US2139799A - Telegraph switchboard switching system - Google Patents

Description

Dec. 13, 1938. A. R. BONORDEN 2,139,799

TELEGRAPH SWITCHBO'ARD SWITCHI NG SYSTEM Filed Aug. 26, 1936 9 Sheets-Sheet 1 4 1 A T TORNEV Dec. 13, 1938. A. R. BONORDEN TELEGRAPH SWITCHBOARD SWITCHING SYSTEM 9 Sheets-Sheet 2 Filed Aug. 26, ,-l95s ZZZ-2::-

INVENTOR A. R. BONORDEN ATTORNEY c- 9 A. R. BONORDEN 2,139,799

TELEGRAPH SWITCHBOARD SWITCHING SYSTEM F led Aug. 26, 1936 9 Sheets-Sheet 3 FIG. 3

//v l/E/VTOR B R BONORDEN DEC. 13, A R BoN QRDE| 2,139,799

TELEGRAPH SWITCHBOARD SWITCHING SYSTEM Filed Aug. 26, 1956. 9 Sheets-Sheet ,4

FIG. 4-A

FIG. 4 #7615 FIG 6 INVENTOR By A. R. BONORDEN A T TORNEV c. 13, 19 38. A. R. BC DNORDEN 2,139,799

TELEGRAPH SWITCHBOARD SWITCHING SYSTEM Filed Aug. 26, 1936 Sheets-Sheet 5 MARG/NA L llllllll ll um MA I? GINAL /a 640 INVENTOR By A. R. BONORDEN 6 A 7' TOR/VEV Dee-13, 1938. R BQNORDEN 2,139,799

TELEGRAPH SWITGHBOARD SWITCHING SYSTE IM Filed Aug 26, 1956 9 Sheets-Sheet 6 //v vE/vmR R. BONORDE N A Tram/5 Dec. 13, 1938. A, R BONORDEN 2,139,799

TELEGRAPH SWITCHBOARb SWITCHING SYSTEM Filed Aug. 26, 1936 9 Sheets-Sheet 7 A/ 5 N TOR By A. R. BO/VQRDE/V A TTOR/VEV i 138. A. R. BONORDEN TELEGRAPH SWITCHBOARD SWITCHING SYSTEM Filed Aug. 26, l936 9 Sheets-Shget 8 FIG. 8

W630 W31 82 v T R m M W A R; BQ/VORQEW By I A T TOR/V5) A. R. BONORDEN Dec. 13, 1938.

TELEGRAPH SWITCHBOARD SWITCHING SYSTEM Filed Aug. 26, 1936 9 Sheets-Sheet 9 ATTORNEY //v l EN TOR A. R. BONORDEN FIG. .9

POST 2 I Patented Dec. 13, 1938 UNHEE TELEGRAPH SVVITCHBOARD- SWITCHING SYSTEM Allen Rudolf Bonorden,

Telephone and to American Fanwood, N. 5., assigncr Telegraph Company, a corporation of New York Application August 26, 1936,8erial No. 98,055

7 Claims.

his invention relates to communication systems and more particularly to supervising and maintaining private, or order, wire service over intercity communication trunk circuits between test board attendants located in different cities.

An object of the invention is to permit an attendant at a test board or switchboard in one locality to be connected with any one of a plurality of attendants at a test board or switchboard in a different locality.

It is essential in test best operation in communication systems for attendants at two different localities, having charge of a particular service at their respective switchboards, to obtain direct communication with each other and consequently it is desirable to have an arrangement which will facilitate certain direct communications or permit of an incoming call being rapidly transferred to an attendant responsible for a particular service. Heretofore in both toll and telephone practice the transfer of calls, received over certain trunks or line circuits, is possible to a very limited extent, that is the facilities at present permit the transfer to one or at the most two points in the oflice.

According to the present invention, the facilities provide for each position or section in a line of test board to become a potential transfer point and in the larger of said oflices these facilities extend to arrangements for transferring a call to any one of a plurality of positions or sections. In other words an attendant at a multiple type of switchboard may upon receiving an incoming call over an intercity communication trunk circuit, transfer the incoming call signal to any particular one of a plurality of trunk lamps, each of which is located at a different position or section in the switchboard. The multiple type of switchboard may comprise two or more sections, each section having one or more operators or attendants positions.

A feature of the present invention is that it provides a more flexible arrangement than heretofore known in that an incoming call signal may be transferred to a signal lamp at any one of even than twenty positions.

Another feature is that an incoming call sigmay be transferred to a lamp at any one of plurality of switchboard positions and then again transferred to another lamp at one of the other positions.

Still another feature is that the arrangement may provide by proper cross-connections, for any trunk circuit'to have either a primary or a secondary answering appearance at any on the multiple type of switchboard.

Another feature is the provision of having a sequence circuit associated with the trunk circuits or the positional key-sets. 5

Another feature is the provision of recalling the attendant at a primary position after the signal has been transferred to another position and the attendant at the latter position has failed to answer.

Another feature is the provision of a transfer key so that for night operation all signals of diiferent trunk circuits normally appearing at difierent primary positions may be caused to appear at some one position used as a night or light load position.

Description A more complete understanding of-the invention may be obtained from the accompanying drawings in Which Figures 1, 2 and 3, represent an arrangement of the invention, when interconnected in accordance with the block diagram Fig. 1A, wherein figure 1 shows two-way communication lines and associated line equipment, Fig. 2 a sequence circuit and associated control circuit for transferring calls and Fig. 3 answering jacks and lamps, associated busy lamps and trunk transfer keys, cord circuits and position transfer keys, cord circuits and position transfer keys with associated equipment.

Figs. 4, 5 and 6 represent another arrangement of the invention, when interconnected in accordance with the block diagram Fig. 4A, wherein Fig. 4 shows two-way communication trunks and associated line equipment, Fig. 5 a control circuit for transferring calls and Fig. 6, answering jacks and lamps, associated busy lamps and trunk transfer keys, cord circuits, position ester keys with associated equipment and circuit relays.

7, 8 and 9 represent still another ar rangement of the invention, when interconnected in accordance with the block diagram 1A, wherein Fig. 7 shows two way communication trunks and associated line equipment including a cros's bar switch and Fig. 8 shows answering jacks and lamps, busy lamps, position transfer keys, cord circuits and a control circuit consisting of a rotary stepping switch.

Fig. 9 is an alternative arrangement of Fig. 8, which uses a relay type control circuit.

