US1451885A - Private-branch-exchange system - Google Patents

Description

- Apr. 17,

M. L. NELSON PRIVATE BRANCH EXCHANGE SYSTEM 2 Sheets-Sheet l fnusnfuz" MEFZZZ'LL. EZE'C/Z'l Original Filed July 9 1917 Apr. 17, 1923.

M. L. NELSON PRIVATE BRANCH EXCHANGE SYSTEM 2 Sheets-Sheet 2 [UL/517227.2- Z7.L.NEZ5UZ'L MEPZZ' Original Filed July 9 1917 Patented l7, lhlildl MARTIN L. NELSON, OF CHICAGO, ILLIENOIS, .AiSSIGNOR TD AUTOMATIC? ELECTRIC COMPANY, 633 CHICAGO, ILLIHQIS, A GOB'POEATIUN OF ILLINOIS.

PBIVATE BBANEEEEXCHANGE SEE'STEM.

Application filed July $3, 191?, Serial No. 179,327.

- themselves bymeans of automatic switching mechanisms, such an exchange constituting what is commonly known as a private automatic exchange, or P. .1 X. These exc ranges are usually installed in factories or business establishments of various kinds and, as in the GilllJOCliIl'lGllt herein disclosed may consist f substations in each department and o'liice of the establishn'ient, and a switchboard comprising li or trunk selecting switches individual to the lines and a suitieient number of connector switches to handle the maximum number of simultaneous calls. In an installation of this kind there are always a number f individuals, such as a general foreman or superintendent, for ex ample having duties of a supervisory nature which often take them on inspection trips through the different departments. Unless these trips are made in accordance with a regular schedule which. is seldom possible or even desirable, these individuals when so engaged will be bereft or telephone service so far as incoming calls are concerned. is true of course that an oiiicial by goin to some trouble could notify his home station when he left for a different department and thus keep an attendant there posted as to his whereabouts but this plan would be inconvenient, and by my invention no such cumbersome arrangement is required.

llriefly stated the object of my invention is to provider. specialcode ringing andintercommunicating circuit whereby certain (licials may be reached when they are absent from their offices on business in other departments. I provide a special bell in each department, all oi which bells are connected in multiple across a common signaling circuit. Automatic code ringing" equipment is provided adapted to close the commonsig' naling circuit in accordance with p: deter minedcodes, one of which is assigned to each Renewed November 1?,1921. Serial No. 515,972.

fficial to whom special service is to be given. r tcertainset oi contacts-in the connector banks is to be used for the special signaling and thetelephone number associated therewith may be termed the special call nun her. it person who desires to commi iicate with an otlicial who is temporarily aliisent in some unknown department will call the special call number, thereby extending a connection to the code ringing equipment. One or more additional digits are now called in order to set the ringing equip ment for the code ring ofthe particular 0 -ial wanted; whereupon'all the special bells are rung in parallel in a distinctive manner which will be heardand'recognized by the desired party wherever he happens to bc.' There is also a seccn'dset oi bank contacts set aside for use in thiscounection', and upon perceiving: his signal the called party will turn to the nearesttelephone and a l the number corresponding to this second set of contacts, which 1 term the answer number; The two sets of bani: contacts are tied together s that by this operation the calling; and called parties willbe telephonically connected. Conversation may be held overthecircuitthus established; or in case anextended conversation is desired, one of the parties willgive the other his telephone number, which may be called in the usual w: thereby "freeing the code ringing'equip for use by someone else.

The foregoing; is a brief statement oi the object and scope of the invention The preferred manner of carrying out the same, and the apparatus involved. will be described and explained fully hereinafter, reli'erence being had to the accompanying drawings, which show the essential features of a private automatic exchange embodying the principles of the invention.

- 1 shows diagxrammatically the circuits of two substations associated with two connectors in a manner to best illustrate my invention. I

2 shows diagrammatically a code A 7 ng equipment and the controlling circuit therefor, arranged to function properly with circuit of Fi 1.

Referring to r, the substation A may be of any suitable automatic type sucln for enan l as the substation d' \losed in British parent to Martin No. Z-zll9 of 1910. As shown herein itconsists essentially of a receiver 2, the transmitter 3, switch hook 4, ringer 5, and condenser 6. Being an automatic substation there is also provided a pair of impulse springs 7 and 8 which are controllable by the impulse wheel 9 through the medium of the finger hole dial (not shown).

The line conductors 121 and 13 terminate at the exchange in the individual line switch C, which may be briefly described as a rotar line switch whose wipers have no norma position. A line switch of this character is shown in the patent to Lamb, No. 1,193,160granted August 1, 1916.

The'line switch C and a plurality of similar line switchesmay be given access to a group of trunk lines, each of which extends to and terminates in a connector switch. One of the trunk lines to which the line switch C has access is shown in the drawing as terminating in the connector E, which may be of the general type of connector shown in Patent No. 815,17 6, granted March 13, 1906 to Keith, Erickson and Erickson. The side switch and private magnet are omitted, however, and the circuits are modified in accordance with the two-wire system of control. These circuit changes, although forming no part of my invention, will be explained fully hereafter during the description of the operation of the invention.

In the lower half of Fig. 1 .I have shown a substation A, an individual line switch C, and a connector E, which are in all respects similar to the substation A and the switches C and E respectively.

It will be understood that the connectors E and E are two of a group of connectors which are used for the purpose of interconnecting calling and called lines in the usual manner. The banks of all the connectors of the group are, of course, connected in multiple and form terminals of normal conductors extending to the individual line switches associated with the lines of the system. This multipling of the banks is not shown in the drawings, but is understood to be in accordance with the usual practice. In brief, the private automatic exchange in connection with which I have chosen to illustrate the invention, comprises a plurality of substations including the substations A and A, a plurality of individual line switches, such as the line switches C and C, and a group of connectors accessible to all the line switches in common. A calling subscriber upon removing his receiver operates his in dividual li'ne switch in order to select and extend connection to an idle connector switch, and the selected connector is thereafter directively controlled to connect with the normal conductors associated with a desired called line.

