US1556793A

US1556793A - Automatic telephone system

Info

Publication number: US1556793A
Application number: US393963A
Authority: US
Inventors: Fred T Madsen
Original assignee: Automatic Electric Co
Current assignee: Automatic Electric Co
Priority date: 1920-07-03
Filing date: 1920-07-03
Publication date: 1925-10-13
Anticipated expiration: 1942-10-13

Description

0a. 13, 1 92s. F. 1'. MADSEN AUTOIA'IIG 'rmraona sisal Original Filed July 5, 1920 3 Shuts-Shoat 1 m\\ l v k Elck-W IWQXGM F FF m \N .IL I 4m B N\.IULI m MYEH. 1+ II In Oct. 13, 1925.

F. T. MADSEN AUTOMATIC TELEPHONE SYSTEM I-UI IIIIIIII R M m IIIIIIIIII w. I III NR1 k :N m; m 0 N.\. Q s w T I 1 I I I I I I I I I I I Z. ing E To all whom it may concern:

Patented Oct. 13, 1925.

UNITED STATES PATENT, OFFICE. A

FRED '1'. MAIDSEN, OF GREEN BAY WISCONSIN, ASSIGNOR TO AUTOMATIC ELECTRIC COMPANY, OF CHICAGO, ILLINOIS, A CORPORATION OF ILLINOIS.

AUTOMATIC TELEPHONE SYSTEM.

Application filed. July 3, 1920, Serial No. 898.983. Renewed March 16, 1925.

Be it known that I, FRED T. Miapsnn, a citizen of the United States'of America) and a resident of Green Bay, Brown County,

and State of Wisconsin, liaveinvented certain'new and useful Improvements in Automatic Telephone Systems, of which the following is a-specification,

My invention relates in general to automatic telephone systems, but more especially to such systems as comprise main and branch exchanges, and the object of the invention may be stated ,to be, in broad terms, the provision of a new and iinproved two way trunk circuit for use in connecting an automatic main exchange with an automatic branch exchange.

A special object is the provision of a trunk circuit of the above character, which has a multiple terminal or jack at a toll operators. position in the main exchange, together with means whereby the servlces of an operator may be enlisted for the purpose of establishing connections in either direction over the trunk line. In this connection it should be stated that means is provided whereby the use of the operators servicescan be made obligatory on the part of the subscribers whenever desired by the management while at other times the sub scribers can call freely over the trunk line.

A further object is the provision of means whereby a branch subscriber can signal the toll operator over a trunk line of the above character with a view to obtaining connection with a certain special line in the branch exchange to which the branch subscribers do not have free access. On receipt of a call of this kind the answering toll operator is able to call back over the trunk line in use and establish the connection locally.

To accomplish the foregoing and other objects I have devised special circuit arrangements which will be fully described hereinafter, reference being had to the accompanying drawings.

In the drawings, comprising Figs. 1, 2 and 3, Figs. 1 and 2 show by means of the usual circuit diagrams a complete trunk circuit embodying the principles of my invention, while Fig. 3 is a general trunking layout of the system.

The reference characters 50 and 51 indicate the two line conductors of the trunk circuit ,which terminate at opposite ends in the wmdingsof repeating coils R and R. Through the medium of repeating coil R the trunk conductors 50 and 51 are inductively connected with; the repeater D, which 1s located in a branch exchange, while repeating coil R serves to inductively connect the trunk conductors at the other end with the repeater E at the-main exchange. At the latter point the trunk circuit continues through the repeater to the jack J at a toll operators position. The auxiliary jack J and lamp signals L, L, and L are associated with ack J. 3

Connections to and from the trunk circuit ma be established as follows: The automat c switches, both at the main exchange and at the branch exchange, are of the modern two wire type such as are in common use in many exchanges throughout the country. The branch exchange, although it may be of any convenient size, will be assumed to be what is known as a hundred line system, that is, no selector switches are used and local connections are established by means of connector switches such as H, Fig. 3, which are accessible to the subscribers individual line switches such as C and C, In. order that the branch subscribers may also have access to the main exchange trunk lines the connectors H are preferably of the type known as selector connectors; in other words, they have an automatic trunk selecting movement on a certain level and perform the functions of a selector switch on that level. This trunk selecting level, usually the tenth, is the level in which the main exchange trunk lines are terminated. Thus in Fig. 1, the conductors 5, 6, and 7, extend from the repeater D to bank contacts 2, 3, and 4, respectively, which are multipled in the tenth level of the selector connectors in the branch exchange. Although many suitable selector connector circuits are well known, reference is made to the U. S. patent to Martin, #1,288,098, Dec. 17, 1918, which'shows a circuit which may be used.

