US712801A - Switchboard and supervisory signal circuit. - Google Patents

Description

- Patented Nbv. 4. I902. D. S. HULFISH.

SWITQHBO ARD AND SUPERVISORY SIGNAL CIRCUIT.

(Application filed July 1, 1902.)

(No Model.)

ATTORNEY.

THE Mom's wzrzns 00., Ppomgnum wnsumamu. n. q.

NITED STATES ATEN'I OFFICE.

DAVID S. HULFISH, OF CHICAGO, ILLINOIS, ASSIGNO'E TO AMERICAN TELE- PHONE AND TELEGRAPH COMPANY, OF BOSTON, MASSACHUSETTS, A CORPORATION OF NEW YORK.

SVVITCHBOARD AND SUPERVISORY SIGNAL CIRCUIT;

SEEGLFIGATXON forming part of Letters Patent N 0. 712,801, dated November 4, 1903i.

Application filed July 1, 1902. Serial No 113,972. (No model.)

[ a whom/ it may concern: plugs, and the said local circuits are com- Be it known that 1, DAVID S. HULFIsH, re- 'pleted through suitable resistance when the siding at Chicago, in the county of Cook and plugs areinserted in main-circuitswitch-sock- State ofIllinois, have invented certain Imets. Signal devicesgenerally small glowprovements in Switchboard and Supervisory lamps, one associated with each switch-plug 55 Signal Circuits, of which the following is a are included in these local circuits, and the specification. said lamps are provided with controlling- Thisinvention relates to the central-station shunts extending around them and leading apparatus of telephone-exchanges, and espethrough the local switching or contact points cially to'the construction and arrangement of of corresponding relays, also one for each 69 the lamp or other signals which are associated plug, which relays are connected in the mainwith switch-cords and which enable the opcircuit switch-cord loops. The relays are erators to exercise intelligent supervision thus responsive to the operation of the hookover calls and over connections between two switches pursuant to the removal and replacesubstations at any or all stages of the Operament of the receivers at the respective substa- 6; tion. tions, and by closing and opening the shunt- In standard central-station telephone syscircuits in response to such operation permit tems and apparatus as at present generally the displayof the lamp-signal associated with constituted and employed the main or subany plug when the receiver is on its hook at station circuits when inactive are conduc-. the substation of aline in whose socket such 70 tively open or discontinuous, but when the plugisinserted, but causes the Same to remain substation-receiver is taken from the switchundisplayed or be withdrawn when the said book are closed by the action of said switch, receiver is removed from the hook. These which therefore controls the continuityot the lamp-signals are termed supervisory sigcircuit. nals and the relays controlling them su- 75 The Switch-cords whereby any two main p'ervisory relays. The displayof the signal circuits may be united at the central station associated with either plug indicates, thereare provided with terminal switch-plugs, one fore, that the receiver at the substation of the of which, usually termed the answeringline directly connected with such plug is on plug, isinsertedin aswitch-socket of the callits hook, and the absence of such signal dis- 8o originating substation-circuit,while the other, .play indicates that the receiver has been rewhich may be termed the companion plug, moved from the hook. Such indication has, is Similarly placed in a switch-socket ot' the however, been found insufficient, since in the called or wanted main circuit. Each switchcase of a called subscriber the signal is the 5 cord has two main-circuit conductors, which same whether the said subscriber has failed 85 when the plugs are thus inserted extend reto respond at all by taking up his receiver or spectively between the main conductors of whether he has answered by such action and the two substation-circuits concerned; but has thenforsomereason replaced hisreceiver, as the working battery or other source of curyet in the former instance the operator'is re- 0 rent-supply is bridged between the said mainquired to ring up the wanted substation again 0 cord conductors it follows that the main-cirand in the latter case is not so required. To cuitconductors of the switch-cord are formed remedy this insufficiency and the confusion thereby into two main-circuit loops, each liable to be caused thereby and to provide closed at its inner extremity through the said fully discriminative signals are the objects of 5 source and each extending to its respective this invention. 5 plug and adapted thereby to constitute a ter- To this end the invention consists, mainly, minal loop, through which the main circuitin in providing an additional local-circuit conwhose switch-socket the plug is inserted is or ductor for the companion plug, in controlling may be closed. The Switch-cord system also this by the relay of said plug, and-in an elechas a local-circuit conductor for each of its tromagnetic switch connected therein and too adapted when actuated by the operation of said relay to connect both signals in parallel branches of the local circuit of the answeringplug, to extend the controlling-shunt of the supervisory signal of the said answering-plug and establish said shunt around both-signals, and to lead said shunt thusextendedthrough the local or contact points of both supervisory relays, so that the de'e'nergization of either relay pursuant to the replacement of the receiver on its hook at the substation of the circuit containing such relay and the consequent opening of the extended shunt-circuit will cause the simultaneous display of both supervisory signals and will thus furnish an unmistakable signal for disconnection which cannot by any possibility mean anything else.

