US649959A - Signal for trunk-lines of telephone systems. - Google Patents

Description

No. 649,959. Patented May 22, 1900.

C. E. SCRIBNER.

SIGNAL FOB TRUNK LINES 0F TELEPHONE SYSTEMS.

(Application filed June 17, 3898.)

(No Model.)

Witnesses: Inventor;

' @hcwlles 5; .5xmi1nwr,

by his Att Y THE mums PETERS co. movoumowaSHlNGTON. n. c.

when

ATENT CnAntEs E. SCRIBNER, or CmCAeo, ILLINOIS, ASSIGNOR To 'rini WESTERN ELECTRIC COMPANY, on SAME PLACE.

SIGNAL FOR TRUNK-LINES OF TELEPHONE SYSTEMS.

$PECIIIGA'IION forming part of Letters Patent No. 649,959, dated May 22, 1900. Application filed June 17, 1898. Serial No. 683,742. (No model.)

To (LZZ whom, it 71mg con/067w:

Be it known that I, GHARLEs E. SCRIBNER, a citizen of the United States, residing at Chicago, in the county of Cook'and State of Illinois, have invented a certain new and useful Improvement in Signals for Trunk-Lines of Telephone Systems, (Case No. e68 of which the following is a full, clear, concise, and exact description. 7

This invention applies to trunk-lines between central offices of telephone-exchange systems.

It consists in a system of visible signals, with means for operating them to enable the attendant at one terminal station of the trunkline to make, supervise, and remove connections between the trunk-line and subscribers lines with a high degree of efficiency and with a slight liability to error.

In the employment of trunk-lines between offices of extensive exchanges the greatest efficiency is attainable in using any trunkline to extend connections in only one direction-that is, from the office within which the calls originate to that wherein the connections are to be con1plctedbusiness in the reverse direction being accommodated by trunk-lines assigned solely for such connections.

The terminal of the trunk-line with which connection is made from the line of a subscriber calling is frequently referred to as the originating or A terminal, the attendant who makes the connection being termed the A operator. The other extremity of the trunk-line, which is employed in completing the connection to the line of the partycalled, is designated the incoming 01"B terminal and the attendant the B operator. The functions of the A operator consist in answering the call of the calling subscriber, making connection with the trunk-line, instructing the B operator to make the connection between a trunk-line and the line called for, supervising the connection while it exists, and removing the connection at the A terminal in response to the subscribers call for disconnection. The functions of the B operator consist in assigning to the A operator the trunk-line which is to be used, testing the line called for, making connection with the line, sending the call-signal to the station thereof, and removing the connection of the trunk-line with the line of the called subscriber in response to a signal from the A operator. The agencies employed by the A operator consist of the apparatus by means of which she makes ordinary connections; but the apparatus at the B terminal of the trunk-line is of a special nature designed to give the B operator the special information which she requires. This apparatus is so constructed, however, as to permit the operation of the apparatus at the A terminal in its usual manner in order that the A operator may not be confused in her Work by a multiplicity of signals with different meanings.

The mechanism and signals at the B terminal of the trunk-line should perform the following functions: The mechanism should provide a circuit by means of which the operator may test the line to determine whether it be free for use. A signal should be provided to indicate the response of the called party to the Call-signal; but this signal should not be again displayed during the connection. A signal should be displayed when the A operator breaks the connection with the trunkline; but this signal should be so arranged that the called subscriber can attract the attention of the B operator in the event of accidental disconnection at the A switchboard. The present invention is addressed to these various requirements and is adapted for use in connection with means for automatically controlling the different signals referring to the telephone-lines automatically in the use of the terminal telephones. Its principal features consist in the combination, with a subscribers line with means for determining the flow of current in the line in the use of the telephone and a trunk-line for temporary association with the subscribers line, of a testing-telephone at the B terminal, an electromagnetic switch for connecting the telephone with a test-contact of the plug, and a circuit for operating the switch to disconnect the telephone when connection is made with the line, a signal referring to the line of the called party, means for controlling it in response to currents in the called line determined in the use of the telephone, and a device for preventing the display of the signal after the response of the called party, a clearing-out signal, a relay associated with the trunk line, means for producing current through the relay, and circuit connections forming two paths for current therein, one controlled by a switch at the A terminal of the trunk-line and the other controlled at the station of the called line.

A further feature of the invention consists in an improved construction and mode of arrangement of the relay for controlling the clearing-out signal, whereby the static balance of the trunk-line is maintained.

