US1581844A - Telegraph switching system - Google Patents

Description

April 20, 1926. 1,581,844

C. E. LOMAX TELEGRAPH SWITCHING SYSTEM Filed Feb. 1, 1922 T'LUEH DI Elarenma Elmmax Patented Apr. 20,

UNITED STATES PATENT OFFICE.

CLARENCE LOMAX, OF CHICAGO, ILLINOIS, ASSIGNOR, BY MESNE' ASSIGNMENTS, TO AUTOMATIC ELECTRIC INC., OF CHICAGO, ILLINOIS, A CORPORATION OF DELA- WARE.

TELEGRAPH SWITCHING SYSTEM.

Application filed February 1, 1922. Serial No. 533,362.

To all whom it may concern:

Be it known that I, CLARENCE E. LoMAx, a citizen of the United States of America, and a resident of Chicago, Cook County, and State of Illinois, hayeiiivented certain new and useful Improvements in Telegraph Switching Systems, of which the following is a specification.

The present invention relates in general to telegraph switching systems, and more specially to systems of this character comprising a plurality of telegraph stations eaph having a line extending to a central exchange. or switching-point, together with suitable automatic switching devices at the exchange for connecting any calling telegraph line with any desired called telegraph line. A system of this kind is useful in banks or other business establishments as a means of communicating between the different departments, and in case telegraph apparatus'oi the printing type is used, as is contemplated, the system is especially useful in that it prescrvcsa record of all communications.

.While ordinarily there would be no particular difiiculty in providing means for switching one line of a plurality of lines in connection with any of the other lines, in

the .case of telegraph lines, the problem is complicated by the fa'ctthat such lines are norn'ially operated on, closed circuit, and special arrangements have to be provided for establishing the interstation circuits at the same time that the local circuits of the stations involved are broken, in order to avoid opening the circult at any station during the switching process.

The particular arrangement provided for this purpose by the present invention will now be described and its operation will be explained in reference to the accompanying drawings, which shows diagrammatically the apparatus and circuits involved in set ting up a connection between the telegraph station A and the telegraph station B.

Although as previouslyindicated it is intended to use the invention in connection with printing telegraph-equipment, such aparatus 1s exceedin l com licated and since the invention has to do merely with the establishment of theinterstation circuits, it has not been considered necessaryto show complete station equipment of this'compli- 1,279,352, issued Sept. 18, 19 18, which isused for. controlling the automatic switch associated with this station at 'the exchange. The key K is provided for closing the circuit of the calling device. The lamp L is a busy lamp, and is lighted whenever it is attempted to establish connection with a busy station.

The line conductors 2, 3, 4c and 5 extend to the central-exchange or switching point and terminate in the individual connector switch H, which is preferably of the. mechanical construction shown and described in the patent to Keith, Erickson & Erickson, No. 815,176, granted March 13, 1906. As will be understood this switch may have access to one hundred lines which terminate in contact sets arranged in a plurality of horizontal rows or levels. In order to connect with a desired line, the switch is first operated to raise its wipers vertically to a position oppo-,

site the particular row or level in which the desired line appears, and is then operated to rotate its wipers into connection with the desired line. In thecase of the connector H, these operations of the connector are all controlled by the subscriber at station A by means of the calling device CD, as will appear more clearly hereinafter.

There may be one hundred stations in the system illustrated, and each station is provided with a connector switch exactly like the connector H. Each connector has access to all of the lines in the system, and thus the party at any station, by suitably operatinghis individual] connector switch, can establish a connection with any other station. i

It may be that under some circumstances a number of the stations will be located in the same department, and of such a character that it is a matter of indilference to a calling subscriber as to which of the particular stations in such department he 0btains connection with. Certain arrange- Ski ments shown herein are arranged to take careof this situation by providing for automatic trunk selection by the connector switches in the case of station lines which may be arrangedin groups under the circumstances mentioned. subscriber,.in calling a department having a number of grouped stations, will call the number of the department, and will automatically establish connection with a line leading to the first idle station in such department.