Figures 1, 2 and 3 Referring to Figs. 1, 2 and 3, Hill isan interposition office trunk, which terminates in jacks 306, 353! the circuit of trunk I is opened momentarily and 302 of positions 1, 2 and 3, respectively. which causes the momentary release of line relay Associated with each of these jacks are answer- Hi3. If the line is kept open sufliciently long, re-

be provided at additional positions, not shown. releasing relay Hi5, which after an interval re- As shown in the drawings positions 1 and 3 are leases and closes a circuit from ground on its cross-connected by conductors 260, so that the winding through its back contacts, momentarily associated answering lamps 303 and 3135 are operated left contacts of relay I06 and winding of gether similarly placed contacts of all the switch into jack see before the attendant at position 3 cordingly a secondary answering position. It is then relay H35 holds operated in a circuit from to be understood, however, that, by the proper battery through the winding of relay I06, opcross-connection, any position in the switchboard erated contacts of relay I05, Winding of relay line up may be arranged as either a primary or MS, right operated front contacts of relay I06,

In order to transfer incoming calls from one tion, relay Hi6 releases and relay I01 does not position to another, trunk 39 is provided with a operate. It is seen therefore that the line relay rotary type stepping switch having a stepping il will respond only to an open interval of magnet 20!, which causes the brush arms 202 definite minimum duration, and not too short irand 2&5, respectively; Each terminal of bank 294 other closely, thereby preventing false line sigis connected to a conductor leading to an answernals.

ing lamp at the respective positions whereby each When relay I07 operated it connected battery, lamp may be selectively lighted as required. Each with its right outermost and middle contacts, to contact of bank 205 is connected to a conductor conductors I09 which are cross-connected by conto which ground is selectively connected by the ductors 280 to conductors 3M and 3|5. Answeroperation of one of the positional transfer keys, ing lamps 3G3 and 305 of positions 1 and 3, reas key 309, 3H or 3 of position 1. In effecting spectively, are simultaneou y lighted. Relay transferred is identified by the key 399, 3H3, 3! I, most contacts to conductor 3|6 thereby lighting etc. and. the trunk is identified by the associated the busy lamps at all positions. Attendants at transfer key, such as key SL2. In order to use positions 1 and 3 respond to the lighted lamps a transfer trunk common to all positions, such as 393 and 355 with cord circuits 3!! and 3H). Astrunk SIS, the conductors of which connect tosuming that the attendant at position 1 plugs which are arranged in a manner similar to the conductor 328 and through the uppermost oprelays of an automatic listening, straightforward rated contacts of jack 3&9 to ground. Relay trunk sytsem, which is well known in the tele- Hi l in operating disconnects ground with its in-. phone art. The aforesaid sequence circuit funcher right back contacts from conductor Ill', tions so that the transfer trunk 3| 3 is available thereby releasing relay I01 and extinguishing to only one trunk a a t thereby ak n i the answering lamps 303 and 305. The attendunnecessary to bring a separate conductor from a t at position 3, observing that lamp 305 is exe h k y to the on s of ank 203, and the tinguished knows that the call is being handled contacts of similar banks associated with trunks t nother position and accordingly makes no lo! and 0 Another feature of the sequence further effort to answer the call. Relay I01 in circuit is the arran m n wher y calls aw itreleasing also disconnects battery with its right n th d s r p be o e given, part cula refwith its left innermost contacts, thereby main- "c5 e enee Was m d to the trunk and its taining the lighted condition of the busy lamps sociated apparatus. A similar description also t l positions. Relay I84 in operating also pp to the othe trun s, I0 and "J A mo e closes through with its contacts H3 the lower mp understanding of the Operation of the conductor of trunk I60 to lower conductor of inVeIltion y be a d f om he following trunk H4 and with contacts H2 disconnects the 79 detailed description. winding of relay Hi3. Contacts H3 are arranged Let it be assumed that an attendant at a disto make before contacts H2 break, thereby maintant point desires to communicate over trunk loll taining Without interruption the continuity of the with an attendant at the secondary answering line. position, position 2 of Figure 3. To initiate a call When the plug of cord circuit 3" is inserted into jack. 3%, the attendant of position 1 is in telegraphic communication over the tip and sleeve conductors of jack 300, trunks H4 and I00 with the distant attendant. Assuming that, as before stated, that the call is to be transferred to the secondary position 2, the attendant of position i'will upon being requested to effect the transfer, now operates momentarily the key 3l2 associated with jack 386, thereby closing a circuit for operating relay llll, which is traced from battery through the right contacts of relay H5, winding of relay 5 it, over conductor 32 I, through contacts of key M2 and contacts 322 of jack 300 to ground. Relay H8 in operating looks through its left contacts to ground on the right inner front contacts of relay ic i and with its right middle contacts closes a circuit from ground over conductor HE to battery 2H5 through the winding of the sequence circuit relay 2111, which operates. If at this time no other trunkas I0! or lSZ-is being transferred by an attendant at another position, relays 209 and 2 are not operated and consequently a circuit is closed for operating relay 238 associated in the sequence circuit with relay 2%. This circuit may be traced from ground 238 on the back contacts of relay 213 through the winding of relay 2M, (which also operates for a purpose hereinafter explained), back contacts of relays 2H and 2 39, right front contacts of relay 2%! and winding of relay 298 to battery. If, however, another trunk at this time is being transferred either relay 259 or 2H is operated and the circuit before traced for operating relay 208 is open at the back contacts of relay 269 or 2| I. If relay 209 is operated, its winding is connected to battery 2l5 through the left break contacts of relay 208; if relay 2!! is operated then its winding is connected to battery 2 it through left break contacts of both relays 2M! and 208.

A general description of the operation of the sequencecircuit, which as before stated is used in the telephone art for straightforward trunking will now be given. Relay 2! I may be said to' be in the first, relay 2st in an intermediate and relay Zii'i in the last or highest numbered position in the sequence circuit chain. If relays 2G9 and Eli; are operated, and lines are awaiting service in the last and first positions, relay 291 is operated, but relay 2H is not operated, since its operating path is disconnected by the left inner break contacts of relay 2H3. When relay 299 releases conductor 2% is transferred from the winding of relay Ziil to conductor 239 by the continuity contacts of relay 209, thereby holding relay 2M operated through the right make contacts of relay 2l3'i and the winding of relay 298, which now operates. Relay 2 does not operate since its circuit is opened by the left inner break contacts of relay 288. When relay 2B! releases, releasing relay 2%, the circuit through relay 2H! is opened and this relay releases, releasing in turn slow releasing relay 2l3, which after an interval longer than the release time of relay 208 connects ground 238. During this open interval with relay 2558 released, relay 2 and also relay 239, if this relay is again awaiting operation, now operate. Relay 2, however, disconnects conductor so that relay 252, and not relay 2H! or operates. It thus appears that lines awaiting connection are served by the sequence circuit sequentially in accordance with their numbered position in the sequence, and not in accordance with the order of their call for service.

With relays 2 i0, 201 and 208 operated as before described, a circuit is closed for operating relay 334, which circuit may be traced from battery through the winding of marginal relay 216, over conductor 2 ll, through left outer make contacts of relay 2%, left contacts of relay 2M, over conductor 233, right innermost contacts of relay HE), over conductor 323, through contacts 324 of jack 309, over conductor 325, through left and right windings of relay 334 to ground. Relay 334 operates, but marginal relay 216, however, does not operate at this time. Relay 334 in operating closes an obvious circuit through lamp 326, which is lighted indicating to the attendant that the circuit is now ready for the operation of the position transfer key. To transfer to position 2, key aid is accordingly operated. If key 3H! should be operated prematurely, that is, before lamp 326 is lighted, then a circuit is closed from ground, through right contact of key 3H3, back contacts of relay 334 (which has not operated) to battery through lamp 321, which is lighted indicating that the circuits are not ready to effect the desired transfer, either because of failure to operate the transfer key M2, or the non-availability of the sequence circuit at this moment.

