US1753491A - Automatic telephone system - Google Patents

Description

- April 1930. J, wlcKs 1,753,491

AUTOMATIC TELEPHONE SYSTEM Original Filed-Feb. 11, 1925 3 Shi ts-Sheet 1 K -Im.ran ur- Jul-Ln LJmks April 8, 1930. J, w c s AUTOMATIC TELEPHONE SYSTEM Original Filed Feb. 11, 1925 3 Sheets-Sheet 2 April 8, 1930.

J. wlcKs AUTOMATIC TELEPHONE SYSTEM Original Filed Feb. 11, 1925 5 Sheets-Sheet 5 0 0 5 in; Q08 QM" M ma xmsh n h 1 @w H Q M. NMNQ s. H @mm .l VI E Jmhn Mmks Patented Apr. 8, 1930 UNITED STATES PATENT OFFICE JOHN WICKS, OF OAK PARK, ILLINOIS, ASSIGNOB, BY MESNE ASSIGNMENTS, TO AUTO- HATIC ELECTRIC INC., OF CHICAGO, ILLINOIS, A CORPORATION OF DELAWARE I AUTOMATIC TELEPHONE SYSTEM Application filed February 11, 1925, Serial No. 8,343. Renewed m 12, 1928.

This invention relates in general to automatic telephone systems, more especially to such systems in which the switches are controlled directly by the calling subscriber.

In the well known automatic systems of 10,000 line capacity, first and second selectors and connectors are used to select the four digits of the call number. Furthermore, in such a system, there is one large group of first selectors, ten smaller groups of second selectors and one hundred still smaller groups of connectors. The use of a plurality of groups of second selectors and connectors tends towards a use of these switches that is less eificient than if they were all in one larger group. This is unavoidable. The second-selectors of an automatic system of the well known type are, mechanically and electrically, identical with the first selectors, and the connectors, the least economically used of all, are the most complicated.

This well known system has been simplified in prior inventions by including in the selector some of the functions usually performed by the connector, these functions being the control of ringing current and battery feed to both the calling and called parties.

In the present invention I have further simplified the switches of the system by including the above functions in the first selector, by arranging the first selector to extend holding ground forward to succeeding switches, and by employing the so-called direct pulsing system. In such a system the line relay of the first selector delivers impulses first to the magnets of the selector and later to the magnets of the second selector and connector directly, without the intervention of another relay.

I have further simplified the system as a whole by including the selection of the frequency of ringing current in the first selector. This eliminates the necessity of grouping party lines and the use of a special party line connector. In the system of the present invention, party lines and straight lines can be indiscriminately intermingled in the connector banks, thereby permitting a more uniform distribution of traffic and, consequently,

a more economical use of the switching equipment.

In an automatic telephone exchange of the usual type, in which about 3000 or 4000 of a possible 10,000 lines are installed, a large number of the levels of the first selector banks are idle, and, consequently, the switches are not used efiiciently. Double wiper selectors and connectors eliminate the necessity of sec-- ond selectors and permit an cflicient use of the first selectors. By such design a 4000 line system can be called with atwo-switch switch train.

Accordingly, a further object of this invention is the design of an improved double wiper selector and connector incorporating the above mentioned simplification. In the double wiper switch of this invention the combination of wipers to be used for a call is controlled from the first selector by means of the setting of a minor switch contained therein.

In a system containing party lines, provision must be made for revertive calls, that is calls between subscribers on the same arty line. Accordingly, a further object of this invention is to provide revertive call switches accessible and operable from the first selectors.

The established custom in automatic telephone systems provides a so-called 0 operator to handle special calls and to assist needy subscribers in establishing connections. further object of this invention provides special circuit arrangements in the first selector to enable the subscriber to reach the 0 operator by dialling only the 0 digit. Other objects of this invention will be best understood from the detailed specification and claims which follow.

While I have chosen to show my invention in connection with double wiper switches, it is equally applicable to switches having a single group of wipers. There are many modifications that will be apparent to those skilled in the art without departing from the scope of the invention, and I am, therefore,

not to be limited by the specific disclosure described herein.

The drawings consisting of Figs. 1, 2, and 3, when arranged with Fig. 1 to the left of Fig. 2, and 3 to the right, show one application of e invention. Fi 1 shows the callin telephone A and its individual line switcfi C, which has access to the first selectors E. Fig. 2 shows the intermediate selector E, connectors H and H the reverting call switch RC and the 0 operators position, together with the trunking layout which makes them accessible to the first selector E. Fig. 3 shows the connector H, two called stations A and A each with its individual line switch C and 0 respectively.

Referring to Fig. 1 in more detail, the calling telephone A is of the usual automatic type in which the impulse springs I are used to produce short interruptions in the line circuit to control the automatic switches at the central oflice. The individual line switch C is of the usual rotary type in which the wipers have no normal position, but remain, when not in use, on the trunk last used. The first selector E is of the usual Strowger, vertical and rotary motion type, with the circuits modified to meet the needs of this invention. Minor switches M and M have been added, the former to select the frequency of ringing current that is to be used in signalling the called line, and the latter to select the wipers that are to be used in a manner which will be explained more fully hereinafter. The first selector E carries two sets of wipers, the customary positive and negative line and the private wipers comprising each set. By this arrangement the first selector is a twenty level selector, vertically, and is further arranged to rotate over ten trunks in each level.

Referring to Fig. 2 in more detail, the intermediate selector E is of the well known Strowger vertical and rotary motion type in which the circuits have been modified by this invention. The usual Strowger selector uses five or six relays to control its three motor magnets. The modified Strowger selector, as shown at E, uses but three relays to control the magnets. The connectors H and H shown at the bottom of Fig. 2 are identical in circuit and structure to the connector H shown in Fig. 3. The reverting call switch RC may be any one of several well known reverting call switches, such as that disclosed in the Patent N 0. 1,306,716, granted to Powell on June 17, 1919, which enables a subscriber on a multi-party line to call another party on the same line. The cord circuits of the 0 operators circuitv may be any one of the well known operators circuits used in connection with calls from automatic to manual exchanges.

Referring to Fig. 3 in more detail, the connector H is of the well known Strowger vertical and rotary motion type, with the circuits modified in accordance with the objects of this invention. The modifications have resulted in reducin the switch to a simpler form, having but ve relays and three motor train of three switches.

magnets instead of eight relays as in the usual switch.

In the drawings I have shown several batteries to simplify the drawings. In practice, however, there would be but one battery, preferably with its positive pole grounded.

The simplification of the intermediate selectors and connectors has been accomplished by imposing upon the first selector man of the duties that are ordinarily performe by the connectors. The first selector, in response to the first digit, determines which of its own wipers and which of the connectors wipers are to be used. The second digit operates the minor switch M to select the frequency of ringing current that is to he used and the side of the line over which the ringing current is to be applied. The first selector not only supplies the ringing current, in this invention, but it also supplies talking battery for both the called and the calling parties. In order to still further reduce the intermediate selector and connector forms, the so-called direct pulsing system is employed. In such a system, the line relay of the first selector delivers impulses not only to the magnets of the first selector, but also to the magnets of the intermediate selector and the connector, without the intervention of another ulsing relay. The minor switch M of the t st selector E is the wiper selecting switch controllin the choice of wipers in the first selector an in the connector. If, for example, the subscriber at A desires to call the subscriber at A whose number is assumed to be 254500, he will first operate his calling device to transmit the digit 2.

The minor switch M responds to the digit 2 and sets its wipers in such a position as to choose the upper set of wipers of the first selector, and the upper set of wipers in the connector. If, on the other hand, the calling party at A desires to call the station A, whose number is assumed to be 314500, the minor switch M responding to the first digit 3 sets its wipers in such a position that the upper set of wipers of the first selector and the lower set of wipers of the connector are used.

The above mentioned calls assume the system expanded by the introduction of intermediate selector E, in which case a total of 40,000 lines could be called with a switch Each of these lines could be party lines with ten subscribers, so that 400,000 subscribers could be served by such a system. It is also advantageous to apply the same principles of switching to smaller exchange areas in which the total number of lines would not exceed 4000. In such application of the invention the intermediate selector E would be omitted and the banks of the first selector E would be multipled directly to the connector H. In Fig. 2 I have shown such an arrangement with the banks of the first-selector mitltipled. directly to connectors H and H it being under-' stood that these connectors are shown in detail in the switch H of Fig. 3.

In accordance with the well established practice I have provided a manual operators position known as the operator for the purpose of handling toll and other special calls. It is desired that such a position be reached by dialling simply one number which is accomplished in this invention by means of special circuit arrangements in the first selector E, which will be explained in detail hereinafter.

