US1556751A

US1556751A - Automatic telephone system

Info

Publication number: US1556751A
Application number: US477183A
Authority: US
Inventors: William A Benson
Original assignee: Automatic Electric Co
Current assignee: Automatic Electric Co
Priority date: 1921-06-13
Filing date: 1921-06-13
Publication date: 1925-10-13
Anticipated expiration: 1942-10-13
Also published as: DE430277C; FR552788A

Description

Oct. 13,1925. 1.556.151

w. A. BENSON I AUTOILTIC TELEPHUNE S'YSTEK .Filed June 15-, 1921 v V I 17.11am fi-Bansmn v I 'Z-W Patented 0a. 13, 1925.

UNITED STATES PATENT orrlcs.

WILLIAM A. BENSON, OI CHICAGO, ILLINOIS, ASSIGNOB TO AUTOMATIC ELECTRIC COMPANY, 01 CHICAGO, ILLINOIS, A CORPORATION 01' ILLINOIS.

AUTOMATIC I TELEPHONE SYSTEE.

Application fled June 13, 1881. Serial. No. 477,188.

To all whom it may cone-em;-

Be it known that I, WILLIAM A. BENSON, a citizen of the United States of America, and a resident of Chicago, Cook County, and State of Illinois, have invented certain new and useful Improvements in Automatic Telephone Systems, of which the following is a specification.

The present invention relates in general to automatic telephone systems; and the particular object of the invention is to pro vide means, when a busy line is called, for notifying the subscriber on the called busy line that a connection is desired with his line.

' The above and other objects of the invention' will be described fully hereinafter with reference to the accompanying drawlieferring now to the drawin at A is shown a subscribers substation o the usual automatic type. The line conductors extending to the substation terminate at the exchange in an individual trunk selecting or line switch 0. This line switch is of the well known rotary type whose wipers have no normal position, always remaining, when which have been modified in accordance with the features of my invention. The connector H has access to called lines such as the one shown associated with the substation A. At the exchange the line of the substation A terminates in the individual line switch C. 7

At I is shown a constantly operating interrupter the function of which will be explained hereinafter.

While in the drawin the line switch C is shown having access irectly to connector switches, it will be readily apparent that as many selectors as are necessary could be inserted before the connector H depending upon the size of the system.

Having briefly described the ap aratus shown in the drawing ,'a detailed escrip tion of the operation will now be given.

For this purpose it will be assumed that thesubscrlber at substation A desires to call the subscriber at. substation A. In order to do this'the subscriber at substation A will remove his receiver and" operate his calling device S in accordance with the two digits of the number of the desired called subscriber. When the receiver is removed at substation A, a circuit .is completed for the line rela 16 of the line switch C over the line con uctors 11 and 12 in series. Re

lay and the said motor magnet. The operation of the line switch C now depends upon whether the trunk line with which the switch wipers 27-29, inclusive are in engagement is busy or idle. Assuming that the trunk line is busy, there will be a ground 1 potential present upon the test contact en-,

gaged by the test wiper 28 and the motor' magnet ing supplied with direct ground via the said test wiper will operate as a buzzer to advance the switch wipers step b step in search of an idle trunk line.

owever, it will be assumedthat when the receiver is removed at substation A the wipers of the line switch 0 are in engagement with the trunk line comprisin conductors 30-32, inclusive, and it will assumed further that this trunk line is idle. Under these conditions, immediately following the energization of the line relay 16, switching relay 15 ener izes. It may be stated at this point that t e switching relay 15 is of sufliciently high resistance to pre; vent the energization of the motor magnet 17 in series wlth it. Upon energizing, relay 15 disconnects the line conductors 11. and 12 of the substation A from the winding of the line relay 16 and from ground, respectively, and extends them by way of armatures 20 and 22, wipers 27 and 29, bank contacts 30 and '32, normally closed springs controlled by armatures 58 and 59, to the upper and lower windings of the line relay 51 of the connector H.

The line relay 51 is immediatel energized over the calling-line loop an u 11 operating, completes the circuit of the s ow loo acting release relay 52. Relay 52, upon 0 crating, prepares the impulsing circults oi the connector H at armature 67and at armature 66 places ground on release trunk conductor 49 thereby establishin a holding circuit for line switch C. T is circuit extends by way of the test contact 31, test wiper 28, armature 21 and its front contact, winding of the switching relay 15, and thence through the winding of the motor magnet 17 to batter This circuit serves to maintain the switc ing relay 15 operated throughout the connection. A branch of the holding circuit also extends by way of the private normal conductor 35 to multiply connected test contacts in the banks of connector switches which have access to the line of the substation A whereby the said line is protected from intrusion in the usual manner.

