US1075430A - Telephone-exchange system. - Google Patents

Description

APPLICATION IiLED JULYZS, 1910.

118 v M hm nu 0m e n a V V. m m F l lillH P. R. MQBERTY.

. TELEPHONE'EXGHANGE YSTEM.

\ APPLIGATION FILED JULYZS, 1910.

Patented Oct. 14, 1913.

F. R. MoBERTY. TELEPHONE EXCHANGE SYSTEM. APPLIOATIOH FILED JULY 23, 1910.

5 SHEETS-SHEBT 3.

7 Patented Oct. 14, 1913.

F. R. MOBERTY. TELEPHONE EXCHANGE SYSTEM.

APPLICATION FILED JULY 23, 1910.

Patented Oct. 14, 1913.

5 SHEETS-SHEET 4.

H Imll -l P. R. MQBERTY.

TELEPHONE EXCHANGE SYSTEM.

APPLICATION FILED JULY 23,.1910

Patented Oct. 14, 19 13 5 SHEETS-SHBBT 5.

llllllllll mm UNITED STATES PATENT ()FFICE.

FRANK R. MCBERTY, OF NEW ROCHELLE. NEW YORK, ASSIGNOR TO WESTERN ELEC- TRIO COMPANY, OF NEW YORK, Y., A CORPORATION OF ILLINOIS.

TELEPHONE-EXCHANGE SYSTEM.

T0 (t7! whom it may concern: I

Be it known that I, FRANK R. MoBnnrr,

citizen of the United States, residing at New Rochelle, in the county of \Vestchester and State of New York, have invented a certain new and useful Improvement .in Telephone-Ilxchange Systems, of which the following is a full, clear, concise, and exact description. This invention relates to telephone exchange systems of the type in which automatic switches orselectors are used for the interconnection of telephone lines, and it has for its objectin general to provide improved means associated with the selectors thereof for governing their operation.

More particularly the invention-has fcr its object the provision of an improved arrangement of apparatus associated with the final switches orselectors whereby various kinds of lines, such as ordinary and prit'ate branch exchange lines, may be intercon nected.

In telephone systems of the kind to which this invention particularly relates. the lines of any private branch exchange may be c0nnected to successive terminals in a row on the final switch. the test terminals thereof being connected differently from the test terminals of ordinary lines andthe test circuit associated with the final switch "being provided with responsive means adapted to' discriminate betweenthe different classcsot lines. 'l he apparatus should also be arranged in such a manner that it all. of the lines lea ding to any private branch exchange to which connection is desired. are busy. the response of the finalswitch, upon connection being' made with the terminals of the line following the last line of the group. will be the same as or similar to the response thereof when connection is made with the terminals of an ordinary 'line.

With such an arrangement the final switch,

will. it connection is made to any of the group of private branch exchange lines. test such line. making onnection thereto it it is not busy but passing on to the terminals of the next line if it is busy. If all the private branch exchange lines of the group are. found busy. the switch will move on to the terminals of the line following the last private branch exchange line oi the group and will th n respond in the same manner as though the connection had been Specification 'of Letters Patent.

K made to a busy ordinary line, that is to say-r it' will set into operation the busy back signaling apparatus to notify the operator or the calling subscriber that the desired connection cannot be secured;

One'feature of the present invention contemplates improved means of selectively signaling the several substations of party lines, this means being. combined and operating in harmony with the means for dis criminating between ordinary lines and. private branch exchange lines.

Another feature of the, intention contemplates improved mcans for controlling the busy back signaling apparatus to indicate that a line or group of lines to which connection may be desired 1s busy.

These features of the invention and others to be described and pointed out in the claims, although capable of separate embodiment in telephone exchange systems, are, in the particular system herein set forth Patented Oct. 1 4, 191 .3; Application filed July 23. 1910. SerialNo. 573,517.

combined in one system and embodied in the apparatus of a'- single final switch,

whereby such switch may perform the sev eral functions required in an orderly and efiicient manner.

An arrangement of the apparatusat the j final switch or selector in accordance with the above mentioned features of invention may be briefly set truth as follows: All of the test terminals of private branch exchange lines. including the last terminal in each group. are connected to a source or sources of current of the same character and the test terminals of all ordinary subscribers lines are connected to a source or sourrl-es ot'r-urrent of a different character from that of the private ranch exchange. lines. The test circuit of the final switch or selector is provided with electro-responsive means. preferably in the form of a r'elay controlling the selector-mechanismv to cause hunting of the brushes over the terminals of private branch exchange lines in 100 succ ssion. and if allot thelines represent ed thereby are busy to cause the-brushes to pass beyond the group of private branch exchange terminals and to maketemporary.

connection to the line terminals next suc- 10 ceeding the terminals of said group, 'theselector mechanism being thereupon caused to give a busv back signal to the operator: or waiting subscriber. The temporary coli- Dentin}; is made without disturbing in the 11o 45 nals of two of the sets of terminals of each leastthe'circuit conditions already existing.

at the terminals of that line, which may be busy or idle, the mechanism in either case I ed. Preferably t-he sources of current of the terminals of private branch exchange lines two kinds of lines are characterized by a difference in polarity, that is to say, thetest may be connected tonegativebattery and the test-terminalls of ordinary linesto posi-' tive 'lzia'ttery. This enables the testing apparatus associated with the selector or final switch to disqriminate between the two kinds of lines. f y r i The connection to party lines and the means for selectively signaling over such lines are provided for in the system herein described in a. manner which completely 'harmonizes with the means for discriminating between ordinary and private branch exchange lines. These-party. lines mayhav e foursubstations each, the signal bells at two of the stations being connected from one side of the line to ground. and those of the other two stations being connected from the otherfside'of the line to ground; this being an arrangement well known in the art. Connections of these lines to the terminals of final switchmeehanisms are made in such a manner that each substation of a party .line has its individual set of terminals. Each such set may be located at any point in 'the system which corresponds to the number assigned to that substation. The, arrangement in this respect is similar to the well known jack per station arrangement in manual switchboards, The termifour-party line are connected to the line wires in reverseorder to thatof the terminals of, the othertwo sets; and the test terminals. of one of each of said two sets are connected to a source of current of the opposite polarity to that to which the test terminals of the other two sets are connected. Thus the polaritybf' the test terminals enables the testing apparatus of the final-switch to determine which of two ringing' generators (positive and negative pulsating) shall be connected in the line cir c uit; while the reverse connection of the line wires enables the selected generator to be applied to one side or the other of the telephone line. The arrangement is therefore one 1n which the selector may be caused to make connection with a set of terminals and upon. making such connection to connect a ringing generator in circuit so as to operate the bell of the'desircd substation without operating thebells at the other su b-' stations ofthe line. The testing apparatus at the finer swi ch in the system of them: ivention is thus required to distinguish between two kinds of lines only those in which the test terminals are connected to positive battery and those in which the test terminals are connected to negative battery.

The presence of positive battery lIlOzl-IIS an ordinary line or either one of two of the substations of a party line, while the pres ence of negative battery means a special or private branch exchange l1ne-"or either one of the other two substations of a party line.

It will only be necessary in considering the operation of the finalswitch while hunting over private branchiexclian-ge terminals and testing at the line terminalsv next succeeding, to refer to ordinary and special or pri vate branch exchange lines. It will tend to avoid confusion-if the party lines are dis regarded with respect to such operation. It

will be understood, however, that the line terminals next succeeding the group 01 pro vate branch exchange terminals may be the terminals of an ordinary line or those of a party line which have positive battery connected to the test terminals thereof. It will also be understood that when connection is made to a party line and at a test terminal thereof which is connected to negative battery, the operation of the final switch'will be the same as that which follows the connection to a private branch exchange line; that is, if the line is busy the brushes of the selector will be caused to advance to the line terminals next succeeding the terminals of the line desired just as the brushes are caused to hunt overterminals of busy private branch exchange lines. quirement in the connection of the various kinds of lines to the terminals at the final switch is that there shall be a positive test terminal next succeeding each negative test terminal of a party line and next succeeding each row of negative test'termiuals of a group of private branch exchange lines,

The method employed of controlling the operation of the final switch mechanism to discriminate between private branch exchange lines and. ordinary lines involves an arrangement of apparatus, whereby a double test follows each selecting operation. This double test is provided for by maintaining the test circuit closed during two perlods, one preferably closely following the other, means being provided to'change the mode of control so that the selector mechanism is adapted with like line conditions to respond in a different manner under the influence of the second test than under that of the first.

