US1181559A - Intercommunicating selective lockout telephone system. - Google Patents

Description

F/W. ADSIT. I INTERCOMMUNICATING SELECTIVE LOCKOUT TELEPHONE SYSTEM.

APPLICATION FILED DEC-8, 1914.

Patented May 2, 1916.

THE COLUMBIA PLANOGRAPH c0-, WASHINGTON, n. c.

'rn sas NT EPIC.

FRANK W. ADSI'I, OF MINNEAPOLIS, MINNESOTA, ASSIGNOR TO AIDSIT GENERAL ELECTRIC COMPANY, OF MINNEAPOLIS, MINNESOTA, A CORPORATION OF MINNESOTA.

Specification of Letters Patent.

Patented May 2, 1916.

Application filed December 8, 1914. Serial N 0. 876,117.

To all whom it may concern:

Be it known that I, FRANK W. Aosrr, a citizen of the United States, residing at Minneapolis, in the county of Hennepin and State of Minnesota, have invented certain new and useful Improvements in Intercommunicating Selective Lockout Telephone Systems, of which the following is a specification.

My invention relates to improvements in intercommunicating selective lock-out telephone systems, and in some of its features more particularly to a. system of the general character described in my copending application, Serial No. 8%,161 filed June 30,1914. It will hereafter become apparent that while the subscribers station apparatus and central station apparatus of the system herein described cooperate systemically in new and advantageous fashion, the particular sub scribers-station apparatus herein shown may be employed in conjunction with central station apparatus as shown in Figure 2 of the drawings of said prior application, while the centralstation appratus herein shown may be employed in connection with the subscribers-station apparatus shown in Fig. 8

of said prior application.

Like the system shown in my prior application the present system contemplates a party-line installation, and in its preferred embodiment provides for intercommunication between the parties on a line, without the intervention of the central operator, upon a selective operation initiated from any subscribers station; contemplates the looking out, or disabling against selective operation, of the signal-initiating means at all stations other than that of the party first initiating the call and so securing the line; contemplates the locking out, or disabling, of the instrument sets of all subscribers save the calling and called subscribers; provides for the employment of the full alternating current of a ringing magneto for the electrically-controlled actions of securing the line, and actuating the selectors, as well as ringing the called station; provides for the release of all centraland subscribers station apparatuses that have been set incident to a call, automatically upon the completion of the call, by distinctive current, such as direct current, preferably supplied from a source common to all stations on the line, and therefore preferably located at the central station; and provides central station apparatus whereby the central operator may efiect manual con trol of the releasing and clearing out operatlons, superseding the normal automatic operation thereof.

Distinctively from the system of my said copending application, one of the objects of the present invention is to provide selective means whereby any plurality of parties, (they being any desired parties of those on the line), may be selected and called for simultaneous communication from the station of any subscriber, and further to effect the closure of the circuits for the instrument sets of the called subscribers through relayoperation, rather than directly by the selectors.

Another object of my invention is to provide a centrally-energized talking circuit, wherein the central source of energy is automatically controlled so as to be not bridged upon the line until after the magneto has been removed from bridging communication with the line, and this without interposition of a horological timer; and a further object of my invention is to provide for automatic retardation of central station apparatus-setting during the maintenance of certain subscribers-station-initiated conditions.

Another object is to provide for the automatic connection of a grounded release-controlling device with the line subsequently to the cessation of the ringing operation and the arrangement of said device to cause the release when it is brought into closed-circuit conditions, due to the hanging up operation at any active station; these automatic operations being effected through the agency of the electro-responsive retarding means as distinguished from a horological or arbitrary timer.

Other and further objects of my invention will become apparent to those skilled in the art from the following description taken in conjunction with the accompanying drawing, wherein I have illustrated in diagrammatic form an embodiment of my invention, showing, it will be understood, all mechanical and electromechanical parts in such skeletonized and simplified forms as seem best suited to diagrammatic clearness,

and, of course, without particular regard to' mechanical efliciency.

Referring to the particular construction shown in the single illustrative exeinplification, A and A represent subscribers stations (of which there will often be, say, from ten to fifteen on a single line, in practice) connected with the line wires 10 and 11 of a metallic or two-wire party line; B indicates in general the central station automatic apparatus appurtenant to that line; C indicates in general the switch board equipment for that line comprising in general a signal lamp Z, line jack j, the central station call-responsive selector S and the operators controlling key 070.

