US1147928A - Automatic telephone-exchange system. - Google Patents

Description

H. G. DIETL. AUTOMATIC TELEPHONE EXCHANGE SYSTEM.

APPLICATION FILED FEB.23, 1909. I I

' Patented July 27, 1915.

2 SHEETS-SHEET 1- Hubzrt Gobi/Lid? Didi iwltmgeg 1 We]? JV E H. DIETL. AUTOMATIC TELEPHONE EXCHANGE SYSTEM.

\ .APPLICATI ON FILED FEB. 23, I909.

Pdtented July 27, 1915.

2 SHEETS-SHEET 2- HUEQH; GoUgLizb Didi epic]; Aiforny E wbnssee UNITED STATES PATENT OFFICE.

HUBERT GOTTLIEB DIETL, OF VIENNA, ,AUSTRIA-HUNGARY, ASSIGNOR, BY MESNE ASSIGNMENTS, TO WESTERN ELECTRIC COMPANY, OF CHICAGO, ILLINOIS, A COR- PORATION OF ILLINOIS.

AUTOMATIC TELEPHONE-EXCHANGE SYSTEM.

Specification of Letters Patent.

Patented July 27, 1915.

Application filed February 23, 1909. Serial No. 479,449.

To all whom it may concern:

Be it known that I, I-IUnEnrGorTLme DIETL, a citizen of Austria, residing in Vienna, Austria-Hungary, have invented certain new and useful Improvements in Automatic Telephone-Exchange Systems, of

which the following is a specification.

My invention relates to telephone systems, and particularly to that type known as automatic telephone systems, or systems wherein the subscribers are enabled to establish conversational connections with one another without the necessity of manual assistance at the centraloflice. In systems of this character it is important from an economic standpoint to reduce the apparatus which is individual to the telephone lines to a minimum, and to supply the central ofiice with other connecting apparatus only in the the reduction and simplification of the central office apparatus. It is some times necessary to ask the assistance of a central ofiice operator, as, for example, when securing long distance or farmers line connections, and it is another object of my present invention to provide means for establishing connections of this character without using any of the common connecting devices-at the central oflice, thus increasing the percentage of available conversational connections through the central ofiice. I

Other objects of my invention are the simplification ofthe circuits and apparatus, es- I pecially with respect to the line switch, one feature of this switch being its continued motion in one direction.

My invention is illustrated in the accom panying drawing in which Figure 1 represents the calling subscribers station, the line switch and the first selector, and Fig. 1 represents the connector, the

4 called subscribers station and his line switch and in which all of the apparatus isshown m the condition which it assumes when a conversational circuit has been established from the calling subscribers station to the called subscribers station.

It is to be understood that all of the apparatus is here illustrated in a conventional form with an idea of representing thereby the corresponding electrical and mechanical movements without any regard to the form that the mechanical parts assume in a commercial embodiment of my invention. Itis also to be understood that many details of my invention here shown and described may be modified to operate with various commercial forms of switching apparatus without departing from the spirit or scope of my invention.

In-the general operation of the system of my invention, the calling subscriber removes his receiver from the switch hook, and thereby suitably actuates a line switch which is individual to his line and which connects the limbs-of his telephone line with an idle selector switch. in a number of impulses corresponding to the first digit in the number of the desired subscriber and suitably moves the contacts of the selector switch opposite a row of connector terminals, each terminal in this row connecting with different connector switches.

any one of which is capable of connecting with the line of the desired subscriber. The

contacts of the selector switch then assume an independent movement along this particular row of connector switch terminals until they'arrive at the terminals of a connector switch which is not in use! The subscriber then sends a number of impulses corresponding to the second digitin the number of the desired subscriber and the contactsof the connector switch are caused to take a corresponding number of steps and to stop opposite the row of contacts in which the particular contact whjch'connects with the desired line is situated. The calling subscriber then sends in a number of impulses corresponding to the last-digit in the number of.