Provision must also be made so that subscribers on a party line may call other subscribers on the same line, for which purpose the reverting call switch of the aforementioned patent is adapted. This reverting call switch is reached through the tenth level of the bank of the first selector over which the upper set of wipers are moved. The circuits of the selector are arranged so that when a call is directed to the reverting call switch the first selector switches through immediately, extending the'calling line clear of attachments to the reverting call switch, enabling the calling subscriber to operate it in the well known manner.

Having thus described my invention in general, I will now give a detailed description of it. Assume first that the calling subscriber at A desires to call the subscriber at station A whose number is 254500.

lVhen the calling subscriber at A removes his receiver, he completes a circuit for the line relay 11 of his line switch C, which eX- tends from ground through spring and its normal contact, line conductor 1, hook switch, receiver, transmitter, and impulse springs I of the telephone A, line conductor 2, through spring 3 and its normal contact, through the line relay 11 to grounded battery. The line relay ll energizes over the above circuit. The operation of the line switch C from this point depends upon whether or not the trunk upon whichthe wipers 80, 81 and 82 are resting, is busy at the moment. If that trunk is busy, busy ground potential will be presentlupon the bank contacts upon which wiper 81 is resting and a circuit will be completed from that grounded contact through wiper 81, through spring 4 and its break contact, through spring 7 and its make contact, through the interrupter spring 6 and its break contact, through motor magnet 23 to grounded battery. The magnet 23 energizes over the above circuit which is interrupted at spring 6 when the armature has completed its stroke. The wipers are then advanced in the well known manner to the trunk and if that trunk is busy the above mentioned circuit will again be closed and the wipers again moved, until an idle trunk is found. Assume that the first idle trunk encountered is the one-comprising conductors 104, 105 and 106,

leading to'the first selector E. That trunk being idle there will be no ground potential upon the bank contact encountered by wiper- 81 and the cut-oil relay will energize over the circuit extending from ground through spring 8 and its make contact, through the winding of relay 10, through the interrupter spring 6 and its break contact. through the winding of magnet 23, to grounded battery. The high resistance ot'relay 10 prevents magnet 23 from energizing. lVhen relay 10 energizes the line conductors 1 and 2 are switched through to the trunk leading to the first selector E over circuits extending from ground through the lower winding of the line relay 1.3, through spring 34 and its normal contact, conductor 106, wiper 82 of the line switch C, spring 5 and its make contact, line conductor 1, through the telephone to line conductor 2, through spring 3 and its make contact, wiper 80 and its associated bank contact, conductor 105, spring 31' and its break contact, through the upper winding of relay 13 to grounded negative battery. Relay 13 energizes. and upon energizing completes a circuit to the release relay 15, which extends from ground to spring 33 and its normal contact, through spring 35 and its make contact, through the Winding of relay 15 to grounded battery. Relay 15, upon energizing extends a ground from spring and its make contact, spring 38' and its normal contact, conductor 104, wiper 81 and its associated bank contact, spring 4 and its make contact, through the winding of relay 10. through spring 6 and its break contact, through magnet 23 to grounded battery. \Vhen the relay 10 was energized it opened the circuit previously traced for the relay 11, which remained in its energized position for a moment by virtue of the copper slug on its core and the ground connection from relay 15 was received through relay 10 before relay 11 had restored. The first selector E upon being seized for the instant call is made busy to other'calls by virtue of ground on conductor 104 which is multipled to the banks of all of the other line switches.

The operation of relay 15 closes the dial tone circuit which may be traced from the dial tone, through spring 42 and it makes contact, through spring 37 and its break contact, through conductor 132, through spring 57 and its break contact, through condenser 138, through spring 53 and its break contact, through conductor 110, through condenser 9', conductor 108, through the lower winding of relay 13, to ground. This tone, which is superimposed on the portion of the line circuit of the calling subscriber is audible to him and informs him that the first selector is ready to receive the impulses he may dial. Relay 15, upon energizing also prepares a link in the impulsing circuit at spring 41 and its make contact, and closes the circuit of control relay 17, which may be traced from ground through spring 40 and its make contact, conductors 122 and 122', conductor 150, through spring 79 and its break contact, conductor 152, conductor 135, through the coil of relay 17 to grounded battery. Relay 17 energizes over the above circuit and prepares the impulsing circuit which will be explained hereinafter.

The calling subscriber upon hearing the dial tone operates his calling device in accordance with the first digit of the called number, in this case 2, to operate the minor switch M to select the combination of wipers to be used. The calling device springs I open a the previously traced circuit for line relay 13 twice, allowing the relay to fall back to transmit impulses to the switch mechanism.

The falling back of relay 13 upon each interruption of its circuit opens the circuit of relay 15 which, being slow to release because of the copper slug on its core remains in its energized position during the momentary interruptions of the current through its coil. The falling back of relay 13 also completes the impulsing circuit sending to ground impulses from spring 33 and its grounded break contact, spring 35 and its break contact, spring 41 and its make contact, conductor 134 where it divides, one division proceeding via conductor 147 conductor 148, spring 69 and its break contact, conductor 149, spring 56 and its break contact, conductor 136', spring 49 and its make contact, conductor 136', through winding of motor magnet 29 to grounded battery; the other division proceeding via spring 69 and its break contact, conductor 133, through the win ding of relay 16 to grounded battery. Magnet 29 advances the wipers to the second bank contact and relay 16 energizes and remains energized during the series of impulses.

With the wiper 87 of M set on the second back contact, no circuit is completed by it, and the upper set of wipers of E are thereby chosen. Relay 22, by means of which the lower set of wipers are substituted for the upper, is energized through wiper 87 when in engagement with either the first, fourth or fifth bank contact over the obvious circuit. The setting of wiper 86 on the second contact determines the set of connector wipers to be used, in a manner that will be hereinafter described.

Shortly after the completion of the second impulse the relay 16 releases. unlocking the holding circuit to relay 17. The circuit over which relay 17 was originally energized was opened at the ofi' normal spring 79 when the minor switch M stepped to the first contact. Relay 17 therefore falls back and at spring 49 prepares the impulsing circuit for the second digit of the called number, which is directed to the frequency selecting minor switch M. When the callin subscriber transmits the second digit, which in this case is 5, the line relay 13 falls back as before and closes the above traced circuit to the multiple relay 16, which energizes without effeet at this time, and also closes a circuit traceable from ground through spring 33 and its break contact, spring 35 and its break contact, spring 41 and its make contact, conductor 134, through conductor 147, spring 69 and its break contact, conductor 149, through spring 56 and its break contact, through con ductor 136, through spring 49 and its break contact, conductor 115, through the winding of motor magnet 27 of M, to grounded battery. Five impulses are transmitted over the above traced circuit, causing relay 27 to energize five times and to advance its wipers 84 and 85 of the minor switch M into contact with the fifth bank terminal. When the wipers 84 and 85 are stepped out of their normal position, the off normal springs 77 and 78 operate for a purpose which will be hereinafter described. a V Y At the end of the second series of impulses, relay 16 falls back and at spring 43 closes a circuit which may be traced from ground through spring 40 and its make contact, through spring 43' and its break contact, conductor 124, through spring 59 and its break contact, conductor 112, spring 77 and its make contact, conductor 113, through spring 66 and its break contact, conductor 140, through spring 55 and its break contact, conductor 101, through spring 32 and its break contact, conductor 102, through the winding of relay 19. over conductor 145, through the resistance B, through the second bank termi nal and wiper 86 of minor switch M, to grounded battery. Relay 19 energizes over the above circuit and at springs 56, 57 and 58 prepares the impulsing circuit for the next digit of the call number. At spring 55 and its make contact the energizing circuit just traced for relay 19 is transferred to the release trunk over conductor 141, spring 61 and its break contact, conductor 150, through conductor 122, to ground at spring 40 and its make contact.

The third digit of the called number, in this case 4, operates the relay 13 as before. \Vhen relay 13 falls back it closes the previously traced circuit to relay 16, which energizes and at spring 43 prepares a point in the circuit of relay 20. Relay 13, upon falling back, also closes a circuit traceable from ground through spring 33 and its break contact, spring 35 and its break contact, spring 41 and its make contact, conductor 134, conductor 147, through spring 69 and its break contact, conductor 149, spring 56 and its make contact, through conductor 130.

through the winding of vertical magnet 7 circuit and steps the shaft of the selector up four steps. When the selector shaft, not shown, is stepped up one step vertically, the off normal switch comprlsing springs 36. 37. 50 and 128 is operated in the well known manner. Spring 50, upon operating. closes the circuit of rotary interrupter relay 20 which is traceable from ground, spring and its make contact, spring 43 and its make contact, conductor 125, spring 62 and its break contact, conductor 142. spring and 1ts make contact, conductor 143, through relay 20 to grounded battery. Relay 20 energizes over this circuit and at spring 59 prepares a point in the encuit of rotary magnet 26. Upon the completion of the transmission of the vertical 1mpulses the relay 16 restores, closing a circuit which may be traced from grounded release trunk conductor 122, through spring 43 and its break contact, conductor 124, spring 59 and its make contact, through the winding of magnet 26 to grounded battery. Magnet 26 ener izes over the above circuit and steps the shait and wipers one rotary step into contact with the first trunk in the level.

