US1202281A - Machine-switching telephone-exchange system. - Google Patents

Description

` C.AL. GOODRUM. MACHINE SWITCHINGTELEPHONE EXCHANGE SYSTEM.

APPLICATION FIEED JUNE 22H19? r UNITED sTATEs PATENT OFFICE. A'

CHARLES L. GOODRUM, OF NEW YORK, N. Y., ASSIGNOR, BY MESNE ASSIGNMENTS, TO

`WESTERN ELECTRIC COMPANY, INCORPORATED, A CORPORATION OF NEW YORK.

MACHINE-SWITCHING TELEPHONE-EXCHANGE SYSTM.

` Toell ywhom t maywncern: i Be it known that I, CHARLES L. GooDRUM,

a citizen of the United States, residing at and exact description.

This invention relates to lmachine switching telephone exchange systems of the stepby-step type, and"particularly to a system of this type wherein trunks lead from the connectors to private branch exchange l5 switchboards.

It is customary to assign to a private branchvexchange 'a single number just as if it were an ordinary substation, and to set the connector switch in the usual way under control oi' a suitable sender upon the first of vsuch trunk lines. The connector then tests such line automatically. It' the same is busy, it passes onand tests the remaining trunk lines in succession until an idle one is found,

whereupon it extends the call in the wellknown manner. In case all the trunks are busy, a busy signal is transmitted to the calling party. A,

It is the object of this invention to provide a new and improved connector circuit arrangement for effectively performingthese functions in a two-wire system, wherein the private branch exchange trunks are grouped upon special connectors, and wherein the connectors are controlled by steering or side switches.

In the circuit arrangement of this invention, 'the operation of the connector' is the same as those well known in the art/up to the y 40 point of testing the first of the private branch exchange trunks assigned to the particularfnumber involved, .that is to say, the side or steering switch in position l places .the primary stepping magnet of the connector undercontrol of the stepping `rlay lin order .to set they connector brushes in accordance with the tens digit of the wanted subscriberrs number. Upon the termination fof this' operation, the side' switch places the 'secondary stepping magnet under control of the stepping relay to .set the connector onto the first of the equivalent lines leading to the Specication of Letters Patent.

Patented oct. 24, 191e.

Application led I une 28, 1915. SerialNo. 36,719.

private branch exchange corresponding to the number in question. If the line is idle the side switch control magnet releases the side switch into the ringing position.' It is from this point on that the present circuit arrangement differs from the prior art.

In accordance with the invention, 'the side switch escapement magnet is made slow-acting, and during the transmission of the units digit is maintained energized by impulses from the armature and backcontact of the stepping relay. Thus, when the sender restores and maintains the line circuit closed, its armature begins to drop away. The relation between the side switch A'escapement mechanism and the escapement magnet-armature is such,'however, that it does not release the side switch until it reaches the yend of its stroke. Before itreaches the end of its stroke, it closes a circuit including its own winding, the secondary stepping magnet winding and the connector test brush. Now under the assumed condition that the first line is busy and hasground upon its test terminal, the side switch escape-ment magnet closes a circuit for the said stepping magnet, which steps the brushes onto the next set of terminals which represents an equivalent line to that just tested. In case this line is idle, its test terminal is ungrounded and the escapement magnet deenergizes and releasesthe side switchinto the ringing position. It, on the contrary, this line is also busy, the escapement magnet again attracts its armature before it has fallen back far enough to release the side switch, and near the end of its forward stroke again breaks its own circuit and that of the secondary stepping magnet and again ,denergizes, its armature, upon closing its back contact, giving another impulse to the secondary stepping magnet. In this manner the connector is stepped ahead until rin ungrounded test terminal is reached, when connection ismade to such line. Each group of lines leading to the same private ranch exchange or to the same station, 2is to owed by a set of contacts upon whichv thm-connector brushes come to rest, if all the Atrinke are busy, and transmits a busy signal to th.r calling party in the well-known manner.

Referring. to the drawings,- the 'connectorl circuit only is shown, 1t being understood that a connection would ordinarily lead from the calling substation A through one or more finders or equivalent switches and group selectors, and finally through the connector shown, to the private branch exchange.

Figure 1, therefore, shows only the connector circuit of this invention, and Fig. 2 is a detail view of the 'side switch escapement mechanism and the control magnet therefor.

The invention will be readily understood from a description of the operations involved in setting up a connection.A The removal-of the receiver by the callingv party at substation A initiates-the movement of the line finder. lVhen such finder has connected with the calling line, the stepping relay 10 at the first selector is energized over the following circuit: free' pole of battery, left winding of said relay, conductors 11, 12, brush 13, terminal 14, line conductor 15 through the telephonie apparatus at substation A, line conductor 1G, terminal 17, brush 18, conductors 19 and 20, right winding of relay 10 to ground. Relay 10 thereupon closes the following circuit for slowacting relay 21 as follows: free pole of the battery, relay 21. conductors 22 and 23, armature and back contact of relayv 2l, conductors 25 and 26, armature and front con.

tact of relay 10 to ground. The slow-acting relay 2l thereupon, at its left armature and back contact, opens the circuit of release conductor 30 leading back to the line finder or line' finders and prepares a circuit for slow-acting magnet 27. which is' the escapement magnet of the side switch. lhe calling party now operates his senderl and interrupts the line circuit a number of times. corresponding to the tens digit of the wanted line.

