US1568180A - Automatic telephone system - Google Patents

Description

W. T. POWELL AUTOMATIC TELEPHONE SYSTEM Jan. 5 1926.

Patented 5, 1926..

UNITED STATES PATENT OFFICE.

WINFRED T. POWELL, OF CHICAGO, ILLINOIS, ASSIGNOR TO AUTOMATIC ELECTRIC COMPANY, 01 CHICAGO, ILLINOIS, A CORPORATION OF ILLINOIS.

AUTOMATIC TELEPHONE SYSTEM.

Application filed April 14, 1917, Serial No. 161,957. Renewed May 31, 1924.

To all whom it may concern:

Be it known that I, WINFRED' T. POWELL, a citizen of the United States of America, and a resident of Chicago, county of Cook, and State of Illinois, have invented 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 relates more particularly to small systems of this charac: ter commonly known as private branch exchanges. These systems are largely in use by manufacturing or mercantile establishments of various kinds for providing local service between the difierent departments or ofiices.

In view of the more or less intimate relations of the subscribers, and of a variety of other factors which need not be discussed in detail, the service requirements in these small systems are radically different from those in a public automatic exchange; and it is possible therefore to omit or depart from certain constructions considered standard in the latter type of exchange with a view of simplifying the apparatus and reducing the first cost. Furthermore certain features wholly undesirable in a public automatic exchange may add greatly to the efficiency and usefulness of a private exchange and should be incorporated therein if possible Without unduly complicating the apparatus. With these objects in view I have designed animproved private automatic exchange system involving a number of features believed to be new which will be fully described hereinafter and more specifically pointed out in the appended claims.

In the accompanying drawings which will be referred to in this specification, Fig. 1 shows diagrammatically an established connection between a calling substation A and a called substation A in one embodiment of my invention- The system herein disclosed provides a number of link circuits common to all the subscribers of an exchange, each link comprising a finder switch C and a sim-' connection. Fig. 2 shows in detail the meconnector'H (Fig. 1).

Referring more in detail to the system shown in Fig. 1, the substation A is of the usual type of common battery substation in which the transmitter 3 and receiver 2 are connected in series with the line circuit and having also a calling device which may be of any Well known type, and which is represented merely by a pair of contact springs 5 and 6 and an interrupter 4 for breaking contact between said springs to thereby send impulses over the line circuit by opening the same. The substation A is also provided with a direct current ringer 7, whichwhen the receiver is on the hook is connected to the positive line leading to the central oflice and which is disconnected therefrom when the receiver is removed from the hook.

The line conductors 8 and 9 terminate in the central ofiice in sets of multipled contacts in the banks of the finder switches C, one of which sets is indicated by reference characters 2023 inclusive, and in multipled sets of contacts in the banks of connector switches such as D. The normal conductors 50, 51 and 52 extend to one of these latter sets of contacts. The line conductors 8 and 9 have allotted to them at the central exchange a combined line and cut-off relay 10 comprising two windings, one of which the winding 11, is of high resistance and few turns, being preferably of' German silver wire. Referring to the detailed showing in Fig. 2, the springs 13 and 15 are adjusted with stiff tension and a space left between the spring 17 and the bushing which controls the. springs 13 and 15, so that, when the winding 11 alone is energized the armature is attracted only far enough toforce the spring 17 out of contact with the spring 18, but not far enough to contact with spring 19, while springs 13 and 15 remain in normal position. When the winding 12 is energized rotary type of construction in which the I, wipers have no normal position but stand, when idle, on the last trunk used. A switch of suitable mechanical construction is shown in the Patent to Dietl No. 1,126,727. The circuits by which the finder switches are controlled, are however, believed to be new in certain respects and will be fully described in the detailed description which is to follow.