Relay 16 upon restoring also opens the c1rcuit of relay 20 at spring 43. The'make before break spring combination at 43, however, retains the circuit of relay 2O closed long enough to permit the rotary magnet 26 to energize before its circuit is opened at spring 59.

If the first trunk is busy at the moment the wiper 89 will encounter a guarding ground, closing a circuit from grounded bank contact such as 234, wiper 89, conductor 157,

spring 72 and its break contact, spring 63 and its break contact, spring 73 and its make contact, spring 71 and its break contact, con-' ductor 142', spring 50 and its make contact, conductor 143, through the winding of 1nterrupter relay 20 to grounded battery. Eelay 20 energizes over the above traced circuit and again closes the circuit for rotary magnet 26 at the spring 59 and its make contact, causing the magnet 26 to advance the wipers another step. This operation continues as long as the test wiper 89 encounters grounded contacts.

Switching relay 21 is prevented from energizing during the trunk hunting operation by being short circuited. It is directly connected to the grounded release trunk conductor 122 at its upper end and to the grounded wiper 89 at its lower end over a circuit traceable from lower terminal relay 21. conductor 155, spring 63 and its break contact, spring 72 and its break contact, and conductor 157 to wiper 89.

Then the first idle switch is encountered, assumed in this case to be switch E, the wiper 89 will not be connected to a grounded test contact, and the relay 21, which was prevented from energizing during the trunk hunting operation by grounded test contacts, will now energize over a circuit traceable from grounded release trunk conductor 122, conductor 150, through the winding of rela 21, through conductors 155 and 156, through the rotary oil normal spring 73 and its break contact, through interrupter spring 71 and its break contact, over conductor 142, throu h vertical off normal spring 50 and its ma e contact, conductor 143, through the Winding of relay 20, to grounded battery. Relay 20 is so constructec that it will not energize in series with the high resistance relay 21. Relay 21 energizes over the above circuit and at springs 61, 63 and 69 connects the trunk conductors of selector E through wipers 88, 89 and 90 to the trunk conductors 261, 264 and 267 of the intermediate selector E. The holding circuit of relay 19, which was traced through spring 61 and its break contact, is transferred to grounded spring 210 and its break contact of selector E, conductor 261, contact 231 now engaged by wiper 88, conductor 155, spring 70 and its break contact, spring 61 and its make contact, conductor 141', spring 55 and its make contact 55', conductor 101, spring 32 and its break contact, conductor 102, through the winding of relay 19, through conductor 145, through the resistance R, the second bank contact of the minor switch M, and wiper 86 to grounded battery, holding relay 19 in its energized position. Relay 21. upon energizing, interrupts the circuit of the relay 20 at spring 62 and its break contact, thereby making it impossible for the relay 20 to again energize and close the circuit of the rotary magnet 26. At spring 68 and its make contact, the relay 21 prepares a link in the ringing circuit which will be explained hereinafter. The operation of relay 21 extends the release trunk conductor 122 through spring 63 and its make contact, spring 72 and its break contact, conductor 157, Wiper 89 now in engagement with bank contact 234, conductor 264, through the lower winding of switching relay 201 to grounded battery. The relay 201 is so adjusted that when energized through its lower Winding only it pulls up only far enough to break the spring 214 from its resting contact, thereby opening a point in the release circuit of selector E, which will be explained hereinafter. The energization of relay 21 closes a circuit traceable from ground through spring 39 and its break contact, conductor 131, spring 67 and its make contact, conductor 133, through the Winding of relay 16 to grounded battery. Relay 16 energizes over the above traced circuit Without particular effect at this time.

The calling subscriber then manipulates the dial in accordance with the fourth digit of the called number, in this case assumed to be 5, thereby opening the circuit of relay 13 momentarily five times. Relay 13 transmits five impulses over a circuit traceable from round through the break contact and spring 33, through spring 35 and its break contact, spring 41 and its make contact, conductor 134, conductor 147, spring 69 and its make contact, spring 76 and its reak contact, conductor 160, wiper now in engagement with bank contact 237, conductor 267, through s ring 216 and its break contact, over conuctor 279, through series relay 202 and vertical magnet 205 in series to grounded battery. Magnet 205 energizes and deenergizes with the five impulses received over the above circuit to step the shaft of the intermediate selector E u five steps. Relay 202, being slow to release ecause of the copper collar on its core, energizes on the first impulse and remains ener ed during the series of five impulses. en the shaft of intermediate selector E is stepped up one step the ofi normal spring 219 closes, closing a circuit traceable from grounded release conductor 264, through spring 217 and its make contact, conductor 274, conductor 283, through spring 219 and its make contact, through the wmding of rotary interrupter relay 203 to grounded battery. Relay 203 energizes over the above circuit and at spring 220 prepares a point in the circuit of the rotary magnet 206. Relay 203, upon energizing, also closes a circuit from ground through spring 211 and its break contact, conductor 278, spring 221 and its make contact, through the rotary off normal spring 212 through the upper winding of relay 201, to the grounded release trunk conductor 264, thereb short circuiting the upper winding of switchlng relay 201 to definitely prevent its energizing at this time. When the relay 202 falls back after the fifth vertical impulse, it closes a circuit traceable from grounded re lease trlmk conductor 264, through spring 217 and its break contact, conductor 273, spring 220 and its make contact, through the winding of the rotary magnet 206 to grounded battery. Rotary magnet 206 energizes over the above traced circuit and at spring 27 2 opens the circuit of relay 203 shortly before the rotary armature completes its stroke The rotary armature rotates the shaft, bringing the wipers 242, 243 and 244 into contact with the first contact of the level. If that trunk happens to be busy at the moment, ground potential will be present upon the bank terminal 246 engaged by the test wiper 243, and a circuit will be complete from this grounded terminal 246, through test wiper 243, conductor 277, through spring 213 and its break contact, conductor 276, spring212 and its break contact, through conductor 274, through spring 222 and its break contact, conductor 283, off normal spring 219 and its make contact, through the winding of interrupter relay 203 to grounded battery. Relay 203 energizes over this circuit and again closes the circuit to the rotary magnet 206 which advances the wipers to the next trunk in the foregoing manner.- This procedure continues until an idle trunk is found in which case wiper 243 will not encounter a grounded contact. The short circuit of the upper windin of relay 201 is then removed and that re ay energizes over a circuit traceable from ground, over the release trunk conductor 264, through the upper winding of relay 201, through rotary ofi normal spring 212 and its break contact, through conductor 275 and rotary interrupter spring 22 and its break contact, conductor 283 and vertical ofl normal spring 219 and its make contact, through the wmdmg of relay 203 to grounded battery. The relay 201 then ulls up completely. Relay 203 is prevented om pulling up by the high resistance of the upper winding of rela 201. Relay'201, upon energizing, exten the ounded negative trunk; 261 through con uctor 272 and wiper 242 to the negative trunk of connector H. Relay 19, which has been held up by the ground at the break spring 210, is now held up over a circuit traceable from ground through the upper winding of switching relay 305, through spring 331' and its break contact, conductor 245, bank contact engaged by wiper 242, conductor 27 2, spring 210 and Its make contact, thence over the previously traced circuit to relay 19. It will be remembered that battery was fed to relay 19 through the resistance R, that resistance being of such a value that the relay 305will not energize with its upper winding alone in series with it. The resistance of the upper winding of relay 305 is of such a value as to permit a flow of suflicient current to hold relay 19 in its energized position in series with the high resistance R.

