US1629533A - Automatic telephone system - Google Patents

Description

May 1927' R. s. RICHARDSON AUTOMATIC TELEPHONE SYSTBI Original Filed Nov. 23. 1920 3 Sheets-Sheet 1 1,62 533 y 24,1927 ga. RICHARDSON 9 AUTOMATI C TELEPHONE SYSTEM Original Filed Nov. 23. 1920 3 shms shm 2 I Racine EEmhardsun May. 24, 1927.

R. G. RICHARDSON AUTOMATIC TELEPHONE SYSTEM Original Piled wov. 23, 1920 3 sh ,.s -3

Ill)

Patented May 24, 1

nurrsn stares PATENT orFicE.

RODNEY G. RICHARDSON, OF

CHICAGO, ILLINOIS, ASSIGNOR, BY MESNE ASSIGNMENTS,

TO AUTOMATIC ELECTRIC INC, OFCHICAGG, ILLINOIS, A CORPORATION OF DELA- vW'ARE.

Original application filed to automatic AUTOMATIC TELEPHONE SYSTEM.

November 23, 1920, Serial No. 426,011.

March 14, 1925.

relates in general directively controlled automatic switches are employed to establish connections between calling and called subscribers lines; and one object is to provide a new and improved first selector switch adapted for use in exchanges where the trunk-mg capacity required exceeds 1,000 or not exceed 10,000 lines, but does twice the figures named, the new switch being adapted to pertorm agroup selecting operation con trolled by relays in which either one of two groupsof twentyfive trunk lines each may be selected, and a trunk selecting operation in which the first idle trunk in the selecte use. V

A; further object is't switch, which may d group is taken for 0 provide a selector be a first, second, or third selector, having improved circuit arrangements and characterized especially by a test circuit arrangement in dition of trunk lines is which the idle conindicated by a battery potential .instead of a ground potential.

' This application is a plicat-ion Serial No.

1920, patented Nov.

The means by .which other useful objects are scribed fully in the detailed division of my apet26,011, filed November the foregoing and obtained will be despecification which is to follow, reterenoebeing had to the accompanying drawings forming a part thereof.

In the drawings, Figs. 1, 2, and 3 are circuit diagrams of the es sential apparatus in a telephone system embodying the principles of the invention.

Referring to the drawings, these circuit diagrams show ed automatic switches to establish a talking substation 1%., fig. 1, Fig. 3. The series of the finder switch F,- Fig.

second selectors D and connector Fig. The automatic telep and A" are of the usua usual talking derives for switches. At the eXch-a a plurality of serially relatwhich may be used connection between the and the substation A,

switches comprises 1, the first and E, Fig. 2, and the hone substations A 1 type and have the instrumentalitiesand calling controlling the central oifice n e each line is ro Divided and. this application filed Serial No. 15,435.

vided with a combination line and cut-ofi relay. In the case of the line of substation A, this individual relay is indicated by the reference character 16. The lines'are divided into groups of 100 lines each in accordance with the capacity of the connector and finder switches, and in addition to the individual line relays there are 10 tens relays and 10 units relays for each group, each of the tens relays being common to all of the lines of the group which terminate in the same level and which, therefore, have the same tens digit in their telephone numbers, and each of the units relays being common to all of the lines of the group which have the same final digit in their telephone numbers. The tens and units relays associated with the line of substation A are indicated by the reference characters 17 and 18, re spectively. It may be stated that the function of the tens and units relays is to indicate by their joint action the calling condition of any calling line in finder switches.

The finder switch the selector E, and

the connector H are of the well known Strowger vertical and rotary type so far as their mechanical construction is concerned, and hence will not need to be described in detail. The construction of the finder switch. however, has been changed somewhat in order to permit it to perform its vertical and rotary selecting operations simultaneuosly, as shown in my parentpatent above referred to. named are shown complete in the drawings and will be fully described.

Thefirst selector D is similar in construction to a well known type of rotary line switch. It has two sets of wipers and a double bank with contact sets associated vith each set of wipers. The wipers normally rest on the contact sets last used and the banks of the v The circuits of all the switches Having given a general description of the apparatus used, the operation thereof will now be described more in detail, it being assumed for this purpose that the subscriber at substation A, Fig. 1, desires to obtain a connection with a subscriber at substation A, Fig. 3, The telephone number at substation A will be assumed to be #4567, while the telephone number at substation A is :hEXX23.