At each subscribers station there is a suitable instrument set a ,wired, from transmitter to switch hook, in any suitable fashion for central energization, the switch hook, sh, when depressed by the hanging up of the receiver coacting as usual with the contact for a grounded ringer 1' (preferably supplemented by a short-circuiting switch a". An alternating current generator, such as the customary hand-operated magneto a normally self-short-circuiting when not in operation, is employed as a source of supply of alternating current for selecting and ringing purposes; and at each station there is provided a manually operable selectorsetter o and an automatic, step-up, alternating-current-responsive selector a, together with automatic circuit controlling clevices a and suitable release means a, preferably operable by direct current of suitable polarity applied to the line wires.

The selector setter a to be manually set by the subscriber, predetermines which pai ty or parties of those on the line will be called; and certain of the automatic circuit-controlling devices a to W1t,-111 the present instance, appropriate elements of the switch-set a'", that I term the magnetobridger switch, controlled by an appropriate relay magnet 7bridge the magneto a on the line and prepare the selector-setter to perform its function, as soon as the magneto is started in operation (provided the line is not already in use). The selector a at each subscribers station, stepping up in harmony with the impulses transmitted in the line by the bridged magneto, a governs the relaymagnet for a second switch-set a (that I call the cutting-in switch) of the auto matic circuit-controlling devices a, so that the magnet S will be energized, and the switch-set will be operated, at the station of each subscriber indicated by the setting of the selector setter a at the calling station. This operation of the switch-set a at each called station bridges the instrument-set of that subscriber on the line; and at the calling station the selector a, at a predetermined point in its rotation energizes the magnet 3 of its own switch set a so as to connect the instrument-set of the calling party with the line, and also-to condition the calling partys magneto to transmit its alternating current through a grounded= mally held in one position by the action of a suitable return-spring 15 and is movable by a ratchet or step-up wheel 16, driven in r0- tation by a suitable active pawl 17 carried by the armature 18 of the selector-magnet 19, which is generally similar to an alternating ringer magnet and which is constantly bridged across the line by wires 2021.

is a holding pawl for the wheel 16.

A pin 23 on wheel 16 governs the controlswitch 2%, and is located in position on the wheel corresponding with the number of the particular station. Switch 21 is in the circuit for the cut-in magnet controlling the switch set a and this switch is instrumental in cutting-in the apparatus of a station being called. An appropriate pin or projection 25 on the selector wheel coacts with another switch 26, also in a circuit for the magnet 8, so as to close said switch 26 at a predetermined point in the rotation of the wheel 16, greater in extent than that necessary to call the highest number on the line. It is closure of this switch 26, in the particular exemplification shown, that results in establishment of ringing conditions and the cutting in of the calling station.

A pin 29 on the shaft of the selector, when in normal position, occasions the closure of the switch 30, which 1 term the magneto lock-out switch. This switch is connected by wires 31 and 32 respectively, through the magnet 7 of the magnetobridger relay to back contacts of the double throw switch blades 33 and 3-4, that are direct-connected to the terminals of the magneto (4". These blades are part of the magneto-bridger set 0 the front contacts for said blades 33 and 34 being normally connected with the opposite line wires 10 and 11.

Now manifestly as soon as the magneto. a is set in operation current is passed through the circuit (1?, 33, 7, 31, 30, 32, 3%, a energizing bridger-relay magnet 7, the armature of which acts as latch normally holding back all of the four blades of the switch set (6 so that as soon as the magnet is energized the blades spring over, connecting the magneto with the line, and opening the circuit for the magnet 7, at the back contacts of blades 33 and 34. The front contacts for blade 33 isconnected by wire 35, switch-blade 36 of the switch set a back contact 37 and wire 38 with the line wire 11; while the front contact for switch blade 34: is connected by Wire 39 with the line wire 10. The magnetobridging circuit therefore may be traced from line 10, 39, 31, magneto 0, 33, 35, 3G, 37, 38, to line 11. Now, manifestly, when the switch-set a7 has thus oper ated the magneto of the calling station will supply alternating current to all of the bridged selector-magnets 19 to operate the selectors a at all stations on the line (including the central station) and it will be apparent that the first advance of each selector will open the magneto-lock-out switch 30 appurtenant thereto, so that when once the line is engaged the magnetos of all other stations are automatically locked out and functionally disabled.

