US899787A - Telephone system. - Google Patents

Description

A. H. DYSON.

' TELEPHONE $YS'IEM. APPLICATION FILED FEB. 5, 1906.

Patented Sept. 29, 1908. s SHEETS-SHEET 1.

A-. H. DYSON. TELEPHONE SYSTEM.

APPLICATION FILED FEB.5,1906.

Patented Sept. 29, 1908.

3 SHEETS-SHEET 2 A. 11-. DYSON.' TELEPHONE SYSTEM.

APPLICATION FILED FEB. 5,1906.

- Patented Sept. 29, 1908.

3 SHEETS-SHEET 3 UNITED STATES PATENT orrion ILLINOIS.

ALFRED H. DYSON, OF CHICAGO, ILLINOIS, ASSIGNOR TO MILO G. KEILLOGG, CHICAGO,

TELEPHONE SYSTEM.

To all whom it may concern:

Be it known that I, ALFRED H. DYSON, re-

, siding in the city of Chicago, county of Cook,

and State of Illinois, have invented new and useful Improvements in Telephone Systems,

of which the following is a'specification.

My invention relates Inore particularly to multiple telephone-exchange switchboards. It has heretofore been the iractice, in constructing switchboards of this character, to provide a line-signal for each subscribers ne and an answering spring-jack associated therewith,- with operators cord-connecting apparatus, whereby the operator connects In, the system herein shown, I retain the line-signal and answering-jack mentioned,

above, but the multiple terminals of subscribers lines are not placed within manual reach of the operator, but may be placed at any other convenient or desired point, the

- operator having control of 'electro-magnetically' operated step-bylstep switching mechanism, by means whereof sheis enabled to extend the-line of the calling subscriber to multi le terminals of the called line, located at a istance from her position.

. The object of my invention is to provide a sim le and efiicient structure of the descri ed character.

Among the advantages secured by my invention, may be mentioned the followin Telephone exchange switchboards originally installed as non-multiple boards, and which it would be impossible to change over to a multiple system, should this become desirable, because there would not be space in the switchboard cabinets for multiplev spring jacks, may, by the-employment of my invention, be readily converted intomultiple boards, since, to change to a multiple system, as will be apparent from the description of my invention, very little space in the switchboard is required. I

Another advantage, which may be secured by my invention, is found in its use when employed for trunking between distant exchanges. Hitherto, in manual exchange from one exchange to the other. ployment of my invention, a single trunk m- Specification of Letters Patent. Application filed February 5, 1906. -"Seria1No. 299,558.

Patented Sept. 29, 1908.

practice, two operators have ordinarily been employed in such work, it being inexpedient from the viewpoint of cost and also switchboard space, to extend multiple circuits of lines terminating in one exchange-to a distant exchange. By the employment of my invention, it is possible for an operator in one exchange to connect a calling subscribers line with multiple terminals of subscribers located at a distant exchange without the intervention of a second operator, as will be more fully explained in the'following description. It would, of course, not be practical to provide each subscribers ling) terminating in one exchange with multiple terminals at a distant exchange on account of the extreme expense that would be involved in so doing consisting in providing an indi vidual trunk circuit for each line extending In the emcluding three conductors extending from a spring jack at one exchange to the circuits of a connector switch at a second exchange provides facilities whereby an-operator may connect a calling line at her own exchange with any one of a hundred subscribers lines terminating at the distant exchange and having multiple terminals appearing in the banks of the said connector switch.

While I show and describe my invention in the form of a structure employing a single step-by-step switch only to complete agiven connection which switch is, of course, a connector, it is not my intention to be limited to the employment of a single switch inasmuch as the employment of auxiliary switches of one or more classes in association with connectors,,is well known in the art, having gone into extensive commercial use in the United States. By the employment of. auxiliary switches in association with connectors, it is, as is well-known, possible-to select automatically any line desired out of a numa her as large as 10,000, or out of even a greater number.

Re. rring to the drawings, Figure 1 illustrates a step-by-step switch, such as may be employed in' connection with the circuits shown at E in Fig. 6, and II in Fig. 8'; Fig. 2 1

illustrates a primary magnet of said switch and its associated par-ts. Fig. 3 illustrates a secondary magnet of said switch and its associated parts. Fig. 4 shows a sectional 'view of the switch-shaft together with the primary magnet and its associated parts.

Fig. 5 illustrates, in perspective side-switch arms and their associated contacts. Fig. '6 illustrates, diagrammatically, magneto telephone exchange circuits arranged in accordance with my invention. Fig. 7 illustrates a grounded magnet-o line circuit arranged in accordance with my invention. Fig. 8 illustrates a common-battery multiple switchboard telephone exchange system arranged in accordance with my invention. In Fig. 9 I show an arrangement whereby the spring jack terminal of the circuit H shown in Fig. 8 is provided with a busy test;

Referring to Fig. 1, the structure there shown is known in the art, and I do not claim it as my invention. -A shaft 47 is provided to which are rigidly attached .fvvipers 32, 33 and 34. Associated with wipers 32 and 33 is a bank of one hundred pairs of contacts arranged in vertical and orizontal rows of ten pairs zontal rows being curved so that the bank presents a concave surface. Associated with wiper 34 is a bank of one hundred single contacts arranged in rows as described. All the contacts in the bank are insulated from each other and are multiple terminals of subscribers lines.

Shaft 47? is journaled to the frame of the banks and is capable of being raised upward with respect to the banks, by means of primary magnet 31, and of being rotated with respectthereto, by means of secondary magnet 40. By means of these magnets, wipers 32 and 33 may be moved to engage any desired pair of contacts in their associated bank, the arrangement being such that wiper 34 at the-same time will always engage a contact of its bank whose relative location will correspond. to that of the pair of contacts engaged. Each pair of contacts and its correspondingly located single contact form a set which constitutes the ter minals of a single subscribers line. Thus the system is what may be called a three wire multiple switchboard. The cycle of operations for the switch shown in Fig. 1 is briefly, as follows:Primary magnet- 31 'is operated to cause wipers 32, 33 and 34 to select the desired levels of the contact banks. Private magnet 36 is then operated to throw side-switch arm 30 to engage its alternate contact 37. Secondary magnet 40 is thereupon operated to cause wipers 32, 33 and 34 to select the particular contacts desired from among those of the selected levels, such contacts forming the terminals of the particular line desired. Private magnet 36 isthereupon operatedto throw side-switch arm 30 to engage the third contact 43. This completes the selection of the line. Release magnet 42 is provided for the purpose of restoring the switch at the end of conversation. It should be remarked at this time, that, should the line'whose terminals are selected,

