US727701A - Telephone system. - Google Patents

Description

No. 727,701. 'PATENTBD MAY 12, 1903.

. 0. B. SMITH. TELEPHONE SYSTEM.

APPLICATION FILED DEC. 31, 1897.

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No. 727.701. PATENTBD MAY 12, 1903. 0. B. SMITH, TELEPHONE SYSTEM.

APPLICATION FILED DIIQ.v 31, 1897.

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PATENTED MAY 12, 1903.

C. B. SMITH.

TELEPHONE SYSTEM.

APPLICATION FILED DEC. 31, 1897.

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TELEPHONE SYSTEM. APPLICATION FILED D110. 31, 1897.

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Q vwentoz JLEQJM dv-E Patented May 12,1903.

ATENT OFFICE.

CHARLES E. SMITH, OF NEW YORK, N. Y.

TE'LEPHONE'SYSTEM.

SPECIFICATION formingpart of Letters lPatent No. 727,701, dated May 12, 1903. Application filed December 31, 18l37. Serial No. 664.870. (No model.)

To aZZ whom it may concern: I

Be it known that 1, CHARLES B. SMITH, a citizen of the United States, and a resident of New York, in the county of New York and, State of New York, have invented certain new and useful Improvements in Telephone Sysa toms, of which the following is a specification.

One object of my invention is to provide a telephone system in which a limited number of wires will serve for a larger number of subscribers or telephone instruments.

telephoning-circuits as would be equivalent to about the average number of subscribers that would ordinarily be telephoning atthe same timesay five circuits. I

A further object of the invention is to enable any subscriber on the system to independently or individually call any other subscriber and also to enable the calling subsoriber to automatically make direct metallic circuit connections at his telephone instruments with an idle or unemployed circuit,

so that the called-subscribers telephone instruments will also make connections with said idle circuit to establish a complete closed' metallic circuit between the calling and the called subscribers without the necessity of using a central office.

In carrying out my invention I provide a telephone system comprising means for'selooting and calling or signaling to the desired subscriber direct, and means by which an idle or unemployed circuit can be automatically selected andconnected through the telephones of the calling and the called subscribers for telephoning purposes. It will be understood that the wires over which the selecting of the desired station and the signaling to the same is done are distinct from the wires used for the telephoningecircuits.

Reference is to be had to the accompanying drawings, forming part hereof, wherein- Figures 1 and l are diagrammatic views of my improved telephone system, and when considered together they represent four stations or sets of operating devices A B C D,

all the devices in stations A and 0 being in their normal positions and the telephoning devices in stations B and D being shown counected together in a closed metallic circuit For in stance, for one hundred subscribers or telephone iustruments I provide such a number of ready for telephoning. Fig. 2 is a front elevation of an instrument provided with the appropriate devices for operating the system complete. Fig.3 is a side elevation thereof ilooking from the right in Fig. 2. Fig. 4 is a front elevation of the devices that serve to transmit proper impulses to select desired subscribers calling instruments and to give a call or signal when said instruments are so selected. Fig. 5 is-a side elevation thereof looking from the left in Fig. 4. Fig. 6 is a side elevation thereof looking from the right in Fig. 4, parts being broken away. Fig. 7 is a front elevation ofthe circuit-changing or circuit-controlling devices which are caused to operate by the devices shown in Figs. 4, 5, and6 for selecting the station desired, forgiving a call or-signal thereat, and for returning all the corresponding devices to their normal positions automatically. Fig. 8 is a side elevation thereof looking from the right in Fig. 7. Fig. 9 is a front elevation of the devices that serve to select an idle or unemployed circuit for telephoning, to connect the telephones of a calling and a called subscriber, and .to return the circuits to their normal idle conditions. Fig. 10 is a side elevat-ion thereof looking from the'left in Fig. 9, part being broken away. Fig. 11 is a horizontal section on the plane of the main shaft shown in Figs. 9 and 10; and Fig. 12 is a plan, projected, of the switching cylinder or drum shown in Figs. 9, 10, and 11.

It will be understood that Figs. 2 to 12, inclusive, illustrate a form of mechanism that I have devised for carrying the system into practice and that said mechanism corresponds in function with the similar parts illustrated diagrammatically in Figs. 1 and 1.

I will first describe how one subscriber on the system is enabled to select the callinginstruments of the subscriber he desires, to give a call or signal at said instruments, and to return to their normal positions all those instruments that have been operated in giving said call, and I will then explain how the telephone instruments of the calling and the called subscribers are connected together for telephoning and how the corresponding cirunits and instruments are returned to their normal positions after the subscribers have finished conversing.

In Figs. 1 and 1, A B O D indicate generally subscribers stations at which are located the various devices that constitute the operative parts of the system, and these devices are connected by appropriate circuits. In the several views similar letters and unmerals of reference indicate corresponding parts wherever they occur. In order to accomplish the selecting of the desired station and signaling to the same, I provide a series of four wires, which are apportioned to the calling system. Of these wires one is an itidependent battery-wire 1, Figs. 1 and 1, having opposed batteries 3 3 at the two ends, suchhatteriesbeinggrounded. Thisbatterywire is looped into each station, and the current from it is thrown on the other lines to operate the parts connected therewith,as hereinafter described. The other three wires are in reality one wi re passing three times through each station. One length of this line is in sections grou nded at each station,but adapted by the operation of the appropriate parts to be connected in one continuous line from the first station to the station to be called. The other two lengths are looped into the stations and adapted to have the battery current thrown on them to operate the mechanisms, as hereinafter described. The wires for telephoning-circuits may be of such number as the necessities of the system may require.

When in this specification I use the term station, I desire it to be understood as embracing the devices, conductors, contacts, &c., that are apportioned to a subscriber on the system.

The selecting, the calling or signaling, and the restoring devices and circuits may be described as follows:

1 is a conductor or circuit leading through all the stations, and it is shown grounded at both ends at 2 2, and near each end said circuit is provided with a battery 3 8, as before stated, and the corresponding poles of these batteries are opposed on the circuit, so that the circuit will normally not be charged. At each station on the circuit is located a rotative toothed wheel 4, that is preferably in electrical connect ion with its supporting'shaft 4 and the framework 4 of the device.

4 is a handle for rotating shaft 4 and wheel (See Fig. 3.)

