US1214638A - Selective lockout telephone system. - Google Patents

Description

F. W. ADSIT.

SELECTIVE LOCKOUT TELEPHONE SYSTEM.

APPLICATION FILED JUNE 30. 1914.

1,214,638. Patented Feb. 6,1917.

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SELECTIVE LOCKOUT TELEPHONE SYSTEM.

APPLICATION FILED JUNE 30.1914.

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F. W. ADSIT.

SELECTIVE LOCKOUT TELEPHONE SYSTEM.

APPLICATION FILED WM 30. 1914. LQPLGSB, Patented Feb. 6, 1917.

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ammmmk WM @wmmw STATES ra rnnr canton FRANK W. ADSIT, .OF ST. PAUL, MINNESOTA, ASSIGNOR TO ADSIT GENERAL ELECTRIC COMPANY, OF MINNEAPOLIS, MINNESOTA, A CORPORATION OF MINNESOTA.

SELECTIVE LOCKOUT TELEPHONE SYSTEM.

Application filed June 30,

To all whom it may concern:

Be it known that I, FRANK WV. ADsrr, a citizen of the United States, residing at St. Paul, in the county of Ramsey and State of Minnesota, have invented certain new and useful Improvements in Selective Lookout Telephone Systems, of which the following is a specification.

My invention relates to improvements in selective lock out telephone systems.

In a system embodying my invention the stations of the respective subscribers on a party line are inter-communicating, and any one thereof may be called by any other party without intervention of the central operator. Both as to ringing and as to telephonic communication, the operation of the system is selective, the instrument sets of the calling and called subscribers, only, being effectively connected with the line as a result of a call. The central station may be signaled in substantially the same way as any other station, and the central operator, of course, may effect calls by selective calling apparatus associated with her cord circuit, and may put any two subscribers lines into connection.

One of the objects of my invention is to provide a system wherein the party-initiated calling operations may utilize alternating current, as of a ringing magneto, for the electrically controlled actions of securing the line, actuating the selectors, and ringing the called station; such arrangement enabling the full power of the magneto to be utilized, giving positive and efficient actuation of the selectors, and dispensing with such commutators, rectifiers, or other ad juncts to the magneto as would be requisite to enable any of these operations to be performed by direct or pulsating current.

Another object of my invention is to provide a system wherein the releasing functions incident to clearing a line and restoring the selector appliances at the subscribers stations to normal condition may be effected by current of a different character, as direct current, preferably derived from a central battery, and, further, efiectively to control the release current supply that the line may be automatically cleared upon the termination of an inter-communi- Specification of Letters Patent.

Patented Feb. 6, 1917.. 1914.. Serial no, 848,161.

. eating call or may arbitrarily be cleared at the will of the central operator.

A further object of my invention is to provide for automatic timing of the automatic clearing-out or release operations so as to fix the permitted durations of a ringing interval and of a communication interval, in order that rules of the line as to maximum time allotted for endeavoring to secure a party who fails to answer, and for a single use of the line for conversation, may automatically be enforced; and further to make such automaticrelease operations subect to suspension by means within the control of the central operator.

Other objects of my invention are to insure that the communicating parties will automatically be'notified, shortly before the expiration of the maximum allotted time for communication, that their time is almost up; to insure the proper setting and releasing of the central station line signals under all conditions where the attention of the operator is necessary to supplement or to supersede the automatic operations of the system; and .to-provide effective central control of all normally automatic operations.

Anotherobject of my invention is to provide the selective mechanism in such structural and systemic relation to the ordinary telephone equipment of a party line that the subscribers station selective apparatus .for the practice of my invention may readilybe added as an attachment to the already present telephone sets; and so to provide such central station equipment that minimum alterations may be necessary properly to equip a central switchboard for most effective employment as part of my system.

Other objects of my invention are to provide, in simple, cheap, economical and effi cient form and systemic relation, suitable appliances for effectively attaining the advantageous results herein described.

In the accompanying drawings I have shown, and will'describe, a single systemic embodiment of my invention for purposes of full disclosure thereof, but it will be understood by those skilled in the art that many changes, variations, and modifications may be made in the structure and arrangement of the parts without departure from the spirit of my invention and within. the scope of the appended claims.

In the drawings Figure 1 shows, under normal conditions, the apparatus of two subscribers stations on a party line; Fig. 2 shows a central station equipment appurtenant to a line; Fig. 3 shows some features of a suitable cord circuit arrangement for the central operator; Fig. 4 shows diagrammatically certain circuit connections existing during the selecting operation for an intercommunicating call; Fig. 5 indicates diagrammatically conditions during the ringing operation; Fig. 6 indicates certain circuit conditions existing during an interval of telephonic communication between the intercommunicating parties; impending release; Fig. 7 indicates certain circuit condi tions incident to releasing operation; Fig. 8 shows a central-energy installation.

Particularly to describe the construction illustrated in the diagrammatic drawings, A A A represent subscribers stations (of which there will often be, say, from 10 to 15, in practice) connected with the line wires 10 and 11 of a metallic or two-wire party line; B indicates in general centralstation automatic apparatus appurtenant to that line; C indicates in general the manually-controlled switch-board equipment including the line jack and its associated keys that are appurtenant to said line; and D represents a cord circuit apparatus.

