US1680565A - Multioffice telephone system - Google Patents

Description

J. E. OSTLINE MULTIOFFICE TELEPHONE SYSTEM Original F led April 9, 1923 10 Shea t m John ..E .U'flm'e J. E. OSTLINE I MULTIOFFICE TELEPHONE SYSTEM Original Filed April 9, 1923 10 Sheets-Sheet 2' Jul-m E. UETZmE 10 Sheets-Shark 3 J. E. OSTLINE MULTIOFFIGE TELEPHONE SYSTEM Original Filed April 1923 Aug. 14, 1928.

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I KULTIQFFICE TELEPHONE SYSTEM Sheets-Sheet 5 or i inal Filed April 9, 1923 I I N j WW I I E v i v l v nuen 02 J. E. OSTLINE 1 MULTIOFFICE TELEPHONE SYSTEM Aug. 14, 1928. 1,680.565

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1,680,565 J. E. OSTLINE MULTIOFFICE TELEPHONE SYSTEM Ori Filed ril 9 10 Sheets-Sheet '7 Inuen 1113- Aug. 14, 1928. 1,680,565

J. E. OSTLINE MULTIOFFI CE TELEPHONE SYSTEM Original Filed April 9, 1923 10 sheets-sh t 8 n Q N F9 Aug. 14, 1928. 1,680,565

J. E. OSTLINE MULTIOFFI CE TELEPHbNE $YSTEM Original Filgd April 1923 l Sheets-Sheet 9 I I I I. I

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J. E. OSTLINE MULTIOFFI GE TELEPHONE SYSTEM Original Filed April ,1923 10 Sheets-Sheet l0 Im/Erz Ur-- Jul-m E. U'ETZmE Patented Aug. 14, 1928.

UNITED STATES PATENT OFFICE.-

JOHN E. OSTLINE, OF LIVERPOOL, ENGLAND, ASSIGNOR, BY MESNE ASSIGNMENTS, TO

AUTOMATIC ELECTRIC INC., OF CHICAGO, ILLINOIS, A CORPORATION OF DELA- WARE.

MULTIOFFICE TELEPHONE SYSTEM.

REISSUED Application filed April 9, 1923, Serial No. 630,728. Renewed January 5, 1928.

The present invention relates in general to multi-oflice telephone systems, but more particularly to such systems as comprise in one net work offices or exchanges of two different kinds, the offices of one kind being manual otfices wherein connections are completed by operators, while the other kind of offices are automatic oifices in which connections are completed b means of automatic switches; and the ject of the invention is to provide new and improved circuit arrangements for handling inter-office calls from an automatic exchange to a manual exchange.

The various features of novelty will be fully pointed out hereinafter, reference being had to the accompanying drawings.

Figs. 1 to 8, inclusive, are circuit diagrams of sufficient of the apparatus used in a system of this kind to illustrate the preferred form of the invention. The equipmentrepresented by Figs. 1 to 3, inclusive, is located in the automatic exchange, while the equipment represented by Fi s. 4 to 8, inclusive, is located in the manua exchange.

Fig. 1 is a circuit diagram of an automatic to manual repeater D, together withthe coder selecting line switch C.

Fig. 2 is a circuit diagram of a portion of a coder, and discloses the coder relay group GR, and the sending switch S.

Fig. 3 is a circuit diagram of the remainder of the coder and discloses the master digit controller M, and the first, second, and fourth digit registers M to M, inclusive.

Fig. 4 is a circuit. diagram of a trunk relay group D and a trunk finder C.

Fig. 5 is a circuit diagram of a cord circuit 0, an operators'receiving equipment P, and the manual substation A, together with its associated line and cut-oft relay equipment.

Fig. 6 is a circuit diagram of a decoder D.

Fig. 7 is a ircuit diagram of a storage relay group Dftogether with the indicating device L, which will be hereinafter referred to as the .call indicator lamps.

Fig. 8 is a circuit diagram of a marker Wributer S, a marker S and a set-up control switch S Fig. 9 is a trunking diagram of the system which is shown in detail in Figs. 1 to 8, inclusive.

Fig. 10 is achart showing the digits 1 to U, inclusive, and the corresponding code trains.

Fig. 11 is a layout showing how sheets 1 to 8, inclusive, should be joined together.

It will be advisable to first consider the trunking layout, Fig. 9, as an understanding of this will assist in the explanation of the rest of the drawings. It may be stated that. the illustration of the trunking is only fragmentary. The substation A is one of a plurality of ordinary automatic substations terminating in an automatic exchange, and is provided with the usual talking, signalling and impulse sending instrumentalities. The conductors from the substation A terminate in the line switch C, which may be briefly described as a rotary line switch whose wipers move in a forward direction only. A plurality of these line switches are given access toa group oftrunk lines extending to first selector switches.

One of the trunk lines to which the line switch C has access is shown in the drawing as extending the selector F, which is a vertical and rotary selector of the well known Strowger type. In a multi-oflice system of the kind herein contemplated, the first selector switches are usually known as office selectors, and the selector F, in common with a plurality. of similar'selectors, has access to a plurality of groups of trunk lines, each of which groups may be extended to a different oiiice or exchange in the system. Some of these groups of trunk lines may extend to automatic exchanges, while other groups may extend to manual exchanges. A trunk line in one of the latter groups is shown in the drawing, and extends by way of the repeater D to the trunk relay group D in a manual oflice.