Impelled by the selector magnet 19, the step-up wheel 16 at each station will rotate as long as its magnet 19 continues to receive the alternating current and at the several stations, successively, pin 23 will close switch 24. a Only at the station or stations indicated by the setting of the selector-setter a? of the calling subscriber will this switch 23 clo-.

sure produce any effect, however, the selective operation being accomplished as follows: When the selector-moved contact 13 at the calling station comes into connection with the first settable contact 13, of the selector setter (and for present illustration we will assume that two of the contacts 13 at station A have been depressed to call two parties for simultaneous communication) the pin 23 of the station A corresponding with said first-selected button 13 will be closing the switch 24. This will establishin said called station A a connection from ground through the ringer, the closed switch 2% and magnet 8 to the line wire 11, while at the calling station the cooperation of contacts 13 and 13 will establish a connection from said line wire 11, through said contacts 13 and 13 to the ringer and ground, via the magneto a so that at the said called station an impulse will pass through the magnet 8 to cause its armature to unlatch the switch blade 36 to occasion such a change of the circuit connections at the calledsubscribers station as will operatively connect his instrument set in relation to the line wires, for ringing and talking purposes. See heavy lines at station A At the calling station the shifting of the magnetobridging switch a will have closed the switch 10 (normally open) and will have opened a switch 4-1, (normally closed). The switch 40 is connected in a wire 42 to the selector-setter disk 12, that also has conncction by wire 13 with switch 26 and thence by wire M- to magnet 8 and by wire 45 to a back contact 16 to the switch blade" 36 of set a The switch 24: heretofore described effects connection between said wire 14 and a wire 47 that leads to the switch hook sit, and from said wire 17, connection 18 is made through a rotary contact arrangement 4E9 on the selector shaft to the movable contact 13. New, remembering that at the callingsubscribers station the switch set a? has bee unlatched, but that at all the stations it is in normal condition, it will be apparent that closure of the switch 24: at a called-subscribers station simultaneously with the closure of switch 1313 at the calling-subscriber"s station will establish the following groundto-ground, magneto-including, circuit from the calling-subscribers station to the first called subscribers station; viz: ground at the calling station, ringer r, switch hook .972, 17,48, 13, 13, 12, 10 (closed at the calling-subscribers station), magneto a 33, (closed on its front contact), 35, 38, line 11, (thence along the line 11 to the called subscribers station and to ground via) 38, contact 37, blade 36, contact 46, 45, cut-in magnet 8, 4 1, switch 24 closed by the selector at this particular station only), 4-7, switch hook 871, ringer '1', ground. Such circuit, since it includes the ringer '1", may cause an incidental tap of the bell, but the condition is only momentary, for the energization of magnet 8 at the calledsubscribens station immediately unlatches the switch blade 36 which springs over, leaving its back contacts 37 and d6 and closing on the front contacts 50 and 51. One of these contacts has connection by wire 52 directly to switch hook sh, and the other has connection by wire 53, switch 41 (closed at the called subscribers station) with the wire 39 running to line 10, so that at the station of the called subscriber this operation of the switch a connects the switch hook via 52, 50, 36, 51, 53, 4:1, 39 with line wire 10, (heavy lines sta tion A?) and, the transmitter being already directly connected with the line 11, the ringer and the talking instruments at said called station are thereby operatively associated with the line for their functional operations accordingly as the switch hook is raised or lowered.

At the calling station the circuit-closing operations described are merely incident to the contact 13- sweeping by the contact 13, and so the stepping up operation continues. At each station corresponding with the other settings of buttons 13 of the selector setter a the operation heretofore described is, of course, repeated.

After all of the selected stations have had their instrument sets operatively connected with the line, contact 25 of the selector closes the switch 26 at all stations, but only at the calling station is this closure effective for any purpose, for at all other stations the switch 40 is open. At the calling station the closure of switch 26 establishes the circuit from the magneto a", via switch i0, 42, 43, switch 26, tt, magnet 8, 45, 46, 36, 35, 33, to ta energizing the magnet 8 so that the switch set a of the calling subscriber is unlatched and the switch blade 36 throws to the right. This unlatching of switch set a at the calling subscribers station efiects changes in the circuit connections to ground the magneto a through the ringer r or switch r at the calling station and connect the other terminal of the magneto to the line 10, so as to condition the system for the ringing of the bells of the called subscribers and the bell of the calling subscriber by the continuing operation of the magneto a This ringing circuit may be traced from ground at the calling station via the ringer 7, switch hook sh, 52, 50, 36, 35, 33, magneto a 3-4, 39, line 10, and at the called station from line 10 via 39, 41, 53, 36, 50, 52, switch hook sh, ringer 1', to ground. heads.) Closure of switch 1* amplifies the current flow to the multipled ringers of the called parties by cutting out the resistance of the calling-station ringer. This transference of the magneto connections from bridged relation to the line to grounded connection with one side, 10, only of the line, of course stops the transmission of the selector-actuating impulses so that all selectors cease to operate and will stand in the described position pending release. The calling subscriber will continue to operate the magneto until his own bell, which is in series with the line, (to which the bells of the called subscribers are now grounded in multiple,) ceases to ring, indicating that all called parties have answered, and then, when the calling subscriber takes his receiver from the hook, and ceases to operate the magneto, the short-circuiting switch a of the magneto closes the circuit (heavy line) 10, 39, 34, a, 33, 35, 36, 50, 52, sh, a, 11. Now the talking sets of all of the interested parties are in operative association with the line, ready for communication upon the application of the central battery to the line to supply the requisite current. Assuming that now the central battery is bridged on the line with such polarity that the direct current passing through the bridged magnets 19 tends to hold their armatures the tighter in normal position, it will be clear that talking conditions will prevail.

