US1246619A - Automatic telephone system. - Google Patents

Description

J. W 'LATTIG & C. L. GOODRUIVI.

AUTOMATIC TELEPHONE SYSTEM.

APPLICATION FILED APR- 25 I916- Patented Nov. 13, 1917.

C/fdf/QS L. Goodr 1. w. LATTIG &'C L. GOODRUM.

AUTOMATIC TELEPHONE SYSTEM.-

APPLICATION FILED APR- 25, I916.

1,246,619. Patented Nov. 13, 1917.

I 2 SHEETS-SHEET 2- //7l/6/7/0/1S.' Jacofi Vl/ Za/f/y. C/iflf/QS L Good/am. y y W 1 X12 Affy UNITED STATES PATENT oFFioE. f

JACOB W. LATTIG, OF GLENSIDE, PENNSYLVANIA, AND CHARLES L. GOODRUM, OF YORK, N. Y., ASSIGNORS TO WESTERN ELECTRIC COMPANY, INCORPORATED, OF NEW YORK, N. Y., A CORPORATION OF NEW YORK.

AUTOMATIC TELEPHONE SYSTEM.

Application filed April 25, 1916. Serial No. 93,386.

To all whom it may concern.

Be it known that we, JACOB IV. LATTIG and THARLES L. GooDRUM, citizens of the United States, residing at Glens'ide, in the county of Montgomery and State of Pennsylvania, and at New York, in the county of New York and State of New York, respectively, have invented certain new and useful Improvements in Automatic Telephone Systems, of which the following is a full, clear, concise, and exact description. I

This invention relates to telephone exchange systems employing machine switching. In systems of this character, 1t frequently happens that after a connection has been partially built up, a group of trunks is encountered, all of which are busy. Heretoforc, in such event, the calling subscriber received a busy signal and had to replace his receiver, whereupon the set switches were all automatically restored, and had to be subsequently reset.

A feature of this invention is the provision of a circuit arrangement wherein when in the process of setting up a connection, one of the automatic switches finds the entire group of trunks busy, a busy signal is transmitted back to the calling party. to inform him of this fact, and when one of the trunks in the group becomes idle, the switch will be automatically set in motion to seize such idle trunk and to disconnect the busy tone from the calling line.

Another feature of the invention relates to machine switching telephone exchange systems employing private branch exchange working, and provides a circuit arrangement for a. system of this character, wherein it is possible to increase or to diminish the num. ber of private branch exchange trunks allotted to a given number or to change from an individual subscribers line to a private branch exchange without disturbing the numbers of the subscribers lines connected to the connector bank contacts.

The invention is illustrated in the accompanying drawings in which Figure 1 shows in diagrammatic form a connection from a calling subscriber to a connector switch, the circuits of the latter being shown in detail.

Fig. 2 shows the circuits and apparatus for connecting the private branch exchange trunks to the connector switchshown in Fig. 1. e In the embodiment of the invention as shown in thefigures, the invention is illustrated' with a two-wire system, but it will be evident that it may be readily applied to any oneof the-well-lmown types of automatic systems. In the system as disclosed, a call to a private branch exchange system is switched through the various switches to' a connector switch in the regular manner.- When the call has been extended to the connector switch a switching device associated with an idle private branch exchange trunk is operated and connects the calling line with the desired private branch exchange system.

The invention can be best described by tracing a call from the calling substation illustrated in Fig. l to the private branch exchange shown in Fig. 2, and a call will be thus traced in the following description. NVhen the calling subscriber removes his receiver from the hook the line finder shown at 2 will automatically connect his line with an idle first selector 3. WVhen the subscriber is so connected he will send a series of im-- pulses to the first selector diagrammaticallyshown at 8, which will connect his line to a trunk leading to a connector switch, in the contact bank of which are located the terminals associated with the desired private branch exchange. WVhen the subscriber has been connected to the connector switch, cur- Specification of Letters Patent. PatentedNoy. 13, 1917.