II. General ,pZan, operations atsnbsert'oers statwn.

At each subscribers station there is a suitable instnument set, a an alternating current generator, such as the customary handoperated magneto a normally short circuited, when not in operation, a manually operable selector-setter a an automatic step-up alternating-current-responsive selector a automatic circuit controlling devices a which in this particular embodiment includes two relays having switch-sets a and a and release means a for the automatic devices. The alternating current magneto supplies current for all of the selective operations. To make a call the party sets the call by turning the selector-setter to the desired number and turns the magneto crank, continuing its operation until the bell at his own station has rung and stopped, its cessation showing that the called party has answered. The selectors a at all stations on the line work synchronously in response to alternating impulses in the line, and the entire selective operation, initiated from a calling station to signal either central or any other party on the party line, is effected by agencies receiving alternating current from the magneto at the calling station. The selector-setter a at the calling station, cooperating with suitable of the automatic circuit controlling devices a at that station, predetermines the number of alternating impulses that will be transmitted via the metallic line circuit to the several selectors; and, at all other stations than that calling, the selector-response disables or locks out their magnetos to prevent conflicting calls. The selector response to any call-setting of the setter a eifects operative connection of the called station instrument-set with the line, for ringing and talking purposes, and locks out all other stations. The automatic circuit controlling devices a, upon causing cessation of the selector-actuating impulses,

shift the magneto connections to connect it in groundreturn ringing circuit with the bells at the calling and selectively-called stations and condition the instrumentset at the calling station for functional cooperation with the line, so that when the switch hooks at the two stations are raised the two parties are in communication; no other party having been signaled, and no other party (save central) having it within his power to listen in on the line. The apparatus at each subscribers station has its release means a, for restoring normal conditions, preferably operable in response to direct current supplied from the central station, but the direct-current supply means at central is normally subject to automatic control from the switch hooks of the subscribers, so that release may take place when aparty hangs up. 7

All of the apparatus at a subscribers station, other than the conventional instru ment set and magneto, may be made small j enough to be housed in a box a (see station A so that the apparatus may be installed on the wall board of, or otherwise located contiguuous to, the usual instrument set.

[I]. General plan; operations of centralapparatus 0n the line.

III. At the central station there is, in the equipment B local to the line, preferably a timer apparatus, 6 automatically potenoperator may, through appropriate instrumentalities of switch-board set 0, clear the line at any time or disable the automatic re lease devices at will. These instrumentalities are supplemented with a signal responsive selector (6* controlling the line lamp or other signal device that attracts the attention of central.

TH. The automatic devices at central so operate that selective signal transmission in the line effects a potentiation of the timer 6 The consequent operation of the timer allots a predetermined time to the ringing operation on the line; then, after lapse of the ringing time, potentiates the releaseactuating devices to respond functionally to such grounding of the line as is caused by a partys hanging up or failing to answer; then, after lapse of a further time, predetermined according to rules of the company, automatically occasions the operation of the release devices at central station and causes the battery to be bridged across the line to restore all subscribers appliances to normal and clear out the whole line. The automatic clearing-out apparatus works, therefore, either upon failure of the called party to answer or arbitrarily at the end of the allotted talking time, or immediately upon either party hanging up before expiry of the full time allowance.

1V. SLtbSCWibTS station apparatus and 0pemtzon.

TV. The selector setter a of each subscribers station is preferably a 'rotatably adjustable dial 12 carrying, for adjustment or setting, a contact 13. A complemental selector-carried contact 13 will connect with 13 after movement of selector shaft 1 1, that carries it through a number of steps corresponding with the setting of the contact 13. The selector shaft is is normally held in one position by the action of a suitable return spring 15, and is movable by a ratchet wheel 16 driven by a suitable pawl 17 carried by the armature 18 of the selector magnet 19 which is generally similar to an alternatingringer magnet and which is constantly brid ed across the line as by wires 20-21. 22 is a holding pawl for wheel 16. Pins 2323 on the step-up wheel govern the phone control switch 24, said switch being connected to the switch look 72, of the instrument set by wire 25 and to the line wire 10 by connections 2627. Since the grounded bell 28 of the instrument set a makes contact with the switch hook it when the hook is down, and the receiver connections 9 make connection from said switch hook to the line wire 11 when the switch hook is raised, it will be apparent that, as far as the selector operation is concerned, it is only when switch 24. is closed by one of the pins 2323 that a subscriber at a called station may get into functional connection with the line. It is my preference that at all stations the first of the pins, 23, on the selector wheel 16 shall occupy the same number-position so that by setting the selector setter a for that number all the subscribers on the line may be called at once. The same thought may be carried forwardby special construction of any number of the selectors to close their switches 2% at the same time as where there are several parties on the line who are particularly subject to call in common. The second pin, 28, occupies a position corresponding with a respective station number so that when the pin 23 of the selector for any subscriber closes the switch 24-, the switches 24 of all of the other subscribers are open and they are accordingly locked out from establishing connection of their instrument sets with the line. The instrument set of a calling subscriber is connected with the line through other means.

TV. A pin 29 on the shaft of the selector, when in normal position, occasions the closure of a switch 30 which I term the magneto-lockout switch, the construction being such that the first step forward of the selector shaft will cause the opening of this switch 30. The magneto-lock-out switch 30 is connected by wires 31 and 32, respec tively, through the magnet 33 of the magneto-bridger relay, to back contacts 34: and 35 of a three-blade gang switch a (which T term the magneto-bridger switch) these contacts normally receiving the blades 36 and 37 that are direct connected by wires 38 and 39 to the terminals of the magneto a Then the magneto first is operated, bridger magnet 33 is energized. (See Fig. 1, heavyline circuit). Tts armature is a latch for switch a It unlatches; the blades of switch a spring over to their front contacts, to remain there until the release takes place. The front contacts 84 and 35 of the two leaves 3637 are respectively connected by wire 4:0, switch contacts 41, 42, and wire 4L3 with line 11 and by wires ll, 27 with line wire 10. This action, therefore, bridges the magneto across the line. The circuit is 10, 27, at, 85, 37, 39, a (magneto), 38, 36, 34', L0, 1-1, 4-2, 43, 11. (See Fig. 4:).

TV". Now, manifestly, the magneto of the calling station will supply alternating current to all of the bridged selector magnets 19 to operate the selectors at all stations on the line, and it will be apparent that the first advance of each selector will open the magneto-lock-out switch 30 appurtenant thereto; (see Fig. 4-) so that when once the magneto of any calling station has been bridged on the line the magnetos at all other stations on the line are automatically locked out and functionally disabled. As a matter of preference the step up wheel of the selector is made with a large number of fine teeth so that the ringer movement of operating magnet 19 may be rapid and so that it takes a number of vibrations of the magnet armature, say 6, to produce a predetermined advance corresponding with one step of the selector setter. This decreases the liabilityof the selectors to get out of step.