The only 1e If the line selected is an ordinary subscribers line, the first test definitely determines the subsequent operation of the selector, but if the line selected is one of a group of private branch exchange lines, the second test instead of the first determines the subsequent operation. The period of the sec- 0nd test would in such case include the time in which the. selector is hunting over the terminals of the group of private branch exchange lines. In case all of the lines of that groupare busy, the test circuit finally becomes closed (still during the second test period) to a line test terminal next succeed.-

ing the test terminals of the group of pri-,

vate branch exchange lines, and the operation of the selector, resulting from this do sure of the test circuit, must necessarily be different from that which follows the first closure ofI-the test circuit to the terminal of a selected ordinary subscribers line.

Considering the operation more in detail, the selector mechanism responds upon-the first test, when an ordinary line is selected to stop the selector if that line is idle, with the brushes in contact with the terminals of that linefand to make. the connections reuuired to signal the subscriber Wanted; but

if such line is'busy, the selector will under the influence of the first test cause a busy back signal to be given to the operator or t aiting subscriber. On the other handIthe selectormechanism will respond under the second test, when the line selected is one of a group of private branch exchangelines, to advance the brushes to the terminals of the first idle line of the group, or in case all of the lines of that group are busy to advance the brushes to theterminals of the next succeeding line, whereupon, whether that line is idle ,or busy, the busy signal will be given.

The testing means for securing the method lot operation hereinbefore referred to may comprise a relay in the test circuit, which relay is. responsive to current of a distinctive character and which controls the local circuit of a locking relay, which in turn determines the operation of the selector mechanism. And the mode of control-of the local circuit of the locking relay by the relay in thetest c'rcuit may be changed by a switching devic in the local circuit in such a manner that if the relay does not respond in the first test period, it will be irresponsive to the test relay in the second test period when it meets; that condition at the test terminal which would have caused it to respond during thefirst test period. This switching dehas been found desirable to have one of these relays responsive to current of a given dimotion, and the othei to current of given strength. The first mentiruicd relay may kinds of lines, such as ordinary lines and private branch exchange lines, while the sec ondrelay may serve to discriminate between lines which are busy and those which are idle. The first mentioned relay may also serve as it does in the system herein de: scribed to determine the kind of generator to be connected for selectively signaling-the subscribers of party lines. V hen the test circuit is equipped with two test relays, the thirdv or locking relay is made responsive under the first test only upon energization of both'of the test relays and responsive un- 'der the second test upon the energization of the current strength relay alone, but not upon the energization of both test relays, the local circuit of the-locking relay-being shifted between the two test periods to change the mode ,of control thereof for the purpose heretofore stated. The locking relay may serve to close a shunt path which is of low resistance in the test circuit, which path includes a second winding of the current strength relay, the closing of this shunt path causing the line to whichconnection has been made to test busy thereafter to other selectors. The main function of this lockin: relay, however, is to control the operation of the selector mechanism. It does this when energized, in part by closing a circuit for the motor magnet of a sequence switch, the sequence switch being thereupon caused to advance to the talking position. It furthermore serves as a means of testing the condition of the distant controllingapparatus, so that under certain circumstances, if the call has not been properly or completely transmitted, or if the operator should open the controlling circuit to Wipe out? the connection which she had starteththis locking relay would respond by releasing its armature and cause the selector mechanism to be returned to normal condition. To provide for this testing operation,"thc local circuit of the locking relay is preferably connected to a switch spring: of the sequence switch mcclmnis'l'n. this spring: playing between contacts, one of which 15 connected in 'circuitwith contact of a line relay in the controlling circuit. If the controlling); cir- 12o curt 1s; open at any of the times when the locking relay circuit is thus switched. the

locking relay will be released with the result stated, that is. the return of the mechanism to normal.

. hfurther feature of the present inven .tion contemplates special means employed for automatically operating the signal bell of the called sul'iscribrr and for actuating switching mer'j-hanism upon the response of-133 saidsubscriber to disconnect the calling generator and to complete the talking cir-' cuit. According to this feature of the in vention, an electro-responsive device or relay arranged to be energized by current from the ringing generator when the subscriber responds, is provided with two windingrone in the line circuit and one in a local circuit, this local circuit including a normally open contact of said re ay and a con trolling device for said switch mechanism. This switch mechanism is preferably a part of the sequence switch and it may be arranged not only to disconnect the generator and complete the talking circuit, but also to disconnect theele'ctro-responsive device or relay from the line circuit. in order that the line may be free from connections which would in any way interfere with the efficient trans'mission of voice currents. The local circuit referred to is a locking circuit which thereby insures the operation of the sequence switch upon a momentary closure of the line circuit. The switching mechanism, however, quickly opens the locking circuit again and releases and disconnects the ringing control relay.

The system of apparatus and circuits herein described embodies certain features of invention which are not claimed in this application. These are made the subjectmatter of other applications for patent by me, of which may be nientionedthe following: Serial No. 516,769, filed September 8, 1909. Serial No. 515,933, filed September2, 1909. Serial No. 531,369,'filed December 4, 1909. Serial No. 573,516, filed July 23, 1910. Serial No. 533,928, filed December 18, 1909.

There is shown in the drawings which accompany this application, a single selector or'switch mechanism and the apparatus associated therewith and entering into the control thereof. The selector shown is the final switch, the last one of a series of similar switches which operate in succession in an actual exchange to interconnect. telephone lines. c r

In the drawingsFigure 1 shows the circuits and apparatus which are directly associated with the final switch mechanism; Fig. 2 shows the mechanism and circuits of a trunk line and a suitable controlling apparatus which may be associated and connected with the final switch of Fig. 1 by means of a trunk line; Fig. 3 shows the circuits of various kinds of subscribers lines to which connection may be made by the final switch of Fig. These three figures when placed side by side--Fig. 2 to the left and Fig. I) to the right of Fig. 1form a complete circuit diagram of the final switch! the apparatus entering into the operation and control thcrmf and the subscrilaers lines adapted to be connected thereby. Figs.

several sets in multiple.

4-, 5, G and 7 show in detail the structure of a sequence switch mechanism by which the circuits of the selector, the trunk line and the controlling apparatus in each case are governed. Figs. 4c and 5 are front and side clevations respectively of the sequence switch, while Fig. 6 is a view in cross sect-ion on line G-t3 of Fig. 5, and Fig. 7 is a view in cross section online 7-7 of Fig. 5.