For eiiecting release of the set selectors, direct current of opposite polarity to the talking current is impressed on the line, reversing the polarity of the selector magnets 19 at all stations, so that said magnets thereupon act as relays, each closing a switch 56 in the circuit 20-2l for a re- (See arrowlease solenoid 55, closure ofswitch 56 bridging said solenoid 55 on the line to be energized by the direct current. The solenoid 55 is the actuating member of the release mechanism a and is associated with suitable mechanical devices in the form oflevers and links or otherwise, (schematically shown in such form that the operation is obvious) and which acts, upon energization of the solenoid, to restore to normal position, under tension, the two switch sets a and a and to trip out the active and holding pawls l7 and for the ratchet wheel 16 to permit its spring restoration to normal position. For convenience and economy I prefer that the release-current-supplying' battery be located at the central station, in association with automatic circuit controlling means, such that when one of the subscribers hangs up, the release battery will be bridged automatically upon the line and maintained there a suiiicient time to insure efiectiveenergization of all of the release solenoids 55 at the several subscribers stations.

The central station line equipment B therefore provides, for cooperation with the subscribers station instrumentalities heretofore described, means for bridging the talking battery on the line, subsequently to the selecting operations; and automatic means,

responsive to the circuit conditions produced by a subscribers hanging up, for bridging a battery on the line with reverse polarity to actuate the release devices atthe subscribers station. In the specific arrangement shown the battery I) is employed as both the talking battery and releasing battery, it being associated with .a pole changing switch set 6 automatically operable under appropriate conditions to reverse the polarity impressed on the line. Also I have shown a second battery 6 arranged for ground-circuit connection and for local circuit connections to supply energy for the release operation and for certain of the central-station automatic operations; and since this battery might be damaged by the ringing current, if it were connected between line and ground during the ringing operation, I make provision whereby the connecting of this battery with the line is automatically retarded until the ground transmission of ringing current has ceased.

The scheme of operation of the devices at the central station, as specifically shown, is as follows: Normally batteries 6 and b are open circuited or disconnected with the line, and no normally bridged circuit is provided in the apparatus B, so that during the interval when the selective impulses are being transmitted by the bridged magneto, no functional. operation takes place in the devices at B. A normal ground circuit from wire 10 is provided, however, including an alternating current responsive device, in the form of a potentiating solenoid structure 72 so that as soon as the magneto at the calling station is connected to ground for ringing purposes the central solenoid 72* is energized and operates to close the circuit for an actuating magnet 6 energized by the battery 6 Under the control of this magnet are two switch sets 6 and b the switches of both these switch sets shifting their position when the armature 57 of the magnet is attracted, and the switches of set b being restored to normal position when the armature 57 is released. This is accomplished, in the schematic representation, by causing the armature 57 of magnet b to coact directly with the switches of set If and to cooperate with a drop-arm b governing the switches of set 6 These appliances Z), 6 and b constitute but one electromechanical expedient making provision that as long as magnet Zr is energized the circuit for solenoid b is maintained closed and the talking battery 6 preferably (though not essentially) cut out of bridged connection with the line, while upon subsequent retraction of the armature 57, the bat tery b is bridged on the line to supply talking current and battery 6 is put in ground connection'with the line through a releasing magnet, as solenoid b, so that the central apparatus is potentiated for automatic clearing out of apparatus B in the event of grounding of the line 10 by the hanging up of the receiver at any subscribers station on the line. The mechanism actuated by the releasing solenoid b is adapted to restore the parts 7), b and b to normal position in retarded fashion, and also to operate the pole-changing switch If to reverse the polarity of the battery 5 bridged on the line so as to efiect the release operation at the subscribers stations through the solenoids 55.