The energization of relay 201 also extends a grounded release conductor through spring 213 and its make contact, conductor 277, wiper 243, to the connector release trunk 246, through the upper winding of the connector magnet control relay 301 to grounded battery. The presence of ground upon the bank contact engaged by wiper 243 and to the contacts multlpled with it makes the connector H busy to ot er calls. Relay 301 when energized through its upper winding only pulls up just sufiiciently to break the spring 321 from its normal contact, but not sufliciently to break any of the other contacts. The energization of relay 201 further extends the trunk conductor 267 through spring 216 and its make contact, conductor 282, wiper 244, to the positive trunk conductor 247 of the connector H, thereby extending the previously traced impulse circuit to the ma ets of the connector. When the calling su scriber again operates his callin device in accordance with the fifth digit 0 the called number. I

the impulses delivered by the line relay 13 are transmitted over the above traced impulse circuit through spring 216 of the intermediate selector E and its make contact, through conductor 282, wiper 244 and the bank contact with which it is in engagement. conductor 247, spring 333 and its break contact, conductor 369, spring 329 and its break contact,

conductor 368 and thence over two parallel paths, one through conductor 367 to the winding of multiple relay 302 to grounded battery, and the other through spring 323 and its break contact, through the winding of the vertical magnet 307 to grounded battery. Relay 302 energizes on the first impulse and remains energized during-the impulsing because of the copper collar on its core. The vertical magnet 307 energizes upon each impulse to step the shaft vertically opposite the level in which the desired line is located. \Vhen the shaft takes its first step off normal springs 328 and 320 are operated in the well known manner to prepare circuits which will be hereinafter described. At the end of the series of vertical impulses relay 302 deenergizes, closing a circuit from grounded release trunk conductor 246, conductor 366, through ofit normal spring 328 and its make contact, spring 325 and its break contact, conductor 364 through the lower winding of relay 301 to grounded battery. Both the upper and the lower windings of relay 301 are now energized and the relay pulls up completely, locking itself through spring 322 and its make contact and the off normal spring 328 to the grounded release trunk conductor 366, independent of the springs of relay 302. Relay 301, upon energizing, operates spring 323 to transfer the impulsing circuit from the vertical magnet 307 to the rotary magnet 306. The subscriber then operates his calling device to transmit the last digit of the called number and the impulses delivered by line relay 13 are transmitted over the above traced impulse circuit to spring 323 and its make contact, and through rotary magnet- 306 to grounded battery, with the before traced parallel eircult through relay 302 to grounded battery. Relay 302 energizes and remains energized as before, and the rotary magnet 306 energizes in accordance with the digit sent to rotate the shaft to the contact terminals of the called line.

The operation of connector H at this point depends upon whether or not the called line is busy at the moment. Assume, first, that it is busy. There will be no ground potential upon the bank conductor 391 encountered by the test wiper 341, completing a circuit from grounded bank conductor 391, wiper 341, conductor 371, through spring 335 and its break contact. conductor 360, spring 324 and its make contact, through the winding of busy relay 303 to grounded battery, relay 302 remaining in an operated position long enough after the wipers come to rest to permit the energization of relay 303. When relay 303 energizes, at spring 327 it prepares a lockin r circuit for itself traceable from grounded release trunk conductor 246, conductor 366, through conductor 362, through spring 327 and its make contact, spring 324 and its break contact, through the winding of relay 303, thereby locking relay 303 independent of its original energizing circuit. Relay 303, upon energizing, also closes a circuit from busy tone machine through conductor 402, through spring 330 and its make contact, spring 333 and its break contact over the positive line conductor. 247, as previously traced back through intermediate selector E, positive Wiper of first selector E, through spring 76 and its break contact, through spring 69 and its make contact, through spring 58 and its make contact, through the condenser 138, through spring 53 and its break contact, through conductor 110, through spring 34 and its break contact, through condenser 9, thence over conductor 108, to the lower winding of line relay 13. The busy tone circuit is superimposed upon the calling line circuit through the lower winding of relay 13, making the busy tone audible to the calling subscriber. Upon hearing the busy tone the calling subscriber hangs up his receiver, thereby releasing relay 13 which restores to normal and opens the circuit of slow to release relay 15. Slow to release relay 15 restores after an interval and removes the ground from the release trunk conductor at spring 40. When ground is removed from the release trunk conductor relay 301 of connector H, which was locked up by the release trunk ground, restores, clos ing a circuit traceable from ground, through spring 321 and its break contact, off normal spring 320, through the release magnet 308 to grounded battery; The release magnet energizes and releases the connector in the well known manner. Removal of ground from the release trunk also restores relay 201 of selector E which was locked thereto and, upon restoring, it closes a circuit to the release magnet of E traceable from ground through spring 214 and its break contact, oif normal spring 215 and its make contact, through the release magnet 204 to grounded battery. Release magnet 204 energizes over this circuit to release the intermediate selector E in the well known manner. Relay 15, upon falling back, also closes a circuit traceable from ground, through spring 33 and its break contact, spring 35 and its break contact, spring 41 and its break contact, over two paths in parallel, the one through oil normal spring 36 and its make contact, through the winding of first selector release magnet 24 to grounded battery, and the other through conductor 120, through the oil normal spring 7 8 of the minor switch M, thence through the minor switch release magnet 28 to grounded battery, and also over conductor 118 through the release magnet 30 of minor switch M to grounded battery. Release magnets 24, 28 and 30 energize over the above traced circuit to release the switch mechanism of first selector E, the minor switch M, and the minor switch M, respectively. Removal of ground from the release trunk conductor 104 releases relay 10 of line switch C, which was locked thereto, said relay falling back to restore the individual line switch C to normal.

Assume now that the called line, upon which connector wipers 340, 341 and 342 are resting, is not busy at the time of the above traced call. Relay 302 remains energized for a brief interval after the last rotary impulse during which time the connector tests the contact 391 for the presence of ground. If no ground is present on this contact, nothing happens until the slow to release relay 302 restores, at which time a circuit for the cut-ott relay 312 of line switch C and the switch-through relay 304 of H is traceable from grounded release trunk conductor 246, through conductor 366, conductor 362, through the spring 327 and its break contact, through the upper winding of switch-through relay 304, conductor 361, spring 324 and its break contact, conductor 360, spring 335 and its break contact, wiper 341 in engagement with contact 391, through cut-off relay 312, through conductor 374, and spring 356 and its break contact, through the winding of motor magnet 314 to grounded battery. Relays 304 and 312 energize over the above traced circuit. Magnet 314 is prevented from energizing because of the high resistance of the relays in series with it. Relay 312 is prevented from attracting its armature all the way by means of the well known interlocking latch operated by line relay 313. Relay 312 energizes sufliciently to cause springs 346, 347 and 348 to break away from their resting contacts, but not sufliciently to cause them to make contact with theirmake contacts. Relay 304, upon energizing, closes a lockin circuit for itself traceable from grounded release trunk conductor 366 through spring 332 and its make contact, through the lower winding of relay 304 to grounded battery. Relay 304, upon operat ing spring 331, breaks the previously described holding circuit for the relay 19 and extends the negative line conductor 245 through the spring 331 and its make contact, conductor 370, wiper 340 in engagement with bank contact 390, through the negative line of the called station, and at spring 333 relay 304 extends the positive line 247 through spring 333 and its make contact, relay 337 and its break contact, wiper 342 in engagement with bank contact 392, to the positive called line. Relay 19 of the first selector E,

. upon restoring, closes the ringing current circuit traceable from the fifth ringing generator through the fifth bank contact of the minor switch M, through the wiper arm 85, to conductor 151, throu h spring 68 and its make contact, through t e lower winding of rin cut-ott relay 18, through spring 48 and its break contact, through conductor 129, through spring 54 and its break contact, through spring 58 and its break contact, conductor 148, through spring 69 and its make contact, through spring 76 and its break contact, thence over the positive line conductor 169, through wiper 90 in contact with bank contact 237, over positive line conductor 267 through spring 216 and its' make contact, conductor 282, through positive wiper 244 in contact with conductor 247, through spring and its make contact, spring 337 and its break contact, conductor 374, through wiper 342 in contact with bank terminal 392, over the positive line 381, through the hook switch, condenser, and bells of the telephone on line A which are connected to the positive line, to ground. The ringer associated with station A is tuned to respond to the fifth frequency of ringing current to notify the subscriber at A that he is being called.

The five frequencies of ringing current, se-

lected by the wiper 85 of minor switch M of the first selector E, are of the well known type superimposed upon grounded negative battery and associated with the mechanism arranged for interrupted ringing, and for supplying direct negative battery to the ringing lead during the silent period.

The bells of the called station A continue to ring intermittently until the subscriber answers his call. Relay 18 is so constructed with a copper sleeve and slug on its core that it will not energize on alternating current. When the called party answers his call by removing his receiver from the switchhook, a direct current path is completed, traceable from ground at spring 64 and its make contact, over conductor 126', through spring 47 and its break contact, conductor 123, through spring 51 and its break contact, through spring 55 and its break contact, conductor 141, through spring 61 and its make contact, through spring 70 and its break contact, over the positive line conductor 155, and the wiper 88 now in engagement with bank terminal 231, through conductor 261, through s ring 210 and its make contact, conductor 2 2, wiper 242 now in contact with conductor 245, through spring 331 and it's make contact, spring 334 and its break contact, conductor 370, wiper 340, bank terminal 390, conductor 376, the impulse springs of calling device of station-A through the transmitter, receiver and switchhook of telephone A, line conductor 381, bank terminal 392, wiper 342, conductor 374, spring 337 and its break contact, spring 333 and its make contact, conductor 247, wiper 244, conductor 282, spring 216 and its make contact, conductor 267, wiper 90, conductor 160, spring 76 and its of minor switch 'M in engagement with the fifth bank contact, through the interrupter and the generator to grounded negative battery. Relay 18 energizes over the above traced circuit, and at spring 52 closes a locking circuit for itself traceable from the grounded release trunk conductor 122, through spring 52 and its make contact, through the upper winding of relay 18 to grounded battery. Relay 18, upon energ zing, interrupts the above traced ringing C11- cult at springs 54 and 51, and connects the line of the called party through to the back bridge relay 14 over a circuit traced in part from ground through the lower winding of relay 14, through the spring 34 and its break contact, through conductor 110, through spring 54 and its make contact, thence over the previously traced circuit, through the intermediate selector E, connector H and called telephone A and back to the spring 51 which is now resting against its make contact over conductor 100, through spring 31 and its break contact, through the upper winding of relay 14 to grounded battery.