Having explained how access is had to the main exchange trunk lines at the branch exchange, the means for extending these trunk lines to called lines in the branch exchange will now be considered. For this purposeeach.. ;trunk line is provided with a branch which extends from the repeater to a simple form of toll connector such as the connector H, Fig. 3. Thus the trunk line shown in the circuit drawing, Figs. 1 and 2, has a

branch comprising conductors

8, 9, and 10, which extend from the repeater D to one of these toll connectors. Althou h in general the toll connector used may e of any well known type, it has preferably two characteristics required to enable it to function properly in connection with the trunk circults shown. It is operated over a conductor separate from the talking conductors and when a connection to a called line is completed the incoming line conductors are connected straight through the connector to the called line without inductive connections or bridges of any kind in the connector.

Connectors having these features are well known as is shown in the U. S. patent to Wicks, #315,444, Sept, 9, 1919. The @011 connectors H of course have access to the local lines in the branch exchange the same as do the selector connectors H, and the tenth level, which is reserved for the main exchange trunk lines in the selector connectors, may be used in the toll connectors to terminate a group of special lines such 'as the line of station A as will be explained more fully hereinafter.

The switches associated with the trunk line at the main exchange correspond in general to those at the branch but are of more simple form due to the fact that the main exchan e is of large capacity and the trunk lines i rom the branch exchange are accessible to and terminate in selector switches rather than .connector switches. In Fig. 2 the

conductors

55, 56, and 57 extend from the repeater E to sets of multiple bank contacts in the banks of second or third selectors such as the selector F, Fig. 3, one of which sets is indicated by

reference characters

52, 53, and 54. This constitutes the means whereby the main exchange subscribers are given access to the trunk line. Connections from the trunk line are extended by way of the branch comprising conductors 58, 59, and 60, which extend to and terminate in the first selector F, Fig. 3, which is shown in skeleton form just below the repeater E, Fig. 2. This first. selector is the same as the other selectors except that it has a cutoff relay 101 connected as shown.

. The cord circuits such as the cord circuit 0 at the toll operators position are of the ordinary type using ring down supervision on the outgoing endand having arrangements for transmitting operating impulses over the sleeve conductor. A cord circuit of this kind is shown in the previously mentioned patent to Wicks.

Having described my improved trunk circuit in a general way, I will now explain more in detail how the same is used to set up connections. It will be assumed in the first place that the toll operator desired to conthe insertion of the plug in the jack, relay.

68 is energized over the sleeve of the cord and upon attracting its armature 89 closes a circuit for the slow acting relay 67.

Upon energizing, relay 67 connects ground to the conductor 56 by means of its armature 86, thereby placing a busy potential upon the test contact 53 and its multiples in the banks of the selector switches having access to the trunk line, and also lighting the busy lamp L at the operators position. It is understood that the jacks-and lamps shown may be multipled in other operators positions and the multiple busy lamps will of course be lighted in parallel with lamp L Conductor 56 being grounded, a circuit may be traced by way of armature 72 and its resting contact, conductor 59, and the winding of the cut off relay 101 to battery. Relay 101 is accordingly energized to disconnect the branch conductors 58 and 60 from the first selector switch. Relays 67 and 68 being in operated position, an operating or control circuit extending to the branch exchange may now be traced as follows: from the ungrounded pole of the exchange battery by way of resistance 92, working contact of armature 91 and the said armature, armature 88 and its working contact, conductor 93, left hand windings of the repeating coil R in parallel, conductors 50 and 51 in parallel, right hand windings of repeating coil R in parallel, conductor 36, armature 30 and its restingcontact, and the winding of relay 15 to ground. Upon the closure of the above circuit, relay 15 is energized and at its upper armature closes a circuit for the slow acting. relay 14. Upon energizing, relay 14; connects ground to the conductor 6 by means of its armature 24, thereby placing a busy potential upon the test contact 3 and its multiples in the banks of the selector connectors in the branch exchange. In addition to closing a circuit for relay 14:, relay 15 closes at its armature 27 an operating or control circuit which extends from the negative pole of the battery by way of resistance 37, the working contact of armature 27 and the said armature, and conductor 9 to the line relay of the toll connector H in which the branch trunk

line comprising conductors

8, 9 and 10 termi-- toll connector are accordingly energized and the switch is prepared for operation in the usual manner.