The subscriber at substation A may now operate his calling device in accordance with the first digit of the desired called subscribers number. By this operation a series of interruptions is produced in the circuit of the line relay 51 of the connector H and this relay retracts its armature a plurality of times in response thereto. At each retraction of its armature 60, an impulse of current is sent from ground by way of the armature 60 and itsvback contact, armature 67 and its front contact, ofi' normal springs 63 and 62, through the winding of the slow acting relay 53 and thence through the winding of the vertical magnet 88 to battery. The above is the circuit over which the first impulse to the vertical magnet is sent. However, upon the first vertical step of the switch, the off normal springs are shifted and the remaining impulses to the vertical magnet traverse a new circuit'which is the same as the one previously traced except that it includes the off normal springs 63 and 6-4 and armature 58 and its front contact, relay 53 being now in an operated position. Vertical magnet 88 operates to raise the switch wipers 90-92, inclusive, step by step until they are placed opposite the level of bank contacts in which is located the contact set associated with the line of the called substation A. The slow acting relay 53 is ener- .gized in series with the vertical magnet and maintains its armature attracted throughout the vertical movement of the switch, and at the termination thereof deenergizes and transfers the impulsing circuit to the rotary magnet 87.

The calling subscriber may now operate his calling device in accordance with the next and final'digit of the desired number. As before, a series of interruptions is produced in the circuit of the line relay 51, which deenergizes a corresponding number of times, each time'sending. an impulse of current over the following circuit: ground by way of armature 60 and its back contact, armature 67 and its front contact, ofi normal springs 63 and 64, armature 68 and its back contact, back contact and armature 75, armature 84 and its back contact, through the winding of the rotary magnet 87 to battery. The rotary magnet 87 operates to rotate the switch wipers into engagement with the set of bank contacts associated with the line of the desired substation A, which we will assume, are the bank contacts 93-95, inclusive. The slow actin relay 56 is energized in multiple with t e rotaryv magnet and operates at its armature 79 to connect the test wiper 91 with the test relay 5'5.

Assuming that the line of the substation A is idle, there will be no ground potential present upon the test contact 94 engaged by the test wiper 91 and no circuit will be completed for the test relay 55. Then, followmg the deenergization of the slow acting relay 56, a circuit is completed which may be traced from ground on release trunk conductor 49, armature 74 and its back contact, lower winding of the switching relay 57, back contact and armature 79, test wiper 91, test contact 94, through the winding of the switching relay 96 of the line switch C, and thence through the winding of the motor magnet 98 to battery. Relays 57 and 96 are energized over this circuit. However, due

to a mechanical interlocking device controlled by the armature of the line relay 97 which is now normal, the switching relay only partially operates its armatures, that is, enou h to disconnect the line of the substation from its normal batter and ground connections in the line switch 6'. Relay 57, upon energizing, establishes a locking circuit for itself at its armature 83 and at its armatures 83 and 85 completes the ringing circuit. Ringing current from the generator Gen is intermittently applied to the line of substation A until the subscriber thereat responds.

When the called subscriber removes his receiver, the ring out oif relay 54 is energized over the called line loop and, upon operating, establishes a locking circuit for itself at its armature 71, at its armatures 70 and 72 opens the ringing circuit, and at the front contacts of these armatures finally completes the talking connection. Talking battery is supplied to the called subscriber from the windings of the back bridge relay 50 which is immediately energized over the called line and operates to reverse the normal current flow over the calling line loop for supervisal or metering purposes. The. conversation may now take place between the calling subscriber at substation A and the called subscriber at substation A, the calling subrelease magnet '86 of the connector H. The

1 H to normal in the usual manner.

magnet 86 operates to restore the connector Upon ground being removed from the release trunk conductor 49 the holding circuit of the switching relay 15 in the line switch C is opened and thls rela then deene'rgizes thus restoring the line swltch to normal position. 1 a

The above is the normal operation of the system when the line of the called-substation A is idle and follows the usual ractice. However, should the line of the su station A be busy either from initiating the call or from being called, it becomes necessary in accordance with the features of the invention to notify the subscriber at substation A that he is being called. This operation will now be described. For this purpose it will be assumed that when the switch wipers 90-92, inclusive, of the connector H are rotated into engagement with the contact set associated with the line of the substation A, the called line is busy. Under these conditions, there will be a ground potential present upon the test contact 94. This ground will be laced on the test contact 94 whether the su scriber at substation A is busy from being called or initiating the call. If initiating a call, contact 94 will be grounded by way 'of'the release trunk conductor extending to the connector in use;