In order to assist in differentiating clearly between the significance of the two lamps, lamp 325 may be provided with a white, and lamp 327 with a red cap. On operating key Sill, assuming that relay 334 is operated, a circuit is closed from ground on its left contacts through the left contacts of key till, over' conductor 328 to the second terminals of the hunting contact banks 2 35, 2GB and 2 Hi. .In the drawings all brush arms are shown resting on the first contact terminals. It is to be understood, however, that the brush arms may rest normally on any contact terminal, since after a selection they remain on the selected terminal. The operation of key 3H] with its right contacts connects a ground to the right inner front contacts of relay 334, thereby short-circuiting the right or high resistance winding of relay 334, which is connected to the said front contacts. Relay 33A continues to hold through its winding. The resistance in the circuit of marginal relay 2H3, is reduced and it now operates and closes a circuit from ground through the left back contacts of relay 2H1 and winding of slow releasing relay 229 to battery. Relay 22E opcrates and closes a circuit from ground through its contacts 22land 222, back contacts of relay 223, right inner break contacts of relay 2!.9, over conductor 22%, right innermost contacts of relay 298, over conductor 225, right outermost contacts of relay Hi3, over conductor 22% and through the self interrupting contacts and winding of rotary stepping magnet 2M to battery. The brush arms 2% and 203 are now stepped around the contact banks 206 and 2215 in the direction of the arrows respectively until the second terminal from the top isreached, which terminal is connected to the grounded conductor 328. When this terminal is reached a circuit is closed for operating relay 223 which is traced from battery through the winding of relay 223, over conductor 22'l through the right outermost contacts of relay 2%, brush arm 2%, second terminal of bank 295, over conductor 328, through left operated contacts of key 3? and relay 334 to ground. Relay 223 in operating closes a circuit from ground through contacts 225 and 222 of relay 229, front contacts of relay 223, and winding of relay 2l9 to battery. Relay 223 also opens the previously traced operating path of selector magnet 2i3i which stops the rotation of the brush arms leaving them on the second terminals, or contacts. Relay 2I9 operates and closes a circuit for holding itself and relay 220, which is traced from battery through the winding of relay 220, left front contacts of relay 2I9, front contacts of relay 223, and contacts 22I and 222 of relay 220 to ground. Relay 220 is slow in releasing and holds over the momentary open period while the left contacts of relay ZI9 are operating. Relay 2I9 in operating also opens the operating circuit for magnet 20I, so that the subsequent release of relay 223 will not again start the selector. Relay 2I9 in operating also closes a circuit from ground through contacts 2 2I of relay 220, right outer contacts of' relay 2I9, over conductor 228, right middle contacts of relay 208, over conductor 230 and through winding of relay H5 to battery. 7

If, as a result of a previous selection, brush arms 202 and 203 had been found resting on the second terminals of I their associated banks, then relay 223 would have operated immediately and there would have been no switch movement whatever. Relay H5 operates and locks through its left inner contacts to ground on the right outer front contacts of sleeve relay I04, and with its right contacts opens the circuit of the winding of relay II 0, which releases. Relay II 0 in releasing, opens the circuit of sequence relay 201 which releases, in return releasing relay 208. The circuits of relays 2I6, 223 and 334, before traced, are now opened and these relays release. The release of relay 223 releases relays 2I9 and 223. When relay 334 releases, the selector lamp 326 is extinguished and the disconnect lamp 321 is lighted, which indicates to the attendant of position 1 that the transfer has been effected and that key 3I0 may now be released. The plug of the teletyepwriter cord circuit 3I1should now be withdrawn from jack 300, which opens its uppermost contacts releasing sleeve relay I04, which effects the operation of relay I I I in a circuit from battery through the winding of relay II I, left outer operated contacts of relay II 5 to ground on the right outer back contacts of relay I04. The locking circuit for relay H5, through its left inner contacts is opened by the release of relay I04, but relay H5 is slightly slow in releasing so that relay II! has time to operate the lock through its right contacts to the ground on conductor H8, before relay II 5 releases. Relay H1 in operating connects battery through its left inner contacts to conductor 3I6 thereby maintaining the lighting of the busy lamps at all positions, and with its left outer contacts connects battery to conductor 228, which is extendedover brush arm 202, second terminal of bank 204, con- .ductor 329 and through lamp 304 to ground.

Lamp 304 is lighted and in response thereto the attendant at position 2 inserts the plug of cord circuit 3H3 into jack 30I thereby connecting with trunk H4 through the tip and sleeve conductors. When the uppermost contacts of jack 30I connect ground to conductor 320, sleeve relay I04 is operated again; removing ground from conductor H3 releasing relay II I, which disconnects battery from conductor 229, thereby extinguishing lamp 394 at position 2. The operation of relay ice connects battery with its left innermost contacts to conductor 3I6, thereby maintaining the lighting of the busy lamps when relay I ll disconnects battery with its left inner contacts.

The hereinbefore given discussion described how an incoming call was answered at primary position 1 and was then transferred to secondaryposition 2. In accordance with a feature of the invention, the attendant at position 2 may now retransfer the call, if required, to any other position in the switchboard line up, in the same manner as was described for the transfer of the original call. If for instance a transfer to position 3 is required, transfer key 330 is operated and then position key 33L After the operation of relay 332, ground is connected to conductor 333, through the left operated contacts of key 33f, grounding thereby the third terminal of bank 205. The invention now functions as previously described in connection with the transfer of a call from position 1 to position, 2. Brush arms 202 and 203 stop on the third terminal of banks 204, and 205, respectively. When 'the plug of cord circuit (H8 is withdrawn from jack 30f, relay I04 releases and relay II'I operates, lighting lamp 305 at position 3 over conductors 229 and 3I4 through brush arm 202 and third terminal of bank 204.

The operation of the invention has been described for an incoming call. It may also be used for outgoing calls. The attendant at position 2, for instance, may originate a call by plugging into jack 38!, thereby operating sleeve relay I04 over Zonductor 326. Relay I04 in operating connects attery ductor 3ft, lighting the busy lamps at all positions. The attendant at the distant end of the line is signaled by the operation of the break key of the teletypewriter or by opening the telegraph key of cord circuit 3I8. If after communication has been thus established, it is desired to transfer the connection to another position, this may be done in the same manner as described in connection with an incoming call.

The invention has been described using as a basis trunk I00, which is associated with relays 2e? and 268, which are in the last position of the sequence circuit chain. The invention functions in a similar manner for trunks IOI and I02, which are in the second and first positions, respectively. Relay 209, however, does' not operate after its associated relay I I9 operates, unless relay 258 is normal at the time, so that battery 2I5 is available through the left inner contacts of relay 208 over conductor 230. Similarly relay2 I I, does not operate immediately, when its associated relay I20 operates, unless relays 208 and 25d are both not operated, thereby making battery 2E5 available through the left inner contacts of relays 208 and 2| 0, over conductors 230 and 23L Although only three trunks are shown it is to be understood that other trunks may be added. Additional pairs of sequence relays may be connected in the same manner as are relays 209 and 2H0, 2H and 2I2. The additional relays should be connected to the vertical extensions of conductors 232, 2H, 22?, 228 and 224 in which case battery 2I5 is always associated with the last relay in the sequence.