rent will flow through the line relay 4 which 7 will consequently be energized. The energization of this line relay closes a circuit from-ground by'way of its armature and make contact through the slow-acting relay 5 to battery. The subscriber will now send a series of impulses to connect the movable contacts of the connector switch with the group of terminals containing the line associated with the private branch exchange to which connection is desired. When this series of impulses is sent, the line relay 4: will vibrate but the slow-acting relay 5 will remain energized. This will complete a circuit from the ground on the armature'of relay 4: by way of its break contact, the right-hand armature and make contact of relay 5 and the coil of the slow-acting relay 6 to battery. The operation of the slow acting relay 6 will close a circuit for the side switch magnet 7, which may be traced from the ground on the armature of the relay 8', its break contact, the make contact and armatures of relay 6 and the coil of the side switch magnet 7 to battery. The circuit completed through theslow acting relay 6 contains av parallel branch which may be traced from the make contact of the slowacting relay 5 by way of the sideswitch arm 9 and primary magnet 10 of the connector switch to battery. The primary magnet 10 will constantly respond to the vibration of the armature of the line relay 4 and this will move the brush-contactsof the connector switch .to a level which will place'it in alinement with the group of contacts which contain terminals assigned to a trunk associated with the private branch v exchange system.

' After thefirstset of impulses to the con-- nector switch hasbeen sent by the. subscr1ber,the linev relay st w ll again be energized fora definiteperiod. This will open the circuit of the slow-acting relay 6 at the break contact of the line relay 1 and the slow-acting relay 6 will thus be deenergized and in turn will open the circuit of the side switch magnet 7 previously traced. This will move the side switch arms of the connector switch into their second position. The subscriber now sends a second series of impulses which will result in the comple tion of circuits similar to those previously traced, for the first set, with the exception that the circuit through the side switch arm 9, which is now in its second position, will be completed through the secondary magnet 12. The secondary magnet 12 will consequently move the brush terminals to the contacts, in the group selected, assigned to the desired private branch exchange system. After the second series of impulses to the connector switch has been transmitted, the

line relay LWill again be energized for a' of relay 17 to battery. This causes the energization of relay 17 which closes a circuit from the ground on its armature by way of its make contact, the normal contacts 18 of the first finder switch allotted to the private branch exchange system and the break contact, armatureand coil 19 of the motor magnet of the finder switch to battery. A parallel circuit is completed fromthe olf-normal contact 18 byway ot the sideswitc'h escape magnet 22 to battery and the slow-acting relay 23 tobattery, likewise through the right-hand winding of test relay 29 of the finder-switch to battery. Immediately after the finder switch takes its first step, the ofi nornial contact spring 18 is moved to its alternate position and the initial operating circuit of the motor magnet 19, the escape magnet 22, the relay 23 and the test relay 29 is opened; This circuit is immediately completed, however, by way of the side switch arm25, the brush 26 and the break contacts and the ground on the armatures of relays, similar to relay 17, associated with trunk lines leading toidle terminals assigned to private branch exchange trunks in the various connector, switches.

This circuit completed through the armature of relay 17 moves the'brushes of the finder switch step by step from one group of contacts to the next, until the trunk extending from the connector switch to the finder switch associated with the calling line is found. l/Vhen this trunk is located, the circuit for the motor magnet 19, the escape magnet 22 and the slow-acting relay 23 is broken at the armature of the operated relay 17, and consequently the movable terminals of the finder switch are permanently located on the selected terminal; The escape magnet 22 in deenergizing moves the side switch arms of the finder switch into its second position and thereby extends the call from the callingsubscriber through the contacts of the finder switch to the private branch exchange indicated at 27. The circuit of the test relay 29 is maintained closed from battery. through its left-hand winding, its make contactand' armature, side switch arm 32, brush 33 and its associated contact, brush 16 of the connector switch and its associated contact and side switch arm 15 to ground. In position 2 side' switch arm 80 closesthe circuit of relay 16. Relay 16 in attracting its left armature deenergizes relay 17, which, in retracting its armature, grounds the finder multiples 85, thus ren dering the selected trunk non-calling to other finders.