I It has been mentioned before that a certain set of contacts in the connector banks is set aside for extending connection to the special code ringing equipment. While any set of contacts may be thus reserved, I prefer to use the last set in some particular level and in the following it will be assumed that the last set of contacts in the seventh level is reserved for this purpose. The special call number therefore, will be the number 70. In this connection attention should be called to the fact that each connector is provided with a set of special rotary ofl normal springs which, in the case of the connector E, are the springs 65, 66, and 67. The spring 67 is normally in engagement with spring and is adapted to be shifted into ei'igagement with spring 66 by the rotary cam 7 5 when the connector is operated in accordance with the number 70. There'is also a set of contacts set aside for answering, to be called when a party is responding to his code rin and it will be assumed that the contact set reserved for this purpose'is the ninth set of contacts in the seventh level. It

follows that the special answering number will be the number 7 9. Both sets of contacts are multipled'as usual through the group of connectors. In addition the contact set corresponding to the call number 70 is multipled with the contact set corresponding to the answering number 7 9. This is shown in the drawing as will now be pointed out. The contact set associated with connector E,

comprising bank contacts 93, 94, and 95, is

the last or tenth contact set in the seventh level, while the contact set associated with connector switch E is the ninth set of contacts in the seventh level. The line contacts 93 and 95 are connected by means of conductors 7 6 and 77 with line contacts 193 and 195. It will be observed that these conductors are transposed so that the upper line contact 98 is multipled with the lower line contact 195, while the lower line contact 95 is multipled with the upper line contact 193. The private or test contacts 94 and 194 are not multipled excepting, of course, for the usual multiple to corresponding contacts in the different connectors of the group.

From the test contacts 94 and 194 and the line contact 95, respectively, conductors 96, 97 and 98 extend to a group of relays which are indicated collectively by the reference character H, Fig. 2. These relays have the function of controlling the rotary switches M and N in a manner which will be described fully hereinafter. The rotary switch M may be termed a code selecting switch and comprises essentially a stepping magnet 113 and the four wipers 115 to 118, inclusive,

with their associated sets of bank contacts.

The switch M may be similar in construction to the rotaryline switch C, Fig. 1, although, of course, the circuits are altogether different because of the different operations which the switch has to perform. The rolOO menses tary switch N is similar to the rotary switch M but has only two wipers 119 and 120. The stepping magnet for the switch N is indicated by the numeral 111. The switch N may be termed a ringing switch and its function is to close the common signaling circuit in accordance with the code selected by the switch M. This circuit is closed over the conductor 121 which extends to the relay 122. When energized the relay 122 connects the generator Genoss the conductors 123 and 124; which extend to all the offices or departments of the business establishment in which the system is installed. As before explained, a signaling device or ringer is connected across these conductors in every department. Three oi these ringers are shown in the drawings and are indicated by the reference characters R, It, and R The bank wiring between the switches M and N will notbe explained in detail just now, but will be described in the course of the description of the operation While I have shown throughout the drawings a plurality of batteries it will be understood that there is preferably but one battery having its positive pole grounded. In order not to encumber the dr; wings separate rei erence characters have not been applied to the separate batteries, but it will be understood that when, in the description of the operation, a circuit is traced to battery it extends to the live or ui'igrounded pole of central battery. The busy signaling machine Q and the intermittent ringing equipment I R shown in Fig. 1 are of the usual type common in other well known automatic e2;- changes.

I-laving given a brief description of the apparatus involved, I will now proceeo to describe more in detail the operation of? the system. For this purpose it will be assumed that the subscriber substation L. i

i n new desires to communicate with an oflicial X who is known to be temporarily absent from his oflice. Usually the subscriber at substation will have ascertained this fact by calling X at his office in the usual manner. However, this is of no importance for it is sufficient for present purposes to assume that X is at some unknown point in the establishment and that in order to communicate with him it will be necessary to use the special call system provided by my invention. The subscriber at substation A will theretore remove his receiver and operate his calling device in accordance with the digits oi the call number 70.

Upon removal of the receiver a circuit is completed for the line relay of the line switch C as follows: ground at 1. resting contact of armature 1S and said armature. line conductor 13, substation A line conductor 12, armature and its resting contact, and the winding of line relay lfi to the closeof the above circuit, the line relay connects the private or test wiper 31 to the junction point 24 as follows: test wiper 31, armature 19 and its resting contact, armature 22 and its working contact, to junction point 2 1. It is understood that the wipers of the line switch are normally in engagement with some contact set in the bank and the operation now depends upon whether the contact set upon wiich the wipers are resting is busy or not. If this contact set is busy the test contact which is engaged by the test wiper 31 will have a ground potential upon it, resulting in the energization of the stepping magnet .17 and the short circuiting ot' the relay 16. By the operation of the stepping magnet 17 the switch wipers are advanced to the next contact set, and since the stepping magnet interrupts its own circuit, the advance of the wipers will be continued through the vibratory operation of the stepping magnet as long as the test wiper 311 continues to engage grounded or busy test contacts. When an idle or ungrounded test contact is reached, which we will assume to be the test contact 34. the operation of the stepping magnet will cease, and the relay 16, being no longer short circuited, will be energized over the previously described circuit extending from ground G The resistance of relay 16 is suiiiciently high to prevent the stepping magnet 17 from energizing over this circuit.

By the operation of the relay 16 the test wiper is connected to the winding of the said relay at its armature .19; and at armatures 20 and 18 the line conductors 1.2 and 13 are disconnected, respectively. from the winding of the line relay 15 and from ground G. and are extended by way of line wipers and 32 and bank contacts 33 and to the windings of the double wound line relay of the connector E.

