US1197048A - Machine telephone switching system. - Google Patents

Description

W. H. MATTHIES.

MACHINE TELEPHONE SWITCHING SYSTEM. APPLICATION nLco JULY 20. 1914.

1,1 97,048. Patented Sept. 5,1916

2 SHEETSSHEET 2.

W/fn ass 86 r UNITED STATES PATENT OFFICE.

WILLIAM HUGO MATTHIES, OF ANTWERP, BELGIUM, ASSIGNOR, BY MESNE ASSIGN- MENTS, T0 WESTERN ELECTRIC COMPANY, INCORPORATED, .A CORPORATION OF NEW YORK.

MACL H INE TELEPHONE SWITCHING SYSTEM.

Specification of Letters Patent.

Patented Sept. 5, 1916.

Application filed July 20, 1914. Serial No. 851,860,

To all ii /tom it may concern Be it known that I, lVILLiAM HUoo MAT- 'rmns, a resident of Antwerp, Kingdom of Belgium, have invented certain new and useful Improvements in Machine Telephone Switching Systems, of which the following is a full, clear, concise, and exact description. 1

This invention relates to improvements in machine telephone switching systems, and particularly to systems in which automatic switching apparatus is adapted to extend or control the extension of a desired connection by means of impulses sent from a distant station.

More specifically, the invention relates to impulse or controlling circuits and provides a new and improved system and apparatus whereby impulses delivered from a distant station will be received and caused to pro- .duce the necessary results to extend the connection to the desired line.

A particular feature of the invention has to do with the relay system provided at the incoming end of an impulse circuit of this character, such relay system being simple and eflicient and involving but a single slow acting relay. Most specifically this relay system involves a single relay located in the impulse circuit controlling two other relays associated therewith, one of the said relays being a slow acting relay; such relay system controlling the stepping of the necessary switches in response to numerical impulses in such impulse circuit; controlling the changeover from one of such switches to be set to another in response to a definite impulse in said circuit and also controlling, the disconnection and restoration of the circuits and the apparatus, if the line circuit is open at the sending station for a relatively long period, as in the case of a calling subscriber in a full automatic exchange system replacing his receiver upon the hook.

Figures 1 and S2 of the drawings taken to -{Ietl1l"Sl10W one embodiment of the invenis extended to the desired line, the set posi tion of the selector switches being determined by the set position. of the register controllers referred to. It will be understood, of course, that the specific features herein shown, and particularly the features relating to the impulse circuit and its associated relay system, are not confined to systems of this type, but may used in systems widely varying in character, either of the fullautomatic type wherein the subscriber operates the sending mechanism, or of the semiautomatic type wherein an operator at an exchange controls such sending mechanism.

Systems somewhat of the type herein illustrated are described in the-British patent specification No. 26,079 of 1910 and No. 9125i of 1911.

The invention will be best understood, and the features thereof best a pear front the description of one form thereof as illustrated in the accmnpanying drawings. The system illustrated in the drawings is for convenience. shown as a one-hundred line system in which an established connection includes a line tinder switch which searches for and seizes the calling line to' connect it to a connecting circuit. The tinder switch has assoc'-' te l therewith a connecting circuit, inc lag the usual source of current, situated in association with the usual repeating coil, as well as a registering and controlling equipment, and a selector switch adapted to select, test and connect with the desired line of the 100 lines to which it has access. It should be understood, of course, that the invention is not limited. to systems of this size, nor to any of the specific fea tures disclosed herein. For example-the system may be extended to any size by the insertion of group selectors in the circuit in the well known manner, and the addition of further register controllers in the registerin and controlling equipment corresponding to such group selectors. Also it is not necessary that the registering and controlling equipment should be permanently associated with the connecting circuit as shown, but may be common to a number of connecting circuits and connected to a particular one thereof when necessary in any well known manner.

Of the apparatus diagrammatically shown in the drawings, the line finders, selector switches,and sequence switches are of types well known in the art, such switches being illustrated as power driven switches, the specific features of which will sufiiciently appear from the description of the operation thereof.

The registencontrollers diagrammatically illustrated may be of any desired mechanical structure which performs the functions hereinafter to be described. For exiimple, they may be of the type shown in Fig.- 1 of the British patent specification No. 26,079 of 1910.

The system shown will best be understood from the description of the operation thereof.

Assume that the subscriber at station 41 illustrated to the left of the drawing dc.- sires connection with the subscriber at station 42 illustrated to the right thereof, the line of which latter subscriber may be desi natcd for example as line 42. The subscriber 41 will, to initiate the call, remove his receiver from its switch hook, thereby closing his line circuit and energizing the line relay 43 individual to his line in the usual manner. A circuit is thereupon closed through the relay 44, and the resistances 45 and 46, energizing such relay and placing a selectable potential upon the test terminal 47 of the calling line wherey'er the same ap pears in the line finder switches basin access thereto. The number of such line iiiider switches, and associated connecting circuits is determined by the trallic in the exchange and may represent the number of simultaneous calls which must be provided for in the system. The energization of the relay 44 closes the circuit to the power magnet 52 of all of such line finders as may be idle at this time, such circuit including the springs 26 top and 25 bottom of the sequence switch 20 individual to each line finder and its connecting circuit. All such idle line finders will therefore move to search for the calling line until the brush 48 of one of them comes in contact with terminal 47 upon which such selectable potential exists and a circuit is established including the high resistance winding of relay 50, the springs 29 top and 27 and the interrupter brush. 49 of this line finder. This will cause the energization of the relay 50 which attracts its armature and closes a circuit through its low resistance winding over the spring 28 bottom in shunt of the high resistance winding of such relay. This so reduces the potential upon the test terminal.