The wheel 4 is shown provided with contacts or metal rings 5 5 5*, which are insulated from said wheel and can move therewith. Contacts 6 6 6", carried by the frame 4 and insulated therefrom, are in engagement with the contacts 5 5 5", respectively. (See Figs. 2 and 3.) The contacts 6 in the several stations are each connected with the line 1, as by a wire 7. Contact or ring 5 is connected, as by a conductor 8, with a switch 9, that is pivotally carried by wheel 4, butinsulated therefrom. The switch 9 is adapted when properly moved to engage a contact or pin 10, that is in electrical connection with wheel 4, and thus with the frame 4" of the device. (See Fig. 4.) In its normal home position the switch 9 engages a stop or pin 9, that is carried by frame 4 andthus keeps the switch 9 from engagement with pin or contact 10. (See Figs. 4, 5, 6.) The frame 4 has an annular series of apertures 11, that are shown located in a ring or plate 12 of frame 4, and these apertures are so arranged that when a plug 13, Fig. 3, is placed therein said plug will be in the path of said switch 9 to cause the latter to move into engagen'ient with contact 10. The apertures 11 are all numbered consecutively, and each represents a subscriber or station on the circuit. The frame 4 (or as shown in diagram in Figs. 1 and 1) is connected with a conductor 14, that leads to two contacts or springs 15 16, which respectively fortn part of a calling or signaling circuit and of a subscriberselecting circuit. The contacts or springs 15 16 do not coact; but each has a companion contact 15 16, frotn which it is nortnally disengaged, but is adapted to make contact therewith through the action of the wheel 4. The contacts 15 16 are connected with a circuit17, as by conductors 15 16". This circuit has portions 17, 17, and 17 leading through all the stations, the portion 17 being normally closed through the switching devices above described, as follows: The contact 6 is connected with one portion of circuit 17 by acouductor 1S, and contact 6 is also connected with circuit 17 by a conductor 18. The contact 5 is connected by a conductor 19 with a switch 20, that is pivotally carried by wheel 4, but insulated therefrom. The switch 20 is in normal engagement with a pin 21, that is insulated from wheel 4 and connected with contact 5 by a conductor 21. (See Fig. 4.) Thus the normal circuit of line 17 at this portion in each station leads from line 17 through 18, 6, 5, 19, 20, 21, 5, contact 6", and conductor 18 back to line 17. Switch 20 is pivotally connected with switch 9 by a link 22, that is insulated from said switches, so that switch 20 will be moved by and with switch 9. It will be understood that when wheel 4 is moved to select a subscriber switch 9 will engage the plug 13, that has been placed in the appropriate aperture 11, so that when switch 9 is moved into engagement with pin 10 (by engaging plug 13) switch 20 will be moved out of engagement with contact 21, thus breaking the normal circuit through line 17 at this part. The teeth 4 4 upon the periphery of wheel 4 are adapted to close and open the circuit through 17 at 16 16 for the purpose of transmitting an impulse or impulses to select the desired subscriber after the normal circuit through 6 6", &c., has been broken, (after wheel 4 has been turned to select a subscriber and switch 9 placed in contact with pin 10,) in which case the circuit through the instrument under consideration will be as follows: from grounds 2 and 2 at the ends-of the system through batteries 3 and 3 and line 1 to the corresponding conductor ICC 7 in the operating-station,thence through contacts 6 5 8, switch 9, pin or contact 10, wheel 4, frame 4", conductor 14, spring or contact 16, and its companion contact16 (when 16 and 16 are made to engage) and 16 to line 17, and thence to portion 17 a of the circuit, on which are located the switching or selecting devices that serve to connect the calling subscriber with the subscriber desired. These selecting devices consist in each station of a cylinder or drum 70, carrying on its surface plates or contacts, such as 45 37 55 32 42. or contacts are of different lengths to suit the duration of contact required in each case. This drum 70 is adapted to be rotated in one direction only,making one forward movement when a magnet 39 attracts its armature 39 and another forward movement when said armature is retracted by a retractile spring 79. (See Fig. 8.) This operation will be described more fully hereinafter. The rotation of the drum 70 is designed to bring plates or contacts 45, 37, 55, 32, and 42 in contact with springs or contacts arranged to bear upon them at the proper time. These plates or contacts on drum 70 are duplicated eight times on the circumference thereof. (This number may be increased or decreased in proportion to the size of drum and amount of its movement.) In the normal position of drum 70 the relation of these contacts to their contacting springs is as follows: Oontact'45 is out of engagement with springs 44 and 46, contact 37 is out of engagement with 35 and 36, contact is out of engagement with springs 54' and 56, contact 32 is in engagement with springs 31 and 31, and contact 42 is in engagement with springs 41 and 43. The first forward movement of drum brings one of the contacts 45 into engagement with spring- contacts 44 and 46. None of contacts 37 are by this movement brought into contact with 35 and 36,and' neither of the contacts 55 is as yet brought into engagement with 54 and 56; but a contact 32, beingalong contact, continues to be in engagement with springs 31 and 31. A contact 42 is now out of engagement with 41 and 43. The second forward movement of drum 70, caused by the retraction of spring of armature39, brings contact 45 out of engagement with 44 and 46, contact 37 into engagement with 35 and 36,

' contact 55 into engagement with 54 and 56,

fourth movement (last movement) of drum 70, caused by the armature 39 being again retracted by its spring, brings the contacts to the normal positionfirst described; but it These plates will be noticed that the springs that are now in engagement with contacts are bearing upon contacts on the drum "belonging to a second series of such contacts.

The circuit through 17 at the first station I on a system, as A, normally leads to ground at 30, and throughout the remainder of the stations this circut is divided or sectional that is to say, it is not a normally closed cirthe next station; but this section is normally disconnected from the portion leading into a station from a preceding station, although the portions leading into and from a station are adapted to be connected together in each station. I have denominated this portion, of the subscriber-selecting circuit as 17 through out, and for convenience of further description I have lettered the portion of this circuit that leads from a station as 17 and the part where it leads into a station as 17 In each station the subscriber-selecting circuit leads from 17 to the contact or spring 31, that normally engages contact or plate 32, which latter is normally in engagement with contact 31, that is connected by a conductor 33 with ground 30 through relay-magnet 34. The subscriber-selecting circuit from the switching devices in a station when wheel 4 has been turned to select a subscriber is as follows: to ground 30 at the first stationon a system, as A, from grounds'2 and 2 through batteries 3 and 3 over line 1 to the callingsubscribe'rs station, as B, thence through conductor 7, contacts 6 5, conductor 8, switch 9, and contact 10, ( parts 9 and 10 having been brought into engagement by the movement of wheel 4, causing switch 9 to strike the plug 13, and the normal circuit through 17- having been broken, as before explained',) to wheel 4, thence through contact 16 (by the action of teeth4 of wheel 4) and the conductor 16 to line 17, thence over line 17 to station A, and through 18, 6, 5,19, 21, 5", 6 and 16 back to 17, (the switch 4, &c., at' A not having been moved,) thence 'alongline 17 to 17*and through its part 17 to 31, 32, 31 7 and magnet 34 to ground 30, thus energizing said magnet. If any other station on the system farther from A than'B had been the calling-station, the circuit would likewise have been through the parts 6 6", &c.,at each station between the calling-station and the first station, as A, to ground thereat, the object being to operate the subsoriber-selectingdevices at the first station on the line, as A, first and then to operate the corresponding devices at the second station, and so onsuccessively to the desired station; but if station A had been the calling-station the circuit would have leddirect from 1616 thereat through line 17 to portion 17. It will be un derstood that each time a tooth 4 of wheel-4 makes the circuit at 16 16 an impulse will be sent over circuit 17 17*, &c., the number of such impulses corresponding to the number of the station called. As the portion 17 of the subscriber-selecting circuit is divided or sectional in each station, the various grounds in all stations up to the called station are to be broken and the corresponding portions 17 17 of the circuit through 17 are to be connected to form athrough -line between the calling and the called stations. This is accomplished as follows: Conductor 17 in each station is connected with a spring-contact 35, and the conductor 17 in each station is connected with a spring-contact 36; but these contacts are normally out of engagement, although, as before stated, they are adapted to be brought into electrical engagement by contact or plate 37. The contact 37 is to be broughtinto engagement with contacts 3536 after contact 32 has been moved away from contacts 31 31 Thus after contact 32 in a station is moved away from contacts 31 31? to break ground 30in that station contact 37 will be brought into engagement with contacts 35 36 in the same station to establish a through-line to thenext station, and so on successively in stations that intervene between the first station on the line, as A, and a station to be called. It will be understood that the magnets 34 control the movements of said contacts or plates. For this purpose I have shown a normally open local circuit in each station comprising a contact 38, conductor 38 magnet 39, a conductor 40, leading to a wire 27, that includes a battery 28, and a conductor 40, leading from wire 27 to an armature 34 of magnet 34, which armature (or a contact operated thereby) is adapt ed to close this local circuit by engaging contact 38. Magnet 39 operates the armature 39, as before stated. Thus when an. impulse is sent through magnet 34 the latter will act through its armature 34" to close the said local circuit at 34 33 to cause contact 32 to move away from contacts 31 31 to break the normal ground-circuit to 30 in the corresponding station. If a station beyond is desired, contact 37 will be brought into engagement with contacts 35 36 to establish a line from the station being considered to ground 30 in the next station on the circuit, and so on successively to the desired station, in which contact 32 is held under 31 31 temporarily to enable the bell circuit to be completed. Means for breaking the line so established and for ree'stablishing the ground 30 in each station will be explained hereinafter.