each, the horinumbered 47 and 48 which would be terminals of line 89 of the one hundred lines terminating in the bank, eight impulses of current are caused to flow through primary magnet 31. The first of these, in attracting the magnets armature, causes pawl 31, illustrated in Fig. 2, but which is concealed by its associated ratchet in Fig. 1, to engage the first tooth of the ratchet and lift the shaft a single step upward- The attraction of the ma nets armature also causes lug 31*, attac 16d thereto, to move arm 31 to disengage double detent 31 which latter moves towardthe shaft, engaging with its upper ortion a tooth of the vertical ratchet and olding the shaft in its raised position. The first movement of the shaft frees arm 30" which, being pivoted as shown, is caused, by its associated spring, to rotate about its pivot, releasing pawl 30" preparatory to its movement as hereafter described. Successive im ulses, caused to flow through magnet 31 ift, by means-of pawl 31, the shaft successive steps upward, detent 31" engaging successive ratchet teeth after each thrust and maintaining the shaft raised. The teeth of the ratchet associated with pawl 31 are so spaced that each upward movement of the shaft brings the wipers topositions level with successive rows of horizontally disposed .contacts. The next step in the operation of the switch is the cnergization and dcenergization-of private magnet 36. Said magnet, in attracting its armature, causes a downward movement of ratchet 36 attached to its arn'iature, so that the. lug 30" upon sideswitch pawl 30 is brought to such position that it engages tooth c of ratchet 36, the said tooth being staggered with respect to tooth 0. Upon the deenergization of magnet 36 and the retraction of its armature ratchet .36 moves upward so that lug 30 slides down over tooth c and engages tooth b. Paul 30 being pivoted as shown, and attached to arm 30, the latter is moved to disengage its normal contact and to engage contact 37. Secondary magnet 40 is now caused to be energized and denergizcd nine times. The shaft of the switch carrying wipers 32, 33 and 34, having been by the eigl'it impulses through primary magnet 31 raised to positions level with the horizontal rows o'l contacts including 47 4S and 49, the first impulse caused to llow through 40 by attracting its armature to which is attached pawl -10 el'l'ects a thrust of the said pawl, which by engaging a tooth of its associated ratchet shown in Fig. 3, moves shaft 47 in a wipers 32, 33 and 34 to engage the contacts at the extreme left of the selected rows.v

' contact 37 and to engage contact 43.

the release of the swltch 1s deslred, an imlevels.

Each of the nine impulses mentioned efiects a thrust of pawl 40, each thrust bringing the switch wipers into engagement wit a successive pair of contacts and a single contact of the selected rows. impulse will, therefore, cause wipers 32, 33 and 34 to engage the contacts 47, 48 and 49 respectively, assumed to be terminals of the line desired which would, from the positions of the contacts in the banks be terminals of line 89 of the particular hundred lines 'having their terminals in the banks of the switch unden'description. Detent 31 engages successive rotary ratchetteethof the shaft holding it in each rotated position.

A second energization and 'denergization of the side switch magnet 36 operating in a manner similar to that before described, brings the lug 30 to engage tooth a, whereby side-switch arm 30 is moved to disengage When pulse of current is caused to flow through release magnet 42, which by attracting its armature moves arm 42 pivoted/to the armature to the right, in such manner that the movement of its right extremity, which engages the pin shown upon the pawl 30,

. moves the pawl to such position, that lug 30" is again brought into engagement with tooth c, rotating pawl 30 and arm 30 to normal,

the latter then engaging its normal contact.

'ihe described movement of arm 42 to the right, by the engagement of the hook at its left extremity with the pin shown upon double dctent 3] 0 moves the said detent away from the ratchets of the shaft and to such u pon detent 31, holding the detent in its retra'cted position. The disengagement of.

the shaft ratchets byv detcnt 31 leaves the shaft in a position to be freely rotated by spring 47, against-the torsion of which the shaft was rotated in selecting terminals 47, 48 and 49. The shaft, therefore, rotates in a reverse clockwise direction until wipers 32, 33 and 34 reach a. position beyond the contacts at the extreme left of the selected When in this position, stationary deten't 47", normallyin such position as to be in the depression of the vertical ratchet shown in Fig. 2, but which with the first rotary movement of the shaft is always brought to engage atooth of the vertical ratchet and so hold the shaft inits raised position while-being rotated, is brought to-a posi tion wh re it again engages the said depression leaving the shaft freeto descend to its normal position, which it does under the influence of gravity assisted by the tension of spring 47 As the shaft reaches its normal position it engages, 'with the lower edge of The ninth and last"- a plurality of circuit changing arms may be associated with pawl 30 together with their appropriate sets of contacts, so that each movement of pawl 30' may be employed to effect a plurality of simultaneous circuit changes. The customary off-normal switch including arm 29" fastened to the upper por-' tion of the shaft is provided, which, in this structure, is adapted with the first upward movement of the'shaft to remove tension from the middle one of the three'springs shown associated with it, whereby contact with the other upper spring is closed. Referring to Fig. 6, I show at A, in diagrammatic form a local battery substation circuit inclnding the usual hook-switch,- generator, bell, transmitter, receiver and induction coil. 1 and 2 are the two limbs of the telephone line extending to the exchange,

limb 1 being connected to spring 3 of the answering spring jack of the line, while 2 is connected to spring 10 of the spring jack. Normally in bridge of the two line limbs at the exchange is the winding of line drop 5, the

circuit of which is arranged to be opened 100.

at a normally closed contact of switch spring 3 upon the insertion of a plug into the spring jac and at a normally closed switching contact of cut-off'relay 6 upon the energization of said relay. In multiple with switch spring 3 are switch contacts 47 and 47, while in multiple with switch spring 10 are contacts 48 and 48". The sleeve 9 of the tipled to contacts 49 and-49. It will thus be seen that the subscribers line is provided with the usual answering spring jack termi- -nals and line drop and in addition 1s provided with terminal- contacts 47, 48 and 49 10- 1'15 catedin the contact banks of a connector such as that shown in Fig. 1, while contacts 47, 48 and 49 are located in the contact banks of a second such connector. Obviously the spring jack contacts of the line of A may be multipled to as many connector contact banks as may be desirable for the operation ofthe exchange.