the desired subscriber and the connector The subscriber then sends switch is thereby caused to take corresponding steps along the row of contacts until it finally stops upon the. particular contacts which connect with the desired line.' Ring- "in current is then automatically connected with the limbs of the desired line and so his connection has been established to re' maintained until the called subscriber respends, when the ringing current is removed and the subscribers are connected for conversation. When either of the subscribers desires to terminate the conversation, he replaces his receiver upon the hook and thus causes the various switches through which with a common battery which is used for sig naling as well as for furnishing transmitter current during conversation. The subscribers apparatus comprises the usual apparatus of a common battery subscribers set, and in addition thereto, the signal sending device 1. This device comprises a dial 2 having ten finger holds corresponding with the different digits from one to ten, this dial being adapted to be moved about a central pivot by placing the finger opposite the desired number and drawing it in a clockwise direction until the finger strikes against the stop 8, when it is released and caused to return to its normal position by a spring not illustrated. Secured to the shaft of the dial 2, is the star-wheel 4, this wheel having ten projections or teeth corresponding in their relative angular positions with the ten finger holds on the dial 2. The button 5 secured to the side of the plate 4 normally presses against the spring 6 to hold it in contact with spring 7 to complete the transmitter circuit when the dial is not in motion. hen the dial is moved in a clockwise direction the rollers 8 and 9 which are supported on rocker arms are moved to the the spring 7 to make one connection with the spring 10, and finally the button 5 engages the spring 6 causing it to connect with the spring 7. The spring 10 is connected with earth and therefore, in calling any digit, as, for example, 6, the contacts 6 and 'i are first separated disconnecting the limbs of the telephone line at the substation and then upon the release of the dial the impulse side of the telephone line 12 is connected with ground six times, these connections being periodic and their time being governed by some mechanical means attached to the shaft of the calling device. pulses have terminated, the button 5 passes under the roller 9 and connects the switch ing limb of the telephone line 13 with earth once/l The transmitter circuit is then estab- After these six imlished through the contacts of springs 6 and 7 This operation is repeated as many times as there are digits in the number of the desired subscribers phone.

Before sending in a call the receiver at the substation is removed from the switch hook, this operation causing the hook to wipe past the contact 15 which momentarily completes a ground connection with the impulse side of the line. hen this occurs an impulse of current flows from the battery A through conductor 16, contacts of cut-ofi" relay 112, the coil of relay 17, over line con-- ductor 12. and through the switch ,hook and contact 15 to earth, it being understood that when the switch hook arrives at its final position the connection with contact 15 is again broken. The actuation of relay 17 closes a circuit from battery A through conductor 16, contacts 18 and 19 of relay 17, contacts 20 and 21 of relay 22, the coil 23 of switching relay 24, and contacts 25 and lever 26 to ground.

The switch limbs 26, 27, 28-and 29 are mechanically connected by means of the rod 30, this rod being adapted to be moved into normal position by the actuation of magnet 31 and to be retained in that position by the catch 32 of relay 24. The actuation 'of relay 24. permits the rod 30 to move downward until it is retained by the'catch 33 and the release of the relay 24 permits the rod 30 to move to its final position, the switches 26, 27, 28 and 29 thus normally standing on their lower contacts, and upon the actuation of the relay 24 standing on their middle contacts, and after they release of relay 24 standing on'their upper contacts. The actuation of relay 24 therefore moves the switches to their second positions and closes contacts 35 and 36, and contacts 37 and- 38 of that relay.

The line switch 40, one of which is provided for each telephone line, is adapted to berotatcd in a clockwise direction by means of the magnet 41, the arms of' this switch carrying wipers adapted to connect with the contacts of the various selector switches as the line switch rotates. This line switch has no returning spring and remains in the position at which it is left by the last actuation of the motor-magnet 41. If a selector switch is busy its private contact 42 will be connected through battery to earth, as will be hereinafter described, and therefore a circuit is established from the various busy private contacts 42 and 42 through conductor 43, contacts 38 and 37 of relay 24, winding 44 of relay 24 and contacts 45 and 26 of the gang switch to ground. The'current in this path maintains the actuation of relay 24 even after the relay 17 has resumed its normal position. During the actuation of relay 24 current Flows from battery A through conductor 16, contacts 18 and 46 of relay .17 winding 47 of relay 24, contacts 35 and 36 of relay 24 and the coil of stepping In gnet 41 through the interrupter 48 to grenind. The current in this path actuates the magnet 41 causing the rotation of the contacts of the line switch 40, and also assists in maintaining the actuation of the relay 24, so that the line switch will take a complete step after its private wiper has passed off of the busy contact 42' on to the idle contact 42. lVhen the idle selector switch contact 42 is found the flow of current through conductor 43, contacts 38 and 37 of relay 24, and the winding 44 of that relay is interrupted, and the relay 24 therefore assumes its normal condition, thereupon switching the contacts of the gang switch to their final positions. 1 I

if. the time the call is initiated the arms of the switch 40 are standing upon contact of an idle selector switch, there will be no movement of the arms of the line switch.