Permanently connected to each of the finder switches C is a connector switch D which is also of the single rotary type construction. Unlike the rotary line switches or finders, however, the switch D does not operate automatically to select idle trunks, but is directively controlled by impulses from the calling device of a substation to which it has been connected by the finder switch. This connector switch comprises briefly, a group of four relays, 53-56 inclusive, whose functions will be explained later, a motor magnet ,57, a set of wipers 58, 59, and 60, and a bank of contacts, over which said wipers are rotated, arranged preferably in the arc of a circle. The wipers have the usual double, or triple, construction, depending of course on the number of degrees in the contact bank, in order to permit their being continuously driven in one direction while always maintaining connection with some one of the contact sets in the bank. It should be understood that the showing of the wipers and bank in Fig. 1 is purely diagrammatic and that the actual construction of these parts is similar to that shown in the above mentioned Dietl patent.

In the preferred embodiment of my invention the connector bank consists of thirtyone contact sets, three contacts in each set. The upper and lower contacts in each set are line contacts, and the third contact is a test contact. Referring to Fig. 3, I have shown one contact ineach set of contacts of a connector bank. However, it is to be understood that there are three such contacts in each set. When in" normal position the switch wipers rest in engagement with the first set of contacts, which as shown in the drawing are dead, that is they have no conductors connected thereto. The eleventh and twenty-first contact sets of said bank are also dead, for reasons which will be vointed out later.

The substation A and the apparatus associated therewith is similar in all respects to the substation A and its associated apparatus.

While I have shown throughout the drawings a plurality of batteries, B, B, 13 etc it is to be understood that there is preferably but one battery having its positive pole grounded.

Having briefly described the apparatus,

I will now describe in detail the operation thereof when one subscriber calls another. For the purpose of this explanation it will be assumed that the subscriber A wishes. to obtain connection with the subscriber A, this connection being shown completely set up in thedrawings.

When the subscriber at substation A removes his receiver 'to initiate a call; a circuit is completed for the individual line relay 10 and the common starting relay 24, which circuit may be. traded as follows: ground G, armature 13, contact 14, line conductor 9, to and through substation A, line conductor 8, contact 16, armature 15, winding 11 of relay 10, and winding 25 of relay 24 to battery B. Upon the closure of .this circuit, relay 10 attracts its armature sulficiently to separate spring 17 from its back contact 18, the other springs being unaffected, as explained before. This operation results in the removal of ground G from the test contact 21 and its multiples, in the banks of the finder switches.

The common starting relay 24 also energizes over the above traced circuit, and upon energizing, connects ground to the starting wire 61 which extends to the starting relay of the first idle finder switch C, and also closes a circuit from ground G armature 27, contact 28, winding 26 of relay 24, interrupter springs 62, and relay 30 to battery B. The relay 30, upon energizing over this circuit, attracts its armature and breaks its own circuit at interrupter springs 62. It will be seen therefore that as long as the 1 starting relay 24 remains energized, that is, until the finder switch lands on the calling line, the relay 30 will vibrate in the manner of a buzzer to induce a tone in the calling subscribers receiver, due to the inductive relation between the windings of the relay 24.

In the description of the operation of the finder switch which is to follow, it will be assumed that the finder switch C is resting upon some line other than the line of substation A, and will be required to rotate in order to find and connect with the line to substation A. It should also be remembered that the test contacts, similar to the test contact 21, of all non-calling lines art connected to ground.

By the grounding of the starting wire 61,

a circuit is completed by way of armature 42 and its back contact 63, through the winding of line relay 31 of finder switch C to battery B The line relay 31, upon energizing, connects ground Gr by means of its armature 36 and front contact 37 to a terminal of the line switching relay 33', and

A of the non-calling lines.

