US772900A - Telephone-exchange system. - Google Patents

Description

PATBNITEDVOGT. 18,1904, J. L. MoQUARRIE. TELEPHONE EXCHANGE SYSTEM.

APPLICATION FILED JAN. 14, 1901- no MODEL.

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JAMES L. MCQUARRIE, or CHICAGO, ILLINOIS, AssIe'NoETo THE WEST- Patented October is, 1,904.

PATENT OFFICE.

ERN- ELECTRIC COMPANY, OF CHICAGO, ILLINOIS, A CORPORATION OF ILLINOIS.

TELEPHONE-EXCHANGE SYSTEM.

SPECIFICATION forining part of Letters Patent No. 772,900, dated October 18, 1904.

' Application filed January 14, 1901. Serial No. 43,279. (No model.)

My invention relates to a telephone-exchange system, and more particularly to a system wherein a private branch telephoneexchange is provided instead of a single instrument at a substation of a large exchange. In large cltles It is not uncommon that a businesshouse-requiring considerable tele-.

phone service to other parts of the city and also requiring alocal telephone system for communicating between its departments will have a large number of telephone instruexchange.

Inents distributed at various points throughout the premises, and all of said instruments will be connected'with a private branch exchange-switchboard. One or more trunklines corresponding to ordinary subscribers lines will then be provided between the private branch exchange and the main centralv office. With such a system when a subscriber of the large exchange desires communication with a particular department of the business-house having the private exchange he will call up the central oflice in the usual way and ask for connection with the private The central-ofiEice operator will then [make connection with the trunk-line leading to-the private exchange and applycalling-current. The private-exchange operator upon perceiving the signal thus transmitted will insert her answering-plug in the spring-jack of the trunk line, at the same time connecting her telephone in circuit. She will then inquire of the calling subscriber the name of the person or department wanted and having obtained this information will complete the desired connection. When a person at one of the instruments of a private exchange desires a connection with a subscriber of the large exchange, he will transmit his order to the private-exchange operator, who will connect his instrument with the trunk-line leading to the central oiiice, whereupon the central-office operator will answer the call in the same manner as though it came from an ordinary substation. The connection of one of the private-exchange instruments with the main central office will not, of course, interfere with local communication between any other two instruments of the private exchange.

In telephone systems of the character described it-is desirable that all the substations of the private exchange should have substantially the same equipment; but it is also desirable that through connection to the large city exchange should be permitted only to a certain few designated instruments. The object of this of course is to limit the use of the trunk-lines strictly to business purposes, and so to reduce the number of trunk-lines required. Where the common battery system is used, while alocal source of current is provided at the private-exchange otfice for local connections it is desirable that for through connections to the cityvexchange the substation-transmitters should be operated bycurrent derived from the main-exchange battery-that is, the battery bridged across the central office operators plug circuitthesame as though connection were had Irom the central oflice to an ordinary individual line.

The object of this invention is to provide a telephone system in which these results are attained.

In accordance with my invention an electromagnetic switch is connected with the private-exchan'ge-operators plug-circuit, which is brought into operation by plugging into certain of the lines but not into others to disconnect or apply the local source of current for talking. Blocking mechanism is also provided for preventing telephonic communication, as by positively rendering the trunkline or other telephonic circuit inoperative when connection is made between the trunkline and a substation which is not designed to be connected therewith.

My invention further contemplates improved means at the private-exchange ollice for controlling signals at the central ofiice of the large exchange.

My invention is illustrated in the accompanying drawing, which is a diagram showing a trunk-line extending from acentral ofiice to a private-exchange ofiice and also showing two subscribers lines of the private exchange, together with the apparatus involved in connecting and disconnecting lines, the system being constructed and equipped in accordance with my invention.