The line relay 10 is accordingly energized in the usual manner over the calling subscribers loop. and completes the usual circuit for the slow acting release. relay 41. Upon attracting its armatures relay s1 prepares the usual circuit for the vertical and rotary magnets 48 and 4-9 (at lower armature 52) and at its upper armature 78 closes a holding circuit for the relay 16 of line switch G which may be tracedas follows: ground at G working contact of armature T2 and the said armature. banl contact 3%, test wiper 31. armature 19 audits working contact, winding of relay 16, and winding of magnet 17 to battery. 11. branch of the above circuit extends from junction point till by way of private normal conductor 27 to multiple test contacts in the banks of the connectors where, by a, ground potential on these test contacts, the line of substation A is made busy.

The foregoing operations have occurred automatically in response to the removal of the receiver at substation A- The calling subscriber may now operate his calling device in accordance with the first digit of the call number which is the digit 7. lVhen the calling device is operated the impulse springs "i" and 8 are separated momentarily seven times, producing a corresponding series of interruptions in the circuit of the line relay of the connector E. In response to these interruptions of its circuit the line relay 40 is deenergized a number of times and at each deenergization transmits an impulse to the vertical magnet 48 over the following path: ground at G armature 51 and its resting contact, armature 52 and its working con tact. off normal springs 59 and 58, winding of the low resistance slow acting relay 42, and the winding of the vertical magnet 48 to battery. In response to these impulses the vertical magnet is operated to raise the switch shaft step by step until the wipers 90, 91, and 92 stand opposite the seventh horizontal level of bank contacts. The slow acting relay 42 is energized in series with the vertical magnet and retains its armature attracted during the series of impulses, thereby preventing the opening of the vertical magnet circuit at the off normal springs which are shifted as soon as the switch shaft leaves its normal position.

The calling subscriber may now call the final digit of the special call number, which is the digit 0. As before, by momentary separations of the impulse springs 7 and 8, a series of interruptions is produced in the circuit of the line relay 40. Now, however, the off normal springs being in the position shown in the drawing, and the relay 42 having deenergized, the line relay transmits a series of impulses to the rotary magnet 49, the circuit being as follows: ground at G armature 51 and its resting contact, armature 52 and its working contact, oif normal springs 59 and 57, armature 53 and its resting contact, winding of low resistance slow acting relay 45, resting contact of armature 72 and the same armature, armature 54 and its resting contact, and the winding of the rotary magnet 49 to battery. The rotary magnet is operated in response to these impulses to rotate the switch shaft until the wipers 90,91, and 92 are brought to rest in engagement, respectively, with bank contacts 93, 94, and 95, which bank contacts comprise the tenth set of contacts in the seventh level. The slow acting relay is energized in series with the rotary magnet 49 and maintains its armatures continually attracted during the rotation of the switch. At its lower armature 60 relay 45 disconnects the test wiper 91 from thelower winding of relay 46 and connects it instead by way of spring 70, resistance 47, and the resting contact of armature 60 and said armature, to the upper winding of the combined test and answering bridge relay 43. The momentary cnergizations of relay 43 due to the test wiper 91 passing over busy or grounded test contacts, if there be any such in its path, are of no consequence because of the alternative circuit for the rotary magnet by way of armature 68 of relay 45 and its working contact. The connector wipers having been rotated into engagement with the set of bank contacts corresponding to the special call number, the operation now depends upon whether the special code ringing equipment associated with that set of con tacts is busy or not. In order to explain the operation of the connector E in calling a busy line, it will first be assumed that the special ringing equipment is busy. Under these circumstances, there will be a ground potential on the test contact 94 and when the connector wipers are rotated into engagement with bank contacts 93, 94, and 95, relay 45 being energized during the rotation as before described, as soon as the test wiper 91 arrives at the test contact 94 the relay 43 will be energized over tne circuit previously traced with the following results: At the resting contact of armature a contact in the circuit of the lower winding of relay 46 is opened and at the working contact of the same armature relay 43 prepares a locking circuit for itself which is completed upon the deenergization of relay 45 an instant later, and which extends as follows: ground at G working contact of armature 78 and the said armature, conductor 79, armature 55 and its working contact, contact point 71, spring 70, resistance 47, resting contact of armature and said armature, and the upper winding of the said relay 43 to battery. In addition, the circuit of the rotary magnet 49 is opened at the resting contact of armature 54 and at the working contact of armature 56, a lead from the busy signaling machine Q, is connected to the lower heavy line conductor in order to notify the calling subscriber that the attempted connection cannot be obtained. He will accordingly replace his receiver, whereupon the automatic switches C and E are restored to normal condition in a manner which will be hereinafter described.

Having explained briefly how the connector E operated when a busy line is called, I will now return to where it was explained how in responseto the final series of impulses the switch wipers were rotated on to the bank contact set corresponding to the call number 70, and from this point the regular operation will be proceeded with. If there is no ground potential upon the test contact 01, when the slow acting relay 15 deenergizes at. the end of the final series 01? impulses the following energizing circuit is completed for the switching relay ground at G working contact o1 armature 78 and the said armature, condrwtor '70, armature 553 and its resting contact, lower winding of relay 16, resting contact 01 arnia ture 09 and the said armature, test wiper 01., test contact as, conductor 96, armature 105 and its resting contact, and the winding 01? relay 102 to battery. Upon the closure of r the above circuit relays 16 and 102 are energized in series. As a result of the energization of the former relay at resting contact of armature T2 the circuit of the rotary magnet 419 is opened, and at the workingcontact of the same armature a circuit is prepared tor the ring cut off relay 414. As a further result of its energization, relay 4E6 closes a contact in the lower heavy talking conductor at its armature 74:, and at its armature 73 short circuits its lower winding and completes a locking circuit for itself by way oi? its upper winding, the circuit being traceable as follows: ground at G working contact; of armature 78 and the said armature, conductor 79, armature 73 and its two working contacts to the upper winding of the said relay 16 and to the test wiper 91. By the connection of direct ground to the test contact 9 1 and its multiples, the special ringing equipment is made busy in the banks oi the remaining connectors of the group. The operation of relay 102, Fig. 2, which it will be remembered was energized in series with the relay 4:6 01 the connector, is without particular function just at this time.