completes an operatin circuit for the rotary magnet 32 over the to lowing path: ground on the test contacts, similar to testcontact 21, wiper 65, armature 46, contact 47, contact 39, armature 38, back contact and armature 68 of rotary magnet 32, and winding of rotary' magnet 32 to battery B. Since the rotary magnet 32 interrupts its own circuit by means of its armature 68 it will operate in the manner of a buzzer to advance the wipers 64-67 inclusive, step by step in search of the set of contacts 20 23 inclusive, of the calling line. It will be noticed that during the rotation of the finder, the winding of the line switching relay 33 is shortcircuited by the ground on the test contacts As soon however as the wiper finds the contact 21 of the calling line, from which ground has been removed, the relay 33 energizes over a circuit from ground G, armature 36, contact 37, relay 33, armature 68 and its back contact, and through the winding of the rotary magnet 32 to battery B. The relay 33 is of sufiiciently high resistance so that although the rotary magnet is included in the above traced circuit, it does not operatively energize and the finder therefore stops with its wipers in connection with the set of contacts 20-23 inclusive, of the calling line. The relay 33, upon energizing, shifts its contact springs to the position shown. with the result that the wiper 65 is disconnected by means of armature 46 from the-circuit extending to the rotary magnet; a circuit for the cut-off winding 12 of relay 10 is closed by armature 44 and its front contact, the starting wire 61 is disconnected from the line relay 31 and, upon the deenergization of relay 31, is connected to the starting wire 69 of the next finder switch; and the line conductors 8 and 9 of substation A are connected by means of armatures 48 and 40 and their front contacts with the trunk conductors and 71 leading to the associated connector switch D. i

The above mentioned holding circuit for the cut-off winding 12 of relay 10 may be traced as follows: from ground G armature 36, contact 37, contact 45, armature 44, wiper 66, contact 22, and through the winding 12 to battery B A branch of this circuit leads from the ground G to the wiper 22 and out over the private normal conductor 51.to the banks of the connectors, thereby protecting the line from seizure by any of said connectors. The line relay 31 it Will be seen is slow-acting and therefore retains ground (it connected to the above traced circuit until {ground is fed back from the connector by the energization of relay 53. The winding 12 of relay 10 ,upon energizing over the above traced circuit, has suflicient strength to fully attract its armatures, so that the line conductors 8 and 9 are disconnected from ground G and from the windings 11 and 25 of the line relay and starting relay upper Winding of re ay 53, trunk conductor- 70, contact 49, armature 48, wiper 64, contact 20, line conductor 8, to and through substation A, line conductor 9, contact 23, wiper 67, armature 40, contact 41. trunk conductor 71, lower winding of relay 53, and lower winding of relay 54 to battery B". Relay 53, upon energizing, repares a circuit for the rotary magnet 57 at springs 76 and 77, and also by separating springs 7 3 and 74 and forcing spring 73 into contact with spring 75, opens the release circuit for the connector and'closes a circuit from ground G, spring 73, contact 75, holding 32 tojbattery B. A branch of this latter conductor 78, and windings of relays 33 and circuit passes through contact 45 and spring 44 over a previously traced circuit to holdmgwinding 12 of relay 10,- it will therefore be seentliat the ground for maintaining the connection which was heretofore supplied from ground Gr through springs of relay 31, is now replaced by ground G, which is controlled by the slow acting release relay 53 of connector D.

It will therefore be seen that without any further-operation on the part of the calling subscriber other than the removal of his recelver, the calling line is extended into connection with an idle connector switch D, which is now in readiness to receive impulses. Let us assume for the purpose of this description thatthe number assigned to the line of substation A, with which connection is desired, is 4. The subscriber at substation A upon noticing the cessation of the tone or signal, supplied by the operation of relay 30, knows that a connector is ready to receive impulses. He therefore operates his calling device, which is indicated at .4, to separate; the springs 5 and 6 a number of times corresponding to the digits of the called numher. In this case, 4 being the called number, the calling device is operated only once to separate the springs 5 and 6 four times.