The battery 7) has one terminal connected by wire 60 with one limb 61 of the pole changing switch 72 the other spring limb 69 of which is connectible with remaining terminal of the battery through wire 63, switch 6% of the'set 7) (normally open) wire 65, switch 66 (normally closed) of the set If and wire 67. A. center contact for the two limbs 61, 62 is connected by wire 68 with line wire 10 and the outer terminals of the pole chang-set 7J3 are connected by wire 69 with the remaining wire 11. It thus becomes apparent that the battery I) will be bridged on the line only when switches 6st and 66 are both closed, and that this condition will be brought about only when the armature of magnet b has been attracted to release arm 22 and cause the closure of switch 64: and then has been retracted, again to close switch 66.

The normal circuit from line 10 to ground, provided in the apparatus B, is established from line 10 by connections 68, 62, 63, to the blade of switch 64, which has normal connection with the back contact 70, connected by wire 71, preferably through a condenser 7 2, with the winding of the solenoid 6* and to ground at 7 3. I prefer that the core of the solenoid 6* should be readily attractable and that its return movement should be retarded, for reasons that will become apparent, and to this end I illustrate a dash pot 75, freely operable in one direction and retardably movable in the other direction, governing the movements of the solenoid core. The upward movement of the solenoid core consequent upon energization of the solenoid permits the closure of normally open switch 77 which governs a local circuit including battery 6 and magnet b through wiring 78, 79, 80 and 81, the latter wire being grounded at 82 for other purposes.

As soon as the ringing generator is put in ground connection with line 10, the solenoid 5* is centrally energized, promptly permitting closure of switch 77, so that magnet b is energized, its armature is attracted throwing the switches of set 6 and permitting arm D to drop for the movement of the blade of switch set 6 A dash pot 83 permits rapid descent of the arm 6 but resists its restoration movement, and in order that the restoration of arm may not affect the position of the armature-coir trolled switch-set Z7 but may, as to its terminal movement be positively actuated by armature 57, I illustrate the said arm 6 as provided with a pointed end to be acted on by a point on the armature 57, and the switch-set b as far enough away from armature 57 not to be moved as arm 5 passes the point of armature 57.

As soon as energization of magnet 5 takes place, the switches of set 6 are shifted, opening the talking battery circuit at switch 66, closing at switch 87 a connection between wire 71 and 63 (in shunt to the normal connection 6470) and opening the switch 88. This closure of switch 87 keeps the solenoid. 72 in grounded connection with the line so that it may continue to receive the ringing current and consequently said solenoid will continue to hold the switch 77 closed as long as ringing current is transmitted over the line wire 10. .The dropping of arm consequent upon attraction of the armature of magnet b closes the battery switch 61, while opening the connections iii-70, and also closes the switch 89. These circuit changes in themselves produce no immediate result, for the battery switch 64- that is closed by the dropping of arm is in series with the switch 66 that is opened by the attraction of the magnet armature 57 and similarly switch 89 that is closed by the dropping of arm 6 is in series with switch 88 that is opened by the attraction of the magnet armature; but the closure of the switches 64:, 89, of set Z), (to remain closed until a clearing out action takes place,) conditions the circuits so that upon the retraction of the armature of magnet b a grounded circuit will be established from line 10 by wire 93 through the coil of solenoid Z), wire 94, switch 89, wire 95, switch 88, wires 96, 78, battery 6 wire 81, to ground at 82. And also it conditions the battery Z) to be bridged on the hue to provide the talking current of one polarity, through the circuit heretofore described, (60, e1, 69, 67, 66, 65, 64, 63, 62, as) as soon as the armature 57 is retracted.

Now it will be apparent that as long as the selective alternating current is maintained on the line nothing occurs in the apparatus B at central station, as no bridged circuit is provided; but as soon as the ringing current is supplied through a ground connection to the line at the calling subscribers station solenoid b is energized and remains energized until the ringing current ceases, its operation, through the intermediary of magnet 5 local to the central station, causing such circuit changes to be made that a deenergization of magnet b will, through switch-set 6 cause the bridging of talking battery 6 on the line and the closure of a ground connection from line wire 10 through the ground responsive releasing solenoid l)", battery 6 and ground at 82; the opening of switch 77 subsequent to the deenergization of solenoid 5 being retarded enough (by the provision of the dash pot 75 or other expedient) so that the calling subscriber has plenty of time to remove his receiver from the hook.