The invention is shown diagrammatically in the attached drawing. This drawing represents two telephone-substations with lines entering switchboards in different central offices, a trunk-line between the oflices, and signaling mechanism in accordance with the present invention associated with the trunk line.

For the purpose of controlling signals the circuits through the call-bells at the stations at and a are interrupted, as respects continuous currents, by condensers interposed in the conductors. Thus the line-circuits are placed in condition to permit the flow of a steady current through them only when the telephones are taken from their switches for use. In other respects the equipment at the substations is of usual and well-known character. From station a line conductors l and 2 lead to spring-jacks b in a switchboard at the central office 0. Associated with the same line are a relay (1, with a secondary line-signal d controlled by it, and a cut-off relay e. Both conductors of the line-circuit are prolonged from the spring jack through the switch-contacts of the cut-off relay, after which they are united through a battery f, the magnet-windin g of relay (1 being included in the line conductor 2. The magnet of cutoff relay 6 is located in a grounded conductor 3, which leads to normally-insulated contactrings 5 of the spring-jacks b. The switchboard is furnished with the usual pairs of plugs h and 72., together with the conductors 4 and 5, uniting them, constituting the plugcircuit, and the usual calling key 71, and listeningkey h The conductive continuity of the plug-circuit is interrupted by the interposition therein of a repeating-coil 72 two serially-connected windings ot' the repeating-coil being located in each conductor of the plug-circuit, with a bridge uniting the points of junction of the pairs of windings. In this bridge of the plug-circuit a battery its is interposed. In the portion of the conductor 5 at each side of the bridge a relay is placed, these relays being designated h and 7&7, respectively, whose function is to control signal-lamps k h", respectively, referring to the different lines with which plugs h and h may become connected. The lamps arein the circuit of conductors 6 and 7, respectively, which terminate in sleeve-contacts of plugs h and h, designed to register with the contact-rings b of the spring-jacks into which they may be inserted, their other terminals being led to the free pole of a grounded battery h Relays h and h7 control the current through the lamps 7L8 and h, respectively, through the agency of shunts 8 and 9, including the switch-contacts of the relays.

A trunk-line 1O 11 extends from the office c to the office 2, wherein the line from station a terminates. This trunk-line is designed to be used in making connections from calling lines in the oflice c to lines called for in the office i. The conductors of the line terminate in contact-pieces of a spring-jack j before the A operator at the office 0, similar in arrangement and function to the springjacks of a subscribers line. The contactring I) of this jack forms the terminal of a conductor which includes a coil of resistance equal to that of the magnet-winding of relay e. At its other terminal in oflice i the conduc tors of the trunk-line are completed during the use of the line to the line-contacts of a plug is. Signal-lamps Z and m are associated with this terminal plug, the former designed to serve as a line-signal referring to the line of a called party and the latter as a clearingout signal. The circuits of these signals, together with other circuits associated with the trunk-line, are controlled by three relays n, 0, 19, respectively. The relay n has a single pair of switch-contacts a M, which become closed when the relay is excited, but its magnet is provided with two windings n and n. The relay 0 is of somewhat similar construction, having also a single pair of switchcontacts 0' and 0 and two magnet-windings o and 0 The relay 1) is provided with two switch-springs p and 19 which are actuated by the armature. The former of these has a normal resting-contact p and an alternate con tact 29 against which it is thrust when the relay is excited, while the latter spring has only an alternate contact 19 The switchcontacts 19 19 control the continuity of one conductor of the trunk-line extending to the tip is of plug 70, the tip of the plug being connected with the switch-spring p and the line conductor 10 being led to the anvil p. The normal resting-anvil p of the switch-spring forms the terminal of a conductor 13 in the circuit of the telephone (1 of the B operator. The magnet of relayp and the signal-lamp l are included serially in a conductor 1A, which leads from a battery 0' to the local contactpiece of plug 7c. The switch-spring 10 1s connected with the free pole of the same grounded .battery, and its contact-anvil 19 forms the terminal of a grounded conductor 15, which includes the signal-lamp m. The

conductor leading from --the battery to the switch-contact 29* contains a resistance-coil. This coil may have a resistance approxi mately equal to that of the lamp m.

The conductor 11 of the trunk-1ine is normally continuous to the sleeve-contact k of plug 70; but it traverses one winding 01 of relay a. The other winding a of this relay, together with the switch-contacts 'n niwhich the magnet controls, are interposed in a conductor 16, which is designed to form a shunt about the lamp Z.