The line relay 54 in response to this operation of the calling device, deenergizes a corresponding number of times, and at each deenergization, transmits an impulse to the rotary magnet 57 over the following circuit: ground G, armature 72 and its back contact, contact 77, armature 76 of release relay 53, and through rotary magnet 57 and slow acting series relay 55 to battery B. The 130 rotary magnet 57 responds to this series of impulses to rotate the wipers 58, 59 and 60 7 'onto the fourth'set of contacts 79, 80 and 81 in the connector bank, to which contacts we have assumed the normals of the line leading to substation A to be connected. The relay being a slow acting relay does not respond to this series of impulses, as does the rotary magnet, but retains its armature ,in its attracted position as long as impulsesare delivered. The relay 55, upon energizing, moves the spring 82 out of contact with spring 83 and into contact with spring 84, thereby closing a circuit for the wiper cut-ofii' relay 56 which maybe traced from ground G, armature 82, contact 84, and winding of relay 56 to battery B". The relay 56, upon energizing, disconnects the wipers 58 and 59 from all connection with the magnets of the connector by means of armatures 85 and 86 and prepares a locking or testing circuit for itself by means of armature 87 and its front contact, the purpose of which will be explained. The off-normal springs 95 in the release circuit come into contact with each other as soon as the con nector takes the first step, but have no effect at this time.

The operation now depends upon whether the called substation A is idle or busy. A ssuming the line to be idle, as soon as the impulses cease, the series relay 55, deenergizes," and opens the circuit of relay 56 at contacts 82 and 84, and the relay 56-in turn, deenergizes, and closes a circuit for the cut-off winding 88 of the relay 89 associated with the called line, which circuit extends from ground G, armature 82,contact 83, armature 87 and its back contact, wiper 60, contact 81, and winding 88 of relay 89 to battery B The relay 89 is thereupon energized and disconnects the line winding 90 and common starting relay winding 25 from the line conductors of substation A.

Returning to the operation of the connector, the relay 56, upon deenergizing, eonnects the wipers 58 and 59 with the trunk conductors 70 and 71 and the line relay 54 which is in bridge thereof, and thereby closes a circuit for the ringer 92 of the substation A. This circuit may be traced as follows: battery B lower winding of relay 54, armature 86 and its back contact, wiper 59, contact 80, line conductor 94, hook switch springs and through the winding of the ringer 92 and its interrupter springs to ground G The called subscriber upon hearing his signal, removes his receiver from the hook, thereby disconnecting the ringer 92 from the line and connecting his receiver and transmitter in bridge thereof; The two substations A and A are now connected for conversation over the heavy conductors shown.

It will be noticed that the talking circuit which has been established does not include condensers as is usually the case in larger systems of this type, and the two substations are therefore connected in multiple, and are both supplied with battery current through the windings of the line relay 54 of connector D. As a further result of this arrangement, the calling subscriberis enabled to detect that the-cal ed subscribers bell is being rung, as the vibrations of the interrupter, associated with said bell, cause a vibration of the current flow in the calling line.

\ At the termination of the conversation boih subscribers replace their receivers. Assume that the subscriber at substation A has replaced his receiver. Then when the receiver at substation A is replaced the circuit of the line relay 54: and release relay 53 is broken at substation A and these relays are accordingly deenergized. The line relay 54 being quick acting falls back before the relay has time to deenergize and sends an impulse of current to the rotary magnet 57 from ground G armature 72 and its back contact, contact 77, armature 76, and windings of rotary magnet 57 and relay 55 to battery B. The rotary magnet energizes over this circuit and operates to step the wipers 58, 59 and 60 one step beyond the called line. The relay 53 also deenergizes a moment after the deenrgization of the line relay 54 and allows its armatures to resume their normal position. The separation of the armature 76 from contact 77 opens the circuit for the rotary magnet which was closed by the deener ization of the line relay. The armaure (3, upon falling .back, removes ground G from the holding trunk 7 8, and closes a new circuit for the rotary magnet 57 extending from ground G, armature 73, contact 7 4, off-normal springs 95, in terrupter springs 96, rotary magnet 57 and relay 55 to battery B5. The interrupter 96 heiug iucluded in the above circuit, the rotary magnet operates in the manner of a buzzer to rotate the wipers 58, 59 and 60 back to their normal positions in engagement with the first set of contacts, at which time the oft-normal springs 95 are separated, and the switch stands ready for another call.