\Vhen a connection is extended to the repeater D no circuit changes take place at the manual office, but the coder selecting line switch C associated with the repeater in question, operates to select an idle coder. As the wiper of the master digit. controller M is in first position the dialling of the next digit in the called number will cause the first digit register M to advance its wipers a like number of steps, after which the master digit controller M will move to second position. Vhen the next digit of the called number is dialled the second digit register 16 will now remove ground 30 ation of the marker 40 with the 50 correspond to the 55 plurality 60 will M will advance its wipers a like number of steps, after which the switch M will move to third osition. 'When the next digit the calle number is dialled the third digit 6 registerlS/i will advance its wipers a like number of steps, after which the switch M will move to fourth position. When the next digit of the called number is dialled the fourth digit register M will advance its 10 wipers a like number of steps, after which the switch M When the registration is complete a is closed to the trunk relay group D at the manual ofiice. The trunk relay group D from the test contacts associated therewith in the multiple banks of the markers, and at the same time will place ground upon the starting common leading to the marker distributer S It will move to fifth position.

circuit will be assumed that the marker dist-ributer S has already preselected the marker S, which will now advance its wiper into enagement with the test contact associated with the trunk relay group D A further 26 result of the operation of the marker S is the rounding of the associated test contact in t e bank of the marker distributer S whereupon the said switch will preselect another marker. A further result of the oper- S is the removal of ground from the test contact associated therewith in the bank of the set-up control switch S and at the same time ground will be placed upon the starting common leading to the set-up control switch S The set-up control switch S advances from one position to the next as the connections are completed, and when its wiper engages the particular bank contact associated marker S, a circuit change will occur in the trunk relay group D whereupon trunk rela group D will become associated with tie decoder D The conductors leading to the decoder D are multipled through each trunk relay group in the position. At this time a change will occur in the inter-oflice trunk circuit such that the sending switch S will proceed to deliver a series of code trains to the decoder D which number set up on the digit M to M", inclusive. Certain counting relays in the decoder will respond to these code trains, and when the decoding is complete, the circuit is transferred over a of conductors to the storage relay registers group D, whereupon the last four digits of the called number will be displayed upon the call indicator lamps L.

At this time the set-up control switch S advance to the next marker, whereupon the decoder becomes dissociated from the trunk relay group D and becomes associated with the trunk relay group selected by the next marker. At this time the trunk relay 5 group D causes ground to be removed from therewith in the such as the trunk The operator will now take any plug in her osition and insert the same into the multiple jack of the line whose number is displayed upon the call indicator lamps L. It will be assumed that the plug associated with the cord circuit 0 is used, whereupon the trunk finder C will seek the ungrounded test contact associated with the trunk relay group D When the cord circuit 0 becomes associated with the relay group D the storage relay group D and the call indicator lamps L will be released, whereupon the dccoder D may transfer a new call number to the stora e relay group.

Procee ing now to the detailed explanation of the circuit drawings and referring first to Fig. 1, the repeater D is an automatk impulse repeater of the general type in C0111 mon use, and in addition to pro"isions foi repeating operating impulses, it provides i holding circuit for the automatic switche: and thus renders it unnecessary to use moi" than two conductors for the inter-oilic trunk. The coder selecting line switch C may be briefly described as a rotary lin switch whose movable terminals or wiper have no normal position, and which hav movement in a forward direction only. I further explanation, it may be stated tha the wipers of this switch advance. upon th deenergization of the stepping magnc rather than upon its energization. As show in the figure, each repeater D has in associa tion therewith a coder selecting line switcl such as the line switch C A plurality t these line switches are given access to group of trunks, each of which extends to coder. In ractice, a grou of coders won? be provide equal in num er to the max mum number of simultaneous uncompletr connections likely to occur in the group i repeaters served by the aforementioni coders.

Referring to the coder relay operation of the registerin equipment in of the sending 'switch The sendii switch S is a rotary switch similar to t coder selecting line switch C. It may stated at this time that the wiper 133 of t switch S is so constructed that it will enga the next contact in its bank before bre'aki connection with the preceding contact. interrupter T may be considered as being constantly moving levice icapable of i. pressing ground im ulses upon armature l at the rate of approximately 10 impulses 1 second.

Referring to'Fig. 3, the master digit c( troller M, the first digit register M the s 0nd digit register M, the third digit regis M and the fourth digit register M Fig. 2 there will be foui group CR which controls t':

simple ten point step by step switches, each of which is provided with an operating magnet, a release magnet, and a set of oif normal springs which are operated when the switch wipers are advanced out of their normal position. The master digit controller M advances the wipers 211 and 217 over banks B and B, respectively. The first digit register M advances the wipers 230, 231 and 232 over the banks B B and B, respectively. The second digit register M advances the wipers 233, 234 and 235 over the banks B, B and B", respectively. The third digit register M advances the wipers 236, 237 and 238 over-the banks B and B, respectively. The fourth dig1t register M advances the wipers 239, 240 and 241 over the banks B B and 8', respectively.

In Fig. 4 will be found the trunk relay group D upon which the inner-ofiice trunk is terminated. The trunk finder C" is a rotary switch similar to the coder selecting line switch'C A plurality of trunkrelay groups, such as the relay group D is provided at each manual position. Each trunk relay group in the position terminates upon a set of contacts in the multiple banks accessble to trunk finders, such as trunk finder Fig. 5 shows the, plug ending cord circuit 0. Each cord circuit 0 will have in association a trunk finder such as the trunk finder C of Fig. 4. In practice, the number of cord circuits 0 and associated trunk finder switches C will be suflieient to care for the maximum number of simultaneous connections likely to occur in the position. The number of cord circuits will usually be less than the number of trunk relay groups to which they have access. The manual telephone substation A has the usual talking and signalling instrumentalities. An operators receiving circuit or head set is shown at P.