At D in Fig. 6 I show a cord circuit arrangement including the usual clearing out drop '50 shunted by a condenser, in order that its impedance. may not affect the voice currents, the operatorstalking set and listening-in key, together with a ringing-generator 51 and the usual ringing key. In addition is 13.0

between springs 23 and 24.

provided a calling device or dial 18 diagrammatically represented as a disk having upon itsperi hery ratchet teeth of insulating material, t 10 disk being adapted for rotation in the direction indicated by the arrow, and being adapted upon its release after such rotation to return to normal in the opposite direction under the influence ol lie-spring shown. This calling device is adapted when rotated and released to close contact between springs 21 and 22 a number of times dependent upon the extent of its rotation, and it reaches normal to close contact a single time A stop is provided upon the. device adapted, when the device is in other than its normalposition to relieve tension from sprin 20 whereby the said spring opens its normally closed contact with spring 19.

At 25 and 26, I have. shown the lovers of a key adapted when the said levers are. thrown,

to engage their alternate. contacts to connect springs 21 and 24, associated \Vltll calling device 18, to-co'ntacts 14 and 16 of the calling plug of the cord circuit respectively.

At E, I have shown the circuits of a connector switch including primary magnet 31,

secondary magnet 40, private magnet 36, re-

lease magnet 42, and a release relay 41 arranged to control the operation of 42 Sideswitch arms 30, 35 and 35 are provided with the usual normal, alternate and third c0ntacts. Like arts appearing in Fig. 1 and at E in Fig. fi'iiave like reference characters. It is to be ugderstood that the circuit at E is that employed for operating the switch structure shown in Fig.1, the mechanical parts, other than the-magnets of Fig. 1, being in general omitted in Fig. 6 for thesake of clearness in the circuit drawing. I have,-

however, shown the shaft and wipers as, on and 34 associated with which wipers are contacts 47, 48 and 49, assumed to be. located in a'position corresponding to the lo =ation of 47, 48 and 4S), shown'iu Fig. 1. To avoid confusion, the remaining contacts of the banks, wherein 47, 4S and 49 are included, are omitted in the circuit drawing. 1 have indicated at 4'1",45 and 4!), multiple contacts of 47, 48 and 4Sl,'which are to be regarded as included in the banks'o'l' a connector switch, other than that shown 'at E, but having identical circuits and mechanism.

At B I have showi'l a second substation connected by its telephone line with its be as follows:ilhc 500 lines would conveniently be dividcdi ito groups ol 100 ea h, and a switchboard havin five operators positions would be provided, each operator having before her in the switchboard l'rame, line drops and answering jacks ol the lines of one of these groups. The terminals at. the exchange of each of the subscribers lines of each group would be multiplied to a plurality of connector switches having circuits such as shown at. E, appearing at said switches in the form of bank cont acts. Each operator would be provided with a plurality ol trunk jacks in addition to the br-l'orc mentioned answer ing jacks, the said trunk jacks being terminals of (Ollfitttfll' switches. In an exchange. oi the size above specified, the provision at each operators position of two trunk jacks, terminals of connector switches assigned for connection to each 100 line group (other than the group of the position), would under ordinary conditions of service. give adequate facilities for the prompt completion of calls.

.In completing connectionsbetween two subscribers both ol whose lines have their line drops and answering jacks at her own position, the operator having tested the called line in the usual manner would complete the (wnncction directly by the calling plug without the use ol the selective switch. Thus, each ol' the 5 operators would have at her position 8 spring jack terminals of connector"switches. Upon receiving a call-from a subscriber other own group, who desired to converse with a subscriber whose linev is included in another group, the operator would insert the calling plug of the cord circuit D in a trunk jack of a connector assigned. to the one hundred line group among which the line oi the called subscriber 'is included, and would complete the connection by operating the calling device 13, which controls the connector switches. Que calling device is )1'0- vided for each operators position, while a key is provided for each cord circuit enabling the operator to connect the calling device with an cord circuit desired, this being in a general way similar to th arrangement of the opclatons talking set with respect; to all of her cords. Obviously the connector switches may be placed at an convenient point in the same room with the switchboard sections, or in another room, or in a distant exchange, the only apparatus connected with them. and required to be wit-bin reach of the operator being the spring jack terminals of the said connector switches.

The operation of the systen'i is as follows Assuming that subscriber A desires to be connected with the line' of subscriber B whose number is assumed to be 289; subscriber A operates the generator at the substation, "current therefrom passing through the winding of drop 5 to attract its armature, releasing the drop shutter, which falls the signal, inserts the answering plug of cord clrcuit Dinto the s ring jack of the calledline, tip 7 of the p ug engaging contact 3 of the spring jack and simultaneously openin contact34,' cuttingoff the win ing of rop 5 from limb 1 of theline. Upon the insertion of the plug, sleeve contact 8 connects with both of contacts 9 and 10.

Current now flows from, ground G at the cord circuit, through contact 89, winding of cut-off relay 6 to the active side of battery 11, energizing-the cut-off relay which. at tracts its armature. It will be seen that ground-Gr is at this time connected to pri ,vate contacts 49, 49, etc., connector terminals ofthe calling line, thesaid line being thereby'rendered busy with respectto connector switches having access to it, in the well known manner. -The oplerator now throws over levers 1213 of er listening key and learns from the calling subscriber the number of the line wanted. Assuming the line wanted, No. 289, to be included in ,a group other than that whose lines have.

their sprin jacks in front of the o erator, she raises t 1e calling plug of the cor circuit used in answering and inserts it into the spring jack of a trunk circuit connected to a connector switch, assigned to lines Nos. 200

- to 299 inclusive. ()n the insertion of the plugfauxiliary spring 15 is caused to disengage contact 29. The connector selected is assumed to be that whose circuit is shown at E. The operator restores her listening key, and throws over levers and 26 of her calling key, thus placing calling device 18 in operative relation with the connector switch.

The operator now rotates dial .18 until eight teeth have-passed to the right, of spring 21. Released, .thefdial returns in the opposite di rection closing and breaking contact eight times between springs 22 and 21. With each closure of contact between said springs,

an impulse of current flows from ground Gr through contact 22-21,' through lever 27 of the, ringing key, lever 25 of the calling key, pliig and jack contact I l--15, side switch arm 30, primary magnet 31 to the active side of battery 11. The prii nary magnet is thereby energized and denergized eight times and liftsthe shaft of the connector eight steps upward, bringing wipers 3233, and 34 level with the eighth rows of horizontal contactsof their associated banks, counting from below? The ninthcontacts counting ji'roni' the le'ft of these rowswill be the terminals of line 89 of the particular group or of line 289. T

and 21.