IV impelled by selector magnets 19, the step up wheel 16 at each station will rotate, and the extent of rotation is determined by the position of the selector-setter contact 13 at the calling station. When the selector-moved contact 13 comes into connection with the adjusted contact 13 of the selector setter, the pin 23 on the selector wheel of the desired station will be closing its switch 2 1 (Fig. 4).

IV. At this point the operation of the selectors ceases, so as to hold the switch 24 at the station of the called subscriber closed and the magneto circuit connections at the calling station are changed so as to connect the magneto in a ground circuit including the ringers at the calling and called station. The calling subscriber continues to operate the magneto until his bell ceases to ring, its cessation showing that the called subscriber has answered the call. Such shifting of the magneto connection is automatically accomplished by the operation of a magnetogrounding-relay having a magnet 15, the armature of which normally latches the spring 4-1 of magneto-shifter switch a back against its back contacts 42 and 4:2, As soon as selectively set switch 1318 at the transmitting station closes, it establishes a circuit for this relay magnet a5, from the ma neto a throu h wires 39 4:6 switch -17 a: a: a v a f the gang a (now closed), wire 48, se-

lectively-set switch 1313, rotary connections 19, wire 50, magnet 45, wire 51 to back contact 42 for blade 41 of switch a wire 41-0, switch 3 16 and wire 38 to the magneto. (See dotted lines Fig. 4E). Immediately upon establishment of this connection the magnet 45 attracts its armature unlatching switch blade 41 which springs forward, breaking the circuit just described at 4L1'42 and making connection with a front contact 42 which is connected by wire 52 with the switch-hook of instrument set a and consequently with grounded bell 28. (See heavy lines Fig. 5).

IVE Now it will be seen a ringing circuit is established from ground at the transmitting station, bell 28, switch-hook, h, connections 52, 12, 41, 10, 3 1, 36, 38, magneto a 39, 37, 35, 14, 27, 10 to the called station and, at the called station, from line 10 by connections 27, 26 and the now closed selector-switch 2 1 by wire 25, switch hook and bell 28 to ground. Thus the two bells at the calling and called stations on the line, connected in series with the magneto at the calling station, are simultaneously rung. When the party at the called station answers, the bells, of course, cease to ring, as the last mentioned circuit is broken at the switch hook it of the called station.

IV Of course when the called subscriber takes his receiver from the hook he bridges bridged when the receiver is lifted from the a hook, although through difierent connections. It will be understood that the magneto at each station is of the usual type short circuiting its own armature hrough a switch a when not in manual rotation, and so it will be apparent that at the call ing station the receiver is bridged by con nections 11, receiver a, switch hook, 52, 42, 41, 40, 34C, 36, 38, a, frame of the magneto, 39, 87, 35', 47, 27, 10. (See Fig. 6). I

IV. Regarding the inter-communicating functions, enabling any party on a line to call any other party thereon without attention from the central station, it will be apparent that the parts thus fardescribed enable all of the functions of selection, calling and vocal communication to be effected. The releasing operation, however, involves the operation of certain central station apparatus, as an expedient for economical avoidance of requiring a comparatively powerful source of direct current supply at each transmitting station. But at the subscribers station of course there is releasing mechanism for response to such central 1 energy.

1V The release means a is diagrammatically shown as comprising a solenoid release magnet 55 adapted to be bridged across the line wires by connections 20, 20, and 21, 21 whenever a switch 56 of the polarized selector magnet 19 is closed. As far as its own functions are concerned it might be permanently bridged, but switch 56 enables the solenoid to be kept off the line except during its functional operation, and for a very brief interval during each selectorarmature vibration. However the duration of the magneto impulses is not suflicient to work the relatively slow-acting release mag- 3 net 55, which is responsive only to direct current. When direct current of proper p0- larity is transmitted through the line, however, polarized magnet 19 responds to close armatures of their respective magnets 38.

and 45. (See Fig. 7). The mechanical details of such releasing devices form no part of my present invention, and it will be understood that, (as is true with respect to substantially all of the mechanical parts employed for convenient practice of my invention,) I have illustrated the mechanical connections only in such skeletonized form as subserves diagrammatic clearness, rather than mechanical efficiency.

V. Central station call responsive clerice.

V At the central station, it will be understood, the selector apparatus a* has a step up wheel 16 which controls a switch 24: to close said switch when the central number is called, the selector being actuated by a magnet 19 and provided with a direct-current responsive release-magnet 55 corresponding in arrangement with the similar parts at each subscribers station. It will be apparent, however, that the se lector devices at the central station appurtenant to each line may be reduced to minimum, consisting simply of the seselector magnet, wheel, switch and releasing magnet, for the obvious reason that the calling apparatus at the central station will be separate from the signal responsive selector and will be connected with the cord circuit. At central station the switch 24: might, of course, govern a connection with a grounded ringer like that at any other station, but preferably in lieu of such signal receiving apparatus I arrange the switch 2 F to control the switch-board line lamp, l, so that the latter may operate after the usual fashion of the line lamp of any central switch-board. The particulars in this regard will be later described.

VI. Central automatic 00ntr0l of party-line intercoininnnieation.

VP. 1 have heretofore indicated that the clearing out or releasing operation, at the subscribers stations, resulting from energization of release solenoids 55, is eifected by direct-current power supplied from the central station. It is my preference that such release be effected automatically, if either of two defined conditions shall exist, and also that the power arbitrarily to effect or to suspend such releasing operations at will be vested in the central operator. The two conditions under which the release operation should preferably take place automatically are: First, if, after the expiration of a limited time (say one minute for example) allowed for ground-circuit ringing, the line wire 10 be grounded, as it is when either party hangs up, or when the called party has not answered; and, second, upon the expiry of a further predetermined period (say five minutes) to which the duration of a single call is limited by the rules of the line, this regardless of the fact that the parties have not hung up.

VH. Central automatic eleoieestioner.

