US772927A - Apparatus for through ringing on telephone trunk-lines. - Google Patents

Description

PATENTED OCT. 25, 1904.

H. M. CRANE. APPARATUS FOR THROUGH RINGING 0N TELEPHONE TRUNK LINES.

APPLICATION FILED FEB. 17. 1902.

N0 MODEL.

' ATTORNEY last-mentioned board.

" UNITED STATES Patented October 25, 1904.

PATENT Orrrca.

HENRY M. CRANE, OF NEW YORK, N. Y., ASSIGNOR, TO I/VESTERN ELECTRIC COMPANY, OF CHICAGO, ILLINOIS, A CORPORATION OF ILLINOIS.

APPARATUS FQR THROUGH RINGING ON TELEPHONE-TRUNK-LINES.

SPECIFICATION forming part of Letters Patent N 0. 772,927, dated October 25, 1904.

i Application filed February 1'7, 1902. Serial No. 94,381. (No model.)

T0 at whom it may concern):

Be it known that I, HENRY M. CRANE, a citizen of the United States,'residing at New York,

in the county of New York and State of New York, have invented a certain new and useful Improvement in Apparatus for Through Ringing on Telephone Trunk-Lines, of which the following is a full, clear, concise, and exact description.

My invention relates to trunk-lines for telephone-exchanges, and has for its object to pro vide improved apparatus and circuits whereby an operator at one terminal of a trunk-line may signal directly the substation of a telephone-line which is connected to the other terminal thereof.

In long trunk-lines it is usual to provide a repeating-coil at one of the switchboards which divides the trunk-line into two sections united telephonically through the windings of the coil. One section extends to the distant board and the other to the terminal at the local board, which is adapted for connection with subscribers lines.

In telephone systems as usually constructed the trunk-line extends from a spring-jack terminal at the answering-switchboard to a plug terminal at the trunking-board, the repeatingcoil being interposed in the trunk-line at the It is desirable that the operator at the answering or long-distance board who supervises the connection should be able to signal the called station directly through the trunk-line without being obliged to call upon the trunk operator at the distant end of the trunk-line for assistance; but ringing cannot be successfully done from the answering-switchboard through the repeating-coil for various reasons, and it has been usual heretofore for the trunk-operator at the receiving-switchboard to ring the called station at the time of putting up the connection upon the order of the long-distance operator. This division of the work of establishing and supervising the connection causes considerable confusion and loss of time, which is increased when the called party does not answer the first signal and requires to be rung a second time.

For the purpose of operating automatic disconnect-signals on long trunk-lines it has been customary to use both line conductors as one limb of an earth-completed circuit, ground branches being connected at each end of the trunk-line with both of the line conductors.

By including a source of current and the sigrial controlling magnets in these ground branches the necessity of running a third conductor in association with the trunk-line to carry currents is avoided.

My invention is especially designed for application to asystem wherein the two line conductors of the trunk-line are used in multiple to constitute one limb of the signal-circuit, as above indicated, and by means of my said invention such system may readily be equipped to permit the supervising operator at one end of the trunk-line to ring the called party directly by manipulating a ringing-key in the usual way instead of calling upon the trunking operator to do the ringing. My scheme is to provide an automatic ringing-key at the trunking-board controlled through the agency of amagnet which has two windings conductively connected, respectively,between the two limbs of the trunk-lineand the earth or other return conductor. At the distant end of the trunk-line the two limbs thereof are connected through resistances to the earth or return conductor, and a signal-circuit is thus established over the line conductors in multiple, in the undivided portion of which circuit the signal devices and source of current may be included.

The two windings of the magnet which controls the ringing-keyare arranged to act differentially under the influence of the signalcurrent which flows through them in multiple, so that the ringing-key is not actuated thereby; but the supervising operator at the distant end of the trunk-line is provided with a calling-key which is adapted to alter the flow of current in one of the windings of the differential magnet, as' by connecting one of the line conductors of the trunk-line directly to the earth or return conductor. The differential magnet is thus unbalanced and brings about the operation of the local ringing-key. whereby a suitable source of ringing-current is automatically applied to the called line.

1 will describe my invention more particularly by reference to the accompanying drawing, which is a diagram showing an ordinary telephone-line extending from a substation to a central-office answering or long-distance switchboard and there connected, through the supervising-operatofis plug-circuit, with a trunk-line extending to a trunking-board.

The incoming end of the trunk-line at the trunking-board is provided with a terminal plug, which is shown inserted in the springjack of a telephone-line, the two telephonelines being thus united through the trunkline and the connection appliances at the two s'witchboards.