l/Vhen the receiver is removed at the calling station a circuit is completed for the tens and units relays l7 and 18, and the line relay 16 over the following path: ground at G winding of units relay 18, resting contact of armature 21 and the said armature, line conductor 12, to and through the telephone at substation A, conductor 11, resting contact or armature 20 and the said armature, upper winding of relay 1G, and the winding of the tens relay 1'? to battery. Upon the closure of the above circuit relays l7 and 18 are energized, while relay 16 is operated suiliciently to close the make contact at its armature 19. This relay is marginally adjusted and when energized over the line circuit it is operated sufiiciently to close the contact named, but does not open the break contacts at armatures 20 and 21. When the units relay 18 pulls up it removes ground from the third test contact in the rotary test banks of all the finder switches in the group having access to the calling line, and the tens relay 17, upon energizing, removes ground from the second test con tact in. the vertical test banks of these finder switches; At the same time, relay 17 connects ground to the starting wire 80 which extends to the second finder switch in the group. This second finder switch is the finder switch F, and assuming that the switch is now in idle condition a circuit will be completed from the grounded starting wire 80 by way of armature 6'0 and its resting contacts, and the winding of line relay 43 to battery. Upon energizing, re-

lay 4-3 completes a circuit at its armature 68,

which includes two branches, the first extending from the said armature 68 to the right by way of the winding of relay stat, armature 79 and its resting contact, and the winding of the vertical magnet 41? to battery, while the second extends to the left by way of the resting contact of arn'iature and the said a nature, winding of relay d5, res-ting contact of armature 7S and the said ari'nature, and the winding of the rotary magnet l8 to battery. At the same time 1- these parallel branch circuits are completed, relay 43 connects the vertical test wiper 93 to the vertical magnet circuit at a point between the said magnet and relayed, and also conz rects the rotary test wiper Set to the rot if magnet circuit at a point midway between the said rotary mag- The two test wipers are at armatures 67 and 66, re-

the vertical i'nagnet 47, being supplied withv direct ground by way or the vertiel test wiper, will be energized. By the operation of the vertical magnet the shaft and Wipers are raised one step and the latter are brought oppositethe second level of bank contacts. In operating, the vertical magnet closes the circuit for the interrupter relay l9 and this a relay upon energizing breaks the circuit of the vertical magnet The vertical magnet is accordingly deenergized and breaks the circuit or" relay 49, which thereupon falls back and again closes the vertical magnet circuit. If the second test contact in the vertical test bank is also grounded, the vertical magnet will now be operated again and the switch will be raised another step, the operation continuing in this manner as long as the test wiper continues to engage grounded test contacts. But in the present case the calling line is terminated in the second level and the second test contact, therefore, will have no ground potential upon it. hen test wiper 93 arrives at the second test contact, therefore, it will tin-d no ground potential, the vertical magnet will not again be energized, and relay 44, being no longer short circuited, will be energized in series with the vertical magnet. Relay H is of very hi h resistance and the vertical magnet remains inoperative. Upon energizing, relay 44 disconnects the test wiper 93 from its winding and connects it to ground instead, in order to make the second level busy.

lVhile the switch shaft vertically, as above described, the rotary magnet i8 is operating to rotate the shaft. The test contact normally engaged by the test wiper 94 is permanently grounded as indicated in the drawings, and when the circuits of and relay ii) are completed by the line relay 43 as previously describedrelay 45 will be short circuited and the rotary magnet 48 will be operated. By the operation of the rotary magnet the main shaft of the finder switch is rotated and the rotary test wiper 94 is brought into engagement with the first of the regular test contacts. lnoperating, the magnet 48 closes the circuit of relay which, upon energizing, breaks the rotary vertical magnet is raising the tile rotary magnet lute magnet circuit. The rotary magnet now deenergizes and breaks the circuit of relay 50, which thereupon falls back and again closes the circuit of th rotary magnet. Since the calling line is terminated in the third con tact set in the second level ground has been removed from the third test contact by the units relay 18, and the first test contact will still be grounded, assuming that the first units relay is not energized by another callin line. This being the case, relay 1-5 will remain short circuited and the rotary magnet 18 will again be energized, with theresult that the main shaft is rotated another step, and the test wiper 9% brought into engagement with the second test contact. For the purpose of this explanation, let it be assumed now that the second line in the sixth level, or line :fiiEXIZSQ is calling, in which case the second units relay will be energized and ground will have been re moved from the second test contact. l hen the test wiper arrives at the second test contact, therefore, it will find no ground po tential, the rotation of the switch will cease, and relay 45, being no longer short circuited, will energize in series with rotary magnet- 48. Relay is of high resistance like relay 44L, and the rotary magnet is not affected. The vertical movement of the switch has already ceased, and relay 44.- is now in energized position. In addition to the functions already explained relay 1st closes a circuit at its armature 78 for the wiper release magnet 52 and this magnet, upon energizing, releases the auxiliary shaft so that the line and private wipers of the finder switch are instantly rotated on to the second contact set in the second level. As soon the auxiliary shaft reaches its normal position with respect to the main shaft, contact springs 51 and are closed. l wo circuits may now be traced which have been closed by the joint energizationflof relays ll and 15. T he first of these extends from ground by way of the winding of slow actine' relay 42, springs 5d and 55, armature 72 and its working contact, working contact of armature 76 and the said armature, and the winding of the rotary magnet 48 to battery. Upon the closure energized. The second circuit referred to is a test circuit and extends from ground by way of the working contact of armature T? and the said armature, armature 7 1 andits working contact, the upper winding of relay 41, and the normally closed contact springs controlled by armature of relay 40/00 the private wiper 91. the circuit is open, for according to the previous assumption the only two calling lines are the line of substation A, which is ter minated in the third contact set in the second level, and another line which is terminated in the second contact setof the sixth of this circuit relay .2 is

At this point, however,

winding of relay 40 to battery.