The toll operator may now operate her calling device in accordance with the digits in the local number of the" desired line at the branch exchange. When the calling device is operated in accordance with. the first cuit of the line relay of the toll connector.

It follows that the toll connector is operated in the usual manner under control of the line. relay to select the group in which the desired line is located. When the operator calls the second digit in the number the interruptions produced are repeated inthe same manner by means of relays 68 and 15,

and the toll connector is operated to estab lish connection with the particular line wanted. Automatic ringing equipment is now brought into use to ring the bell at the station on the called line. When the subscriber answers, the rin 'ng apparatus is I disconnected and the talking circuit is completed as usual, the transmitter at the called substation being supplied with talking battery through the windings of the double wound relay 19 at the repeater D. This will be readily understood when it is recalled that the toll connector H, is of the type which connects the line conductors straight through to the called line, as previously explained; and since relay 19 is connected across the trunk in series with the battery it Will supply current to the called line as stated. Upon energizing, relay 19 closes a circuit which extends from its grounded armature 35 by way of the working contact I of said armature, armature 25 and its working contact, and the windings of relays 13- and 12 in series to battery. Relays 12 and 13 are accordingly energized but without effeet at the present time.

The connection to the desired line at the branch exchange has now been established, and if the connection is completed at the toll board by means of the other end of the cord circuit in use, conversation can be held over the talking circuit thus established. When the subscribers are through talking they will replace their receivers, whereupon disconnect supervision is'given to the toll operator. The manner in which the branch exchange subscriber gives'the toll operator a disconnect signal will now be explained.

When the receiver is replaced relay 19 at falls back at once but relay 13, being slow acting, retainsits armatures for an instant, and durin winding 0 the transformer R is bridged across the conductors 50 and 51 of the trunk line. Ringing current from the generator Gen. is thus transmitted over the trunk line and operates the ring down supervisory slgnal 1n the operators cord circuit. This g ves the operator the usual disconnect supervision, and upon perceiving the signal she will pull down the connection. When the plug is removed from the jack J relay 68 is deenergized and breaks the circuit of relay 67 and also the control circuit extending to the branch exchange. At the latter point relays 15 and 14 thereupon dccnergize and the former breaks the control circuit extending to the toll connector H. It follows that the toll connector will be restored to normal inthe usual manner and since all the relays have deenergized the trunk circuit will be ready for use in establishing another connection.

It will now be assumed that a subscriber 1n the main exchange desires to obtain connection with a subscriber in the branch exchange. As before stated, the trunk lines connecting the main and branch exchanges terminate at the main exchange in the banks of second or third selectors such as the selector F, Flg; 3, and the calling main exchange subscriber therefore can obtain access to an idle one of these trunk lines by calling the digits which correspond to the particular selector groups and levels which happen to be used for this purpose. Assuming that the trunk line shown in the drawng is selected, when the selector switch hav ing access to

bank contacts

52, 53, and 54 establishes connection therewith and cuts through, the calling. subscribers line will be extended by way of bank contacts 52 and 54. right hand windings of the repeating coil R, and armatures 71 and 7 3 and their resting contacts to the upper and lower windings of the double wound line relay ,66 of the repeater E. Relay 66 is accordingly energized over the line circuit and upon attracting its armature 84 completes a circuit for the slow acting relay 65. Upon energizing relay 65 connects ground to the conductor 56 by means of its armature 81, thereby lighting the busy lamp L and its multiples, placing a ground potential upon test contact 53 and its multiples, and energizing the cut off relay 101. Relay 65 also closes a circuit for the main exchange call signal lamp L by means of its armature 82 and at its armature 83 closes the operating circuitwhich extends over the previously traced simplex circuit to the relay 15 in the repeater D at the branch exchange. This circuit is the same as the one previously traced except that it includes armatures 85 and 83 this interval the secondary of relays 66 and 65'instead of

armatures

91 and 88 of relays 68 and 67, and its closurehas. een received from a main exchange subscriber WhO dGSIIGS tO connect with a branchexch'ange -subscrlber and shewill accordin ly plug into-the jack J inorder to assist '1n plug is insertedin the jack relays 68 and 67 areenergized andthe latter relay breaksithe "circuitof the lamp L at, its armatures 87...;- Relay 67.als o groundsthe conductor 56 at,