It consists also in certain details of construction and arrangement of the said circuit connections and apparatus, and provides also that the said electromagnetic switch shall after it has been energized be enabled to transfer its own local circuit from the contacts of the companion plug relay to a new path through contacts controlled by its own magnet, thereby leaving said relay free to participate in the direct control of the supervisory signals.

The drawing which accompanies and illustrates this specification is a diagram representing a modern telephone-exchange system of substation-circuits converging to a central station, where by means of a suitable switching apparatus they maybe united in pairs for through communication.

The several substation-circuits are exemplified by two main circuits L L and the switching apparatus is exemplified by a single switch-cord circuit or system IV.

In the said drawing, A and A represent the substations of the main circuits L and L respectively, and M is the central station. The substation apparatus is of standard type, as is also the call-receiving portion of the central-station appliances. The substation apparatus comprises, as usual, the callbell d, the condenser c, the telephone-transmitter T and receiver t, and the suspensionswitch 8, havingahook termination, on which, as shown at substation A the receiver is hung when not being used. Then the switch 3, in virtueof the presence of the telephone on the hook, is in its lower position, the circuit is conductively open, the condenser 0 being interposed therein, but the bell (l is of course readily operated through the condenser by the alternating call-currents of the regular generator; but when the receiver is taken from the hook and the switch 3 moves to its upper position the circuit is conductively closed through the switch-lever, its contact-stop y, and the station-telephones.

J J are the spring-jacks or switch-sockets of main circuit L, and J J the sockets of main circuit L and each contains a contact connection of both main wires a b or a b of the circuit. In the sockets J J 3 3 are the contact-springs extending from condutor b, and 4 4 those which are branched from conductor a. The socket-frames e of the said switch-sockets are grounded through conductor 5 and through an appropriate resistance, which, as shown, may take the form of a cut-off relay R operating when excited to sever the normal line-terminals 8 and 9 at the points 6 and '7when the circuitis transferred to a switch-cord by the insertion of a plug in any one of its sockets. The said conductor 5, extending from the switch sockets to ground G or return, forms part of local circuit f, which includes the said cut-oft relay or resistance and which, as presently to be described, is associated with the answering switch-plug and the corresponding supervisory signal. The normal terminals of the substation-circuits are as usual.

The main conductor aextends through the cut-off relay-contact 6 and extension-conductor to earth, and conductor 1) extends through cut-01f relay-contact 7, the winding of line signal-relay R and the source of cur rent E to earth. The said line-relay R controls the call-signal D in a normally open local circuit 12 of the generator E which extends through the armature h of the line-relay and its front contact 10 and also may include an appropriate resistance j. The said signal is shown as being a small glow-lamp, and the said generator E may be and generally is a voltaic battery-and the same battery as that to which reference will presently be more particularly made as being that which supplies current for the transmitters and signals for lines which are in use or active operation.