In the form of automatic switch shown in Fig. 1, the switch carriage or movable element is provided with a number of sets of multiple brushes, any particular set of which may be selected for service and the switch carriage then advanced over a series of sets. of line terminals until the selected brushes are brought into engagement ,with the terminals of a desired'line. The switch carriage or brush carrying member is of the rotary type, the frame 21 of which is mounted upon a central standard .or shaft 22. At

the outer end of the frame a number of sets of contact brushes 28,241, 25.are pivotally mounted upon but insulated from a rod 26, and from each other, in position to sweep over sets of line terminals 27, 28, 25). The brushes have inwardly extending arms 30,

' bearingagainst which, one for each brush,

are springs 31. Latches 32 one for each set of three brushes, are pivotally mountedupon a rod 33 and arranged to normally hold the brushes from being rocked outwardly into line with the stationary terminals. Bearing against the inner ends of the latches are springs 34 which hold the latches firmly against a stop rod 36. This stop rod 36 serves to prevent the. latches from being moved forward too far after the brushes have been released. A stop bar 35 serves to limit the outward movement of the brushes when the latches are withdrawn. The latches 32 and stop bar are of insulating material so that the circuits con nected with the brushes will not be crossed thereby. The springs 31 make electrical connection with the brushes; they are of sheet metal and form the teeth of combs which connect corresponding brushes in the terminals 37, 38 and 39am provided for the circuit connections to the springs and brushes. As the brush. carriage is rotated to cause the brushes to sweep over the fixed terminals, the latches first pass bya tripping device or brush selector, by which any desired set of brushes may be released and caused to swing outwardly. This tripping device comprises a shaft -Ll-0 provided with radially extending fingers 41 arranged spirally about the surface of the shaft. This shaft is adapted by mechanism, to be presently described, to be rotated so as to bring the fingers one after another into the line of travel of the several latches on the brush carriage. Only one set of brushes Suitable wire clip then the brush carriage is rotated. In passingrthe outward edge of this latch strikes the end of the finger, allowing one set of three brushes to be released. Continued vmovement of the brush carriage brings theselected set ()flHllSllQS into engagement with the rows of stationary terminals in the same level therewith these brushes trailing over the. terminals and making contact therewith in passing. The brush carriage is finally caused to stop. with the selected brushes in contact with some one set of stationary terminals. The other brushes, not being released. are held out of contact with the terminals over which they pass. A further movement of the brush carriage in the same direction'ot' rotation will carry the brushes over -a restoring roller 69, which may he pivoted to the frame and which engages the free ends of the released set, causing them to be pushed back into their normal latched position. After making a full revolution, the brush carriage is brought to rest 111 its normal position again. The brush selector and the brush carriage of this switch mechanism are arranged to be moved one following the other by suitablemotor mechanisms which will impart to "each acontinuous movement. In order thatthe .succ positions taken by 4 each movable member may he stepperlott or measured, eachis provided with airinterrupter device adapted to make and break a contact in the controlling I circuit as the moving member passes the several positions at which it may be desired to cause said'member to stop. Thisinten rupter device for the brush carriage comprises a jpair' of contact springs '48, 49 secured to tl-ieshaft but insulated from said shaft nd from each other. \The outer ends of these springs are engageeh'hy inwardly extending arms 44 and 4501 a pair of levers 42, 43. whi h are pivotally mounted upon the rod 26. These levers 42 and 4?, are insl'llated from the. springs 4 and 49 by small insulating buttons at the ends of the arms 44 and 45, but are uninsulated from the rod 26 which is connected to ground through the frame of the selector n iechanism. In the movem nt of the brush carriage a roller 31 on the free end of the lever 42- engages the teeth 53 of a am plate 50. then-tiller: engaging each tooth as thebrushes are traversing the space l'ietween the successive terminals and droppinginto the notches between the t eth as the brushes are cen-' trally located in contact withsa'id terminals. \Vhile therollcr 51 is riding over the teeth .of the plate 3! the curved end of the lever is in talgagement with the smooth edge 52 ol that plate. A relative movement of the levers 42 and 43 is thus obtained by their engagement with the edges of plate and this movement is, therefore, independent of slight variations in the radial distance between the plate and the axis of movement of the brash carriage. By this construction the duration of contact between theinter'rupter springs 48 and 49 is made uniform in the movement of the brush carriage, each make and each break corresponding to a particular position of the brushes with'respect to the terminals.

.In the normal position oi the switch mech anism as shown in Fig. l, the levers 42 and 43 rest in a recess 47 ct' a. normal stop plate 46: The entering edge of this plate is covered with insulating material in order to prevent the free ends of the levers 42 and from making"electrical contact with the plate 46 before reaching the .tull normal position in which the ends of the levers drop into the recess 47. 1

The interrupter for the. brush selector comprises an arm 50 pivoted to the "frame at 57, engaging at its free end a toothed wheel or cam '58 which rotates with the shaft 40. This arm 56 is adapted in the rotation of the shaft to engage two contacts 59 and 60. These contacts may he springs. the free ends only of which are shown in the drawing. "in its normal position the tree end of the arm 56 lies in a notch of the cam.

whiehis deep enough to insure an open connection with contact 55). When the shaft is/away from its normal position. however,

connection is made contiumisly with contact The connection with contact (30 is intermittent. this contact being made when the arm 56 is lifted by each tooth of the cam. "There are as many teeth on the cam as there are lingers 41 on the spindle 40 and therefore as many as there are sets of brushes.

The motor mechanism for causing rotation of the brush carriage comprises an annular iron Friction disk 61 flexibly m unted at the lower end of thespindle 22. an electromagnet 32 which may be fixed in any suitablemanner to the frame, and a .coustantly rotating shatt i2) carrying an iron lriving roller (34. The disk Cl. roller (it and that part of the shaft or: which extendsthr ough the center of the elta-tromagnet o2 *t'oii'n the magnetic circuit ct the electromagnet '12. When therefore current is passed through the winding of the magnet, the roller 34 attracts the disk (31 andciauses the. latter to rotate by frictional contact therewith. holding eleetron'iagnet (35 having clisl: c1 and roller 6%.

rietl by the spindle 40. An cicctrouiugnet 68 controls the engu'g'i-nucnt or disk and roller 67 in the some nnintnerthat the electromagnct 62 controls the engagement of These devices are in fact electromngnetic clutches, one to cause movement of the brush carriage and the other to cause movement of the brush selector. i

The complete selector switch mechanism is not shown in the drawing, but the elements thereof appear their proper relation to one another so as to make clear the manner iniwhich the mechanism operates to'inten connect lines. 'llhere maybe as many sets of brushes and stationery terminals as desired. may, as a. hole, have ten sets of three brushes each and two hundred sets of fixed terirninuls zurungecl in. ten levels of twenty sets each. For simplicity in the cliogrcui there. are shown only two sets of brushes,

the 8th and 9th counting from. the top down, and 511%. sets of stationary terminals in two levels corresponding to the two sets. of brushes shown.

in Fig. 1, and those at the controller and at the distant e'nil oi? the trunk line, shown in Fig. 2, ure preferably governed in each case by a sequence switch. in general the function at the sequence switch is to establish inc definite order it successive stages of the operation Various circuits rcquired to brlnglntoservice YRIIOUS ClQKUCQS or ports in probe)? sequence. The sequence switch consists in itselements of a movable switch operating member, a number of circi'iit changers actuated in sequence as said member is nioveclfrom one position to on other, an elec'tromagnct, and motor mechw nisni operated or controlled by said magnetadvencing soul movable member.

each position to which it movable member of the-sequence switch is advanced, a circuit or set bi circuits is established by which a given operation of the device uncler control is made possible, and at the some time another circuit is placed in a condition whereby the motor ma it 01''. the sequenceswitch may be subsequentl actuated so that the sequence switch Will then be automatically advanced to the next position,'nntil :1 new set of circuits is established, bringing about u new operation or electrical condition of the dx, vice devices under control, and so on.