Referring to Fig. 6, this figure shows a decoder D The relays 511 to 514, inclusive, and 540 to 542, inclusive, are control relays which govern the operation of the set-up relays SR. Four groups of set-up relays are'indicated, each group being made up of ve relays. Each of the five relays is a wo step relay. Considering relay 533, for example, the energization of its left hand winding will cause it to partially 0 erate and prepare the circuit for its rig t hand winding. When the energizing circuit is opened, a shunt will be removed from around the right hand winding, whereupon the relay will become fully opearted. The set-up relays SR receive the coded impulse train corresponding to the first digit, the set-up relays SR receive the coded impulse train for the second digit, the set-up relays SR receive the coded impulse train for the third digit, while the set-up relays SR receive the coded impulse train for the fourth digit.

In Fig. 7 will be found the storage relay group D, and the call indicator lamps L. Four .sets of storage relays are indicated, each set being made up of four relays. The relays in the storage relay set SRS are controlled by the set-up relays SR. The relays in the storage relay set SIRS are controlled by the set-up relays SR The storage re lay set SRS is controlled by the set-u relays SR. The storage relay set SRr is controlled by the set-up relays SR The circuit to the first digit call indicator lamps is controlled by the storage relay set SRS. The circuit to the second digit call indicator lamps is controlled by the storage relay set SE8 The circuit to the third digit call indicator lam s is controlled by the storage relay set SHE? The circuit to the fourth digit call indicator lamps is controlled by storage relay set SRS.

Referring to Fig. 8, we find the marker distributor S which advances the wipers 311 and 340 over the banks B and B respectively. The marker S advances the wipers 318 and 338 over the banks B and B, respectively. The set-up control switch S advances the wiper 335 over the bank B. These switches are all similar to the coder, selecting line switch C There is one marker distributer, such as the switch S provided for each position. The wiper 311 of switch S is connected to a starting conductor common which is multipled through each trunk relay group in the position. Upon each contact in the bank B is terminated a start conductor which leads to a marker, such as the switch S In practice, a number of markers would be provided equal to the maximum number of simultaneous uncompleted calls likely to occur in the position, usually about six or seven. Each marker is associated with a test contact in bank B, which serves to advance the marker distributer S when the marker in question is seized. A test conductor from each trunk relay group in the position terminates in the bank 13. An operating conductor from each trunk relay group terminates upon a contact in the bank B. The relay .327 of the set-up control switch 8 is connected to a starting common which is multipled through each marker in the position. A test conductor from each marker is terminated upon a contact in the bank B The code used to transfer the call number set up on the digit registers utilizes each side of the inter-office trunk separately. Each train consists of from one to three ground impulses over the pulsing trunk conductor. Three conditions are imposed upon the control trunk conductor, i e., neutral, high resistance ground, or low resistance ground.

The three possible conditions on each trunk conductor allow of nine combinations, which correspond to the digits 1 to 9, inclusive, as shown in Fig. 10. The code for the digit zero is obtained by the combination of a neutral control trunk conductor and no impulses on the pulsing trunk conductor. The circuit change which is necessary at the (lecoder between the end of one code train and the beginning of the next, is brought about by a momentary grounding of the control trunk conductor.

Referring to the sending switch S, Fig. 2, it may be said that at the proper time the wiper 133 becomes associated with the control trunk conductor, while the wiper 135 becomes associated with the pulsing trunk conductor. It will be noted that the contacts 4, 8, 12 and 16 in bank B are multipled to the armature 142. These are the switching points which control the change over circuit at the decoder. The first train of coded impulses is delivered while the switch S is passing over bank contacts 1, 2 and 3. the second train while passing over contacts 5, 6 and 7. the third train while passing over contacts 9, 10 and 11, while the fourth train is delivered while passing over contacts 13. 14 and 1:). The seventeenth contact in bank B is reached after the complete code has been sent, and is utilized to cause the release of the coder. The remaining contacts in bank B are multipled and serve to insure that the switch S will return to normal upon the release of the coder.

Contacts 1, 2 and 3 of bank 1?) are multipled and carried by conductor 144 to contacts 7, 8 and 9 in bank B of the first digit register M Fig. 3. Contacts 4, 5 and 6 ot the same bank are connected through the high resistance 250 to conductor 144. From the foregoing it is evident that conductor 144 will be ungrounded if the digit registered upon switch M be a 1, a 2, a 3, or a 0. It follows, therefore, that the control trunk conductor will be neutral while the sending switch is advancing over the first, second and third bank contacts. If the digit registered upon switch M be a 4, a. 5, or a 6, the conductor 144 will be grounded through resistance 250, and the control trunk conductor will have a high resistance ground placed upon it while the switch S is advancing over the first, second and third bank contacts. If the digit registered upon switch M be a 7. an 8, or a 9, the conductor 144 will be grounded directly and the control trunk conductor will have direct ground placed upon it while the switch S is advancing over the first, second and third bank contacts.

Contacts 5. 6 and 7 of bank B" are multipled and carried by conductor 147 to contacts 7. 8 and 9 of bank 13 of the second digit register M Contacts 4, 5 and 6 of the same bank are connected through the high resistance 251 to conductor 147.

Contacts 9, l0 and 11 of bank 15 are multipled and carried by conductor 150 to contacts 7, 8 and 9 of bank B of the third digit register M Contacts 4, 5 and 6 of the same bank are connected through the high resistance 252 to conductor 150.