The trunk-line, which extends in two limbs or line conductors 1 2 from the central ofiice A to the private-exchange office B, is provided at the central oifice with the usual line-signal apparatus for indicating a call. Such signal apparatus is similar to that used on all subscribers lines of common-battery exchanges and does not require detailed description. At theprivatebranch-exchange office B the limbs 1 2 of the trunk-line terminate in line-springs a 0/ of a spring-jack a. A line-indicator or drop I) is connected in a terminal loop of the trunk-line by way of two contacts, against which the line-springs a a? normally rest when no plug is inserted in the jack. Condenser b is included in the terminal loop containing the drop 5, so that the circuit of the central-office line-signal battery will not be closed through said terminal loop. The continuity of the two conductors 1 2 is controlled by a blocking-relay 0. Said relay normally maintains the continuity of the trunk-line, but is adapted when excited to sever both limbs thereof. The magnet-winding of the relay 0 is included in a conductor 3, which extends from the test-ring or third contact-piece a of the spring-jack a to the pole d of the local-exchange battery (Z.

At the central oflice the trunk-line is connected with the usual terminal spring-jaclw and is equipped in the samemanner as an ordinary subscribers line. I have. illustrated an operatorsplug-circuitat the central ofliee, adapted to make connection between the spring-jack of the trunk-line and the springjacks of other lines of the exchange. This plug-circuit is of the ordinary type and need not be particularly described. It is equipped with the usual supervisory relays ff included in the sleeve-strand thereof, and a battery f is connected in a bridge of the plug circuit between the windings ot' a repeatingcoil. The relays ff control subsidiary signals ff", and when one of the plugs of the plugcircuit is inserted in the spring-jack c of the trunk-line the supervisory relay corresponding to such plug is thus responsive to the flow of current from battery f through the trunkline. A calling-keyf is associated with one of the plugs, said calling-key being adapted when depressed to sever the cord-circuit and connect the terminal contact-pieces of the calling-plug with the poles of an alternating gen erator. hen alternating calling-current is applied to the trunk-line to signal the privateexchange ofiice, such current will traverse the terminal loop, which includes the condenser Z1 and trunk-line drop 6, whereby said drop will be caused to display its signal.

Two substation instruments G H of the private exchange are illustrated, said substation instruments being connected with corresponding spring-jacks r /1/ at the private-exchange ofiice. Thus the line-springs 5 ol springjack r are connected with the line conductors leading to substation (i, and line-springs A h" of spring-jack /1/ are similarly connected with the line conductors leading to substation ll. Line indicators or annunciators are provided for the substation telephone-lines, each line having an annunciator connected in a bridge thereof, together with a source of current at the private-exchange ol'lice, and the springjacl; of each line is adapted when plugged into to open the circuit of this bridge in a well-known manner. It is designed that station Gr shall be used not only to communicate with other stations of the private exchange, but also to be given through connection over the trunk-line with the city exchange, while substation H, on the other hand, is intended to be allowed only local service in the private exchange. The equipment of the two stations (iand H and of their line apparatus at the central office is identical, with the single exception that the spring-jack of the line ol station H is provided with a ring contact A, which is connected by a conductor 4: with the pole (Z of battery (I. The springjacl r has a similar ring contact; but no battery connection therefor is provided.

The private-exchange operator is provided with a number of pairs of plugs and their link conductors for making connections. ()ne of these pairs of plugs with a cord-circuit therefor is illustrated in the drawings. Each of the plugs 11 Z: is provided with three contact-terminalsthe usual tip, ring, and sleeve contacts adapted to register with corresponding contact portions of thespring-jacks. Thus, for example, when plug is inserted in spring-jack (6 the parts i f 1" register with and make contact with the parts a u" 1/" of said spring-jack. The tips I A" of the plugs if .1', respectively, are united by the conductor 5 of the cord-circuit, and similarly the ring contacts 1? A" are united by conductor (3, and contacts '11 K1 are united by conductor 7. The listening-key is adapted when depressed to connect the private-exchange-operatr rs telephone set in abridgebetween the cord-strands 5 6. The ringing-key m is adapted when depressed to sever the conductors 5 (S and connect the ends of said conductors which lead to the calling-plug Zr with the poles oi a calling-generator.

The local-exchange battery is connected in a bridge between the conductors 5 (3 of the conductor 5 through the'winding ',"and the plug-circuit, said bridgebeing Controlled by The windings 0 0 of aretardaa relay n. tion-coil 0 are included in the bridge, one on either side of the battery 0?. The relay n is of comparatively'high resistanceand has two armatures, one of which is connected with the other is connected with conductor 6 through the winding 0 The armatures normally rest on back contacts, which are connected with the poles d d respectively, of the battery 4?.