Figures 4, 5 and 6 Referring now to the arrangement of the invention shown by Figs. 4, 5 and 6, 400 is an interofiice trunk which terminates on jacks 600, 60I and 652 of positions 1, 2 and 3, respectively. Associated with these jacks are answering lamps 693, 554 and 505 and busy lamps 606, 601 and which calls may be answered by plugging into the with its left innermost contacts to conjack associated with the lighted answering lamp, or originated by plugging in and then operating the teletypewriter break key or holding the telegraph sending key open momentarily. Additional jacks, answering and busy lamps may be provided at additional positions, not shown. As shown in the drawings, position 3 is cross-connected by conductor 500, so that the associated answering lamp 605 is lighted on an incomin call, that is, position 3 is a primary answering position. Position 2 is normally not thus connected, its lamp 604 is lighted only on a transferred call, and is accordingly a secondary answering position. Position 1 may be either a primary or secondary position. When the night key 609 of trunk 400, and all other similar night keys are operated, then position 1 is cross-connected so that all incoming calls also effect the lighting of the line lamps of position 1, which is then a primary position. When key 609 and the other night keys are not operated, then the cross-connections are not effective, the answering lamps light only on transferred calls, and position 1 is then a secondary position. By the proper cross-connection any position in the switchboard line up may be arranged as either a primary or answering position.

In order to transfer calls from one position to another, trunk 400 is provided with a rotary type stepping switch, which is similar to that shown in Fig. 2. Each terminal of bank 505 is connected to a conductor leading to an answering lamp at the respective positions, whereby each lamp may be selectively lighted as required. Each contact of bank 506 is connected to a conductor, to which ground is selectively connected by one of the positional transfer keys, such as key BID, 6H or B|2 of position 1. In effecting a transfer the position to which the call is to be transferred is identified by the key M0, 6 or 612, etc., and the trunk is identified by the associated transfer key, such as key 6H, which is an arrangement like that of Figs. 1, 2 and 3. In order to make use of a simple transfer trunk such as (H6, which is similar to the arrangement of Figs. 2 and 3; a sequence circuit is provided consisting of a pair of relays such as GM and 615, interconnected as shown for each position. With this arrangement, the transfer facilities of only one position are available at one time, thereby avoiding possible interference due to several attendants at different positions attempting to transfer calls simultaneously. This arrangement differs from that of Figs. 1, 2 and 3, since in the latter the sequence circuit was associated with the individual trunks and not with the positional transfer keys. Where there is a comparatively large number of trunks with only a few switchboard positions the arrangement of Figs. 4, and 6 may be more desirable than that of Figs. 1, 2 and 3, since fewer sequence relays may be required. There is a possibility, however, that in the arrangement of Figs. 1, 2 and 3 that the attendant at one position may attempt to transfer two trunks simultaneously. A description of the means whereby interference is avoided in this case is given hereinafter under Figs. 4, 5 and 6;

Figures 4, 5 and 6 A more complete understanding of the operation of the arrangement of Figs. 4, 5 and 6 may be obtained from the following discussion which follows the progress of a call. Let it be assumed that an attendant at a distant switchboard desires to communicate over line 400 with the attendant at the secondary position 2. When the normally closed circuit of line 400 is momentarily opened relay 403 releases and closes a circuit for operating relay 404, which is traced from battery on the right back contacts of relay 405 through the winding of slow releasing relay 434, closed break contacts of relay 4 03 to ground on the right inner break contacts of sleeve relay 400. Relay 494 in operating closes a circuit for operating relay 405, which is traced from the operating ground on the lower terminal of relay 40% through front contacts of relay 404 and winding of relay 405 to battery. After an interval, relay 405 which is slow-to-operate, operates and opens with its right back contacts, the operating circuit for relay 404. It also closes with its left contacts a circuit from battery through the winding of relay G3? to the back contacts of relay 404. When this relay releases after an interval, if the contacts of relay 403 still remain closed, the operating .ground on the winding of relay 404 operates relay 401, which looks over conductor 408 to ground on the right inn-er back contacts of relay 406. This arrangement of relays 403, 404, 405, and 401 is identical with that of relays I03, I05, I06 and lii'i of Fig. l and functions in a similar manner. Relay 40'! in operating connects battery with its right outer contacts to conductor 409, thence over cross-connection conductor 500 and conductor 623 to ground through lamp 005, which is lighted, and with its middle right contacts connects battery over conductor 624 to the contacts of night key 609. When this key is operated, which is the case when position 1 is operated as a night position, then battery is extended also over conductor 625, cross-connection conductor 50L and conductor 026 to ground through lamp 503 which lights.

Relay 107 also, with its right innermost contacts connects battery to conductor 628, thereby lighting busy lamps 606, 601 and 608. The attendant at position 3, responds with the tele typewriter cord circuit 622 and sleeve relay 4% operates over conductor 62? to ground through the uppermost local contacts of jack 602, and in operating removes ground from conductor 08, releasing relay 407i and extinguishing lamp 605. Relay 405 in operating connects battery with its left innermost contacts to conductor 628, which maintains the lighting of the busy lamps etc, 601