a, new point-bymeans of its armature 86. and bymeans of its armature 88 places the operating. circuit'under control of the relay 6 8-. The toll operator can now operate her callingdevice and control the toll connecto'rfI-It at the branch exchange to establish. the desired connection, the operating impulses produced by the operationof the calling device being repeated by relays 68 and 15"iniwthe manner already described. When the connection has been established the toll operatormay withdraw the plug from the jack if she so desires, and need pay no further attention to the connection, which is controlled after the plug is withdrawn the calling *subscriber through the medium,

of relays 66 and 65.-- When conversation. finished both subscribers hang up their re-' 'ceiversfirelays 66 and are deenergized, and the '.-.operati'ng..circuit' is broken, where- -uponrelays 15 and 1e at the repeater D are I deenergized and the) toll connector is released? HaVing described the manner in which connections are extended from the main ex-' change to the branch, exchange over the trunk: circuit, I'will.now explain how the, same is used 1n extendlng connectlons 1n the oppositedirection. 'It will be assumed first, that a calling subscriber in the branch exchange desires to obtain connection with one of the special lines-hereinbefore mentioned. Since these lines appear in the banks of the toll connectors 'H' but do not appear in the banks of the selector connectors H they are not accessible to the local subscribers in the branch exchange as are the ordinary sub-' scribers lines, but when abranch exchange subscriber desires to connect with one of I ,these'special lines it will be necessary for lflm to call the toll operator at the main ex-Q ange. This being the case, the calling sub s. iber, after removing his receiver and ob'-- b branch-trunk conductors 5 and to the upper and lower. windings the setting-up of the connection. When-the" 'ing relay I :1-

to the trunk line for supervisory cuit, relay 62 in the repeater E ,and closes a circuit for the slow acting relay change. -Assuming that the trunk line shown is the first one found to be idle, the wipers will come to rest in enga ement with bank contacts 2, 3, and 4, orsimi calling, line. will be extended way of v v and the left handiwindings of the repeating coil R ture 35 comp etes' a circuit for the slow act- Upon energizing, relay 17 prepares a circuit" for relay 18 at its armature 31, and at its armature 29 connects ground to conductorv 6, thereby closing a holdingcircuit for the selector connector in use, and the calling subscribers line switch.

device in acof the line -relay19 of the repeater D. Upon the exar contacts, connected in multiple therewith, and the This holding circuit serves to retain the above switches in operated position throughout the connection. A branch of the holding circuit extends 'from'conductor 6 by way of armature 9A: and its resting contact and through the windings ofrelays 13 and 12 to battery. These relays are therefore energized jin'readiness to connect the generator urposes, as before explained. Relays 19 an 17 being. in operatedposition, a control circuit extending to the main exchange may be traced" as follows: from the ungrounded pole of the branch exchange battery by way of the winding of relay l6, contact'springs controlled by armature 33, working contact of armature 34 and the said ing contact of armature 30 and the. said armature, work-.

armature, conductor 36, right hand wind- 6151 The latter relay, upon energizing, connects ground" to the conductor 56 by means, of its armature 7 2,.thereby lamp L and itsinultiples, and placing a busy potential upon the test its multiples,

contact 53 and lighting the busy prepares a; circuit for relay at its armature 70, and at its armat'ures' 71'. and 73 disconnects the trunk conductors that acall has been received from a branch exchange subscriber. When the operator plugs into the jack J to answer the call, relay 68 is energized, and now,-since relay 61 is in operated position, the said relay 68 closes a circuit for the relay 64 at its armature 89. Upon energizing, relay 64 breaks the circuit of the call signal lamp L at its armature 78, connects ground to conductor 56' at the working contact of the same armature, connects theungrounded pole of the exchange battery --to the lower terminal of the winding of relay 62 by means of armature 80, and by means of armature 79 disconnects the operating circuit from the winding of the said relay 62, and extends it to ground at the working contact of the grounded armature 90 of relay 68. We now have relays 61, 62, 64, and 68, in therepeater E in energized position. At the repeater D in the branch exchange, relay 16 was energized when the control circuit was first established by the energization of relays 19 and 17, and this relay 16 completes the op-' erating circuit for the toll connector at its armature 28. p

