US779811A - Selective party-line telephone system. - Google Patents

Description

PATENTED JAN. 10, 1905.

A. J. SPRINGIBORN. SELECTIVE PARTY LINE TELEPHONE SYSTEM.

APPLICATION FILED APR.3,1903.

4 SHEETS-SHBBT 1 A TTORNE Y.

No 779,811. PATENTED JAN. 10, 1905.

x A. J. SPEINGBORN.

SELECTIVE PAR-TY LINE TELEPHONE SYSTEM.

APIiLIGATION FILED APR. a, 1903.

4 SHEETS-SHEET 2.

[35 ll 11f "i M 415 WITNESSES: c I S r 16. or w/NVENTOR.

No. 779,811. PATENTED JAN. 10, 1905. A. J. SPRINGBORN.

SELECTIVE PARTY LINE TELEPHONE SYSTEM.

APPLICATION FILED APR. s, 1903.

4 SHEETS-SHEET 4.

WITNESSES. WW CDZ ATTORNEY UNIT D STATES Patented January 10, 1905.

PAT NT OFFICE.

SELECTIVE PARTY-LINE TELEPHONE SYSTEM.

SPECIFICATION forming part of Letters Patent No. 779,811., dated January 10, 1905.

To atZZ whom it may concern/.-

Be it known that I, ALBERT J'. SPRINGBORN, acitizen'of the United States, residing at Cleveland, in the county of Guyahoga and State of Ohio, have invented a new and useful Improvement in Selective Party-Line Telephone Systems, of which the following is a specification.

This invention relates to partyline telephone systems, and is an improvement on the system shown and described in my pending application for patent, Serial No. 64,302, filed June 12, 1901.

The objects of said improvements are to render said system more automatic in its operation and to make the apparatus simpler in its construction and electrical connections. These objects I attain in the system illustrated in the accompanying drawings, in which Figure 1 is a diagrammatic view of two partylines, each being provided with two substations and each extending to the central station, the connections and apparatus in which are shown. Fig. 2 is a diagrammatic view of a party-line which is provided with four telephones or substations in parallel, showing the dials for the selecting devices. Fig. 3 is a view of the clockwork for operating the selecting devices at both the central and substations, the same being taken on line 3 3 of Fig. 4. Fig. 4 is a central sectional view through either dial A or B of Fig. 2, taken on line 4 4 of said figure, but showing the clockwork mechanism of Fig. 3 in plan with the same released by its electromagnet. Fig. 5 is a detail view of a portion of the apparatus shown in Fig. 4, showing the parts in a different position. Fig. 6 is a perspective view of a selector-key and a portion of the spring-connecting finger that cooperates with it. Fig. 7 is a view taken on the line 7 7 oi'Fig. 5, showing the beveled head on the dial-hand keys. Fig. 8 is an enlarged diagrammatic view of the connections at the substations. Figs. 9, 9, and 10 are perspective views of portions of the substation selecting apparatus, showing the locking devices for the keys and telephone-hook. Fig. 11 is adetail view of aportion of the rod leading to the telephone-hook, showing the expansible and compressible portion of the same. Fig.11 is a detail view of the Zero-key. Fig.

12 is an enlarged front view of the central selecting device and its electrical connections. Fig. 13 is a side view of the selecting device shown in Fig. 12. Fig. 14 is asectional view of the same, taken on line 14 14 of Fig. 12. Figs. 15, 16, and 17 are detail views of portions of the central selecting apparatus, and Fig. 18 is a general View of a telephone having a selecting device attached thereto.

In the telephone system herein described I have sought to make the operation entirely automatic and to relieve the operator at the central station of as much labor as possible.

In the drawings, in which similar reference characters designate corresponding parts throughout the several views, 1 and 2 represent the main wires of party-line telephones, one set of said wires in Fig. 1 being connected with substations A and B and another set being connected with substations C and D. All of said sets of wires lead to a switchboard 3 at the central station, which board is shown divided, so as to more clearly illustrate the electrical connections.

In each of the telephones shown, 4 designates the hook, upon which the receiver 5 is adapted to hang in the usual manner. 6 is the transmitter, the circuit from which leads through the primary of the induction-coil 7. 8 designates the call-bell, which is preferably of the ordinary make-and-break-circuit form. At the central station, 9 represents the ordinary jacks ot' the switchboard, and 10 the plugs for the same.

This system depends for its operation upon a series of selecting devices, one for each substation, and also upon one or more of a somewhat different form of selecting device at the central station. In order for these devices to always select the particular party with whom connection is desired to the exclusion of all other parties on the line, it is necessary for them to move synchronously. To accomplish this result, I provide each selecting device with clockwork mechanism, which is shown in detail in Figs. 3 and 4, the said clockwork being identical in both the central and sub stations. While this mechanism may be of any suitable character, as shown in the above mentioned figures, 1t consists oi a drum-arbor 11 and drum 12, within which is coiled the spring 13. As will be understood, one end of this spring is fastened to the drum, while the other end is attached to the drumarbor. Secured to the drum is a large pinion 14:, which meshes with and drives a small pinion 15, which is secured to the central shaft 16. Also secured to the central shaftis a large pinion 17, which meshes with a small pinion 18 on the shaft 19, which carries a governing-fan 20. Instead of a fan a suitable form of escapement mechanism may be employed, if desired. Projecting from the frame of the clockwork mechanism are studs 21 and 22, upon which are journaled gearwheels 23 and 24, which are geared toa small pinion 25 upon the drum-arbor. Also journaled upon the stud 22 is a lever 26, which carries a pawl 27 for engaging with the teeth of the gear-wl1eel 24 to drive the same when the lever is moved forward against the tension of its spring 28. For preventing the backward rotation of the gear-wheel 24 I provide a detent-pawl 29, which is secured to a stationary part of the framework and engages with the top teeth of the gear-wheel. From this description it will be understood that when the lever 26 is moved forwardly it will turn the gear-wheel 2a and through the train of gearing will turn the drum-arbor to wind the spring 13. Furthermore, when the central shaft is permitted to turn by releasing mechanism presently described the train of gearing extending from the drum-arbor to the governing-fan will be rotated. This releasing mechanism consists of a notched disk 30, which is secured to the central shaft, in the notches of which the beveled end of a lever 31 is normally pressed by means of a spring 32. hen this lever is moved so as to disengage its beveled end from the notches, the clockwork mechanism is free to operate.

