccessful attempt to extend said link, and means for discon-- necting said source of tone after a successful attempt to extend said link.

In Witness whereof, I hereunto subscribe my name this 18th day of December, A. D. 1920.

EDYVARD E. HINRICHSEN.

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