The connection. has now been extended to the trunk line terminating in the special ringing equipment shown in Fig. 2, and the apparatus is in readiness for the transmis sion of setting impulses to code selector M. The calling subscriber is, of course, acquainted with the code ring which has been assigned. to the wanted party X, and knows, also, what digit is now necessary to be called in order to operate the code selector 1W1 for the purpose of selecting this particular code ring. -We will assume that the code ring used tor signaling X is one long and one short. and that thecode selector M is so wired that in order to select this particular code ring, the digit five must be called. The calling subscriber will, therefore, operate his calling device in accordance with this digit, thereby producing as before, a series 0t interruptions in the line circuit and a corresponding series of deenergizations of the line relay 10. These deenergizations of the line relay are at this time ineffectual to cause any Further operation of the connector E for the rotary magnet circuit has been opened,

as before explained, at the resting contact of the armature It has been explainedbetore, however, that when the connector E is operated. in accordance with the number the rotary 011' normal springs 65, 66, and 67 are shifted, and since these springs, therefore, will now be in the position shown in the drawing, the deenergizations of the line relay now result in the transmission of a series of impulses to the stepping magnet 113 of the code selectorM, the circuit being as follows: ground (i armature 51 and its resting contact, armature 52 and its working contact, oft normal springs 59 and 57, armature 53 and its resting contact, rotary oft normal springs 66 and 67, resting contact of armature 63 and the said armature, armature 7 1 and its working contact, wiper 92, hank contact 95, conductor 98, armature 106 and its resting contact, armature 108 and its resting contact, winding o1 low resistance slow acting relay 103, and the winding of the stepping magnet 113 to battery. Five impulses are transmitted to the stepping magnet 113 over the above circuit and the switch wipers 115 to 118, inclusive. which normally rest in engagement with the first contacts in their respective banks, are advanced live steps to the position shown in the drawing. Relay 103 is energized in series with the stepping magnet 113 and being slow acting retains its armature during the series of impulses. At the end of the series of impulses relay 103 deenergizes and connects ground G to the Wiper 115, thereby closing an energizing circuit for the relay 101 as tollows: ground G, resting contact of armature .111 and the said armature, wiper 115 and the ban; contact engaged thereby, conductor 13 1, and the winding of relay 101 to battery. Upon energizing, relay 101 prepares a circuit tor the relay 100 at its arma-- ture 107 and at its armature 108 opens the circuit of the stepping magnet 1113. A branch of the energizing circuit of relay 101 may be traced to relay 104: as follows: junction oint 136, armature 110 and its working contact, interrupter contact otthe steppi g magnet 114 of ringing switch N. and the winding of the stepping relay 104: to

battery. Upon energizing, relay 1041 completes an extension of the above traced branch as follows: junction point 137, ar-

mature 112 and its working contact, and the winding of stepping magnet 114 to battery.

The stepping magnet 1141 is accordingly energized and by its operation the wipers 119 and 120 of the ringing switch N are advanced one step. Near the end of its stroke the magnet 1141 opens the circuit of the stepping relay 10 1 which is thereupon deenergized and opens the circuit of the stepping magnet. A vibratory action is thus set up between the stepping relay 104: and the stepping magnet 11-1, whereby the wipers 119 and 120 are advanced step by step into engagement with successive contacts in their respective banks, and it will be evident that this operation will continue as long as a ground potential is maintained upon the junction point 137.

hen on its second step the wiper 120 arrives at the contact 140 a circuit is completed for the relay 122 as follows: ground at G, resting contact of armature 111 and the said armature, wiper 115 and the bank contact engaged thereby, conductor 133, wiper 120, bank contact 140, conductor 121, and the winding of the said relay 122 to a battery. Upon energizing, relay 122 bridges the generator Gren across the two conductors 123 and 124, thereby operating the ringers R, R R and all other ringers similarly connected. When the wiper 120 reaches contact 141 on the third step the circuit of the relay 122 isnot interrupted, but is maintained closed over the following path: grounded wiper 120 by way of bank contact 141, conductor 125, bank contact engaged by the Wiper 118 and the said wiper, conductor 132, conductor 121, and winding of relay 122 to battery. Obviously, the above circuit will continue to be closed while the wiper 120 is passing bank contact 142. During the time that the wiper 120 is in engagement with the contact 143 the circuit of re lay 122 is closed over the path originally described. While the wiper 120 is in engagement with contacts 144 and 145 the circuit of relay 122 is still maintained closed over the following path: grounded wiper 120, contact 144 or 145, conductor 126, contact engaged by the wiper 117 and the-said wiper, conductor 132, conductor 121, and the line relay 122 to battery. It will be evident, also, that While the wiper 120 is in engagement with bank contact 146, the circuit will still be closed as originally. Thus it will be seen that the circuit of the relay 122 will be closed continuously while the wiper 120 is passing contacts 140 to 146, inclusive, thereby producing a long closure of the common signaling circuit. But while the wiper 120 is passing contacts 147 and 148 the circuit of the relay 122 is interrupted, for it will be seen when tracing the circuit that none of the contacts to which the conductor 127 is multipled in the bank of the code selector M is engaged at this time by the wiper 116. The relay 122 is accordingly deenergized while the wiper 120 is passing contacts 147 and 148. When the contact 149 is reached the circuit of the relay 122 is again completed as originally described, and since the circuit is interrupted again upon the arrival of wiper 120 at contacts 150 and 151 the relay 122 is energized only momentarily to produce a short closure of the signaling circuit. As the wiper 120 continues its rotation and successlvely engages the remaining cont/ads in its bank, it produces no further operations of the relay 122, as may be readily ascertained by tracing the circuit connections of the remaining contacts. After completing one revolution the wipers of the switch N immediately start on another, and it follows that the signaling operation just described will be repeated at intervals.