The operator will now converse with the calling subscriber in order to ascertain what line he is calling. Finding that one of the special lines in the branch exchange is wanted, the operator will now actuate her calling device in accordance with the digits in the number of the special line, and the interruptions produced are repeated by means of relays 68 and 16 in order to control the toll connector to establish the desired connection. It is noted that relay 68 breaks the simplex operating"'circuit each time it deenergi aes at its armature 90, from which it will be seen that the operating circuit is somewhat different from the operating circuit used in former cases, the battery now used being the one located at the branch exchange. The desired connection having been completed by the toll connector the calling and called lines will be connected over a direct path in the branch exchange, and both subscribers will be supplied with talking battery through the windings of the double wound line relay 19 of the repeater D. When the subscribers hang up their receivers at the end of the conversation relays 19, 17 and 16 at the repeater D will deenergize, andthe latter relay breaks th control circuit extending to the toll connector which is thereupon restored to normal. Relay 17, upon deenergizing, breaks the circuit of relays 12 and 13, and when'relay 12 deenergizes, ringing current is automatically transmitted over the trunk line in order to operate the ring down relay in the operators cord circuit to givethe toll operator a disconnect signal. When the operator perceives the signal, she will withdraw the plug from jack J and relays 68, 64, 62, and 61 will fall back, whereupon all the relays will have been deenergized and the trunk circuit will be ready for use in another connection.

It will now be assumed that a calling subscriber' in the branch exchange desires to obtain connection with a subscribers line in the main exchange. In order to establish the connection the callin branch exchange subscriber will call the igit O in order to obtain access to one of the main exchange trunk lines, the same as was done in the case just described. Assuming that the trunk line shown in the drawings is taken for use, when the connection is extended to bank contacts 2, 3, and 4, relays 19 and 17, and 12 and 13 in the repeater D are energized as previously explained, and the operating circuit including relay 16 in the repeater D, and relay 62 in the repeater E at the main exchange is closed. These two relays are accordingly energized also, and the latter relay brings about the energization of the slow acting relay 61, with the result among other things, that the branch exchange call si a1 lamp L is lighted at the operators posltion. Attention is nowv called to the fact that at the working contacts of the armatures 71 and 73, relay 61 has prepared a shunt circuit around the condenser which is included between the right hand windings of the repeating coil R, which shunt circuit, if closed, would constitute with the right windings of the repeating coil, a bridge across the branch trunk conductors 58 and 60 extending to the first selector switch F. Since relay 62 is energized, and its armature 74 is in operated position, this shunt circuit would be closed were it not for the fact that special terminals 94 and 95 are disconnected from each other, and it will be evident therefore, thatnothing further can be done without the assist ance of the operator.

When the operator plugs intothe jack J to answer the call, relays 68 and 64 are energized as in the previous case, and with the same results. Upon ascertaining that the calling branch subscriber desires to obtain connection with a subscriber in the main exchange the operator will proceed to set up the connection in the following manner:

Taking any idle cord circuit the operator vwill plug into the auxiliary jack J, thereby establishing a circuit for the slow acting relay 63. Upon energizing, relay 63 disconnests the upper terminal of relay 62 from direct ground at the resting contact of its 'with relay 63. As a'further result of this operation relay 63 closes the previously mentioned shunt around the condenser at its armature 77. The bridge across branch.

trunk conductors 58 and 60 is now completed and the line and release relays of the first selector F will energize to prepare the selector switch for operation.

The apparatus is now ready for the calling of the number of the desired main exchange subscriber. Thenumber is called on the cord circuit associated with the auxiliary jack J, and when the calling device is operated in accordance with the first digit a series of interruptions is roduced in the circuit over the sleeve of the cord which includes relays 63 and 62 in parallel. Relay 62 responds by deenergizing a plurality of times and at each 'deenergization opens the shunt around the condenser at its armature 74, thereby producing a series of interruptions in the circuit of the line relay of the selector switch. Responsive to these interruptions the selector is operated under control of its line relay to extend the connection to an idle second selector in the proper group. When the calling device is operated in accordance with the remaining digits in the number, the resulting series of interruptions are repeated by relays 62 in the same way and the selected second selector, selector F for example, Fig. 3, and a final connector switch such as H are 0 erated in the well known manner to comp etc the connection. The bell at the called station is now rung automatically and when the called subscriber responds, conversation may be held over the established con- I nection.

At the termination of the conversation both subscribers will replace their receivers, and as a result of the hanging up of the receiver by the branch exchange subscriber, relays 19, 17, 12, and 13 in the repeater D will be deenergized. The relay combination comprising relays 12 and 13 now connects ringing current to the, trunk line as in the former case, in order to give the toll operator a disconnect signal, and upon perceiving the signal the operator will withdraw both plugs from the jacks. All the relays in repeater E are accordingly deenergized with the result that the bridge across trunk conductors 58 and 60 is broken and the operated switches in the main exchange are released.