When said armatures are attracted, they close against a pair of front contacts united by a conductor which includes a retardation-coil 5 1). Normally, then, the battery 0? is included in a bridge of the cord-circuit between the windings 0'0 of the retardation-coil 0, and when the relay n is excited the battery is cut off. and the retardation-coil p substituted therefor in the bridge-circuit An electromagnetic supervisory indicator is included in the circuit of the cord-strand 6 and is reponsive to current flowing therein. Said indicator is adapted to display its'signal when inert.

' ductor 3. No circuit through the relay n is completed when both the plugs are inserted in local jacks, since the ring contacts of lines designed for private service only are connected withthe same pole, d of the battery, and the ring contacts of jacks g of lines permitted exchange service also have noconnection at all.

The relay 0, which is adapted when excited to sever the circuit of thetrunk-line, constitutes a blocking device to prevent the use of the trunk-line from substations similar to substation H. While circuit is always com pleted through said relay cwhenever connection is made with the trunk-line, yet when the trunk-line is connected with a substation oftype G the circuit through said relay includes the windings of the high-resistance relay n, so that suflicient current does not flow in the circuit to excite relay 0," but when one of the plugs is inserted in the trunk-line jack and the other is inserted in the jack of a station of class H a low-resistance circuit will be completed through the relay 0 from the pole d of the battery cl to the ring a of jack a, contact 6 of plug 2', conductor 7 of the plug-circuit to contact if of plug In, thenceto the ring contact if of the spring-jack it, and so by way of conductor 4: to the other pole,

d of the battery. Current flowing in this circuit will excite the relay 0 suificiently to cause the same to draw up its armatures, whereby the circuit of the trunk-line will be broken and telephonic communication prevented.

Whenever connection is made between the trunk-line and a station of class G, the relay n is excited by current flowing in the local circuit 3 7 8, whereby said relay draws up its armatures and cuts off the battery (Z from its bridge connection with the main conductors 5 6 of the plug-circuit, at thesame time substituting the retardation-coil therefor. The substation-transmitter is then supplied with current, not from the battery cl, but from the main battery at the central ofiice of the cityexchange, the same as though the substation were an ordinary substation of that exchange. The maintenance of the bridge-circuit, including retardation-coils 0 and 9, during the coiinection with the trunk-line serves to maintain acircuit for the supervisory relay fof the central-oflice-operators plug-circuit independent of the condition of the telephone-switch at the private exchange substation. The centraloffice'- operators supervisory lamp, therefore, is'not lighted to indicate a disconnection-signal until the connecting-plug at the private exchange has been removed from the trunk-jack. If it were desired that the operator at the central oflice of the main exchange I those which are permitted only private local 7 service. A blocking device 0 is provided. for preventing telephonic communication between the city exchange and substations of the private exchange which are not designed for through connection, and said blocking device is actuated whenever connection is made between the trunk-line and such a substation. It is obvious that various means may be provided for blocking communication other than by severing the trunk-line, and ldo not wish to be limited to the precise means illustrated. When connections are made between local substations of the private branch exchange, current for exciting the substationrtransmitters is derived from the local battery (Z; but when through connection is made from a sub. station to the central office A the local battery d is cutoff and currentis derived directly from signal device of the A operators plug-circuit thus receives current as long as connection is maintained with the trunk-line at the B switchboard and is independent of the private-exchange-substation apparatus.

' Having thus described my invention, 1 claim as new, and desire to secure by Letters Patent, the following:

1. In a telephone-exchange system, the combination with telephone lines of ditterent classes extending from substations to terminal spring-jacks at an exchange-switchboard, of a pair of connecting-plugs and link conductors uniting them, for connecting lines together by plugging into the spring jacks thereof, a trunk-line also having a terminal spring jack at the exchange-switchboard, adapted to be plugged into by a plug of the pair aforesaid, a blocking device for preventing telephonic communication between a substation and the station of the trunk-line, and means, controlled by connection of the trunkline with any one of the lines of a certain class, for actuating said blocking device, substantially as described.