The switchboard-A is the answering or longdistance board. The switchboard B is the trunking-board. The trunk-line extends in two limbs 1 2 from a spring-jack a at the answering-switchboard to a terminal plug 6 at the receiving-board. The A operator is provided with apparatusfor connecting lines together, which consists of a pair of plugs c d united by link conductors 4 5 of aplug-circuit. A calling-key e is associated with the plugeircuit and is adapted when depressed to sever the link conductors uniting the two plugs and to ground the tip of the calling-plug (Z.

The trunk-line is divided at the switchboard B by a repeating-coil g, the windings g g of said repeating-coil being connected in the circuit of the trunk-line leading to the A board and the windings g connected in the circuit leading to the trunk-plug 1).. The circuit of the trunk-line from the windings g g of the repeating-coil to the trunk-plu g b is controlled by the armatures it if of the relay or electromagnetic calling-key it. These armatures of the calling-key are connected with the two lineterminals of the trunk-plug, and the back contacts of said armatures are connected with the windings g g* of the repeating-coil g. The front contacts of the armatures are connected to the poles of a source of callingcurrent Z; The relay h is thus adapted when energized to sever the trunk-line and connect the terminals thereof leading to the trunk-plug with the circuit which includes the calling-generator 7c.

A. local circuit for the relay it, including the central battery 2', is provided at the trunkingboard. This local circuit is controlled by the armature and front contact of a differential relay m. This relay m is provided with two differential windings connected together to earth through the armature and back contact of a relayl and the winding of a relay '72,. The other ends of the diflerential windings of the relay m are connected, respectively, with l the two limbs 1 2 of the trui'ik-line through the windings y" of the repeating-coil.

The usual supervisory relay 0 1s provided on one side of the trunk-line between a pole of the battery 1 and a terminal piece of the trunk-plug. The armature of this relay is adapted when drawn up to close the circuit ol a branch conductor (3 from the tree pole of the grounded battery 1' to earth through the winding of the relay so that when the called subscriber responds by taking his telephone from its switch-hook, and so closes a brid e of the line at the substation, the supervisory relay 0 in drawing up its armature will close a local circuit through the relay and break the circuit of the ground branch, which includes the relay u. The latter relay controls a disconnect signal-lamp I, which is lighted when the relay is inert.

\Vhilc two batteries (marked 1' and I) are shown in the drawing, it will be understoml that in accordance with the usual practice but a single battery may be employed, connected as indicated At the answeringswitchboard the limbs l 2 of the telephone-line are connected together through impedance-coils r to a conductor 7, which extends to the t'ree pole of a grounded battery The conductor 7 includes the winding of a relay 1' and is itself controlled by the armature and front contact of a relay s. The relay s is included in a local circuit 8 from battery 7), established in registering contacts of the plug and the springjack of thetrunk-line. A signal 1/ is included in the portion of this local circuit 8, which is associated with the plug (Z, and a resistance r is included in the portion of said circuit which is associated with the spring-jack ol the trunkline. The relay 1* is provided with switchcontacts which control a short circuit of the resistance a, so that when the relay is excited said short circuit is closed. The relay a, which is also included in the local circuit 8, is adapted to respond to current l'rom the battery 1;) whether the resistance 1* be short-circuited or not; but the signal 1/ is adapted to respond only upon the increased current when the resistance r is short-circuited by the relay r.

The operation of the system is as follows: \Vhen the connection is lirst made from the answering-board to the called line through the trunk-line, the circuit of the grounded battery 1) is closed by relay s through the impedance-coils 1 (I to the limbs 1 2 ol the trunk-line in multiple, through the dill'erential windings of the relay in in multiple, and to ground by way of the back contact of relay 1, which is not yet excited, and the winding of relay 12. The ellects ol the two windings of relay m neutralize one another, so that the armature of said relay [is not Relay 11 1s excited and shunts drawn up.

out its controlled signal-lamp, The A operator Wishing to signal the called party depresses her calling key 6', thereby putting a ground connection on the limbl of the trunkline by way of the tip or the calling-plug 05. Current from battery 19 then divides at the impedance-coils go, as before; but the portion of the current which passes to the conductor 1 passes directly to earth at the contact of the calling-key 0 instead of flowing out over the trunk-line. The portion of the current which passes to conductor 2 flows through one ofthe windings of relay m and then divides, one part passing to earth through the relay a and the other part passing through the other winding of magnet m (in a direction to augment the effect produced by the current in the first-mentioned winding) and back over limb 1 to earth at the calling-key c. The relay m therefore draws up its armature and closes the local circuit of battery 6 though the electromagnetic calling-key 72,, which attracts its armatures 72, [L2 and connects the ringing-generator to the terminals of the trunk-plug 5, and so with the called line. Sufficient current still flows through the relay n to excite it and prevent the display of the disconnect-signal. The long-distance operator at the A board may thus ring the called station as long or as frequently as desired without being obliged to call upon the B operator for this purpose. When the called party responds, the armature of relay 0 is drawn up and closes a local circuit through the relay Z, which breaks the earth connection of the windings of the differential relay m and connects the relay n in a local circuit with battery 71 to maintain the same excited. The trunk-line is thus freed from connection with the earth at the B switchboard during conversation:

The operator at the A switchboard supervises the connection and receives the disconnect-signals when the conversation is finished. After the connection has been put up and until the called party responds the circuit of battery 10 will be completed through the relay 1? to earth at the B switchboard by way of the armature and back contact of the relay Z. Upon the response of the called party, however, the relay Z, being excited, breaks this circuit, so that the relay risdeenergized and allows its armature to fall back, thus opening the short circuit about the resistance '0. The current through signal a being out down by the introduction of this resistance 0 into the circuit, said signal becomes inert and remains inert during the conversation. When, however, the called party hangs up his telephone, the supervisory relay 0 at the switchboard B will be deenergized, breaking the circuit through the relay Z, whereby the armature of the last-mentioned relay is permitted to fall back and reestablish the circuit from battery 12 through the relay r over the trunk-line to earth. Relay r shortcircuits the resistance '0, which is included in the circuit of the signal at, so that the signal responds to the increased current and displays a disconnect-signal. A clearing-out annunciator-drop -is also provided in a bridge of the A operators plug-circuit to receive a disconnect-signal from the substation of the calling-line.

When the A operator in response to the disconnect-signal removes the plug from the trunk-line jack, the battery connection with the trunk-line is broken at the switch-contacts of the relay 8, and the relay n is deprived of current, so that it allows its armatureto fall back and open the shunt around the disconnect-lampt at the B switchboard. Said lamp 2, thus receives current for its illumination and indicates to the B operator that the trunk connection may be taken down.

Having th us described my invention, I claim as new, and desire to secure by Letters Patent, the following:

1. The combination with two telephoneswitchboards and telephone-lines centering at each board, of a trunk-line extending between the boards and means at each board for connecting the trunk-line to other lines, a relay at one of the boards, a source of calling-current and means controlled by said relay for applying the calling-current to the telephoneline which is connected with the trunk-line at that board, differential windings for said relay connected respectively with the limbs of the trunk-line, means for producing aflow of current in both limbs of the trunk-line, and a switch at the distant end of the trunk-line for diverting current from one of the differential windings of the relay, substantially as set forth.

2. The combination with a metallic-circuit telephonetrunk-line, of an electromagnetic calling-key at one end thereof, a local circuit for said calling-key including a source of current, a relay controlling the said local circuit,

differential windings for said relay connected respectively with the two limbs of the telephone-line, means for producing a flow of current in both limbs of the trunk-line, and

a switch at the distant end of the trunk-line adapted to alter the flow of current in one of the differential windings of the relay, as by shunting the same, whereby the calling-key at one end of the trunk-line may be actuated by moving the switch at the distant end, substantially as set forth.

3. The combination with two switchboards and telephone-lines centering at each board, of a metallic circuit trunk-line extending between the boards and means at each board for I nected With the two limbs of the trunk-line, respectively, and with a return-conduetor, as the earth, means for producing a flow of current in both limbs of the trunk-line, and a switch at the board distant from the callingkey, controlling the connection of one limb of the trunk-line circuit with the earth or other return-conductor, whereby the calling-key may be actuated from the distant board, substantially as set forth.

4. The combination with a metallic-circuit telephone trunk-line, of an electromagnetic calling-key at one end of the trunk-line, a local circuit for said calling-lrey including a source of current, a relay controlling the said local circuit, difl'erential windings for said relay connected respectively with the two limbs of the telephone-line and having a common earth connection, a grounded source of current at the distant end of the trunk-line connected with the two limbs thereof in multiple, impedance-coils q q interposed between the two limbs of the trunk-line and a source of current, and a switch 6 adapted to connect one of the limbs of the trunk-line to earth, whereby the differential relay may be excited and the calling-key actuated from the distant end of the trunk-line.

5. The combination with a metallic-circuit trunk-line, of a callingdiey atone end thereol', an electromagnct for actuating the callingkey, two diiierential windings for the magnet connected respectively between the two limbs of the trunk-line and a third conductor, said third conductor extending to the distant end of the trunk and there being connected with the two limbs of the trunk-line, a source of current in the circuit of the third conductor, a switch in the circuit of the third conductor at one end of the trunk-line, a signal device in the third conductor at the other end of the trunk-line, said signal device being controlled by said switch, and a second switch at the end of the trunk-line distant from the calling-key, adapted to effect the actuation of the callingkcy by altering the flow of current in one of the windings of its control]ing-magnct, whereby the calling-key and the signal device may be independently operated.

In witness whereof I hereunto subscribe my name this 27th day of January, A. .l). 1902.

HENRY M. CRANE.

itnesses:

Pnnsco'r'r H. CooLIDen, HENRY F. \Vnrrn.

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