As long as the conversation period lasts nothing occurs at the central station automatic apparatus B; but as soon as an active subscriber hangs up, closing a ground connection through his ringer to the line wire 10, the releasing solenoid b is energized by the arrowhead-indicated circuit: ground at s2, 81, b 96, 88, 95, e9, 94, b, 93, 10, subscribers apparatus to ringer r and ground, the direct current from battery 5 causing the solenoid b to exert its strong pull so that through suitable releasing instrumentalities, such as the lever 97, strong spring 98 and lost-motion hook 99, it may pull the arm upward against the resistance of dash pot 8-3 sufficiently high to bring the pointed end of the arm above the point of the armature 57, to be pushed the rest of the way up by the engagement of the opposing beveled faces of the arm and armature. At the extreme end of the upward movement switch 89 is opened thereby breaking the release circuit; but during all the time the release operation at the central station is occurring the lever 97 is operating, through mechanical connections to the two spring blades 61 and 62 of the pole changing switch 6 to reverse the connections of the latter with the line, thereby to transmit to the subscribers stations direct current of proper polarity so to energize magnets 19 as to cause the closure of the switches 56, and consequently to occasion the energization of the releasing solenoids that restore the subscribers appliances to normal.

It will now be apparent that all of the operations incident to selection of any desired subscriber, to establishment of conditions for communication, and to rel-ease or clearing out of the line at the end of a call, are automatically performed without need of a central operators attention; the system thus being wholly automatic as far as intercommunication between parties on the line is concerned.

The signal-receiving and operators-control apparatus at central station may be widely varied, that herein shown at C corresponding in general functions and arrangement with the apparatus described in my copending application, heretofore referred to. The central selector apparatus S connected with the party line may be of substantially the same construction as the selectors at the subscribers stations with bridged magnet 19, release magnet 55, etc., but need have no selector setter, as a call- .initiating or settingselector will be included in the central operators cord-circuit. Preferably, the selector wheel 16 has two pins 23 and 100, respectively, controlling the switches 24 and 101, which in turn form part of the controlling means for the lamp Z, that, in the present illustration, is the central station signaling device. Pin 23 is set to close switch 21 on such step number as indicates central-station, (generally the lowest number indicated on the selector-setter), while pin 100, upon the initial movement of the selector, permits switch 101 (normally closed) to open. The spring jack j preferably has associated therewith a double-throw-switch-spring 102, and the lamp Z is connected in a circuit normally open at the switch 2 1 and including the switch blade 102 and its back contact (normally closed), such circuit being shown as energized by the battery .7), and traceable via: 103, Z, 106%, 102, back contact, 105, 24", 106, 6. her is called, this circuit is closed, and the lamp Z is caused to glow. When the operator plugs in the jack j causes the circuit to open at switch 102, so that the lamp Z is extinguished. Opening switch 102 closes the blade against its front contact which is con nected by wire 110 through switch 101 with wire 106, (forming a parallel to the two series switches, viz., 2 1 and the back-contactconnections of blade 102), As long as the Obviously, when the central numparty line is not cleared out this connection through wire remains open at the switch 101, but as soon as the clearing out takes place, owing to one of the communicating or active subscribers hanging up, and wheel 16 therefore automatically restores to normal position, the closure of the switch 100 establishes the circuit 6, 103, Z, 104, 102, front contact,'110, 101, 106, b, causing the lamp Z again to glow as a signal to the op erator to remove her plug.

The switch 070 gives the operator control over the normally-automatic apparatus so that she can either clear out the line at any time arbitrarily or can suspend the automatic operation of the ground-responsive solenoid b", to make intermittent ringing possible. To this end, the key 070, when thrown to the right, closes the switch 112 that by wires 113 and 11 1 and connects the ground wire 81 with the side 10 of the line, producing the same eifect as the hanging up of the receiver of any subscriber and so effecting an automatic clearing out regardless of whether the parties are through with their conversation or not. The key 07c, when thrown to the left, closes the switch 115 connected by wire 116 between the wire 80 and the wire 114; that is, connected in parallel with the switch 77, so that as long as the key is held to the left magnet 6 cannot be deenergized, and closure of the groundsusceptible circuit for the solenoid b is prevented.

