US841339A - Incoming trunk-line. - Google Patents

Description

N0- 84l,339. PATENTEDJ'AN. 15, 1907.

H. M. POST.

INGOMING TRUNK LINE. APPLICATION FILED MAR.14.1906.

rue NORRIS PETERS cm, WASHINGTON, n. c.

UNITED STATES PATENT OFFICE. I

I-IOWARD M. POS'IIOF CHICAGO, ILLINOIS, ASSIGNOR TO KELLOGG S'WITOHBOARD- & SUPPLY COMPANY, OF CHICAGO, ILLINOIS, A

CORPORATION OF ILLINOIS.

Specification of Letters Patent.

Patented Jan. 15, 1907.

Application filed March 14, 1906. Serial No. 305.993.

To all whom, it may concern:

Be it known that I, HOWARD M. PosT, a citizen of the United States, residing in Chicago, county of Cook, and State of Illinois, have invented a new Improvement in Incoming Trunk-Lines,-of which the following is a specification. V

lWIyinVentionrel-ates to telephone trunk systems for making connection between subscribers' whose lines terminate at diiierent switchboards and usually at switchboards located in ditterent central ofiices for exchanges and to signaling means between the operators and subscribers by means of which such a connection is made and the connection supervised during conversation.

such systems the opera/tors cord-circuit is usually employed for answering the calls coming at the initiatory or Astation, and in-case a subscriber is desired whose line terminates at another exchange the calling end of the operators cord-circuit is connected with the outgoing end oi a trunk-line which terminates in spring-jacks at the'A station and a c-allingplu-g at the incoming end of the trunk-line or B station. It is usual to provide a battery at each of the exchanges -for controlling the signals between the operators in making and supervising the connection, the battery at the A exchange being used to furnish current over the line to energize the. transmitter of the calling subscriber and the battery at the B exchange to furnish current to the substation-transmitter of the called subscriber. Dueto the fact that the hattery at each exchange is fur: nishing current over the line terminating at that exchange for talking purposes it is usual in such systems to sever the metallic trunk connection-between the subscribers to the flew of direct current and to inductively unite the circuit for thetransmissionof voice-currents by means of a repeating coil or by the use of condensers inserted in the ta lking-strands of the trunk-line. The use of condensers or repeating coils to inductively unite the sides of the trunk-circuit for conversation add to the cost of installation and reduce the ei Iiciency of the talking-circuit. Insuch systems also it is necessary to use a twenty-four-volt battery at 'both exchanges for energizing the transmitters of the respective slrbscri'bers.

In my invention a complete metallic circuit is provided to the voice-currents over the trunk-line from one exchange to the other without the use of intervening in ductive means, such as repeating coils or condensers, and the battery at the A ex change 18 adapted to furnish current to the transmitters .of both the calling and the called-subscriber. The cost of installation is therefore materially reduced and the talkingcircuit is coincident with the battery-circuit from the A exchange over the trunk-line to the called subscribers station.

In the accompanying drawings I have shown two subscribers lines terminating at different central oflices with an --operator"s cord-circuit at the A exchange and a form of trunk-circuitembodying my invention, which I have worked out for commercial purposes, extending between the A exchange .1 and the B exchange 2. I

At the A exchange the subscribers line is shown consisting of limbs 3 and 4E, terminating in contact-springs5 and 6 of the cut-ofi relay 7. A call-bell 8 and condenser 9 are located in a permanent bridge of the line conductors, and [a transmitter 1 0 and receiver 11 are located in a bridge of the line normally off relay when said relay is energized.v The line conductor 4 is normally connected with ground by a back contact of the cut-off relay, and the line conductor is normally connected with one side of the winding-of the line-relay 14 at another back contact of the cut-off relay, the other side of the winding :of

l the line-relay being connected with the cen:

tral-ofiice battery 15 by means of conductor 16. Multiplejacks 17 are provided at the diiierent switchboard-sections.. The linerelay is adapted'to control through its normally open contacts the circuit of the linesignal 18 in t'he usual manner.