and 608, after battery has been removed by the release of relay 40?. Having been informed that the call should be transferred to position 2, the attendant at position 3 first operates the transfer key 629 associated with jack G02 and thereby closes a circuit for operating relay 430 which is traced from battery through the winding of relay 4H3, over conductor 630, through contacts of key 829 to ground through the operated contacts 63! of jack $02. The positional transfer key 650 is then operated and a circuit is closed from battery 638 through the winding of sequence circuit relay $32, lower back contacts of marginal relay 633 to ground through the right contacts of key 630. Relay 632 operates and if neither relay 5M or 034 is operated then a circuit is closed from 1 battery through the winding of sequence relay 635, lower front contacts of relay e32, lower back contacts of relays 634 and 614, over conductor 636, through winding of relay 501 to ground on the break contacts of relay 508. Relays 535 and 50'! operate. Relay 501 in operating closes an obvious circuit through the winding of slow releasing relay 508 and locks to ground on its own contacts. Relay 508 operates and disconnects the original operating ground. This arrangement of sequence relays operates in similar manner to that of Fig. 2 discussed before in detail. Relay 635 in operating connects ground with its upper outer contacts to conductor 63?; thence this ground is connected by the left operated contacts of key 630 to conductor 631, which terminates on the second terminal of hunting contact bank 506, thereby marking position 2 to receive the transferred call. Relay 635 disconnects, with its upper inner break contacts, battery 638 from conductor 639, thereby making this battery unavailable at this time for relays 634 and 610. Relay 635 also closes a circuit which is traced from ground through the upper winding of marginal relay 633, upper operated contacts of relay 632, lower inner contacts of relay 535, over conductor 640, and through the serially connected left and right windings of relay 509 to battery. Relay 509 operates in this circuit, but marginal relay 633 does not operate at this time. Relay 500 closes a circuit from ground through the left back contacts of relay 510 and winding of relay 511 to battery. Relay 511 operates and closes a circuit which is traced from battery through the left back contacts and right winding of marginal relay 512, operated left contacts of relay I, over conductor 641, through lower outer operated contacts of relay 635, over conductor 649 operated contacts 643 of jack 502, over conductor 644, through right outer break contacts of relay 411, over conductor 513, through winding of marginal relay 514, over conductor 515 to ground on the right outer operated make contacts of relay 410. Relay 510 operates but relay 512 does not operate at this time. Relay 514 in operating closes a circuit from battery through winding and break contacts of stepping magnet 502, right outer contacts of relay 514, over conductor 516, right inner break contacts of relay 510, back contacts of relay 517, operated contacts 518 and 519 of relay 5| 1, to ground on the break contacts of relay 512. The brush arms 503 and 504 are now rotated in the direction of the arrows until contact 2 is reached. A circuit is then closed from battery through the winding of relay 51?, over conductor 520, through left operated contacts of relay 514, over conductor 521, brush arm 504, second contact of bank 506, over conductor 631, through left operated contacts of key 650 to ground on operated upper, outer contacts of relay 635. Relay 51'1 operates and opens the operating circuit, hereinbefore traced, of magnet 502, thereby causing brush arms 503 and 504 to stop on the second terminals of banks 505 and 506. Relay 511 in operating closes a circuit for operating relay 510 which may be traced from battery through the Winding of relay 510, front contacts of relay.51'1, operated contacts 518 and 519 of relay 511 to ground on the break contacts of relay 512. Relay 510 looks with its left inner front contacts to ground on the contacts of relay 509, before relay 511, which is slow in releasing, releases due to the opening of its circuit by the left back contacts of relay 510. Relay 510 also closes a circuit from ground on the contacts of relay 512, through contacts 518 and 519 of relay 51 1, also before this relay releases, right outer contacts of relay 510, over conductor 522, through right inner operated contacts of relay 514, over conductor 523 and left winding of relay 411 to battery. Relay 411 operates and looks through its right winding and right inner contacts to ground on the left outer operated contacts of relay 410, and with left inner contacts connects battery to conductor 028 to maintain the busy lamps lighted, when sleeve relay 400 subsequently releases as hereinafter described. Relay 4l1 also opens with its right outer break contacts the operating circuit for relay 514, which releases.

When relay 511 releases as hereinbefore described it connects battery through its right outer break contacts and the left operated outer make contacts of relay 5l0 to the common terminal of the windings of relay 509, which is equivalent to short circuiting the right winding of relay 500. Relay 509, however, still holds through its left winding and, due to the decreased resistance, marginal relay 633 now operates and closes an obvious circuit tobattery through the transfer lamp 613, which lights. Relay 633 looks through its lower winding and front contacts to ground on the right contacts of key 650 and also with its lower contacts opens the circuit of sequence relay 032, which releases and in turn releases relay 635, thus immediately freeing the sequence circuit for the use of attendants at other positions even though the attendant at position 3 continues dilatorily to hold key 050 operated. After observing the lighted lamp 613, the attendant releases key 650, which releases relay 633, extinguishing lamp 513. On withdrawing the plug of cord circuit 622 from jack 602 sleeve relay 406 releases, releasing relay 010. Relay 406 in releasing connects ground through its right outer back contacts and through the right inner contacts and winding of relay 011 to battery. This prevents relay 311 from releasing when the ground on the left outer contacts of relay 410 is disconnected. Relay 406 in releasing also reconnects to the conductors of trunk 400, the winding of line relay 403, which reoperates; The release of relay 410 closes a circuit from battery through the right break contacts of relay 410, left outer operated contacts of relay 411, over conductor 52 1, brush arm 503, second terminal of bank 505, over conductor 042 and to ground through lamp 604, which lights. In response to the lighted lamp, the attendant at position 2, inserts the plug of cord circuit 021 into jack'601, and connects ground with the uppermost contacts of jack GM to conductor 021, thereby operating sleeve relay 405, which removes ground with its right outermost back contacts from the right winding of relay 411, which releases, extinguishing lamp 604. The busy lamps, at all positions, however, are maintained operated, by battery connected to conductor 628, by the left innermost contacts of relay 005. If the attendant at position 2 should delay in answering, the attendant at the distant office may recall the attendant at position 3 as in the case of the original call, relays 403, 004, 405 and 40'! functioning as before and effecting the lighting of lamp 605 at position 3. If the attendant at position 2 should find in communicating with the distant attendant that the call should be transferred to some other position,

the transfer may be made in the manner hereinbefore described for the original call. When the plug of the cord circuit 621 is withdrawn from jack 601 relay 406 releases and the winding of relay 403 is reconnected to trunk 400 Without opening the circuit, by means of the left continuity springs of relay 406. Relay 403 reoperates and all apparatus is now ready for another call.

Another feature pertaining to the arrangement of Figs. 4, 5 and 6 will now be discussed whereby the possibility of interference due to the simultaneous transfer of calls from the same position is avoided. Let it be assumed that a call over trunk 400 has been answered at position 3 and that the trunk transfer key 629 has been operated all as hereinbefore described. If at this moment a call comes in over line 49!, associated lamp 653 lights and. the attendant may inadvertently insert the plug of another cord circuit into jack 648 before completing the transfer of the call on trunk toe. It may happen now that the attendant is requested to transfer the call on trunk 40!, and forgetting that the transfer of the call on trunk 40!] has not been completed, may operate transfer key 645, effecting the operation of relay 4 I 3 in the same manner as the operation of relay M6 was previously effected. When a positional transfer key of position 3, key 550 for instance, is now operated, the circuit hereinbefore traced over conductor 649 now branches also through contacts 665 of jack 6 -38, over conductor 641, through outer right break contacts of relay 4I2, over conductor 525, through winding of relay 525, over conductor 52'! to ground on the right outer operated contacts of relay 413. Marginal relay 5I2 now operates in this circuit, but neither marginal relay 5M nor marginal relay 525 operates. Relay 5l2 in operating opens with its left contacts the short circuit around its left winding thereby inserting the resistance of its left winding, and with its right contacts disconnects ground from contacts SIB and 5? of relay 5. Under this condition it is clear that the rotary switches controlled by magnets 582 and 528 do not operate. Marginal relay-533 does not operate and lamp M3 does not light. The failure of lamp M3 to light after key 638 has been held operated for a period of time more than is ordinarily sufiicient to effect a transfer, is an indication that a simultaneous double transfer has been improperly attempted. The attendant will accordingly release key 650, causing relays 632, 635, 509, 5 and EIZ to release. The attendant will also remove momentarily the cord circuit plug from one of the jacks, say jack E48, thereby releasing relay 4 I 3. When the attendant again operates key 656 sequence relays 532 and 635 reoperate and the desired transfer of the call on trunk 400 to position 2 is now effected, and lamp 6l3 lights as hereinbefore described.

The preceding description has been based on the operation of trunk 498, with an incoming call answered at position 3 and transferred to position 2. The operation with the other trunks 40! and 402 is similar, and at other positions the sequence circuit functions in like manner.