P is the answering switch-plug, and P the companion switch-plug, of the switch-cord circuit or system W; I, the usual split winding repeating induction-coil; 25 a receiver symbolizing the operators telephone apparatus; 70, a ringing-key, and F a call-current generator. The tip and ring contact-surfaces p and p of the two plugs, arranged when the plugs are inserted in the sockets J to register and make contact with the springs 3 and 4, respectively, of said sockets, are united by the main cord- conductors 15 and 16. The battery E, having the usual ground connection 26, is bridged between the said conductors at the middle of the two windings of the split repeating-coil I, and the main cord conductors are thus divided into main-circuit loops X and Z, the former associated with the answering-plug, P and the latter with the companion plug P and each constituting the terminal loop or section of the main or substation circuit with which its associated plug is or is about to be connected.

R is the supervisory relay associated with the answering-plug end of the cord-circuit, and R the supervisory relay of the companion plug. These relays are in the main-circuit loops Xand Z, respectively, and of course when the plugs are inserted in the sockets of substation-circuits L and L are brought directly into the said circuits and are thereby made subject or responsive to the operation of the substation-switches s and 8 The signal S, preferably also a small glowlamp, is connected in the local-circuit conductor 20, which forms part of the local circuit f, the said circuit being completed when the plugP is inserted in a socket J of the calling-line by way of the frame-piece e of said socket and cut-off relay R The said local-circuitconductor extends from the ungrounded pole of battery E through said lamp-signal S and a reducing-resistance r to the sleeve-contact piece p of the plug P. The signal S associated with the companion plug P in like manner, is in a similar local circuit f, the cord conductor 20 whereof branches from conductor 20 at any convenient point 24. This circuit may also have a steadying or reducing resistance 0"" H is a normally open shunt around the signal S, beginning at point 24 of conductor 20, ending at point 17 of the same conductor, and leading by conductor 26 through the restingcontacts n and 27 of a device hereinafter to be described and byconductor 22 through thecontact-points 18 and mof the supervisory relay R and through resistance r. This shunt is therefore controlled by the said relay, being closed when the relay is excited and attracts its armature and opened when the said relay is not excited, and is thus enabled to control the display of the signal S,

With the companion plug is associated a second or auxiliary local circuit W, the cord portion of which circuit normally extends from any convenient point 19 on conductor 22 of the controlling-shunt H by conductor 30 through the contacts of supervisory relay R to any point 53 on the ordinary local-circuit conductor 20 on the plug side of the resist ance W.

N is a switching-relay or electromagnetic switch, whose magnet-coilis connected in the said auxiliary local circuit. The said electromagnetic switch is shown as having two armatures n and o, controlling different sets of switching-points. Obviously, however, if desired, one armature carrying two switching-levers or one armature lever carrying both sets of contacts could readily be arranged. The armature 0' makes no electrical contact in its quiescent position, but when attracted forward establishes contact with its front stop 28. The armature 7% is adapted to make electrical contacts in both quiescent or back and active or. forward positions and is provided with contiunity-preserving springs q and u, whereby it is enabled to maintain its contact on either side closed until that on the other side is established. Its back contact between armature n and point27 is in the circuit of the controlling-shunt H, and the normal circuit of said shunt, as hereinbefore stated, leads therethrough, so that as long as the electromagnetic switch remains unactuated the said normal circuit of the shunt H is maintainedthereby. The front contactstop 29 of armature n is branched from conductor 30 of theauxiliary local circuit within which the magnet of the electromagnetic switch is connected, When, therefore, the said switch is operated and the said armature is attracted forward, contact is established between the contact-spring u of said armature and stop 29.