The various connections which are described in the foregoin paragraphs have all been established wit the assistance of the toll operator, and it will be evident from what has been'said that the assistance of the operator is absolutely required with the apparatus connected as shown. The circuits may readily be changed, however, to providely, and entirely without the assistance of the a toll operator, as will now be briefly pointed out. Assuming that a calling main exchange subscriber has established connection with the trunk .line at

bank contacts

52, 53, and 54, when the connection is completed relays 66 and 65 will be energized as before explained, and the operating or control circult including the relay 15 at the repeater D in the branch exchange will be completed. The calling subscriber may now operate his calling device in accordance with the digits in any desired number in the branch exchange, and since the

special terminals

96 and 97 are now disconnected, the resulting deenergizations of the line relay 66 will produce corresponding interruptions in the operating circuit. It follows that the toll connector at the branch exchange can be operated under control of the relay 15 at the repeater D to complete any desired connection.

Considering now a call from a subscriber in the branch exchange, if such subscriber desires to connect with a subscriber in the main exchange, the repeater E being connected for automatic calling as stated, when the calling subscriber .connects with the trunk line at bank contacts 2, 3, and 4, relays 19 and 17 are energized as previously explained to close an operating circuit which includes relay 16 of the repeater D, and relay 62 of the repeater E. These relays are accordingly energized, and the latter relay closes the circuit ofrelay 61. Re-

lays 62 and 61- being in operated position,

it will be evident now that the shunt circuit around the condenser connecting the righthand windings of the repeating coil R will be closed, for the special terminals 94 and 95 are connected together. The calling branch subscriber will not therefore have to wait until the operator comes in on the line to set up the connection, but may at once proceed to dial any desired number in the main exchange. The interruptions produced by the calling device are repeated by means of line relay 19 and relay 62, causing a like series of interruptions in the bridge across the branch trunk conductors 58 and 60, and it follows that the switches in the main exchange will be controlled as desired to connect with the wanted line. It will be to repeat impulses, it sends impulses the' slow acting rela 18 which is accordingly energized at the ginning of each series of impulses and remains in operated positlon until the'series is completed. In energized position relay 18 cuts the relay 16 out of the operating circuit and substitutes therefor the resistance 38. This is done 1n order to prevent the operation of the toll connector which would otherwise be operated in accordance with the first two digits in 1 the number of the main exchange. With the arrangement described the operating circuit of the toll connecter is broken long enough to release it each time a series of impulses is transmitted. Relay 18 also cuts out the upper winding of the line relay 19 during each series of impulses, and closes the circuit through the resistance 38. This produces a control circuit which is less susceptible to line leakage than a circuit having both windings of the line relay across the line. The release of the connection,

-when established in the foregoing manner,

ment of the receiver at the calling station which breaks the operating circuit and the release of the switches in use follows in the manner already explained.

When the repeater E is connected for antomatic calling th busy lamp L should be removed, and the lamps L and L are used as busy lamps. When the lamp L is lighted it indicates to the operator that the trunk line is in use in a main to branch exchange connection, and when the lamp L is lighted it will indicate to the operator that the trunk line is in use in a branch to main exchange connection. In case subscribers in either exchange desire to connect with the toll operator for any purpose, they may do so by calling her through the regular main exchange trunking system, which ordinarily includes a number of so called toll recording trunks over which the toll operators may be reached. 7

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

. What I claim as my invention is:

1. In a telephone system, a main exchange having an operators position, a branch exchange having a toll connector, a trunk line extending from said op 'rators position to said toll connector, se ector connectors in said branch exchange having access to said trunk line, special lines in said branch exchange accessible to said toll connector but inaccessible to said selector connectors, other telephone lines in said branch exchange, means controlled from one of said other telephone lines for operating one of said selector connectors to connect withsaid trunk line and call the operator thereover ,for the purpose of obtaining connection withone of said speciallines, and means whereby the operator at said position canoperate' said toll connector to establish a connection with one of said special lines locally.

2. In a telephone system, a main exchange having an operators position, a branch exchange, .a trunk line extendingfrom said operators position to said branch exchange, a branch of said trunk at the main exchange terminating in an automatic switch, means whereby a branch subscriber can connect with said trunk line for the purpose of obtaining connection with a subscribers line in the main exchange, means preventing such branch subscriber from operating said switch, means for signalling the operator when the call is received, an answering jack Where the operator can'plug in and answer the call, an auxiliary jack associated with said answering jack, and means for establishing a control circuit for said switch by way of said auxiliary jack whereby the operator can operate the said switch to extend the call in the direction of the desired line.