Having pointed out the general features of the invention, its operation will now be described more in detail, and for this purpose it will be assumed that the party at station A desires to establish a connection with the party at station B. Before proceeding, it will be well to point out that the telegraph apparatus at the station A is included in a closed circuit which extends from round at G by way of resistance a, restmg contact of armature 60 and the said armature, conductor 1, switch S, magnet M, conductor 2, normally closed contact springs controlled by armature 76, and resistance 1 to the grounded battery B. It will be .seen also, that the telegraph apparatus at station B is included in a closed circuit similar to the one described for station A, except that it includes the battery B In practice,

the batteries B and B will be the same ordifi'erent batteries depending on the distance between the stations and perhaps on other circumstances. The telegraph battery, or batteries, are preferably ofhigh voltage, as is inost suitable for telegraph systems. The other batterysymbols shown in the drawinglall refer to the same battery, which is the one used for supplying current to the automatic switchesat the exchange.

Now, since the two stations are normally. connected in alocal closed circuit, the establishment of a connection between the two stations will necessarily involve the opening of both local circuits and the completion of an interstation circuit in which the telegraph equipment at both stationsis connected in series. While the inter-station circuit might conceivably include both batteries, in case different batteries were employed at the two stations, according to the present arrangement only one battery is used in each connection, and the battery used is the one at the called station.

To extend a connection, the key K isfirst operated in order to, connect up the, calling device CD after which the calling device is operated. in accordance, with the two digits in the number assigned to the called station, which may be assumed to be the number 55. When the key K is operated, a circuit is completed over conductor 5- for the line relay 16 of the individual switch H, and the said relay energizes and com: pletes a circuit at armature 61 for the slowacting release relay 17. Upon energizing, the latter relay disconnects relay 15 at arni ature 62 andat the saine point connects ground to the conductor 6, whereby a test potential is placed on the test contacts 10 and 11 and multiples thereof in banks of the other connector switches. In addition to the foregoing, relay 17 prepares a circuit for the vertical magnet 2% at armature 63. The calling device is now operated in accordance with the first digit. Five interruptions are accordingly produced in the circuit of the line-relay 16, which deenergizes five'ti'mes and transmits a like number of impulses to the vertical magnet 24 over the following path: From ground by way of armature 61 and its resting contact, resting contact of armature and the said armature, armature 63 and its working contact, shaft controlled off-normal springs 27 and 29, winding of the slow-acting series relay 18', and the winding of the vertical magnet- 24 to battery. In response to impulses received over the above circuit the vertical magnet 21 operates to raise the switch shaft step by step until the wipers 35,36 and 37 stand "opposite the fifth horizontal level of bank contacts. series with the vertical magnet and being slow-acting, remains in operated position during the vertical stepping movement. At

its armature '64, relay 18 maintains the impulsing circuit closed through its own winding and the vertical magnet, notwithstanding the shifting of the shaft controlled olfnormal springs, which takes place at the first vertical step of the switch. At the end of the vertical movement, relay 18. falls back and transfers the impulsing circuit from the vertical magnet to the rotary magnet 25.

When the calling device is operated in accordance with the second digit of the number, five more interruptlons are produced in the line circuit and the line relay 16 is deenergized fiye times asbefore. This time, however, the line relay transmits impulses to the rotary magnet 25 over the" following, path: Fromground'by way of armature 61 and its resting contact, resting contact of armature'75 and the said armature, armature 6 3 and its working contact, off-normal springs 27 and 28 armature 6 1 and its resting contact, resting contact of armature 67 and the said armature, winding of the slow acting series relay 20', and the winding of the rotary magnet 25 to battery. By the operation of the rotary magnet, the wipers 35, 36 and 37 are rotated step by step and are finally broughtto rest in engagement with the particular set of bank contacts in which the line of station B is terminated, designated in the drawing by reference characters .38, 39 and 40. Relay20 is energized inseries with the rotary magnet and Relay 18 is energized in being slow-acting, remains in operated posi tion during-the rotation of the. switch. At armature 7 0, relay 20 closes a circuit for the sloweacting relay 22, which is thus also maintained energized .during the rotary movement of the switch.- At armature 77,