Remembering that the side switch of'the connector is in its third position, it will now be apparent that a signaling circuit to the private branch exchange is completed from the generator 54- and the battery commutator ring 52 through the ringing relay 8, the make contact and armature of side switch magnet 7 which is operated, side switch arm 34, brush 35, of the connector switch, and its associated contact, brush 36 of the finder switch and its associated contact, out over the private branch trunk and back by way of brush 37 of the finder switch, and its associated contact, brush 38 of the connector switch and its associated contact, side switch arm 40 and the make contact and armature of the relay 4 to ground. The response to this signal from the private branch exchange will increase the flow of current over the circuit just traced which will energize the ringing relay 8 and this will open the circuit of the side switch magnet 7 which in turn will move the side switch arms of the connector switch into their fourth position. In the fourth position of the side switch'of the connector, the talking strands of the calling subscriber are connected with the selected private branch exchange trunk. The calling subscriber is now in a position to converse with the subscriber at the private branch exchange. l/Vhen the subscribers complete their conversation and hang up theirreceivers, relays 4 and 43 will deener. gize. Relay 4, in retracting its armature, opens the circuit of slow relay 5, which, in retracting its armatures, closes the following circuit for the release magnet 42 of the corn nector free pole of battery, right winding of magnet 42, right armature and back contact of relay 43, ofi normal contact 44, left armature and back contact of relay 5, left armature and back contact of relay 43, right armature and back contact of relay 5, right armature and back contact of relay 4 to ground. Release magnet 45 of the selector 3 is also energized over the following circuit in parallel with magnet 42: free pole of battery, magnet 45, test brush 82, terminal 83, test conductor 84, left armature and back contact of relay 43, right armatures and back contacts of relays 5 and 4 to ground. Magnets 42 and 45 in operating restore the apparatus of the first selector and connector switches to normal. The line finder 2 will likewisebe restored to normal in the usual manner. 7 v

The finder switch shown in Fig. 2 will be restoredby the deenergization of the test relay 29. It will be remembered that this relay is maintained in an operated position by means of a locking circuit which was traced from battery through its left-hand winding, its make contact and armature, side switch arm 32, brush 33 and its associated contact, brush 16 of the connector switch and side switch arm 15 of the connector switch to ground. Consequently, when the connector switch is restored to normal this circuit is broken at the side switch arm 15 and the test relay 29.0f the finder. switch is deenergized. The deenergization of this re lay causes the completion of a circuit from ground through the off-normal contact 45, the right-hand armature and break contact of the test relay 29, and the release relay 46 of the finder sWitch to battery. This will restore the finder switch associated with the selected private branch exchange trunk to normal. c

All'the apparatus used in establishing the connection from the calling subscriber to the private branch exchange system has now been restored to normal and is in condition to be used for another connection.

By referring to the circuitsh'own in Fig. 2 it will'be observed that but twotrunks to the private branch exchange system 27 and their associated finder switchesjyhave been shown. It will be evident, however,"that any number of these trunks, depending upon traffic 'conditions,vcan'beallotted to a private branch exchange system, and that with each one of thesetrunks will be associated a finder switch similar to the ones shownin Fig. 2., To simplify the drawing, but two of these finders have been shown. 'Allotte'd to the contact bank of each-finderswi'tch and wired in multiple are terminals connected to the terminals in thevarious connector switches assigned to the private branch exchange system. Each of these contacts in the connector switch are individual to said switch andare not multipled to the other connector switches of the group. Associated with each of the trunks leading from the connector switch to the finder switches is a relay 17 used to initiate the starting of the first idle finder switch associated with the private exchange system 27 and a cut-ofif relay 16, utilized to open the initial energizing circuit of the relay 117, when the trunk to the finder switch'asso ciated with the calling line has been found.