The windings o o of the relay oare located in a bridge 18 of the trunk-circuit-lO 11, together with a condenser s. This bridge is connected with the free pole of battery 1'. The switch-contacts o o of this relay control a wire 17, which when it is closed forms a shunt about the signal-lamp m. The purpose of providing two windings on the relay 0 in a completed bridge of the circuit with a condenser interposed between thewindings is to maintain the static balance of the trunk line while retaining an operative connection of the relay with the line. The windings of the relay should be of many turns to attain high impedance in the magnet.

The circuit of the line conductors to the plug traverses the switch-contacts of the usual calling-key z, for bringing a generator of calling-current into circuit with the plug.

Communication may be established between the telephones of the A and B operators by means of an order-wireli), which permanently includes the receiving-telephone of the B operator at office 2, but which may be brought into connection with the telephone of the A operator through the agency of a key under the control of the latter operator.

In the operation of this system the mere removal of the telephone from its switch at station a for use brings about the display of the line-signal cl, and thus indicates a call to the operator at otlice c. In response to this call the operator will insert plug 7t into a spring-jack b of the calling line, at the same time bringing her telephone into connection with the plug circuit, and thus through oral communication will learn the subscribers ordersay for connection with station a entering the office i. The insertion of a plug into the spring-jack of a calling line completes a local circuit 6 3 of battery h whereby the cut-off relay 0 is excited and breaks the normal ground connections of the calling line. At the same time the circuit completed from battery 71 through the conductors of the plug-circuit effects the excitement of relay h, which closes the shunt 8 about the lamp it. Having learned the order of the calling subscriber, the A operator brings her transmitting-telephone into circuit with the ordenwire 19 and addressing the B operator at the office 0 instructs this operator to make connection with the line to station a. The B operator, observing that the trunk-line 1O 11 is free for use, informs theA operator that this trunleline will be used in making connection, whereupon the A operator inserts plug h into the spring-jack j. This act of the A operator completes a local circuit 7 12 of battery it by which the lamp it is lighted. The battery 7r finds as yet no circuit through the conductor 5 ot' the plug- -remains dark.

circuit and the conductor ll of the trunkline, so that the shunt about lamp It remains broken and the lamp continues to be lighted. lVhile the A operator is completing her portion of the work of making connection between the lines, the B operator, taking the plug It, tests the line to station a by applying the tip of plug 7- to the test-ring b of a spring-jack of the line called for. If this line he in use in virtue of a connection already existing with the line, a battery it or 7 will be connected with the test-rings of these spring-jacks and a current will flow to the tip of the plug and thence through the conductor 13 to earth, producing a characteristic test-sound in the telephone of the B operator. If the line be not in use, no such current will result from the application of the plug to the springjack. Finding the line free for use, the B operator inserts the plug into the spring-jack of the line called for and transmits a calling current to the station thereof by means of the key 25. Putting the plug 7tinto the spring-jack Z) closes the local circuit of battery 7* through conductors 143.116. 3, whereby the relay 1) and the lamp Z are excited. The magnetization of the relay-magnet brings the switch-springs p p against their respective anvilsp p whereby the conductor 10 of the trunk-line is made continu ous to the tip-contact of the plug 7c, and thus to conductor 1 of the linecircuit, While the connection of the tip of the plug with the operators telephone q is broken and a local circuit is closed by way of wire 15, which provides current for exciting the signal-lamp m. The current in signal-lamp Z lights this lamp, whose display indicates to the B operator that the line-circuit at the station called is open. The insertion of plug 7L into the spring-jack 7 at othce 0 provides a path for current from battery 7' through winding 0 01? relay 0, through the conductor 10 of the trunkline, and through a portion of conductor at of the plug-circuit to earth, whereby the relay 0 is excited and is caused to complete the shunt 17 about the lamp m. Hence When this clearing-out lamp m becomes connected with an excitingbattery 0' it is shunted through the iustrumentality of relay 0 and When the called subscriber, responding to the signal, takes his telephone for use, the line-circuit becomes closed at the substation, current flows from battery 7L5 through a portion of conductor 5 ot' the plug-circuit, conductor 11 of the trunk-line, and conductor 2 of the line-circuit, returning by way of line conductor 1, trunk-line conductor l0, and conductor at of the plug-circuit. The currentin this circuit excites both relays 7L7 and u at the offices 0 and 2', respectively. The magnetization of the former relay brings about the completion of shunt 9 about supervisory signal-lamp 7L9, whereby the A operator is informed of the response of the called subscriber. The magnetization of relay or effects the closure of shunt 10 of super- 4 c ients;