i In this instance the removal of-the receiver r 48 through the coil of motor-mag contacts 36 and of relay 24, coil 47 relay, the nowclosed outside con relay 17 and the coil of that relay 1 the closed contacts of relay 112 pole 'of battery A. The winding 0 motornlagnet 41 being of low resistance compared with the line relay 17 the current in this path will not be suilicient to actuath the motor-magnet and step the arms of thfi. 45 line switch. W'henthe interrupter 48 arrives at its open condition the circuit through the coils of relays 24 and 17 will be interrupted and theserelays will both return to their normal conditions, allowing the gang switch switch having been moved from its normal .position. 7 -ltwill be seen that the limbs of the telephone line are now connected through the switches 27 and '29 of gang switch 30 and contacts 50 and 51 of the line switch 40 I through contacts 52 and 53 of the gang switch with the coils of relays 56 and 57. The calling subscriber now places his finger opposite the figure corresponding to the first digit in the number of the desired subscriber and pulls his dial and releases. Supposing this to be No. 6, the impulse line conductor '12 will be connected with. ground times through springs 10 and 11 and therefore .he ground pole of battery at inteif to move to its final position without the line current will flow from battery A through relay 56 to actuate six times in unison with the six impulses of current sent through it.

The actuation of relay 56 closes its contacts 60 and 61 a corresponding number of times and causes the actuation of the vertical magnet 62, the pawl of which engages the teeth upon the shaft of the selector switch, car'ry-.

ing that. shaftwith its contacts up ,to its sixth position. After the six-impulses have been received over the impulse side of the line, one impulse will be received over the switching side of the line. The current will then flow from battery A, through conductor 58, the coil of relay 57, contact 53 of gang switch 55, contacts 51 of line switch 40, contact 27 of gang switch 30, line conductor 13, and springs 7, and '10 to ground. The current in this path actuates relay 57 closing its contacts 63 and 64 and completing a circuit from battery A through conductor 58, conductors 147 and 65, the coil of rotary magnet 66, conductor 67, winding 68 of relay 69, contacts 63 and 64 of relay 57 to ground. Current in this path actuates relay 69 and also actuates the rotary magnet 66,causing the selector switch shaft and its contacts to bemoved to their first rotary position. If

the connector switch whose contacts termi nate at the first rotary position of the selector switch is busy, the private contact 77 will be connected through battery to earth as will be hereinafter described, and current will flow through privatewiper 70, contacts 71 and 72 of relay 69 and the winding 73 of relay 69 to earth. Current in this path will maintain the actuation-of relay 69, and therefore after the relay 57 has resumed its normal position current will flow through conductor 65, the coil of rotary magnet 66, conductor 67, winding 68 of relay 69, contacts 63 and 74 of relay 57, contacts 75 and 76 of relay 69 to earth through the interrupter 48. The interrupted current in this path will cause the interrupted operationof rotary magnet 66, the pawl of whichwill cause the rotation of the selector shaft until its private contact arrives upon a contact which is not connected with battery, at which time the relay 69 will fall back to its normal position, and cut off the interrupted current through the rotarymagnet 66. At the same.

further extended through contacts 78 and 79 of the gang switch 55 through contacts 80 and 81 of the selector switch through con-- tacts 82 and 83 of gang switch 84 of the In this I 87, contacts ber of the desired subscriber and again causes connector switch with the coils of relays 85 and 86. The operator now moves her dial to correspond with the second digit infthe number of the desired subscriber and in the same manner as formerly described, causes-a determined number of impulses to flow from battery A throughconductor 87 and the coil' of relay 85, over the impulse side of the.

number of the desired subscribers phone.

The impulse which is received as before described, over the switching side of the line, causes one actuationof relay 86, which, due to the escapement onits armature 92, permits the gang switch to move to its second position. The subscriber now moves his dial to correspond with the last digit of the numthe relay 85 to actuate a corresponding number of times. Impulses from battery A are therefore sent through conductor 87, contacts 88 and 89 of relay 85, contact 93 of gang switch 84 and the coil of rotary magnet 94 to ground, which magnet by its pawl causes the rotation of the connector shaft to the position in which its wipers are connected with the contacts of the desired line. The

impulse which is then received upon the switching side of the line actuates the relay 86 once and causes the gang switch 84 to step to its final position.