With the return of the dial 18 to normal, contact is closed and broken between springs 24 and 23 a single time-at a period subsequent tothe last closure between springs 22 An impulse of current is thereby caused to flow from ground G2 through springs 2324, lever 28, lever 26, plug and jack contact 16'17, side switch arm 35, private magnet 36 to the active side of battery 11. 36 is thereby energized and denergized, whereby arms 30, 35 and 35'disen' gage their normal contacts and en age contact points 37, 38 and 39 respective as will be understood from the preceding description of Fig. 1. The 0 erator now causes nine impulses of current, y the operation of dial 18, to be transmitted from ground Gr through contact 22, 21, lever 27, lever 25, plug and jack contact 141.5, contact 37 through the winding of secondary magnet 40 to battery-11. The resulting energizations and deenergizations of secondary magnet 40 cause nine rotary step-by-step movements of the switch shaft bringing wipers 32, 33 and 34 into engagement with contacts 47, 48 and 49, forming multiple terminals of the desired line. With the return of dial l8.to normal a single impulse of' current flows from ground (l over the before traced path to side switch arm 35, through contact 38 and the winding of private magnet 36 to battery 11, causing 'a second energization and decnergization of .36, which causes arms 30, and 35 to engage contacts 43, 44 and 45 respectively. Arms 30 and35, in leaving their alternate contacts 37 and 38 to engage contacts 43 and 44,-cut ofl" secondary magnet 40 and private magnet 36 from the talking strands of circuit E, indicated by the heavy lines. By enga ing contacts 43 and 44 they comple'tethe ta king circuit of E through to wipers 32 and 33 and to the limbs of the called-for line. Arm 35 by engaging contact 45' connects ground G to private Wi or 34 and private contact 49 and its multip es of the called-for line, rendering the line busy with respect to other connector switches having access to it. Sleeve contact.9 of the spring jack of the called line is also connected to groundG, thereby providing a busy test forthe called line, inasmuch as the tip contacts of the calling plugs of all operators, positions are connected to battery when the listening key is depressed,

tion of cut-ofi relay 6 of the calledline which attracts its armature to open the circuit. of

drop 5. The. operator connecting the lines ofsu bs cribers and B now throws her levers 27 and 28 of her ringing key, connecting generator 51 in circuit with the line of subscriber B, and causing his bell to rin 1 She thereupon restores levers 27-28 and also levers 26 of the calling key, thereby completing connection between the two subscribers lines and conversation ro ceeds upon the response of the called su scriber, .the talking circuit being traced from substation A, over the heavily marked line conductors, through cord circuit D, over the heavily marked conductors at connector circuit E, and over the heavily marked line conductors of the line of subscriber B.

When the subscribers have finished their conversation, they replace their receivers and operate the substation generators. When either one does so, current from his generator flows through the winding of clearing out drop 50 at cord circuit D. The armature of said drop is attracted and the drop shutter falls, thus notifying the operator that conversation is finished. She thereupon withdraws the answering plug from the calling subscriber's line, restoring the line circuit to normal. She also withdraws the calling plug from the trunk jack. Jack spring 15 thereupon'resumes its normal position, and auxiliary contact 15 again engages contact 29. ment of the connector shaft when initially operated, oil-normal switch 29 engaged its front contact. l'lence, at the closing of contact 15-29, current will llow from ground G through said contact, through switch arm 2i), and winding of release relay 41 to the battery 11. Contact is, by .the resulting energization of 4], closed from ground Gr through the winding of release magnet 42 to battery 11 and the release magnet attracts its armature restoring the switch to normal, as described in connection with Fig. 1. The line of subscriber B is thereby placed in its normal position, and the busy test potential is rleinoved from sleeve contact 9-o'f1ts spring ac i.

should the line of the called subscriber be already in use, when the wipers of a connector switch are brought to rest in engagement with contact-terminals of said line, the connector will automatically be released and returned to normal. It will be noted that if a subscribcfls line is a busy line, due to a connection having been made by a plug of a cord circuit such as l) to its spring jack, sleeve contact 9 of the line jack and its multiple contacts 4S)4t9 will be connected to ground (l at the cord circuit; on the other hand, if the line is busy, due to connection having been made therewith by a connector, its sleeve contact 9 and its multiple contacts 49-49 will be grounded at ground G of the connector.- Assuming that the line of subscriber B is busy, and contact 49 therefore grounde at the time wipers 32, 33 and 34 of switch 1) engage terminals 47, 48 and 49 re- With the first upward move-.

I will now describe the means whereby,

spectively, it will be observed that when the impulse of current flowing from ground G", with the-return of calling device 18 to normal, through contact 23-24, levers 2S and 26, contacts 16-17, 35'-38, through privat ma net 36, causes the energization of the said private magnet, there will, upon the engagement of armature of 36 with its associated front contact, be established a path for the flow of current as follows: from grounded contact-terminal 49 of the called line, through wiper 34, and contact 3539 (the switch arms being moved only upon the dcenergization of the private mag-not) through armature of private magnet 36, its front contact, winding of release relay 4] to battery 11. The cnergization of 41 closes circuit through release magnet 42 and the connector switch returns'to normal. This is the means above referred to, whereby 'a' connector will be automatically released when its wipers are caused to engage terminals of a busy line, the result being that an existing conversation cannot be interfered with. U on the release of the switch, occurring at this time, the operator receives a busy signal from the int errupter 46 as soon as side switch arm 30. with the release, is brought to engage its normal contact. The path for the interrupted tlow ofcurrent notifying the operator that the called line is busy when the connector is re leased, may be traced from interrupter 46, by induction through condenser 46, through its normal contact to side switch arm 30, contact 15] 4 through lever 25 (at this time dcpressed) through lever 27, through contact 19-20 (dial 18 being at this time in its normal position) through the operators receiver and to batterv 1]. it will be noted that this path is independent of the )osition of levers 12 and 1.; of the listening toy. The operator, upon hearing the signal atthis time, withdraws the plugs, after advising the calling subscriber that the line wanted is busy. .lt will be noted that the operator immediately on. inserting the calling plug into the spring jack of a connector and deu'essing' the lovers 2:) and 26 of the calling soy, will receive the busy signal until such a time as side switch arm 30' is moved, under the inlluence of 3G,. to disengage its normal contact and to engage its alternate contact 37. The operator however, pays no heed to the signal at this time, under instructions to this effect.