1 The subscribers line entering the B exchange and its switchboard-section is shown the relay 50. The relay 72 has its. circuit normally open at the front contact-74 of the relay 45 and has one side :of its Winding connected with saidcontact by means of conductor and the other side of its Winding connected with. the battery 51 by means of conductors 76 and 63. A. ringing-genera tor .77 is adapted to be connected between ground and the tip side of the line by the, op eration of the ringing-key49 to signal the subscriber, a normally open contact 78 of the ringing-key being connected With-the live side of battery 51 bymeans of conductor 79 to maintain the cut-.oif-relay ,7 actuatedduring the operation of ringing.

In the operation of the system a subscriber Whose line terminates at exchange 1 signals the operator by removing telephone from the hook, 1a pathfor 'currentbeing thereby closed from thebattery 15 over conductor 16 through the line-relay 14,-the limbs of the telephone-line, including the substation ap. paratus, and to ground. atthenormally closed contact 5 of the cut-off relay .7. The.li=.1e-. relay responsive to current in this. path Will attractits armature and. light the line-lamp 18. Upon seeing the signal the operator Will insert a plug of her @cordecircuit in the answering-j ack of the line closing a path for current from. the battery 15, through the of supervisory relay 23, the sleeve'-. contacts of the inserted .plug; and jack, through the cut-off relay 7 to ground. The cut-off relay will attract its armature 5 and 6, removing the groundv from the tip side of the line. and retiring the line-signal by break.- ing the connection with the line-relay upon the sleeve side of the line, at the same time connecting the external limbs of the telephone-line with. the jack-section thereof at the front contacts of-said relay. The circuit of. the supervisory lamp 27 Will be closed at the contacts of relay 23 by current in this path;- but due. to thefact that the subscrihers receiver is off its hook ,a. path for current is completed through the substation talk ing. apparatus .overthe tip side :ofthe line, the tip-contacts of the jack and plug, tip-strand 19, and through the Winding of the supervisory relay 24'to battery, thus opening a circuit of the supervisory lamp 27 at the normally closed .contactsof said relay and pre venting the operation of said signal. The operator will then throwher listening-key 3.5 to ascertain the number of the subscriber d-e sired. Upon learning that a subscriber Whoseline terminates at station 2 is desired the operator will depress, her order-Wire key 39 and communic-atethe number of the sub seriber desired to the B operator, who Will tell the A operator What trunk-line to use in making the connection. The A operator will then insert her. calling-plug in a jack of the designated line. A pathfor current will then be closed from the battery 29 through With the test-relay32. rent will also flow from the branch containing the impedance-coil 47, over trunk-conductor 41, armature 43 of relay 45, through the supervisory relay 29", sleeve-strand 21 of the cordcircuit, the sleeve contacts of the inserted plug and jack, and the Winding of 28 and will connect the norm-ally severed portions \of the tip-strand for conversation by means of its armature .31, severing the .connection of the calling end of the tip-strand A portion of this curthe- Winding of .the high-resistance trunkrelay .46., armature 44 of relay 45., trunk-conductor 42, tip-contacts of the plug and jack,

tip-strand 1 9 of the cord-circuit, and the windj ing of the tip supervisory relay30 to battery.

The tip supervisory relay 30 does not attract its armature by current in this path, due to l the high-resistance of the trunk-relay 4'6, the