It will'now be seen that current from battery A flows through the coil 95 ofrelay 96,

contacts 97 of the gang switch 84, contacts of the selector switch, contacts 7 8 of gang switch 55, contacts 50 of the line switch 40, contacts 29 of the gang switch 30, line conductor 12, contacts of the switch hook, receiver, transmitter, springs 6 and 7, line conductor 13, contacts 27 of gang switch 30, contacts 51 of line switch 40, contacts 7 9 of gang switch 55, contacts 81 of the selector switch, contacts 98 of gang switch 84, and the coil 99 of relay 96 to the other pole of battery A. The current in this path actnat-es the relay 96 closing its contacts 100 and 101 which complete a circuit for ringing current from the alternating current ringing generator 105 through contacts 106 and 107 of relay 108, contacts 101 and 100 of relay 96, the lower wiper spring and the connector contact 108, conductor 13, the annunciator and condenser at substation 1', conductor 12, contacts 109 of the connector switch, conductor 110 and the coil 111 of relay 108. through the main battery A to ground. When the wipers of the connector switch arrived upon the contacts of the desired line and the gang switch 84 moved to its final position, a circuit was completedfroni the live pole of battery A through the coil of the cut 01f relay 112 which is individual to the called line, through the eontacts-103 of the connector switch, conductor 114, contacts 115 and 116 of relay 86 and contacts 117 of the gang switch 84 to ground. The. current in this path .actuates the cutofi relay 112 and thereby disconnects the coil of relay 17 from its connection with the main battery A, so that the ringing current now connected with the desired line for sounding its annunciator is not shunted through the coil of relay 17 The ringing current passing through the.

high resistance annunciator and the condenser at the substation is not suflicient to actuate relay 108 but sounds the annunciator at the, desired station.

During the application of the ringing current to the called line and before the called subscriber has answered his'call, asmall amount of the alternating ringing current returning from the substation upon conductor 12 will, instead of passing through coil 111 of relay 108, pass through the condenser in the top talking strand, then through the now closed contacts 97 of'the connector gang switch back and through the calling subscribers station, returning to ground through the coil 99 of relay 96 in the connector switch. The sound of this ringing current givesv to the calling subscriber what may be termed negative busy test since, as will be later explained if the called subscribers line is busy, the ringing current will not be applied thereto and therefore no buzz, due to the application of the ringing current, will be heard. lVhen the receiver at the substation is removed from the switchhook a path for direct current is establis ied from the live pole of battery A throu h the winding 111 of relay 10S, conductor-5110, contacts 1.09 of the connector switch, line conductor 12 and the ground contact 15 at the substation. The current in this path is sutlicient'to actuate relay 108 which disconnects the ringing current at its contacts 106 andlO'T and by means of contact 120 completes the talking circuit so that the calling and called subscribers are now connected for conversation.

The contacts of relays 96 and 108 are provided with a retaining catch which engages certa in of the contacts when the relays are actuated and retains them in their engaged position until the shaft of the connector switch returns to its normal position, at which time the retaining catch istripped, allowing the retained contacts of relays he interrupts the current flow through the 96 and 108 to return to their normal posilive pole of battery A through conductor 1122, the coil of release relay 123, conductor tions.

During conversation the current for the transmitters at the calling and called subscribers stations is furnished through the coils of relays 96 and 108, both of these relays being actuated thereby during the en tire conversation. When either subscriber desires toterminate. the conversation and replaceshis receiver upon the switch-hook,

coil of the controlling relay associated "with his end of the line. Supposing this to be the called subscriber, the relay 108 will return to normal position carrying with it" its spring 121, the other two springs being retained in actuated position by the retaining catch. lVhen the spring 121 returns to-normal position, a circuit'is completed from the 124 and contacts 125 and 121, and contacts 126 and 127 of relay 108 to ground. The

current in this path actuates the release magnet which through the'movement of its retaining catch, allows the shaft and the wiper springs carried thereon to return to normal position. The actuation of release .magnet 123 also closes the contacts 130,131