It will be seen that it is necessary to release all of the mechanisms on the various substations on a line at the same instant, and for this purpose I provide each of the selecting devices with an electromagnet 33, which is preferably mounted between the ends of the levers 26 and 31, so that when a current is passed about the same these levers will be drawn toward each other to release the clockwork and also to wind up the spring. The gears for winding the spring and those for driving the central shaft are so proportioned that the spring is always kept under driving tension.

The frame for the clockwork mechanism is secured to the rear side of an inner dial-plate 34, and the central shaft projects through the same and also through the center of the outer dial-plate 35, the frame and the inner dial being secured together by the posts 36 and the dials being connected by similar posts 37, and the outer rim 38 of the selecting device. About midway between the outer and inner dials and parallel therewith is a disk 39, of insulating material, to the inner surface of which are secured conducting-rings 40, that are placed concentric with themselves and with the shaft 16. Attached to the back side of the disk 89 and radiating from points near the central shaft are spring arms 41. These arms extend through slots 12 in the outer rim 38. and just beyond said rim they are bent forwardly at 43, so as to bring their free ends almost flush with the outer dial 35, when the arms are permitted to assume their normal position, as shown in Fig. 4. Secured to the front sides of these spring-arms are contact-springs H, which are adapted to bridge across and shortcircuit the conducting-rings 40 when the arms are in normal position, but which are lifted outof contact when the arms are depressed, as shown in Fig. 5. The rings 10 and the contact-springs 1 i form under conditions presently set forth parts of an electric circuit through which a current flows to set all the selecting devices at the substations to the desired point for unlocking the telephone at the particular substation desired, while all the other telephones are maintained in locked condition. For depressing the spring-arms and breaking the contact at the rings 40. I provide the central shaft 16 with a dial-hand 45, which turns about over the outer dial and terminates in an antifriction-roller4:6. This roller moves in an orbit over the free ends of the springarms ll and depresses them, so as to break the contact between the springs 41 i and rings 1O, as shown in Fig. 5. When the contact is thus broken at the substation that is calling and that controls for the time being the party-line, all the selecting devices stop with the dial-hands pointing toward the same indicating-letter. By reference to Fig. 2 it will be seen that while all the dials have the same arrangement of letters'there is a different arrangement of keys 47, which keys are adapted, when depressed by the dial-hand, as hereinafter described, to close a bell-circuit for sounding a call-bell 8. There is one of these keys at? for each of the spring-arms 4:1, and they are arranged in pairs, so that when the dial-hand moves around to break the contact at the rings 40 in one station it will simultaneously depress a key 4L7 and close the bell-circuit at that station. As seen in Fig. 2, but one dial has a key atA, but one has a key at B, but one has a key at (J, and but one has a key at D, so that normally when one telephone on a line is in use no other telephone on that line will be called. One of the keys 47 is shown in enlarged views in Figs. 4, 5, 7, and 9, from which it will be seen that it is provided with an enlarged head that projects beyond the face of the dial 35 and that is beveled so that a roller 48, that iscarried by the dial-hand, may more easily depress it. The keys are normally pressed outwardly by springs 19, that are coiled about their shanks and are preferably guided at their inner ends cuit.

in bosses 50, that project from the outer face of the disks 39. Mounted on said disks on the opposite side from the conducting-rings 40 and preferably concentric with the shaft 16 are a second pair of conducting-rings or segments of rings 51, said rings being clearly shown in Fig. 8. The bosses and keys 47 are placed between these segmental rings. Opposite each of the said bosses spring-contacts 52 are connected with the segmental rings and are passed through the disks 39 and then bent down into the bores through the bosses. When the keys 47 are in their outer position, as shown in Fig. 4, the contacts-are separated; but when they are pushed in, as shown in Fig. 5, they will be forced between the contacts and will complete the bell-circuit. As will hereinafter more clearly appear, a plurality of separate contact-points with independent conducting-wires may be employed instead of the conducting-rings 40 and the segmental conducting-rings 51. From this description it will be clear that when the dialhand depresses a spring-arm 41 it will break the contact at rings 40 and at substantially the same instant will close the contacts at the corresponding key 47.

In the system described in my former application above referred to the party who should take down the receiver and ask the centralop- 'erator for connections with another party was obliged to give his own letter and wait for central to place his own phone in the talking-cir- For the purpose of relieving both the party calling and the central operator of this trouble I have the spring-arms 41 at the single letters A, B, C, and D in such position that the springs 44 are normally in contact with the conductingrings, as seen in Fig. 10. w The said rings are in a circuit that is controlled by the telephone-hook, and when the receiver is up the circuit is broken; but as soon as A, for example, takes down his receiver to call he completes the circuit and a local battery starts all the telephone-selectors on his line, which selectors continue to operate until As dial-hand reaches A on hisdial, when the spring-arm 41 is depressed and the circuit broken. Each party calling therefore places his own line in the proper condition, and thus relieves the central operator of that operation. Vhen As dial-hand stopped at A, it depressed the key 47 at that letter, and thus closed the bell-circuit there. This circuit, however, is controlled by the telephone-hook, and when the receiver is down the circuit is broken, so that As bell is not sounded.

It may sometimes happen that two parties on the same line wish to converse. Suppose, for example, that A should want to call D. If he should proceed in the usual way, it is evident that the dial-hands would be stopped at A and that D would not be placed in connection. To provide for such conditions, I