. while if the line of the substation A is being called, there will be a ground potential on the contact 94 from the test wi er of the connector switch which has estabhshed connection with the line. Immediately u n the switch wipers 90-92, inclusive, belng rotated into engagement with the bank contacts 93-95, inclusive, a circuit is completed which extends from the grounded test contact 94 b way of test wiper 91, armature 79 and its ont contact, arma ure' 81 and its back contact, and thence t ough the winding of the test relay 55 to battery. Relay 55, upon energizing, prepares a point in its ocking circuit at armature 74 which is closed immediately upon the "deenergization of the slow acting relay 56. Another result of the energization of relay 55 is that a busy tonefrom the busy machine is placed on the lower heavy talking conductor at armature 76 which is audible to the calling subscriber. A still further result of the 'energization of relay 55 is that a light tone is placed on the called subscribers line over a circuit extending from the tone conductor 119, ar-mavture 73 and its front contact, armature 77 and its back contact, back contact and armature 80, wi or 90, bank contact 93, and thence over the me of the called substation A. This tone serves to inform the subscriber at substation A that he is being called, but it is quite low and does not appreciably interfere with the conversation. When the subscriber at substation A hears the busy tone,

he will replace his receiver upon the switchhook and then release the operated switches in the same manner as was described hereinbefore. 'The subscriber at substation A being notified that he is being called by the above mentioned tone will, in all probability, 1

terminate the conversation as soon as possible thereby rendering his line accessible to be called and thus lessening the time during which his line is held busy.

At this point the operation of the interrupter I in producing the low induced tone which is placed on the busy called subscribers line will be describeda little more in detail. The interrupter I is made up of two

coils

100 and 101 above which is pivoted I an armature, 105. Attached to the armature'105 is a swinging pendulum 102. As the pendulum 102 moves back and forth it closes the circuit of the

coils

100 and 101 at the proper point in its are as it is connected to battery. That is, assuming that the pendulum 102 is moving to the right under influence of the coil 100 it will break contact with the contact 103 thereby opening the circuit of the coil 100 and shortly after close the contact 104 thereby closing thecircuit of the coil 101. Upon energizing the coil 101 attracts the armature 105 an causes the. pendulum '102 to move in the opposite direction. The s eed of the pendulum may be regulated by means of the weight 125 which is held in position by the set screw 126. The weight 125 is preferably quite heavy so as to make the pendulum 102 slow moving. Each time the pendulum moves back and forth, its upper end engages the spring 109 and causes it to break contact with the spring 106. However, there is a short interval when all the three contacts are making, that is, the pendulum 102, the spring 109 and the spring 106. At this instant, there is an impulse of battery sent over the conductor. 123 and through the coil 111 to round. As the pendulum 102 and the spring 109 make and break contact, the condenser 112 is charged and discharged through the upper winding of the coil 110. The current fluctuation in the coil 110 serves to induce a secondary alternating current large capacity as compared with the condenser 113. Also the upper winding of the coil 110 has a great many more turns on its winding than has the lower winding of the coil 110. This is so as to get a suflicient volume of pulsating current to su ply a number of tone leads. The tone lea 119 is common to a group of connector switches which have access to 100 lines. In the case of a large system where there are a number of groups of 100 lines each group of connectors will be supplied with a tone lead ,such as 120 and 121 and a condenser individual to each lead such as 114 and 115. It will be seen that the above construction will give a slow click tone signal to any subscriber on a called busy line, which is so light that it does not interfere in any way with the conversation.

Having full described and ascertained the features 0 the invention, what is considered to be new and desired to have protected by Letters Patent will be pointed out in the appended claims.

What I claim is:

1. In a telephone system, a calling and a called line, an automatic switch controlled over said calling line to connect with said,

called line in an attempt to establish a talking. connection therewith, a switching relay for connecting the wipers of said switch, a test relay responsive in case the called line is busy to open the circuit of said switching relay, a source of signalling current, and a circuit controlled by said relays jointly for connecting said source with the busy called line.

2. In a telephone system, a calling and a called line, an automatic switch controlled over said calling line to connect with said called line in an attempt to establish a talking connection therewith, a switching relay for connecting the wipers of said switch, a test relay responsive in case the called line is busy to open the circuit of said switchin relay, a source of signallin current, an a circuit for connecting sai source to one of the wipers of said switch to signal the called subscriber while his line is busy, said circuit including normally closed contacts on said switching relay and normally open contacts on said test relay.

3. In a telephone system, a calling and a called line, an automatic switch controlled over said calling line to connect with said called line in an attempt to establish a talk ing connection therewith, a test relay in said switch effective to prevent the completion of such talking connection if the called line-is busy, a source of busy signalling current, another source of signalling current, circuits for connecting the first of said sources to the calling line and the second of said sources to the called line, and contacts on said test relay included in both said circuits for closing the same when the test relay is energized.

In witness whereof, I hereunto subscribe my name this 9th day of June, A. D. 1921.

' WILLIAM A. BENSON.