VH The timer 6 referred to in para graph HP is preferably a retarded train, set in motion whenever the line is energized for use, and operating to manipulate, mechanically, certain switches b and b at predetermined moments in its timed cycle. 60 is a wheel, retarded in rotation as by a suitable escapement 61, adapted to be driven in rotation by the pawl 62 of an arm 63 which is subject to spring elevation for movement in the wheel-driving direction and to potentiation by the action of a timer magnet, preferably in the form of a solenoid 6%, the action of which opposes the spring 65. The switch members that are controlled by the timer-lever 63 are, for convenient diagrammatic illustration, divided into two groups 6 and 71 The double throw switch I), (which I will term the timer-magnet control-switch) has a spring leaf 66 that moves between back and front contacts 67 and 68 according as a spring-resisted switch-snapper or flopover 69 is flopped at opposite ends of the throw of timer arm 63. The upper switch group, b, which I will term the release-control switch, comprises a plurality of members all of which have their effective circuit connections opened when the timer arm 63 is moved to potentiated position, and which are acted on by the timer arm to close their respective circuits in predetermined succession during the timed return-travel of the timer arm (33. This upper switch group Z2 includes a ground switch 71 grounded by wire 72, and a double throw switch comprising a blade 7 3 linked to the timer arm 63 to move therewith. When the timer arm moves down, a pin 74 on the switch blade 73 opens ground switch 71 and holds it open until the timer arm 63 returns a distance proportioned to the allotted ringing time (see Fig. 5). his is to make the releasing devices ground-responsive as hereafter more fully described. When nearing the end of its return it closes briefly (of or a few seconds in practice) a connection with contact 75 over which it wipes. (This is to give a warning signal on the line.) And last, on the rising movement of arm 63 occupying say 5 minutes, said blade 73 closes with contact '76. (See Fig. 7) This is for automatic clearing of the line upon lapse of the time circuit allowed by rule. Considering, mechanically the order of operation of these switch devices 6 and b it is evident that when arm 63 is moved in a potentiating direction, or downward, blade 7 6 may follow blade 73 downward a short distance, while switch 6667 is maintained closed until the potentiating movement is substanlected for diagrammatic simplicity rather than mechanical expediency.

VH1. Central station release means.

VIII. The release means Z9 comprises a release magnet 80; mechanical restoring devices for the timer parts, and circuit controlling switch means for the battery Z2 by which the latter may be bridged on the line for a brief interval pending self-restoration of the release means and battery switch to normal.

VIII". The release magnet 80 of the timer controls av releasing lever 81 and when energized it pctentiates said lever by pulling it over in opposition to a spring 82. Such potentiating movement throws the upper end of lever 81 to the right and its return movement, under the influence of its spring, is itself retarded briefly, as for a few seconds, preferably by the same retarding train 60 which serves the timer arm. The potentiating movement of the release lever 81 throws out the pawl 62 for the timer arm 63 wherever said arm may be, engages a pawl 84: of the arm 81 with wheel 60, and also works a. switch-snapper or fiopover 86, thereby automatically to control a switch set 5'' for the battery 0 as well as the latching devices for certain other switches. The conditions thus established by the release-lever potentiation will maintain until the retarded return of the release lever to normal is completed, when flopover 86 will be thrown back to normal, leaving all parts in normal position.

IX. Central station Potential/tag the timer.

IX. It will be observed that at central there is normally bridged across the line the magnet 90 of a magneto-current-responsive relay. (See Fig. 2). This has connection by wires 91, the magnet coil, normally closed cut-out switch 92, wire 93, normally closed cut-out switch 9%, with wire 95, connected to line 11. The cut out switch 92 is one of a gang, 6 of two switches normally latched in position, with switch 92 closed and the companion switch 96 open, by the action of the relay armature. Consequently, as soon as a magneto current is transmitted over the line at the commencement of the selective signaling operation, magnet 90 is energized by current flowing through the path 10, 91, 90, 92, 93, 9t, 95, 11, whereupon magnet 90 attracts its armature, unlatching switch 5 so that its blades spring over opening cut out switch 92 and closing switch 96. The switch 94 heretofore mentioned is one of a gang of three switches, the others being double throw battery switches, and all controlled, for movement from normal position, by the fiopover 86. The normal position of the double throw battery switches is with their central springs 97 and 97 en gaging their back contacts 98 98 which are connected to circuits local to the central exchange. The front contacts 99 and 99, respectively, of these battery switches b are connected by wires 95 and 91 to wires 95 and 91, leading to the line wires 11 and 10, so that movement of the battery switches from normal position over to their front contacts will bridge the battery on the line. (See Fig. 7.)

IX As soon as the magneto responsive relay 90 works, as heretofore described, in response to the first magneto impulses transmitted over the two line wires, the closure of switch 96 establishes a battery circuit through the timer magnet 64 which is to potentiate the timer. (See Fig. 4). The circuit may be traced as follows: battery 5 switch 97-98, battery wires 100, 101, switch 96, connection 103, timer magnet 64, connection 104:, contact 67 to switch blade 66 of timeranagnet switch Z), connection 105, to junction 106 with battery wire 107 leading back to contact 98, blade 97 and battery. Accordingly the battery current, flowing through the solenoid 64, energizes it, so that it pulls down the timer arm 63 potentiating the timer, and at the extreme limit of throw of the timer arm the flopover 69 is worked, breaking at 66-67 the circuit just described for the timer magnet .and connecting the battery wire 107 with the lower contact 61, which is connected with the main switch blade 73 of the releasecontrol switch W by wire 109. Also this potentiating movement of the timer arm opens the ground switch 71 and release switch 7 376, the successive closure of which is the prime function of the timer.

IX. Thus, almost immediately upon commencement of the operation of the ma gneto at the calling station the timer at central station is potentiated. Generally, the arm 63 is started on its return movement before the selection of the called subscriber is completed; and in any event the return movement of the timer arm 63 is going on during the interval when the calling subscriber is ringing the bell of the called subscriber. A predetermined time, say one minute, elapses before the timer arm 63 is moved back far enough so that the insulated pin 74 on switch blade 7 3 h as left the switch leaf 71 and allowed the latter to close. After that lmore minutes elapses, say, be fore release switch 7376 closes.