From a point 42 .on the conductor 20 of the regular local circuit f of plug P a branch connection 32, passing through the contacts 28 and o of the electromagnetic switch N, extends to a point 43 on the cord conductor 20 of local circuit f, associated with plug P. Since the said points 28 and o are normally out of contact with one another, this branch connection is normally open. VtThen closed at the said contacts, however, by the operation of the switch N, it forms the principal portion of a parallel branch of the said local circuit f of plug P and includes thesupervisory signal S which is thus connected in parallel with signal S, the said parallel branch now extending from point 24 by conductor 20 to the said signal S thence to point-42, contacts 2S and o, and conductor 32 to point 43 on conductor 20 of local circuitf. The portion 30 of the auxiliary local circuit extending between point 19 and the forward contact-point 29 of armature n of the switch N and passing through the contacts 51 52 of the supervisory relay R becomes when said electromagnetic switch is operated a continuation of the shunt H,which is thus extended around both of the two signals S S connected in parallel, and exercises control over both, and since the said shunt nowincludes the contacts of both relays, so that it is controlled by both relays, it follows that thedeenergization of either relay pursuant to the replacement of the receiver at the substation of either line willoperate both of the said signals. Thus the display of both signals together can only occur when after both receivers have been removed from their respective switclrhooks one or both are replaced.

The operation of the electromagnetic switch has still another result. It transfers its own auxiliary local circuit from its original path through the contacts 51 and 52 of supervisory relay R to the forward contacts to and 29 of its own armature n, and thus becomes independent of said relay-contacts.

The operators telephone t is adapted to be bridged in a well-known manner between the main conductors 15 16 of the cord-circuit by means of the usual listening-key, which is conventionally indicated by the contacts 14.

The ringing-key Z6 is adapted when pressed to sever themain conductors of the main loop Z by separating the springs o w from the contact-points 34 and 35 and to connect the former'. to. the terminal contacts 32 and 33 of the call-generator F for the purpose of sending a ring or call-signal over circuit Z to the substation A In these devices the several re- ICC sistances should, of course, be proportioned on proper engineering principles. Good results will be attained by giving to the cut-off relays a resistance of about thirty ohms, the resistance-coils r and r eighty ohms, and the shunt resistance r twenty ohms. In the operation of these devices a call coming in over substation-circuit L will be responded to by inserting the answering-plug P into socket J Since the receiver at the calling-substation has already been taken from the hook to give the call and order, the circuit of battery E is closed through the relay R, which therefore is excited. At the same time the local circuit fis closed from the battery E to ground by way of the signal-lamp S, the socket-ring c, and the cut-off relay R but the said signal S isnotdisplayed,because thecontrolling-shunt H thereof is closed around it by the relay R, which being excited has attracted its armature and brought its contacts on and 18 together, the shunt for the present being maintained through the armature and back contact n and 27 of the switching-relay N. The signal S though notdisplayed remains under the control of the switch 3 at substation A in the usual way, so that if the subscriber at any time prior to the culmination of the call wishes to attract the attention of the central operator he may do so by oscillating his switchlever, which will cause the signal to operate the signal intermittently. The calling subscriber having stated his order plug P is placed in a switch-socket of the circuit of the wanted. substation, and the local circuit f of said plug being thereby closed current flows through signal S and causes the same to be displayed. The call is now sent over line L by operating the ringing-key It. At this juncture signal S remains undisplayed, because the receiver 25 at substation A has been taken from the hook to send the call and give the order and has not been replaced, and signal S is displayed because its circuit 5 f? is closed through the local contacts of the plug P and socket J and its display continues until the subscriber at A responds to the call by removing his receiver from the hook 3 but when the receiver is lifted from the switch-hook the main circuit is conductively closed through the telephones, and the current from the source E circulates therein and energizes the supervisory relay R which bringing its contacts 51 and 52 together closes the auxiliary local circuit 7L2 and causes the operation of the electromagnetic switch N included therein. The said electromagnetic switch then attracts both armatures by armature 0 closing the branch 32 of the local circuit f of plug P through signal S and thus placing the two signals S and S in parallel with one another between the points 24 and 43 and by armature n uniting the spring and fixed contacts a and 29 and immediately thereafter separating the spring contact (1 from the backstop 27, thereby closing the extended shunt-circuit around both signals and through the contacts of both relays R and R in series and transferring the control of the switch N from the contacts of relay R to its own contacts to and 29. As has been indicated, the signals S S though now undisplayed remain during the pendency of the communication under the control of the substation-switches s 5 in such manner that the restoration of the receiver to the hook at either substation will cause the display of both signals S S at the same time, for when either subscriber hangs up his telephone his main circuit is opened at the switch, and the corresponding relay R or R becomes deenergized, and as the shunt around both lamps leads through the contacts of both relays it will evidently be broken by the retraction of the armature of either relay. Receiving the disconnection-signal the operator pulls the switch-plugs from their sockets. The circuit maintaining the magnetization of the switching-relay N, which upon the initial operation of the same was formed through the forward contacts u and 29, through the winding of said relay, and by conductor 30 to the sleeve contact of plug P returning thence by way of the switch-socket earth branch, which contains the cut-out relay of main circuit L is broken by the withdrawal of the said plug P and the excitement of the magnet of the switch-relay N ceases, permitting it's armatures to move to their original positions, and thus restoring all portions of the switch-cord apparatus to their normal or resting state.