While I have herein described only a single embodiment of my invention, for simplicity of illustration and description, to make a full disclosure thereof, it will be apparent to those skilled in the art that many changes in the details of construction and arrangement might be varied without departure from the spirit of my invention and within the scope of the appended claims:

What I claim is:

1. In an intercommunicating party-line telephone system, in combination, a line; at each subscribers station a means of supply of ringing current and an instrument set including a switch hook and a ringer controlled thereby, a selector, and electroresponsive release means therefor; and, at a central station, a source of release current supply, controlling means therefor connectiblc with the line to operate in response to depression of the switch-hook of a connected subscriber, and current responsive means, operable by the ringing current, for preventing connection of said release-controlling means with the line during continuance of ringing current and effecting connection thereof subsequent to the cessation of the ringing current.

2. In an intercommunicating party-line telephone system, in combination, a line; at each subscribers station a means of supply of ringing current and an instrument set including a switch hook and a ringer controlled thereby, selector, and electro-responsive release means therefor; and, at a central station, a source of release current supply, controlling means therefor connectible with the line to operate in response to depression of the switch-hook of a connected subscriber, current responsive means, operable by the ringing current, for preventing connection of said release-controlling means with the line during continuance of ringing current and effecting connection thereof subsequent to the cessation of the ringing current, and means to retard the said current-responsive means in its connecting operation.

in an intercommunicating, selective, party-line telephone system, in combination, a line; at each subscribers station an instrument set comprising a grounded ringer, a magneto, step-up selector for connecting the instrument with the line on a predetermined step, means responsive to magneto operation at any station to connect the mag neto of that station with the line to operate the selectors at all stations on the line, means responsive to the magneto operation at that station to establish ground return ringing circuit to the line, and electro-responsive release means for the electricallyset devices; and, at the central station, a source of release current supply, controlling means therefor adapted for connection in a ground return circuit, and means responsire to ringing current to prevent the closure of said ground return circuit during the ringing operation and to cause said closure subsequently to the cessation of the ringing current.

1. In an intercomrminicating, selective, party-line telephone system, in combination, a line; at each subscribers station an instrument set comprising a grounded ringer, a magneto, a step-up selector for connecting the instrument set with the line on a predetermined step, means responsive to magneto operation at any station to connect the mag note of that station with the line to operate the selectors at all stations on the line, means responsive to the magneto operation at that station to establish ground return ringing circuit to the line, and clectro-responsive release means for the electrically-set devices; and, at the central station, a source of release current supply, controlling means therefor adapted for connection in a ground return circuit, means responsive to ringing current to prevent the closure of said ground return circuit during the ringing operation and to cause said closure subsequently to the cessation of the ringing current, and retard means for the last said means.

In an intercommunicating, selective, partydine telephone system, in combination,

a line; at each subscribers station an instrument set comprising a grounded ringer, a magneto, a step-up selector for connecting the instrument set with the line on a predetermined step, means responsive to magneto operation at any station to connect the magneto of that station with the line to operate the selectors at all stations on the line, means responsive to the magneto operation at that station to establish ground return ringing circuit to the line, and electro-responsive release means for the electricallyset devices; and, at the central station, a source of release current supply, controlling means therefor adapted for connection in a ground return circuit, means responsive to ringing current to prevent the closure of said ground return circuit during the ringing operation and to cause said closure subsequently to the cessation of the ringing current, and mechanical retard means for the said circuit closing means.

6. In an intercommunicating, selective, party-line telephone system, in combination, a line; at each subscribers station, an instrument set including a grounded ringer, a magneto, means automatically responsive to alternating current supplied by the magneto at the calling station to select and connect the instrument sets of the calling and called subscribers with the line and to establish a ground return ringing circuit through one part of the line, and direct current responsive release means for the selector devices;

and central station apparatus comprising a source of release-current supply, means for automatically connectin said source of release current supply with the line, and means, including a grounded magnet responsive to ringing current, for automatically preventing connection of said release controlling means with the line during the continuance of, and occasioning the connection of said means with the line subsequent to the cessation of, the ringing operation.

7. In an intercommunieating, selective, party-line telephone system, in combination, a. line; at each subscribers station, an instrument set including a grounded ringer, a magneto, means automatically responsive to alternating current supplied by the magneto at the calling station to select and connect the instrument sets of the calling and called subscribers with the line and to establish a ground return ringing circuit through one part of the line, and direct current responsive release means for the selector devices; and central station apparatus comprising a source of release-current supply, means for automatically connecting said source of release current supply with the line, means, including a grounded magnet responsive to ringing current, for automatically preventing connection of said release controlling means with the line during the continuance of, and occasioning the connection of said means with the line subsequent to the cessation of, the ringing operation, and means controllable by the central operator for actuating said release controlling means independently of the automatic control thereof by said magnet.