relay 22 disconnects the test wiper 36 from the winding of the switching relay 21 and connects it by way of armature 73 andits resting contact to the winding of'th'e test relay 19. It is noted, that since the test relay is connected up at the beginning'ot the rotary movement, means is provided on the series relay 20, consisting. of armature I contact .39, itwill find a ground potential and the test relay 19 will be energized. -The rotary movement having been completed, re-

lays 20 and 22 now fall back, and a locking circuit is completed for the energized test relay as follows: From the groundedconductor 6 by wa-y of armature 66 and its Working contact, normally closed contact springs controlled byarmature 77 of relay 22, armature 73 and its resting contact, and the winding of test relay 19 to battery. In its energized position the, test relay opens the rotary magnet circuit at armature'67, breaks the circuit to the lower winding of the switchingrelay 21 at armature 66, and at armature 68- connects conductor 3 to the exchange battery, thus lighting the lamp L at station A. Since this indicates to the calling party that the desired station is busy, he will release the connection by're storing key K It may be assumed, however, that station B is idle when called. Under these circumstances, when the test wiper 36 comes into engagement with test contact 39, it will find no ground potentials and the test relay 19 will not be energized. Accordingly, when relays 20 and 22 fall back at the end of the rotary movement, a circuit will be established for the switching relay 21 as follows: From the grounded conductor 6 by way of armature 66 and its resting contact, lowerwinding of relay 21, resting contact of armature W and the said armature, test wiper 36, test contact 39, conductor 6', armature 62 and the winding of relay 15 to battery Relays 21 and 15 are energized in series over the above circuit, and the latter relay disconnects conductor 4 from ground at armature The switching relay 21, L \on energizing, establishes a locking circuit 1. r itself at armature 72, opens the circuit f the test relay 19 at armature 7 3,-opens the operating circuit at armature 75, and at arplished b mature 7 4 connects direct ground to the test wiper 36. In addition to the foregoing, at

armature 76 relay 21 disconnects the line conductor 2 of station A from the battery B and connects it instead to wiper-37, this operation taking place simultaneously with the operation of armature 60 by relay 15 which was previously described. Both of the local telegraph circuits have now been broken and an inter-station circuit has been established which may be traced as follows: From ground at G by way of resistance 1",

resting contact of armature 60 and the said armature, conductor 4, switch S, magnet M, conductor 2, working contact of armature 76 and the said armature, wiper 37, contact 40, conductor 4, switch S magnet M, conductor 2, nonnally closed contacts controlled by armature 76 of relay 21, and'the resistance r to the grounded battery B The establishment of the above circuit completes the operations incident to securing the desired connection.

The two stations being now in communication with each other, the party at station A may open the switch S, and by suitably manipulating key K can transmit code sig nals to the party at station B, which are there rendered audible by means of the sounder magnet M; or, 1n case printing telegraph apparatus is used at the two stations, the party at station A will spell out the message he desires to transmit on the keyboard at his station, whereupon the message will be printed out on tapes at both stations simultaneously. It will be understood, of course, that when the automatic printing equipment is used, the transmission of a message does not require the presence of the receiving-operator at the other end, the message which is sent being printed on-tape as stated, where it is accessible to the operator or other party at the receiving station when he returns.