and 132 controlledthereby, and in addition thereto, resets the gang switch 84 to its normal position. When the contactsof the release magnet are closed the ground side of battery is connected through contacts 130 and 131, conductor 133, contacts 77 and 70 of the selector switch through contacts 134 of the gang switch 55, the coil of release magnet 135, and conductors 147 and 58 to the live pole of battery-A. The current flowing in this path actuates the release magnet 135 which also restores the gang switch 55.to its normal position and closes contacts 136, 137 and 138 The closing of contacts 136 and 138 completes a locking circuit for the release magnet. 135 through the off- normal contacts 139 and 140 which contacts remain closed until the selector shaft returns to its normal position, the object of this being to insure the complete restoration of the selector switch before the release magnet 135 is again denergized. The closing of contacts 136 and 137 of the release magnet connectsthe ground pole of battery through contacts 136 and 137, conductor 141, contacts42 of the line switch 40, conductor 43, contacts 28 of the gang switch 30, thecoil of the reset magnet 31 and conductor 16 to the live pole of battery A. The current in this path actuates the reset magnet 31 which returns the. gang switch 30 to its normal position, the circuit, of the magnet 31 being maintained closed through its own contacts and through the contact 142 of the gang switch 30 until the switch ceiver upon the hook t'o'terminate the con versation, the relay 96 would have been released and would have established the cir- I cuit of the release magnet 123 in a manner similar to the manner in which the circuit was established by the release of relay 108. It now remains to be described the-manner in which; a release will be accomplished if the line which is being called is already busy when the wipers of the connector switch arrive upon the contacts of the line. If the called line were busy its'private contact 103 would be connected directly with ground. If the line were a calling line this would be accomplished through contacts 26 of the gang switch 30, which contacts would also establish the circuit of cut- -otf relay 112, and if the line were a called line this would be accomplished through contacts 117 of gang switch 84 of the connector switch which was associated with the desired line, and through contacts 116 and 115 of the relay 86 of that connector switch.

In that case, after the wipers of the connector switch had arrived upon the contacts of the desired line and the final impulse was received upon the switching side of the line, the relay 86 thereby being closed for the last time, would connect the ground pole of battery through wiper contacts 103, conductor 114, contacts 115 and 1430f relay 86 and conductor 144 through the coil of the release magnet 123 to the live pole of battery A. The current in this path would momentarily actuate the release magnet 123 which would be looked up through its own contacts 130 and 132 and through the oil'- normal contacts 145 and 146 of the connector switch, thereby causing the release in the same manner as before described. The calling subscriber would then place his receiver to his ear, and .not hearing the buzz caused by the comiection of the ringing current with the called subscribers line would know that the line was busy and would therefore replace his receiver upon the switch hook, the ground contact 15 at the calling station being arranged so as not to wipe the hook switch when. the receiver is returned so that a new call will not be initiated thereby. I I

t It will be noted that inasmuch as the contacts of the line switch 40 remain [upon contacts of a selector switch and inasmuch as the contacts of this line switch 40 are also multiplied to a large number of other line switches, it is important to maintain the conductors extending to the connector rings of the line switches from the various line circuits normally open so that no current will be wasted and so that the various wipers, in passing over the contacts of busy tacts 38 and 37 of the relay 24.

It often happens that a subscriber of an automatic system wishes to e connected with a toll line or wishes for some other reason to communicate with the attendant at the automatic exchange. In order to facilitate such a connection, I provide each line with a jack and signal at the central office and also provide each subscribers station with a button which may be pressed to signal the attendant without setting the automatic apparatus into operation. To accomplish this I provide the push button 150 at the substation which when depressed connects both limbs 12 and 18 of the telephone line to earth. Current therefore flows from the live pole of battery A through the coil of relay 17 over line conductor 12 to ground at the substation. The actuation of relay 17 connects the live pole of battery through its contacts 18 and 151 and through the coil'of relay 22 and line conductor 13 with ground. The relay 22 is therefore also actuated, opening its contacts 20 and 21 which prevents the actuation of the automatic apparatus in the manner which would accomplish an automatic connection. The actuation of relay 22 also closes its contacts 152 and 153 and thereby establishes a circuit "from the live pole of battery A through the contacts of cut-ofl relay 112, contacts 152 and 153, and the locking coil 154 of relay 22, conductor 155 and the lamp signal 156 to earth. The att ndant seeing this signal displayed, inserts the plug of a cord circuit, conveniently illustrated by the 'tip and ring and grounded sleeve of an operators plug shown on- Sheet 1, into the jack which is associated with the line, the plug of this cord circuit being provided with a sleeve contact which is connected directly with earth. A path for current is therefore established from the live pole of battery A through the coil of relay 112, conductor 157 and the sleeve contact 158 of the jack and the sleeve contact of the lug to ground. The actuation of cut-off relay 3112 releases the locking circuit of relay 22 and opens the circuit of relay 17, so that battery connection is entirely removed from the limbs of this telephone line. The connection of ground with the sleeve of the jack also places the private contact 103 of this line in a busy condition so that no other automatic subscriber can connect with the line during the time that the cord circuit is in its normal condition ready for another call.