Contacts 13, 14 and 15 of the bank B are multipled and carried by conductor 153 to contacts 7, 8 and 9 of bank 13 of the fourth digit register M. Contacts 4, 5 and 6 of the same hank are connected through the high resistance 253 to conductor 153.

To sunnnarize; it may be said that the condition of the control trunk conductor during the transmission of the first code train is determined by the position of wiper 230 of the first digit register M. Its condition during the transmission of the second code train is determined by the position of the wiper 233 of switch M during the transmission of the third code train by the position of the wiper 236 of switch M while its condition during the fourth train is determined by the position of wipers 239 of switch M.

The grounding of the pulsing trunk conductor will now be explained. The first contact in bank B" of switch S is carried by conductor 145 to the multipled contacts 1, 3, 4, 6, 7 and 9 in bank B of the first digit register M The second and third contacts in bank B are multipled and carried by conductor 146 to contacts 2 5 and 8 in bank B and contacts 3, 6 and 9 in bank B". From the foregoing it is evident that conductor 145, only, will be grounded it the digit registered upon the switch 'M be a 1. a 4, or a 7. It follows. therefore. that only one impulse will be delivered to the pulsing trunk conductor while the sending switch is advancing over the first. second and third bank contact. If the digit registered upon switch M be a 2, a 5, or an 8, the conductor 146, only, will be grounded and two impulses will be delivered to the pulsing trunk conductor while the sending switch is advancing over the first, second and third ha nk contacts. If the digit registered upon switch M be a 3, a 6, or a 9. both conductor 145 and conductor 146 will be grounded and three impulses will be delivered to the impulsing trunk conductor while the. sending switch is advancing over the first, second and third bank contacts.

Contact 5 of bank B" is carried by conductor 148 to the multipled contacts 1. 3. 4, 6.7, and 9 in bank 13* of the second digit register M The sixth and seventh contacts in bank B" are multipled and carried by conductor 149 to contacts 2. 5 and 8 in bank B and to contacts 3. 6 and 9 in bank 13.

Contact 9 of bank B" is carried by conductor 151 to the multipled contacts 1. 3, 4, 6, 7 and 9'in bank 13 of the third digit register M. The tenth and eleventh contacts 111 bank B are multipled and carried by conductor 152 to contacts 2, 5 and 8 in bank B and to contacts 3, 6 and 9 in bank B Contact 13 of bank B is carried by conductor a to the multipled contacts 1, 3, 1, 6, 7 and 9 in bank 13 of the fourth digit register M*. The fourteenth and fifteenth contacts in bank 15" are multipled and carried by conductor 155 to contacts 2, 5 and 8 in blank B and'to contacts 3, 6 and 9 in bank B To summarize; it may be said that the number of grounded impulses delivered to the pulsing trunk conductor during the transmission of the first code train is determined by the position of wipers 231 and 232 of the first digit register M The number delivered durin the transmission of the second code train is determined by the position of wipers 234 and 235 of the second digit register M during the transmission of the third code train by the position of wipers 237 and 238 of the third digit register M while the number of impulses delivered to the pulsing conductor during the fourth code train is determined by the position of wipers 240 and 211.

The general object and scope of the invention having been pointed out, the operation of the apparatus involved will now be described more in detail, and for this purpose it will be assumed that the subscriber at the automatic substation A, Fig. 9, desires to establish connection with the subscriber at the manual substation A, whose telephone number is assumed to be 32490. When the re ceiver is removed at substation A, the calling line is extended in the well known mannor to a first selector, such as the selector F, by means of the primary line switch C. \Vhen the calling subscriber operates his calling device for the'first digit 3 of the called number, a first selector F will raise its shaft and wipers opposite the third level of bank contacts, whereupon it will rotate in search of an idle trunk. It will be assumed that the first selector F connects with a set of bank contacts indicated by reference characters 10, 11 and 12, Fig. 1. The two conductors of the calling line are now eon nccted with trunk conductors 13 andl and a. circuit will be completed over the" said trunk conductors through springs 15 and 16, of relay 52, and their resting contacts, to the line relay 1? of rcpeatcr D.