.nects private wiper level. Since the line terminating in the second contact set in the second level is not calling, its line relay will not have been energized and the bank contact now engaged by the private wiper 91 will not have been connected through to the cut-off winding of the associated line relay. The test circuit described, therefore, will not be completed, and relay 41 will not be energized. lVhen relay 42 attracts its armature 6 1 it prepares a circuit for its rotary magnet 48, and at its armature 5 breaks the circuit of relay The latter relay, therefore, falls back, closes the rotary magnet ci 'cuit at the resting contact of its armature 76, and breaks the circuit of relay 12 at the working contact of thesame armature. Being slow acting, relay 4:2 is not d-eenergized for an instant, and the rotary magnet 48 is thus operated to rotate the shaft and wipers into engagement with the third set of contacts in the second level, test wiper being moved at the same time into engagement with the third test contact in the rotary test bank. The circuits are now in the same condition as when the rotary movement of the switch was first initiated, and the rotation of the switch will be continued if necessary until the test wiper 9 1 locates another ungrounded test contact. But in the present case, the calling line is terminated in the third set of contacts in the second level, upon which the switch wipers are now resting, and ground has been removed from the test contact now engaged by the test wiper 9st by the operation of the units relay 18. It f0llows, therefore, that the rotation of the switch will again be stopped and relay at) will again be energized. As before, circuits are now completed simultaneously for relay 42, and for the upper winding of relay 4-1. This time since the private wiper 91 is now in engagement with bank contact 31, the latter circuit is completed by way of armature 19 and its working contact, and cut-oil winding of relay 16 to battery. Relays 11 and 16 are accordingly energized in series, and the latter relay disconnects line conductors 11 and 12 from the tens and units relays 17 and 18 at armatures '20 and 21, re spectively. Relay 4-1 energizes slightly before relay a2, and its armature 62 closes a shunt around the break contact at armature (55 of the latter relay, and thus prevents opening of the circuit of relay 4!). In addition, relay 4-1 completes a circuit for the switching relay 10 which extends from ground by way of armature 69 and its working contact, armature 63 and its working cont-act, lower winding of relay ll, and the Upon attracting its armature 5S, relay 4:0 discon- 91 from the circuit including the upper winding of relay ll, and connects it instead to the circuit just esill) tablished, which includes the switching relay 10, and the lower winding of relay 41.

It is noted that the release trunk conductor 97 extending to the first selector switch D, Fig. 2, is connected to this circuit at a point between relays 410 and In addition to the operations described, switching relay disconnects ground from armature 64 of relay 12 by means of its an matureb'r", opens the release magnet circuit at armature 59, extends the starting wire to armature 70 of the line relay 45% by means of armature 60, and by means 01: armature 56 and 61 connects up the line wipers and 92. By the latter operation the line conductors 11 and 12 are extended by way of bank contacts 30 and 32, wipers 90 and 92, armatures 56 and (51 and their working contact, trunk conductors 96 and 98, and armatures 114; and 116 of the switching relay 10l of the first selector D to the line relay 100, and to ground, respectively.

lVhcn the calling line is extended to the se lector l) in the manner above explained, the line relay 100 is energized over the line cir cult, and closes a circuit for the slow acting release relay 101. Upon energizing, the latter relay prepares a circuit for slow acting relay 102 at armature 108, and at armature 10'? connects ground to the release trunk conductor 97, thereby establishing a holding circuit which may be traced by way of the said conductor 97, and through the winding 01 the switching relay 40 of the finder switch F to battery, and also by way of armature 58 and its working contact, private wiper 91, bank contact 31, and armature 19 and its working contact, and the cut-elf winding of relay 16 to battery. This holdlug circuit serves to maintain relays 10 and 16 energized throughout the duration of the connection. Ground is also placed upon the private normal conductor 1 1 which extends to multiple connected test contacts in the banks of the connector switches which have access to the line of substation A, thereby guarding the line against intrusion in the usual manner. An instant after the hold ing circuit is established, the line relay 13 of the finder switch F is deenergized, its circuit having been broken by the opera tion of the switching relay -10. Upon deencrgizing, relay 4:3 disconnects the test wipers 93 and 9 1 and breaks the circuits of relays -1 and 45, and also disconnects ground from the lower winding of relay 11. In addition, at its armature 70, re lay -13 extends the starting wire 80 by way of starting wire 81 to the third finder switch of the group. terminating in the second level are calling at this time the tens relay 17 will already have been deenergized and ground will have been removed from the starting wire 80. it, however, some other line in the second if none of the other lines level is calling, relay 17 will remain held up and the third finder switch will be started and will operate to connect with the calling line in the same way as has just been described in the case of the finder switch The foregoing operations by which the line of substation A has been extended through the medium of the finder switch E into connection Withthe first selector 1) have all occurred automatically responsive to' the removal of the receiver from the hook. Y '1 be calling subscriber may now operate his calldevice in accordance with the first digit in the desired number, which is the digits. As a result four interruptions are produced in the line circuit and the line relay 100 at the selector D; is deenergized momentarily four times. Although its circuit is broken momentarily at each deenergization, the slow acting relay 101 remains in operated position and a series or" four impulses are transmitted to the slow acting relay 102. The latter; relay is accordingly operated and retains its armatures attracted until the series of impulses cease. When the release trunk conductor 97 was first grounded, a circuit 5 completed by way of armaturell1 and its r sting contact, the winding of Wiper switc lie relay 105, and the winning of relay 103 to battery. Relay 105 is accordingly now in operated position, but since this relay is of high. resistance, relay 103, which is of relatively low resistance and is marginally adjusted, is not operated. 'Now when the slow acting relay 102 energizes responsive to the impulses received from the line relay 100 it connects the grounded release trunk conductor 97 to the junction of relays 105 and 103, thereby short circuiting the former relay and closing a direct circuit for the latter relay which thereupon energizes. Upon attracting its armature 111, relay 103 closes a locking circuit for itself by way of the resistance 12?, and at armature 112 prepares a circuit for the switching relay 10%, and at its armature 113 prepares the usual testing circuit. Relay 105 is short circuited when relay 102 is first energized, and since the latter relay remains in operated position while four impulses are being transmitted to it the short circuit is maintained long enough to cause relay 105 to fall back. In doing so it breaks the connection to the release trunk at armature 118 and since its initial energizing circuit has already been opened at armature 111 of relay 103, relay 105 cannot again be operated. Thus it will be seen that the wiper set comprising wipers 121, 122, and 123 are connected for use. At the end of the series of impulses relay 102 falls back and at its armature 109 completes a circuit extending through the switching relay 104 and the stepping magnet 128 in series to battery. At the same time, at its armature 110 relay 102 connects the test Wiper v contact, or not.