\Vhen ground G is removed from the holding trunk 78, the line switching relay 33 of the finder switch and the cutoff winding 12 of the line relay 10, are deenergizel with the following results: The relay 33, upon restoring its armature, opens the trunk conductors and 71, opens the holding circuit. for the cut-oii' winding 12, and againincludes the relay 31 in circuit with the starting wire 61. It will be remembered that the tinder switch C has no normal position and that the wipers stand on the last trunk used. Therefore no releasing operation is necesrelay It) being opened thesaid relay/docuergizes and prepares the circuits associated with the calling line tonormal position in readiness to receive another call.

Let us assume now that the called line is busy when the wipers 58, 59 and 60 are rotated into connection therewith, in this case the test contact 81, associated with said called line, will be supplied with a ground potential, either from a finder switch, similar to C, which has seized the said line, or from a connector switch, similar to D, whichhas connected with some multiple of the contacts 79, 80 and 81. After the connector wipers 58, 59 and 60 have been rotated onto the said contacts 79, 80 and 81, and before the slow acting relay 55 has time to open the circuit of the wiper cut-off relay 56, a locking circuit is closed for the relay 56 extending from the ground of the occupying switch (not shown) to the test contact 81, test wiper 60, armature 87 and its front contact. and through relay 56 to battery B. The

relay 56 therefore does not fall back to cut the trunk conductors through, but remains locked in energized position until the switch is released or until the line of the called subscriber becomes idle. As the signaling of the called line depends-upon the deenergization of relay 56 it will be seen that no battery will be connected to the called line for ringing purposes and no interference caused with the talking circuit which is established therewith. In order to simplify the construction of this switch, no busy signal is provided, however it has been pointed out that a calling subscriber is notified when the called subscribers bell is being operated. It is therefore suflicient in a system of this character that a subscriber be notified that, in case this signal is not heard as soon as his call is completed he may know that the called line is busy and that he must either hang up his reeciver and call again or wait until the called line becomes idle.

In the description of the construction of the connector switch D it was pointed out that the bank of the switch comprises preferably 31 contacts although not necessarily limited to that number. Now since the calling device of the character used in a system of this sort is only capable of sending ten impulses, it will be explained how the connector is advanced to establish connection with those subscribers lines which terminate in contact sets further around than the tenth. Obviously'more than one operation of the calling device will be required. To permit successive operations of the switch to select one of these lines, the eleventh and twenty-first contact sets are left dead, and the intervening contact sets, namely, 2-10 inclusive, 2 $9 20 nclusive, and 22 to 3 inclusive, are connected to subscribers lines, making three groups of hnes. Now in order to call a subscriber 1n the second group, the

digit 0 is prefixed, and in order to call a subscriber in the third group, the digits 00 are prefixed.- Therefore'when 003 is called the connector is first rotated to the eleventh contact, which is dead, then to the twentyfirst contact which is also dead, and then to the third contact in the third group. It will be seen that this scheme may be extended to any reasonable extent, every ten sets of contacts which are added to the bank roviding for nine additional subscribers ines, and that the group to which the call is extended depends upon the number of series of impulses. It will therefore be seen that I have provided a very simple and ellicientsystem for use in small private branch exchanges, and having several new and desirable features.

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

\Vhat I claim as my invention is:

'1. In a telephone system, a calling line, a called line, a connector switch, means for operating said switch to connect said lines for conversation, a line relay in said con-' nector switch, a release relay in said connector switch, circuit connections whereby/ a talking circuit between said lines compris-' ing a finder switch and a connector switch, an operating magnet for said connector switch for moving the wi ers thereof, a relay having a pair of win ings, both of said windings being in series with the talking circuit, said relay deenergized by the calling subscriber alone and means controlled by the deenergization of said relay for causing said motor magnet to continue its operation and move the wipersto release the connection.

3. In a telephone system, a subscribers line, aswitch having access to said subscribers line to extend a connection therefrom, a signal, a relay controlled from said subscribers line for operating said switch to seize said line, and for applying said signal to said subscribers line only while said switch is operating.