With the devices so far described let it be supposed that a subscriber at station E desires to select a subscriber at station D. He first places his plug 13 in the aperture 11 corresponding to station D and then turns his wheel4 by means of handle 4 to the left in the drawings until his switch 9 is moved against plug 13, the continued movement of wheel 4 causing switch 9 to turn on its pivot until the pin 10 passes into engagement with said switch 9. The wheel 4 is thereupon returned to the home point either directly by the operator or by suitable mechanisms, as hereinafter explained. The said movement of switch 9 also moves switch 20 away from the contact 21, and these switches remain so placed until wheel 4 arrives at the home point, where both switches are moved to their normal positions by switch 9 engaging stop 9*, wheel 4 continuing to move the proper ground 30 at station A (the first station on the circuit) and causes magnet 34 to close the local circuit through magnet 39. The drum 70, at A, now makes the first movement, before described, bringing contact into engagement with 44 46, contact 32 remaining in engagement with 31 and 31 and moving contact 42 out of engagement with 41 and 43. The circuit of magnet 34 is now broken at 16 16 in the calling-station by the action of teeth 4 of wheel 4, whereupon said magnet at sta tion A releases its armature 34, causing the local circuit through magnet 39 to be broken at 38. Magnet 39 thereupon releases armature 39, and its retractile spring effects the second forward movement of the drum, bringing contacts 32 out of engagement with 31 31,

thereby breaking off the ground 30 at station A. Contact 45 is now out of engagement with 44 and 46, and contact 37 is brought into engagement with contacts 35 36, whereby two sections of the line are joined together at A, as from 17 to 35 through 37 and 36 to 17-, the new line now leading therefrom through 17 at B to 31, 32, 31, 33, through magnet 34,

to ground 30 at B. The next impulse and break over the line so formed causes a similar operation of drum at B, breaking 01f ground 30, and causing two sections of theline 17 to be similarly connected at B. A third impulse has the same effect at (J, and thus a line has been established out of the various sections through stations A, B, and 0 direct to ground 30 at D. As D is the station to be called, a through-line to the next station beyond is not formed; but the fourth impulse is held on the line while a call is being given magnet 34 at D, holding its armature attracted. Magnet 39in consequence holdsits armature 39 closed, keeping contact 32 of drum 70 still in engagement with 31 31, thus holding ground 30 in station D unbroken. By this impulse contact 45 has been brought into engagement with contacts 44 and 46 and is held there to edect the operation of calling.

"The manner of sending a call and of holding the circuit complete and of preventing the completion of the circuit through 17 to the next station (beyond D) is as follows:

The first impulse sent over The wheel 4 carries a circuit-operating device 23 23*, that is adapted to make and break connection between the contacts l5 -in order to give a call or signal in the desired station and subsequently to restore all the subscriberselecting instruments that may have been operated to their normal positions. This signaling and instrument-restoring circuit at this part of the system may be traced as follows: from grounds 2 and 2 at each end of the possible intermediate station to the desired station. The device 23 is a projection or tooth carried by wheel 4, and the device 23, is similar, but preferably longer, to produce a closing of the circuit of comparatively long duration, and there is a space 23 between the teeth or projections 23 23 to produce a break in the flow of the current. The last tooth, as 4*, on wheel 4 is longer than the teeth 4 and is placed in line (laterally) with tooth or projection 23, the arrangement being such that while tooth 4 which corresponds to the selected'station) holds contacts 16 16 together tooth 23 will hold contacts 15 15 together to produce the call or signal, and the tooth 4 will continue to so hold the selecting-line until after projection 23 leaves contact 15 whereupon tooth 4 releases contact l6 and breaks the circuit through the selooting-line. Thereupon projection 23 acts to again close the circuit through contacts 15 15 to restore to normal all the subscriberselecting devices that may have been operated in selecting the desired subscriber, all as more fully explained hereinafter.

The circuit through line 17 is normally closed in each station and is adapted to be broken and re-formed in two ways, one for calling or signaling and the other forrestoring, the arrangement being as'followsz In each station for convenience of description the part of line 17 that leads into a station is numbered 17 and the part leading from the station is numbered 17K The part 17 of line 17 in each station leads to the contact or spring 41, that normally engages the contact or plate 42, which is in normal engagement with the contact 43, that is connected with the appropriate part 17 ofline 17.

Line 17 continues from contact 43 in one station through the part 17 of thelinein the next station to contact 41 thereat, and so on through each station, the line being open at the extreme station, as A, on the system. Thus a normal closed line is established in 17 through all the stations from right to left 1 by the magnet 49.

the local circuit.

through magnet 49 to ground 48.

in Figs. 1 and 1*. In each station the contact 44 is connected, as by conductor 44, with the part 17 of line 17 and contact 44is adapted to be engaged by the contact or plate 45, but is normally out of engagement therewith. Contact or plate 45 is also normally out of engagement with but is adapted to engage a contact 46, which is connected by a conductor 47 with ground 48, (or a common return -wire connected with all conductors 47 on the system,) and the conductor 47 includes a magnet 49. Thus when contact 45 in a station is moved into engagement with contacts 44 46 (the arrangement being sucn that at this time contact 42 will have been moved out of engagement with contacts 41 43, as before explained) the line 17 in that station will be grounded. the through-line in this station having been broken at 41 42 43, and the new circuit will be as follows: from part 17 of line 17 to 44, thence through 44, 45, 46, 47, and magnet 49 to ground 48. The circuit so established is for calling or signaling in a selected station, and by preference I utilizea calling instrument 50 on a normally open local circuit in each station that is controlled This local circuit is shown as follows: 51 is a contact from which a conductor 52 leads to wire 27, hell or signaling instrument 50 being located on conductor 52.

The circuit passes thence through 27 battery 28, and conductor 40 to a conductor 52, that connects with an armature 49 of magnet 49, which armature or a contact operated thereby is adapted to engage contact 51-to close Thus if while contacts 44, 45, and 46 are in engagement an impulse is sent along line 17 by the closing of contacts 15 15 a circuit will be established to ground 48 at the station to be called, as follows: from the ground of line 1 and its batteries through said line to the calling-station, as B, thence through conductor 7, contacts 6 and 5, conductor 8, switch 9, contact 10, (with which said switch will be in engagement, as before explained,) wheel 4, frame 4", conductor 14, contacts 15 15 ,(which are now held in engagement by presser 23,) to conductor 15, to -line 17, thence along line 17 through any intervening stations to the end of the system, (at the right in Fig. 1 thence to portion 17 of the line to the selected station D, thence I through portion 17 of the line to conductor 44*, contacts 44 45 46, and conductor 47, Magnet 49 will now attract its armature 49 to close the local calling-circuit from 51 through 52 (including instrument 50) to line 27, through battery 28 to conductor 40, thence through thereby,) back to contact 51.

selected station, as D. By preference I'utilize this closing of the local bell-circuit to also perform an operation with relation to the telephone-circuits, as hereinafter explained.

It will be understood that the stations are selected from left 'to right in Figs. 1 and 1 through the stations that intervene between the first station and a station to be called and that the contacts 42, 32, 37, and 45 are only moved in selectinga subscriber in the instruments (on the system) that intervene between the first station and the station to be selected and in the latter station sufficiently far to disengage 42 from 41 43 and to engage 45 with 44 46, (contact 32, it will be remembered, is still in contact with 31 and 31,) whereby line 17 is left normally closed from the opposite end of the system (on the right in Fig. 1) through all the stations to ground 48 at the selected station.