Each time the. armature of relay 10 closes its back contact, an impulse is sent tothe primary stepping magnet 32 of the, connector over the following circuit: 't'reo pole ot the battery, magnet 32. side switch arm 3?) and -its first contact. conductor 2H. 35. right armature and trout contact of relay 2l, conductor 29. armature and backcontzurt ot relay l() to lground. 'l`he magnet 32 thus steps the hruslua.l Ilo, 3T and 33 into operative relation to the group et' terminals containing the group ot' trunks leading to the desired private hranch exchange. Upon the irst closure ot' the bach' Contact of relay l0,

the slow escaluincnt magnet was yenergized over the following path: i'ree pole. of battery` lett winding ot' magnet 27, conductors 2S. 35. right armatury and t'ront contact ot relay 2l. conductor 2.) to ground. lVhen the sender 3l completelyrestores and maintains the line circuit closed. the circuit traced for the 4escapement magnet 27 is opened at the armature and back contact ot' stepping relay 10, and after an interval the magnet 27' allows its armatures to re-y magnet 39, side switch arm 33 and its second contact, conductors 34 and 35, right armature and front contact of relay 21, conductor 29, armature and back contact of relay 10, to ground. The magnet 39 therelupon steps the brushes in a secondary direction over the terminals of the selected group. The first retraction of the armature of relay 10 again closed a circuit for the side switch cscapement magnet 2l over the circuit previously traced. When the sender completely restores and maintains the line circuit closed, the maintained attraction of the armature ot' relay 10 opens the circuit ot' slow-acting escapement ma net 27. Assuming now that the first o? the private lnanclr exchange trunks, whose terminals are indicated by the numbers 40, 41,' 42 is busy. the multiple test terminals l2 thereof will be. grounded. Thus, remembering that the side switch iS now in the second position. the armature of the slow-acting escapement magnet 2T, at the beginning of its reti-active movement, closes the following circuit t'or the secondary stepping magnet 39 to step the brushes 3G, 37, 3S on to the next trunk, which is an equivalent line leading to the same private h'aneh exchange: tree pole of the battery, magnet 3l), side switclt arm 33 and its second contact, conductors 34, 2S, armature and back contact ot' cscapement magnet 2T, conductor 13, side switch arm -H and its second Contact, conductor 45, test brush 3S to grounded test terminal 42. Simultaneously with the closureI of this circuit through the secondary stepping magnet 39, a `circuit is closed in pa rallcl therewith for the side switch escapement magnet 2T. This circuit is as follows: jree pole of battery. left winding of magnet 2T, armature and back contact of magnet 2T. conductor 43, sido switch arm -l-i and its second contact. conductor 45tcSt brush 38 to said grounded test terminal. Thus, the magnet 2T again attracts its armature bet'orc. it has lnovcd a suliicient distance to releasel the side switch into the ringing position. This will he clear from aconsideration ot' Fig. 'lhis ignre shows the side switch magnet 2i' energized and the side switch iu its second position. This is the condition that, prevails just as the sender 221 restores and maintains the circuit of lstepping' relay 10 closed@r It will be noted that the pin 5 6 on the armature 52 of the escapement magnet 27, maintains open the conrmiection between springs 50 and 51', which correspond to the armature 57 and back "contact 58 of the magnet 27 in Fig. 1. This armature 52 is pivoted at 59 upon the same axis as that of the arni 60 to which the toothed' U-shaped spring 70 of the escapein engagement with the third tooth G3 ofv the lower member 64.

Referring back to Fig. 1, it will be ap\l parent therefore that as long as the test brush 38 encounters grounded test contacts 42, which represent blsy lines, impulses will be sent to the secondary stepping magnet 39. `When, however, the test brush encounters a test contact 42 from which ground is removed, which indicates that the line represented thereby is idle, there is no circuit for the side switch magnet 27, and it allows its armature to retract to its extreme position, thus releasing the side switch into the third position. Side switch arm 44 in this position grounds the multiples 42 of the seized trunk to cause this line to test busy to other connectors. In position 3, the genera-- tor is connected in circuit with the seized trunk in the well-known manner. Since this forms no part of the present invention, the bell at the private branch exchange is not shown. -It will be understood that the operator will respond to the ringing of the bell 0r the lighting of a lamp, as the case may be, and by depressing a key or inserting a plug in a jack, bring her head set in circuit to respond to the calling party and determine his wants. Upon the insertion of such head set into the circuit, the relay 24 which is marginal, at its armature 'and back contact opensthe short-circuit about the -rightihand winding of the side switch escapement magnet 27, whereupon the side switch becomes energized. This circuit is as follows: free pole of battery, relay 21, conductors 22, 74, 75, 2G, armature and front contact of stepping relay 10-to ground. The side switch is released into the fourth position by the energization of the magnet 27 at this time, since the tooth which ordinarily stops the arm 83 is removed from the upper member 55, and the arm 83 therefore is not stopped until it reaches the tooth '76, at which time the side switch arms 71 are in contact with the fourth set of terminals. Current is fed to the called party over the windings of the called supervisory relay 65 in the wellknown manner.