visory lamp Z, darkening this lamp, and at the same time provides a closed local circuit including the winding n of the relay n, whereby the relay is prevented from subsequent control by current through the trunk-line. Hence the signal-lamp Z will remain dark while the connection exists. The purpose of the lamp Z is to permit the B operator to send a second or subsequent call-signal to the called station if the first signal should receive no response or in the event of obtain ing no response to inform theA operator that the called party cannot be made to answer.

' When this condition has been reached, the

. remains at the office 0.

stations at and a are in telephonic communication. The supervisory lamps h and h in the switchboard at oflice c are dark, and thus indicate that the telephones at the terminal substations are in use. The lamps Z and m before the B operator indicate to her, respectively, that the party called for has responded and that connection with the trunk-line The replacement of the telephone on its switch at either station a or a afiects only the signals h and h, the return of either telephone to its switch being indicated by the lighting of the corresponding signal. When both signals have become illuminated, the A operator may assume that the conversation has been finished and may withdraw plugs h and hfrom the springjacks into which they are inserted. The Withdrawal of plug h from the spring'jack j breaks the circuit of battery r through the conductors l0 and 4, and since the circuit from battery 1* through the telephone-line is already broken the relay 0 is deprived of current and breaks the shunt 17 about the clearing-out lamp m. This lamp then receives current from battery 1-, which lights it, and its display instructs the B operator to remove the terminal plug of the trunk-line from the spring-jack into which it is inserted. Its removal breaks the circuit through relays n and p, whereby all the apparatus and signals are permitted to return to their normal conditions.

The invention is defined in the following claims:

1. The combination with two telephonelines, each provided with means at its station for controlling a current in the line automatically in the use of the telephone, said lines terminating in different offices, of a trunkline between the olfices uniting the said subscribers lines, a source of current at one of the offices in a bridge of the united circuits, an electromagnet at the other ofiice in the path of current therefrom to the line entering the said office, and a supervisory signal controlled by the magnet, as described.

'2. In combination with telephone -lines, each having at its station a switch for controlling a current in the line in the use of the telephone, said lines entering different offices,

of a trunk-line uniting the telephone-lines, a bridge of the united circuits and a source of current therein at the originating office, an electromagnet in the path of current therefrom to the called line at each of said offices, one of said magnets being located at each office, and a supervisory signal controlled by each of said electromagnets, as described.

3. The combination with telephone-lines having telephone-switches at their substa tions controlling currents in the line in the use of the telephones, said lines entering different offices, of a trunk-line uniting the said lines, a bridge of the united circuits at the originating office and a source of current therein, an electromagnet in the path of cur rent therefrom to the calling line, two electromagnets in the paths of current therefrom to the called line, said last-mentioned magnets being located at the ditferent'offices, and supervisory signals controlled by each of the electl'oma'g-nets, as described.

at. The combination with telephone-lines and means at the stations thereof for controlling currents in the lines in the use of the telephones, said lines entering different offices, of atrunk-line uniting the lines, abridge of the completed circuit and a source of current therein, an electromagnet in the path/of current to the calling line, two electromagnets, located at the different offices, in the path of current to the called line, a local circuit of the electromagnet at the B terminal of the trunk-line including a winding of the electromagnet there, together with switchcontacts closed by the said magnet when excited, means for closing the local circuit at another point in the use of the trunk-line, and supervisory signals controlled by the magnets at the difierent offices; whereby the supervisory signals at the A office indicate at all times the position of the telephones at the substations, while the supervisory signal at the B office is controlled from the called substation only when the telephone is brought into use, as described.

5. The combination with a trunk-line for uniting telephone-lines entering different offices, of an electromagnet having two windings connected in a bridge of the trunk-line,

a condenser interposed between the said windings, a source of current connected to one of the windings, and a clearing-out signal controlled by the electromagnet, whereby the balance of the line as respects inductive disturbances is maintained, as described.

In witness whereof I hereunto subscribe my name this 2d day of April, A. D. 1898.

CHARLES E. SCRI BNER.

WVitnesses:

ELLA EDLER, MYRTA F. GREEN.

Images