122 to the above circuit at a the said relay and magnet. The Operation now depends upon whether the test wiper 122 is in engagement with a grounded test it the trunk line terminating in the bank contacts upon which the wiper set in use is standing is busy, the test contact engaged by the test wiper 122 will be grounded, the switching relay 104 will be short circuited, and the stepping magnet 128 being supplied with direct ground by way 01 the test wiper will operate as a buzzer to advance the switch wipers step by step in search of an idle trunk line. This movementwill continue. as long as the test wiper 122 engages grounded test contacts, but in the present case we may assume that when the selector D is taken for use wipers 121, 122, and 123 are standing upon the contact set in which is terminated the trunk line extending to the second selector E, and it may be assumed furthermore that this trunk line is idle. Under these circumstances when the slow acting relay 102 falls back and closes the circuit of the switching relay 104, said relay will not be short circuited and no rotary movement of the switch Will take place, but the said relay 104 will pull up at once in'series with the stepping magnet 128, the magnet remaining inoperative, due to the high resistance or" the switching relay. Upon energizing, relay 10% connects grounded release trunk conductor 97 to the test wiper 122 at its armature 115, and at its armatures 11 1 and 116 disconnects the incoming trunk conductors 96 and 98 from the line relay 100, and tr in ground, respectilvey, and extents them by way of the working contacts of the armatures named, armatures 117- and 120 and their resting contacts, wipers 121 and 123, bank contacts 130 and 132, and armatures 160 and 163 and their resting contacts'to line relay 151 of the second selector E and to ground, respecetively.

When the calling line is extended to the second selector E in this manner, line relay 151 is energized over the line circuit and closes a circuit for the slow acting release relay 152. Upon energizing, the latter relay prepares a circuit for the vertical mag- 155 at its armature 105, and at its arma- 'ture 16 t closes a holding circuit which extends from ground by way the working contact of armature 16% and said armature, release 'trunk conductor 13%, test contact 131, test wiper 122, resting contact of armature 119 and the said armature, working contact 01': armature 113 and the said armature, resting contact or armature 110 and the said armature, armature 115 and its working contact, working contact of armature 112 and the said armature, and resting contact of armature 109 and the said armature to the release trunk conductor 97 where point between joinsthe previously described holding circuit extending back to the finder switch F, and the cut-off winding of relay 16.

This holding circuit is established before theslow acting release relay 101 of the selector D has had time to deneergize, and serves to maintain relays 103 and 10% energized dur ing the connection.

It may be well to pause a moment at this point and consider the operation of the selector D a-little more fully. The system herein contemplated has a capacity of 2000 lines, comprising two groups, which may be termed the 1000 group and the 1000 group. In other words, the first digit in the telephone numbers assigned to one of the groups of lines is always the digit 1, while the first digit in the telephone numbers assigned to the other group of lines is the digit 4:. hen the selector D is taken for use, the wiper switching relay 105' is immediately energized by the grounding of the release trunk conductor 97 and locks itself at its armature 118. Then, it the first digit in'the desired number is the digit 1-, the said relay 105 will be short circuited long enough during the transmission of a series of impulses corresponding to said digit to cause it to fall back, break its locking circuit, and connect up the normally connected set of wipers, allas described in detail in the foregoing paragraphs. However, if the first digit in the desired number is-the digit 1, relay 105 will be short circuited only momentarily, and sincethis relay is slow actin fall back but will remain locked up by way of its armature 118, notwithstanding the fact that its initial energizing. circuit isbroken at-armature 111 of relay 103, and the wiper set comprising wlpers 121, 125, and 126 willremain connected for use. The subsequent operation of selecting an idle trunk will take place the same as in the other case, except that since the alternative wiper set is being used a trunk line will be used which extends to asecond selector in a different group. 1t will be seen then that the selector D may have access to two different groups of second selectors corresponding to the two diilerent thousands, and although this is a small number as compared to the usual ten groups which are accessible to the ordinary standard type of first selector, yet under certain circumstances two thousand groups are all that is required, and in such acase a switch of this type is very desirable. The selector D has no complicated stepping mechanism such as is used in the ordinary selector switch and is, therefore, much cheaper to construct. It also has a decided advantage in that its wipers are normally in engagement with a set of bank contacts, and in the majority of cases no rotary movement oi" the switch is required.