Relay 14, upon energizing, at spring 39 breaks the previously described circuit for relay 16, which restores after a brief interval. The energization of relay 14 at sprin 38 changes the holding circuit of the cut-o relay 10 of the line switch C, without material efiect at this time. Relay 14 furnishes talking battery to the transmitter of station A over the above traced circuit and the two parties may converse. The alternating current of conversation passes through condensers 9 and 9' to loop of the calling station A. It should be noted that in setting up the just described call several features were brought out which are different from the practices of the usual automatic system. The release trunk ground of this invention isextended from the first selector to each succeeding selector, and then to the connector and line switch of the called line, whereas in the usual automatic system the connector extends the release trunk ground back to hold up the preceding switches. In this invention the battery feed for both the calling and called telephones is-supplied from the first selector, rather than from the connector as in the usual automatic system. The first selec4 tor of this application controls the selection of and application of the ringing current to the called party. In setting up a call from station A to station A, we use the upper set of wipers 88, 89 and 90 of the first selector E, and the upper set of wipers of the connector H, the selection of the wipers being controlled by the wiper setting of the minor switch M.

It the subscriber at A was desirous of calling A whose number is assumed to be 314500, he would reach him over the switch train just described. In response to the first digit dialled the minor switch M would be stepped so that its wipers 86 and 87 are in contact with the third bank contact, in a manner hereinbefore described. With the wiper 87 resting on the third bank contact, no circuit is closed through it and therefore the upper set of wipers 88, 89 and 90 of the first selector would again be used. With the wiper 86 resting on the third 'set of bank contacts, the high resistance B would be excluded from the circuit of relay 19 of the first selector E and relay 305 of the connector,H, this circuit having been previously traced. Relay 305 is so adjusted that it will pull up in series with relay 19 over the above traced circuit when the high resistance R is excluded. When relay 305 pulls up, it looks itself to the release trunk at spring 336 and its make contact, and at springs 334, 335 and 337 disconnects the upper set of wipers and connects the trunks 245, 246 and 247 to the lower set of wipers 343, 344 and 345. The minor switch M is actuated in response to the second digitof the called number, in this case 1, to step its wipers 84 and 85 into engagement with the first bank contact, thereby selecting the first frequency of interrupted generator later to be applied to the called line to ring the bells of station A over the circuits hereinbefore described.- Station A is shown in Fig. 3 as a single party line, it being understood that it could be a multiparty line if desired. When the subscriber at A answers his call, the circuit of relay connector H to normal, as hereinbefore described.

In the telephone calls previously described, a switch train of three switches consisting of the first selector E, intermediate selector E, and connector H were employed. This invention is equally applicable to-a switch train consisting only of the first selector and the connector in which case the connectors would be available from the banks of the first selector. Fig. 2 shows such an arrangement with connectors H and H accessible from the banks of the first selector E. The connectors H and H are shown in detail in Fig. 3. By arranging Fig. 3 on Fig. 2 so that conductors 245, 246 and. 247 coincide with first selector bank contacts 232, 235, and 238, the circuits for such a connection when the upper set of wipers of the first selector are used may be traced. By arranging Fig.

3 so that conductors 245, 246 and 247 coincide with bank contacts 239, 240 and 241, the circuits may be traced for connection using the lower set of first selector wipers.

In originating such a call the subscriber at A will remove his receiver, seize and operate his individual line switch C, and seize the first selector E in the manner hereinbefore described. If the station desired were a station selected by the upper set of wipers of the connector H its number would be 45200, for example. The subscriber, upon hearing the dial tone, would operate his calling device to transmit the digit 4. Line relay .3 would be impulsed and would deliver impulses to the motor magnet 29 of the minor switch M to step the wipers 86 and 87 into engagement with the fourth bank contact. \Vhen the wiper 87 reaches its fourth bank :ontact a circuit is traceable from ground through Wiper 87 and the fourth bank contact, conductor 153, through the winding of relay 22 to grounded battery. Relay 22 energizes over the above traced circuit and at .prings 70, 72, and 76 disconnects the upper set of wipers 88, 89 and 90 of the first selector and connects in their place the lower set of wipers 91, 92 and 93. The minor switch M is stepped up in response to the second digit, in this case 5, to the fifth bank contact to 'prepare the ringing circuit which will be hereinafter described. The subscriber then operates his calling device in accordance with the third digit, and the line relay 13 transmits two impulses to the vertical magnet of the first selector E to step the shaft and wipers opposite the second level, and at the end of the impulses the rotary magnet 26 is energized to step the wipers into engagement with the first contact in that level in a manner hereinbefore described. If the first trunk of the lower bank level is busy, the wiper 92 will encounter the guarding ground potential and, in the manner previously described, will reenergize the rotary control relay 20 to step the wipers on the next trunk. This operation continues until an idle trunk is encountered, at which time relay 21 energizes to switch the calling line through to that trunk and to seize it for the instant call, in the well known manner. The first selector E is then connected directly to the connector H, whose circuit is shown at H on Fig. 3, and in response to the fourth and fifth digits of the called number the connector H steps up vertically and rotates to the terminals of the desired line, such as A in the manner hereinbefore described. The wiper 86 of the minor switchM is connected with the fourth bank contact, completing a circuit which is traceable from ground through the upper winding of relay 305, through spring 331 and its makecontact, conductor 245, bank contact 239, wiper 91, conductor 156, spring and its make contact,

wiper 61 and its make contact, spring 55 and its make contact, conductor 101, spring 32 and its break contact, conductor 102, through the winding of relay 19, conductor 145, through the high resistance B, through the wiper 86 in contact with the fourth bank terminal to grounded battery. Relay 19 is held energized over this circuit in a manner previously described, and because of the resistance of R relay 305 does not energize. The call from subscriber A to a subscriber such as A therefore, uses the lower set of wipers of the first selector E and the upper set of wipers of the connector H The called line is then tested as before and if found busty), busy tone is returned to the calling su scriber. If the called line is idle, it is seized, as before. 1

If, on the other hand, the calling subscriber at A desires to call a station reached through the lower bank of H whose number is assumed to be 51200, he will dial as the first digit a 5, setting the wipers 86 and 87 of the minor switch M in engagement with the fifth bank contact. The call will be extended as before. When the connector is seized, the wiper selecting relay 305 of H will be energized over the circuit just traced, which exeludes the high resistance R, for the reason that the wiper 86 is on the fifth bank contact. Relay 305, upon energizing, switches the incoming line from the upper set of wipers to the lower set of wipers, thereby extending the call to a station such as A when the connector is stepped up and around as before.

If the calling subscriber at A desires to call a subscriber reached by connector H through the upper banks and wipers, whose number would be 25200, the wipers 86 and 87 of the minor switch M will be stepped up two steps in response to the first digit dialled, in the manner hereinbefore described. The wiper 87, in engagement with the second bank contact, does not complete the circuit to wiper selecting relay 22, and the first selector E uses the upper set of wipers 88, 89 and 90. The second. digit operates the minor switch M to select the frequency of ringing current to be used, as before, and the third digit steps the shaft up opposite the desired level, in this case the second, from which position the sh aft is rotated in the well known manner until it encounters the bank contacts 232, 235 and 238, which are connected to the connector H When the connector H is seized the wiper selecting relay 305 therein does not energize because the high resistance R is included in its circuit, previously traced and including wiper 86 and relay 19. The call is completed in the well known manner to connect the calling station A with the desired station such as A in which call the first selector E and the connector H both use their upper set of wipers.