In the form of sequence switch. shown in Figs. to 7 inclusive, the movable member is n yertice'i rotary shaft 76 cer'ryinge num-' of switch operating cams 77, said shaft being arranged to be driven by power up plied through the agency of an electromagnetic clutch. The constantly driven power '38 carries a friction driving clisl; 79 which is oriented to be (brown into engagi- F cxumplgthe switch mechanisnr The circuits at the final switch, as shownveglg e oi the 023,111 85.

ore-13o ment- Wii h a friction roller-'80, carried upon the shaft 76,, by the notion of a. clutch m agnet 81. The roller 80 and-the disk 79 are of iron, and the motor magnet 81 is adapted when excited to mngnetize said roller '80 which serves as a. rotary pole piece forsaiti mugnct-; whereby the driving disk 79 is at tracteti into engagement with said roller, therotetion of-the shaftYG thus continuing as long as the motor magnet 81 remains excited. f r

The crime "Z'I carriecl by the rotary shaft 76 are arrnngecl to operate switch springs 82, forcing seicl springs into engagement With outer contacts 83, or allowing them to engage their alternate inner contacts 84 ac-.

cording .tothe positions of said cams. As'

' until the next intended stopping position of the rotary element is fully reached. As"

shown. in Fig. 7, the cam 85 for operating the local" switch is adapted to he en-' gnged by a coin roller 86' carried by a pivotecl switch lever A spring 88 is arranged to act upon said pivoted lever 87 so as to press the cam roller 86 against the W hen the roller S6 rides upon a. tooth or high part of the cam 85, said lever;8l closes a contact 89 which" controls the local-circuit for the motor magnet. The teeth of the cam 85 hztveinclined edges, so that the com roller 86, after riding over the point of a tooth, is forced (IOWII the opposite slope by the action of the spring 88, and this tends to pushsgz'tinst the com to continue the rotation thereof until the roller 86 reaches the'bottom of the followbut the local circuit will be maintained for the motor magnet througl'l the contact 89 closed by the-cam 85, and the rotary element will thus continue to advance until the cam roller 86 reaches the bottom of the next notch of the com 85.

device, the circuit will The switch springs of the sequence switches do not appear intheir actual an rangement in the. circuit diagrams, but are so located as to give a clear arrangement of the circuits; and the operating camsare not shown. In Fig. 1 the clutch or motor mechanism 81, its driving disk T9and friction roller 80 are shown in their structural arrangement, while the contacts 101, 102, 111 to 114, inclusive, and 201 to 227, inclusive, operated thereby, are shown merely in their proper circuit positions without regard to structural arrangement. The positions of the rotary elements of each sequence switch in which any of its contacts, except contact 101, are closed, are indicated by numbers placed adjacent to such contacts; each contact being open in all positions except those indicated by reference numbers. For example, contact 102 is closed in the 2nd, 5th, 12th,"13th and 14th positions as indicated.

- by the numbers 2, 5, 12, 13 and 14 placed adjacent thereto. In the case of the special contact 101 operated by cam 85, the numbers are placed on the opposite side of the switch lever from its contact anvil and indicate the positions in which the contact is opened, said contact being closed continuously while the rotary element of the sequence switch is in; transit between the positions indicated. It will therefore be understood that tl e'speojla-l contact 101 is closed continuously between positions 1 and 2, 2 and 5, 5 and 9, 9 and 11, 11 and 12, 12 and 13, 13 and 14, 14 and 16 and 16 and 1. eighteen positions of the sequence switch and the cams thereof will be caused to niake one complete revolution in passing from normal through the eighteen positions and hack to normal again. i

The sequence switch spring which operates contacts 221 and 222 is of slightly different construction from the others, inthat it is adapted to make either of said contacts before the other is broken. It may be called The reason for this a. continuity switch. continuity operation of these contacts'will appear presently.

In addition to the sequence switch mechanism there are associated with the final switch of Fig. 1 the following relays: 1,023 is a line relay, the operation of which controlled by current in the circuit of the trunk line 104.105leat'1ing to the controlling apparatus of Fig. 2; 23!) is a battery control relay,

one of the functions of which is-to control the connection of battery 109 in the circuit of the trunk line 228 is a su )ervisor relav which is included .in that part of the trunk line which leads from battery 229 through .\'indings 107 of a repeating-coil 108 .to the brushes 23 and 21 of the switch mechanism; 230 is a ringing control relay. its function being to cause the operation of the sequence switch upon the response of the called sub- Thcre may he say scriber to a ringing signal; 231, 232 and 23 s are test relays, their main function being to discriminate between the different kinds and different conditions of subscribers lines to which connection may be made by the switch mechanism. Relay 231 is of comparatively high resistance and is polarized. It is responsive to positive current only flowing from the test brush 25. Relay 232 is responsive only to current of a given strength, it has two windings 236 and 237, the former heing of somewhat higher resistance than t e latter. The winding 236, is in a branch of the test circuit WlllCllriilClUdGS .the wind ing of relay 231, while winding'237 is in a branch adapted to shunt relay 231 and winding 236. Relay 233 is in a local circuit controlled byrelays -31 and 23 Contact 220 of the sequence switch controls the connection of aninterrupter 238, the function of which is to give a busyback signal to the waiting subscriber or.

certain other conmrctions to a middlepoii'it in the battery which may be called the neutral terminal of the battery.

The polarity test relay 231 is arranged to control the application of negative and positive pulsating current generators 234- and 235 to the connected line, a resistance 250 being inter 'iosed in the ringing-circuit to'regulate the How of current therein. A resistance 2:37 is iuchulcd in a lo al circuit controlled by sequen e switch contact 227. A condenser 250 is placed in shunt of the line relay 103 in order to eliminate the in'ipedance of said relay in the talking circuit. 7

The following are given as suitable resistance values for the various relays'and clectromagnct windings shown in Fig. 1: line relay 103, 1200 ohms; battery control relay 239, 1000 ohms; supervisory relay 228,

25 ohmsprcferably with a non-inductive shunt; ringing control relay 230, each winding 250 ohms; polarity test relay 231, 250 ohms: marginal current test relay 232,100 ohms-in winding 236 and 50 ohms in winding 237; motor magnet 81 of the sequence switch 500 ohms; and the motor magnets 02 and 68 of the switch mechanism and holding magnet 65. each 500 ohms. The resistances 250 and 257 may each be of 300 ohms; the battery 109 may be of 48 volts potential, the two parts thereof on either side of the neutral point being of 2-t volts, and battery 225) may be of 24 volts. These resistances and voltage may be widely varied in practice, the

values given being merely those whichhave proved suitable in practice.

Referrin to Fig. 2, it will be noted that the trunk line conductors 104, 10:) are represented as extending through three sets of tant or controlling end includeswindings 321 of a repeating coil 320 and a relay 323. The cooperating Windings'322 of this repeating coil may be connected in circuit with a battery 319 and through suitable mechanism to a calling telephone liner Associated with the trunk line and controlling the connections thereof isa sequence switch mechanism similar. to that associated with the final switch. There are shown for this sequence switch a motormagnet 381, its dr1ving disk'379 and friction roller 380 and contacts 301 to311 inclusive. Contact 301 is a special contact operating similarly to contact 101 of the final switch; it is arranged to be closed while the sequence switch is be-' ing moved between the positions 1 andnG, 6 and 10, 10 and 15, and 15 and 1, as indicated. In addition to the sequence switch contacts there are shown in the circuit contacts 313 and 314 which may be manipulated in any desired manner to assist in the control of the sequence switch operation. Relay 323 has a back contact 315 leading to sequence switch contact 311 and a front contact, 316 controlling the operation of a lamp signal 318 which is included in a local circuit with battery 319. Battery 312 serves as the source of current for various circuits associated with the trunk line controlling apparatus.

A suitable arrangement of controlling apparatus is shown in Fig. 2. This apparatus may comprisea plurality of counting relays operating the counting relays in succession and a cut-off relay adapted, when its circuit is closedsimultaneously at one of the. counting relays and at the particular switch or key which .is operated, to open the con trolling circuit and stop the movement of the selector. The circuits of the controlling apparatus may be governed by a sequence switch, such a sequence switch being represented in Fig. 2 by a motor magnet 481, its driving disk 479 and roller 480 and contacts 401 to 408 inclusive. Contact 401 isa special contact" opcrating similarly to contact 101 or the selector sequence switch. It may be arranged as indicated to maintain the circuit of the motor magnet 481" closed continuously while passing fromi position 11 p to position 13 and then from position 13 i to ition 11. Only so inuch of the com; tro ling apparatusis shown as enters nit-a.

the operation'of the final switch mechanism.