After a call has been given, as explained, the circuits through those instruments that have been operated in selecting a subscriber are to be returned to their normal positions. This may be accomplished as follows: From the conductor 44 in each station a conductor 53 leads to a contact 54, that is normally out of engagement with but is adapted to be engaged by a contact or plate 55. Contact or plate 55 is also normally out of engagement with but is adapted to engage a contact 56, that is connected by a conductor 57 with the conductor 33, leading to ground 30. Contact 55 is so located that it will engage its contacts 54 56, while contact 37 engages its contacts 35 36; but contact 55 is wider than contact 37, so that it will remain longer in engagement with its contacts 54 56 than contact 37 does with its contacts 35 36. Now atter an impulse has been sent over the line 17 to ground 48 to produce a call, as before explained, the projection or presser 23 on wheel 4 at station B will pass from contact 15, and thus cause the latter to break the circuit at 15 15, whereupon all the contacts 42 32 55 37 45 will be operated and in such manner that contacts 37 and 55 will be moved, in manner before described as the second movement, into engagement with their respective contacts 35 36 and 54 56, whereupon two sections of line 17 are joined together, as before explained, and a new ground is formed for line 17 from 17 through 53, 54, 56, 57, 33, and 34 to 30 in all stations whose corresponding instruments have been operated. Wheel 4, continuing to move toward the home point, next causes projection 23 (by pressing 15 15 together) to send current over the circuit from grounds 2 and 2, through batteries 3 and 3, over line to the calling-station, thence through conductor 7, contacts 6 5, wire 8, switch 9, contact 10, wheel 4, frame 4, conductor 14, contacts 15 15, and conductor 15 to line 17, (all at the calling-station,) thence to line 17 and along the same to the called station, in which the circuit passes from 17 to 44, thence to 53, 54, 55, 56, 33, and through magnet 34 to ground 30. Magnet 34 now closes the before described local circuit through magnet 39 at 34 38, and the armature of magnet 39 thereupon acts to move contacts 42, 32, 55, 37, and 45, whereupon the circuits through 37 will be broken; but the circuit through 55 will be continued a little longer than through 37 to assure the complete action of magnet 30. Then the circuit through 55 will be finally broken, while at about the same time contact 42 will be brought into engagement with its contacts 41 43 to restore the normal circuit of 17 through the instrument. Thereupon the current now on the line will travel through all the instruments on the line that may have been operated, performing the same restoring operations in them all. The current being next broken from the line by the passing of projection 23 from contact 15, the set of contacts 42 32 55 37 45 will be given a further movement to finally restore all the circuits to their normal conditions, thus bringing contact 32 into engagement with contacts 31 31 and leaving contact 42 in engagement with contacts 41 43. It will be understood that these actions take place successively in all the stations that have been operated in reaching a desired station.

It is desirable when one subscriber is operating the above-described devices to select and call another subscriber that any other subscriber will be prevented from operating his corresponding instrument, and for this purpose at each station I place a magnet 24 in the line 1; but this magnet is normally shunted from the line as follows: From line 1 on one side of its connection with magnet 24 extends a conductor 24, that leads to a contact 24, that is in normal engagement with a spring or contact 24, and from the contact 24 extends a conductor 24, which joins line 1 on the side of magnet 24 opposite to the connection of conductor 24 therewith. The wheel 4 carries a stop or presser 25, that holds the contacts 24 24in engagement when wheel 4 is in its normal home position; but when wheel 4 is moved away from its normal position contacts 24 24 will separate, thus breaking the shunt around the magnet and allowing the battery on line 1 to energize said magnet. Magnet 24 thereupon acts to close a normally open local circuit through a magnet 26 at each station. The local circuit for each magnet 26 is arranged as follows: lVith one terminal of said magnet is connected a cond uctor2'7, which leads to battery 28, thence to contact 27, which is adaptedto be engaged by an armature 24 belonging to magnet 24, and said armature is connected with the other terminal of magnet 26 by a conductor 27. The armature 26 of magnet 26 is adapted to operate a detent or finger 26", that is arranged to engage the teeth 4 on wheel 4 to prevent the corresponding wheel from being turned far from its home point. Thus when the line is being used for calling and a subscriber turns his wheel 4 far enough to disengage his switch 20 from its contact 21 the line will be charged from battery 3 0r 3 through the new circuit formed by switch 9 engaging contact 10, and if another subscriber starts to move his wheel 4 he will immediately break the shunt around his magnet 24, thus allowing the current on line 1 to energize his magnet 24. This magnet 24 will then attract its armature 24, thus closing the local circuit 27, 27, 24 and 27 through magnet 26, and battery 28 will cause magnet 26 to attract its armature 26, which will move detent 26 in the path of teeth 4 of wheel 4, and thus block or check the intended movement of wheel 4. By this means all subscribers are prevented from interfering while a calling subscriber is operating his device to select a subscriber and to signal to him; but as soon as wheel 4 of the calling subscriber has reached its home point the stop 9 will move switches 9 and 20 to their normal positions, thus removing the charge of the current from line 1 to enable any other subscriber to operate his wheel. In Figs. 4 and 5 the detent is shown carried independently of armature 26 and connected therewith by a light spring 26, which will act to throw the detent into engagement with teeth 4 of wheel 4 to prevent forward movement thereof and yet allow said wheel to return to its normal position without interference.

As the several subscriber selecting, calling, and restoring circuits have been described generally, I will now explain the mechanical devices I have illustrated whereby certain changes in the circuits are effected in conjunction with the circuits set forth. In the construction illustrated in Figs. 2, 3, 4, 5, and 6 I have shown a spring 60, that is connected at one end with shaft 4 of the selecting and calling switching devices, the other end of the spring being connected with the frame 4 and so arranged that as the wheel 4 is turned to the left in Fig. 4 the spring will be wound, and when the wheel is released said spring will act to return the wheel to zero or the home point. To cause wheel 4 to return to the normal position at the proper speed, I provide a train of gear-wheels 113V? ing a fan 61 and a main gear 62, loosely hung on shaft 4*, but having a spring-acting pawl 63 to engage a ratchetwheel 64, secured on shaft 4. \Nith this arrangement as the selecting-wheel 4 is turned in the direction of arrow at in Fig. 4 the'teeth of the ratchet 64 will slip under the pawl 63; but when said wheel 4 is released the ratchet, acting through pawl 63 and the train of gearing, will cause fan 61 to rotate, and thus retard or regulate the speed of return of wheel 4 to zero to the proper degree.

I will now describe more fully the mechanical devices (shown in Figs. 2 to 6, inclusive) for regulating the impulses sent along the circuits before described, for selecting thedesired subscriber, for giving a call, and for returning the parts to their normal positions, asfollows: The companion contacts orsprings 15 15 and 16 16' and 24 24 are shown carried by frame 4", but insulated therefrom. In Fig. 4 contacts 15 16 are shown connected by a plate 15, and in Figs. 4 and 6 contact 15 is shown capable of being movedinto engagement with contact15, while in Figs. 1 and 1 contact 15 is arranged to be moved against contact 15. In Figs. 2 to 6 I have shown rocker arms or levers 65-66, that are pivotally carried by a rod or shaft 67 of frame 4 andindcpendentlymovablethereon. Arms 65 66 are arranged to operate contacts 16 15, respectively, and they carry insulated points 65 66*, that engage said contacts. At their ends opposite this insulation the arms 65 66 have projections or fingers 65 66 the projection 65 being arranged to engage teeth 4 4 of wheel 4, while the projection 66 is adapted to engage the projections 23 23 and to pass into the space 23 between the latter. The number of teeth 4 4 .on wheel 4 are equal to the number of subscribers on a circuit; but tooth 4 is longer or wider than the tooth 4 to produce a longer contact, so as to hold contacts 44 45 46 together in the selected station while a call is being given. There is a long space 4 on the periphery of wheel 4 between tooth 4 and the first tooth of the series of teeth 4. tion 65 of arm 65 normally rests against that side of the first tooth 4 that faces the tooth 4 so that arm 65 will normally be tilted to cause contacts 16 16 to be normally separated. Arm 66 carries a pin- 66, that normally rests against frame 4 to enable contacts 15 15 to be normally separated, and the outer end of projection 66 normally lies within the path of the outer surface of projection 23. The working sides of projections.