Proceeding now with the explanation, the

git will not connection has been extended as far as the second selector E. When the calling subscriber operates his calling device in accordance with the next digit in the number, whicn is the digit 5, series of five interruptions is, produced in the circuit of the line relay 151 and said relay is accordingly dcenergized momentarily five times. At each deenergization of the line relay an impulse .of current is transmitted through the slow acting series relay 153 and the ver tical magnet 155, and the latter isoperated in the usual manner to raise the switchshaft step by step until the wipers 180, 1 81 and 182 stand opposite the fifth level of bank contacts. Belay 155:5 is energized in series with the vertical magnet and since it is slow acting it retains its armature attracted until the impulses cease. At the end of the vertical movement of the switch, relay 153 is deenergized and since the normal springs 158 l. ave been closed (these springs are closed at the first upward movement or the shaft) a circuit is completed for the rotary r magnet 156 as follows: from the grounded armature 162 by way of the said armature and its resting contact, armature 168 and its working contact, oft normal springs 158, armature 1-66 and its resting contact armature 16'? and its resting contact, and the winding or the rotary magnet 156 to bat tery. The rotary magnet is accordingly o'p erated and advances the switch wipers into engagement with the first set of contacts in the level opposite which they have been raised. In operating, the rotary magnet closes a circuit for the interrupter relay 1534. Upon energizing, relay 154C connects the test wiper 181 with the lower winding of the switching relay 150 at armature 168, and at the same time, or a little later, preferably, breaks the circuit of the rotary magnet at armature 167. upon whether the first trunk line in theselected level is busy or idle. It this trunk line is busy, the test contact engaged by the wiper 181 will have a ground potential upon it, and since the lower winding of relay 150 is connected to ground the said relay 150 will not be operated. The rotary magnet deenergizcs when its circuit is broken at armature 167 and breaks the circuit of the inta'rupter relay 15s which accordingly falls back and again completes the rotary magnet circuit, the rotary ma net being again operated to advancethe switch wipers into engagei'nent with the nest set ot bank contacts. This operation will. continue until the wiper 181 arrives at a test contact having a battery potential upon it, the bat- "ery potential indicating that the associated 1 Assuming that the first idle trunk line is the one shown in the drawing, when the test wiper 181 arrives at test contact 184;, and relay 154: pulls up re- The operation now depends.

sponsive to the closure of its circuit by the rotary magnet, a circuit will be completed forthe switching relay 150 which extends from ground by way of the lower winding of relay 150, armature 168 and its working contact,'test wiper 181, test contact 18%, release trunk conductor 187, armature 216 and .its restin contact armature 227 and its a la resting contact and the upper winding of the line relay 201 of the connector l-l'to battery. Upon the closure of the above circuit, relays 201 and 150 are energized in series and the latter relay closes a locking circuit for itself at its armature 161 at the same time connecting the grounded release trunk conductor 18-41, to the test wiperflSl in order to make the selectedtrunk line busy. Relay 150 alsobreaksthe rotary magnet circuit at its armature 162, and atits armatures 160 and 163 extends the incoming trunk conductors by way or wipers 1 and 182, bank contacts 183 and 185, trunk conductors 186 and 188, and the normally closed contacts at the reversing relay 20 0 to the upper andlower windings of the line relay 201 of the connector H.

N hen the calling line is extendcd to the connector in this manner, the line relay 201 is energized over the line circuit andzclose s a circuit fortheslow acting release relay 202. Upon energizing, the latter relay prepares a circuitfor the verticalmagnet at its armature 215, and at its armature 216 connects ground to the release t-r'unk conductor 187, thereby establishing a holding circuit which maybe traced by way of the said conductor 18?", test contact 18 1, test wiper 181, and the make contacts at armature 161 to the release trunk conductor 13 1, where it joins the pre viously described holding circuit extending back through the selector D and the finder switch F. The upper, winding of the switching relay 150 is connected to the holdng circuit at armature 161, and this relay is, therefore, held up throughout the duration of the connection. I

The calling subscriber may now operate hiscalling device in accordance with the next digit in the desired number. As a result six interruptions are produced in the line circuit in the usual manner and the line relay 201 18, deenergized momentarily six times, at each deenergization sending an impulse oil' current through the slow acting relay 208 and the vertical magnet 208 in series. B the operation of the vertical magnet, the connector shaft is raised step bystep until the wipers are raised opposite the sixth level of'loank contacts. The slow acting relay 203 is energized in series with the vertical magnet and retains its armature 217 attracted during the series of impulses, thereby preventing the vertical magnet circuit from being opened by the shifting of the off normal springs 211, 212, and 213, which takes place at the first upward movement of the switch shaft. At the end of the vertical movement of the switch, the slow acting relay 203 falls back and transfers the operating circuit to the rotary magnet 209.