When the called party X hears one of the special bells ringing in accordance with his code he will step to the nearest telephone, which we will assume to be the substation A, and call the answering number 79. Upon the removal of the receiver at the substation A the line switch C is operated automatically the same as was described in connection with the line switch C to select and establish connection with a trunk line extending to an idle connector switch. Assuming that the selected connector isthe connector E, when the calling device at substa tion A is operated in accordance with the digits of the number 79, the connector E will be operated under control of its line relay 180 to raise and rotate its wipers 190, 191, and 192, until they come to rest in engagement with the bank contacts 193, 194, and 195, respectively. The connector E operates precisely like the connector E, and therefore the manner in which the above connection is established will not be described in detail. WVhen the slow acting relay 186 deenergizes at the end of the rotation, a circuit is completed for the switching relay 185 as follows: ground at G, working contact of armature 181 and the said armature, conductor 182, armature 183 and its resting contact, lower winding of relay 185, resting contact of armature 179 and the said armature,

test wiper 191, test contact 194, conductor 97, and the winding of relay 100 to battery. Relays 185 and 100 are energized in series on the closure of the above circuit and the en ergization of the former relay has the usual results among which may be mentioned the preparation of an energizing circuit for the ring out 01f relay 187 at armature 178, and the grounding of test wiper 191, and the closure of a locking circuit through the upper winding of the said relay 185 at armature 184. The lower line wiper 192 is also connected at the working contact of armature 177, whereby an energizing circuit is completed for the ring cut off relay 44 of connector E as follows: ground at G or G, .depending on the position of the intermittent ringing equipment I R, generator Gen or the booster battery, conductor 176, rotary off normal springs 175 and 174, resting contact of armature 173 and the said armature, armature 177 and its working contact, wiper 192, bank contact 195, conductor 77, bank contact 93, wiper 90, lower wind ing of the ring cut off relay 44, working con-- tact of armature 72 and the said armature,

iii)

armature and its resting contact, and the winding oi the rotary magnet 19 to battery. Upon the closure of the above circuit the ring cut oil relay is energize-ll. the rot magnet 49 remaining inoperative, r: armature 61 completes a loosing itself as tollows: ground atG working contact ot armature '78 and the said armature. conductor 79, armature S1 l its we contact, and the upper windi oi the said relay t-lto battery. As a in ier result oi its energization relay extends the app 1' and lower heavy talking conductor oy or its armatiu-es 60 and 63 through to the line wipers QOand 92, respectively. An energizing circuit for the ring cut oil relay 187 of the connector E may nowbe traced over the following path: groundat G working contact armature 78 and the said armature, conductor 79, armature 61 and its working contact, lower winding of relay a3, spring 62, armature armature 7-1.- and its working contact, wiper 92, bani: contact- 95, conductor 76, bank contact 193, wiper 190, lower winding ot ring cut'ott relay 187, working contact ct armature 178 and the said. armature, armature 172 and its resting contact, and the winding of the rotary net 171 to battery. Current flow in the above circuit brings about the energization o1 relay 187 with results similar to those de scribed in the case of the ring cut oil relay 14 of connector ll including the extension of the heavy talking conductors by way of armaeurcs 188 and 173 to the wipers 190 and 192. The complete talking circuit between the substations A and A has now been established The transmitters at the two substations are supplied with talking cur-- rent through the windingso'l the line relays ll) and 180, respectively, while the voice currents take the path shownin the heavy lines. The back bridge relays i and 170 which supply talking current to the called subscribers in ordinary connections will evidently be' energized in series, but have no battery supplying function in a connection of this character. It will be seen that the automatic operation of the ring cut oh relays in the two connectors is due tothc transposition of the conductors76 and 77 which'has been before mentioned, and it may be stated that these conductors are reversed especially for this purpose.

lie-turning to the re ay Hit), Fig. .2, which, it will be recalled, was cnei.'.fize(l in SONGS 1th the relay 185 of connector E, the operation of this relay opens the circuit of the stepping magnet 11 at a new point, (armature .106), and also serves to lisconnect the CODClUCiZOI" 96 u the winding of relay 102 and connect it instead direct to ground at the working contact of :11 ature 105. l" 102 does not deener eize once, however, hut is held'up tempo'arilyfover the lay 41-1.

following circuit ground at G, resting con tact of armature 111, wiper 115 and the eon-- tact engaged thereby, conductor 183, wiper 119 of the rotary switch it and the contact engaged thereby, conductor 138, and the winding oi relay 102 to battery. As soon 'as the switch N completes its revolution the above circuit will be broken, for the first contact of thebank associated with wiper 119 is not in multiple with the remaining contacts. Relay 102 is therefore deenergized with the following results: At the rest ing contact of armature 110 a circuit is completed for the stepping magnet 11?) for the purpose of restoring the code selecting switchM to normal position, and at the resting contact of armature 109 an auxiliary energizing circuit is completed for the relay 100 in order to maintain this relay energized and the contact sets 70 and 79 busy in case the subscribers should hang up their receivers before the code selector M had reached its normal position. The circuit oi the stepping magnet 113 mentioned above may be traced as follows: ground at G", resting contact of arn'lature 111 and the same armature, wiper 115' and contacts engaged. thereby, conductor 13%, armature 110 and its resting contact, interrupter contact of the stepping magnet 113, and winding of said magnet to battery. Since the above. circuit includes the interrupter contact of the stepping magnet, the said magnet willoperate intermittently to advance the switch wipers step by step to complete the revolus tion, the operation of the stepping magnet ceasing only when the wiper 1.15 arrives at the first/contact in its bank. When this has occurred the circuit of the stepping mag; net has been opened. in an obvious manner, and also the circuit of rela 101. this relay being rleenergized to open the above mentioned auxiliary energizing circuit for relay 100. p