Figures 7, 8 and 9 Referring to the other arrangement of the invention disclosed by Figs '7, 8 and 9, the combination of Fig. '7 with Fig. 8 will now be discussed. In Fig. '7 are shown three intercity telegraphic communication trunks 10D, Hit, and 192, which are arranged to cooperate with a cross-bar switch CB which is of the same general construction as that described in Patent No. 2,021,329, issued November 19, 1935 to J. N. Reynolds, from which patent a complete description may be obtained. The function of switch CB is to cooperate over transfer trunk 800 with positional transfer keys shown in Fig. 8 in order to transfer calls to various positions in a telegraphic switchboard line up. The switch GB is shown with trunks 150, NH and 102 connected to cooperate with verticals I, 2 and I0 respectively. Intervening verticals 3, 4, 5, 6, 1 and 8 are omitted as being unnecessary for the purpose of this description, and are symbolized by vertical 9 which is shown unconnected. Only four horizontals are shown, each of which represents positions respectively 1, 2, 3 of Fig. 8, and position 4, not shown. Horizontals 5, 6, I, 8, 9 and IE3 are not shown since these are not necessary in describing the invention. By means of the switch CB ten trunks as 108, ml, i132, etc. may be served, and transferred to any one of ten positions. By using two switches any one of twenty trunks may be transferred to any one of ten positions, or alternatively, any one of ten trunks may be transferred to any one of twenty positions. Furthermore, by using an N number of cross-bar switches connected together horizontally there is provided space for ten times N number of trunk circuits to ten positions; by using M number of cross-bar switches connected together vertically there is provided space for ten trunk circuits to ten times M positions; and by using N number of cross-bar switches connected together horizontally and M number of cross-bar switches connected together vertically there is provided by the joint arrangement ten times N number of trunk circuits to ten times M number of positions, N and M being any desired numbers.

When the attendant at the distant office originates a call on one of the trunks, say trunk 199, by sending a long space signal, trunk N30 is grounded and relays 183, NM and 7105 function so as to operate the lamp 834 at position 1 of Fig. 8, assuming that the night key 8Ul is operated so that this position is now a primary answering position. Also the lamp 818 at position 3 is light-ed over conductor 892, and the busy lamps at all positions are lighted over conductor 8il3. This is in accordance with the cross-connections Hi6 and The answering lamps for trunk IE0 at position 1, when key SM is not operated and at position 2 are lighted only on transferred calls. Any position may be cross-connected so as to function as either a primary or secondary position. In response to a lighted answering lamp associated with trunk mil, the attendants plug into the answering jacks 8B4, 895 or 8%, with the telegraph cord circuits 801, 888 or 339, thereby extinguishing the lighted answering lamps. In order to transfer a call from one position to another, a position transfer key as key 868, 8| I, 812 or M3, corresponding to the position to which the transfer is to be made, is operated. This causes a stepping switch type of control circuit, shown at the bottom of Fig. 8, to function and to associate itself with the position from which the transfer is to be made, provided the control circuit is not then in use at some other position. In operating, the control circuit causes a selecting magnet H38, 109, H0 or HI, corresponding to the position to which the transfer is tobe made, to be energized and then also a holding magnet H2, H6 or H5, corresponding to the trunk 100, It! or 1% which is to be transferred. The contacts of switch CB, corresponding to the intersection of the operated holding and selecting magnet are now closed. When the transfer apparatus has completed its operation, a signal is given to the attendant by the lighting of the positional release lamp Bill, 820 or 82!. The operated position key is then released, and when the plug of the cord circuit, which was used to answer the call, is withdrawn from the answering jack, the lamp at the position to which the transfer is to be made is lighted. A more complete understanding of the operation of the arrangement of Figs. '7 and 8 may be obtained by tracing the progress of a call as hereinafter described.

Let it be assumed that an attendant at a distant switchboard desires to initiate a call over the trunk 99 for the attendant who is located at position 2, which is accessible to trunk 10!! only as a secondary answering position. the conductor of trunk I08 is grounded due to the calling impulse from the distant end a circuit is closed through the left outer contacts of sleeve relay H5, winding of relay ms, to battery on the left back contacts of relay Hi4. Relay H33 operates and closes a circuit through the winding of relay 16 2-, which is traced from battery on the left operated contacts of relay 583, through the winding of relay "504 and the left outer contacts to the conductor of line m0. Relay l'li operates and closes a locking circuit for itself from battery through its left operated contacts and winding through the left break contacts of sleeve relay 7 Hi to the trunk conductor, and also with its left back contacts opens the circuit of relay 703, which releases. Relay 103 in releasing closes a circuit from battery through the winding of relay ""25, right break contacts of relay N33 to ground on the right operated contacts of relay 164. Relay H14 is made slow-to-operate and relay Hi3 slow-torelease, which arrangement necessitates that the calling signal be maintained for an appreciable interval to assure the operation of relay 1G5 and accordingly safeguards the circuit against false signals, due to momentary line disturbances. When the calling pulse is terminated relay 1B4 releases. Relay 135 in operating locks through its right inner contacts to ground on the left inner contacts of sleeve relay H6; with its left outer front contacts it connects battery to conductor 1 il', thence through cross-connection it? to conductor 882, which extends to position 3 at which the answering lamp 8I8 is lighted. Busy lamps 838, 838, 832 and busy lamps at other positions, not shown, are all lighted over conductor 883 from battery on the right outer contacts of relay 785. The attendant at position 3 responds by inserting the plug 853 of the telegraph cord circuit 899 into jack 8% and operating the locking cord circuit key 825, which connects with its upper contacts the position telegraph set 829 through the tip conductors of the plug 853 and jack 8% to the conductor of trunk 166. A circuit is also closed. from battery through resistance 854, sleeve of plug 853 and jack 886, over conductor 833, through winding of relayiiii and right winding of marginal relay N93 to ground. Relay lit operates but relay He does not operate at this time. Relay 1 i6 in operating removes the calling-in signal relays 1533 and 704 from the trunk lfiil with its left outer contacts, and with its left inner contacts opens the locking circuit of relay Hi5, which releases, extinguishing the lamp H8.

The attendant at position 3 is now in tele graphic communication with the distant attendant. Should he be requested to transfer the call to position 2, which is in accordance with the previous assumption he will accordingly operate position transfer key 8! 2, which is'the key for transferring calls to position 2, closing a circuit for operating start relay 835, which is traced from battery through the winding of relay 835 and the right contacts of key M2 to ground. Relay 835 in operating closes a circuit for operating the stepping magnet 836, which is traced from battery through the winding of magnet 836 and its interrupting contacts, left outer contacts of relay 837 to ground on the contacts of relay Key 8H? through its right contacts also connects ground to conductor 838, which extends to contact terminal No. 3 of hunting bank 816, which terminal corresponds to position 3 at which the transfer is being effected. As indicated on the drawings other terminals corresponding to other positions, are numbered consecutively in the direction indicated by the arrow, which also indicates the direction of rotation of the brush arm 839. 7

When the circuit through the winding of stepping magnet 83$ is closed as before described, brush arm 839 and the other brush arms of the switch are stepped around in the direction of the arrows until terminal No. 3 is reached. Ground on terminal No. 3 is reached. Ground on terminal No. 3 of hunting bank 8H3 connected as before described, now operates relay 837, which opens with its left outer contacts the circuit of stepping magnet 83$, thereby preventing the further movement of the switch. A circuit is also closed for energizing selecting magnet 709 of the CB switch, which is traced from battery through the winding of magnet 709, over conductor 840, through left operated contacts of key 8|2, over conductor 84!, through No. 3 contacts and brush arm 842 to ground on the left inner contacts of relay 831. Relay 831 also closes a circuit for operating relay 843, which is traced from battery on the right contacts of relay 837, through winding of relay 8&3 to ground on the left outer con tacts of relay 8%. Relay 53 in operating closes a circuit with its make contacts from battery on the right contacts of relay 831 to ground I through the winding of slow operating relay 844 which looks with its left inner contacts to battery on the right contacts of relay 837. Relay 813 is designed to release slowly to assure that relay 844 locks up before its operating circuit 'is opened. Relay 8 is slow-to-operate to assure that relay 8 :3 operates and its magnetic circuit is saturated before its operating circuit is opened and to assure a sufficient delay in energizing holding magnet H2, after selective magnet 'ifiQ is energized, as will be hereinafter described.