When the calling and called partles hang up their receivers the release magnet 49-is energized over the following circuit: free pole of the battery, release magnet 49, conductor 66, primary off-normal spring PON (now closed), right armature and back contact of relay 65, conductor 82, left armature and back contact of relay 2l, conductor 30,

conductor 67, left armature'and back con- Y tact of relay 65, conductor 6'8, right armai ture and back contact of relay 21, conductor- 29, left armature and back contact of relay 10 to ground. The release magnet 49 there-k upon restores the connector and side switch. When the connector is completel restored it opens ott-normal contact PO thus deenergizing magnet 49. The closure of the armature of relay 10 to its back contact grounds conductor 78, leading back to the group selectors and finders or -`e uivalent switches, to release the same in t e well-V known manner.

Each group of terminals, representing a group of trunks leading to the same substation or to the same private branch exchange operators. switchboard, as the case may be, is followed by a set of contacts 79, 80, 81. Contact 81 has a busytone thereon. The connector brushes will always come to rest upon this 'set of terminalsif all the trunks are busy, and give a busy signal to the calling party. I

What is claimed is:

1. In a telephone system, the combination with a plurality of' lines, an automatic switch wherein said lines terminate in groups and having a test terminal for each line and a test wiper, means for grounding test contacts of-busy lines, a side switch, a

spring adapted to advance thesame, of a slow-acting control magnet for said side switch constructed and arranged to allow said spring tol advance said side switch only after its armature has retracted a predetermined distance, a stepping magnet, -a sender for' operating the same to set said test wiper on the first one of a group of said test terminals, and circuits including grounded test terminals of busy lines, said test wiper, and said control and stepping magnets, and leading through an armature and back contact of said control magnet andelosed after said armature has retracted a predetermined distance less than that necessary to release the side switch.

2. In a telephonesystem, the combination with a plurality of groups of lines, each group running` tol the same substation, an automatic switch wherein said groups terminate and having a test terminal for each line and a test wiper, means for grounding test contacts of busy lines, a sidegwitch, a spring adapted to advance the same, of a slow-acting control magnet for said side switch constructed and arranged to allow said spring to advance said side switch only after its armature has retracted a predetermined distance,y a stepping magnet, a sender for operating the same to set said test wiper on the Afirst one of a group of said test terminals, and circuits including grounded test terminals of busy lines, said test wiper, and said control and stepping magnets, and leading through an armature and back contact of said control magnet and closed after said armature has retracted a predetermined distance less than that necessary to release the steering switch.

3. In a telephone exchange system, the combination with a plurality of groups of lines, each group running to the same substation, an automatic switch wherein said roups terminate and having a test terminal oreach line and a test Wiper, means for giving said wiper a movement in a primary direction vunder control of said sender,

'a stepping magnet for moving said wiper 1n a secondary direction under control of said sender and into engagement with the first line of the desired group, means for grounding test contacts of busy lines, a side switch, a snring adapted to advance the same of a slow-acting control magnet for said side switch constructed andarranged to allow said spring to advance said slde switch only after its armature has retracted a predetermined distance, and circuits including' grounded test terminals 'of busy lines, said test wiper,'and said control and stepping magnets, and leading through an armature and back contact of said control l magnet and closed after saidv armature has retracted a predeter1uined distance less than that necessary to rel-case the sideswitch.

4. In a telephone system, the combination with an automatic selector having fixed and movable terminals including test terminals and a motor magnet, of a side Aswitch for controlling the selector and being provided with a magnet and a contact closed as said magnet is denergized, and a circuit for the selector motor magnet including test terminals of said selector and said contact of the side switch magnet.

5. In a telephone exchange system, the combination with a plurality of lines, an automatic switch wherein said lines terminate in groups and having a test terminal for each line, and a test wiper, means for changing the electrical condition of the test termmals of busy lines, a steering switch, means tending to advance the same, acontrol magnet. for said steerin switch adapted to allow said means to a vance the same only after its armature has retracted a predetermined distance, a stepping magnet for said automatic switch, means for settin said test wiper on the first of a group o test terminals, and circuitsy including test terminals of busy lines, said wiper and said control and stepping magnets, and including an armature and back contact of said control magnetand closed when said armature has retracted a predetermined distance less than that necessary to release the steering' switch.

In witness whereof, I hereunto subscribe my name this 25th day of June, A. D. 1915.

CHARLES L. GOODRUM.

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