Referring to the talking conncmion which has been established through the medium 0? the apparatus shown in Fig. 1, when a con versationis finished both parties will replace their receivers. At the replacement of the receiver at substation A the circuit of the line relay is broken resulting in the do eoergization oi the line relay and also in the deenergi ntion of the slow acting release re- By this operation the circuit of the release magnet closed as follows: ground at G armature 51 and its resting contact, armature and its resting contact, lower oft normal springs, and the winding of said release magnet 50 to battery. The operation of the release magnet is effective to restore the connector to normal position in the usual manner, its circuit being broken by the off normal springs when the switch shaft reaches its lowest position. As a furtl'ier result ot the deenergiaation of the release relay'41 ground G is disconnected from the holding circuit extending back to the relay 16 of the individual line switch (I Belay 16 accordingly deenergizes to restore the circuit of the line switch to its normal condition. The connector E and line switch C are released in the same manner a result of the replacement of the receiver at the substation A. All or the apparatus involved in the connection has now been restored to normal in readiness for other words In View of the preceding explanation it is believed that the operation of the code selector M and the ringing switch N insignaling in accordance with the other codes will be understood without goin any further into details. While a variety of wiring schemes may be used for selecting the various code rings, the one which has been worked out is comparatively simple and is appended below in the form of a table for the benefit of those who may wish to practice the invention:

ga S1gnal code.

701 l 1 long 702 2 long 703 4 short 704 5 short 705 1 long and 1 short 706 1 short and 1 long 707 1 long and 2 short 708 1 long and 3 short 4 709 1 long, 1 short and 1 long 7001 2 short and 1 long 7002 3 short and 1 long 7003 1 short, 1 long and 1 short 7004 1 short, 1 long and 2 short 7 7005 2 short, 1 long and 1 short 7006 1 short and 2 long 7007 2 long and 1 short 7008 1 long and 4 short 7009 4 short and 1 long 70001 3 short, 1 long and 1 short 70002 2 short, 1 long and 2 short 70003 1 short, 1 long and 3 short 70004 6 short It will be observed that certain of the call numbers appearing in the above table require the calling of either two or three digits instead of one in order to control the set of the code selector M. To provide for this, the 11th and 21st contacts in the bank associated with the wiper 115 are not mul tipled with the remaining contacts so that when the code selector is operated in accordance with the digit 0, for example, when the slow acting relay 103 deenergizes at the end of the series of impulses, the rin ing switch I? will not begin its operation It the next'digit called is some digit other than 0 the end or the series of impulses the ringing switch N will be started as pre viously described for all contacts between the 11th 21st are multipled with the ones preceding the 11th. If the next digit called is again 0, however, the wiper 115 will be advanced to the 21st contact, making it necessary to call still another digit before the ringing operation will begin. The switch is prevented from stopping on the 11th and 21st contacts during the release by means of a conductor 13-5 which serves when relay 102 is deenergized to join these two contacts to'the remaining ones.

Having described my invention, what I consider to be new and desire to'have pro tected by Letters Patent will be pointed out in the appended claims:

What I claim as my invention is:

1. In a telephone system, a pair of con nected terminals common to the exchange, means, whereby a calling subscriber can obtain a connection with the first of said termi nals, other terminals multiplied to said first terminals, and means for making said terminals busy when said calling subscriber obtains connection with said first terminal, signaling means associated with said first terminals for signaling a called subscriber, and means whereby the called subscriber can obtain a connection with the second of said terminals while said other terminals are busy, whereby the said calling and called subscribers may be telephonically connected.

2. In a telephone system, a pair of connected terminals common to the exchange, telephone call and answer numbers assigned to said terminals respectively, means operated in accordance with the call number for connecting a calling subscriber with one of said terminals and for making said terminal busy when said calling subscriber obtains connection thereto, means for signaling the called subscriber, and means operated in accordance with the answering number for connecting the called subscriber with the other of said terminals while said first terminal is bus, whereby said subscribers may be telephonically connected.

3. In a telephone system, a pair 01 connected terminals common to the exchange, telephone call and answer numbers assigned to said terminals, respectively, means operated in accordance with the call number for connecting a calling subscriber with one of said terminals and for making said terminal busy when said calling subscriber obtains connection thereto, means for signaling the called subscriber in accordance with a predetermined code, and means operated in accordance with the answering number for connecting the called subscriber with the and other or said terminals while said first terminal is busy, whereby said subscribers may be telephonically connected.

a l. In a telephone system, a pair of connected terminals common to the exchange, automatic switching mechanism controlled by ii-calling subscriber for establishiiu; connection with the first oiisaid terminals other terminals multipled to said first terminals, and means for making said terminals busy when said calling subscriber obtains connection with said first terminal, signaling means associated with said first terminal tor signaling a called subscriber, and automatic switching mechanisnr controlled by the called subscriber tor establisl'iinp a connection with the second oil said terminals while said other terminals are busy, whereby the said calling and called subscribers may be telephonically connected.

In a telephonesystem, a pair of connected terminals common to the exchange, telephone call andanswer numbers assigned to said terminals, respectively, automatic switching mechanisn'i controllal'ile by a calling subscriber in accordance with the call number for extending a connection to'one of said terminals and for malting said terminal busy when said calling subscriber obtains connection thereto, means for then signaling the called subscriber, and automatic switching mechanism controlled by the latter in accordance with the answering number tor extending a connection to the other of said terminals while said first terminal is busy, whereby the calling and called subscribers may be telephonically connected.

(5. In a telephone system, a pair of connected terminals common to the exchange, telephone call and answer numbers assigned to said terminals, respectively, automatic switching mechanism controllable by a cal in;- subscriber in accordance with the call number for extending a connection to one of said terminals and "tor making said terminal busy when said'calling subscriber obtains connection thereto, a common signaling system and means tor operatingthe same in accordance with a predetermined code to signal a called subscriber, and automatic switching mechanism controlled by the latter in. accm'dance withthe answering number tor extending a coi'incction to the other o'i' said terminals while said first terminal is busy, whereby the calling and 'called subscribers may be telephonically connected.

7. In a private branch exchange system, a plurality of special signals located at. ditferent points in the system. a common circuit for actuating allsa-id signals simultaneously in order to notify a party at some unknown point thathe is wanted, means for bringing said circuit under the control of the calling subscriber, means controlled by the subscriber for determiniag rhe code by which said signals are to be operated, and automatic means for thereafter causing said. signal to be actuated in accordance with the predetermined code.