-In a large system employing a. series of selector switches operated in succession, the sequence switch for the contro ler would be provided with various'other contacts than those shown and the contacts shown would be arranged to be closed in other positions than those indicated. In the operationiof the final switch alone, however, but two comprises relays 441 to 448 inclusive; these v are adapted when energized to close contacts 461 to 468 inclusive, each of which is inseries with .one of the switches orkeys 451. to,

458 inclusive and. also with one of the switches or keys 471 to 478' inclusive. Any

relays when closed conjointly'witha corresponding key' or switch is adapted to com- 'plete a circuit for a cut-ofi relay 423 and a sequence switch controlling relay 425. A second or auxiliary series ,0f counting relays 411 to 418 inclusive is arranged to cooperate with the main counting relays; these are adapted under t c control of the stepping relay 424 to be rought into'cirwit and energized in alternate succession with the main counting relays. 'The two series of counting relays ma be extended in' an obvious manner to inc ude any desired number. i l

' As will presentl Yap earzthe ste ping re- 7 lay 424 is adapte to "jenergi'z and d6- energi'zed intermittently while the selector mechanisms of the final switch are being advanced from position to position. Upon the 'and a plurality of controlling switches oiiflfirst cncrgization of stepping relay 424, 11

keys, together with a stepping relay for? v of sequence'sw'itch contact .405," winding of circuit is completed from battery 312 byway auxiliary counting relay 411, contact428 of main cou.nting relay 441 and'front cont tact 432 of the steppingrelay 424, where-' upon relay 411 is energized and; closes a locking circuit for ltSWlIldlIig by way of contact 429. Relay 411 when energized also closes contact 430 which places the; first. main counting relay 441 in positioir to be operated by the stepping relay when it is deene'rgized, a circuit being then completed from battery 312 through sequence switch contact 404, relay 441, contact 433 of the "sec ondauxiliary. counting relay 412, saidpcontact 430 of the firstiauxiliary cohntingrelay 411 and back contact 431 of the steppin relay. Relay 441 is thereupon energize and it, like the relay 411, closes a locking circuit for its winding by way of contact 461.. As heretofore stated, contact 461'would one of these contacts of the main counting I also be in circuit with relays 423 and 425 if the corr'esponding key or switch 451 was closed at this time, and the energization of relay 441 would in such case cause the cutin the 11th position at this time and it would therefore be advanced to the 13th position. In passing the 12th position, the

a locking circuits for the countingrelays 441 cuit before the circuit is opened at back 0011- and 411 would be opened at sequence switch contacts 404 and'405 and the circuit of the stepping relay 424 would also be opened in the 12th position at sequence switch contact 403 but closed again in position 13. Se quence switch contact 406, which was closed in the 11th position, is openin the l3th, while contact 407, which was open in the 11th, is now closed in the 13th. The two strings of counting relays are therefore in position for operation again under the control of the stepping relay 424 and the second series of keys or switches 471, 478. "It will be noted that the number of impulses of current for intermittently operating the stepping relay 424 which may flow over the trunk cirtact 422 of the cut-off relay depends upon the particular key which is actuated. If, for exam le, key 453 had been actuated, the circuit 0 the cut-oii' relay 423 would not be closed until main counting relay 443 had been energized, and this would happen after three impulses of current in the trunk line circuit.

It has been stated heretofore that the switch mechanism shown in Fig". 2 was arran 'ed to make connection with. various kinds of subscribers lines. In In". 3-the circuits of such lines are shown in d agrammatic form. An ordinary single party line is indicated by line wires 501 leading to a substation 502. A four-party line is indicated by conductors 503 leading to four substations 504 to 507 inclusive. The signal bells at the substations of this party line are of high resistance and are connected in a well known way two from one side and two from the other side of the line to round,

one bell on each side of the line being re spo-nsive to positive pulsating ringing current and the other bell on each side of the line being responsive to negative pulsating ringing current. A private branch exchangeis indicated at 508, this exchange being connected with the switch mechanisms at the main exchange by lines 509, 510 and 511, terminating at suitable springjack switches 535 and drop signals 530. A plug may be used to extend the circuit. of any one of said. lines 500, 510, 511 to any one of the lhcal stiitions at the private branch exchange 508. The ordinary single party line and the private branch exchange lines are connected to apparatus at the main exchange accord-- ing to a well known arrangement. each line Y being provided with a springjack 534, a line relay 531, a lamp signal and a cut-01f rclay-533, the latter being connected in a third wire connected to a test terminal 29 of the final switch mechanisu'i. reason of the usual multiple wiring, this test terminal and the line wire terminals would be connected also to oth'ertest terminals of other switches having access to such lines. It will be noted that the test wire' of the ordinary single party line is connected through the cutoii' relay 533-to the. positive pole of battery 109, while 'the test wires of the private branch exchange lines are connected through cutoff relays to the negative pole of thatbattery. It is this difference in the manner .of connecting the test terminals of these lines which enables the testing apparatus of the final switch mechanism to distinguislrbetween ordinary lines and private branch exchange lines.

A somewhat dilferent arrangement of circuits is provided for party lines. It has already been stated that each substation of a party line has its own setof terminals at the final switch. The test terminals for two of the substations of the party line 503 are connected together by one test wire which made in reverse order -to those of the line terminals for the other two substationsthis in order that the ringing generators may, in each instance, be connected by way of the same brush 28 for ringing the bells at every one of the four substations. Either cut- 0H relay 514 or 517 is adapted to open the normal circuit of the line conductor 503 to a line relay 518 and to ground. It con-. nection is made to a test terminal leading to either one of these cut-ofi' relays, a local circuit will be closed by that relay which will reduce the potential at the test terminals leading to the other cut-01f relay. This is accomplished without causing the energization of said other cut-off relay. The local circuit referred to includes a second winding of said other cut-oft relay. Let it be considered, for example, that connection is the L "Jade to the test terminal leading to wind ingfilfi or" cut-oil relay 51 The energizatic-n of this relay will open the circuit of the line at contacts 519 and 520, one on one side t the line and one on the other, and will fit the same time close contact 52l, completin local circuit from the neutral point of the battery 109 by way ofnormal contact of cut-on relay 5.17, said contact 521, winding 516 of relay 517, and winding 515 ofthc same relay to the ground pole of the battery. Current flows in winding 516 in this circuit an opposite direction to that of the current flowing in winding. 515 and relay 517 is not energized. In the same manner, it connection should be made terminal leading'to winding 51%; lay 517, this relay would open the li cult at contacts 523 and and close circuit at contact 524: which would w ndings 512 and 513 of relay 51%, The istances of these windings which have been *ound suitable in practice are as follows: fi indings 512 and 515, 100 ohms each, and windings 513 and 516, 50 ohms each. The number of turns is approximately the same in the two windings of each cut-off relay. It will thus be seen that the local circuit o-, d by either cut-oft relay through the tings of the other will materially change the potential at the test terminals connected to said other cut-oft relay, It may be stated l re that the windings of the cnt-offrelays of the ordinary subscribers and private ch exchange lines may also be of 1 oach. in: several sets of conductors leading to aft in S are individual to the sevsubscri.

here of ordinary and party lines 1 to the several lines of a private branch Mango and may be considered as conrow at the final switch mechanism o i The 2nd, lth, 9th and 10th sets coz'mtiog" from the top down, connected telephone line 503 and reprellos. 7'1, '73, 78 and 79. onnected to the ordinary 1, subscriber No. 72; the c csent other ordinary single is, subscribers bloc. 70 and '77, the ucrei'or being not shown in the IIOWQVQE", the 5th, 6th and 7th connectcl to the privat branch Ell) mind 5.11 re; cctively, The third with of each oi concuctors is connected to one of the lcrmiamls 29 at the final switch. It will he noted that each test terminal of a party telephone line which is connected to dive pole of the battery 10:) has a cinipal beyond. it in the line of travel brush 25, which is connected. to do of the tutti-(Ty; also that i souls of the three private to the nod to successive sets of terminals in a branch exchange lines are arranged in succession in a row on the final switch and are followed by a test terminal leading to positive battery. The test brush of a final switch will accordingly be caused to make contact with-negative test terminals of party lines and of private branch ex change lines, and if the party line pr the group of private branch exchange lines is busy, the test brush will be caused immediately thereafter to make contact with a positive test terminal of some other line, whereupon the signal willv be given that such party line, or such group of private branch exchange lines is busy.