The calling subscriber may nowv operate his calling device for the next and final digit in the number, this being the digit '7. In response to the interruptions thus produced in the line circuit theline relay 201 is deenergized momentarily seven times, and at each deenergization transmits an impulse of current through the rotary magnet 209. By the operation of the rotary magnet the switch wipers 250, 251, and 252, are rotated step by step and are finally brought to rest in engagement with the particular set of bank contacts in which the line of substation A is'terminated, these contacts being indicated by the reference characters 253, 25 i, and 255. nected to the operating circuit and is energized in parallel with the rotary magnet 209, its armatures being held up continuously throughout the rotary movement of the switch. At armature 225, relay 206 connects the test wiper 251 to the winding of the test relay 205, and at its armature 224 relay 206 closes a shunt around the break contact at armature 222 of the test relay, the latter operation being a precautionary measure which prevents the rotary magnet circuit from being opened in caseithe test wiper should engage a grounded contact while the switch is rotating.

it may be assumed first that the called line is busy when connected above. Under these circumstances, when the test wiper 251 comes to rest'in engagement with test contact an it will find a ground potential thereon and the test relay 205 will be energized. 1 in instant later. when the slow acting relay 206 falls back at the end of the rotary movement of the switch, the test relay established a locking circuit for itself at its armature 221. The test relay also breaks the rotary magnet circuit at its armature 222, and at its armature 223 connccts a lead from the busy signalling machine to the lower side of the calling line. By this operation an audible busy signal. is transmitted to the calling subscriber, and being thus vised that the desired called line is for. the time being inaccessible, he will replace his receiver.

Let us assume now'that the desired line is idle when called. In this case, when the test wiper 251 arrives at the test contact 254C it will find no ground potential and the test relay 205 will not be energized. Then, when the slow acting relay 206 falls back an in stant later, a circuit is completed for the switching relay 207 over thefollowing path: From the grounded release trunk conductor 18? by way of armature 221 and its resting The slow acting relay 206 is con" with, as explainedticular utility in connection with contact, upper ture, test wiper 251, test contact 254:, private normal conductor 26 1, and the cut-off winding of the combination line and cutoff relay 270 to battery. Relays 207 and 270 are energized in series upon the completion of the above circuit, and the latter relay operates to disconnect the conductors 260 and 261 of the called line from their normal battery and ground connections at the exchange. In the connector, when the switching relay 207'is energized it establishes a locking circuit for itself at. its armature 229, grounds the test wiper 251 at armature 228, breaks the connection at its arn'iature 227 which extends from the upper winding of the line relay 201 to the resting contact of armature 216, opens the rotary magnet at armature 230, and at armatures 226 and and lower line wipers 250 and 252. Ringing on rent from the generator GEN is now projected intermittently out over the called line in order to operate the bridged ringer at substation A. The return path for the ringing current includes the upper winding of the ring'cut-oif relay 20d, and when the called subscriber answers the ring cut-off relay is energized, establishing a locking circuit for itself at its armature 219. In addition, relay 204 breaks the ringing circuit at its arinatures 218 and 220 and at the working cont-acts of these same armatures finally completes the talking connection.

The desired connection has now been established and the calling and called subscribers may converse as desired. The transmitter at the calling station A is supplied with talking current through the windings of the double wound line relay 201 of the connector H, while the transmitter at the called station A is supplied with talking current through'the windings of the double wound back bridge relay 200. The latter relay is energized immediately following the energization of the ring-cut-ofl' relay 204C and reverses the direction of current flow in the calling line. This operation is of no parthe apparatus shown herein, but is standard operation provided for in order to control measured service equipment where such equipment is furnished.

At the end of the conversation, both subscribers will hang up their receivers. The

release of the connection is controlled by the replacement of the receiver at the calling substation A in the following manner: When the receiver is hung up, the line and release relays 201 and 202 of the connector ii are deenergized and jointly close a circuit for the release magnet 210, which operates to restore the connector to position in the usual manner. Relay 202 also breaks the holding circuit extending back to the Sc winding of relay 207., resting 281 connects up the upper ice lectors E and D, finder switch F, and the cut-oil winding of the combination line and cut-ott relay 18, and all relays in the switches named which have been held up over the grounded holding circuit are permitted to deener 'ise. At the selector E, when the switchin relay 150 falls bacl: a circuit is completed for the release agnet- 157, which operates to restore the selector switch to nor mal position. In the selector D the wipers are not restored; relays 103 and 10a simply fall back and the latter relay disconnects the wipers. in the finder switch F, when the switching relay l0 is deener "Jed it not 51,