8. In a private branch exchange system, a plurality of special signals located at difterent points in the system, a common circuit tor actuating all said signals simultaneously in order to notify a party at. some unknown point that he is wanted, means under control or" the calling subscriber for controlling said circuit in a predetermined distinctive manner to signal the particular party wanted and automatic means for thereafter actuating said signals in said predetermined n'ianner.

9.In a private branclnexchange system, a plurality of special signals located atdit l erent points in the system, a common circuit tor actuating all. said signals simultaneously in order to notify a party at some unknown point that lie wanted; means controlled by the calling party tor preparing a talking circuit, and for thereafter closing said signaling circuit, and means controlled by the called party in response to the signal for con'ipleting said talking circuit and for opening said signaling circuit.

10. In a private branch exchange systemi a plurality of special signals located at ditterent points in the system, a common cir cuit tor actuating all said signals simultaneously in order to notify a party at some unknown point that he is wanted, a code selector switch and. a controlling switcl'i, means under control of the calling party for setting said code selector to signal the particular party wanted, and circuit connections whereby said controlling switch is operated auto matically thereafter to close said signalingcircuit in accordance with the selected code.

11. In a private branch. exchange f *steni. a common signaling circuit comprising); a plurality oi signaling devices, equipment comprising a code selector and a controllinir switch, automaticswitching mechanism controlled by a calling, subscriber in. accord ancewith the digits of a special call number for extendingv a connection to said equipment. and means i-m- "then settingsaid code selector in accordance with another din'it. the said controlling switch being automati cally responsive to the setting ot said code selector for closing said signaling circuitin accordance with the selected code.

1.2. The method of connecting callina' and called sul'iscribers in conversation in an ai'itoniatic te ephone syst .n. which consists oi the operation of an automatic switch by a calling; subscriber to connect with one of a pair of terminals accessible to the subscriber and starting the operationofa code signalling equipment associated therewith to signal the called "suscriber, and in thejfope ation as auto n;

switches by the called party in response to the signal to connect with the other of said pair of terminals and thereby automatically stop the operation of said code signaling: equipment and complete the connection be-- tween the calling and called subscribers.

13. In a telephone system, a pair of connected terminals common to the exchange, means whereby a calling subscriber can obtain a connection with the first of said terminals, signalling means associated with the first of said terminals for signalling a called subscriber, means whereby the called subscriber can obtain a connection with the second of said terminals whereby the calling and called subscribers may be telephonically connected, and automatic means responsive to the establishment of said telephonic connection for disconnecting said signalling means.

14. In a telephone system, a pair of connected terminals common to the exchange, telephone call and answer numbers assigned to said terminals, respectively, means operated in accordance with the call number for connecting a calling subscriber with one of said terminals, means for signalling the called subscriber in accordance with a predetermined code, means operated in accordance with the answering number for connect ing the called subscriber with the other of said terminals whereby said subscri jiers may be telephonically connected, and automatic means responsive to the establishment oi" 5? said telephonic connection for disconnecting said signalling means.

15. In a telephone system, a pair of connected terminals common to the exchange,

automatic switching mechanism controlled by a calling subscriber for establishing a connection with the first of said terminals. signalling means associated with said first terminals for signalling the called subscriber, automatic switching mechanism controlled by the called subscriber for establishing a connection with the second of said terminals, whereby the said. calling and called subscribers may be telephonically connected. and automatic means responsive to the establishment of said telephonic connection for disconnecting said signalling means.

16. In a telephone system, telephone lines, a pair of connected terminals common to the exchange, automatic switching mechanism controlled from a calling one of said lines for establishing connection with the first of said. terminals, code signalling means associated with said first terminals. an auto-- matic switch associated with. said first ter-- minals, means controlled from said calling line for operating said automatic switch to select a particular code in order to signal r subscriberat an unknown point in the exchange, and automatic switchingmechanism controlled by the'said called subscriber for establishing a connection with the second of said terminals, whereby said calling and called subscribers may be telephonically connected.

17. In a telephone system, telephone lines, a pair of connected terminals common to the exchange, automatic switching mechanism controlled from a calling one of said lines for establishing connection with the first of said terminals, code signalling means associated with said first terminals, an automatic switch associated with said first terminals, means. controlled from said calling line for operating said automatic switch to select a particular code, signals common to the exchange, means for operating said common signals in accordance with the selected code to signal a subscriber at an unknown point in the exchange, and means controlled by the said called subscriber for establishing a connection with the second of said terminals whereby said calling and called subscribers may be telephonically connected.

18. In a telephone system, a pair of connected terminals common tothe exchange, automatic switching mechanism controlled by a calling subscriber for establishing connection with the first of said terminals, code signalling means associated with said first set of terminals, means controlled by said calling subscriber for selecting a particu lar code, a plurality of signals common to the exchange, automatic means for actuating said signals in accordance with the selected code to signal a called subscriber, and automatic switching mechanism controlled by the said called subscriber for connecting with the second terminals, whereby said calling and called subscribers are telephonically connected.

19. In a telephone system, a pair of connected terminals common to the exchange, automatic switching mechanism controlled by a calling subscriber for establishing connection with the first of said terminals, code signalling current associated with said first terminals, a code selecting switch accessible from said first set of terminals, mean controlled b'y said calling subscriber for operating said code selecting switch to select a particular code, signalling devices common to the exchange, automatic means for actuat- 111g said. devices'in accordance with the selected code, and means controlled by a called subscriber for obtaining connection with the other set of terminals thereby establishing a telephonic connection with said calling subscriber 20. In a telephone system, a pair of con-- nected terminals common to the exchange, automatic switching mechanism controlled by a calling subscriber for establishing connection with the first of said terminals, code signalling current associated with said first terminals, a code selecting switch accessible iling devices.

n a telephone system, a pair of connected terminals common to the exchange,

automatic switching mechanism controlled by a chilling subscriber torestabhshing connection with the first of said terminals, code signalling current associated with said first terminals, a code selecting switch accessible from said first set of tern'1inals, means con trolled by said calling subscriber for operating said code selecting switch to select a particular code, signalling devices common to the exchange, automatic means for actuating said devices in accordance with the selected code, means controlled by a called subscriber for obtaining connection with the other set of terminals thereby establishing trolled b said callin subscriber tor onerating said code selecting switch to select a particular code, signalling devices common to the exchange, automatic means for actuatin; said devices in accordance with the selected code, means controlled by it called subscriber for obtaining connection with the other set oi terminals thereby establishing a telephonic connection with said calling subscriber, and automatic means responsive to the establishment or said telephonic connection for releasing said code selector.