In Fig. 7, I show the arrangement 'of a substation the line circuit at the exchange employing a single line conductor 1, the other conductor 2 shown in Fig; (i being dispensed with, ground indicated at 2, 2 and 2 being employed in its place. This arrangement is adapted for use in connection with the cord circuit shown at D and the coilnector shown at E of Fig.

In Fig. 8, I show the application of the character.

3 provided with multiple terminals forming placing broad features of my invention to a multiple telephone exchange system of a well known illustrated, extending by their line limbs 1 and 2 to the exchange, and there provided with answering and multiple spring jacks, one only of the latter being shown. Said lines, in addition to the spring'jacks, are

ank contacts of connector switches. The general. arrangement ofthe bank contacts may be such as that described in connection with Fig. 6, as may be. the division of the lines into groups, one group being assigned to' each of a plurality of operators. The provision for each operator of two or more trunk spring'jacks connected to connector switches assigned to individual groups of one hundred subscribers lines would be retained. The substation at F is'arranged for common battery talking, and comprises the usual hook-switch normally maintaining the condenser and call-bell in bridge of the two line limbs, the said switch being adapted upon removatof the receiver to place the bell in open circultand connect the transniitter into circuit with the metallic circuit of the line. The signaling circuit for the line at the exchange is well known character, comprising the line relay 50 controlling by its armature the local circuit'of the line lamp 51. Forming a part of the line circuit is also the cut-off relay 53 connected to the sleeve contacts of the spring jacks and adapted upon the insertion of a plug into the spring jack to open the circuit of the line relay and connect the two line limbs to the multiple connection terminals of the line. The cord circuitshown at Fig. 8 is also of well known character, including an answering plug comprising contacts 55 and 59, associated with which are the supervisory relays56 and 58, under whose joint control is the answering supervisory lamp 57. The cord circuit includes also the calling plug comprising contacts 63 and 65, associated with which are the supervisory relays and 7 2, controlling jointly the calling supervisory signal lamp 71. A test relay is provided, normally in circuit with the tip contact of the'calling plug in the usual manner. talking circuit is also provided and a listening key comprising levers 61 and 62 individual to the cord circuit for connecting the talking set with a subscribers line. The arrangement of generator 51 and its associated ringing key is also well known in the art. For each opcrators position is provided a dial or calling-device 18, similar to that already described in connection with Fig. 6, and for each cord circuit is provided acalling key, comprising levers 25 and 26 adapted for with the calling plug.

At H in Fig. 8, I have shown a connector The substations F and G are An operators 1e dial 18 into operative relation.

circuit diflering from that shown at principally in respect to the arrangement for releasing the switch as will be more part cularly pointedout hereafter. The mechanical features of the switch operated by means of circuit H may be substantially the same as those disclosed in Fig. 1 with the following exceptions. I First, that wiper 34 is omitted together with its associated contact bank, two wipers 32 and '33 only being required m connection. with the circuit arrangement of' H secondly, the off-normalswitch shown at is arranged, with the first upward movement of the switch shaft, to disengage its associated contact instead of engaging it, as off-normal switch 29 shown at E in Fig. 6 is arranged to do. The substation shown at G is provided with a circuit similar to that of the'substation at F and its line circuit at the exchange is similar to the line. circuit. connected with substation F.

Assuming, that the subscriber F desires to be connected with the subscriber G, whose number is 289, subscriber F, by removing his receiver, closes circuit through line relay '50, which by attracting its armature effects the illumination of line lamp 51. The operator observing the signal inserts the answering plug into the answering jack, closing contacts 5960 and 55-54. Current flows from gpound G f through cut-off relay 53, throng contact 54-55, supervisory relay 56 to the active side of battery 52. This causes the energization of cut-oil relay 53, which 'by attracting its armature connects the limbs of the line to contacts 5-1 and 60 of the s ring jacks. Relay 56 is energized also,

. and y the attraction of' its armature would cause the display of supervisory lamp 57, were it not for the fact that relay 58, is,'upon the energization of cut-ofi' relay 53, energized by a-ilow of current from ground Gr through 58 over the line of F returning through contacts 54-55 and the winding of 56 to battery. The operator throwing over levers 61 and 62 of the listening key learns the number of the desired-'subscriber, 289. Were this subscriber provided with a line jack within reach of the operator, shewould test the said jack by touching tip 63 of the calling plug to its sleeve contact, receiving, in case the line is busy, the usual click in her head. telephone from the resulting actuation of the test relay 75, in which case she would advise the callin subscriber that the line is busy. Did she car no click, she would complete the call in the usual manner. Assuming, however, that the called. line is not lprovided with a spring jack within reach of t e operator, she inserts the calling plug of the cord circuit into thespring jack terminal of connector H, among the bank contacts of which the line of subscriber G, numbered 289, is assumed to have multiple terminals. The operator, throwing over levers 25 and 26 of hercalling key,tirst operates the dial 18 to send eight impulses of current from ground G through contact 22-2], levers 26 and 28, contact 6566, arm 30, primary magnet 31 to battery. Magnet 31 is thereby caused to ell'ect upward movements of the shaft of the connector to bring wipers 82 and 33 level with rows of contacts including terminals or" Nos. 281 to 289 inclusive followed by 280. A single impulse of current now 'llowsfrom ground (Vt-hrough contact 2324, levers 25 and 27, contact 63-454, private magnet 36 to battery lead 52. Private magnet 36- by its energization and deonergization moves side switch arms 30, and

35 to engage contacts 37, 3S and 39 respectively.

The operator now actuates dial 1.8 to send nine impulses of current from ground G over the previously traced path to side switch arm 30, through contact 37, secondary magnet "4() to battery lead 52. The resulting energizetions of magnet 40 bring wipers 32 and 33 to engage multiple contact terminals of the desiredline. With the return of dial 18 to normal, a single impulse of current again flows from ground Gthrough the private magnet to battery; the said magnet, by its resultmg energization and denergization, moves side switch arms 30, 35 and 35 to engage their respective third contacts 43, 44 and 45, assuming the called line to be idle. The closing of contacts 3043 and 3544 connects the talking conductors of H, indicated by su ervisory relay to battery 52.

heavy lines, through to wipers 32 and 33 and to contacts 47 and 48 now engaged by said wipers. The called line being assumed idle, the operator receives no busy signal, and restores levers 25 and 26 of her calling key, whereupon current flows from ground Gr at the line clrcuit of subscriber G through cutoff relay {3, contacts 47-32, 43'30, 6665,-

through levers 28 and 26, the winding of Cut-off re ay 53 Is now energized and attracts its armatures to open the circuit of the line relay 50 and to connect limbs 1 and 2 of the line of subscriber G to contacts 48-and 47 res ectively and to the other'multiple termina s of the line. The before described flow of cur rent also eil'ects the energization of relay 70 which attracts its armature to engage the associated front contact, thereby closing circuit from ground G" through calling supervisory signal lamp 7]. to battery 52, effecting the display of the said signal. The energization of 70 also attracted its right hand armature to open the circuit of test relay and complete the conversational circuit of the tip strand of the cord circuit in the well known manner.