65 66 are inclined to enable the projections to ride up on teeth 4 4 and on projections 23 23 These projections 23 23 are shown comprised in a plate having a space 23",

which plate is secured on the side of wheel 4 The presser 25 in line with rocker-arm 66. is shown in the form of a finger carried by .wheel 4, and it may be insulated therefrom or have insulation where it presses contacts .24" 24 together, said contacts being normally held in engagement by said presser. The detent 26 is shown pivotally carried by frame ed on insulation b, carried by wheel 4, so as. to move along the face thereof, and link 22.

may travel in a recess 22 in said insulation, Figs. 5 and 6. The insulation 11 carries a pin 1), against which switch 9 is pressed when it engages stop or pin 9 on ring 12, whereby wheel 4 is brought to rest and held at the,

home position under theintluence of spring 60. The devices by which contacts 45, 37, 55, 32, and 42 are carried and operated are illustrated in detail in Figs. 2, 3, 7, and 8 and are arranged as follows: These contacts are (See Fig.4.) The projec-v secured upon a drum or cylinder 70, preferably of insulating material, although it may be made of metal and the contacts insulated from it. The said contacts are arranged upon the drum 70 in the relative positions shown in Fig. 7 for controlling their respective circuits at the proper moments. One of each of these contacts 45 37 55 32 42 comprise a complete set, and there may be any desired nurnber of such sets of contacts upon each drum 70. In the arrangements shown provision is made for eight sets of such contacts. The drum 70 is supported by shaft 71, which is journaled in hearings on a frame 72, so that said drum can rotate, or said drum may be mounted loosely on said shaft. To thedrum 70 or its shaft 71 is attached a toothed wheel 73, having twice as many teeth 73 as there are sets of contacts 45 55 32 42. To the frame 72 are pivotally connected arms 74 75, which are adapted to oscillate, these arms being shown pivoted at 74 75 to a support or plate 76 of frame 72. The arms 74 75 carry pawls 74 75", respectively, which pawls are adapted to engage the teeth 73 of wheel 73. (See Fig. 8.) The arms 74 75 are respectively pivotally connected by links 77 77 with a lever 78, and the lever 78 is pivotally connected with frame 72, as at 78, being shown secured toa shaft 78", journaled in bearings carried by frame 72. (See Fig. 7.) The armature 39 of magnet 39 is connected with lever 78, so that when said armature is attracted by magnet 39 the lever 78 will be turned on its axis to draw links 77 and 77. Lever 78 is connected by a spring 79 with frame 72 to act against the attraction of magnet 39, the spring 79 serving to cause lever 78 to push links 77 77. The arrangement is such, as shown in Fig. 8, thatin the normal positions of the parts the pawls 74 75 will be in engagement with the edges of teeth 73. Now when magnet 39 attracts its armature 39 it will move the upper end of lever-78 outwardly or in the direction of the arrow in Fig. 8, whereupon. pawl 74 will act to turn wheel 73 and drum 70 one step, which is equivalent to a distance moved by half of a tooth 73, during which movement pawl 75 will be drawn into engagement with the edge of a new tooth 73, these movements of pawls 74 75 being simultaneously in the same direction, caused by the links 77 77 drawing arms 74 75 outwardly. As soon as magnet 39 is denergized the spring 79 will draw lever 78 in the reverse direction, whereupon links 77 77 will push arms 74 75 rearwardly, (or to the right in Fig. 3,) whereupon pawl 75 will push upon the tooth 73, with which it is in engagement, and thereby turn wheel 73 and drum 70 a distance equal to halfa tooth 73, while at the same time pawl 74 will be moved into engagement with a new tooth 73. The movement thus imparted to wheel 73 by the independent action of pawls 74 75 is equal to the length of a tooth 73, so that a complete forward-and-back stroke stop at the proper point, 1

of lever 78 by the combined action of magnet 39 and spring 79 drum 70 will be given one complete movement necessary to move contacts 45 3755 32 42 together a proper distance. In order that the pawls 74 75 will not cause wheel 73 to overthrow, but will bring it to a provide abuttneuts 74 75, which are adapted to respectively engage the pawls 74 75 when they have been moved by lever 78 the proper distance, and the arrangement is such that the pawl will be jammed between its abutment 74 or 75 and the corresponding tooth 73 of wheel 73 with which it may be in engagement.

The action of the foregoing devices for operating drum 70 may be explained in connection with the selecting, calling, and restoring circuits, heretofore described with relation to Figs. 1 and l, as follows: The relative positions of contacts 45, 37, 55, 32, and 42, comprising a set of contacts, are illustrated in diagram in Figs- 1 and 1, and the same are clearly shown ip Fig. 7 with relation to the respective contacts 46 44 36 35 54 56 31 31 41 43, and the drums 70 are shown in their normal positions. Now when a subscriber first turns the handle 4 of his circuit-controlling wheel 4 switch 9 as it encounters plug 13, that has been placed in an aperture 11, corresponding tothesubscriber desired,ismoved into engagement with contact 10 to close the subscriber-selecting circuit, and thereupon as wheel 4 is moved back toward its home point by the action of spring the first tooth of said wheel that engages the rocker-arm will close the circuit at 16 16, thus sending an impulse to magnet 34 at the first station on the system, as A, which will close the local circuitfor the correspondingmagnet 39. Magnet 39 now attracts its armature 39, which moves lever 78, whereupon pawl 74 will turn drum a distance equal to half of a tooth 73, whereupon contact 45 will be brought into engagement with contacts 46 44 to close the circuit for producing a call, contact 42 will be moved away from contacts 41 43 to break the normal restoring-circuit, contact 32 will be moved a distance, but will still remain in engagement with cont-acts 31 31 to hold the ground-circuit to 30, and contacts 37 and 55 will be moved a distance, but not yet into engagement with their respective contacts 35 36 and 54 56. Now if a call is to be sent to this station (the first station on the circuit) the long tooth 4 of wheel 4 will hold the circuit closed to ground 30 and projection 23 will operate rocker-arm 66 to close the callproducing circuit at 15 15, whereupon current traversing contacts 44 45 46 to ground 48 will cause magnet 49 to close the local circuit forthesignalinginstrument50. Acontinued movement of wheel 4 causes rocker-arm 66 to move off projection 23, thus breaking the callproducing circuit, and immediately thereafterrocker-arin 65 will move 0% tooth 4*, thus breaking the subscriber-selecting circuit.

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close the local circuit of magnet 39.

to engage contacts 54 56 and to cause contact 32 to leave contacts 31 31 to break the operating-circuit through magnet 34, contact 42 not yet being drawn into engagement withcontacts 41 43. Projection 23 will now reach rocker-arm 66 and again close the circuit through 15 whereupon current will trav erse line 17 toward the right in Figs. 1, 1 to line 17, and thence through all the intervening stations to the called station on the circuit A, whereupon the circuit will find ground from 17 through 53, 54, 55, 56, 57, 33, 34, to ground 30, thus causing magnet 34 to again 39 now attracts its armature 39 and moves lever 78 outwardly, thus again turning drum 70 the distance of half a tooth 73 whereupon contact 37 will move from contacts 35 36 to break the sections of line 17, and immediately thereafter contact 55 will move from contacts 54 56 to break the restoring-circuit, thus causing magnet 39 to become denergized, whereupon spring 79 will draw lever 78 to turn drum 70 the distance of half a tooth 73, thus restoring the set of contacts 45 37 55 32 42, which have been under consideration, to their normal positions and wheel 4 will have arrived at the home point, thus causing rocker-arm 66 to move off projection 23*. t.