Vhcn the line relay 17 becomes energized, a circuit will be closed for the slow acting release relay 19 at armature 18. The latter relay. upon energizing. will place ground u 3 release trunk 20 by way-of armature .41. thereby completing a holding circuit for the preceding switches in the usual manner. A further result of the energization of relay 19 is the closure of a circuit traceable from ground, working contact and armature 22, through the upper winding of the electropolarized relay to battery. This is without etfect, as the upper winding of relay 221i is not strong enough to operate the associated arniatures. A further result of the encrgization of relay 19 is the closure of a circuit' from ground, working contact and armature 22, armature 2st and its resting contact, armature and its resting contact, through line relay 2(3 of the coder selecting line switch C to battery. Relay up energizing, closes a circuit for the switching relay 27 in series with the stepping magnet 28 at armature 29, and at armature 30 conmeets the test wiper 31 to the above circuit at a point between the winding of the switching relay and the winding of the stepping magnet. If the trunk with which the wipers of the coder selecting line switch are now associated is busy, there will be a ground on the test contact wi.- h which the test wiper 31 is in engagement. The switching relay 2? will be short circuited, and the stepping magnet 28 will be operated to advance the switch wipers into engagement with the next trunk line. If the next trunk line is bus the same operation will be repeated, an the stepping magnet 28 will continue to operate in the manner of a buzzer to advance the switch wipers-step by step until an idle trunk line is encountered. If the trunk line with which the wipers of the line switch are associated is idle, there will be no ground potential on the test contact engaged by the test wiper 31 and the switching relay 27 will not be short circuited, but will be immediately energized in series with the stepping magnet 28, the said magnetremaining inoperative due to the hig resistance of the switching relay. \Vhcn the switching relay 27 becomes energized, ground at armature 29 of relay- 26 is connected through working contact and armature 32, through test wiper 31 to test contact 34: and its multiples in the banks of other coder selecting line switches, in order to make the selected coder busy. A further result of the cncrgization of relay 2? is the closure of a circuit traceable from ground, working contact and armature 25), working contact and armature 33, armature 53 and its resting contact, armature 35 and its working contact, through relay 36 to batteryl Relay 36, upon energizing. forms a locking circuit for itself, independent of relay 26, which may be traced from ground, working contact and armature 22. armature 24 and its resting contact, armature and its working contact, armature 35 and its working contact, through relay 36 to battery. A further result of the energization of relay 36 is the regrounding of release trunk conductor 42 over a circuit traceable. from ground, working contact and armature 22, armature 24 and its resting contact, contact controlled by armature 37, working contact and armature 53, armature 33 and its working contact, working contact and armature 32, test wiper 31 to test contact 31, and release trunk conductor 42. The above circuit will maintain ground upon release conductor 42 after the deeiiergization of the slow acting line relay 26, which will take place shortly after its circuit is opened at armature 25 of relay 36. In order to insure the proper operation of relay 36, the springs are so adjusted that armature 25 engages its working contact before armature 53 opens its resting contact.

It will now be assumed that the calling subscriber dials the next digit 2 of the called number, as a result of which line relay 17 will momentarily release its armature a like number of times. At each deenei'gization of relay 17 a circuit may be traced from ground,

working contact and armature 22, restin contact and armature 38, armature 39 and its working contact, working contact and armature 40, wiper 54, bank contact 33, conductor 41, slow acting relay 111, Fig. 2, conductor 112, wiper 211, Fig. 3, first contact in bank B, through the ste ping magnet 212 of the first digit register lit to battery. A branch of the above circuit may be traced from conductor 42, contacts controlled by armature 11 1, through relay 115 to battery. Relay 115, upon energizing, forms a locking circuit for itself, independent of conductor 41, which may be traced from the grounded release trunk conductor 42, armature 114 and its working contact, through relay 115 to battery. A further result of the energization of relay 115 is the removal of ground from conductor 161 at armature 116, thereby removing ground from the oil normal springs ONS associated with the master digit controller M, and the digit registers M to M, inclusive, Fig. 3.

The stepping magnet 212 of the first digit register M will respond to the impulses delivered to it and will advance the wipers 230, 231 and 232 into engagement with the second contact in the banks B, 13 and B, respectively. The slow acting relay 111 will energize at the first impulse and will remain operated throughout the period that impulses are passing through it. Relay 111, upon energizing, will close the circuit of slow acting relay 119 by way of armature 118. \Vhen relay 111 deenergizes, shortly after the last impulse has passed through it, the circuit of slow acting relay 119 will be opened. and a circuit will be closed from ground, armature 118 and its resting eontact, armature 120 and its working contact, armature 121 and its resting contact, con ductor 122. through stepping magnet 213 of the master digit controller 711 to battery. The stepping ,magnet 213 will now energize and advance wipers 211 and 217 into engagement with the second contact in the banks 1% and B, respectively. The deenergization of slow acting relay 119 will occur shortly after its circuit is opened at armature 113. When this takes place the circuit of stepping magnet 213 will be opened at armature 121).

It will now be assumed that the calling subscriber operates his calling device for the next digit 1 of the called number, as a result of which the line relay 17 will momentarily deeneigizc a like number OflllDBS. At each deenergization of relay 17, a ground is placed upon conductor 112 over the previously traced circuit, which continues through the wiper 211 in second position to the stepping magnet 214 of the second digit register M to battery. The stepping magnet 211 will energize four times and operate to advance the wipers 233. 221i and 235 into engagement with the fourth contact in the banks l5, l5 and B", respectively. The relays 111 and 119 will operate as before to send an impulse of current through the stepping ,inagnet 213 of switch M, whereupon the wipers 211 and 217 will be moved into engagement with the third contact in the banks B and B, respectively.

It will now be assumed that the calling subscriber operates the calling device in accordance with the next digit 9 of the called number, as a result of which the line relay 17 will momentarily deenergize nine times. At each deenergization of relay 17 the usual circuit is extended to the wiper 211 of switch M, the circuit continuing through the third contact in bank B, through stepping magnet 215 of the third digit register M to battery. The steppin magnet 215 will energize nine times, an will operate to advance the wipers 236, 237 and 238 into engagement with the ninth contact in the banks 15, B and B, respectively. The relays 111 and 119 will operate in the usual manner to send an impulse of current through stepping magnet 213 of switch M, whereupon the wipers 211 and 217 are advanced into engagement with the fourth contact in the banks B and B, respectively.

It will now be assumed that the calling subscriber operates his calling device for the last digit 0 in the called number, as a result of which the line relay 17 will momentarily release its armature ten times. .\t each decnergization of relay 17, the usual circuit 7 is extended to wiper 211 of switch M, the circuit continuing through the fourth con-- tact in the bank B, through stepping relay 216 of the fourth digit register M to battery. ten times and operate to advance the wipers 2311 240 and 241 into engagement with the tenth contact in the banks B, B and B. respectively. The relays 111 and 119 will Stepping magnet 216 will energize operate as before to cause an impulse of cur- 3 rent to be delivered to the stepping magnet 213 of switch M, whereupon the Wipers 211 and 217 are advanced into engagement with the fifth contact in the banks B and B, respectively.