place contact-arms 41 at points on the dials which are designatec AB, AC, AD, &c., as shown in Fig. 2, and arrange radial keys 520 to cooperate with said arms. The resiliency of these arms tends to make them assume the position shown in Fig. 4; but they are normally held back by the keys, as shown in Fig. 5, said figures showing the AB key. As appears from Fig. 6, the forwardly-bent portion 43 of these spring-arms is provided with a slot that has a narrow part 53 and a wide part 54. The keys 520 are provided intermediate their length with enlarged rectangular portions 55, that normally rest in the wide part of the slots in the arms, as shown in Fig. 5, at which time the arms are depressed. The keys are supported partly by the outer rim 38 and partly by the annular flange 56, that surrounds the selecting device, and they are normally held outwardly by springs 57, that are coiled about their shanks. With this description it will be understood that when A wants to talk with B he simply pushes in the AB key a distance sufficient to bring the enlargement out of the wide part 54 of the notch in the spring-arm, when the latter moves forwardly to close the contact with the rings 40. Then when he takes his receiver off the hook the selecting devices start forward and continue untilAs dial-hand depresses the spring-arm and breaks the contact again. When the arm moved forwardly as above described, the shank of the key 520 entered the part 53 of the notch and the en- 'largement 55 prevented the outward movement of the key until the spring-arm was again depressed so as to bring the wide part of the notch opposite the key, when the latter was free to snap outwardly to hold the arm in its depressed position. In moving to the AB key the dial-hand passed and depressed the spring-arm at A. This arm having no key 520 to detain it would, if permitted, spring back as soon as the dial-hand had passed and bridge the contact-rings at A, with the result that the dial-hand will not stop at AB. In order to hold the A spring-arm depressed, I provide a locking-hook 58 (see Fig. 10) with a beveled face that is cammed back as thearm 41 is depressed and that moves forward again as soon as the arm has passed it, the hook engaging with the front of the arm to hold it back. This hook is carried on the end of an arm 59, that is journaled on the central shaft 16, and it is held in its engaging position by means of a coiled spring 60, that is secured at one end to a stationary part of the mechanism'and engages the arm 59 with its free end. Normally thedial-hands all stand at O, which in this case I prefer to place at the left part of the dials. The lines are automatically restored to their Zero positions when the parties who have been talking hang up their receivers. It thus becomes necessary to have a restoring-circuit in each line that is closed when the receiver is hung up and that continues unbroken until the dial-hands reach zero. The particular circuit for accomplishing this result will not be traced until the various mechanisms have been described; but it has one pair of contacts under the receiver-hook and another pair at the zero-key, which key is shown at 61 and is designated 0. The outer conducting-ring 40 is for convenience used for one contact of the latter pair, and the other contact is shown at 62. (See Figs. 4:, 8, and 10.) The zero-key, like the bell-circuit keys 47, is provided with a beveled head, so that it can be easily depressed by the roller 48 on the dial-hand. For a purpose hereinafter made to appear the zero-keys are of a double structure, consisting of an outer sleeve 63 and an inner plunger 64, that extends beyond the sleeve at each of its ends. The outer end carries the beveled head heretofore referred to, and the inner end is provided with a cam 65, that is adapted to engage the arm 59 as the plunger is depressed by the dial-hand to push back the hook 58, and thus release the springarm 41, that may be retained thereby. Intermediate the cam 65 and the head the plunger has a cam 66, that projects through a slot 67 in the sleeve, said cam preferably resting against the outer dial 35 when the plunger is in its outer position. Between the cam 66 and the upper end of the bore in the sleeve is a spring 68, that presses the plunger outwardly except when it is restrained by the dial-hand. The lower end of the sleeve is provided with a plate 69, between which and the dial 35 is a coiled spring 70, that pushes out the sleeve when it is released. Projecting from the inner end of the sleeve 63 is a stud 71, to which is secured a contact-spring 72, that is adapted, when the sleeve and plunger are released, to bridge the contacts i0 and 62 for restoring the selecting devices on the line to zero position. It will be evident that if the sleeve 63 were permitted to spring out on all the telephones on a party-line as soon as the dial-hand moved away from zero position the contacts 4:0 and 62 would be closed on those selecting devices belonging to the telephones with their receivers up, with the result that the return-to-Zero circuit would be fully established in those telephones and the dial-hands could not stop until they had again reached Zero. The sleeves, therefore, are prevented from moving outwardly at the telephones unless the receiverhooks are elevated. This is accomplished by extending a rod 73 from a short arm 7% of the receiver-hook t back to the zero-key to intercept the sleeve and prevent its outward movement. This rod terminates in an angular plate 75, said plate normally extending in front of an angular pin or finger 76 on the sleeve, as shown in Figs. 4c and 10. When the receiver-hook is up, the plate 75 is drawn away from the pin 76, and when the dial-hand moves away from Zero the sleeve and plunger will assume their outward positions, bringing the pin 76 in front of the edge of the plate 75. Then when the receiver is again hung up the plate abuts the angular pin and would prevent the depression of the hook, which is necessary for completing the returnto-zero circuit, were it not for the telescopic structure shown in detail in Fig. 11. The plate 7 5 is attached to a small cylinder 77, in which works a piston-head 78, that is formed on the end of the rod 73. Between the cylinder and the piston-head is a compressible spring 79. This structure permits the hook to be depressed to close the contact-points of the return-to-zero circuit, and when the dial-hand pushes in the ZBIO' key the spring 79 causes the plate 75 to snap in front of the angular pin 76. As the dial hand will be stopped by the releasing-lever 31 the instant the current is broken, so that it will not be able to further depress the sleeve 63, it will be seen that the contact plate 72 will be lifted from the contacts 410 and 62 such an exceedingly short distance that changes of temperature or slight jars would be sufficient to cause trouble. To still further depress the sleeve and separate the contacts, I form the front part of the plate 75 with a cam edge 80, that forces the sleeve inwardly as the plate moves forward under the impulse of the spring 79.

In the operation of any system it is necessary that when the lines are not in use and the dial-hands stand at Zero all the receiverhooks and all the keys 520 be unlocked, and it is also necessary to lock the hooks and keys as soon as the dial-hands move from Zero, after which neither will be unlocked unless the dial-hand stops on a key 47 of some selector, when the hook and keys for that seletor will be released. Of course all keys 520 and receiver-hooks will be released when the dial-hands return to zero. To accomplish these results, I form a head or button 81 on the rods 73 at a point a short distance inside the outer rim 38 when the hooks are down, said rods passing through said rim. I also form similar heads or buttons 82 on the inner ends of the radial keys 520, said heads being in an opening in the rim 38 when the keys are in their outer positions. Mounted to turn about the central shaft and to move in close' proximity to the inner surface of the outer rim is a locking-ring 83, said ring being preferably carried by radial arms 84, that are journaled on the central shaft. Aspring 85, that is coiled about the shaft, has one end secured to a stationary part of the device and has its other end bearing against one of the arms 84 to hold the locking-ring in normal position. (See Fig. 10.) The locking-rings are provided at points opposite the rods 73 and the keys 520 with holes 86, (shown most clearly in Fig. 9,)said holes having narrower slots 87 connected therewith. The holes 86 are of substantially the same size as the heads 81 and 82, and when they are in normal position they are directly opposite said heads, so that the head 81 may pass through the hole, moving outwardly, or the heads 82 may pass through moving inwardly. The cam 66 on the plunger of the Zero-key shifts the ring to this position when it is depressed by the dial-hand, as is shown in Fig. 10, where the cam is seen engaging with one of the arms 84, that carry the ring. When, however, the dial-hand moves away from Zero, the plunger and cam move outwardly and the spring causes the ring to shift, so as to bring the neck 88 (see Fig. 11) of the rod 73 into the narrower slots 87 in the ring and the heads 82 of the keys opposite said slots. This being the position of these parts, it is obvious that the telephone-hook cannot rise or the keys be depressed. By reference to Fig. 9 it will be 'seen that all the bell-circuit keys 47 are provided with a ring-shifting cam89, that pushes back the arms 84 and unlocks the receiver and keys on the telephones. When, therefore, a dial-hand comes to rest on a key 47 and the hook for that telephone is down, the bell will be sounded and the locking-ring shifted so that the hook will be unlocked.