4. In a telephone system, a subscribers line, a swi ch having ac es o sa sub scribers line to extend a connection theretrom, a signal, a relay controlled from said subscribers line for operating said switch to seize said line, and for applying said signal to. said subscribers line only while said switch is operating, and means controlled by said switch for disconnecting said signal from said line.

5. In a telephone system, a subscribers line, a switch having access to said subscribers line to extend a connection therefrom, a signal, a relay controlled from said subscribers line for operating said switch to seize said line, and for applying said signal to said subscribers line only while said switch is operating, and means controlled by said switch for disconnecting said signal from said line as soon as connection is established therewith.

6. In a telephone system, a pair of subscribers lines, a link circuit comprising a inder switch and a connector switch both having motion in one plane, means for operating said connector switch to establish a connection between said lines, said finder switch having no normal position, a motor magnet for controlling the operation of said connector switch, and means for continuing the operation of said motor magnet to release said connector switch and break said established connection.

7 In a telephone system, a calling and a called line, a link circuit for establishing a talking circuit between said lines comprising a finderswitch and a connector switch, a motor magnet for operating said connector switch, a relay having a pair of windings, both of said windings being in series with the talking circuit, said relay deenergized by the calling subscriber alone and means controlled by the deenergization of said relay for continuing the operation of said motor magnet to release said switches.

8. In a telephone system, a subscribers line, a switch having access to said subscribers line to extend a connection therefrom, a relay common to said lines and controlled therefrom to start the operation of an idle one' of said switches to connect with said line, and means controlled by said relay for applying a signal to said line until said connection is established.

9. In a telephone system, a subscribers line, a switch having access to said subscribers line to extend a connection therefrom, a relay common to said lines and controlled therefrom to start the operation of an idle one of said switches to connect with said line, and means controlled by said relay for applying a signal to said line in case all of said switches are busy. I

10. In a telephone system, a subscribers line, a switch having access to said subscribers line to extend a connection therefrom, a

useaiso relay common to said lines and controlled therefrom to start the operation of an idle one of said switches to connect with said line, means controlled by said relay for applying a signal to said line until said connection is established, and means controlled by said switch for disconnecting said signal from said line.

1-1. In a telephone system, an automatic switch, a plurality of groups of lines accessible thereto, said lines having terminals in said switch arranged in a single plane, wipers for the switch for extending connections to any of said lines via said .terminals, means for sending a plurality of series of impulses to said switch to select a group of lines, the group selected determined by the number of series of impulses delivered to the switch, means for then sending a single series of impulses to the switch to cause the wipers to connect with a particular line in the selected group and means for thereafter automatically advancing said switch to normal.

12. In a telephone system, an automatic switch, a plurality of groups of lines accessible thereto, said lines having terminals in said switch arranged in a single plane, wipers for the switch for extending connections to any of said lines via said terminals, means for sending a plurality of series of impulses to said switch to select a group of lines, the group selected determined by the number of series of impulses delivered to the switch, mean-s for then sending a sin le series of impulses to the switch to cause t e wipers to connect with a particular line in the selected group, and the line selected determined by the number of impulses in the final series and means for thereafter automatically advancing said switch to normal.

13. In a telephone system, an automatic switch having wipers and lines accessible thereto divided into groups, all of said groups being accessible to the wipers of the switch during movement in a single plane, a magnet for moving said wipers, means for sending a variable number of series of impulses to the switch said magnet responsive to a single series of impulses to select a line in the first group and responsive to a plurality of series of impulses to step the wipers over the contacts of the first group and into engagement with lines in other groups and means for thereafter automatically advancing said switch to normal.

14. In a telephone system, a calling and a called line, an automatic switch accessible to the calling line, a line relay for said switch, means controlled from the calling line for operating said line relay to control the complete operation of said switch to seize the called line, and means whereby oth calling n alled subscribers receive talking current through the windings of said line relay during conversation.