The operator now depresses levers 2728 of her ringing key, connecting generator 5] in circuit with the called line, current from said generator passing through the call bell at the substation and causing the bell to ring,

thus notifying the subscriber that his attention is desired. While the bell of subscriber G is being rung, cutofl' relay 53 1s contmued G, passing through ringing key lever 28 and its alternate contact to battery lead 52". The operator restores levers 27 and 28 and when the called subscriber G responds, by removing his receiver, a path for the flow of current is established from ground G" through tip supervisory relay 72, the right hand armature of relay 70, through levers 25 and 27, contacts 6364, 35-44, 33-48, its alternate contact and armature 53 over limb 1, through the transmitter and hook lover at the substation, returning ovcr limb 2 through armature 53" and its alternate contact, through contacts 47-32, 43-3U, 6665, levers 28 and 26 and the winding of relay 70 to battery 52. This flow causes the encrgization of relay 72 which, by attracting its armature opens the circuit through lamp 71, which is thereby put out, thus notifying the operator that the called subscriber has responded. The above traced flow of current energizes the transmitter of subscriber G and conversation now proceeds over a path traced from substation 1 throughout the exchange by the heavily marked conductors to cluded in the two strands of the talking circuit at the exchange in the well known manner.

When at the end of conversation the subscriber at F replaces his receiver, he opens the path for the l low of current through relay 58 before traced, which relay is deonergizcd, and as a result its armature engages its back contact to complete a path for current to cause the display of supervisory signal 57. When the subscriber at G replaces his receiver, he opens the before traced path for the flow of current through relay 72, which is Bot amps being thus lighted the o orator knows that conversation is finlshe She thereu on withdraws the answering plug from t 0 spring jack of the linc of the subscriber F and the calling plug from the spring jack of circuit H. The first-withdrawal opens the circuit through rclays 06 and 53, whosearmatures resume their normal posi tions, whereby lamp 57 is extinguished and line relay 50 placed in circuit with the calling line.

It will be observed that mechanically connected to the tip contact (34. of the spring jack of circuit 1] is an auxiliary contact (37 adapted, when tip 63 of the calling plug ongages spring 64-, to close contact (i7-(i7", whereby circuit is completed from ground Gr through said contact and'through the windings of relays 69 and 68 in series to batsubstation G, condensers 73 and74 being in- 9 energized by a flow of current from ground deenergized, its armature retracted, and a 69 are immediately energized and remain so during the subsequent switching operations and during conversatlon. Of these two relays 68 1s constructed in suchmanner as to be relatively sluggish in the release of its arma-- ture as compared with relay 69, the arrangement of the two being such that when they are simultaneously deenergized upon the withdrawal of the plug from the spring jack of H and the resulting opening of contact 67 67? the armature of 69 will be retracted to close its normal contact before the armature of 68 disehgages its associated front contact. To render 68-relat1vely sluggish as to the release of its armature, a copper shell may be placed about its core or it may be rendered sluggish in any other other known or approved manner. Thus, when the operator removes the'calling plug from the jack of circuit H, contact 6767 .is opened and circuit through 68 and 69 is opened. The

quickly acting armature of 69 closescircuit from ground G 'through release relay 41, the armature of 69, the armature of 68 to battery lead 52*. 41 attracts its armature to energize release magnet 42 and the connector is released and returns to normal. When the sluggishly acting armature 68 disengages' its front contact, circuit will be broken through 41 and, upon the retraction of the armature of 41, release magnet 42 is deenergized and the connector switch is in its normal condition.

It will be observed that when a plug is inserted into the spring jack of any line, a connection exists'to the sleeve of the spring jack from the active 'side of battery 52, and contact 47 in the connectorb anks being in multiple with the sleeve of the line jacks, said battery connection extends to said contact 47 audits multiples. Similarly, when wiper 32 is brought to rest in engagement with a 001 1": tact 47 of an idle called line, abattery connec- 45 tion to the contact '47 and its multiples, and to the sleeve contacts of the multiple spring jack of the line, is completed from the active side of battery 52. In either of these cases,

the potential of the spring jack sleeves is raised so that an operator, testing a spring jack with the calling plug, will always receive a click. in herreceiver.

The battery connection above mentioned to contacts 47 of busy lines is employed in securing the automatic release of con nectors whose wipers 32 are brought to rest in engagement with contacts 47 of busy lines in the following manner. Assuming the line of G to be busy when 32 engages 47, the energization of relay 36 occurring with the return of dial 18 to normal, as before described, attracts the armature of 36 to engage its as- ..sociated front contact. At this time, 35

will be in engagement 39, it being re,- mcmbered that the side-switcharms are acconnectiom provide a busy test tuated only upon the deenergization of 36. Current thus flows from ground G through release relay41 through armature of 36 to its front contact, through contact 35-39, wiper 32 to bank contact 47 and to battery through a multiple of the said bank contact. This flow energizes the release relay 41, which, in turn, energizes release magnet 42, upon whose energization the connector is re leased and returns to normal. With the return thereof, contact 8081, which was opened with the first upward step of the shaft, is again closed and the operator receives a busy signal from busy machine 46,

through contact -81, the normal contact of side-switch arm 30, plug and jack contact 66-65, lever28, lever 26, its alternate contact, through contact between springs 19 and 20 (dial 18 being at this time at normal) and through the tertiary winding of the operatorts induction coil to battery. The operator, being thus notified that the line Wanted is busy, withdraws the calling plug from the jack of the connector used, and, advising the subscriber of the'circumstances, withdraws the answering plug from the spring jack of the line.

While in the foregoing I have described each operator as being provided with jack terminals of connector switches individual to her position, I contemplate, in the employ ment of my invention, a structure wherein .the spring jack terminals ofconnector switches maybe multipled before two or more 0 erators, each of whom would be'thus enable to use them in completing a desired In doin this, it is preferable to ?or the spring jack terminals of the connectors, and m Fig. 9 I have indicated onewa in'which the test means may beprovided or spring jacks of c-onnectors such as that shown at H in Fig. 8.