X. Central station: Release-controlling means.

The automatic release and. clearing out should take place before the full time allotment for a single call has expired in either of two events: if the called party has not answered within the allotted ringing time; or if either party hangs up between expiry of the ringing time and expiry of the full calllimit of, say, 5'niinutes. These results I accomplish by the employment of a groundresponsive relay Z2 having its magnet 111 in a battery-circuit controlled by the ground switch 71 and through its armature, in turn, controlling local circuits for the release magnet 80. The ground responsive magnet 111 is preferably of high resistance and is bridged across the line by wires 112-112 leading respectively to line wires 10 and 11, and it has a central tap 113 running to a junction point 11% with a wire 115 leading from battery wire 100 direct to the release magnet 80. (See dotted lines Fig. Now it will be apparent that, at any time after ground switch 71 is closed, if there is a ground on line Wire 10, a ground-return, battery-energized circuit will be established Via said ground on the line, wire 10, 112, half of coil 111, 113 to 114, up on 115, 100, 98, 97, battery 6 97, 98, 107 to 106, 105, 71, ground switch 71, 72, ground. Thereupon the ground-responsive magnet 111 is energized, attracts its armature 120 to connect with front contact 121, and thereby closes a release circuit for release magnet 80, as hereafter described (paragraph Xl Half of the Winding of the coil 111 is ample for the necessary energization. The only object in splitting the coil with the tap 113 is to prevent possible unbalancing of the line by the establishment of the ground connections through switch 71, it being appreciated that such connection is maintained from the time of its establishment until the completion of the call.

XI. Releasing operation.

XI. The closure of the switch 120, 121 should result in energization of the release solenoid 80 for performance of its functional operation; and the same effect should follow either from the closure of switch 7 3- 76 at the end of the full allotted time for a call, or from a manual switch operation effected at will by the central operator. To secure the desired results of release-control from these multiple points the release magnet 80 should have parallel circuit connections through the several control switches to battery 6 To this end the release magnet 80,

one terminal of which is connected by wires 115, 100, and switch 98-97 directly with the battery, as heretofore described, has its opposite terminal connected by wire 125 with a normally closed switch 126 appurtenant to an operators release control key, c/c, and from the wire 125 (when connected with battery 6 three alternative connections may be made back to the opposite battery Wire 1077, so that by closing any one of these three connections the battery circuit for the releasing magnet may be established.

XI". One said connection may be made through a switch 128 appurtenant to the key 076 and serving to connect the line wire 125 with wire 129 leading to a junction 130 with the wire 107. Manifestly this gives the cen tral operator a release-control circuit, 6 115, release magnet 80, 125, 128, 129, 130, 107, Z9 that is independent of any automatic switch means.

XI. A second connection may be made from Wire 125 through switch 126 to a wire 131 having a tap 132 to the front contact 121 of the ground responsive relay. The armature 120 of the ground responsive relay is connected by wire 133 with the junction point 106 of the battery wire 107. Thus whenever relay 120 is attracted (if switch 126 be closed, as normally it is) the release circuit 5 115, 80, 125, 126, 131, 132, 121, 120, 133, 106, 107, b is established.

X1 The third connection is closable by timed release switch 73-7 6, blade 76 of which has connection 135 to wire 131. Its release'magnet circuit is 5 115, S0, 125, 126, 131, 135, 76, 73, 109, 68, 66, 105, 106, 10?, 0". (See Fig. 6).

XP. It will be observed that of the three parallel connections from wire 105 to battery 87, the two connections that may automatically be established, namely, the connection 120121 controlled by the ground responsive relay and the switch connection 7 37 6 controlled by the timer, are both effected through the operators manual switch 126 in series therewith; but that the third con nection controlled by the operator, at switch 128, is direct. The result of this arrangement will be manifest. By manipulating key 076 to open switch 126 encrgization of the release magnet through either of the automatic agencies is prevented, and the line will not automatically be cleared, however great the lapse of time. until switch 126 is closed. 011. the other hand, regardless of the position of either of the two automatic switching devices, a circuit for the release magnet may be closed at any time by switch 128, thereby peremptorily to clear the line.

XII. T he Zine clearing operation.

XII? Assuming that an intercommunicating call has been made on the line and that two stations have been in telephonic communication for the period of time occupied by the full rising movement of the potentiated timer arm 63, the automatic release operation that occurs when switch 73-76 is closed, just before the fiopover 69 is thrown back to normal position, is as follows: Glosure of switch 7376 establishes a battery circuit local to the central exchange, including the battery 6 and release solenoid 80, as described in paragraph KT. The direct current energizes the release magnet which shifts the release lever 81, throwing the pawl 62 for the timer arm out of engagement with the ratchet and allowing the timer arm to make the very last portion of its rising movement rapidly, to throw the fiopover 69 to restored position, opening the switch 66 68 and thereby breaking the release magnet circuit. Also this movement of the release lever 81 shifts the fiopover 86, throwing its upper portion to the left so that through suitable mechanical. connections, as the levers 150, 151, it trips the latch for the armature of magnet 90, re-

storing the double pole switch 6 to initial condition, and at the same time it shifts the triple pole switch l2 associated with the bat tery, so as to bridge the battery on the line. It will be observed that the shifting of the triple pole switch opens the switch 94 so that the magneto-responsive relay 90 is left disconnected with the line (pending return of the flop-over 86) and is not responsive to the battery current on the line. The shift of the switch blade 9797 of switch Z) brings the battery into connection with the wires 95' and 91 which, through wires 95 and 91, respectively, are connected to the line wires 10 and 1.1. The direct current thus supplied to the line affects the polarized magnets 19 of all of the subscribers stations, and the corresponding magnet 19 at the central station, the'polarity of the current causing the normally raised ends of the relay magnets to descend so as to close the switch 56 in each instance. Accordingly direct current flows through each release magnet 55 and 55, bridged across the line by the closure of switches 56, so that the release magnets 55 or 55 at each affected station performs its releasing function so that all selector and relay apparatus at each subscriber station is restored to normal in a manner heretofore described. This release action is shown in Fig. 7.