'It is to be understood that many; parts of the automatic system which are not essential to the establishing of a single connection but which are essential to the operation of the systen'ras a whole are omitted from the drawings and from the description, these omissions being well understood by those skilled in the art of automatic telephony.

.The manner in which the contacts of theunderstood that though the system here shown is adapted to only select subscribers stations having three digits to their numbers, or in other words, is only illustrated in connection with a nine hundred and ninetynine subscriber system, it is to be understood that by inserting a second selector switch exactly like the selector switch illustrated in the drawing, that subscribers stations having four digits in their numbers could be selected and the system would thereby be adapted. to select anyone of a nine thousand nine hundred and ninety-nine subscriber exchange. Further increases in the number of subscribers could be accomplished by further increasing the number of selector switches. While specific circuits are here illustrated, it is to be understood that I do not wish to be unduly limited to the details of these circuits, many changes being possi-' ble without departing from the spirit or scope of my invention,

1' claim- 1. In an automatic telephone system, the combination with a pair of telephone lines connected for conversation, of a pair of relays having coils throu h which the transmitter current is furnis ed to each of said lines, said, relays being actuated during conversation by current flowing over the telephone line and through the transmitters, an automatic switch through which said conversational circuit is established, a release magnet for said switch, and means whereby the interruption of the current through either of said relays will complete the circuit through said release magnet to thereby efi'ect the release of said automatic switch, substantially as described.

2. In an automatic telephone system, the combination with a called telephone line, of a relay and a source of current bridged between the limbs/of the line at the central office during conversation, said relay being actuated over the telephone line, automatic apparatus at-the central oflice for establish- .ing the conversational conneetinmwith said 3. In an automatic telephone system, the

combination with a pair of telephone lines connected for conversation, of a pair of condensers, one interposed in each voice current conductor connecting said telephone lines, a pair of relays and a source of current bridged between said voice current conductors, one on each side of said condensers for furnishing transmitter current to the telephone line, automatic apparatus for said connection, a release magnet for said apparatus, being adapted to actuate said release magnet to efiect the releaseof the automatic apparatus at the central oflice, substantially as described. v

4. In an automatic telephone system, the combination with a relay, of two sets of contacts for said relay, a contact of one set being electrically connected with a contact of the other set, one set being normally closed and the other set being normally open, the energization of said relay being adapted to reverse the conditions of said contacts, means for holding the normally open pair of contacts in their closed condition after I the relay is actuated and returned to normal,

whereby the clrcuit is completed seriallythrough both sets of contacts of said relay, and apparatus controlled by the circuit through said sets of contacts for tripping the retained contact and allowing it to return to normal position, substantially as described.

5. In an automatic telephone system, the combination with a step-by-step mechanism at the central oflice, said mechanism having a normal position and a plurality of dif ferently actuated positions, a releasejmagnet for said step-by-step mechanism, said magnet being adapted to be actuated by an impulse of current and to closea locking circuit for'itself which is again automati cally interrupted when the step-by-step mechanism returns-to its normal position, and a single relay adapted to control the actuation of said magnet.

6. In an automatic telephone system, the combination with a selector switch, of a relay adapted to be maintained actuated by current through the wipers of said switch and through the contacts of busy trunk circuits, over which said wiper passes, the actuation close the circuit of an interrupted source through the motor magnet to cause the movement of said wiper over said trunk contacts, the current through the motor magnet also passing through a coil of said relay, whereby the relay will be maintained actuthe release of either of said relays of said relay being adapted toated by the motor magnet current to permit the step-by-step mechanism to take a full step even after the circuit of said relay has been interrupted at the contacts of said wiper with the contacts of busy trunk lines,

1 substantially as described.

7. In an automatic telephone system, the

combination with a calling and a called telephone line, of automatic mechanism at the central station for connecting said lines, a ringing generator at the central station connected with the called lme for sending current thereover to sound the annunciator at the call station, a resistance coil at the central oflice connected 1n series with the called line and the ringing generator, the

calling line being connected in a bridge of said reslstance whereby a small portion of the generator current after having passedover the called line will pass over the calling line to indicate that a connection has been established with the called line.