By reference to Fig. 2 it will be clear that if D, for example, is called and the dial-hands all start around for D one of the other parties on the line, as B, seeing the hand moving could take down his receiver. Then when his dialhand reached his key 47 his ring 83 would be shifted and his telephone-hook would fly up and place his telephone in the talking-circuit. Before explaining my means for avoiding this result I will call attention to the fact that the dial-hands are controlled by the electromagnets 33 and that they can move only as said magnets are energized. I therefore operate a second locking-ring by means of these magnets, said ring being mounted to turn just inside the ring 83 and having holes 91 with narrow extensions 92, that normally register with the holes 86 and extensions 87. The ring 90 is supported on arms 93, (see Fig. 9,) that are journaled on the central shaft 16. Secured to one of these arms and to the releasing-lever 31 (see also Fig. 3) is a link or rod 94, said rod connecting the arm and lever rigidly, so that they move together. The leverspring 32 holds the ring with its holes in unlocking position when the magnet is deenergized; but when the latter is energized the inner ring 90 will be shifted to lock the receiver-hooks down and the keys 520 outv It will thus be seen that after the dial-hands move from zero position it is impossible to release any hook or depress any key until the hands come to rest on a key 47, when the currents through the magnets are broken and the ring 90 comes to its unlocking position. The depression of that key 47 also shifts the ring that causes all the dial-hands on that line to be returned to Zero position.

The selecting device at the central station is similar in many respects to those at the substations. It has an outer dial 95. upon which are the letters A, B, C, D, &c., and over the face of which turns the dialhand 96. This dial-hand has a roller 97 corresponding with the roller 46 on the other dial-hands for pressing down the spring-arms 98 opposite the single letters on the dial and the special springarm 99 at the zero position, which in this device is preferably at the lower part of the dial. Precisely the same form of clockwork mechanism is employed as that previously described, so that illustration and description of the same is deemed unnecessary. Mounted on the inner face of the outer dial are a pair of conducting-rings 100, which are bridged under conditions presently set forth by spring contact-plates 101, that correspond with the plates 44, heretofore described. The outer rim 38 is surrounded by one of the flanges 56, and in this rim and flange are guided radial keys 102, which are like the keys520, except they have no head or button 82, there being no locking-rings in this selector. As in the other selecting devices, the spring-arms have a forwardlybent portion in which are the slots for co6pcrating with the squared portion 55 of the keys. The operation of a key 102 releases the corresponding spring-arm 98, which snaps forward and closes the circuit between the conducting-rings 100. The special arm 99 (see Figs. 16 and 17) is provided with a forward projection 103, upon which the roller'97 of the dial-hand 96 rests when it is in its zero position, at which time its spring-plate 101 is out of contact with the conducting-rings. The arm 99 is extended beyond the projection 103, and on its extreme outer end it has a linger 104 pivoted thereto. A flange 105 just inside the finger prevents an inward movement beyond the position shown, while the finger can be readily depressed, as indicated in dotted lines. A spring 106 tends to hold the finger in its inner position.

The central selecting device is in my improved system mounted upon the upper end of a hollow standard 107, that is pivoted to a rod 108, preferably below a table or board 109, through which the standard projects,

and through a slot 110, in which it can swing back and forth, as indicated in dotted lines in Fig. 12. Below the pivot the standard is preferably flattened and is of a shape resem- 83 for that selecting device; but as there is no 1 bling somewhat an inverted cross having the lower depending part 111 and the outstretched arms 112. 113 is a solenoid through which extends a plunger 114, the upper end of which is wedge-shaped. The lower end of the depending part 111 is formed on an arc concentric with the pivot 108, and near each of its outer edges it is provided with notches 115,

' into which the end of the plunger 114 engages when the standard 107 is swung, so that the latter will be temporarily held against return. A spring 114 normally holds the plunger retracted. A pin 116, covered with insulating material, as indicated at 117, projects from the face of the depending part of the standard between fixedly-mounted ducting-springs 118, (see Fig. 5,) said springs returning the standard to and holding it in vertical position when it is released by the plunger. These spring are mounted upon bars 119 and are insulated from one another, the bars being preferably formed of insulating material. They and the rod 108 will also preferably be made of considerable length, so as to accommodate a series of selecting devices arranged in alinement. The construction and connections will be the same in all selecting devices, however, so that such a series is not illustrated.

120 is a stationary arm that is mounted upon the table 109 opposite the slot 110, the same extending upwardly to a point almost opposite the hinged finger 104 of the arm 99, where it is provided with a cam-fl ange 121, said flange being curved so as to be coaxial with the rod 108. At the center of the flange is a notch 122, into which the finger 104 projects when the standard is in vertical position and the dial-hand is returned to zero. \Nhen the selecting device is swung to either side, the finger moves opposite the flange 121, which prevents the arm from moving forwardly to bridge the conducting-rings 100. In order to permit the same to move, however, it is only necessary to depress the end of the finger 104 below the plane of the fiange,when contact will be made.

123, Fig. 12, is a solenoid into which extends a plunger 124. This plunger carries at its end opposite the solenoid a spring contact-plate 125, that is adapted to bridge across the space between the wires 126 and 127 and connect them electrically when the solenoid is energized. The plunger also carries beside its armature 128 a plate 129, to the ends of which are secured blocks of insulating material, as shown. Pressing against these blocks and normally retracting the plunger are springcontacts 130, which are secured to stationary parts of the apparatus and which are adapted to be pressed against stationary contacts 131 when the plunger is drawn baclr by the solenoid.

The outer ends of the arms 112 of the standard 107 are each provided with a pair of contact- points 132 and 133, which when the standard is moved are adapted to contact with a pair of stationary contacts 134 and 135, respectively. The lower end of the standard is provided with contacts 136, 137, 138, and 139, which when the standard is in a vertical position contact with stationary points 140, 141,

142, and 143, respectively.