Before describing in detail the operation of the system of'Figs. 1, 2 and 3, it may be stated that the'several positions which the sequence switches assume are characterized. in each instance by a particular condition or operation of the mechanism governed thereby; and these positions may c0nveniently be defined by such conditions or operations. Thus the selector sequence switch positions are as follows: 1, normal; 2, that in which the brush selector is advancin and transmitting impulses over the truni line; 5, that in which-th advancing for line selection and is transmitting impulses; 6 and 7, those in which the test is made for which a retest is made for negative line and in which a further advance of the switch carriage may occur for private branch exchange hunting; 10, test of trunk line for wipe-out operation; 11, that in which the sequence switch may run to busy back position; 12, the ringing position, 13, the talkingposition; 14, the busy back position; and 16, that in which the selector is caused to return to normal. Similarly the positions of the trunk line sequence switch may be defined as follows: 1, normal; 6, that in "which the controller is connected to the trunk line for brush and. line selection; 10, the talking position; 11 and 15, positions in which the selector may be caused to return 'to normal; and 15, also that in which the trunk line sequence switch awaits the return of the selector.

The controller sequence switch positions are: 11, brush selection, and 13, line selection.

The opcration of the system will be described under several headings as follows:

1. Selection of non-busy ordinary line.

' 2. Selection of non-busy private branch exchange line. i

3. Selection of busy ordinary line.

e brush carriage is positive line; 9, that In 4-. Selection ofbusy private branch exchange line, and

Returnof mcch knock-down operations.

It will be understood that the operation of the switch which anism on wipe-out or occurs in the selection 13o tire battery, as are those of an ordinary as that which occurs in the selection of an ordinary line, or as that which occurs in the selection of a private branch exchange line. This is because the test "terminals of party line'snbscrib ers are connected either .to posiline, or to negative batter-V as are those of a private branch exchange lines.

Selection of non-busy ordinary Zine- Let itjbe assumed that the terminals of an ordinary line (subscriber No. 72) to which connection is desired, are located in the 8th level from the top of the finalswitch, and in the 3rd range counting from left to right in the direction of the travel of the brushes. The operator, having received instructions from acalling subscriber to establish this connection, will first close switches 458 and 473, the first (458) to control the impulses for brush selection and the second (47 3) to control the impulses for line terminal selection. Switch 313 may I then be operated, closing a circuit for motor magnet 381 and starting the operation of the trunk line sequence switch, which thereupon advances from thefirst or normal position to the 6th position in which. contacts 303, 304 and 305 are closed. A. circuit is then completed over the trunk line as follows 5, battery 109, back contact 260 or the battery control relay 239,

winding of relay 103, sequence switch contact 211, conductor 104, the trunk line sequeues-switch contact 304, the controller sequence switch contact" 403, winding of stepping relay 424, back contact 422 of the cut-off relay 423, the trunk linesequence switch contact 303, co-nductor'105, sequence switch contact 212 and back contact'26l of the battery control relay'239 tothe ground pole of the battery 109. This circuit causes the energization of thestepping relay 424 at the controller and of the line relay 103 at the final switch. The energization of'the stepping relay 424 completes a' 'circuit heretofore traced forauxiliary 'coiinting relay I 411, one-half step being thus taken 'in the movement of the controlling apparatus. The energization of line relay, 103 causes a circuit to be completed forthe motor mag- 'net 81 of the selector sequence switch Fig.

1) by way of sequence switchcontact 203 and the front contact 124 of the line relay 103. The selector sequence switch thereupon advances to the 2nd position.

In the second position of the selector sequence. switch a circuit is closed for the motor magnet 68 of the brush selector by way. of sequence switch contact 204 and the front-contact 124 of the line relay, whereupon the shaft 40 is rotated, causing an intermittent closing of its interrupter arm and contact 00. This contact is closed once for each position in which the shaft 40' is adapt-ed to be placed for selecting a set of gized" a circuit is completed for the cutoff relay 423 and the sequence switch controlling relay 425 by way of sequence switch contact 400, key 453 and front contact 408 of counting relay 44S. Relay 423 thereupon opens the trunk line'circuit at its back contact 422 and the brush selector upon reaching its 8th position from normal is caused to stop in that position, the circuit of the motor magnet 68 being opened at the front contact 124 of the line relay 103, which is deenergized upon the 8th interruption of the shunt path at contact 60. The controller se- ',quen ce switch is now advancing to the 13th position and a circuit is completed for the motor imag'net- 81 of the selector sequence .xswitch by way of sequence. switch contact 102, back contact 243 ofthe battery control relay 239 and back. contact 121, of the line relay- 103. In the posit-ion taken by the shaft 40,, of the brush selector, one of its fingers 41the 8th from the top in this instance-is pointing inwardly in line to en gage a latch-32, holding the 8th set of brushes 23,24 and 25 normally retracted.

The selector sequence switch now advances from the 2nd to the 5th position in which a circuit is completed for the motor magnet 02 of the brush carriage by way of sequence switch contact 111 and front contact- .124 of the line relay, the line relay having been energized again by reason of the reclosing of.

the trunk circuit at contacts 403 and 422,

while the selector'sequence switch was advancing to the 5th position. In the first stage of rotation of the brush carriage, the inwardly projecting finger 41 on the shaft 40 engages the edge of the latch'32 andreleases the set of brushes 23, 24, 25, which are eludes the terminals of the wanted lino. As the brushes approach the first set of tenninals the'levers 42, 43' of the brush carriage interrupter engage the ram plate and when the roller 51 at the free end of the lever 42 engages the first tooth 53 of said cam plate, ashort circuit of the sender circuit-l and its stepping relay is closed by way; of sequence switch contact 2 3, interrupter contact springs 48 and 49 and sequence switch contact A series of intorrup tions between contact springs 48 and 45) follow as roller 51- drops into the notches bein line witlrthe row of terminals that. in-.

' front contact 12 1- is opened and its back contact 121 is closed again, whereupon the circuit of the motor magnet 62 is opened and a circuit for the holding magnet 65 is closed by way of sequence switch contact 112, back contact and said back contact.- 121 of line relay 103. The brush carriage is thus caused. to stop with the brushes in contact with the third setof terminals in the 8th level. The sequence switch motor magnet 81. is energized at the same time in a circuit completed by way of sequence switch contact 102, back contact 213 and back contact 121, and the sequence switch moves from the 5th to the 9th position. The cont-roller sequence switch in passing the 11th position in the mean time closes contact 108 which completes a circuit for the motor magnet 381 of the trunk line sequence-switch, this circuit being completed from battery 312 by way ot the winding of said motor magnet 881, sequence switch contact 305 and sequence switch contact 108. The trunk line sequence switch thereupon advances to'the 10th position. It will be noted that the trunk line circuit is closed, however, as soon as the sequence switch reaches the 8th position and remains closed in the 9th and 10th positions.