If the desired station were to be reached such as A, in this case, would use the u per through the lower bank connector H its number would be 31200, the first digit of whichseized for such a call, the wiper selecting reof switch M to grounded battery, excluding the high resistance R. The call to a station set ofwipers of the first selector E, an the lower set of wipers of the connector H.

f Special calls .In accordance with the well established practice, a manual operator'usually referred :to as the 0 o rator is available to assist a In the usual automatic system, the first selector'responds to the digit to step its shafts and wipers to the tenth bank level,

from which trunks lead to the operators po sition. In the present invention, the vertical motion of the shaft isresponsive to the third digit dialled. The minor switch M is responsive to the first digit. In calling the 0 operator, M is stepped ten steps, closing a circuit to step the shaft of E one step vertically. Trunks to the 0 operators position lead from the first level of the selector E, rather than from the tenth.

lVhen a calling subscriber removes his receiver the individual line switch 0 operates to select the first selector E in the'foregoing manner, and upon the transmission oft-he 0 digit by the calling device the ten impulses from the line relay 13 are delivered over the previously described circuit to the magnet 29 of the minor switch M, which advances its wipers ten steps, at the'completion of which a circuit is traceable from ground through wiper 87 in contact with the tenth bank contact, off normal spring 128 and its break contact, through the winding of vertical magnet 25. The vertical magnet energizes over the above traced circuit and advances the shaft one step vertically. When the shaft is advanced one step vertically the off normal springs operate in the well known manner, and the circuit to the vertical magnet is broken at ofi' normal spring 128. The operation of 011' normal spring 50 closes a circuit for relay 20, in the manner hereinbefore de-' scribed. The rotary magnet 26 is energized to rotate the wipers 88, 89 and 90'into engagement with the first contact in the first level. If that contact be busy the usual trunk hunting operation continues until an idle trunk is found, at which time the calling subscriber is connected through the Wipers 88, 89 and 90 to the 0 operators position over the bank contacts 252, 253 and 255.

Ringing current is supplied to signal the 0 operator through grounded negative battery and the ringing generator No. 1 through wiper 85 in engagement with its normal position contact, through the conductor 151, spring 68 and its make contact, throu h the lower winding of relay 18, through spring 48 andits break contact, over conductor 129, through spring 54 and its break contact, spring 58 and its break contact, spring 69 and its make contact, spring 76 and its break contact, conductor 160, the wiper 90 in engage ment with contact 255, trunk 255, through the signalling apparatus at the 0 operators position, trunk 263, wiper 88, conductor 155 sprin 70 and its break contact, spring 61 and its make contact, conductor 141, spring 55 and its break contact, spring 51 and its break contact, conductor 123, spring 47 and its break contact, conductor 126, spring 64 and its make contact to ground. When the 0 operator answers the call, relay 18 operates over the above traced circuit inthe manner hereinbefore described to connect the lines of the 0 operators position to the back bridge relay 14, from which relay battery is fed in the usual manner. The O operator extends the call or answers the inquiry, and

upon completion of the conversation the calling party A replaces his receiver and the 0 operator removes her plug from the circuit, at which time the line relay 13 deenergizes and opens the circuit of release relay 15, which removes the ground from the release trunk, and completes the circuit through through the release magnet to restore the line switch C and the first selector E to normal in the usual manner.

In order to guard against the possibility of wrong numbers due to a premature operation of the dial, I have provided an arrangement for releasing the switches and returning them to normal, should the subscriber send a preliminary impulse after the switch E is seized. Responsive to that impulse, relay 13 deenergizes momentarily as before to send a ground impulse to the motor magnet 29 of minor switch M as before. Responsive to that impulse, wiper 87 is stepped to its first bank contact closing a circuit through wiper 87 and its first bank contact, over conductor 153 through relay 22 to battery, energizing relay 22. Relay 22 closes a circuit from grounded release conductor 112, through springs and 79 to the winding of release magnet 30 of minor switch M. Magnet 30 releases M, whereupon wiper 87 breaks the above circuit of relay 22, which restores, restoring the switch to normal ready forthe reception of directive impulses from the subscribers calling device.

It should be noted that the off-normal springs of minor switch M are adjusted so that springs 79' are not operated when the wipers 8687 are advanced but one step, but are operated on the second step.

Inasmuch as a part of the lines in this system may be multi-party lines, provision must be made so that a subscriber on one of these lines may call another subscriber on the same line. It is the well established practice in automatic systems, to make use of the socalled reverting call or ring-back switch for this purpose, such a switch being described in detail in the above referred to patent. On the telephones of a party line, there will appear a card listing the directory numbers of the other parties on that line, and giving directions as to what number to call in order to reach that party from that particular telephone. In the presentsystem, the so-called reverting call switch is reached by dialling the digits 610, after which two digits are dialled to operate the reverting call switch to set up the desired combination of rings.

When the subscriber at A removes his re ceiver to make such a call, he seizes his line switch C, which operates to select the first selector E in the well known manner. He then operates his calling device to transmit the digit 6, causing the line relay 13 to transmit six impulses to the motor magnet 29 of the minor switch M, thereby stepping the wip ers 86. and 87 into engagement with the sixth bank contact. He again operates his calling device to transmit the digit 1 and the impulses from the line relay are delivered to the minor switch motor magnet 27 of the minor switch M, as has been before described, stepping the' wipers 84 and 85 of the switch into engagement with the first bank contact, thereby selecting the first frequency of ringing current. In response to the third digit, the 0 in this case, ten impulses are transmitted from the line relay 13 to the vertical magnet 25 of the first selector E, which magnet operates to step the shaft and wipers ten vertical steps. lVhen the shaft is stepped into the tenth step, the tenth level post springs 139 operate to prepare a switching through circuit. The selector is rotated into the tenth level and an idle trunk therein hunted and secured in the usual manner, the switching relay 21 energizing at the completion of this process to connect the calling line to that trunk. The cnergization of relay 21 closes a circuit traceable from ground through spring and its make contact, conductor 144, 0 level post spring 139 and its make contact, through two paths in parallel, one path through the winding of the relay 18 to grounded battery, and the other path over conductor 103,through the winding of relay 12, conductor 107, throu h the sixth bank contact and the wiper 86 of t e minor switch M to grounded battery. Ring cut-off relay 18 energizes over this circuit, and at springs 54 and 51 removes ringing generator from the wipers of the first selector E and prepares a pointin the calling line circuit. Switching relay 12 also energizes over the above traced circuit and, at springs 31' and 34' and their break contacts, disconnects the calling line from the line relay 13 and extends it through the reverting call switch line relay, free from attachments, a circuit being traced in part from ground, through the lower winding of the line relay of the reverting call switch, this relay not being shown, over the trunk conductor 266, bank contact 236 now engaged by the wiper 90, over the conductor 1.60, through spring 7 6 and its break contact, through spring 69 and its make contact, over conductor 148, through spring 58 and its break contact, spring 54 and its make contact, conductor 110, spring 34 and its make contact, conductor 106, through the wiper 82 of the line switch C, spring 5 and its make contact, calling line 1, through the hookswitch, receiver, transmitter and dial of the calling station A to calling line 2, through spring 3 and its make contact, the wiper 80 of the line switch C in engagement with trunk conductor 105, through spring 31 and its make contact, the conductor 100, through spring 51 and its make contact, spring 55 and its break contact, conductor 141, through spring 61 and its make contact, spring 7 0 and its break contact, conductor 155, the wiper 88 now in engagement with bank contact 230, through trunk 260, through the upper winding of the line relay of the reverting call switch, to grounded battery. Relay 13 deenergizes and at spring 35 opens a circuit of the release relay 15. The release relay of the reverting call switch is energized and returns the ground over conductor 261', which is picked up by wiper 89 now inengagement with contact 233 and returned over conductor 157, through spring 72 and its break contact, spring 63 and its make contact, through the relasetrunk conductor 122, thereby holding the first selector E and the primary lineswitch C in energized position. The fourth and fifth digits transmitted by the calling subscriber are directed to the setting up of the switch mechanism of the reverting call switch R0, the line going through the first selector E without any attachments. Upon completion of the transmission of the digits of the called number the subscriber'at A replaces his receiver whereon the reverting call switch RC rings first the bells of the called party and then the bell of the calling party, continuing with this alternate ringing until the called party answers. The calling subscriber noting that his hell no longer rings removes his receiver and the two parties may then converse. Upon completion of the conversation the parties replace their receivers interrupting the circuit of the line relay of the reverting call switch RC, which ,releases the release relay and removes the ground from the release trunk conductor 261, whereupon the first selector E, the rotary line switch .0 and the reverting call switch RC are returned to normal in the well lmown manner.

Having thus described my invention, what I consider new and desire to have protected by Letters Patent is pointed out in the appended claims.

What is claimed is:

1. In an automatic telephone system, calling and called lines, means comprising switches controllable from said callilelg line for extending a connection to said call line, said switches bein arranged in one lar group of switches irectly accessible to said calling line and a plurality of smaller groups of secondary switches accessible to said calling line through the banks of the switches of said first group, means in the switches of said first group operable by the calling subscriber to select a grou of saidsecondary switches, means in said switch for automatically selecting an idle one of the switches of said selected group, and means in the first said switch operable by the calling subscriber for selecting a frequency of ringing current and ligcontrolling its application to the called 2. In an automatic telephone system, a calling and a called line, means comprising switches controllable by said calling line for extending a connection to a called line, said switches being arranged in one main group of primary switches directly accessible to the calling station with a plurality of groups and sub-groups of secondary switches accessible from the banks of said primary switches, means in said primary switches responsive to the first digit dialled by said calling subscriber for selecting a group of secondary switches, means responsive to the second digit dialled for selecting the frequency of ringing current to be used and for preparing circuits to control its application, means responsive to the third digit dialled for selecting a sub-group of secondary switches, and means in said primary switches automatically operable to select an idle one of said switches of the selected sub-group.