8'. In an automatic telephone system, the combination with a pair of telephone lines, of a source of ringing current means for connecting said source with a limb of the called, line only for signaling purposes, an impedance at the central office through which theother limb of thecalled line is connected. to the source of ringing current,

said latter limb being also connected with a limb of the calling telephone line whereby a portion of the ringing current returning from the called line will pass through the calling subscribers receiver to indicate that a connection-has been established, substantially as described.

9. In an automatic telephone system, combination with a calling and a desired telephone line, of means for testing the busy or idle condition of the desired line, a source of ringing current at the central oliice, means for automatically connecting said source in a bridge of the desired telephone line when said line is found idle and a connection' has been established therewith, a re sistance at the central oflice in series with the the 4 desired telephone line and said ringing".

source, the calling telephone line being connected in parallel with said resistance whereby a small part of the current from the ring: ing source which passes over the called line.

will also pass over the calling telephone line to indicate to the calling subscriber that a connection has been established, substantially as described. I

10. In a telephone system, the combination with switching mechanism in an abnormal position, of a release magnet having an armature, adapted to be actuated by an impulse of current through the release magnet, a pair of contacts closed by the actuation of said armature, to thereby close a locking circuit for the release magnet, and a pair of contacts in the locking circuit of said magnet adapted to be separated when the switching mechanism returns to normal position, and a single relay adapted to control the actuation of said magnet.

11. In a telephone system, the combination with an automatic switch of a release magnet for said switch, a pair of armatures for said release magnet, a pair of normally open contracts controlled by one of said armatures and a release catch controlled by the other of said armatures, the first of said armatures being adapted to be actuated by an impulse of current through said release magnet and the second of said-armatures being adapted to be actuated by current flowing through the contacts closed by the first armature, substantially as described.

12. In a telephone system, the combination with an automatic switch of a release magnet therefor, a pair of normally open contacts and a release pawl controlled by said magnet, said pair of normally open contacts being arranged-to close upon the first energizationof'said release magnet and to thereby close a circuit for said release magnet to maintain the actuation of the release pawl, substantially as described.

13. In a telephone system, the combination with an automatic switch of a release magnet therefor, adapted to have its circuit initially closed by an impulse of current, a pair of normally open contacts controlled by said release magnet and adapted to be closed by the passage of said impulse of current through the coil of said release magnet and a circuit completed through said contacts and the coil of said release magnet to maintain the actuation of the release magnet after the impulse of current "has ceased, and a single relay adapted to control the'actuation of said magnet.

' 14. In a telephone system, "the combination with a switch for extending the limbs of the telephone line, a release magnet for said switch, a pair of normally open contacts controlled by said magnet for holding an energizing circuit for said magnet, and

Copies of this patent may be obtained for means actuated by the release of said switch for interrupting the energizing circuit of said magnet, substantially as described.

15. In an automatic telephone system, the combination with a telephone line, of a ringing generator having one pole connected with one limb of said line at the central 'oflice, a coil connected between the other limb of said telephone line and the other pole of 'said' generator at the central oflice and a calling telephone line having one limb connected to the terminal of said coil leading to said generator and 'the other limb connected tothe other terminal of said coil, substantially as described.

16. In an automatic telephone system, the combination with a pair of telephone lines connected together through automatic switching mechanism, one limb of said lines being completed fromthe calling station to the called station and the other limb of said linesbeing interrupted at the central oilice, a ringing generator at the central office, a resistance coil connected between the uninterrupted limbs of said telephone lines and one terminal of said ringing generator, the other terminal of said generator being connected with the interrupted limb of the telephone line extending to the called subscribers station, the interrupted limb of said telephone line extending from the calling subscribers station being connected with the first named pole of said ringing generator whereby a small portion of the ringing current from said generator which passes over the called subscribers line will pass over vthe calling subscriber b line *to produce a signal in the receiverat the calling subscribers station, substantially asidescribed.

Signed by me at Vienna in the Empire of Austria-Hungary in the presence of two witnesses. HUBERT GOTTLIEB DIETL.

Vitnesses ROBERT W. HEINGARTNER, AUcUs'r Fucenn.

five-cents each, by addressing the Commissioner of Patents, Washington, D. G. k

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