The release of. the connection is accomrestoring key K as previously mentione The restoration of this key breaks the circuit ofline relay 16, which falls back and permanently opens the circuit of slow-acting release relay 17. The

latter relay upon deenergizing, takes ground oft from conductor 6 in order to clear the line of'station A for incoming calls, and

wiper 36, thus permitting the deenergization oflelay 15 in the switch associated with ion now in normal condition, ready for other the called station B. All the apparatus is calls. v

The automatic trunk selecting feature of connector H will now bebriefly explained. The connectors are preferably provided with extra banks of test contacts, such as the test contacts 10 and 38, associated respectively with stations A and B. The extra test contacts which are associated with all single or individual stations, are left dead or disconnected, asshown in the case of the test contact 38 which is associated with the line of station E. In the case of grouped stations however, which are selected auto matically responsive to the calling of the group number, whichit may be stated, is the number of the firststation in the group, each extra test contact is connected'to its' associated regular test contact. This is true of the test contacts associated with all the stations inthe group except the ones associatechwith the last station in the group,

' which are left separate or disconnected from each other. The manner in which the testcontacts of a grouped line areconnected, is shown in the. case of contacts 10 and 11 associated with the line of station A. Y

Assuming now, that the connector H is operated to establish connection with a set of contacts in which is terminated a line extending to the first station of a group. If

this station is-busy, the test contact engaged by test wiper 36 will find a ground potential and'the'test re'lay 19 will be energized, as previously explained. At the end of the rotary movement relay 20 will fall back and open thecircuit of relay 22, but the latter relay being slow-actim will not decnergize immediately. \Vhen re ay 20 falls back a circuit is completed for the'stepping relay 23 as follows: From the-grounded test contact engaged by test wiper 35, (this test contact is permanently connected to the test contact engaged by test wiper 36), by way of test wiper 35, resting contact of armature 69 and the said armature, working contact of armature 6 5 and the said armature, interruper contact of rotary magnet 25, and the winding of stepping relay 23 tobattery. Relay 23 is energized over 'the above circuit, and locks itself at armature 7 9, at the same time closing acircuit for the rotary 'magnet'25 at ari na'ture Relay 20 being now deenergized, the slow-acting relay 22 is energized in parallel with the rotary magnet, andisthus prevented'from' deenergizing. The operation of the rotary magnet advances the switch wipers into en.-' ga'gement with the next set of bank contacts, The rotary magnet also breaks the .circuit of the stepping relay 23, which accordingly falls back and breaks the rotary magnet circuit, which then deencrgizes also and again ,closes'its interrupter contact.

If the next set or contacts is engagcu also, the foregolng operations will be repeated,

and it will be understood accordingly, that idle Ifidle, neither test wiper will find a ground and communication with the selected called station will be established by theenergi'zation of switching relay 21, as previously pointed out, but if busy, the test contact 36 will find ground potential, and the test. relay 19 will'be locked up to light the busy lamp at the calling station.

It will be seen from the foregoing, that suitable switching-apparatus is provided, whereby closed circuit telegraph stations, such as stations A andB for example, may be connected in a series circuit without-interrupting the flow of current through the instruments at the two stations during the process of establishing the connection. This is, of course, accomplished by theenergization, in the case of the stations mentioned, of the switching relay 21 o't the connector H at the same time or slightly before. the energization of relay 15 in the connector associated with the called station. In order to insure the correct timingof thcsc relays, relay 15 is provided with a slug of copper, as indicated in the drawing, which renders it slightly slow to'pull up. Resistances such.

ion

as r to 1", inclusive, are provided toprevent short-circuiting of the batteries or the telegraphfinstruments during the establishment and release of. inter-station circuits. The arrangement shown and described is-intended for use in connection with that type of equipment in whiclrit is positively required that the flow of current must be maintained through the telegraph instruments at all times, except during the actual transmission of code signals. jCertai-n types of telegraph equipment,- howe'ver, have less rigid require- -ments and permit the momentary breaking of the instrument circuits, preliminary to the transmission of redeption of a' message; or, the system may -loe'ojf the type in which a momentary/opening of the circuit is .re quired to be introduced in order toprepare the equipment tor .thetransmission or re ception of messages.- In such cases-the resistanc-es 7" to rt, inclusive, may be omitted,

and ordinary make and break spring combinations maybe used at the connectors in place ofthe make before break spring combinations which are shown at armature 76 oi; the connector H and-at armature 7 6 of the connector associated with station B.

considered to be new will be Having described the invention what is pointed out in the appended claims.

lVhat I claim is:

1. In a telegraph switching system, a plurality of closed local circuit telegraph stations, there being three or more of said stations, automaticfsw'itches for connecting any two stations in series, and relay means in said switches for establishing a series circuit between any two connectedstations before opening the local-circuits of said stations.