3. In an'automatic telephone system, calling and called lines, means controlled by the calling subscriber to extend a connection to the called line comprising switches arranged in one large group of primary switches and a plurality of main and sub-groups of secondary switches accessible from the banks of said primary switches, an auxiliary switch associated with said primary switches responsive to the first digit dialled to select the main roup of secondary switches, a second auxiliary switch associated with said primary switch responsive to the second digit dialled to select the frequency of ringing current to be used and to prepare circuits for controlling its application, means in said primary switch responsive to the third digit dialled for selecting i a sub-group of said secondary primary and secondary'switches each pr0- vid ed with a plurality of sets of-wipers, means comprisin an auxiliary switch responsive to the first digit dialled for selecting the set of.

wipers of the primary switch and for preparing circuitsto select theset of wipers of the secondary switch, and means'for thereafter operating said primary switch to extend a connection to a selected one of said secondary switches.

5. In a telephone system, calling and called lines, a series of automatic switches for establishing a connection from a calling to a called line, means for operating said switches from the calling line in response to the di 'ts of a called number, the first switch of said series responding to the first two digits of a called number before moving its wipers or connecting with the succeeding switch in the series.

6. In an automatic telephone system, a calling line, an automatic switch accessible to said line. other automatic switches accessible to the first switch, each automatic switch having a plurality of sets of wipers, an auxiliary step-by-step switch associated with said first automatic switch, means for operating said auxiliary switch to select a set of wipers of .said first automatic switch, means for there after operating said first automatic switch to select and extend a talking connection to one of said other automatic switches through the selected wiper set, and means in said selected switch operable through said auxiliary switch over one side of said talking connec tion to select a set of wipers thereof.

7. In an automatic telephone system, an automatic switch having a plurality of wipers, a plurality of groups of switches accessible to said automatic switch,'each of said switches having a plurality of sets of wipers, an auxiliary switch associated with said first automatic switch, means for variably operating said auxiliary switch and for subsequently operating said first automatic switch, the setting of the auxiliary switch determining the set of wipers to be used by the first and succeeding automatic switches.

8. In an automatic telephone system,'subscribers lines, a group of selectors available to said lines, a plurality of groups of connectors available to said selectors, said selectors and connectors each having two sets of wipers, means. in the selector responsive to a digit dialled for selecting the combination of wipers to be used, means in. the selector res onsive to another digit dialled for selecting the frequency of ringing current to be used, means in said'selector responsive to the third digit dialled for selecting the combination of nectors to be used, and means in said selector automatically operable at the end of the last said digit for selecting an idle connector of the selected group.

9. In an automatic telephone system, subscribers lines, a group of selectors available to said lines, a plurality of groups of connectors available to said selectors, said selectors and connectors each having two sets of wipers, meansin the selector responsive to a digit dialled for selecting the combination of wipers to be used, and means in the selector responsive to another digit dialled for selecting the frequency of ringing current to be used.

10. In an automatic telephone exchange, a calling and a called line, means consisting of a selector and a connector operable from said calling line to select a called line, means in said selector for selecting and applying ringing current to said called line, a ring cut-oil relay in said selector operable by the response of the called part to remove ringing current from the called inc, and means in said selector controlled by the operation of said relay for furnishing talking current to both of said lines and for connecting them together telephonically.

11. In a telephone system, a calling line, an automatic switch accessible to said line, said switch having access to a plurality of groups of trunks, one of said groups leading to an operators position, a first and second auxiliary switch and a motor magnet associated with said automatic switch, means on said calling line for transmitting directive digits to said automatic switches, circuit means arranged so that the first auxiliary switch responds to the first digit received, the second auxiliary switch to the second digit received and the motor magnet to the third digit, and another circuit arrangement operable by a particular setting of the first auxiliaryswitch for directly operating said motor magnet to connect said calling line with said operators position.

12. In a telephone system, calling and called lines, a first selector, other switches, said first selector having means for extending a talking circuit through said other switches to a called subscriber, ringing equipment in said first selector, means in each of said other switches for maintaining a ground connection to one side of said circuit to prevent the operation of said equipment, and means for removing ground from said circuit when connection is made with the called line to start the operation of said equipment.

13. In a telephone system, means for es- I tablishing a connection including a first selector switch directly accessible to a calling line, and otlier switches accessible thereto, said switches operated in response to the digits of a called number, a plurality of sources 0; alternating current, means individual to said first selector for selecting one of said sources of alternating current, and means for applying the selected source over said connection.

14. In a telephone system, means for establishing a connection including a first selector responsive to the first digit of a called number, and other switches accessible thereto, said switches operated in' response to the digits of a called number, a plurality of sources of alternating current, an auxiliary switch associated with the selector for selecting one of said sources of alternating current, and means for applying the selected source over said connection.

15. In an automatic telephone system, a group of automatic switches, a plurality of groups of secondary automatic switches accessible to the first said switches, a plurality of groups of subscribers lines accessible from said second switches, said groups containing both multi-party and single-party lines, means in the switches of said first group for controlling the switches of said second group to select a particular line, and means in said first switches for signaling a particular party on the selected line.

16. In an automatic telephone system, a group of automatic switches, a plurality of groups of secondary automatic switches accessible to the first said switches, a lurality of groups of subscribers lines accessi le from said second switches, said groups containing both multi-party and single-party lines,

means in the switches of said first group for controlling the switches of said second group to select a particular line, a source of alternating current of many frequencies, means in said first switches comprising an auxiliary switch for selecting one of said frequencies, and means for selectively applying said frequency to the selected line.

17. In an automatic telephone system, a group of automatic switches, a plurality of groups of secondary automatic switches accessible to the first said switches, a lurality of groups of subscribers lines accessi le from said second switches, said groups containing both multi-party and single-party lines, means in the switches of said first group for controlling the switches of said second group to select a particular line, a source of alternating current of many frequencies, means in said first switches comprising anauxiliary switch for selecting-one of said frequencies, and means comprising a relay for applying said selected frequency to either one of the two sides of the selected line.

trolled by the subscriber on the calling line.

to operate said selector to seize one of the other switches, circuits controlled by said line relay for repeating impulses direct to the vertical and rotary magnets of said other switch and a two step relay partially energized over a conductor separate from the talking circuit, and fully energized over a local circuit completed after the last impulse of a series to switch said impulsing circuit from one magnet to the other.

20. In a telephone system, calling and called lines, a selector switch accessible to the calling line, other switches accessible tosaid selector, said selector operated from the calling line to seize said other switches and extend a connection to a called line, a line relay in said selector, vertical and rotary magnets for each of said switches, and circuits for all of said vertical magnets and one of said rotary magnets directly controlled by the springs of said line relay.

21. In a telephone system, a selector switch. a connector switch, a line relay for the selector, means controlled thereby for operating the selector to extend circuits to the connector, primary and secondary operating magnets for the connector, a circuit for each magnet including one of the extended circuits directly controlled by said line relay, and means, controlled over another of the extended circuits, for switchingthe first extended circuit from one magnet to the other.

22. In a telephone system, a calling line and a called line, an automatic switch accessible to said calling line and controlled by the subscriber thereon for extending a connection in the direction of said called line, a second automatic switch accessible from the first, a relay in said second switch, said relay operable in two distinct steps, means in said first switch for partially energizing said relay to operate it through its first step, and means in saidsecond switch for thereafter further energizing said relay to operate it through its second step.

23. In a telephone system, an automatic switch operable in two distinct motions to select a telephone number, said switch controlled by a relay operable in two distinct steps, a release magnet and two motor magnets in said switch, said relay operating to its first step when the switch is seized to disconnect said release magnet and to connect the first of said motor magnets, and means for thereafter operating said relay to its second step to extend a circuit to the second of said motor magnets.

24. In a telephone system, a selector switch, other switches accessible thereto, means for controlling said selector to extend a talking circuit successively through said switches to a called line, a relay in said selector for controlling the talking circuit therein, a circuit for said relay including a part of the talking circult and successively extended to include a branch in each switch, and means for controlling said circuit to operate said relay 1when the connection is completed to a called 25. In a telephone system, a calling line, an automatic switch accessible to said line. said switch having two sets of wipers, means in said switch responsive to two digits dialled from the calling line for selecting the wiper set and frequency of ringing current respectively, an operators position accessible from the banks of said switch, means operable from a particular setting of said first means for operating said switch to connect the calling line with said operators position.