3. In a telephone system, a main exchange,

a branch exchange having a toll connector, a

trunk line extending from said main exchange to said toll connector, said connector being adapted for use to complete two classes ofconnections, a control circuit for said connector including the two sides of said trunk line in parallel, a battery in each exchange, means for closing said control circuit through the branch exchange battery when a connection of one kind is established, and means for closing said control circuit through the main exchange battery when a connection of another kind is established.

4. In a telephone system, a main exchange having an operators position, a branch ex.- change having an automatic switch, a trunk line extending from said operators position to said switch, a cord circuit at said position, telephone lines in said branch exchange,

means including said cord circuit whereby the operator at said posltion may operate receiver at the substation on the called line other automatic switches, means controlled from a telephone line in one of said groups for operating one of said other automatic switches to seize said trunk line, and means controlled from said pos tion for then extending the connection to a line in said other group by operating the first-mentioned autoswitch, other automatic switches in said branch exchange having access to said trunk line, two groups of telephone lines in said branch exchange, one of said groups being inaccessible and the other accessible to said other automatic switches, means controlled from a telephone line in vone of said groups for operating one of said other automatic switches to seize said t unk line, a signal at said operators position, means controlled by the seizure of said trunk line for operating said signal, and operator controlled means for then operating the first-mentioned switch over said trunk line to extend the connection to another of said telephone lines.

7. In a telephone system, a main exchange having an operators position, a branch exchange having an automatic switch, a trunk line extending from said position to said switch, other automatic switches in said branch exchange having access to said trunk line, two groups of telephone lines in said branch exchange, one 0 said groups being inaccessible and the other accessible to said other automatic switches, means controlled from a telephone line in one of said groups for operating one of said other automatic switches to seize said trunk line, a signal at said operators position, means controlled by the seizure of said trunk line for operating said signal, operator controlled means for operating the first-men tioned switch over said trunk line to extend the connection to another of said telephone lines, and a relay associated with said first automatic switch for supplying talking current to the connected lines in said branch exchange.

8. In a telephone system, a main exchange having an operators position, a branch exchange having an automatic switch, a trunk line extending from said position to said switch, other automatic switches in said branch exchange having accessto said trunk line, two groups of telephone lines in said branch exchange, one of said groups being inaccessible and the other accessible to said other automatic switches, means controlled 5 ating said signal, operator controlled means for operating the first-mentioned switch over said trunk line to extend the connection to another of said telephone lines, operator controlled means for releasing said swtich, and means operative as long as the subscriber on said calling line maintains his receiver ofi the switchhook for preventing said release. 1

9. In a telephone system, a main exline, a signal at said operators position,

means controlled by the seizure of said trunk line for operating said signal, operator controlled means for operating the first-mentioned switch over sa1d trunk line to extend the connection to another of said telephone lines, means controlled by the calling subscriber for releasing said first switch, and operator controlled means for preventing said release.

10. In a telephone system, a main exchange and a branch exchange, a trunk line interconnecting said exchanges, anautomatic switch associated with said trunk line at said branch exchange, telephone lines in said branch exchange, other automatic switches in said branch exchan e, means controlled fromione of said telep one lines branch exchange having an automatic switch, a trunk line extending from said position to said switch, a circuit for controlling said switch including two conductors of said trunk line in parallel, a battery in each exchange, means for closing said control circuit through one of said batteries to control the operation of said switch, and means for substituting said other battery in said control circuit.

12. In a telephone system, a main exchange having an operators position, a branch exchange having an automatic switch, a trunk line extending from said position to said switch, telephone lines in both exchanges, automatic switches controlled from one of said telephone lines in said main exchange for extending a connection to said trunk line, means controlled by the operator at said positioufor operating the first-mentioned switch over said trunk line to extend the connection to one of said telephone lines in said branch exchange, operator controlled means for releasing said first switch. and means controlled over said calling line for preventing the operation of said releasing means.