144 is a battery or other source of electric:

power at the central station that furnishes the necessary current for setting the lines in condition. Connected with the positive side of the battery is a wire 145, that is passed up the hollow of the standard 107, so as to control an electromagnet. (Not shown, but just like the magnets 33, illustrated in Figs. 3, 4, and 9.) Below this magnet on the return-circuit I shall designate the wire 146. At its lower end it is connected to the middle of a wire 147, that is carried by the arms 112, and terminates at each end in a contact-point 132. The wire 126, above referred to, is connected with wire 146 just opposite the rod 108.

148 and 149 are the conductors in the cables that lead to the plugs 10, (see Fig. 1,) and these conductors are connected to the spring-contacts 118. (See Fig. 15.) They are also connected with the contact- points 134 and 135, respectively. The spring-contacts 130 are connected with the conductors 148 and 149, and

saidconductors are short-circuited through 9 them when the solenoid 123 is energized. This solenoid is connected through a resistance 150 with the conductor 149 and through another resistance 151 and wire 152 with the terminal 140, which is normally in contact with 136, The contact 136 is connected with contact 139 by means of a wire 153, that is carried by the lower part of the standard 107, The contact 139 normally has electrical connection with the terminal 143,and this is connected, through the wire 154, with the conductor 148. From this it will be seen that when the standard is in a vertical position the conductors 148 and 149 are connected through the solenoid 123 and resistances 150 and 151. The wire 127 is connected with the contact 141, and the contacts 137 and 138 are connected bya wire 155. The contacts 133 are connected by a wire 156, and with this wire is connected a wire 157, that leads to the solenoid 113. Beyond this solenoid I shall designate this wire 158, said wire leading to the negative side of the battery 144. The wire 158 is also connected with the contact-point 142.

.I. will now direct attention to Figs. 1 and 8, while describing the connections at the substations. 159 is the talking-battery, which is connected through the wire 160, transmitter 6, the induction-coil 7, and wire 161 with a terminal point 162 above the receiver-hook 4. 163 is another terminal point above the hook, said point being connected with the talkingbattery through the wire 164. As will be understood, when the hook is raised the termi nal points will be connected therethrough and ance 196, with the wire 167.

a current will flow. Instead of supplying the current from a local battery I may employ the well-known central-energy system, if preferred. The impulses that are'set up in the induction-coil are transmitted through the receiver 5 and wires and 166 to the main wire 2 of the party-line, which leads to the jack in the switchboard. pass through the wires 148 to the wire 2 of the other line, which conducts them to the substation that is in the circuit. From said station they are returned through wires 167, 1, 149, 1, and 167 to the receiver-hook 4 and from thence through the hook and wire 161 to the induction-coil again. seen that there is nothing novel about the talking-circuits.

The bell 8 is placed in parallel with an electric motor 168, which drives a make and break circuit device 169, consisting of a disk of insulating material upon which brushes 169 and 170 bear.

171 is a strip of conducting material on the disk that connects the brushes electrically for a short time at each rotation of the disk. It will be remembered from the previous description that there are two sets of contactpoints in the bell-circuit that must be simultaneously closed before the bell can ring. One of these sets is the segmental rings 51 in the selecting device, and the other setis shown at 172 and 173 under the receiver hook. \Vhen the hook is down, the contact 172 is pressed into engagement with the contact 173, as shown.

174 is a local battery that is connected with contact-point 173 through the wire 175. The contact 172 is connected with the return-tozero contact 62 through the wire 176. Leading from this wire is the bell-circuit Wire 177, said circuit, dividing at 178, part of the current going through the bell and brushes 169 and 170 and the rest of it through the motor, the two currents uniting at 179. Beyond this point a wire leads to the outer segmental ring 51. The inner ring is connected, through the wire 181, with a wire 182, that leads to the battery 174. This latter wire is also connected with the wire 167, thatleads to that substation.

Branching off from the wire 175 and leading to a terminal point 183 above the hook is a wire 184, and a similarly-located terminal 185 is connected by a wire 186 with the inner conducting-ring 40. The outer conducting-ring is connected with the wire 166 through the wires 187, 188, and 189 and the relay 190. The wire 189 is connected with a pivoted arm 191, an end of which constitutes an armature for the relay 190 and the other end of which forms a terminal that when the relay is deenergized contacts at 192 with the wire 193, that leads to another relay, 194. This relay is connected, through the wire and resist- The wires 187 From there they It will thus be and 193 are connected through a resistance 197. The relay 194 controls a pivoted arm 198, similar to the arm 191, to make and break a current through the electromagnet 33 from the local battery 199. This current flows from the battery through a wire 200, magnet 33, wire 201, pivoted arm 198, and wire 202 back to the battery.

When users of. telephones in calling do not receive a prompt answer from the central station, they are prone to pump the hook up and down to attract the attention of the operator. This would naturally close the contacts 172- and 173 below the hook and would, as will hereinafter more fully appear, establish the return-to-Zero circuit. 1 To keep these contacts apart at this time when the receiver is down, I pivot a small bell-crank 203 to the casing below the hook in such a manner that the receiver will when hanging from the hook depress its lower end against the tension of a spring 204. To the upper end of the bellcrank I pivot a plate 205, of insulating material, said plate being so placed as to slide between the contacts 172 and 173 when the receiver. is removed. It will therefore be impossible to close these contacts unless the bellcrank 203 is depressed, and the hook can be pumped as much as may be deemed necessary without disturbing the selecting devices on the line.

206 is a signaling device at the central station, one of said devices being connected with each jack in the usual way to indicate to the operator when a line is calling.

In describing the operation of my system 1 will first assume that A on one-party-line desires to talk'with D on another line (see Fig. 1) and that D answers his call. All the dial- .hands are at their Zero positions when A takes his receiver off his hook 4, and all receiverhooks being unlocked the hook flies up to close the contacts 162, 163, 183, and 185. It being remembered that the conducting-rings 40, Figs. 8 and 10, are bridged at A on As selecting device, a current is permitted to flow from the battery 174 at As telephone through the following circuit: wires 175 and 184, hook 4, wire 186, inner ring 40, contactstrip 44, and outer ring 40, beyond which it divides, part of it flowing through the wire 187, relay 190, wires 188, 189, and 166 to the main line 2, which leads to the jack on the central switchboard, through the signaling device 206, the main line 1, back to the substation A, the wires 167 and 182 to the battery again, and the other part flowing through the resistance 197, relay 194, wire 195, resistance 196,'and wires 167 and 182 to the battery. The first branch of this circuit to the the electromagnet 33.