26. In a telephone system, a calling line, an 'automat-1c switch accessible to' said line, said switch having access to a plurality of groups of trunks, one of said groups leading to an operators position, an auxiliary switch associated with said automatic switch to assist in selecting a group of said trunks, means on said calling line for transmitting directive digits to said switches, said auxiliary switch responsive to the first digit, means operable by said auxiliary switch for translating said digit into a lesser digit to operate said automatic switch to connect said calling line with said operators position.

' 27. In a telephone system, a calling line, an automatic switch accessible to said line, an opxerators position accessible from said switc and means in said switch responsive to the dialling of a digit for translating said digit to a lesser digit to operate said switch to connect the calling line to said operators position.

28. In a telephone system, a calling and a called line, selectors available to said calling line, a plurality of groups of other switches accesible to said selectors, means for operating one of said selectors to select one of said other switches, a two-step relay in said latter switch, means for partially energizing said relay to operate it to its first step when the switch is seized, and means for thereafter fully energizing said relay to operate it to its second step.

29. In a telephone system, a calling and a called line, selectors available to said calling line, a plurality of groups of other switches accessible to said selectors, means for operating one of saidselectors to select one of said other switches, a two-step relay in said latter switch, means for partially energizing said relay to operate it to its first step when the switch is seized, a plurality of connectors accessible from said second switch, means for operating said second switch to select an idle one of said connectors, and means for preventing a further energization of said relay durin the selection of said connector.

30. n a telephone system, a calling and a called line, selectors available to said calling line, a plurality of groups of other switches accessible to said selectors, means for operating said selectors to select one of said other switches, a two-step relay in said latter switch, means for operating said relay to its first step when the switch is seized, a plurality of connectors accessible from said second switch, means "for operating said second switch to select an idle one of said connectors, means for preventing further operation of said relay during the selection of said connector, and means for thereafter operating saidrelay to its second step.

31. In a telephone system, a trunk line terminating in a selector switch, wipers on said switch, other trunk lines accessible through said wipers, primary, secondary and release magnets in said selector, primary and secondary control relays and a two step switching relay in said selector and circuit connections between said first trunk, relays and magnets through which are exercised all the functions incidental to positioning said wipers on a desired one of said second trunk lines, connecting said first and second trunks together, and subsequently breaking said connection and restoring said selector to normal. 32. In a telephone system, a trunk line terminating in a selector switch, wipers on said switch, other trunk lines accessible through said wipers, primary and secondary motor magnets in said selector, control relays in said selector comprising only a primary control relay, a secondary control relay and a switching relay, and connecting means through which said relays are operated to control said magnets to connect said first trunk through said wipers to a selected one of said second trunks.

33. In a telephone system, a trunk line terminating in a selector switch, wipers on said switch, other trunk lines accessible through said wipers, primary and secondary motor magnets in said selector, control relays in said selector comprising only a primary control relay, a secondary control relay and a switching relay, connecting means through which said relays are operated to control said magnets to connect said first trunk through said wipers to a selected one of said second trunks, and releasing means operated by said switching relay in its normal position to restore said selector to normal.

34. In a telephone system, a switch having wipers, a plurality of contacts to which said wipers have access and through which connections are established, three motor magnets in said switch and control means comprising three relays and the associated circuit connections for operating said magnets to control said wipers.

35. In a telephone system, a selector switch and a connector switch accessible thereto, a plurality of wiper sets on each of said switches, ringing equipment in said selector, a line relay in said selector, means for operating said relay to prepare a means for determining the wiper set to be used by said selector 'and connector, to prepare circuits to and from said ringing equipment and then to operate said selector into connection with said connector, means in. said connector for projecting a high resistance ground over one conductor of said connection said prepared means cooperating therewith to select a wiper set of said connector, lines accessible to said connector, means for repeating impulses from said line relay to said connector to operate it into connection with one of said lines, means responsive to the establishment of said connection to apply said prepared ringing equipment to said line.

36. In a telephone system, a selector switch and a connector switch accessible thereto, a plurality of wiper sets on each of said switches, ringing equipment in said selector, a line relay in said selector, means for operating said relay to prepare'a means for determining the wiper set to be used by said selector and connector, to prepare circuits to and from said ringing equipment and then to operate said selector into connection with said connector, means in said connector for projecting a high resistance ground over one conductor of said connection said prepared means cooperating therewith to select a wiper set of said connector, lines accessible to said connector, means for repeating impulses from said line relay to said connector to operate it into connection with one of said lines, means responsive to the establishment of said connection to remove said high resistance ground from said conductor, and means responsive thereto to apply said prepared ringing equipment to said line.

37. In a telephone system, a selector switch and a connector switch accessible thereto, a plurality of wipers on each of said switches, ringing equipment in said selector, a line relay in said selector, means for operating said relay to prepare a means for determining the wiper set to be used by said selector and connector, to prepare circuits to and from said ringing equipment and then to operate said selector into connection with said connector, means in said connector for projecting a high resistance ground over one conductor of said connection said prepared means cooperating therewithto select a wip'er set of said connector, lines accessible to said connector, means for repeating impulses from said hne relay to said connector to operate it into connection with one of said lines, a rela in said connector energized in response to t e establishment. of said connection to remove said high resistance ground from said conductor and means responsive thereto to apply said prepared ringing equipment to said line.

38. In a telephone system, a selector switch and a connector switch accessible thereto, a plurality of wiper sets on each of said switches, ringing equipment in said selector, a line relay in said selector, means for operating said relay to prepare a means for determining the wiper set to be used by said selector and connector, to prepare circuits to and from said ringing equipment and then to operate said selector into connection with said connector, a relay in said connector through a winding of which ground is applied to one conductor of said connection said prepared means cooperating therewith to select a wi er set of said connector, means for repeatlng impulses from said line relay to said connector to operate it into connection with one of said lines, means responsive to the establishment of said connection to apply said prepared ringing equipment to said line.

39. In a telephone system, a selector switch and a connector switchaccessible thereto, a plurality of wipers on said switches, wiper selecting equipment in said selector, ringing equipment in said selector, a line relay in said selector, means for operating said line relay to operate said wiper selecting equipment, means responsive to a reoperation of said line relay for preparing circuits to and from said ringing equipment, and means responsive to a further operation of said line relay for operating said selector into connection with said connector, a marginal wiper selecting relay in said connector, a control relay in said selector, a circuit for said relays including one conductor of said connection in series with those relays and with either direct battery or battery through a high resistance, said marginal relay energizing or not energizing over said circuit to select one or the other of said wiper sets of said connector, and said control rela energizing over said circuit to disable sai prepared ringing equipment, means for repeating further impulses from said line relay to said connector to operate it, lines accessible to said connector, and means in said connector responsive to the establishment ofa connection over one of said lines, for opening said series circuit to permit said control relay to drop back to apply said tion. 7

40. In a telephone system, a switch train prepared ringing equipment to said connec-' comprising a first selector, an intermediate selectorjaccessible thereto, and a connector accessiblet'o said intermediate selector, a plurality of wiper sets on said first selector and said connector ringing equipment. in said first selector, a ine relay in said first selector, means for operating said line relay to determine the wiper sets to be used by said selector and said connector, and for preparing circuits to and from said ringing equipment, and fort-hen operating said selector to establish a connection with said intermediate selector, a control relay in said first selector, means in said intermediate selector for com- -pleting a. vcircuit over one conductor of said established connection through said control relay andsaid wiper determining means to operate said relay, means in said intermediate selector responsive to further operation of the said line relay for operating it to es tablish a connection with said connector, means in said intermediate selector responsive to the establishment of said connection for opening said circuit and substituting therefor a'circuit completed in said connector, means in said connector controlled over said'circuit for selecting the wiper sets thereof in accordance with the determination made in said first selector, lines accessible to said connector, means in said connector for establishing a connection with one of said lines, means responsive to the establishment of said connector for opening said extended circuit to permit said control relay to restore, and means responsive to the restoration of said control relay for applying said prepared ringing equipment to said connection.

41. In a telephone system, a selector switch and a connector switch accessible thereto, a plurality of wiper sets on each of said switches, a line relay in said selector, means of operating said relay to select the wiper set of said selector and connector and for then reoperating it to operate said selector to establish a connection to said connector, means in said selector for projecting busy potential over one conductor of said connection to mark said connector engaged, means in said selector for projecting a wiper selecting potential over asecond conductor of: said connection to prepare the circuits of the selected wiper set of said connection, and means for repeatin impulses generated by a further reoperation of said line relay over a third conductor of said connection to said connector to operate it. v

42. In a telephone system,a selector switch and a connector switch accessible thereto, a plurality of wiper sets on each of said switches, a line relay in said selector, means of operating said relay to select the wiper set of said selector and connector and for then reoperating it to operate said selector to establish a connection to said connector, means .in saidselector for projecting busy

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