When wiper 217 of switch M engages the fifth contact in the bank 13, a circuit may be traced from grounded release trunk conductor 42, wiper 217 in fifth position, conductor 218, resting contactand armature 125, through lower Winding of relay 126 to battery. Relay 126, upon energizing, places its upper winding in bridge of the inter-office trunk, whereupon a circuit may be traced from ground, working contact and armature 611 of position busying relay 612, Fig. 5, conductor 613, resting contact and armature 411, Fig. 4, resting contact and armature 412, resting contact and armature 413,

armature 414 and its resting contact, puls ing trunk conductor 51, armature 50 and its resting contact, Fig. 1, armature 49 and its working contact, wiper 48, bank contact 35, conductor 129, armature 128 and its resting contact, Fig. 2, armature 127 and its working contact, upper winding of relay 126, conductor 47, bank contact 32, Fig. 1, wiper 46, armature 45 and its working contact, resting contact and armature 44, control trunk conductor 43, resting contact and armature 415, Fig. 4, armature 416 and its resting contact, armature 417 and its resting contact, through the upper winding of relay 418 to battery. A further result of the energization of relay 126, Fig. 2, is the closing of a circuit through relay 131 by way of ,;armature 130. Relay 131, upon energizing, forms a locking circuit for itself, independent of relay 126, which may be traced from grounded release trunk conductor 42, armature 132 and its working contact, throu h relay 131 to battery. A further result of t e energization of rela' 131 is the opening of the circuit for the lbwer winding of relay 126 at armature 125, and the opening of the circuit for the stepping magnet 213 ofswitch M at armature 121. In order to insure the proper operation of relay 126, the spring adjustment is such that armature 127 will engage its working contact before armature 130 engages its working contact.

To return to the consideration of the trunk relay group D, Fig. 4, it ma be said that relay 418 will energize over t e previously traced circuit and operate to remove ground, by way of armature 422 and conductor 320, from the contacts associated with the trunk relay group D in the multiple test banks of the markers. A further result of the operation ofrelay418 is the grounding of the common start conductor leading to the marker distributer S Fig. 8. For the sake of explanation we may assume that the marker distributer has preselected the marker S as the next marker to now operate in the usual manner to seek an ungrounded contact in the test bank B. When the ungrounded test contact associated with the trunk relay group D is reached the switching relay 314 will energize and open the circuit of relay 313 at armature 312.

As relay 313 is slow to deenergize a circuit will momentarily be closed from ground, working contact and armature 316, working contact and armature 319, wiper 318 and the contact u on which it is now standing, marker re ease trunk conductor 320, armature 422 and its working contact, Fig. 4, through the lower winding of relay 423 to battery. Relay 423 will energize over the above traced circuit and will place ground upon marker release trunk conductor 320 by way of the resting contact controlled by armature 424 and the working contact and armature 425. This ground will maintain switching relay 314 of marker S energized after relay 313 has deenergized, and will also make the trunk relay group D busy in the .Inultiple test banks of the markers. A furbank'B of the marker distributer S whereupon the motor magnet 322 of marker distributer S will operate toadvance the marker distributer S into engagement with A still further result of the energization of relay 314 is the closure the next marker.

of a circuit from ground, working contact and armature 323, conductor 324, through the lamp 614, Fig. 5, to battery. A lamp is lighted whenever a marker is taken for use, i

contact associated with the marker S in A the bank B of the set-up control switch S A stillfurther result of the energization of relay 314 is the closure of a circuit from ground, working contact and armature 325, common starting conductor 326, through relay 327 of the set-up control switch S to battery. For the purpose of explanation we may assume that the set-up control switch S is at this time in connection with some marker other than the marker S The switching relay is therefore energized, and the encrgization of relay 327 is without effect because of the open circuit at armature 330. \Vhen the marker with which the switch S is in engagement completes its operation the switching relay 332 will deenergize, whereupon a circuit is closed from ground, working contact and armature 329, resting contact and armature 330, through line relay 331 to battery. Relay 331, upon energizing, will close a circuit for the switching relay 332 and the stepping magnet 333 in series at armature 334, and at armature 341 connects the wiper 335 to the junction of switching relay 332 and stepping magnet 333. The set-up control switch S will now operate in the usual manner to seek an ungrounded contact in the bank 13 When the ungrounded contact associated with the marker S is reached the switching relay 332 will energize and open the circuit of line relay 331 at armature 330. As relay 331 is slow to deenergize a circuit will momentarily be closed from ground, working contact and armature 334, working con tact and armature 336, armature 337 and its working contact, wiper 335 and the contact with which it is now engaged, armature 328 and its working contact, wiper 338 and the contact with which it is now engaged, conductor 339, through rela 426, Fig. 4, and the lower winding of re ay 418 to battery. Relay 426, upon energizing, will place ground upon conductor 339 by way of the resting contact controlled by armature 424, and the armature 427 and its working contact. This ground will maintain the switching relay 332 after the line relay 331 has deenergized.

A further result of the energization of relay 426 is the operation of holding relay 511. Fig. 6, over a circuit traceable from ground, working contact and armature 428, conductor 429, through relay 511 to battery. A still further result of the energization of relay 426 is the extension of the control trunk conductor 43 and the pulsing conductor 51 to the decoder D The extension of the control trunk conductor 43 may be traced from resting contact and armature 415, armature 416 and its working contact, conductor 430, through the low resistance relay 513. through the high resistance relay 512 to battery. The extension of the pulsing trunk conductor 51 may be traced from resting contact and armature 414, armature 413 and its working contact, conductor 431, through relay 514 to battery.