When relay 85*! operates it closes a circuit from battery 845, through resistance 846 and its right outer contacts, brush arm 84?, No. 3 contact terminal of bank 8 i "5, over con-ductor 848, through lower operated contacts of key 826, sleeve conductors of plug 853 and jack 8%, over conductor 833, through winding of sleeve relay H6 and right winding of marginal relay H9 to ground.

Battery 845 is of higher voltage than that of the I battery connected to sleeve resistance 854 and relay H9 now operates and looks from battery through its left contacts and winding to ground on the right outer contacts'of relay H6. Relay 159 with its right contacts connects ground over conductor l2ii through winding of selective magnet 7 82, over conductor 12! to battery on the left back contacts of relay Hi5, which as before stated, released when relay H6 operated. Magnets H19 and H2 are now both operated, operating springs 722, which are located at the intersection of the Vertical and horizontal corresponding respectively to magnets H2 and 789. Relay B44 operated also. closes a circuit traceable from battery on the right contacts of relay 831, through back contacts of relay 843, right inner contacts of relay 844, brush arm 8 39 and contact No. 3 of bank 8! to ground through release lamp 824, which is lighted. The attendant at position 3 observing the lighted lamp 82L knows that the selection has been completed and releases key 812 which releases magnet 109, making it immediately accessible to. the control circuit. Relays 835, 831 and 844 also release and the control circuit is now ready for another selection at any position. Plug 853 is now removed from jack 806, which releases relays 116 and 119. Magnet 112 is held in a locking circuit through its left contacts which circuit is traced from ground on the right outer back contacts of relay over conductor 123 left contacts and winding of magnet 112, over conductor 121 and left back contacts of relay 116 to battery. In order to maintain the circuit of magnet 112 continuously closed, ground is connected by the continuity contacts of relay 116, to conductor 123, before the locking circuit of relay 119 is opened when relay 116 releases. When relay 116 releases, battery on the right inner contacts of relay 116 is disconnected from conductor 803, but the battery on the left back contacts of relay is extended over conductor 121, through right contacts of magnet 112, to conductor 803, thereby maintaining the lighting of the busy lamps. A circuit is also closed for lighting lamp 851 at position 2, which is traced from battery on the left back contacts of relay 119 over conductor 125, contacts 122 of switch CB over conductor 850 to ground through lamp 851.

The attendant at position 2 responds by inserting plug 852 of cord circuit 808 into jack 805, thereby operating relay 116. Magnet 112 releases due to the opening of its circuit at the right outer back contacts of relay 116, and lamp 851 is extinguished.

If, after the lamp 851 is lighted, the attendant at position 2 should delay his response the calling attendant may recall the attendant at position 3, by reoperating relay 105 as hereinbefore described, thereby relighting lamp 818.

In the description hereinbefore given position 3 was cross-connected as a primary, and position 2 as a secondary position. Position 1 is arranged regularly to operate as a secondary position, but when the key 801 is operated it functions as a night position or primary position at which all incoming calls for the switchboard are answered, all other positions at this time being unattended. Key 801 is associated with all trunks over conductor 822 and multiple conductor 126. When relay 105 is operated, as before described, battery is connected, through the contacts of key 801 over conductor 822, through left inner con tacts of relay 105, over conductor 118, cross-connection 106, conductor 823 and through lamp 834 to ground, which is lighted. The operator at position 1 then answers by inserting plug 856 of cord circuit 801 into jack 804, the lamp 834 being extinguished by the operation of sleeve relay 119. Communication is established by operating cord circuit key 824.

Referring now to the alternative arrangement in which Fig. 7 cooperates with Fig. 9, trunks 100, 101 and 102 are associated with jack and lamp equipment in Fig. 9, identical with that of Fig. 8. Also, the cord circuits at each position are the same as in Fig. 8. However, in Fig. 9, instead of a stepping switch type of control circuit a relay circuit, consisting of common relays 900, 901, 902 and positional relays 903, 904 and 905 is used. When one of the positional transfer keys, as 906, 901, 908 or 909 is operated, the associated positional control relay is caused to operate, if the control circuit is not in use, and in cooperation with the common relays of the control circuit effects the operation of the apparatus of Fig. '7 over the conductors of the transfer trunk 800 in the same manner as before described in connection with Fig. 8. A more complete understanding of this arrangement of the invention may be obtained from the following detailed description.

Let it be assumed that a call over trunk 100 causes the apparatus of Fig. '7 to function as before described connecting battery to conductors 802 and 803 and in this case causing the lighting of answering lamp 910 and busy lamps 911, 912 and 913. The attendant at position 3 responds by inserting plug 914 of cord circuit 915 into jack 932. Lamp 910 is extinguished, and the busy lamps remain lighted, as before described. W'hen cord circuit key 916 is operated, communication over trunk 100 is established. Assuming now that the attendant of position 3 is requested to transfer the call, as in the case of the arrangement of Figs. '7 and 8, to position 2, position transfer key 908 is; accordingly operated, thereby closing a circuit from battery through the winding of relay 900, over conductor 918, through both windings of relay 905 in series to ground on the right operated contacts of key 908. If now relay 903, 904, or some similar relay at another position, not shown is not operated, relay 905 operates. A discussion of the means whereby the control circuit functions so as to avoid interference, when a simultaneous attempt to transfer a call is made is discussed hereinafter. Relay 905 with its upper inner contacts short circuits its high resistance upper winding, which so reduces the resistance of the circuit that relay 900 operates. Relay 905 continues to hold on its lower winding. Relay 900 operated closes a circuit from ground on its left contacts, over conductor 919, through upper outer make contacts of relay 905, left operated contacts of key 908, over conductor 840 and to battery through the winding of selecting magnet 109, which operates. Another circuit is closed from battery through the right contacts of relay 900, winding of relay 901 to ground on the left outer break contacts of relay 902. Relay 901 operates and operates relay 902 in a circuit from ground through the winding of relay 902, front contacts of relay 901 to battery on the operated right contacts of relay 900, to which relay 902 looks through its left inner contacts. Relay 902 releases slow release relay 901 and with its outer right contacts connects battery 920 through resistance 921 to conductor 922, through lower outer contacts of relay 905 to conductor 923. From conductor 923 battery 9201s extended through the lower operated contacts of cord circuit key 916 to the sleeve circuit of plug 914 and jack 932. Battery 920 is of higher voltage than that of the regular sleeve circuit battery hence marginal relay 119 operates as before described in connection with Fig. 8 and energizes hold magnet 112, closing contacts ,122. Another circuit is closed when relay 901 eventually releases from battery on the right contacts of relay 900, break contact of relay 901 through right inner contacts of relay 902, over conductor 924, through lower inner contacts of relay 905 to ground through lamp 925, which is lighted, indicating to the attendant that the selection has been completed. Key 908 is now restored to normal which releases relays 900, 902 and 905 extinguishing lamp 925. Plug 914 is now withdrawn from jack 932 and lamp 926 at position 2 lights. The attendant at position 2 answers the call by inserting plug 921 of cord circuit 928 into jack 929. and operating cord circuit key 93.0. From this point, the description in connection with Fig 7 and Fig. 8 applies.