trunk-relay being preferably of fifteen-thousand ohms resistance .and the tip supervisory relay 10f one-hundred ohms. The supervisory signal :28 Would therefore be lighted throughthe closedcontacts of both supervisory relays to notify the A operator that the called subscriber has not yet responded. The trunk-relay 46 is enerziged by this flow of current attracting its armature and closing the circuit of' the guard or disconnect lamp 62,.from the live side of battery 51 over conductor 63, through the lamp 62, conductor '64, and front .contact. of relay 46, conductor54, and the armature 53 of relay 50 to ground. The signal. 62 will therefore be lighted to notify the B operator that the A operatorhas inserted her calling-plug in a jack of the proper trunk-line. The B operator, if she has not previously done so, will then test the condition of the Wanted line in'the usual manner. If the line is busy, a potential above that of ground Would exist at thesleeve contact of the j ack due to a flow of battery through the cut-oif relay 7 of the line at the switchboard-section Where such connection exists. As the tip-strand of the operators testing-terminal is normally grounded through the test relay 56, a flow of current Will'I'GSIlli? over the tip-strand 57 and the Winding of the test-relay56 to ground. The armature 58 of the test-relay Will close a path for cur rent from. the battery 51 through. the, tertiary Winding of the operators induction-coil, jincludingconductors .63, 76, 76?, and .59. Current in this path will produce aninductive click in the operators head-receiver to notify her that the line is busy. If the line is not in use, no flowof current Will result and the op erator will insert her calling-plug into the jack of the desired line. Current will then flow from battery 51 over conductors 63., 80, and 5.2., through the Winding of relay 50, sleeve-contacts of the plug and jack, and

through the Winding of the'cut-ofif relay 7 to ground. The relay 50 will attract its armatures, severing the connection of the testrelay with the tip-strand and uniting said strand for conversation at its armature 55, and opening the circuit of the guard-lamp 62 and closing the circuit of the rin ing-lamp 69 at its armature 53.v The guardamp 62 will thereby be eiiaced and the ringing-lamp 69 lighted, the circuit of the-latter signal being traced from battery 51 over conductors 63, 80, and 70, through the lamp 69, normally closed back contact 71 of relay 72, conductors 73 and 68, and contact-armature 53 of the relay 5O torground. The flowpf current through the cut-off relay will remove the connection of the line-relay 14 with line conductor 3 at contact-spring 6 of the cut-off relay to prevent the operation'of the linesignal 118 and will remove the ground connection from line conductor4 at contactspring 5 of said relay. The operator will then signal the subscriber by operating her ringing-key 49, signalingcurrent flowing from the generator 77 overthe tip-contacts of the plug and jack, line conductor 4 through the substation signaling apparatus, line conductor3, sleeve-contacts of the jack andplug,

. sleeve-strand 49, back contact 78 of the ringingfkey, conductor 79 and to ground through thebattery 51'. During theprocess of ringing the cut-off relay -7 is maintained actuated by current from the battery 51 over conductor 79, contact 78 of the ringing-key, sleeve contacts of the plug and jack, and through the winding of said relay to ground.

Upon the response of the called subscriberthe relay is operated over a path for current which-maybe traced'frombattery 51 over conductors 63,- 80, and {52, the Winding of relay 50, sleeve-contacts of theplug and jack, lineconductor 3, the substation talking apparatus, line "conductor 4, thetip-cont acts of the jack-and plug, tipestrand 47, and

through the Winding of the relay 45 to ground. The rel ay. 45 attracts its armatures, opening the circuitof. the high-resistance trunk-relay 46. and extending the circuit-of battery 29 at the A exchange from the armature 43 of the relay45-to the armature 44,.of-saidrelay, over the sleeve-strand 48 of thetrunk-cord, sleeve contacts ofthe plug and jack, limb 3 of the telephone-line, substation talking apparatus, limb 4 of the telephone-line, the tip-contacts of the jack and plu and cord-strand 47 to the armature 44 of t e relay 45. It Will thus be seen that the telephone-line of the called subscriber is substituted in the path of current from the battery 29. at the A exchange for the high-resistance trunk-relay 46 and that the battery 29 is thus utilized for furnishing energy to the transmitter at the called subscribers station over a metallic line free from inductive devices or repeating-coils of any kind and free from impedance, the conducsaid relay, retiring said si nal and notifying the A operator that the ca led subscriber hasv responded. v