2. Inatelephone-exchange, the combination with a number of telephone-lines of different classes extending from substations to an exchange-switchboard, of a telephone trunk-line extending from said exchange-switchboard to a distant exchange, means for connecting any two of said telephone-lines together and for connecting either of said lines with the trunkline, and blocking mechanism, made operative in connecting said trunk-line with any one of the lines of a certain class, said blocking mechanism being adapted to render inoperative the telephonic circuit thereby established.

3. The combination with local telephonelines and a trunk-line, each having switch-ten minals at an exchange, said trunk-line having a source of current in a bridge thereof at the distant station, of link conductors for uniting any two lines at the said switch-terminals, a local source of current in a bridge of said link conductors for supplying current to the telephones of local lines united thereby, an electromagnetic switch adapted when actuated to disconnect said local source of current, and a local circuit for said electromagnetic switch closed in connecting said link conductors to the trunk-line, whereby currentfor the local line is supplied from the distant trunk-line battery during the connection of said local line with the trunk-line.

4:. The combination with a number of local telephone -lines having circuit controlling switches at the substations thereof and switchterminals at an exchange office, of link conductors for uniting the lines, a local source of current in a bridge of the link-conductors for supplying current to local lines united thereby, a special line also having a switch-terminal at said exchange office, a battery and a signal device in the circuit of said special line at the distant station theretd, and a switch at the aforesaid exchange oiiice adapted to disconnect the local source of current from the link conductors and complete an independent bridgecircuit of low resistance across said link conductors, whereby when a local line is united to said special line current is derived from the battery in the special line, and the circuit through the signal device of said special line is maintained independent of the switch at the substation of the connected local line.

The combination with telephone-lines of different classes having terminal switches atan exchange ofiice, and link conductors for uniting lines at the switch-terminals thereof, a local battery and circuits connecting the same in a bridge of the link conductors, an electromagnetic switch controlling the connection of said local battery in said bridge, a portion of a local circuit controlling said electronlagnel ic switch associated with the link conductors, and conductors associated with the terminal switches of a particular class of lines adapted to complete the local circuit controlling said electromagnetic switch when connection is made with such lines, whereby the local battery is applied to the link conductors or not, according to the type of line with which connection is made.

6. The combination with a telephone trunklinc extending between two S\\il'cl]l) '):ll' ls A B, of a source of current in a bridge of the line' at the switchboard A, and a supervisory device connected in the circuit, a spring-jack terminal for the line at the other switchboard B, a pair of plugs and a plug-circuit at the B switchboard for connecting lines together, a source of current and a retanlation-eoil normally connected in a bridge of the plug-circuit, and an electromagnetic switch actuated by connection of the plug-circuit with the trunk-line, adapted to discmmect the source of current (J from the bridge of the plug-circuit and to complete said bridge independent of said source of current, substantially as described.

7. The combination with a telephone trunkline extending between two s\\'itchboards A 13, of other telephone-lines having spring-jack terminals at switchboard B, such other lines being divided into two classes, a plug-circuit connected with the trunk-line and having a plug-terminal adapted for insertion in the spring-jacks of the other lines to make conncction therewith, an electromaguelie blocking device, a circuit incl uding a source of current, for said electromagnetic blocking device, and switch-contacts associated with the spring-jacks of all the lines of a particular class for establishing the circuit of said blocking device when the plug is inserted in any spring-jack of said class, substantially as described.

8. In a telephone-excliange,the combination lished in connecting the special line with any of the lines of a particular class, whereby communication between the special line and the lines of such particular class is prevented, substantially as set forth.

9. The combination with telephone-lines having terminal switches at an exchange office,' of link conductors for uniting the lines,

a special line having a battery and a signal operated thereby in its circuit at the distant station, a source of current at the exchange office, a switch adapted to connect said source of current in a bridge of the link conductors, and a high-impedance bridge of said link conductors independent of said source of current adapted to be completed by said switch in its alternative position whereby the signal of said special line is controlled.

In witness whereof I hereunto subscribe my name this 28th day of July, AQD. 1900.

JAMES L. MCQUARRIE.

lVitnesses ELLA ED ER, ADELL HOGKETT.

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