XII". In order to insure maintenance of the direct current in the line for a sufficient time to insure functioning of the release magnets 55, I prefer that the return movement of the central station releasing lever 81 to normal position after the breaking of the circuit for release magnet 80 at the switch 6668, shall be retarded and, as diagrammatically illustrated, this may be done by causing a pawl 84 on said release lever to en age the retarded ratchet wheel 60, or any X111. Warning signal preceding limeol release.

I have pointed out that just before the re lease switch 7 37 6 closes, the switch blade 7 3 makes a brief contact with a switch point 75. This is in order to give a warning signal to the parties on the line indicating that their allotted time for communication is al most expired. As a specific means to give this signal I provide a buzzer 160 connected -with one winding of a repeating coil 161,

the other coil of which is" bridged across the line, and I arrange said buzzer for energizaown from a small local battery 162 whenever the switch 7 3-7 5 is closed. The circuit is established from battery 162 by wire 163 to switch 73, returning via 109, 68-66 (closed under these conditions) 105, 106, 164:, 165, buzzer 160, coil 161 to battery 162. As a result a slight buzzing sound is made on the line for a short period of time at a predetermined interval before the closure of switch 7 3-76 that controls the automatic line-clearing operation.

XIV. Ualling through eenlralline lamp operation.

XIV. The operations heretofore described 0 have been predicated upon the assumption of inter-communicating calls between subscribers on the same line. The calling operationto get the attention of central is the same as the operation to call any other party on the line, the central station being indicated by a number on the selector setter, like any other station. When the central selector a is stepped up in response to the central call, to close the switch 24, a circuit is established for the line lamp l from the central battery 6 as follows (see dot-and-dash lines, Fig. 4): from battery 6 switch 97-98', wires 107, 106, 164, 170, selector switch 24:, wire 171, normally closed switch contacts 172173, (connected with a spring of jack j to open when a plug p is inserted) wire 174, lamp l, wire 175, back to battery wire 115, through switch 98-97, to the other terminal of battery 6 The line lamp glows until the plug p is inserted in the usual jack j, the spreading'of the jack spring mechanically shifting the spring leaf 173 into connection with its front contact, 176, breaking the aforesaid lamp circuit at 17'2173. This front contact 176 for spring 173 is connected 3 by wire 177, switch 178 and wire 179 back to wire 170, thereby throwing a parallel connection around the open switch 172-173, but the switch 178 is closed by a pin 180 on the selector wheel a" only when the latter is in normal or cleared-0ut position. This parall-el connection is afforded to insure that the line lamp will glow (as a clearing out signal) when either party hangs up and the clearing-out operation is eflected, for (incidentally to the clearing out operation,) the selector at central station thereby has its wheel returned to normal position, closing switch 17 8 and reestablishing the circuit for lamp Z through the shunt connection 173--176, 177 178, 179 around the open jackcontrolled switch 172173. When the operator withdraws her plug the clearing out signal is extinguished, for switch 176-173 is opened.

XIV t Vhen the automatic clearing of the line has been made impossible by the operators throwing key 072 to the right to open release-disabling switch 1.26 (as for instance in the event of a toll call where no time limit is imposed) the central selector 62* is not cleared or restored to give the clearing out signal through switch 178. Therefore the line lamp Z should be made to respond, under these conditions, to the energization of ground responsive relay 6. To this end I provide a switch 185, closed by key ck when switch 126 is opened. Switch 185 is included in wires 187,188 running from lamp wire 17 4 to a front contact 189 for armature 120 of the ground responsive relay b.

lVhen line 10 is grounded by a subscriber hanging up, the magnet 111 is connected 'foin wire 10 to ground via 10, 111, 113, 114-, 5, 98-97, battery 5 97'98, 107, 105, 71, 71, 7 :2, ground. Its armature 120 then closes the lamp circuit battery b 9798, 100, 115, 175, Z, 17%, 187, 185, 188,189, 120, 133, 106, 107, 9897, battery 6 This causes the lamp Z to glow to acquaint the operator with he fact that she may restore her key 07c and so clear the line.

XV. The 00rd circuit.

same type as the calling apparatus at the subscribers stations. Various arrangements, and a greater or less degree of refinement 1n automaticity of action may be provided, but

in the present instance I have diagrammatically shown merely a simple form of cord arrangement for purposes of disclosure. Referring to Fig. ,3 the cord (Z has its answer ing and calling sections (Z and (Z (that are respectively connected with the answering and calling plugs, p and 29), associated with each other through a repeating coil rZ. An operators instrument set d is associated with the cord in any suitable fashion and the selective calling apparatus is associated with the calling plug section (Z Of course, as is well understood in the art, since the interchange of electrical energization between the two cord sections occurs only through the repeating coils, compromise cords may be used to effect connection of a subscriber with a line of some other system, requiring any special form of cord equipment, in which event one section of the cord will ake the arrangement appropriate to the different or outside system.

XV The calling section (Z of the cord is connectibl with the selective call apparatus through a key K. In lieu of the magneto generator a constantly operating source of alternating current supply as generator (Z may be employed, connectible in bridged relation to the line and to the step-up mag net 01"' the selector a when the key K is thrown to the left, closing switches l and K and opening switch K that leads to the repeating coil. The selector a receiving alternating current, steps up until its settable switch d closes circuit (Z that includes battery (Z switch (Z and magnet 6Z whereupon the magnet 6Z properly energized, attracts its armature (which is thereupon latched in attracted position by an armature of the releasing magnet (Z opening switch (Z and also a switch 6Z that is interposed in the connection between the generator (Z and switch K This leaves the generator, one terminal of which is grounded, connected only with the sleeve strand of the cord, (which connects with line wire 11) and the step-up action of the selectors stops. When the operator then throws key K to the right she moves switch K that closes a connection for the tipstrand or" the cord through a lamp 6 the generator (Z to ground, thereby to ring the bell of the selected station, and that also opens the cord-strand leading back to the repeating coil. To restore the selector to normal the operator closes key (Z which is connected in a circuit (Z with battery (Z and magnet (Z and said magnet, when energized, unlatches switches (Z and. cl and also withdraws the pawls of the selector a to permit its spring-restoration to initial position.