8. In an intercommunicating, selective, party-line telephone system, in combination, a line; at each subscribersstation an instrument set including a grounded ringer; a magneto, means automatically responsive to alternating current supplied by the magneto at the calling station to select and connect the instrument sets of the calling and called subscribers with the line and to establish a ground return ringing circuit through one part of the line, and direct-current-responsive release means for the selector devices; and central station apparatus, comprising a source of release-current supply, a switch to connect the same with the line, means for operating said switch comprising a magnet, a source of current supply therefor, switch means for connecting said magnet and source of supply, a ground return connection responsive to grounding of the line at the switch hook of any subscriber, and alternating current responsive means controlling said switch-means and normally in grounded connection with the line for response to ringing current.

9. In an intercommunicating, selective, party-line telephone system, in combination, a line; at each subscribers station an instrument set including a grounded ringer; a magneto, means automatically responsive to alternating current supplied by the magneto at the calling station to select and connect the instrument sets of the calling and called subscribers with the line and to establish a ground return ringing circuit through one part of the line, and direct-current-responsive release means for the selector devices; and central station apparatus, comprising a source of release-current supply, a switch to connect the same with the line, means for operating said switch comprising a magnet, a source of current supply therefor, switch means for connecting said magnet and source of supply, a ground return connection responsive to grounding of the line at the switch hook of any subscriber, alternating currentresponsive means controlling said switch-means and normally in grounded connection with the line for response to ringing current, and means for retarding the operation of the last said ourrent-responsive means.

10. In an intercommunicating, selective, party-line telephone system; in combination, a line, subscribers apparatus at each station comprising selective means operable from any station to connect the instrument sets of the calling and called subscribers to the line and establish a ground return ringing circuit through the ringers thereof, and release means responsive to current other than the ringing current; at the central station a source of release current supply, means to connect the same with the line responsive to grounding of the line through the switch hook of any subscriber, and automatic electro-responsive means for disabling said controlling means during the continuance of the ringing operation.

11. In an intercommunicating, selective, party-line telephone system, in combination; a line; at each subscribers station a centralenergy telephone set, a selective means for selecting and connecting the instrument sets of any calling and called subscriber with the line, and direct current responsive release means comprising a polarized relay; at the central station a source of direct current supply, and means responsive to operations initiated at a subscribers station automatically to connect said source of supply with the line to establish one polarity for talking and automatically to reverse its connection with the line to establish the opposite polarity for releasing.

12. In an intercommunicating, selective, party-line telephone system, in combination, a line; at each subscribers station an instrument set including a grounded ringer, a, magneto, means automatically responsive to alternating current supplied by the magneto at any calling station to select and connect the instrument sets of the calling and called subscribers with the line and to establish a ground return ringing circuit through one part of the line, and direct-current-responsive release means for the selector devices; and central station apparatus comprising a source of release-current supply, means for connecting said source of supply with the line comprising a magnet, a source of current supply therefor, and switch means for connecting said source of supply and mag- ,1

net with one side of the line, to respond to grounding of the line at the switch hook of any connected subscriber, a magnet nor-1%;

mally ground connected with the line responsive to ringing current, switch means for breaking said ground connection and means controlled by the last said magnet controlling the two said switch means.

13. In an intercommunicating, selective, party-line telephone system, the combination of a line; and at each subscribers station an instrument set, including a grounded ringer, a magneto, a selector, a selector-setter associated with the selector for closing a magneto-including ground connection at any selected plurality of points correspond ing with the selector-settings of different subscribers, and,-normally in connection with the line and controlled by the selector,an electro-magnetic means for con necting the instrument set with the line, said means being responsive to magneto current supplied thereto by the aforesaid ground connection of the magneto with the line at any subscribers station.

'14. In an intercommunicating, selective, party-line telephone system, the combination of a line, and at each subscribers station, an instrument set including a grounded ringer, a magneto, means automatically responsive to magneto operation to bridge the operated magneto on the line, selector means bridged on the line responsive to the magneto current, selector setter means arranged to ground the magneto to one side of the line at a selected plurality of points corresponding with desired station numbers on the selector, and selector control means comprising a magnet arranged for ground con nection with said side of the line arranged when energized to break the circuit of the selector and bridge the instrument set on the line.

In testimony whereof I hereunto set my hand in the presence of two subscribing witnesses.

FRANK W. AD SIT.

In the presence of FORI JE, BAIN, MARY F. ALLEN.

Copies of this patent may be obtained for five cents each, by addressing the Commissioner of Patents, Washington, D. 0.

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