Thus by means of my improved supervisory switch-cord circuit a new and distinctive signal is obtained from the same two lamps viz., the display of both at the same time-to indicate the requirement of disconnection, even though at the close of the communication but one of the substation-receivers be replaced upon its book.

Having now fully specified my invention and its mode of operation, I claim 1. In a telephone-system switchboard apparatus, the combination of answering and companion switch-plugs, united by a switchcord comprising a main-circuit loop and. a local signal-circuit conductor for each plug; a supervisory relay included in the main-circuit loop of each plug, a supervisory signal for each plug in the local circuit thereof; a shunt-circuit around the answering-plug signal and including the switch-points of the answering-plug relay; and means controlled by the companion-plug relay and operating pursuant to the excitement thereof to connect both of the said supervisory signals in parallel branches of the answering-plug local circuit, and to connect the switch-points of both supervisory relays in series in said shunt-circuit, whereby both signals are rendered responsive to the denergization of either relay; substantially as described.

2. In a telephone-system central-station apparatus, the combination with answering and of; a supervisory signal associated with each plug in the local circuit thereof; and a shuntcircuit around said signal normally controlled by the relay of the answering-plug only; of a normally open branch circuit parallel to the local-circuit conductor containing, said answering-plug signal, adapted when closed to include the supervisory signal of said companion plug; a normally disconnected continuation of said shunt-circuit adapted to extend the same through the contacts of the companion-plug relay and to shunt the companion-plug signal also when thus included in said parallel branch; and an electromagnetic or relay switch controlled by the said supervisory relay ofthe companion plug, and adapted when actuated to close said parallel branch through said companion-plug signal, and to extend said shunt through said continuation; whereby both supervisorysignals may be made responsive to either supervisory relay, substantially as described.

3. Ina telephone-system switchboard apparatus, the combination of answering and companion switch-plugs united by a switchcord comprising a main-circuit loop for each plug, a local signal-circuit conductor for each plug, and an auxiliary local-circuit conductor for said companion plug; a supervisorysignal associated with the answering-plug and connected in the local circuit thereof; a normally incomplete branch of the said answering-plug local circuit arranged in parallel with the signal thereof; a second supervisory signal connected in the local signaling-circuit of the companion plug and also in the said normally incomplete branch of the answering-plug local circuit; a shunt-circuit normally around the said first-named signal but adapted when the said branch is completed to be extended also around the said second signal included therein; a supervisory relay in the main-circuit loop of the answering-plug and adapted to alone control said shunt as normally constituted; a second supervisory relayin the maincircuit loop of the companion plug normally controlling the said auxiliary local circuit but adapted when the said shunt is extended around both signals to control the same jointly with said first-named relay; and an electromagnetic switch in said auxiliary local circuit maintainingwhen quiescent the normal circuit of said shunt, but adapted when excited to close said normallyincomplete branch through said second signal, and to extend the said shunt-circuit around both signals and through the contacts of both relays; whereby both signals originally responsive each to its own relay alone, are made responsive to the deenergizat-ion of either relay; substantially as described.