23, In a telephone system, two sets of con nected terminals common to the exchange, automatic switching mechanism controlled by a calling subscriber for extending a connection to one of said sets oi terminals, a source of code signalling current, a code selector accessible from said first set of terminals, means controlled by the said calling subscriber for operating said code selector to select a particularcode, signalling devices common to the exchange, automatic means for operating said signalling devices in response to the selected code to signal a called subscriber, automatic switching mechanism controlled by the called subscriber for extending a connection to said second set of terminals whereby the calling and called subscribers are telephonically connected, and automatic means responsive to the establishment of the last connection for releasing said code selecting switch.

24. In. a code ringing machine, a pair of step bystep switches, permanent conductors connecting the bank contacts of onevswitch with the bank contacts of the other, ringing mechanism, subscriber controlled means for operating one of said switches to select a desired code, and automatic means for operating the other of said switches to operate said ringing mechanism in accordance with the selected code.

25. In a telephone system, a signalling circuit, a plurality of signals connected to said circuit, a code selecting switch operable by a calling subscriber to select a code,

mechanism cooperating with said switch for operating said signals over said circuit according to the code selected, and means for preventing the restoration of said switch and cooperating mechanism in case the calling subscriber hangs up his receiver before the code is finished,

26. In a telephone system, a signalling circuit, a plurality of signals connected to said circuit, a code selecting switch operable by a calling subscriber to select a code, mechanism cooperating with said switch for operating said signals over said circuit according to the code selected, means for restoring said switch and cooperating mechanism controlled by the calling subscriber, and means for preventing the calling subscriber from producing a false signal by restoring said switch and cooperating mech- 'anism before the code is completed.

27. In a telephone. system, a signalling circuit, a plurality of signals connected to said circuit, a code selecting switch operable by a calling subscriber to selecta code, mechanism cooperating with said switch for operating. said signals over said circuit according to the code selected, means controlled by a called subscriber for stopping the signalling operation. and means for preventing the stopping of. the signalling operation before the code is finished.

28. In a telephone system, a signalling circuit, a plurality of signals connected to said circuit, a code selecting switch operable by a calling subscriber to select a code, a sending switch cooperating with said selecting switch to operate said signals over said circuit in accordance with'the code selected, an operating circuit for said sending switch initially closed by the calling subscriber, and locking means for preventing the opening of said circuit until the code is completed.

29. In. a telephone system, a signalling circuit, a plurality of signals connected to said circuit, a code selecting switch operable by a calling subscriber to select a code, a

sending switch cooperating with said selecting switch to operate said signals over said circuit in accordance with the code selected,

subscriber controlled means for restoring said selecting switch, and means for preventing the restoration of said selecting switch while said sending switch is in an oil normal position.

50. In a telephone system, a signalliugcircuit, a plurality of signals connected to said circuit, a code selecting switch operable by acalling subscriber to select a code, asending switch cooperating with said selecting switch to operate said signals over said circuit in accordance with the code selected, means controlled by the called subscriber for stopping the signalling operation, and means for preventing the stopping of the signalling operation while said sendingswitch is in an off normal position.

31. In a telephone system, asignalling circuit, a plurality of signals connected to said circuit, a code selecting switch operable by a calling subscriber to select a code, a send- 111g switch cooperating with said selecting I switch to operate said signals over said cir- 7 normal position.

33. Inc code ringing machine, a register switch adapted to be set in accordance with a code digit, a" rotary switch for transmitting the code, means for operating; said Totary switch continuously to repeat the code at intervals, and means for preventing the restoration oi said register switch. ex-

cept when the said rotary switch is in a particular position.

34;. In a telephone system, a pair of terminal sets common to the exchange, unlike call and answer numbers assigned to said sets, respectively, automatic switching mechnism controlled by a calling subscriber in accordance with the call number for connect ing with the first of said sets, automatic switching mechanism controlled by the called subscriber in accordance with the answer number for connecting with the second of said sets, and conductors connecting said terminal sets to permit conversation between said subscribers.

35. In atelephone system, a plurality of automatic switches, a set of multiply connected calling terminals in each 0i said switches having a call number, a set of multiply connected answering terminals in each of said switches having an answer number,

means under the control of a calling subscriber -for operating one of said switches in accordance with the call number to connect with a set of calling terminals, means under the control'ot the called subscriber for operating another of said switches in accordance with the answer number to connect with a set of answering terminal-sand multiple connections between the calling and answering terminal sets to permit conversation between said subscribers.

36. In a telephone system, a pair of terminal sets common to the exchange, an automatic connector switch operable by a calling subscriber for connecting with the first of said terminal sets, a second automatic connector switch operable by the called subscriber for connecting with the second of said terminal. sets, a back bridge relay in each connector bridged across the wipers thereof in series with the exchange battery, and transposed conductors connecting said terminal sets whereby said relays are energized in series.

37. The combination, with a register switch adapted to be set in accordance with a digit in a number, of a code sending switch, automatic operating means for said second switch, and conductors connecting bank contacts of said register switch with bank contact-s of said sending switch, whereby the code sent out is in accordance with the setting of said register switch.

Signed by me at Chicago, Cook County, Illinois, this second day of July, 1917.

MARTIN L. NELSON.

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