closes a circuit of the release ma which extends by way of the grounded arresting contact, resting mature 69 and its contact of armature 59 and the said arma ture, rotary oli" normal spring 53 and its working contact, and the winding of the release magnet 51 to battery. By the opera tion of the release magnet 51 the switch shaft is restored to its normal position. It is noted that the (ill normal spring whose function it is to brealtthe release magnet circuit after the switch has been fully restored, is operated on the li note ment of the main shaft, 1' Y than on the first vertical movement as is the usual. case and this is necessary on account of the fact that the line and private wipers oi the finder switch normally stand opposite the firstlevel of bani; contacts, from which it will be seen if the calling line is a line terminating in the level no vertical i'novement oi the switch will talze plac Therefore, the oit' normal spring 53 is arranged to be operated on the lirst rotary movement, stated, in order to insure that it will be actuated in all cases. 7

Having described my invention, what I consider to be new and desire to have protected by Letters Patent will be pointed outin the appended claims.

What is claimed is:

1. ln a telephone system, an automatic switch having group and trunk selecting functions, contacts associated with said switch. and wipers for said switch resting normally on the contacts last used. c

2. ln a telephone system, a plurality o'i groups of trunk lines, an automatic switch comprising subscriber controlled means for selecting a group of said trunk lines, wipers in said switch automatically operable to connect with an idle trunk line in the selected mp, said wipers being normally associated nxth some trunk line in said group, and means tor completing the connection through said switch without moving said wipers it the trunk line with which they are associated is idle.

In a telephone system, an automatic switch, trunk lines accessible to said switch and arranged in groups, contacts in which said trunk lines terminate, wipers in said switch resting normally on. some of said contacts, and means whereby a calling sub scriber can operate said switch. to select a desired group of saidtrunk lines and to establish connection with an idle trunk line in the selected group while maintaining said wipers in their antecedent normal position.

In a telephone system,'an automatic switclntrunk line's accessible .to said switch and arranged in groups, contacts in which said trunk lines terminate, wipers in said switch resting normally on some of said contacts, means in said switch for performing group and trunk selecting operations to nect with an idle trunk line in any one said groups, and means whereby the trunk selecting operation is omitted in case the wipers are already associated with an idle trunk line. 7

5. In a telephone system, a selector switch, wipers for said switch having movement in a torwart direction only and having no normal position, a plurality of groups of trunk lines accessible to the wipers oi said switch, means whereby a calling subscriber can operate said switch to select a desired group of trunk lines, and means for then automatically operating the switch wipers to select and connect with an idle trunk line in the selected group. v r

6. In a telephone system, an automatic selector switch, a plurality of groups of trunk lines accessible to said switch, a relay directively controlled by a calling subscriber for selecting a desired group of trunk lines, and step by step mechanism automatically controlled to select an idle trunk line in the selected group.

7. In a telephone system, an automatic selector switch, two groups of trunk lines accessible to said switch, a group selecting relay, subscriber controlled means for producing either short or long changes in the circuit of said relay, the said relay being responsive to such circuit changes to select one or the other of said trunk groups, and means for automatically selecting an idle trunk in the selected group.

8. In a telephone system, an automatic selector switch, two groups of trunk lines accessible to said switch, subscriber controlled means tor connecting with said switch and for transmitting current impulses thereto, means in said switch responsive to a. single impulse for selecting one or said groups of trunk lines, means in said switch responsive to any number of impulses greater than one for selecting the other. oi said groups of trunl: lines, and automatic means in said switch for selecting an idle trunk line in the selected group.

9. In a telephone system, an automatic selector switch having directive group and automatic trunk selecting movements, a line relay for said switch, primary and secondary magnets for operating said switch in its two movements, respectively, a circuit for each magnet, and contacts in both circuits directly controlled by said line relay.

10. In a telephone system, an automatic selector switch having directive group and automatic trunk selecting movements, a line relay for said switch, primary and secondary magnets, for operating saidswitch in its two movements, respectively, a circuit for each magnet, a contact on the line relay for closing the primary circuit, a contact on the line relay for preparing the secondar circuit, a slow acting relay and contact thereon for closing the secondary circuit, an interrupter relay energized by the secondary magnet when it is operated, anda contact on said interrupter relay for opening the secondary circuit. v

11. In a telephone system, an automatic selector switch having directive group and automatic trunk selecting movements, a line relay for said switch, primary and secondary magnets for operating said switch in its two movements, respectively, a circuit for each magnet, an interrupter relay for opening the secondary circuit, line and test wipers for said switch, a switching relay for connecting the line circuit through to said line wipers, and a contact closed by said interrupter relay when it is energized to connect a winding of said switching relay to said test wiper.

12. In a telephone system, an automatic selector switch having directive group and automatic trunk selecting movements, a line relay for said switch, primary and secondary magnets for operating said switch in its two movements, respectively, a circuit for each magnet, an interrupter relay for opening the secondary circuit, line and test wipers for said switch, a switching relay for connecting theline circuit through to said line wipers, a contact closed by said interrupter relay when it is energized to connect one side of a winding of said switching relay to said test wiper, an exchange battery, a connection to one pole of the battery on the other side of said switching whereby said relay is energized when said test wiper engages a test contact connected to the other pole of the exchange battery, and a locking winding for holding said switching relay energized.