13. In a telephone system, a main exchange having an operators position, a branch exchange, telephone lines in said branch exchange, a trunk line interconnecting said exchanges and terminating in a jack at said operators position, an auxiliary jack associated with said trunk line, an automatic switch associated with said trunk line in said main exchange, other automatic switches in said branch exchange controlled from a calling one of said telephone lines to establish the connection with said trunk line, a signal at said operators position, means ,for operating said signal when said connection is established, and means whereby the operator at said position may operate said associated automatic switch from said auxiliary jack.

14. In a telephone system, a main exchange having an operators position, a branch exchange, telephone lines in said branch exchange, a trunk line interconnecting said exchanges and terminating in a jack at said operators position, an auxiliary jack associated with said trunk line, an automatic switch associated with said trunk line in said main exchange, other automatic switches in said branch exchange controlled from a calling one of said telephone lines to establish the connection with said trunk line, a signal at said operators position, means for operating said signal when said connection is established, means whereby the operator at said position may operate said associated automatic switch from said auxiliary jack, a second signal at said operators position, a source of signalling current, and means operative when the receiver is replaced at the substation on said calling line for operating said second signal.

15. In a telephone system, two automatic switches, a two way trunk line connecting said switches, a circuit including two controlling relays, one for each switch, each relay controlling an operating circuit for its associated switch, means for connecting with said trunk line at one end, means responsive to such connection for closing said circuit to energize both said relays and for then producing interruptions in said circuit to cause the controlling relay at the distant end to set the second switch, and means for preventing the said controlling relay at the near end from responding to such lnterruptions in order to prevent the setting of the first switch. l

16. In a telephone system, a trunk line having an automatic switch at each end thereof, a control circuit for said switches including two controlling relays, one for each switch, said circuit including a conductor of said trunk line, means controlled by a calling subscriber for closing said circuit, and operator controlled means for opening said circuit at a point between said relays.

17. In a telephone system, a trunk line having an automatic switch at each end thereof, a contrhl circuit for said switches including two controlling relays, one for each switch, said circuit including a conductor of said trunk line, means controlled by a calling subscriber for closing said circuit, operator controlled means for dividing said circuit into two sections by opening the same at a point between said relays, and operator controlled means for producing impulses in either section so as to set either of said switches by means of its associated controlling, relay.

18. In a telephone system, two automatic switches, a common control circuit including a controlling relay for each switch, sub scriber controlled means for closing said circuit to energize both relays, and operator controlled means for producing momentary .deenergizations of either relay to set its associated switch. while the other relay is maintained energized.

19. In a telephone system, a trunk line terminating at one end in an automatic switch, a controlling relay for said switch, means at the other end of said trunk line for closing a control circuit for said relay, said circuit including a conductor of said trunk line, operator controlled means at the switch end of the trunk line for closing a local circuit for said relay and for opening the original control circuit, the relay remaining energized, and operator controlled means forthereafter producing interruptions in said local circuit to cause said relay to operate the said switch.

20. In a telephone system, a trunk line terminatingin an automatic switch, means including a second switch controlled by a calling subscriber for connecting with said trunk line, a control circuit for said first switch closed responsive to the completion of the connection, interrupter contacts controlled by the calling subscriber for sending impulses over said circuit'to set said first switch,a pair of terminals connected in multiple with said contacts and adapted to be connected together to shunt said contacts when it is desired to prevent subscriber control of said first switch, and operator controlled means for closing said control circuit ov efa new path including operator controlled impulse sending contacts.

21. .Etn a telephone system, a trunk line terminating in an automatic switch, means including a second switch controlled by a calling subscriber for connecting with said trunk line, a control circuit completed responsive to such connection, a local control circuit for said first switch, a relay in said first control circuit having contacts for closing; said local control circuit, a pair of terminals included in said local control circuit in series with said contacts so that the closure of said loal control circuit by said relay depends onwhether said tcrimnals are connected or not, and operator controlled means for shunting said terminals in case the same are not connected.

22. Ina telephone system, a two Way trunk line connecting two exchanges, automatic switches in the first exchange for extending connections to and from said trunk line in connecting the same with subscribers lines in said first exchange, manual equipment associated with said trunk line at said second exchange, means in said first exchange for momentarily transmitting ringing current over said trunk line tQ-"QiVe a disconnect signal at the second exchange, and circuit arrangements such that said lastincans is controlled both by calling and called subscribers in said first exchange.

33. In a telephone system, two automatic switches, a trunk. linc connecting, said switches, means including a third switch controlled by a calling subscriber tor connccting: with said trunk line at one end, a branch oi said trunk line at the other end vcxtendingto an operators switchboard, and

FRED T. MADSEN.