The foregoing show how the first station on the system may be selected-and called and the circuits restored; but if it had been desired to reach a station beyond the first station A on the system the drums 70 would have been operated to connect the sections 17 17 of line 17 through the station A and throughout the stations that intervene between station A and the station to be called. For instance, let it be supposed that the subscriber at station B desires to call the subscriber at station D, (station No. 4 on the system.) The calling subscriber first places his plug 13 in the aperture 11, corresponding to station D, which would be at aperturenumbered 4 in ring 12. (SeeFig. 4.) Hethenturnshishandle4until his switch 9 strikes plug 13, throwing 9 into engagement with 10 and breaking engagement of switch with 21, four teeth on wheel 4 having passed into position under their rocker-arm 65. It will be understood that these rocker-arms cause no circuit to be completed until the plug has been reached and switches 9 and 20, have their positions changed thereby. Wheel 4 now starts to move toward the home point, and the first tooth 4 thereof closes the selecting-circuit at 16 16 by means of the rocker-arm 65, whereupon an impulse will be sent to ground through contacts 31 Magnet- 32 31" in the first station on the system A to cause the local circuit controlled by magnet 34 to close through the magnet 39, whereupon the corresponding drum 70 will be moved to change the positions of the contacts thereon relatively to their respective contacts connected with their various circuits. This tooth 4 will next release rocker-arm 65,"wheren'pon the circuit at 16 16 will be broken to allow spring 79 to move the corresponding drum 70 another step, as before explained, whereupon contact 32 will he moved out of engagement with contacts 31 31 thus breakingmagnet 34 and ground from the operating-circuit, and contact 37 will be drawn into engagement with contacts 36, whereby two sections of line 17 will be connected together in the station under consideration, contact will be moved away from contacts 44 46, contact will be moved into engagement with contacts 54 56, and contacts 32 42 will be wholly out of engagement with their respective contacts 31 31 and 41 43. wheel 4 will engage rocker-arm 65, thus sending another impulse from the selecting-circuit to ground 30 at the second station on the system B, performing the same operations on drum 7O thereat, principally to connect the two sections of line 17 at 35 36 37. The following tooth 4 on wheel 4 will cause the same operations to occur in the third station on the system C, likewise connecting two sections of line 17 together thereat, a through-line to ground 30 at the fourth station on the system thus being established through the three stations A B G. The wide tooth 4 at the calling-station will now arrive in engagement with rocker-arm 65, thus sending a long impulse direct to ground 30 through magnet 34 at the selected station, while at about the same time projection 23 will engage rockerarm 66 to close the calling-circuit at 15 15. The first efiect of the impulse sent through the selecting-circuit so established by the "influence of long tooth 4 is to cause magnet 39 (through the closing of its local circuit at 34 38) to cause drum 70 at the sejection 23 and tooth 4 now causes rocker-.

arm 66 to move from projection 23 into space 23, thus breaking the call-producing circuit, and immediately thereafter rocker-arm moves from tooth 4*, thereby breaking the selecting circuit, whereupon spring 79 will move lever 78 so as to give drum in the selected station the proper forward movement, during which time contacts 37 55 are The next tooth 4 on brought into engagement with their respective contacts 35 36 and 54 56, ( contacts 32 and 45 having previously been moved out of engagement with their respective contacts in the selected station, as before explained.) A continued movement of wheel 4 now causes projection 23 to move rocker-arm 66 to close the corresponding circuit at 15, whereupon the restoring-circuit will be established and will act as follows: from grounds 2 and 2 through batteries 3 and 3 and line 1 to the selecting-station B, thence to conductor 7 thereat, thence through contacts 6 and 5, con ductor 8, switch 9, contact 10, wheel 4, frame 4 conductor 14, contact 15 to 15 conductor 15 to line 17, thence along line 17 to station 0 through conductor 18 thereat, thence through 6", 5, 2t, 21, 20, 19, 5, 6 and conductor 18 to line 17, thence to through the corresponding parts in station D to part 17 of the line, thence through portion 17 thereof (at D) to 53, 54, 55, 56, 57, and 33 through 34 to ground. The local circuit of magnet 39 is now closed, whereupon said magnet moves drum 70 a proper distance, disconnecting contact 37 from contacts 35 36 and thereafterdisconnecting cont-act 55 from contacts 54 56, thus deenergizing magnet 39, allowing spring 79 to move drum 70 to bring the corresponding contacts carried thereby to their home points, thereupon bringing contact 42 into engagement with contacts 41 43, thus reestablishing the circuit through line 17 in the selected station. Projection 23 still being in engagement with rocker-arm 66 causes the current to continue to How along line 17 to station C, performing the same operations thereat just described with relation to station D, and so on through all the stations in which instruments have been operated in selectingstation D, whereby all the circuits in all the stations that have been operated will be restored to their normal positions. Projection 23 will now move from rocker-arm 66 to disengage contacts 15 15, and all the parts throughout the system will be in their normal positions.

From the foregoing explanations it will be understood that the drums at 70 are always moved forwardly in one direction, and as there are a number of sets of contacts 45 37 32 42 thereon one of these sets is utilized in each station that is operated in reaching the desired subscriber, the next set being utilized the next time a subscriber is desired, and so continuously. Furthermore, it will be understood that thedrum is given foursteps each equal to half the length of a tooth 73- that is to say, the first step is effected by the current in magnet 39, which closes the calling-circuit at 45 and breaks the restoring-circuit at 42. The next step is caused by spring 79, which breaks the calling-circuit so established and closes the circuit through 37 and 55 and breaks the circuit through 32. The

next step is caused by magnet 39, which breaks the circuit through 3755, and the next step is caused by spring 79, which restores the circuit through 32 42, leaving the drum in its normal condition.

Having explained how one subscriber may select and call another and then return the operated parts to zero, it remains to be described how the calling and called subscribers can be placed in telephonic communication. One of the principal features of the invention is that a large number of subscribers can be accommodated on acom parativelysmall number of line wires or conductors, and another feature is that their telephone instruments may be connected in closed metallic circuits. For these purposes I provide a number of main conductors or wires SO" 81 81 S2 S2, and these conductors are used in pairs, as 80 and 80, 81 and 81.", 82 and 82. There are a considerably less number of pairs of such wires than there are stations on a systemfor instance, a number of pairs of wires about equivalent to the greatest number of subscribers that would be telephoning at one time-say five pairs of such wires for one hundred subscribers. I have shown in Figs. 1 and 1 three pairs of wires for the telephonecircuit and four stations, this small number of stations being for convenience of illustration. In each station on the system each conductor 60 80 81 81 82 82 is connected with a contact, which contacts are separated or insulated from each other. In each station are contacts 83 S4 83 84 85, one for each of the telephone-conductors. The contact 83 is shown connected with main wire 80 by a conductor (1, 83 with main wire 80 by a conductor e, 84 with main Wire 81 by a conductorf, 84 with main wire 81 by a conductor g, 85 with main wire 82 by a conductor h, and s5 with main wire 82 by a conductor 1', the same arrangement being made in each station, and so on in each station for as many pairs of such telephone-conductors as there are on the system. Thus when contacts 83 83 are electrically connected through the device the circuit will be from 80, through d, 83, to S3 and e, to 80, and similarly for the other corresponding conductors and contacts.

86 is a contact or metal plate placed near and parallel to contacts 83 84 85", but insulated or separated therefrom.