The operation just described causes the circuit of the upper winding of relay 126,

Fig. 2. to be opened. Relay 126. upon deenorgizing. closes a circuit traceable from ground. armature 130 and its resting contact, working contact and armature 136, through relay 137 to battery. Relay 13?, upon energizing, removes ground from certain contacts in bank B at armature 140, and extends conductor 129 by way of armature 128. A further result of the energization of relay 137 is the closure of a circuit from ground, through the constantly moving interrupter '1, armature 138 and its working contact, through pulsing relay 139 to battery.

Relay 139 will energize at the first impulse and will close a circuit through stepping magnet 143 of the sending switch S at armature 141, whereupon the stepping magnet 143 will energize. No movement of the wipers 135, 133 and 156 will take place at this time. A further result of the energizetion of relay 139 is the removal of ground from certain contacts in the bank B by way of armature 142, and the completion of the circuit from conductor 129 to Wiper 135 of sending switch S by way of armature 134.

At this time a circuit extends from relays 512 and 513, Fig. 6, over the control trunk conductor =3 to the wiper 133 of sending switch S. A circuit also extends at this time from relay 514, Fig. 6, over the pulsing trunk conductor 51 to the wiper 135 of the sending switch S.

When the interrupter T next opens the circuit of relay 139, the said relay will deenergize and open the circuit of stepping magnet 143, whereupon the wipers. 135, 133

and 156 will be advanced into engagement with the first contact in their respective banks. As the wiper 230 of the first digit register M is in second position, the first contact in bank B will be open and the control trunk conductor will be neutral. W'hen relay 139 energizes in response to the next impulse, the wipers of the sending switch S will not advance, but armature 134- will close the wiper 135 through to the pulsing trunk conductor 51. As the. wiper 232 of the first digit register M is in second position, the first contact in bank B" is open and there will be no circuit for relay 514, Fig. (3.

At the next deenergization of relay 139 the stepping magnet 143 will deencrgizc and advance the wipers 135, 133 and 156 into engagement with the second contact in their respective banks. As wiper 230 of the first digit register M is in second position. the second contact in bank li will be open and the control trunk conductor will be neutral. At the next energization of relay 13.), a. circuit may be traced from ground at wiper 232 of the first digit register M in second position, conductor 146, second contact in bank B", wiper 135, working contact and armature 134, and over the previously traced circuit to relay 514, Fig. 6.

ltlS

position, the third contact in bank B will be open and the control trunk conductor will be neutraL. At the next energization of relay 139, a circuit may be traced from ground at wiper 232 of the first digit register M in second position, conductor 146, third contact in bank B", wiper 135, working contact and armature 134, and over the previously traced circuit to relay 514, Fig. 6.

\Vhen the interrupter T next opens the circuit of relay 139, the said relay will deenergize and open the circult to relay 514, Fig. 6, and to the stepping magnet 143, whereupon the wipers 135, 133 and 156 will be advanced into engagement with the fourth contact in their respective banks. A circiut may be traced, however, from ground, resting contact and armature 142, fourth contact of bank B wiper 133, and over the previously traced circuit to relays 513 and 512, Fig. 6. At the next energization of relay 139 the above circuit will be opened at armature 142, but as the fourth contact in bank B" is open there will be no circuit established at this time for relay 514, Fig. 6.

The transmission-of the code train representing the digit 2 is now complete. It consisted of two grounded impulses over the pulsing trunk conductor, during a period in which the control trunk conductor was neutral. This was followed by a single grounded impulse over the control trunk conductor. The operation of the decoder I) in response to the above code train will now be explained.

As a result of the first code train, relays 512 and 513, Fig. 6, will remain at normal while relay 514 will momentarily operate its armature two times. At the first energization of relay 514, a circuit may be traced from ground, working contact and armature 515, armature 516 and its working contact, armature 517 and its resting contact, armature'518 and its resting contact, armature 519 and its restingscontact, armature 520 and its resting contact, through the left hand winding ofrelay 521 to battery. The structure of relay 521 is such that the energization of its left hand winding will operate armature -'522, but will not operate armatures 520 and 523. lVhen relay 514 next deenergizesfa shunt will be removed from around the right hand winding of relay 521, whereupon the said relay will be completely energized over a circuit traceable from ground, Working contact and armature 524,

conductor 525, armature 522 and its working contact, through the two windings of relay 521 in series to battery. A further result of the energizationof relay 521 is the extension of display conductor 526, through the working contact and armature 523, conductor 527, to the right hand winding of relay 611, Fig. 7.

At the next energization of relay 514, a circuit is closed from ground, working contact of armature 515, armature 516 and its working contact, armature 517 and its resting contact, armature 518 and its resting contact, armature 519 and its resting contact, armature 520 and its working contact,