The additional 1 means provided in 9 consistmerely 'in'the provision of a second sleeve contact 66 for each multi le terminal of a connector switch, the said additional sleeve contacts bein connected together. In employing this mu tiple arrangement the circuit connections of the connector will be identical with those shown at H and the same cord circuit as that shown in Fig. 8 will be employed.

Assumin that the operator desires to "test,

by means 0 the cord circuit shown at Fig. 8, one of the multiple jacks shown at Fig. 9, she touches the ti '63 of the calling plug. to sleeve 66 of t e jack to'be tested. If the jack testedfs idle, 66 will be in open circuit, and no energization of the test relay 75 1n the cord circuit will result and the operator will receive no click in her telephone. She will thereupon insert the plug into the spring jadkfltzp 63 of the-plug engaging conta'ct 64 ofthe jack and sleeve 65 of the plug crossing . contacts 66 and 66 of thesprmg jack. It

- tiple terminals for said other lines, selective exchange, selective switches adapted for opnals, operators switching means for control- 'der them busy when connection is made with will be seen from an inspection of Fig. 8 that sleeve is at all times connected to the active side of batterv 52 with the exception of the time when calling device 18 is being 0 erated. Sleeve contacts 66 of the multip e connector spring jacks, will, when the Oil-H111 plug of a cord circuit is inserted in one 0 them, be connected to the active side of 52. A second operator touching the sleeve contact 66 of a multiple jack in which 'a plug is inserted will cause a flow of current "from ground G through test relay 75 to tip 63 of the plug with which she is making a test, thence to contact 66" of the plug tested and through a multiple thereof to the active side of battery 52. Test relay 75 will therefore be actuated and attracting its armature will close circuit through the tertiary winding of the operator's induction. coil, notifying her that the connector in circuit with the multiple jack tested is already employed by an operator at another position.

I do not limit myself to the specific arrangement of apparatus and circuits shown herein or to the employments specifically mentioned ofmy invention, as the princi le is applicable broadly in the art, and 1 shal so claim it.

I claim: I

1. A telephone system comprising subscribers telephone lines extending from substations to an exchange, signals for said lines controlled from the substations, operators answering means adapted for connection with said lines, other telephone lines, mulswitches ada ted to be employed for making connection therewith, operators switching means to enable the operators to transmit directive currents to said selective switches to cause them to connect said answering means with terminals of particular ones of said other telephone lines whereby-connec-- tions between subscribers are completed, and a central source of current and branches to supply current therefrom for conversation,

2. A telephone exchange system including tele hone lines having answering terminals ire exchange, signals at the exchange adapted to be controlled by currents over said lines, operators connective-means adapted to be connected with said answering terminals, multiple terminals of said lines at the eration to complete connections from said answering terminals to said multiple termiling the operation of said switches to select terminals of particular lines, means for changing the electrical character of its terminals to rena line; automatic test means'for said switches sensitive to the electrical character of said terminals to render connections ineiiective when said terminals are busy, a central source of current and branches to energize subscribers transmitters therefrom for conversation, and means for releasing said select ive switches when disconnection is required.

3. A multiple switchboard telephone exchange system including telephone lines, signals for said lines at the exchange, answering jacks for said lines, operators cord circuits provided with plugs for connecting with said spring jacks, multiple calling terminals of said-lines divided into groups, a plurality of connector switches adapted to make connections with the lines of each of said groups, means controlled by the-operators for completing connections from said cord circuits to said connector switches, calling devices controlled by the operators for transmitting directive switchin currents to said switches to cause them to se ect particular called lines of their groups, means for changing the electrical character of its terminals to render them busy when connection is made with a line, test means for said switches whereby a connection made with a busy line is ineffective, and a central source of current and apparatus for supplying current therefrom to subscribers lines for conversation.

4. A multiple switchboard telephone exchange system including telephone lines, signals for said lines at the exchange, answering spring jacks for said lines, operators cord circuits provided with plugs for connecting with said sprin' jacks, multiple calling ts minals of said iines divided into groups, a plurality of connector switches adapted to make connections with the lines of each of said groups, manually manipulated operators switches for connecting said cord circuits with said switches, calling devices controlled by the operators for transmitting directive switching currents to said switches to cause them to select particular called lines of their groups, means for chan 'ng the electrical character of its terminas to render them busy when connection is made, with a line, test means for said switches whereby a connection made with a busy line is ineffective, and a central source of current and apparatus for supplying current therefrom to subscribers lines for conversation.

5. A multiple switchboard telephone exchan e system including-subscribers lines,

signa s for said lines adapted for operation from the substations, answering spring jacks for said lines, multiple calling terminals of said lines divided into groups, a plurality of connector switches adapted to make con. nection with the lines of each of said grou s, link-circuits extending to said switches or controlling their operation, spring jack terminals of said circuits, 0 erators cord 'circults hav ng answering p ugs for connecting with said answering spring jacks and calling Iplugs for connecting with said s ring jack terminals, calling devices control ed by the operators for transmitting directive switching currents to said switches to cause them to select particular lines of their groups, automatic test means for said connector switches to cause them to avoid busy lines, and a cen tral source of current and branches therefrom to sup ly current for conversation.

6. A mu tiple switchboard telephone exchan e system including subscribers lines, signa s for said lines adapted for operation from the substations, answering spring jacks for said lines, multiple, calling terminals of said lines divided into groups, a plurality of connector switches adapted to make connection with the lines of each of said groups, link-circuits extending to said switches multiple spring jack terminals of said circuits, means enabling the'operators to determine the idle or busy condition of said spring jack terminals, 0 erators cord circuits havin answering p ugs for connecting with said answering spring jacks and calling plugs for connecting with said spring jack terminals,-

calling devices controlled by the operators for transmitting directive switching currents to said switches to cause them to select particular lines of their groups, automatic test means for said connector switches to cause cord circuits provided with them to avoid busy lines, and a central source of current and branches therefrom to supply current for conversation.