XV. Manifestly a single selector apparatus may be multiple-connected to any desired number of cords, as the operator can make only one selective call at a time in any event, the construction shown permitting XVI. Rsum of operation.

The calling party sets his selector setter a? to indicate the number of central, it he is going to call to some other line, or the number of the desired party on his own line, if the call is to be intercommunicating. Assume the latter condition and that the set call is for station No. 9: By continually turning his magneto the caller secures the line, operates all selectors thereon, looking out the magnetos at all. otthe stations that there may be no interference with his call; stops the selector operation when all the selectors on the line have stepped forward 9 steps, and rings the-bells at his ownand at the called station, conditioning his own instrument set and that at the called station for communicating connection with the line. The operation of the calling magneto a? first energizes relay 33 (Fig. 1) which switches (at a the magneto into'bridged relation to, the line (Fig. 4:) so that the bridged selector magnets 19 of all stations on the line respond, stepping up the selec tors a synchronously until, at the calling station, the settable switch connection 1313 is made between the selector moved contact and the selector-setter contact (dotted lines, Fig. 4E) whereupon magneto grounding relay magnet 45 is energized, tripping its switch a to break its own circuit and to connect the calling magneto from line 10 to the grounded bell at the calling station. Accordingly all of the sel'ectors stop; selector atstation 9 standing in such position that its control switch 2% is closed, connecting the switch hook of the called station to line 10 and establishing the ringing circuits. (Fig.5.) Removalot' the receivers from the switch hooks bridges the twoinstrument sets on the line, (Fig. 6) that at the called station through the switch 24 and at the calling station through contact 42 and the short circuiting switch 620 of the magneto that is closed whenever the magneto is not in rotation. At central station the first magneto impulses on the line energize the normally bridged relay (Fig. '1), the switches, b, of which are unlatched, opening the relay circuits and closing a circuit from the central battery 6 to the timer potentiating magnet 6% through the switch 96. Fig. 4.) The timer is spring returned against retardation of its train. After a definite time lapse, during which all of the switches of the releasing set 6 are open, (such interval being allowed for the ringing operation to secure response of the called party,) the timer arm lifts lever 73 far enough to permit closure of the ground switch 71 which connects the ground responsive relay 6 to the line 10 (dotted lines, Fig. 5); later, almost at the limit of its return movement, the timer arm causes closure of the switch 73-7 5 for the buzzer so that through the'repeating coil 161 a slight noise may be made on the line to warn the parties that their time has nearly elapsed; and then almost at the conclusion of its range of throw, afterthe lapse of the total time allowed for a single conversation by the rules of the line, said timer arm closes the release switch 73-76, (Fig. 6) and then, last of all, it works flop-over 69 to shift switch 5". (Fig. 7.)

The release switch 7376 is in parallel with a. switch 120 132 controlledv by the magnet 111 of ground responsive relay b and these two switches are in series with a release-disabling switch 126 manually controlled by'the central operatorslrey air. The circuit on which these three switchesoperate connects the battery and the releasing solenoid 80, so that it either the groundrelay' controlled switch (120-132) or the release switch (7375) be closed the release solenoid is energized from central battery. Therefore, either ii the party hangs up during the time allowed for conversation (in which case he will ground the line 10 and cause the round responsive relay 5 to operate) or when the switch 7376 closes by lapse of the maximum time, the release is automatically effected, but the central operator by opening switch 126 may disable these autjrinatic switches, or by closing switch 128 may establish a batteryto-release-solenoid circuit independently of these automatic switches. En'ergizaticn of the release solenoid in any event moves the release lever 81, (Fig. 7) the return movement of which is retarded for a short interval of time, to give ample time allowance for the clearing out operation. The solenoid impelled movements of the release lever, 81 causes the gang switchb appurtenant to the central battery to be shifted to bridge the battery on the line. This causes all of the selector magnets 19 at the respective signaling stations to throw their armatures down in such direction as to close their switches 56 which bridge the releasing magnets at the subscribers station on the line andthese releasing magnets (which are not adapted to respond to the alternating magneto current) respond to the direct current to actuate the mechanical releasing devices for the several selectors, clearing the line and restoring all subscribers apparatus to normal condition. When the central station releasing lever 81 effects its spring re turn to normal condition it causes the bat tery bridging switch to snap back to normal position and the restoration of all automatically moved parts at the central station to normal has been completed.

When the central station is called the selector (3* closes at 2& the line lamp circuit that receives its current from the central battery. (Dot-and-dash lines, Fig. d.) When the operator plugs in the line lamp circuit is broken at the plug controlled switch 179. When the call has been completed and the automatic clearing out takes place the return of the central station selector a to normal condition closes the circuit for the line lamp through switch 178, and this circuit is broken at 17 6 when the operator removes her plug. When the operator throws switch 126 to disable the automatic line-clearing means, by moving her controlling key 070, the same key movement closes at switch 185 a connection for frontcontact 189 of said relay 72 that makes the response of the ground relay, occasioned by a subscriber hanging up, to energize the line lamp Z and give a clearing-out signal.

The operators calling device is connectible to any one of her cord circuits, and, save that for convenience a constant source of alternating current may be substituted for a hand magneto, with suitable changes of details, the centrals calling arrangement is practically the same as that of any other subscriber. Throwing key K for any cord to the left connects the selector magnet with the calling section (Z of that cord. Throwing said key K to the right connects grounded generator al to the tip-strand of the cord (connectible with line wire 10 through the jack) and rings the called subscriber. Closure of key (Z releases the selector which may be used to make other calls while the first-called party is being rung.