A cylinder or drum 124 is provided carrying suitable plates or contacts. The drum has two movementsnamely, a rotarymovement, effected by spring-actuated mechanism,

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and a longitudinal movement-2'. e., a movement to the right caused by the armature 123 of magnet 122 and to the left by means caused to operate by the hanging of the receiving-telephone on its hook, the same action reversing the rotary motion and returning all parts to normal position, as hereinafter specifically explained. The plates or contacts carried by the drum are adapted to be engaged by suitable spring-contacts. In the normal position of the drum 124, as shown in Fig. 1, at station A a long contact 114 is in engagement with spring- contacts 113 and 115, abroad contact 132 is in engagement with spring- contacts 131 and 133, a contact 88 is in engagement with spring- contacts 119 and 88, a contact 104 is out of engagement with contacts 103, 105, and 106, and a contact 138 is out of engagement with 137'and 139.

Movable with the drum 124, butadapted to be arrested in its progress, is an arm 94, carrying and in electrical engagement with a contact 95, adapted to engage contacts 83' 84 85, &c., and insulated contacts96 and 97 in electrical connect-ion with each other, contact 96 being adapted to engage contacts 83 84 85, &c., and the contact 97 being adapted to engage contact 86. Fixed on thearm 94 and moving with it'is-a toothed wheel 98. A magnet 101 has an armature 100, provided with a detent-point 99, adapted to engage teeth 98 on said wheel and to arrest the prog ress of the. arm. The arrangement is such that when arm 94 is stopped by said idetent the drum 124 is not arrested, but moves to its destined position. -When a subscriber removes his receiver 91 from its hook 144, arm 94 moves over the contacts 83 84 85, &;c., and the drum 124' rotates. This rotation brings plate or contact 104 in engagement with contacts 103 and 105. When the drum has reached its final position, plate or contact 138 will be in engagement with spring contacts 137 and 139, and plate or contact 104 will then be out of engagement with 103 and 105, part 88 of plate or contact 88 will be in engagement with spring-contact 88 only, contact-plate 132 will be out of engagement with spring- contacts 131 and 133, and plate 114 will be still in engagement with 113 and 115. If now druin 124 be thrown to the right (in the drawings) by the action of armature 123 of magnet 122, the relations of the contacts on the drum'and the spring-contacts will'be as follows: 138 wille'ngage 137 only, 104 will be out of engagement with 103 and 105, part 88 of 88 will be 'in'engagement with contacts 88 and 89, contact 132 will still be out of engagement with its spring-contacts, contact 114 will engage contacts 115 and 135. (This is the normal position of drum 124 and its contacts when circuits are completed for conversation.) Drum 124 is also adapted to be moved to the right by armature 123 of magnet 122 before the receiver is removed from its hook and the drum rotated, in which case the relative positions of contacts on the drum and the spring-contactswill be as follows: Contact 88 will be in engagement with 88 only, contact 132 will be in engagement with 131 and 133, and 114'will be in engagement with 115 and 135.

tated these same positions will be preserved, contact 104 moving into engagement with contact- springs 103 and 106. 'When the drum has rotated its full distance, the positions will be the'same as described above for the purpose of conversation. 'From contact 86 extends a conductor 87, that leads to contact Now when drum 124 is r0-.

88. Contact 89is connected by a wire 90 with one side of telephone-receiver 91. From the other side of this receiverextends a conductor 92, that includes the secondary of an induction-coil 93 and leads to the arm 94.

One of the purposes of my invention is to enable contacts 95 96 97 in each stationto select an idle or unemployed pairof main conductors automatically, and in connection therewith I have arranged the system so that after the appropriate parts in a calling-subscribers station have selecteda pairof idle main conductors the corresponding parts in a called station will act to select the same pair of wires to place the telephone instruments in a calling and a called station in a closed metallic circuit over said selected conductors. Magnet 101 is located on a normally open local circuit organized as follows: From one terminal of magnet 101 extends a conductor 102, that leads to the contact 103, which is normally out of engagement with but adapted to be engaged by the contact 104.

The contact 104 in the calling station is' adapted to engage the contactl105, while in the called station contact 104 is adapted to engage contact106, as hereinafter explained. The contact 105 is connected withaconductor 107, that leads to a contact 108, which is contact operated thereby.) The armature 109 I normally engagedby an armature 109, (or a 1 (or the contact operated thereby) is connected bya conductor 110, that leads toconducto'r 27 on one side of battery 28. From conductor 27, on the other side of battery 28,.a conductorlll IQO leads to the terminal of magnet 101 opposite to conductor 102. Magnet 122 is operated in two ways. In one case ,when magnet 49 3's operated in a called station to ring the corresponding bell the current from the battery 28 passes not only throughthe bell 50, but also through magnet 122, as follows: From one side of magnet 122 a conductor 127 leads to wire 111, the circuit leading thence to wire 27 and to one side of battery 28, thence from other side of battery 28 over wires 402 52, armature 49*, contact 51, wires 52 and 126,'to wire 125, and back to magnet 122. A circuit IIO for magnet 122 is alsoformed when drum-124 has been rotated before being moved lengthwise, as follows: from one side of magnet 122, to wire 125, to spring-contact139, thence by plate 138, ,(as drum has been rotated,) to

spring contact 137, wire 128, contactH129, 7 (adapted to be engaged by armature 109 of magnet 117,) through armature 109, wire 110,

wire 27, through battery28, to Wire 111, thence by 'wire 127, back to magnet 122. Whena calling-stations arm 94 automatically seeks an unemployed circuit in order to secure it are open throughout' that is, where no conforitself, it seeks for a pair of wireswhich pass over the contacts corresponding to the busy wires, as 81 81, without being arrested. The circuits which enable this passing of the arm 94 are as follows: Suppose an attendant at any station, as Afdesires to communicate with some station, as C. Having called station 0 over the calling-circuit in the manner previously described, he removes his receiving-telephone from its hook on arm 144. This starts the rotation of his drum 124 and also starts the movement of arm 94. We will now suppose that wires and 80 are in use, and therefore connected together through some userstelephonaas previouslydescribed. \Vhen, therefore, arm 94 reaches the contacts 83 and 83, representing wires 80 and 80, a circuit is instantly formed as follows: from grounds 2 and 2, through batteries 3 3, over wire 1, to wire 112, thence to spring-contact 113, contacts 114 115, wire 116, to magnet 117, thence by wire 118, over wire 92, arm 94, contact 95, contact 83, wire d, to main wire 80, (all at the calling station,) over 80 and through the telephones of subscribers using the wires to wire 80, back over wire 80, to wire 6, contact 83, contacts 97 86, wire 87, to spring-contact 88, contact 88, springcontact 119, thence by wire 120, to ground 121. This circuit being thus closed through magnet 117 causes it to attract its armature 109. This breaks the local circuit of magnet 101, as before described, at 109 108. Magnet 101 cannot therefore attract its armature 100, and thereby arrest arm 94. The arm 94 will therefore pass on to the next pair of contacts 84 84, and as the wires connected to these contacts are also busy the circuit for 117 will still be unbroken (as contacts 95 and 96 are arranged (see Fig. 9) to make contact with the next pair of contacts before breaking from the one they are on, thus contact 95 engages 84 just before breaking from 83 and 96 engages 84 just before breaking from 83) and arm 94, continuing its movement, passes on to contacts 85 and 85. If the wires connected with these latter contacts are not in use, there will be no connection between 82 and 82, so that when arm 94 passes on to these contacts the circuit through magnet 117 will in consequence be broken. Magnet 117 thereupon releases its armature 109, causing the local circuit through magnet 101 to be closed at 109 and 108, as follows: from armature 109, over wire 110, wire 27,inc1uding battery 28, wire 111, magnet 101, wire 102, contacts 103 104 105, wire 107, and contact 108, back to armature 109. Magnet 101 thereupon attracts its armature 100, causing detent 99 to be thrown into engagement with a tooth 98 of wheel 98, thus stopping the progress of arm 94 over contacts 85 85, which represent connection to the first pair of idle wires, and drum 124 continues its rotation to its destination. It will be noticed that battery from wire 1 is left on the selected line 82 through magnet 117, also that the ground 121 is removed from wire 82. The position of .92, to arm 94, contact 95, contact 85, wire it, to

wire 82. The ground 121 is broken from 82 as follows: from 82 to wire 2', contact 85, contacts 96 97 86, and wire 87, to contact 88, and as contact 119 is not connected through part 88 of contact 88 to contact 88 the circuit over wire 120 to ground 121 is therefore broken between 88 and 119.