4:- In aswitch-cord-circuit system, the cornbination with the answering and companion switch-plugs of said cord; the standard main and local circuits of the said plugs respectively; the supervisory relays and lamp-signals connected in said main and local circuits respectively; and the standard controllingshunt of the signal-lamp of the answeringplug local circuit; of an auxiliary local circuit associated with said companion plug; and an electromagnetic switch included therein, responsive to the supervisory relay of said companion plug; the said switch being organized when operated, to connect said signals in parallel branches of the answering-plug local circuit, to establish said controllingshunt around both'signals, and to connect the contacts of both supervisory relays in series in said shunt-circuit; whereby the signal: lamps normally responsive each to its associated relay are brought into such relation that both are responsiveto either relay; substantially as described.

5. In a telephone-exchange system, the combination of two main or substation circuits, viz: acalling and a called circuit, both adapted to be closed and opened by the substation hook-switch as the receiver is taken therefrom 'or replaced, and both having switch-sockets comprising main and local circuit switch contacts at the central stations;'

a switch-cord with answering and companion switch-plugs, and containing main conductors with a source of current bridged between them and dividing the same into loops, one for each plug, and a local signal-circuit conductor for each plug; a supervisory relay in each main-circuit loop responsive to the operation of the respective substation switchhooks; a supervisory signal for each plug in the local circuit thereof; a shunt normally arranged around the answering-plug supervisory signal and controlled by the relay of said answering-plug main loop, but having an alternative circuit around both supervisory signals, and through the switch contacts of both supervisory relays; a normally open branch circuit in parallel circuit with the supervisory signal of the answering-plug and adapted when closed to include the other signal; and an electromagnetic switch or switching-relay controlled by the supervisory relay of the companion plug, the said switchingrelay having two positions, and being adapted in its quiescent position to maintain the normal circuit of said shunt, but in its active position to close the said parallel branch circuit through said companion-plug signal, and to establish the alternative circuit of said shunt; substantially as and for the purposes specified.

6. Inatelephone-exchange,acompoundcircuit extending between two substations and comprised of two substation-circuits switched together at a central-station switchboard on the call of oneof them, and having a battery bridged between its main conductors at said central station; aswitch at each station each controlling the conductive continuity of its own component circuit; a relay at the central station in each of the said component circuits responsive to the switch at the substation of its own circuit only; alocal circuit associated with each component main circuit; a supervisory signal included in each local circuit; an auxiliary local circuitassociated with, and leading through the contacts of the relay of the called component main circuit; a shuntcircuit for the signal of the calling component circuit leading through the contacts of the corresponding relay; a continuation thereof normallydisconnected but adapted to extend the same around both signals and through the contacts of both relays; a normally incomplete branch for the local circuit associated with the calling component main circuit in parallel with the signal included in said local clnde the signal of the other local circuit; and an electromagnetic switch connected in the said auxiliary' local circuit, and adapted in its quiescent position to maintain the normal circuit of said shunt, but when operated to establish parallel connection of the said two signals, to transfer its own local circuit from the contacts of the called-circuit relay to contacts controlled by its own magnet, and to extend the shunt-circuit through the said continuation thereof; substantially as described.

In testimony whereof I have signed my name to this specification, in the presence of two subscribing witnesses, this 20th day of June, 1902.

DAVID S. HULFISH. Witnesses 1 L. G. RICHARDSON,

A. B. RAYMOND.

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