IIO

be remembered, releases the clockwork mechanism and winds up the same, so that the dialhand 45 starts from Zero position and travels around until it reaches A, when it depresses the spring-arm 41 and breaks the connection between the conducting-rings 40. The current in the circuit above traced is broken, therefore, and the relay 194 being deenergized the current through the magnet 33 is also broken, and the locking-lever 31 stops the clockworkmechanism. It is not all of the current that passes out to wire 166, as above described, that goes to the signaling device 206, since it is this current that must control the other selecting devices on the line with A, so as to lock them out of the talking-circuit. Since the connections are the same in all the substations, I will trace this current through the one shown in Fig. 8, into which it will flow over the line 166. The receiver-hook being down, as shown, the current is compelled to flow through wire 189, contacts 191 and 192, wire 193, relay 194, wire 195, resistance 196, and wire 167 to wire 1, and thence back through the circuit already traced to As battery. The relay 194 closes the local circuit for releasing the dial-hand, and said hand will turn, as above described, as long as the current flows from substation A, said current being broken when the hands reach A on the dials. Originally all the receiver-hooks and all the keys 520 were unlocked. WVhen A lifted his receiver, the button or head 81 on the rod 73, that is connected with his hook, passed beyond the locking- rings 83 and 90, and the plate 75 permitted the zero-key to move outwardly, so as to bridge the contacts 40 and 62 to return the line to zero when A hangs up his receiver. On the other telephones on the line the movement of the dial-hands from Zero permitted the plunger 64 of the zero-key to move outwardly, so that the locking-rings 83 could shift to lock the telephone-rods and all the keys 520.

I will now describe the operation of signaling D and of placing him in connection with A. When the operator at the central station notices the signal 206, she inserts the plug 10 into the jack 9 in the usual manner and ascertains that A is desiring connection with D on another line. She accordingly depresses the D pin on the central selecting device, which releases the spring-arm 98 at that point and connects the conducting-rings 100, and then she inserts the other plug 10 on the same cable into Ds jack 9. She then swings the standard 107 toward Ds jack, (the right in Fig. 1,) when a current will be established that flows from battery 144 through the following circuit: line 145, ring 100, contact-plate 101 at the D position, other ring 100, wires 146 and 147, contacts 132 and 134, wire 148 to plug and jack, wires 2, 166,189, and 193, re-

lay 194, wire 195, resistance 196, wires 167 and 1 to the jack and plug, wire 149, contacts 135 and 133, wires 156 and 157 to the solenoid 113, and wire 158 to the battery again. This current controls the operation of the dial-hand 96 on the central selecting device and also the relays 194 for establishing the local circuits for operating the substation dial-hands, and as soon as the hand 96 reaches the D position it depresses the arm 98 and breaks the circuit, so that all the devices on Ds line are stopped with the hands at D. Now it will be remembered that no party on that line has a bell-circuit key 47 at this point except D and that the rings 83 on the other selecting devices will have the telephone-hooks and keys 520 locked, so that D cannot be disturbed. As has been stated, B or C, for example, could have removed their receivers when the dial-hands started and secured the release of their receiver-hooks as their dial-hands passed their keys 47 if it had not been for the rings 90, which are shifted to locking position by the magnets 33 and are held in that position as long as the current flows. When the standard 107 was swung to establish the above-described circuit, the pin 116 separated the spring-contacts 118, Fig. 15, so that the current could not flow back and disturb As line, and the standard was held in this position by the plunger 114, which was drawn into the notches 115 by the solenoid 113. hen the current is broken, however, the plunger disengages the notches, and the standard is returned by the contacts 118, which close together below the pin 116. A is now in talking-circuit with D and all other parties are locked off of the lines; but D has not yet been signaled. The depression of his key 47 closed the contacts 52 of his bell-circuit, however, andhis telephone-hook being down a circuit is established at his substation through the following connections: from battery 174, wire 175, contacts 173 and 172, wires 176 177, hell 8, brushes 170 and 169, wire 180, outer segmental ring 51, contacts 52 and key 47, and wires 181 and 182 to the battery. As before described, the bell is caused to ring intermittently by the motor 168 and disk 169, and this ringing is kept up until D removes his receiver from the hook 4. Of course the bell could be given a continuous ring, if preferred, in which case the circuit between the points 178 and 179 through the motor would be omitted. It will be remembered that the bell-circuit key 47 is provided with a cam 89, that shifts the locking-ring 83 when it is depressed by the dial-hand, so that Ds receiver-hook is unlocked.

It is desirable that each party reestablish his own line to the Zero position when he is through talking. It being remembered that the telephones that have been in use have their zero-keys released and the contacts at 40 and 62 closed, the depression of their hooks by their receivers closes the contacts 172 and 173, and a return-to-Zero circuit is established through the following connections: wire 175,

contacts 172 and 173, wire 176, contacts 62 and 40, wire 187, relay 190, wires 188, 189, 166, and 2 to the Wires 166 of the other substations on the line, from 166 in said substations through wires 189 and 193, relay 194, wire 195,resistance 196. wires 167 and 1 to .the wire 167 of the telephone that has been in use and then through wire 182 to the battery 174. At the outer ring the current divides, as previously described, and flowing through the resistance 197, relay 194, wire 195, and resistance 196 to the wires. 167 and 182 closes the local circuit from the battery 199 to return the selecting device to Zero. It will be understood that the current through the relays 194 at the other substation close their local circuits and set them to zero. When the dial-hands reach Zero, the keys at that point are depressed and the circuit is broken, so that all dial-hands come to rest. Simultaneously the rings 83 and 90 are shifted to unlock all the hooks and keys 520.

In the case above selected, in which A was talking with D, the dial-hands on Ds line, having a shorter distance to travel, will reach zero sooner than those on As line, and as a result the current from As line might disturb the substations on Ds line.

To prevent this result, I short-circuit the conductors 148 and 149 at the central station through the following connections: wire 154, contacts 143 and 139, wire 153, contacts 136 and 140, wire 152, resistance 151, solenoid 123, and resistance 150. A suflicient amount of current will flow through this circuit to cause the solenoid to close the contacts 130 and 131, which will establish a circuit between the conductors that cuts out the resistance 150 and 151. This short circuit will carry practically all the current and prevent it from flowing through central to the other line to disturb the selecting devices there. Inasmuch as this short circuit is at the central station, where it is removed as far as possible from the substation, resistance of the main wires leading to the central station will ordinarily be sufiicient to force the currents through the local circuits at the substations of a sufficient strength to operate the delicately-poised circuit-closers there. If, however, it should be found that the current flows too freely through this short circuit, more resistance will be placed therein, this short circuit being merely intended to keep a current from passing to the other line of suflicient strength to disturb the selecting devices thereon.