But two of the trunk lines from the connector switch to the finder switch are shown in Fig. 2 and, as shown, these lines are multipled through all the finder switches asso ciated with the particular private branch exchange system. It will be evident, however,

that the number of terminals in the finder switches associated with the private branch exchange systemwill be equal in number to the connectors in the group to which the private branch'exchange has been assigned. It will also be apparent that line switches could be used instead of finder switches.

It follows from the foregoing description that any set of terminals in the connector bank may be assigned to a private branch exchange system/ Bearing in mind the previous description of the circuits shown in the two figures, it becomes apparent that when themovable contacts of any connector switch are associated with the terminals assigned to any branch exchange system, the calling subscriber may be connected by means'ofthe finder switches shown in Fig. 2 with any one of a plurality of trunks tern. Any set of terminals in the ordinary connector bank can be assigned to a private branch exchange by merely openingthe multiple connections between the contacts in the switches of the group. As this set of assigned terminals may then be connected to a plurality of trunks to a private branch exchange system, which may be varied at will depending upon traffic conditions, 1t follows that the private branch exchange trunking facilities'associated with any connector switch may be changed without afi ecting in any manner whatsoever the number ing of contact terminals in a contact bank of the connector switch. Thus any one ofa number of contiguous contact terminals in the contact bank of any connector switch may be changed from a private line to a private branch exchange line or v-iceversa, without in any way afiecting the numbering of all the remaining connected subscriber s lines. Likewise in a connector switch in which all the contacts of the terminal bank are wired to individual lines, it is possible to change any one of said lines to a private branch exchange line without affecting the numbering of all the remaining connected subscribers lines.

If all the private branch exchange lines allotted to a system are busy when a calling subscriber attempts to connect with the private branch exchange, the circuits are arranged so that the subscriber will obtain a busy signal indicating this condition and this subscriber may then at his option either hang up his receiver and release the connection, or wait at his telephone, in which case the connected line willbe switched to the private branch exchange system as soon as one of the trunks to the system becomes idle.

Referring to the circuit shown in Fig. 1, when the brush contacts 16, 35 and 38 are switched to their a-ssociated stationary contacts assigned to a private branch exchange system in which all the trunks are busy, a circuit is completed from ground by way of the side switch arm 15, brush 16 and its associated contact and the break contact and armature of relay 16 and the coil of relay 17, associated with the trunk leading from the terminals of the connector switch selected to the multiple stationary contacts of the various finder switches associated with the private branch exchange trunks, to battery. The circuit just completed will cause the energization of a relay 1'7 and this will connect the ground attached to the armature of said relay, by way of its make contact, to the extended starter wire connected through the off-normal contacts 18 and the armatures and break contacts of the slow-acting. relays 23 of the various finder switches. However, as all the finder switches are engaged, the extended starter wire circuit will-be dead ended from the armature. and make contact of the slow-acting relay 23 ofthe last finder switch. At the same, time a circuit will be completed from ground through the winding 50 ofa transformer, the ofi-normal contacts 51, 52, etc., of the various finder switches, break contact and armatureof the relay 16 associated with the trunk selected by 'the, connector switch and thence by way oi brush 85 of the connector switch, side switch 1arm'34, armatureand make contact of the side switch magnet 7 the coil of the ringing relay 8 and through the interrupting dislr5l and the commutator ring 52, to battery and ground. The completion of this circuit will, energize ringing relay 8 which will attract its armature and open the energizing circuit of the side switch ,magnet 7, which will move the connector. side switch into its. fourth position. ,In this position of the side switch,,a busy tone will be sent back to the calling subscriber over a circuit which may be traced from ground through the winding 50 of, the transformer, the off-normal contacts 51 and 52 of the private branch exchange finder switches, the break contact ancharmature of relay 16, the brush 35 of the connector switch, side switch arm 34k and thence by way of the-ringing strand of the trunks between the various switches through the calling subscribers loop and back over the tip strand of the switch trunks, through theleft-hand winding of relay 4C3 battery and ground. This signal to the calling subscriber will indicate that all the trunks to the private branch exchange are busy,-and the subscriber may at his option either hang up and release the connection or remain ,at histelephone in which case he will be switched to the private branch exchange system as soon as one of the trunks become idle. As soon as one. of the trunks of the private branch exchange is disengaged and they finder associated with this trunlcrestoredto normal, the circuit of its motor magnet 19will be closed by virtue of the attracted armature of the relayz 17 associated with the trunkselected' by the connector switch and the. finder will be immediately. operated to hunt for the terminals of the trunk selected. As soon as this trunk has been found, a signal will be displayed .at the private branch exchange due to the battery bridged across the line strands of the trunk by the-,battery feed relay 43. The calling subscriber may now be onnected 120 to the desired private branch exchange subscriber.