The operation of the relay 45 opens the cir- 66 of said relay and closes the circuit of the relay72 at its front contact 74. The guardlamp 62 is therefore prevented from lighting when its circuit is closed at the back contact of the trunk-relay 46, and said signal remains dark. The ringing-lamp. 69'is extinguished by the'operation of the relay 72, due to current from the battery 51 over conductors 63 and 76, the winding of the relay 72, conductor 75, contact74 of relay 45, conductors 67 and 68, and armature 53 of relay 50 to ground. The circuit of the ringing-lamp 69 is broken at the back contact 71 of relay 72 and the ringing-lamp extinguished. A locking-circuit is also completed for the relay 72 fromthe battery 51 over conductors 63 and 76, the winding of said relay, front contact 71, conductors 73 and 68, and armature 5.3

of the relay 50 to ground. I

; cuit of the guard-lamp 62 at the back contact At the termination ofthe conversation,

when the subscriber at the A exchangehangs up his receiver, the circuit through thesupervisory relay 24 is opened, denergizing said relay and permitting its armature 26 todrop back, closing the circuit of the supervisory lamp 27, thus notifying the operator that this subscriber has returned ,hisreceiver to its hook. The return of the subscribers telephone to its hook at the B exchangeopen's the circuit through the relay45, permitting its armatures 43 and 44 to drop back, inserting the high-resistance trunk-relay in'the path of current from-battery 29 atthe A exchange. As previously stated, the resistance in this path is sufiicient to prevent the operation of the tip supervisory relay 30,'Wl.'li0l1 releases its armature, closing the circuit of the super visory signal 28, which is illuminated to notify the operator that the subscriber at the B exchange has returned his receiver to its hook.

It will be noted that the ringing-lamp 69 will not be lighted when the B subscriber hangs up his receiver, due to the locking-circuit of the relay 72 above described. The disconnect-lamp 62 will also remain dark, due to the fact that its circuit is opened at the back contact of the trunk-relay 46. When the A operator receiving the signal for disconnection from both subscribers removesthe plug from the trunk-jack, the trunk-re-' III from the jack of the called subscriber, restoring all parts to normal condition.

It will be understood that the several grounds mentioned in connection with the exchanges maybe one and the same or the common ofiice return and that the ground connection between the exchanges is to be I considered the equivalent of a metallic conductor. l Vhere a metallic conductor is used, the danger of disturbing earth currents, which in some localities might be present in the exchange, due to the ground connection,

. will be obviated.

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

1. The combination with a trunk-line, of a cord-circuit at the A exchange to connect with the out oing end thereof, and a called-v subscribers line terminating at the B exchange with which its incoming end is adapted to be connected, a supervisory relay associated'with the cord-circuit energized over .a circuit local to the A exchange when a connection is made with the trunk-line, a signal having its circuit closed by said relay, a second relay forcontrolling the circuit of said signal at another point, a trunk-relay in series with said second relay and of sufiiciently high resistance to prevent its operation, and means when the called-subscriber answers for substituting the called-subscribers line in the circuit in place of said trunk-relay, whereby said second relay is actuated and said signal extinguished, substantially as described.

2. The combination with a trunk-line, of a cord-circuit at the A exchange to connect with the outgoing end thereof, and a calledsubscribers line terminating at the B exchange with which its incoming end is adapted to be connected, a supervisory relay associated with the cord-circuit energized over a circuit local to the A exchange when a con nection is made with the trunk-line, a signal having its circuit closed by said relay, a second relay for controlling the circuit of said signal at another point, a trunk-relay in se ries with said second relay and of sufficiently high resistance to prevent its operation, a relay at the B exchange energized by current over the called-subscribers line, said relay being adapted to remove said trunk-relay from the circuit and substitute the resistance of the called-subscribers line therefor, to energize said second relay and extinguish said signal, substantially as described.