2. In a telegraph switching system, a plurality of closed local circuit telegraph stations, there being three or more of said stations, automatic switches for connecting any two stations in series, said switches being individual to said stations and controlled therefrom, and relay meansin said switches for completing the series circuit between any two connected stations before the local circuits are broken.

3. In a telegraph switching system, calling and called stations, closed local circuit telegraph instruments at each station, an automatic step by step switch directly controlled from the calling station to establish a circuit including the instruments at .both

stations in series, and relay means in said 'included in the closed local circuit at each station, and an automatic selectively movable switch directively controlled from the calling station to establish aseries circuit including the instruments at both stations and only one of-said batteries.

5. In a telegraph switching system, calling and called stations, closed circuit telegraph instruments at each station, a battery included in the closed local circuit at each station, an automatic selectively movable switch directly controlled from the calling station to establish a series'circuit including the instruments at both stations and the bat tery at the called station, and means for switching the battery at the calling station out of circuit.

6. In a telegraph switching system, a plurality of telegraph] stations, telegraphic sending and receiving equipment at each sta tion, automatic selectively movable switching mechanism controlled from any calling station to connect the sending equipment thereat with the receiving equipment at any called station to establish communication between said stations said switching mechanism being nonresponsive to said telegraph sending equipment, and an operator controlled variable impulse sender at each station for controlling said switching mechanism as set forth.

7. In a telegraph switching system, calling and called stations, closed circuit telegraph instruments at each station, separate 7 battery and ground connections in each local circuit, an automatic selectively movable switchcontrolled' from the calling station to establish a series circuit including the in: struments at both stations, the ground connection at one station, and the battery connection at the other station, and means for automatically opening the other ground and battery connections when the series circuit is established.

8. In a telegraph switching system, calling and called stations, closed local circuit telegraph instruments at eachstation, a battery included in the closed local circuit at each station, an automatic selectively movable switch directively controlled from the calling station to establish a connection between said stations, and relay means in said switch effective upon said connection being established for completing a series circuit including the instruments'at both stations and only one of said batteries.

9. In a telegraph switching system, a plurality of stations, telegraph instruments at each of said stations normally in a closed local circuit involving separate ground and battery connections, an automatic switch individual to each of said stations and directively controlled therefrom for extending a connection to a called station, and relay means in said switchesv for automatically completing a series circuit including the in- I struments at both stations and only one battery.

10. In a telegraph switching system, call- 'ing and called stations, closed local circuit battery and a ground connection included in the closedlocal circuit at each station, an automatic selectively movable switch directively controlled from the calling station-t0 establish a series circuit including the instruments at both stations and the battery at the called station, and means for switching the battery of the calling station and the ground at the called station out of circuit.

11. In a telegraph switching system, callingand called stations, closed localv circuit telegraph instruments at each station, a bat' tery and a groundcon nection included in the closed local circuit at each station, an automatic selectively movable switch controlled from a calling station to establish a-series circuit including the instruments at both stations and the battery at the called station, and automatic means in said switch eiiective after said series circuit has been completed, for switching the battery at the calling station and the ground at the called station 013i of circuit.

12. Ina telegraph switching system, call- 3 ing and called stations, closed local circuit telegraph instruments at each station, a bat-.

tery included in the closed local circuit at each station, an automatic selectively movable switch directively controlled from the calling station, to establish-a series circuit including the instruments at both stations and only one of said batteries, and relay means in said-switch for establishing said series circuit without, at any time, dlsturb- 10 ing the current fiow over said instruments.

In Witness whereof, I hereunto subscribe my name-this 23rd day of December, A. D., 1921.

CLARENCE E. LOMAX.

Images