armature 528 and its resting contact, through the left hand winding of relay 529 to battery. Relay 529 will only operate armature 530 at this time, but when relay 514 deenergizes it will remove a shunt from around the right winding of relay 529, whereupon the said relay will become full operated from ground on conductor 525 by way of armature 530. A further result of the energization of relay 529 is the extension of display conductor 526, through the working contact and armature 543, conductor 544, to the right hand winding of relay 612, Fig. 7. The ground impulse delivered over the control trunk conductor causes the energization of both relays 512 and 513. The en ergization of rela 513 is without effect at this time, but re ay 512, upon energizing, completes a circuit from ground, working contact and armature 515, working contact and armature 531, armature 532 and its resting contact, through the left hand winding of relay 533 to battery. Relay 533 will only operate armature 534 at this time. When relay 512 deenergizes following the next energization of relay 139 of the sending switch S, it will remove a shunt from around the right hand winding of relay 533 upon the said relay will become fully operated from ground on conductor 525, by Way of armature 534. A further result of the en'ergization of relay 533 is the transfer of the o crating conductors to the second setup re ay group SR Returning to a further consideration of the sending switch S, Fig. 2, it may be said that at the next deenergization of relay 139, the stepping magnet 143 will deenergize and advance the wipers 135, 133 and 156 into engagement with the fifth contact in their respective banks. A circuit may now be traced from ground at wiper 233 of the second digit register M in fourth position, resistance 251, conductor 147, fifth cont-act -in bank B, wiper 133, over the previously traced circuit to relays 512 and 513, Fig. 6. At the next energization of relay 139, a circuit may be traced from ground at wiper 235 of the second digit register M in fourth position, conductor 148, fifth conwheretact in bank B", wiper 135, working contact and armature 134 over the previously traced circuit to relay 514, Fig. 6.

At the next deenergization of relay 139, the circuit to relay 514, Fig. 6, will be opened, while the stepping magnet 143 will dcenergize and advance the wipers 135, 133 and 156 into engagement with the sixth contact in their respective banks. As the fifth, sixth and seventh contacts in bank B are in multiple, the circuit is still maintained to relays 512 and 513, Fig. 6. It may also be said that the wiper 133 engages the next contact in the bank before breaking connection with the preceding contact, thus the circuit to relays 512 and 513 is not opened as the wiper 133 advances from contact to contact. When relay 139 energizes in response to the next impulse, the wipers of the sending switch S will not advance, but armature 134 will close the wiper 135 through to the pulsing trunk conductor 51. As the wiper 235 of the second digit register M is in fourth position, the sixth contact in bank 13 is open and there will be no circuit for relay 514, Fig. 6.

At the next deenergization of relay 139, the stepping magnet-143 will deenergize and advance the wipers 135, 133 and 156 into en gagement with the seventh contact in their respective banks. As the fifth, sixth and seventh contacts in bank B are in multiple the circuit is still maintained to relays 512 and 513, Fig. 6. When relay 139 energizes in response to the next impulse, the wipers of the sending switch S will not advance, but the armature 134 will close the wiper 135 through to the pulsing trunk conductor 51. As the wiper 2350f the second digit register M is in fourth position, the sixth contact in bank B" is open and there will be no circuit for relay 514, Fig. 6.

\Vhen the interrupter T next opens the circuit of relay 139, the said relay will deenergize and open the circuit of stepping magnet 143, whereupon the wipers 135, 133 and 156 will be advanced into engagement with the eighth contact in their respective banks. As the eighth contact in bank 13" is open, there will be no circuit at this time for relay 514, Fig. 6. A circuit may be traced, however, from ground, resting contact and armature 142, eighth contact of bank 13", wiper 133, and over the previously traced circuit to relays 513 and 512, Fig. 6, thus replacing the ground previously supplied through the resistance 251, Fig. 3. At the next energization of relay 139, the above circuit will be opened at armature 142.

The transmission of the code train representing the digit 4 is now complete. It consisted of one grounded impulse over the pulsing trunk conductor, during a period in which the control trunk conductor was grounded through a high resistance. After the impulse was delivered the high resistance ground upon the control trunk conductor was momentarily replaced by direct ground, after which the said trunk was cleared. The operation of the decoder D in response to the above code train will now be explained.

As a result of the second code train, relay 512, Fig. (3, will be maintained in an operated position while relay 514 momentarily operates its armature. The low resistance relay 513 will not operate at this time due to the high resistance in the circuit. \Vhen relay 514 energizes, a circuit may be traced from ground, working contact and armature 515, armature 516 and its working contact, armature 517 and its resting contact, armature 518 and its working contact, armature 535 and its working contact, armature 536 and its resting contact, armature 537 and its resting contact, through the left hand winding of relay 538 to battery. Relay 538 will only operate armature 539 at this time, but when relay 514 dcenergizes, it will remove a shunt from around the right hand winding of relay 538, whereupon the said relay will become fully operated from ground on conductor 525 by way of armature 539. A further result of the energization of relay 539 is the extension of display conductor 526 through the working contact and armature 545, conductor 546, to the right hand winding of relay 613, Fig. 7.

The grounding of the control trunk conductor through a high resistance will cause the energization of relay 512, whereupon a circuit is closed from ground, working contact and armature 515, working contact and armature 531, armature 532 and its working contact, armature 547 and its resting contact through the left hand winding of relay 548 to battery. Relay 548 will only operate armature 549 at this time. It will be remem bered that the wiper 133 of sending switch S placed direct ground upon the control trunk conductor when it advanced to eighth position. This direct ground not only maintains the circuit of relay 512, but also causes the operation of relay 513, which is without effeet at this time. When relay 512 deenergizes, following the next energization of relay 139 of the sending switch 5, it will remove a shunt from around the right hand winding of relay 548, whereupon the said relay will .become fully operated from ground on conductor 525 by way of armature 549. A further result of the energization of relay 548 is the transfer of the operating (glflllCtOIS to the third set-up relay group Returning to a further consideration of the sending switch S, Fig. 2, it may be said that at the next deencrgization of relay 139 the stepping magnet 143 will deenergize and advance the wipers 135, 133 and 156 into en-

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