As was previously stated, when the circuit was broken in the central selecting device the standard 107, carrying the said device, returned to its vertical position. As the clock- Work mechanism in this device is the same as that at the substations, the dial-hand 96 must have been stopped at D. WVhile mechanical means could easily be adapted to return this hand to zero, I prefer to have this done automatically, however, when the lines are being reset, and for this purpose I provide the solenoid-plunger 124 with the contactpiece 125, which is adapted to connect the wires 126 and 127. When, therefore, A and D hang up their receivers, the return-to-zero currents energize the solenoid 123 and draw the contact-piece into position to bridge across the wires 126 and 127, so that a current can flow from battery 144 through the following connections: wire 145 to the central selecting device, where it releases the clockwork mechanism, as in the other devices, wires. 146 126, contact-piece 125, wire 127, contacts 141 and 137, wire 155, contacts 138 and 142, and wire 158 to the battery. The dial-hand 96 presses back the special spring-arm 99 (see Fig. 17) when it reaches the Zero position and breaks the connection between the conducting-rings 100. so that the current will be broken and the dial-hand stopped, although the current in As line may keep the contact-piece 125 bridged for a short time longer. When the central selecting device is swung for the purpose above described, the pivoted finger 104 rides over the flange 121 which depresses the spring-arm 99 and breaks the bridge between the conducting-rings 100 at the zeropoint; otherwise the dial hand would not stop at D, but would come entirely around to zero. It will also be remembered that when the dial-hand passed D the spring-arm at that point was pressed inwardly until the squared part of the key 102 engaged in the slot in the spring-arm and held it depressed after the dial-hand moved on. I will assume now that D does not answer As call, in which case it is necessary to return his line to zero from the central station. I/Vhen this line was turned to D, the current was broken from the central station and the standard 107 rose into vertical position, as previously described, with the dialhand at D and the conducting-rings 100 bridged at zero. When the central operator becomes satisfied that D will not answer his call, she again swings the standard 107 as beforeand at the same time depresses the pivoted finger 104 so as to bring it below the flange 121. The arm 99 is not depressed, therefore, as was previously the case, and as soon as the circuit is established at the contacts 132, 133, 134, and 135 the current will again flow from the central battery through Ds line and will continue until the dial-hand 96 reaches Zero, when it will depress the special arm 99 and break the circuit, after which the standard 107 and finger 104 return to their normal positions.

In case A and D, for example, on the same line wish to converse it is only necessary for one of them to take off his receiver and press his AD key, when the selecting devices on that line will turn to'the AD position and place those two parties in talking-circuit, it being remembered that they each have a key 47 at this point. In passingaround to theAD key the dial-hands passed and depressed all the spring'arms 41 at the A, B, C, and I D positions. These arms have no radial keys 520 to hold them when depressed; but they are prevented from springing out to bridge the conducting-rings 40 after the dialhand has passed by the hooks 58. When the dial-hands return to zero, these hooks are pressed back to release the spring-arms by the cams on the plunger-s of the zero-keys. The cams 66 on these plungers simultaneously swing the locking-rings 83, and as soon as the current is broken at 40 and 62 the magnets 33 will be deenergized, which will permit the locking-rings 90 to be moved by the springs 82 to unlock all the receiver-hooks and keys 520 on the line.

Having thus described my invention, what I claim as new, and desire'to secure by Letters Patent, is-

1. In a telephone system, a main line, a plurality of telephones on said line,said telephones having receiver-hooks, a selecting device connected with each telephone, said selecting devices being adapted to operate simultaneously and synchronously, a rod connecting each telephone-hook and its selecting device, a perforated plate mounted for movement in said selecting device, the perforation being normally opposite the said rod, and means for shifting said plate to cause it to engage the rod and hold it so that the telephone-hook cannot be moved.

2. In a telephone system, a main line, a plu rality oi telephones on said line,said telephones having receiver-hooks, a selecting device connected with each telephone, said selecting devices being adapted to operate simultaneously and synchronously, and mechanism at each selecting device that is operated when a receiver-hook is lifted to automatically lock all the hooks of the other receivers against release.

3. In a telephone system, a main line, a plurality of telephones on said line, said telephones having receiver-hooks, a selecting device connected with each telephone, said selecting devices being adapted to operate simultaneously and synchronously, a dial-hand on each selectingdevice,a rod connecting each telephonehook and its selecting device, a plate mounted for movement in each selecting device, said plates having perforations opposite the rods when the dial-hands are in normal position, means for causing the plates to shift to lock the rods and the hooks when the dial-hands move from normal position, keys projecting into the'path of the dial-hand to be depressed by the latter, and means on said keys for shifting the said plates to unlock the rods.

4. In a telephone system, a main line, a plurality of telephones on said line,said telephones having receiver-hooks, a selecting device connected with each telephone, a dial-hand on each selecting device, a locking-rod connected with each receiver-hook and extending to the corresponding selecting device, plates in the selecting devices for locking the said rods, means for shifting the plates to their unlocking position while the dial hands are in zero position, means for shifting said plates to their locking position when the dial-hands move from their zero position, keys projecting into the path of the dial-hands to be depressed by the latter, and means on said keys for shifting the plates to their unlocking positions, the arrangement of the keys being such that but one key will be depressed at a time, and only that telephone having that key will have its receiver-hook unlocked.

5. In a telephone system, a main line, telephones on said line, a central station from which said line extends, a selecting device at the central station that is normally disconnected from said line, means for placing said selecting device in circuit with said line, means in said selector for automatically breaking said circuit after a predetermined time, selecting devices at each of the said telephones, said devices being in the same circuit With the selecting device at central, keys on said devices,

means for locking the keys of all the telephones that are on the line except those at one telephone, and means for sounding the signal at that telephone.

6. In a telephone system, a central station, a main line extending from said station, telephones on said line, a movable selecting device at the central station, selecting devices at the telephones, a cable adapted to connect the movable selecting device with the main line, a source of electric power at the central station, contact-points that are closed when the central selecting device is moved to connect the said device with the main line, and contacts in the said device that may be manually closed to establish a circuit from the said source of power through the cable and the selecting devices to set them to a predetermined position.

7. In a telephone system, a central station, a main line extending from said station, telephones on said line, amovable selecting device at the central station said device having keys for controlling electric contacts therein, selecting devices at the said telephones; a cable adapted to connect the central selecting device with the main line, a source of electric power at the central station, contact-points that are closed when the central selecting device is moved to connect the said device with the main line, contacts in the said device that are closed by the depression of the keys to establish a circuit from said source of power through the cable and the selecting devices to set them to a predetermined position.