3. The combination with a trunk-line, of a cord-circuit at the A exchange to connect with the outgoing end thereof, and a calledsubscribers line terminating at the B exchange with which its incoming end is adapted to be connected, a supervisory relay associated with the cord-circuit energized over a circuit local to the A exchange, when a connection is made with the trunk-line, a signal having its circuit closed by said relay, a second relay for controlling the circuit of said signal at another point, a trunk-relay in series with said-second relay and of sufliciently high resistance to prevent its operation, and means when the called subscriber answers for substituting the called-subscribers line in the circuit inplace of saidtrunk-relay, whereby said signal is extinguished, and a path for direct current is closed from one exchange to the other including the called-subscribers line, substantially as described.

4. The combination with a trunk-line, of a cord-circuit at the A exchange to connect With the outgoing end thereof, and a calledsubscribers line terminating at the B exchange with which its incoming end is adapted to be connected, a supervisory relay associated with the cord-circuit energized over a circuit local to the A exchange when a connection is made with the trunk-line, a signal having its circuit closed by said relay, a second relay for controlling the circuit of said signal at another point, a trunk-relay in series with said second relay and of sufliciently high resistance to prevent its operation, and means when the called subscriber answers for substituting the called-subscribers line in the circuit in place of said trunk-relay, whereby said signal is extinguished, and a path for direct current is closed from one exchange to the other including the called-subscribers line, the path for voice-currents from the A exchange to the called-subscribers station being coincident with said direct current path, substantially as described.

5. The combination With a trunk-line, of a cord-circuit at the A exchange to connect with the outgoing end thereof, and a calledsubscribers line terminating at the B exchange withwhich its incoming end is adapted to be connected, a supervisory signal associated with the outgoing end of the trunk, means for closing the circuit of said signal when a connection is made with the trunk, a supervisory relay for opening the circuit of said signal, a trunk-relay of sufliciently high resistance to prevent the operation of said supervisory relay when connected in series therewith, and means when the calledsubscriber' answers for connecting the calledsubscribers line in the path of current from the A exchange and removing said trunkrelay therefrom to actuate said supervisory relay and extinguish said signal, substantially as described. i

6. The combination with a trunk-line, of a cord-circuit at the A exchange to connect with the outgoing end thereof, and a calledsubscribers line terminating at the B exv change with which its, incoming end is adapt-ed to be connected, a supervisory signal associated with the outgoing end of the trunk, means for closing the circuit of said signal when a connection is made with the described.

7. The combination with a trunk-line, of a cord-circuit at the A exchange to connect with the outgoing end thereof, and a calledsubscribers line terminating at the B exchange with which its incoming end is adapted to be connected, asupervisory signal associated with the outgoing end of the trunk, means for closing the circuit of said signal when a connection is made with the trunk, a supervisory relay for opening the circuit of said signal, a trunk-relay of sufficiently high resistance to prevent the operation of said supervisory relay when connected in series therewith; and a relay energized over the called-subscribers line for connect ing said line in the path of current from the A exchange and for removing said trunk relay therefrom, whereby the resistance of the .path is reduced, and said supervisory relay actuated to extinguish said signal, substantially as, described. t r

8. The combination with a trunk-line, of

a. cord-circuit at the A exchange 'to connect with the outgoing end thereof, and a-calledsubscribers line terminating at the B ex; change with which .its incoming-end; is adapted to be connected, a supervisory signal associated with the outgoing end of;.th e 1 trunk, means for closing the circuit of said signalwhen a connection is made with-the trunk, a supervisory relay. for opening-the circuit of sald signal,'a trunk-relay of sufficiently high resistance to revent the operation of said supervisory re ay when connected in series therewith, a relay energized over the called subscribers line for connecting said line in the path of current from the A exchange and forremoving said trunk-relay therefrom, whereby the resistance of the path is reduced and said supervisory relay actuated to extinguish. said signal, and a disconnectelamp having its circuit normally closed at the contacts of saidtrunk-relay, andat the contacts of said relay adapted tor-be energized over the called-subscribers line, substantially as described.

Signed by me at Chicago, county of Cook,

and State of Illinois, in the presence oftwo witnesses.

, HOWARD M. POST. Witnesses: A

' (LB. CAMP,

O. C. BRADBURY.

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