15. In a telephone system, a calling and .i a called line, an automatic switch accessible 5 tothe calling line, a line relay for said switch, means controlled from the calling -l in'e for operating said line rclayto control the complete operation of said switch to seize the called line, and'means whereby all the current is fed through said line relay for signalling the called subscriber and for supplying talking current to both the calling and called subscribers. 16. In a telephone system, a calling line, a called line, a connector switch having a magnet operable over a plurality, of branches, means for operating said magnet over one branch to connect said lines for conversation via said switch, means for thereafter operating the magnet over said branch to disconnect said lines and for thereafter automatically causing it to operate over another branch to restore the said switch to normal.

17. In a telephone system, a switch having a movement in a single 'plane, a wiperfor said switch, groups of subscribers lines terminating' in said switch, said subscribers lines being decimally designated, and means responsive to trains of impulses td step said wiper to'select a group of lines and a line in said group, the steps of said wiper in the group and line selecting movements being of equal length. 18. In a telephone exchange system, an impulse sendingdevice, a switch responsive to said sending device and comprising. stationary terminals, and a movable terminal arranged to move in a single plane, a plurality of groups of.subscribers lines terminating in said stationary terminals, and means responsive to impulses sent by said sending device on a decimal basis for mov ingsaid movable wiper toselect a group and a line in said group, the movements of the wiper being of equal length.

19. In a telephone exchange system, an automatic switch, a terminal bank therefor, groups of lines connected to certain'terminals on said bank, other terminals being allotted for group selection and interspersed between said groups of lines, means for selecting a group of lines decimally, and means for selecting a line decimally.

20. In a telephone system, a calling line, a first and a second called line, a connector switch having a magnet operable over a plurality of branches, means for operatin said magnet over one branch to connect sai calling line with said first called line for conversation via said switch, and for thereafter operating said magnet over said branch to disconnect said calling line from sai first called line and connect said. calling line to said second called line, and means for thereafter automatically causing said magnet to operate over another branch to restore the saidswitch to normal.

2l. In a telephone exchange system, an

'scribers line, an automatic adding-type connector switch controlled over the two sides of the subscribers line in series, a single row or level of bank contacts for said automatic switch, other subscribers" lines terminating in said bank contacts, subscriber controlled means for said switch for connecting said first subscribers line to any one of said other subscribers lines, means for ringing the called substation, and automatic means for moving said switch to normal position.

28. A telephone system including a subscribers telephone line, an automatic adding-type connector switch controlled over the two sides of the subscribers line in series, "bank contacts for said switch, subscriberslines terminating in said bank contacts, step-by-step means for said switch for .connecting said first subscribers line to any of said other subscribers lines, means for ringing thecalled substation, and automatic means for operating said step-by step means to move the wipers of said switch to a; nor mal position.

24:. In a telephone system, a switch having a movement in a single plane, a line relay for said switch, a wiper for said switch, groups of subscribers lines terminating in said switch, said subscribers lines being decimally designated, and a magnet directly responsive to" trains of impulses produced by said line relaygdor stepping sald wiper to select a'group of lines and a line in said group, the steps of said wiper in the group and line selecting movements being of equal length.

25. In a telephone exchange system, an impulse sending device, a switch responsive to said sending device and comprising station ary terminals and a movable terminal adapted to move in a single plane, a plurality of groups of subscribers lines terminating in said stationary terminals, a line relay for said switch responsive to impulses sent by said sending device, and a magnet for said switch directly responsive to said line relay to move said wiper step-by-step to select a group and a line in said group, the steps of the wiper being of equal length.

26. In a telephone system, an automatic switch having stationary terminals and a llllH'llliil wiper adapted to move in a single plum, groups of subscrlbers lm'es tenn1nating in said stationary terminals, a linerelay for said switch, and a magnet for said switch operative responsive to nnpulses pro-.

lily-step to selecfi a grouli and a line iii said group, the steps-0f the wiper being of equal length. 10 Signed by me at Cl1ieag0, Go0k County, State of Illinois, this 31st day of March,

WINFRED T. POWELL.

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