The system which I have heretofore de scribed as a single embodiment of my invention, is illustrated as having the talking circuits energized by local batteries, as is common practice in many party-line exchanges; but where it is desired to use central energy for the talking circuits, in lieu of local bat-- teries at the subscribers stations, this may readily be accomplished with but few changes in the organization of the system. Under such circumstances I prefer that the central talking battery be connected with the line only pursuant to the selecting operation, or subsequent to an alloted time adequate for the performance of the selecting function. This in order to prevent the battery from receiving alternating current impulses, as it would if bridged on the line during the interval when the magneto bridged for its selector-actuating function. It will have been noted that the common battery that occasions the release operation is connected with the line to establish a definite polarity, to accomplish the releasing function- Therefore on the other hand,

where central energization for talking purposes is provided, the battery connections for supply of talking current should produce the opposite polarity on the line, where the selector-magnets are, as in the present illustration, bridged across the line-wires.

In Fig. 8 I have outlined a central energy system embodying my invention, all circuits and apparatus being the same as those heretofore described, except for the few changes now to be noted.

In the drawings, for simplicity of illustration I have shown the talking battery t?) as a battery independent of the release battery 6 although consolidation of all of the central station means of direct-current-supply into one source might be effected. The talking battery it is capable of being bridged on the line by the simultaneous closure of two switches 190 and 191 in series connection therewith, one switch, 191, being timed, as to effective closure, to insure that the battery-bridging will be subsequent to the selecting operation. Since the system shown provides a central station timer, that instrumentality may conveniently be employed for timing the closure of switch 191. In the specific arrangement shown switch 190 is associated with the flop-over, 69, to be closed at the end of the down stroke or potentiating pull of the timer-arm, when flop-over 69 is thrown down. The other switch 191 is arranged for closure on the return movement of the timer arm after a lapse of time, 1 (which may be emperically determined) equal to or slightly in excess of the maximum time that is required for selection of the highest number on the line.

At each subscribers station the telephone set a is of course appropriately changed in wiring to meet the central energy conditions, one known form of instrument wiring being shown.

It will be observed that when the system in general is operated as heretofore has been described, pursuant to signal initiation from any subscribers station, the talking battery 65 will remain open-circuited during the clown stroke of the timer arm, as switch 191 will open before switch 190 closes, and that then, after switch 190 is closed owing to the shifting of the flop-over, 69, the circuit will continue open for the predetermined maximum-selecting-time, until switch 190 is closed by the rising arm of the timer. This will bridge the talking battery 25?) on the line, thereto remain until the timer arm reaches its highest position and throws the flop-over back to normal position, so reopening switch 190. In order that calls which are not to be subject to maximumtalking-time-limit (such as long distance calls) may not be subject to interruption by the cutting off of battery when the timer arm is restored to highest position, I preferably provide in connection with the key 070 a switch 192, in multiple with the two series switches 190, 191, and is closable by the throwing of key 070 to the right; that is, to position preventing the automatic release, and clearing out. Of course when switch 192 is thus closed, the talking battery tb will be maintained on theline until the operator manually restores key 07c.

Save forv the modification incident to installation of my system on a basis ofeither central or local battery energization of the talking circuit, to meet the two basicconditions most commonly met in practice, I have shown herein only a single embodiment of my invention for purposes of disclosure. It will be understood however, that in its broader aspects mv invention is not'limited in detail-to the structure and arrangement specifically shown but is susceptible of many modifications within thespirit of my invention'and the scope of the appended claims.

7 I believe it to be broadly new with me to employ full magneto-generated-alternating current for intercommunicating-and-central-calling selection in one circuit and ringing in another circuit; to employ in connection with such selective system,.a distinctivecurrent release; and also in employing as a release-relay the same alternatingcurrentresponsive magnet that actuates the step up selector. And I believe it to be broadly new to time automatically the maximum allotment for ringing and for talking service; and, in a system employing alternating current selecting current on the line, to time automatically the connection of a centraltalking-battery to the line. These and other features I intend to claim broadly for their individual benefits and combinatively in their advantageous associations herein dis closed.

I claim-:

1. In a selective telephone signaling sys tem, the combination with ametallic line, of subscribers instrument sets, each includ ing a grounded bell, and at each subscribers station a source of alternating current supply, a step-up selector responsive to alternating current adapted on a predetermined step to connect the instrument set with the line, and settable means cooperating with the selector to control" the number of steps duration of current flow to the line from the source of alternating current supply at said station.

2. In a selective telephone signaling sys tem, the combination of a metallic line; at each subscribers station an instrument set including a grounded bell; a source of alternating current supplv, a step-up selector responsive to alternating current adapted, after a predetermined number of steps, electrically to connect said instrument set and bell to the line, a selector setter comprising a switch settable to close at a predetermined position of the selector, means for bridging each subscribers station an instrument set including a grounded bell; an alternating current generator; a selector responsive to alternating current in the line and adapted, on a certain step, to condition the bell for ground connection .on one side of the line and the telephone instrument for bridging connection with the line; a selector-bridging relay having its magnet normally connected with the source of current supply and acting when energized .to bridge the source of current supply on the line, thereby to actuate all selectors; selector setting means including a switch settable to close after any predetermined number of selector steps; a circuit local to said station, and means therein responsive to alternating current from said source of supply, and controlled by said settable switch, to operate onswitch-closure, for disconnecting said source of current supply t'rom one side of the line and grounding it for operation of the bell at the called station; 7 K

l. In a selective telephone signaling. system, the combination of two line wires; at each subscribers station an instrument set including a grounded bell; analternating current generator; a selector responsive to alternating'current in the line'and adapted, on a certain step, to condition the bell for ground connectioncn one side of the line and the telephone instrument for bridging con nection with the line; a selector bridging relay having its magnet normally connected with the source of current supply and acting when energized to bridge the source of cur-' rent supply on the line, thereby to actuate all selectors; a selector controlled switch for breaking said normal connection, a circuit local to said station, and means therein responsive to alternating current from said source of supply, and controlled by said settable switch to operateon switch-closure, for disconnecting said source of current supply from one side of the line and grounding it for operation of the bell at the called station.

5. In a selective signaling systemthe combination with two line wires, of subscribers apparatus at each station comprising an instrument set having a grounded bell, a

switch hook for connection with one line wire and telephone instruments connected with the other side ofthe line a magneto generator; a step-up selector responsive to

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