In advancing from the 5th to the 9th position the selector sequence switch introduces various changes in the circuit by which the selected line is given a double test. In passing the 6th and 7th positions the first test is made, the circuit being closed from the neutral point of battery 109 through winding 2% of the marginal current test relay 232, sequence switch contact 209, winding of polarity test relay 231, test brush 25, test terminal 29 and cut-ott relay of the ordinary subscribers line 501 to the positive or ground pole of battery 105). Under the present assumption that this line is not busy, this circuit will receive current from the full potential of the positive portion of battery 109 and relays 232 and 231 will be energized, wl'iercupon a. circuit is closed for energizing relay 233, this circuit being by way of battery 10.), winding of relay 233, Front contact 2 ml ot. relay 2;;2, sequence switch contact 207 and Front con tact 245 of relay 2:11. lleiay 23%: then bc comes locked in a oircpit from battery 10!), winding of relay 233/ fcontact 24-6 of said contact, 22 2,

op-ease relay and s iencc switch contact 222; Relay alst o by way of i M. contac .I

T and winding 237 of relay 232, this path shunting windings 286 oti'clay and the winding of relay 231. By reason of the lOW resistance of the shunt path. just referred to the potential at the test terminal 29 of the selector and other test tern'iinals of other selectors connected in i'm-ltiple therewith will be substantially l ere'd, thus creating a condition under which t out of the 6th position the sequence switch opens the circuit of the holding magnet 65 ot the selector, which circuit had been closed in the 5th position througl'l the back contact 121 of the line relay. Before the 9th position is reached by the selector sequence switch, the trunk line is closed at contacts 806 and 307 so that line relay 103 is energized. Relay 233 having been locked in circuit as stated, a circuit is closed in the 9th position for the motor magnet 81 by way-of sequence switch contact 201 and contact of relay 223, the sequence switch thereupon advances to the 12th position, the circuit just traced being the means also of moving the sequence switch past the 11th position. In the 12th position of the sequence switch, the circuit for relay 231 is again. closed at sequence switch contact 209-tiis in order to determine the polarity of ringing current when selection is .made to a. party telephone line. Under the present assumption this relay 231 would be energized in the 12th position, opening con-*' tact 259 and closing contact 2-19 connected to the positive pulsating current generator 235. A circuit is now completed from the positive pulsating generator 235 through said contact 249, resistance 250, sequence switch contact 217, brush 24, terminal 28, one wire of line 501, the signal bell and condenser atstation 502, the return wire of said lino, terminal 2?, brush 23, sequence switch contact 21 1 and winding 251 of the ringing controlfrelay 230. Current from this generator will operate the signal hell, but is too feeble to cause the energization of said rel- 2305 Upon the response of the sub ssiiber to this signahhowever, the currentis strengttuincd by the closing of the low resistance path through the telephone apparatus at the substation and relay 230 is energized, whereupon a circuit is closed from battery 109 through sequence switch contact of relay 230, lockcs path in the test circuit ing winding 253 of said relay, supervisory relay 228, winding 107 of the repeating coil 10!) and battery 229 to round, relay 230 remains energized in sait? circuit until the sequence switch passes out of the 12th position. The supervisory relay 228 is ener gizcd, completing a circuit for the motor magnet 81 of the sequence switch by way v of sequence switch contact 218 and contact 26 1 of the supervisory relay 228. The sequence switch thereupon moves out of the 12th position and into the 13th or talking! position, the supervisory relay 228 remain ing energized in the circuit of the called line which is closed in the 13th position at. contacts 216 and 113. i

In the 13th position of the sequence switch, contact 219 is closed, thereby-completing a circuit for: the battery control relay 239, which removes battery 109 from the circuit of the trunk line and closes thiscircuit again without battery through its front contacts 262 and 263. The circuit oh the trunk line being now free from battery, line relay 103 is deenergized. In fact, re-- lays 239 and 103 are pra-cticallyoperated together, the former opening contact 243 and closing contact while the latter opens contact 124 and closes contact 121.- The circuit of the motor magnet 81 is, there-- fore, not affected and the sequence switch remains in the 13th position.

The talking circuit may be traced as fol-- lows: One section leads from battery 319 through windings 322 of repeating coil 320 to the calling telephone line (this line not being shown) the trunk section includes re-- lay 323, winding 321 of repeatingcoil 320, conductor 105, winding 106 of repeating coil 108, contacts 203 and 262 of battery control relay 239, line relay 103,shunted by condenser 250, another winding 106 of repeating coil, 108', sequence switch contact 210, conductor 1041, another winding 221 of re-- peating coil 320 and sequence switch contacts 306 and 307, this section being free from any source of steady current, but inductively united byrepeating coils with the c-the-rsections. The third section of the talking circuit maybe traced as follows: battery 229, winding 107 of repeating coil 108, supervisory relay 228, sequence switch contact 216, brush 24, terminal 28, one wire of line 501, telephone apparatus at substation 502, return wire of line 501, terminal 27, brush 23, sequence switch contact 113 and another winding 107' of repeating coil 108 to ground, In this 13th position of the sequence switch, the brush selector is returned to normal position, a circuit being completed for the motor magnet 68 through sequence switch contact 25, contar 0 and arm 50. "When the shaft reaches Mal. position the free and ot' the aim drops intc the deep notch iii-the star Wheat and the cii'Quit at contact 59, whereupon the shaft" comes to rest.

When the called subscriber replaces his receiver on its switch hook at the end of the conversation the line circuit is opened, onus-v ing supervisory relay 228 to be denergized, whereupon the circuit of the battery control relay 239 is opened at contact 204 of 'said supervisory relay, battery 109 is again included in the circuit of the trunkline, and lin'e" relay 103 is energized. Relay'323'at the contrfaller end of the trunk line is also energized and closes the local circuit of the supervisory lamp signal 318. This indicates to the operator that the/called subscriber has hung up his telephone. In response to the lighting of supervisory lamp signal 318, the operator may cause switch 314 to be closed, which completes a circuit for motor magnet 381 by way of sequence switch contact 308. The sequence switch for the trunk line thereupon moves out of the 10th position and advances to the 15th. In passing out of the 10th position the circuit of the trunk line is opened at contacts 306 and 307, whereupon line relay 103 at the selector is deiinergized, The battery control relay 239 being also deenergized at this time, a circuit iscompleted for the motor magnet 81 of the selector sequence switch by way of sequence switch contact'102, back contact 243 of the batter control relay 239 and back contact 121 0 line relay 103. The sequence switchthereu'pon advances to the 16th position, the circuit for the motor magnet 81 :just traced being the means also of causing the sequence switch to 'pass by the'leth posicircuit for the locking relay 233 will be openedat sequence switch'contact 222. It

closed-before contact 222 is opened, there is no pathcompleted for relay 283i'by Way of contact 221 in this instance, for the reason that line relay 103; is deiinergize d and its front contact 12 1 is; at this time open,- The denergization' of relay 233 causes'the' open.- ing-of the test circuit through winding-237 of relay 232 so that this relay is also deenergized. The immediate result. of the opening of the test circuit is the removal of the busy test condition at the line of the connected subscriber. Upon reaching, the 16th position, the sequence switch ,clos'es a circuit for tho selector= motor magnet by way of sequence switch contact '114,'b ack contact 257 of relay 232, se-quence-lswltch contact 208 andcontact, 258* of relay. 231. The brush carriage of the selector is themupon moved aroundiito normal positioirand when this position isreached, a circuit is closed for relay 232 from neutral point or battery 109, winding 236 of relay 232, sequence switch contact 215, the normal stop plate 46 of the selector and levers 12 and 43 Ttion; Upon entering the 14th position, the

will be noted that, although contact 221 is to ground through the frame of the selector, whereupon relay 232 is energized, opening the circuit. of the motor magnet- 62 at its back contact and closing a circuit for the holding magnet (35 at its front contact 2 5%, this latter circuit being completed by way of sequence switch contact 206. The one 'gization of relay also completes a circuit for relay 233, this circuit including battery 109, front contact 24 1- of relay sequence switch contact 208 and contact 258 01 relay 2'01. Relay -00 thereupon closes a circuit for the motor magnet Slot the sequence switch by way of sequence switch contact 201 and contact 2 1801 relay The sequence switch is thus caused to move out of the 16th position and to be returned to normal. The holding magnet remains energized in the 16th and 17th positions of the sequence switch. In passing out of the 17th position, the circuit for relay 232 is opened at sequence switch contact 215. Relay 233 is released in the 18th position by the opening of sequence switch contacts 209 and 222.