7. A multiple switchboard telephone exchange system including telephone lines, signals for said lines at the, exchange, answering spring jacks for said lines, operators lugs for connecting with said spring jac s, other telehone lines, multiple terminals of said other i'nes divided into groups, a plurality of connector switches adapted to make connections with the lines of each of said groups, manu-' ally manipulated operators switches for connecting said cord circuits with sa'id'connector switch-es, calling devices controlled by the operators for transmitting directive switch ing currents to said switches to cause them to select particular lines of their groups, and a central source of current and apparatus for supplying current therefrom to subscribers lines forconversation;

8. A multiple switchboard telephone exchange system including telephone lines, signals tor said lines at the exchange, answering spring jacks for said lines, operators cord circuits provided with plu s for connecting with said spring jacks, ot or telephone lines, multipleterminals of said otherlines divided into groups, a plurality of connector switches adapted to make connections with the lines'of'each of said groups, manually manipulated operators switches for connecting said cord circuits with said connector switches, calling devices controlled by the operators for. transmittin directive switching currents torsa'id swit'c es to cause them to select particular lines of their groups, means for changing the electrical character of its terminals to render them busy when connection is made with a line, testmeans for said switches whereby a connection made with a busy line is ineffective, and a central source of current and apparatus for supplying current therefrom to subscribers hnes for conversation.

9. In a telephone system, a plurality of trunk jacks,a trunk line connected thereto,

an automatic switch connected to said trunk" able terminals for connecting with said 'calling terminals, and a slow acting release relay and a quick-acting release relay associated wit-h said electromagnetic-ally mov able terminals adapted at the will of the operator to cooperatively cause the restoration of said terminals.

11. A telephone system comprising sub-- scribers telephone lines extending from substations to an exchange, signals for said lines controlled from the substations, operators answering means adapted for connection with said lines, other tcle ihone lines, multiple terminals for said ot er lines, selective switches adapted to be employed for making connection therewith, operators switching means to enable the operators totransmit directive currents to said selective switches to cause them to connect said answering means with terminals of particular ones of ,said other telephone lines whereby connections between subscribers are completed, a spring jack switch and a plug therefor adapted to connect said switching means with a selective switch, and apparatus operable, whensaid plug is removed from said spring ack switch, to cause the restoration of an operated selective switch.

12'. A telephone system comprising sub- I scribers telephone lines extending from substations to an exchange, signals for said lines controlled from the substations, operators answering means adapted for connection with said lines, other telephone lines, multiple terminals for said other lines, selective switches adapted to be employed for mak ing connection therewith, operators switching means to enable the operators to transmitdlrectlve currents to said. selective switches to cause them to connect said anconnections between subscribers are completed, automatic test means for said switches adapted to automatically cause their disconnection from busy lines. when brought to engage terminals thereof, aspring jack switch and a plug therefor adapted to connect said switching means. with a selective switch, and

apparatus operable, when said plug is removed from said spring jack switch, to cause the restoration of an operated selective switch.

13. A multiple switchboard telephone exchange system including telephone lines, signals for said lines at the exchange, answering terminals for said lines, operators link-circuits for connecting with said ,answering terminals, other telephone lines, multiple calling terminals for said lines, selective switches for connecting with said last mentioned terminals, linkcircuits connected. with said selective switches, manually operated terminals for said l nk-circuits adapted for connection with said operators link-circuits, and a paratus operated on dis connection of sai operators link-circuits from said. manually operated terminals for restoring said selectiveswitches.

14. A multiple switchboard telephone exchange system including telephone lines, signals for said lines at the exchange, answering terminals for said lines, operators link-circuits for connecting with said answering terminals, other telephone lines, multiple calling terminals for said lines, selective switches for connecting with said last mentioned terminals, li nkcircuits connected with said selective switches, manually operated terminals for said link-circuits adapted for connection with -said operators link-circuits, means for causing the operation of said selective switches to connect with said other telephone lines, apparatus for changing the electrical character of said multiple terminals to render them busy when said switches are connected with said other lines, test means for saidselec ive switches whereby they automaticallydisengage said multiple terminals when busy, and apparatus operated on disconnection of said operators linkcircuits. from said manually operated terminals for restoring said selective switches.

15. A telephone exchange system including telephone lines having answering terminals at theexchange, signals at the exchange adapted to be controlled by currents over said lines, operators connective means adapted-to be connected with said answering terminals, multiple terminals of said lines at the exchange, selective switches adapted for operat on to complete connections from said answering terminals to said multiple terminals, operators switching means for controlling the operation of said switches to select switcbing means adapted, when a p terminals of particular lines, and plugand jack connections included in said 0 )erators lug is removed from a jack, to cause the restoration of a connected selective switch.

16. A telephone system including acalling line, an operator's link-circuit connected therewith, other telephone lines, multiple terminals for said other lines, selective switches adapted to be employed for making connection therewith, operators switching means to enable the operators to transmit directive currents to said selective switches to cause them to connect said answering means with terminals of particular ones of said other telephone lines whereby connections between subscribers are completed, and. a central source of current and branches to supply current therefrom for conversation.

17. .A tele )hone exchange including a substation, a te ephone line connecting said station with the exchange, signals at the exchange, a hook-switch at the substation adapted, on removal of the receiver, to cause the display of a signal, operators means for answering the call, other telephone lines, multiple terminals for said other lines, selective switches adapted to be employed for making connection therewith, and operators switching means to enable the operators to transmit directive currents to said selective switches to cause them to connect said answering means with terminals of particular ones of said other telephone hncs whereby connections between subscribers are completed.

18. A tele hone exchange including a substation, a te ephone line connecting said station with the exchange, signals at the exchange, a hook-switch at the substation adapted, on removal of the receiver, to cause the display of a si nal, operators means for answering the cal, other telephone lines, multiple terminals -for said other lines, selective switches adapted to be employed for making connection therewith, operators switching means to enable, the operators to transmit directive currents to said selective switches to cause them to connect said answering means with terminals of particular ones of said other telephone lines whereby connections between subscribers are completcd, a central source or" current and branches to supply current therefrom for conversation.

19. A telephone exchange including a substation, a telephone line connecting saidstation with the exchange, signals at the exchange, a hook-switch .at the substation adapted, on removal of the receiver, to cause the display of a signal, operators means for answering the call, other telephone lines, calling terminals for said other telephone lines and operators connecting means including electromagnctically movable tcrnnnals for eomlpleting eonnections through said other te I v i 20. A telelphone exchange including a subi-fi'l' ephone lines.

station, a te ephone line connecting said station with the exchange, signals at "the egi-l change, a hook-switch at the substation I 7 In adapted, on removal of the-receiver, to cause the dlsplay of a signal, operators. means for answer-mg the call, other teiephone lines,

calling terminals for said other telephone lines and operators connecting means'inelectromagneti cally movable termi- *ynalsifor com leting connections through to T. H. FERGUSON, L. D. KELLooe.

Images