8. In a telephone system, a central station, a plurality of main lines extending from said station, telephones on each of said lines, a cable at the central station through which a pair of said lines may be connected, said cable being separable intermediate its length, a movable selecting device at the central station and a selecting device at each of the said telephones, a source of electric power at the central station, means whereby the movement of the central selecting device opens the cable and places the source of power in circuit with one of the lines, and means in the said device for completing said circuit so that all the selecting devices will be operated for a predetermined time.

9: In a telephone system, acentral station, a plurality of main lines extending from said station, telephones on each of said lines, a cable at the central station through which two of said lines may be connected, said cable being separable intermediate its length, a movable selecting device at the central station and a selecting device at each of said telephones, a source of electric power at the central station, means whereby the movement of the central selecting device opens the cable and connects the source of power therethrough with one of the lines, means in the said device f'orcompleting said circuit so that the selecting devices at central and on the connected line will be operated for a predetermined time, means for holding the central selecting device in its moved position, and means for releasing the same so that it may be restored as the devices come to rest.

10. In a telephone system, a central station, a plurality of main lines extending from the said station, telephones on each of the said lines, a cable at'the central station through which two of said lines may be connected, said cable being separableintermediate its length,a movable selecting device at the central station, said device being mounted on a pivoted standard, a selecting device at each of said telephones, a source of electric power at the central station, a pin projecting from the pivoted standard, said pin opening the said cable as the standard is swung, contacts on said standard that puts the source of power in circuit with one part of the cable and with the line connected therewith as the standard is swung,

means in the central selecting device for com pleting said circuit so that the selecting devices at central and on the connected line will be operated for a predetermined time, means for holding the pivoted arm in its moved po sition, and means for releasing the same so that it may be restored as the devices come to rest.

11. In a telephone system, a central station, a plurality of main lines extending from said station, telephones on each of said lines, a cable at the central station through which two of said lines may be connected, said cable being composed at one part intermediate its length of two pairs of normally contacting springs 118, a movable selecting device at the central station,said device being mounted on a pivoted standard, a selecting device at each of said telephones, a source of electric power at the central station, a pin projecting from the pivoted standard between the contacting springs 118 and contacts on said standard so that as the standard is swung on its pivot the springs will be pressed apart and the source of power connected with one part of the cable and through it with one of the main lines, means in the central selecting device for closing the circuit from the source of power and means for automatically breaking the same after a predetermined time whereby all the selecting devices are brought to rest.

12. In a telephone system, a central station, a plurality of main lines extending from said station, telephones on each of said lines, a cable at the central station through which two of said lines may be connected, said cable being composed at one part intermediate its length of two pairs of contacting springs 118, a selecting device at the central station, said device being mounted on a pivoted standard, a selecting device at each of said telephones, a source of electric power, as a battery at the central station, a pin projecting from the pivoted standard between the contacting springs 118, and contacts on said standard, so that as the standard is swung on its pivot the springs will be pressed apart and the battery connected with one part of the cable and through it with one of the main lines, means in the central selecting device for closing the circuit from the source of power, means for automatically breaking the same after a predetermined time, a solenoid and plunger for holding the pivoted standard in one position and a spring for drawing back the plunger when the current through the solenoid is broken so that the standard may return to its normal position.

13. In a telephone system, a central station, a party-line leading to said station, telephones on said line, a selecting device at the central station and at each of the said telephones, connections whereby the said central selecting device may signal and place one of the said telephones in condition for use to the exclusion of all other telephones on the line, con nections whereby the said telephone that has been signaled and its selecting device will, if the call has been answered and the receiver removed from the hook, automatically return all the selecting devices to Zero, and means for restoring the first-mentioned connections from the central selecting device to return the said devices to zero if the party signaled does not answer.

14:. In a telephone system, a main line, telephones on said line, selecting devices for controlling said telephones, an electromagnet at each selecting device, and means controlled by a part of the telephone proper that is operating for keeping the other telephones of]? the talking-circuit while the selecting devices are operating, said means being controlled by the said electromagnets.

15. In a telephone system, a central station, a main line leading from said station, telephones on said line said telephones having receiver-hooks, a selecting device at the central station that is adapted to be connected with the said line, means within the said selecting device for closing a circuit through the said main line and for automatically breaking it after a predetermined time, a selecting device for each telephone, said devices being in the circuit with the device at the central station and operating synchronously therewith, an electromagnet at each of the telephone-selecting devices that releases the operating mechanisms of said devices, means for locking the telephone hooks, and armatures connected with said means, said armatures being operated by the said electromagnets.

16. In a telephone system, a main line, telephones on said line, said telephones having receiver-hooks, a selecting device for each tele phone, an electromagnet in each selecting device, a zero-key for each of said devices, and double means for locking the receiver-hooks, one of said means being controlled by the electromagnets and the other by the zero-keys.

17. In a telephone system, a mainline, telephones on said line, said telephones having receiverhooks, a selecting device connected with each telephone, said selecting device having Zero and bell-circuit keys, an electromagnet in each selecting device for controlling the same, a locking-rod connecting each telephone-hook with its selecting device, a locking-plate in the selecting device for locking the said rod, said plate being under the control of the zero and bellcircuit keys, and a second locking-plate for said rod that is under the control of the electromagnet, for the purpose specified.

- 18. In a telephone system, a main line, telephones on said line said telephones having receiver-hooks, mechanism at each telephone that is operated when a receiver is lifted from its hook to automatically keep all the telephones on the line out of the talking-circuit except the one whose receiver has been lifted, a return-to-Zero circuit having a set of contacts at the telephone whose receiver has been lifted, and means for separating the contacts and thus breaking the return-to-zero circuit, said means being controlled by the receiver-hook.

19. In a telephone system, a main line, telephones on said line, a selecting device at each telephone whereby one telephone may be placed in the talking-circuit to the exclusion of all other telephones on the line, a returnto-zero circuit having a set of contacts below the receiver-hook, a plate adapted to separate the contacts, and a spring-pressed lever pivoted to the telephone-casing below the outer end of the hook and normally tending to cause the plate to separate the contacts, said lever projecting into a position to be depressed by the receiver as it hangs on its hook so that the contacts may come together.

In testimony whereof I afliX my signature in the presence of two witnesses.

ALBERT J. SPRINGBORN.

\Vitnesses S. E. FoU'rs, BRENNAN WEsT.

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