13. In a telephone system, switches in serial relation, a controlling line relay in each switch, means for operating the first switch under control of its line relay to connect with the second switch, a switching relay in said first switch for completing the connection, and a test circuit including said switching relay and the line relay of said second switch.

14. In a telephone system,

relay winding,

two groups of two automatic trunk lines, subscriber controlled means for selecting one or the other group, said means selecting one group if the duration of control is any amount of time more than a predetermined time and the other group it it is less than said predetermined time.

15. In a telephone system, two groups of trunk lines, subscriber controlled means for selecting one or the other group, said means selecting one group if the duration or control is any amount of time more than-a predetermined time and the other group if it is less than said predetermined time, and means for automatically selecting an idle trunk in the selected group.

16. In a telephone system, two groups of trunk lines, subscriber controlled means for select-ing one or the other group, said means selecting one group it the duration of control is any amount of time more than a predetermined time and the other group if it is less than said predetermined time, means for automatically selecting an idle trunk in the selected group, saidmeans including a wiper normally resting on the trunk line last used, and means for rendering said last named means ineitiective if the trunk line is idle.

17. In a telephone system, an automatic selector switch, two groups of trunk lines accessible to said switch, a group selecting relay, subscriber controlled means for producing changes of varying duration in the circuit of said relay, said relay being arranged to select one or the other of said groups depending on whether the said changes continue for variable periods of time greater or less than a predetermined time.

18. In a telephone system, a numerical switch having a plurality of groups of trunk terminating contacts, a wiper for each group of contacts, said wiper when idle resting in the position last used, subscriber controlled means for 'directively selecting the wiper to be used,-and means automatically operating the wiper to select an idle trunk in the event the trunk contact upon which the selected wiper rests is not idle.

19. A trunk line comprising two branches, means for selecting one or the other branch, said means including a slow to release relay arranged to select one branch when energized and the other when deenergized, means establishing an energizing circuit and then a holding circuit for said relay, and subscriber controlled means for first opening the energizing circuit and then rendering the holding circuit ineffective for a period of time controlled by the subscriber, whereby it the said period of time is less than a predetermined amount, the relay will be maintained, whereas if it is greater than said predetermined amount the relay will deenergize and open its holding, circuit.

20, A trunk selecting switch including a line wiper, a test wiper, and a switching relay, a trunk accessible to said wipers, said trunk having a line relay, and means for simultaneously establishing initial energizing circuits both for the switching relay andsaid'line relay when the test wiper connects with the trunk line.

21. A trunk selecting switch including line and test wipers and a switching relay, a trunk accessible to said wipers, said trunk having a line relay, and nieai'is tor simultaneously establishing an energizing circuit both for the switching relay and said line relay when said test wiper connects with said trunk line, and means whereby said switching relay upon operating establishes a holding circuit for itself and a circuit for said line relay through the talking strands of the trunk line, andsaid line relay upon operat ing causes the breaking the first 'men tioned circuit.

22. in a telephone ,ystem, an automatic switch having a line relay, means for extending a calling line to said switch, and means for automatically closing a local circuit for said line relay to energize the same independent of the calling line.

23. In a telephone system, a trunk line terminating in an automatic switch, trunk lines divided into groups accessible thereto, said switch being responsive to a digit of a called number to select a particular group, line wipers for said switch always in electrical engagement with some one of said trunk lines, which connected trunk line is always the one last employed by said switch for extending a call, means for seizing the first mentioned trunk line and for operating said switch into selective relation with one of said groups 01" trunk lines, and means then operative for causing said switch to select an idle trunk line in the selected group,-

24. In a telephone system, a trunk line terminating in an automatic switch, trunk lines divided into groups accessible thereto, wipers for said switch normally in electrical engagement with the trunk line used in the previously established connection, means for seizing said first trunl line and for operating said switch into selective relation with one of said groups of trunk lines, automatic means then operative for causing said vitch to select an idle trunk line in the selected group, and means operative ipers of engagement with the trunlr lineused the previously estahlis 16d connection, means. for

sci said trunk i s and for operating said switch into selective relation with one of said groups of trunk lines, automatic means'then operative for causing said switch to select an idle trunk l ne in the selected group, and means operative it the wipers of said switch are standing in engagement with an idle trunl; line in the desired group for causing said switch .to connect with this trunk line.

26. In a telephone system, a calling line, an automatic switch, trunk lines and asso ciated contacts divided'into a plurality of groups, said switch having agroup selecting operation and a trunk selecting operation, said switch being normally in selective relation with regard to a trunk line'in one of said groups, means controlledtrom said calling line in response to a digit of a called number for causing both group and trunk selecting operations of said switch to select one of said trunks and to connect with the contacts thereof, and means permittingthe omission of both of said operations provided said switch is already associated *ith an idle trunk in the proper group.

Signedhy me at Chicago, CoolcCounty, Illinois, this 11th day of March, 1925.

RODNEY G. LICMARDSON.

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