Having explained the manner in which the arm 94 at the calling-station selects and makes connection with a pair of idle wires, I will now explain the manner in which the arm 94 at the called station makes connection with the particular wires selected by the callingstation. It must be remembered that the calling-stat-ion has left a battery from wire 1 upon line 82. Now in the called station when the hell or signaling instrument was operated the local circuit of magnet 122 was completed in manner already described through the action of armature 49 of magnet 49 energizing magnet 122. The drum 124 was moved to the right, and a circuit was formed for magnet 117 in the called station when the receiver was removed from the hook, as follows: The removing of receiver 91 from its hook permitted the drum to rotate, and arm 94 moved over the contacts 83 83 84 84,&c. Arm 94 cannot stop until it makes such connections as will complete the circuit through magnet 117 to ground 121 for the battery-currentput on wire 82 at the calling-station. The called station cannot now select an idle pair of wires, as the contact 114 has moved from under 113, thus cutting off battery connection-through 112 to line 1 at that station. The contact 104 is now under 103 106, (the moment the drum begins to revolve,) and contact 119 is out of engagement with 88. The circuit from the charged line 82 will new extend as follows: from wire it, to contact 85, contact 95, (when arm 94 has reached said contact,) arm 94, wire 92, wire 118, magnet 117, wire 116, contacts 115 114, (as 114 is out of engagement with 113 and in engagementwith 115 and 135,) contact 135, wire 134, to contact 133, contact 132, contact 131, and wire 130,to ground 121. This completes the circuit of the battery put on to wire 82 at the calling-station through magnets 117 in both the stations. In the called station magnet 117 attracts its armatu re 109 and completes the local circuit through magnet 101 at 109 and 129, the local circuit being as follows: from armature 109, to wire 110, wire 27, through battery 28, wire 111, magnet 101, wire 102, to contact 103, (contact 104 being new under 103 106,) contact 104, 106, wire 128, and contact 129 to armature 109. Magnet 101 thereupon attracts its armature 100, causing detent 99 to engage a tooth 98 of wheel 98, thus arresting the progress of arm 94 over contacts 85 85, securing connection to the wires desired, (82 82.) In

the calling-station magnet 117 also attracts its armature 109, completing the local circuit for magnet 122 in that station as follows: armature 109, wire 110, wire 27, through battery28, wire 111, wire 127, magnet 122, wire 125, spring-contact 139, (drum 124 having rotated its full distance and brought contact 138 under contacts 137 and 139,) contact 138,: contact 137, wire 136, to wire 128, and by contact 129 back to armature 109. Magnet 122 (at the calling-station) thereupon attracts its armature 123, moving drum 124 at that sta:v tion to the right and breaking the local cir-' cuitof magnet122at139138. Thebattery-cirs cuit leading from wire 1 is now broken as fol-Q lows: from wire 1,to wire 112, and contact 113, and as contact 114has been moved away from contact 113 and is now under 115 135, said battery-circuit will be broken at 113 114. Part 88 of contact 88 now completes con nection between 88 and 89.

For the purpose of illustrating the circuit just described I have-shown in the drawings Figs. 1, 1 the stations 13 and D as in connection for conversation. We must suppose station E to have called station D and that all necessary movements and connections have been made as described. The positions of the difierent parts and the connections formed will be as follows: The arm 94 at both stations has been arrested on the first already engaged by other stations,) represented by contacts 84 and 84*. From contact 84 in station B the circuit extends over wire 81 to contact 84 in station D, thence by contact 95 on arm 94 at D over arm 94 and wire 92, through the secondary ofinduction coil 93 to receiving-telephone 91, thence by wire 90 to contact 89, part 88" of contact 88, contact 88, wire 87, contact 86 to insulated contact 97, thence to 96 84 over wire 9 to wire 81*, over the latter to wire g in station E, thence to contacts 84 96 97 86 87 88 88 89, wire 90, receiving-telephone 91, wire 92, through secondary of induction-coil 93, arm 94, and contact 95 back to contact 84 in sta tion B. Receiver 91 having been removed from the hook of arm 144 at both stations, arms 144 will have engaged contacts 140 and have thus completed the local circuits through transmitters as follows: From transmitter 142 extends a conductor 143, which leads to the primary of induction-coil 93 over conductor 143 conductor 27, to one side of battery 28, conductor 27, from other side of battery 28, wire111 111, arm 144, contact 140, and wire 141, back to transmitter 142. This circuit is the same at both stations. The

arrangement of the parts is such that when receiver 91 is hung upon hook 144 arm 94 will be moved clear of contacts 83 83, &c., as in stations A and C, and drum 124 willbe moved back to zero.

The mechanism I have devised for causing the various and independent movements of on shaft 145.

arm 94 and drum 124 is clearly illustrated in Figs. 2, 3, 9, 10, 11, 12 and is as follows: The drum of cylinder 124 is loosely mounted on a shaft 145, so it can slide thereon, and the shaft 145 is joufrnaled in suitable bearings in a frame 146. The drum 124 has an aperture to receive a pin 147, so that it can freely slide lengthwise of said pin and shaft 145, and said pin is carried by an arm or disk 147, secured to shaft 145 and which serves as an abutment for drum 124 to stop the latter in the proper place when it is moved by magnet 122. Pin 147 causes drum 124 to turn with shaft 145. The armature 123 of magnet 122 is connected with anarm 123, that acts to push drum 124. (See Fig. 11.) As shown clearly in Figs. 9, 10, and 11, arm 123 is carried by a rock-shaft 123", jonrnaled in bearings on frame 146, and armature 123 is carried by arm 123 (See Fig. 11.) Drum 124 is moved back to the normal position by a pin 148, carried by drum 124, acting against a springarm 149, which has a curved part 149 (see Fig. 3) so arranged as to allow pin 148 to travel with drum 124 along shaft 145 (by the action of arm 123) and to move forwardly or over with said drum; but when the drum is turned back on 'its axis the curve of said spring 149 will act on said pin to move the drum back along shaft 145 to the normal position. The arm 94 is-loosely hung on shaft 145, and the toothed wheel or disk 98 is also loose on said shaft, but rigidly connected with said arm. (See Fig. 11.)'- The shaft 145 carries a pin 150, shown attached to an arm 144, and to enable said shaft to be given a maximum motion with a minimum movement of arm 144 I have shown said shaft and said arm connected by suitable gearing. Furthermore, in order to move arm 94 to enable it to select the proper pair of main teleph0ne-con-.

ductors and to cause arm 144 to close the local circuit for the transmitter 142 I have provided a spring 151 to operate the before-mentioned gearing. (See Fig. 11.) Said gearing is arranged as follows: Arm 144 is secured to a shaft 152, that is journaled in frame 146, and said shaft carries a gear-wheel 153, that meshes with a pinion154, carried by an arbor 154, journaled in frame 146. Pinion 154 meshes with a pinion or gear 155, secured on shaft 145. .(See Figs. 9, 10, 11.) To the pin ion or gear 155 is secured an arm 156, which normally rests beneath a pin 157, that is attached to a ratchet-wheel 158, loosely mounted Ratchet-wheel 158 is in engagement with a spring-acting pawl 159, that is carried by a gear-wheel 160, loosely mounted on shaft 145. Spring 151 is connected with frame 146 and is also connected-with wheel 160, being shown so connected through the-

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