The means whereby interference. is avoided, if attendants at diiferent positions attempt to transfer calls simultaneously will now be discussed. When key 908 was operated as before described it was assumed that the common control circuit was not then in use. Suppose, however, that the circuit being used at position 2, that the associated relay 9% is operated and: the upper high resistance winding of relay 9% is short-circuited and connected to ground through the operated right contacts of key 93L Under this condition the two serially connected windings of relay 905 are shunted by the low resistance lower winding of relay 9534- Relay 9&5 is marginal under this condition and does not operate. Consequently position 2 encounters no interference from position 3. If key 898 should be operated simultaneously with key 93l relays 95 i and 965 would then operate together. If each relay should close its upper inner front contacts simultaneously and short-circuit its upper winding then the individ ual current flow through the respective lower windings of relays 9M and 905 would be so. small that the relays would immediately release. now one of the relays, say relay 994, should re lease before relay 9125, then the low resistance shunt on the winding of relay SE55 is removed and relay Q35 holds, and at the same time shunts effectively the two serially connected windings of relay 904, which continues in' the released condition.

If the attendant at position 2, to which position the call answered at position 3 was transferred, should be required to retransfer the call to some other position, this may be done in the case of both Figs. 8 and 9 in the same manner as in the case of an original call at a primary position.

The operation of the arrangement of Figs. '7, 8 and 9 has been discussed on the basis of calls incoming over trunks Hi0, ml and 582. This arrangement, however, is equally well adapted to handle outgoing cal-ls.

with the trunk over which the call is to be transmitted and operates the cord circuit key. By sending a spacing signal, i. e., grounding trunk for a short period of time causes the signal rality of auxiliary circuits connected in multiple.

to each of said switching devices and termina ing at said switchboard, a primary signal lamp path and a plurality of secondary lamp paths associated to each of said auxiliary circuits and respectively having. appearances at different sections of said switchboard, a lamp in each of said paths, a keyset at each section of said switchboard comprising keys for initiating the transfer of an incoming call signal to a lamp in any desired secondary lamp path, and switching means I associated with each of said auxiliary circuits for automatically completing the transfer of a call signal incoming over any one of said trunk circuits and appearing at one of the sections of said switchboard, to any one of the other sections of said switchboard.

To initiate a call an attendant plugs into the answering jack associated 2. In amanually operated switchingsystem, a switchboard divided into a plurality of sections, a plurality of two-way trunk circuits terminating in said switchboard, a plurality of auxiliary circuits associated with said trunk circuits terminating at each of said sections, a primary signal lamp path and a plurality of secondary lamp paths associated with each of said trunk circuits and respectively having appearances at different sections, a lamp in each of said paths, a keyset at each section comprising keys for initiating the transfer of an incoming call signal to a lamp in any desired secondary lamp path, switching means associated with each of said auxiliary circuits for automatically completing the transfer of the incoming call signal appearing at one section to any one of the other of said sections, and other auxiliary circuits controlled by each of said keysets and each of said switching means for transferring an incoming call signal transferred to a secondary signal lamp to any one other secondary lamps of said plurality at any other of the other of said sections as desired.

3. In a manually operated switching system, according to claim 2, wherein the said lamp paths are provided with means for cross-connecting each of said lamp paths to have either a primary lamp path appearance or a secondary signal lamp path appearance at any one of said. switchboard sections'as desired.

4. In a manually operated switching system, a switchboard divided into a plurality of primary sections'and into a plurality of secondary sections, a plurality of trunks for two-way messages, a switching device, a plurality of circuits accessi ble to said device and respectively terminating at the primary and secondary answering sections of said switchboard, indicators individual to certain of said circuits respectively appearing at said primary section, indicators individual to the other of said circuits respectively appearing at said secondary section, and means at each of said primary and at each of said secondary sections. for transferring a signal appearing on any one of said indicators, primary or secondary, toany one of the secondary sections.

5. In a manually operated switching system, a switchboard divided into a plurality of primary sections and a plurality of secondary sections, a plurality of trunks for two-way messages, a rotary stepping switch individual to each of said trunks, a plurality of auxiliary circuits accessible to each of said switches, primary trunk indicators individual to' certain of said auxiliary circuits and respectively appearing at said primary section, a secondary trunk indicators individual to the other of said auxiliary circuits and respectively appearin at said secondary section, means asociated with each trunk for selectively actuating the associated trunk indicator at any of said primary or secondary sections, transferring meansassociated with each section for initiating the transfer of a secondary or primary signal on any of said indicators to any selected-section and for causing the functioning of the selecting means aforesaid, a transfer trunk common to all trunks and to all switchboard sections interconnecting said selecting means and said transferring means, and means whereby said transfer trunk is effective for the transfer of only one signal at a time thereby avoiding circuit interference.

6. In a manually operated switching system, a switchboard divided into a plurality of positions, a plurality of trunk circuits for incoming and outgoing messages, a plurality of circuit paths comprising, a primary signal lamp path and a plurality of secondary lamp paths accessible for connection to each of said trunk circuits and respectively having appearances at different positions, a lamp in each of said paths constituting an appearance, a key set at each of said positions comprising keys for initiating the transfer of incoming call signals on a primary or a secondary signal lamp to any desired secondary signal lamp, and a cross-bar switch common to each group of ten trunk circuits arranged totransfer an incoming call signal transferred to a secondary signal lamp to one of the other secondary signal lamps at any of the other of said positions as desired.

'1. In a manually operated switching system, a switchboard divided into a plurality of primary positions and into a plurality of secondary positions, a plurality of trunk circuits for two-way messages, a rotary switch terminating each trunk circuit, a plurality of circuit paths accessible to said switch and terminating in said switchboard at said primary and said secondary positions, primary trunk signals individual to certain of said circuit paths and respectively appearing at said primary positions, secondary trunk signals individual to certain other of said circuit paths and respectively appearing at said secondary positions, means associated with each trunk for selectively actuating the associated trunk signal at any one of said primary positions, transferring means associated with each position for initiating the transfer of a primary trunk signal to any selected position and for causing the functioning oi the selecting means aforesaid, a transfer trunk circuit common toall trunk circuits and to all switchboard positions interconnecting said selecting means; and said transferring means, and means whereby said transfer trunk circuit is effective for the transfer of only one signal at a time thereby avoiding interference between trunk circuits.

ALLEN R. BONORDEN.

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