It will be noted that the sequence switch contacts 211 and 212 maintain their circuits about the windings 106 of repeating coil 108 during the periods (positions 2 and 5) in which the impulse sending operations occur. The trunk line conductors 104: and 105 are closed by way of windings 106, while the sequence switch IS in positions (5 to 14: m-

elusive, one side, conductor 104, being closed during this period way of contact 210. Upon leaving the 14th position, a short circuit of the trunk line is closed at sequence switch contact 213. This short-circuit serves to prevent the closure of contacts 309 and 310 of the trunk line sequence switch from causing the operation of line relay 103 at the selector. Upon leaving the 18th position, the short circuit is removed and relay 323 at the controlling end of the trunk line is energized, whereupon a circuit is established for motor magnetBSl ot' the trunk line sequence switch by way of sequence switch contact 811 and the back contact of said relay The sequence switch thereupon moves out of the-15th position and returns to normal. :When the selector sequence switch reaches the 17th position, a local test wire circuit is closed at sequence switch contact 227, this circuit including resistance 257 and certain electromagnetic de- -vices 490 which may be associated with a selector immediately preceding the final switch and which may be the means of starting the'restoring operation for such selec tors. Selection, of non-busy private branch change Zivzc.-Let it now be assumed that the operator had. caused the actuation of controlling switches 45S and are for the pin-pose or causing the final switch mechanism to make connection with one of a plurality of lines, say line 50$) leading to pri vate branch exchange 508 (subscriber No. 74). The terminals for this line are loca ed in the 8th level and in the lifth range on the final switch and the mode of opcration of the mechanism up to the time that the selector sequence switch leaves the fitth position is the same as that already described except that the brushes 23, 24. and 25 will be caused to move to the fifth set of line terminals in the 8th level instead of the third set as under the previous assumption, T he test terminal 29 oi. this set is coi'mectcd to the vnegative pole of battery 109 and as it is assumed that the line is not busy, the potential existing at that terminal when the test brush 25 makes connection therewith high. Therefore, as the sequence switch. is passing the 6th and 7th positons (the first test period), in which. the test circuit closed at contact 209, relay is energized, but relay 231 is not ener l ZQd, the latter be ing unailected by negative curre 1 The second test period. he ing again closed at contact 209, and a cla cult is completed tor relay 233 hy way oi.

front contact 244: of relay s switch 208 and normal contact lay 231. Relay 233 LS tlIC-it-lOL and becomes locked in a front contact 2&6 of said' quence switch. contact The connectc line 509 is now caused to test busy to other selectors by reason of the closure of the low resistance shunt path in. the test circuit by way of contact 24'? or relay and wit ing 237 of relay 232. The o iening oil hart: contact 25? of relay 232 prevents the in magnet 62 of the selector from being e gized to adi 'ance the selector :tor hun over the terminals of the other lines leadin to the private branch exchange 508. The sequence switch is now caused to leave the nth position by reason of the closure contact 248 of iclay and the mode of operation which. follows is the same as that previously described, when the connection had been as sumed to be made to a non-busy ordii'iary line, exceptthat in the 12th, the ringing position of the sequence switch, the polarity test relay 231 is not energized and the negative pulsating generator instead of the pcsitive pulsating generator 235 is included in the ringing circuit oi the called lin it may be noted in this connection that the modes o1 operation of the switch "is nisni which w il non-busy p the same as tion of non busy private l) mes, been.

55 and 222.

10 larity test relay 231 in the 12th position. of:

the sequence switch is made use of in party line ringing to connect a generator adapted to operate selectively the signal bell of the Wanted party line subscriber. V

Selection of busy ordinary" subscrb efs time, Letit now be assumed that the selected line is that of a busy ordinary subscriber.

The test terminal 29 would therefore haye a low positive potential, and when the test circuit is closed in the 6th and 7th positions (the first test period) and the 9th position (the second, test period) of the sequence switch, relay 232 does not receive suilicient current to cause its cnergization. Relay 2'5 231, however, is energized and when the sequence switch reaches'the 9th position, a circuit is closed "for the motor magnet 81 of the sequence switch by way of contact 201 and front contact 245st relay 231,.vhereupon the sequence switch advances from the 9th to.

the In the 10th and 11th, pos of relay 231 is open at sequence switch contact 209 and said i'elay231 is therefore de- 11th position.

energized so that in position 11, a circuit is completed for the motor magnet 62 of the brush carriage by way of sequence switch contact .114, back contact of relay 232,

sequence switch contact 208, and norinal'con 40 tact 258 of relay 22-51.

The brush carriage of the selector thereupon caused to more around to its nei'n'ial position, a circuit then being closed for relay 232 from the neutral pole of batteryltlf), through winding 236 of relay 232, sequence switch contact 215,

the normal stop plate to of the selector and levers 4-2 and 4-3 thereof tog'round through the frame of the switch mechanism. Relay 232 is energized in this circuit and operates to complete a circuit for relay 233 by way of its front contact 2'21, S-LQ'UGIU'TO switch contact 208 and normal. contact 258 of relay 231.

Relay 23. 3 is therefore energized and closes its locking circuit by way of contacts 246 Contact 248 of relay is also closed, whereupon a circuit completed for the motor magnet 81 of the sequence switch by way of sequence switch contact 201.-

The opening of back contact 257 of relay 5 232hreaks the circuit for the motor magnet 62 or" the brush carriage and the closing of front vcontact ill of said relay 232 closes at the some tune a circuit for the holding magnct 65, this latter circuit being completed 65 by way of sequence switch contact 206, said ions of thcsequciice switch the circuitswitch is passing positions 11 and 12. A 7

circuit for the niotor magnet 81 being closed by relay 233, the sequence switchadvances from the 11th to the 14th position'in which a busy back signal is given to indicate that the line desired is busy. in the 12th and 13th positions of the sequenceswitcli, the

circuit of relay'232 is open at sequence a switch contact 21 5. Thisirelay is therefore deiinergized When the sequence switch leaves I the 11th position; Relay 23?, however, re-

mains energized in its locking circuit by way of its front-contact 246 and sequence switch contact 222 until the sequence switch arrives-at the 14th position wherein relay may remain energized for a moment in the circuit completed by way of its front Contact 246, sequence switch contact 221 and front contactl24; of line relay 1'21. Upon reachingthe 13th position, the sequence switch closes Contact 205 to return the brush selector to normalp In the 14th position relay 232 is ags-in energized in the circuit heretofore traced, which is completed by way of sequence switch contact 215 Finally, in the 14th position of the sequence. switch, the busy back interrupter 238 is brought into circuit with the battery control relay 239 by the closing of sequence switch contact 220. This interriqficr causes intermittent energization of said relay whereupon current fronibat-tcry 101} is iiiterinit-tently applied to the circuit of the trunk line conductors 10% and 105.

battery control relay 239 and the line relay 103 are afi'ecte'cl practically in unison so'that the operation of the sequence switch is not effected to cause its advance from the 14th position. The intermittent application of current in the trunk line merely causes flash ing of the snpervisorylanip signal 318. The local circuit for test relay 23.3 nil-lbs opened at the front contact 12-1 of the line relay 103 and said relay 233' will beadeenergized as soon as the busy back inter cansin switch contact 314 at'th'e'controlleiii end 0 the trunk line to beclosedl This completes a circuit for niotor'magnet381 by way of "sequence switch contact .308Pand causes the'sequence switch associated witlr {the trunk line to be moved from the-10th to

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