Obviously the invention is not limited to the specific. embodiment herein, shown and described, but is capable of many variations 125 and modifications without departing from its spirit and scope.

What is claimed is:

1. In an automatic telephone. system, the combination with a plurality of subscrib- 180 ers lines, of private branch exchange trunk lines, means including a connector switch for establishing connection between said subscribers lines and said trunk lines,means to indicate to the calling subscriber when all of said private branch exchange trunk lines are busy, and means to automatically connect the first idle trunk to the private branch exchange with the calling line.

2. In an automatic telephone system, the combination with a plurality of subscribers lines, of private branch exchange trunk lines, means including a connector switch for establishing connection between said subscribers lines and said trunk lines, stationary terminals in each connector switch assigned to said private branch exchange trunk lines, other trunk lines, a finder switch associated with each one of said private branch exchange trunk lines and with all of said other trunk lines, means to indicate to the calling subscriber when all of said pri vate branch exchange trunk lines are busy, and means to start the finder switch associated with the first idle trunk to automatically connect said trunk with said calling line.

3. In a telephone system, the combination with a plurality of subscribers lines, a private branch exchange system, of a plurality of trunks to said private branch exchange system, means including a connector switch for interconnecting said subscribers lines, terminals in said connector switch assigned to the trunks of said private branch exchange system, means when a calling subscriber selects the terminals in a connector switch assigned to a private branch exchange system to indicate to the calling subscriber that all the private branch exchan e trunks are busy, switches allotted to said private branch exchange trunks, and means actuated when one of said trunks becomes idle to connect the calling subscriber with said idle trunk line.

4. In an automatic telephone system, the combination with a'plurality of subscribers lines, of a group of trunk lines, means for establishing a connection between said subscribers lines and said trunk lines, means to indicate to the calling subscriber when all of said trunk lines are busy, and means automatically to connect the first idle trunk to the calling line.

5. In an automatic telephone system, the combination with telephone lines, of a group of trunk lines, automatic switches for connecting any of said telephone lines with any of said trunk lines, means automatically actuated by the busy condition of all the trunks of a group for transmitting a busy signal to the calling party and means automatically actuated when one of said trunks becomes idle, for causing one of said automatic switches to extend the calling line to said trunk.

6. In an automatic telephone system, the

combination with telephone lines, of a group of trunk lines, automatic switches for connecting any of said telephone lines with any of said trunk lines, means automatically actuated by the busy condition of all the trunks of a group for transmitting busy signals to calling parties and means automatically actuated as said trunks become idle for successively setting said automaticswitches in operation to extend the calling lines.

In witness whereof, I hereunto subscribe my name this 22nd day of April, A. D.,

JACOB IV. LATTIG. In witness whereof, I hereunto subscribe my name this 7th day of April, A. D., 1916.

CHARLES L. GOODRUM.

Copies 0! this patent may be obtained for flye cents each, by addressing the Commissioner of Patents, Washington, D. 0.

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