47 of the calling line in all of the other line finders, that no other line finder bringing its brush 48 in contact therewith will have its relay 50 energized and therefore prevents the seizure of this line by any other such line finder. As the line finder which has first brought its brush 48 in contact with the te minal 47 moves so that its brushes are centered upon terminals of the calling line, the interrupter circuit opens at the interrupter brush 49, and the relay 51 is energized in series with the relay 50 over spring 31." The energization of relay 51 opens the. circuit of power magnet 52 of the line finder at the same time closing over spring 23 bottom the circuit of the holding magnet 53 of such line finder thereby bring ing the line finder positively to rest with its brushes centered upon the terminals of the calling line. At the same time the energization of relay 51 closes a circuit to drive the sequence switch 20 out of its first position and such sequence switch under control of the spring .21 will move into its fourth position. On coming'into its second position the sequence switch closes the spring 30 top, which causes the energization of the cut-off relay 54 of the calling line. This relay opens the circuit of the line relay 43 and maintains the calling line busy, in all the line finders and selector switches in which it appears, in the usual manner, in-

dependent of the relays 50 and '51, the circuit of which is opened at the spring '29 top as the sequence switch 20 leaves its second position. As the sequence switch 20 comes into its second position the impulse circuit extending from the calling sub-station to the register-controller equipment is completed at the springs 33 bottom and 34 top and such circuit is supplied with current from the battery shown between the repeating coil terminals. This circuit will be maintained in the third and fourth position, and also in the fifth, sixth, and seventh positions of the sequence switch 20. The closure of this circuit energizes the stepping relay 91, which by the closure of the circuit including the spring 82 and the register sequence switch S0 drives this sequence switch into its second position. It should here be noted that the respective sequence switch springs are not shown associated with the power magnet thereof, but are so shown as to present as clearly as possible circuits which they control. It should be understood, however, that all the. sequence switch springs indicated in Fig. 1 are associated with and form a part of the connecting circuit sequence switch 20, whereas those shown in Fig. 2 are associated with and torm a part of the register sequence switch 80. It will, of course, be further understood that each of the sequence switch springs is closed and only closed in the positions indicated adjacent thereto. The register sequence switch being in position 2, andthe connecting circuit sequence switch 20 being in position 3 or 4, the impulse circuit and the register-controlling equipment are now ready for the sending of the controlling impulses by the subscriber.

The subscribers impulse sending device is herein illustrated diagrammatically at 55. It will, of course, be understood that this impulse sending device may be of any type Well known to the art, it being sufficient for this description to state that such impulse device is operated to produce a number of short breaks in the circuit corresponding to the several digits of a numerical designation of the line the subscriber desires. Having assumed, therefore, that the number of the line desired by the subscriber is 42, the calling subscriber will first produce at his impulse sending device 55, a series of five interruptions of the impulse sending circuits, such interruptions being separated each from the other by a relatively short closure of the circuit in the usual manner. The sending of the digit 4 requires 5 impulses for the reason that the digit zero requires one; the digit 1 requires 2, and digit 2 requires 3, and so forth. At each interruption of the circuit the relay 91 is denergized, but the first time such relay is deenergized it closes the circuit which includes spring 89 for energizing relay 92 which remains ener ized and locked up over its left-hand winc ing. The energization of the relay 9'2 prepares at its right armature a circuit for the stepping magnet 76 of the tens register controller 77 which is energized upon a subsequent energization oi. the relay 91. At the end of this first short interruption of the sending circuit, relay 91 will be again energizcd, and the relay 92 remaining, locked up, a circuit will be established over the springs 83 bottom and 84 bottom, and right armature of the relay 92 to energize the stepping magnet 76 of the tens register con troller which will thereby cause the movement of the register disk one step from normail in a. clockwise direction. The relay 93 will not be energized at this time, the circuit interruption and the closure between two impulses being too short to allow the relay 91 to remain energized or detinergized long enough to cause the relay 93 to respond. such relay being of the slow acting type. Upon the decnergization of the relay 91 at the second impulse the magnet 7 6 is dei nergized to prepare for a second step. Upon the subsequent closure of the sending circuit and the energization of the relay 91, the tens register controller disk will be given a sec ond step. This will continue until at the end of the fifth break the disk of the tens register controller 77 has been given 5 steps in a clockwise direction. At this time the circuit will be maintained closed for a relatively longer interval. that is, at least for the time required for the subscriber to initiate a second operation of his impulse ender to send the units impulses. This period will be suliicienliv long for the circuit including the magnet 79 of the tens gaigisler controller, to energize the slow ing relay 93 over its left-hand winding. Upon energizing this relay closes the circuit to drive the sequence switch 80 out of position 2, and such sequence'switch under control of spring 81 will move into position 4.

In moving through position 3, however, this sequence switch has opened the spring 89 thereby causing the deenergization of the relay 92. The circuit of the relay 93 is therefore open not only at the springs 83 The register controlling equipment now so awaits the sending of the second series of impulses indicating the unit digits of the desired line. As in the former case the first denergizing of the relay 91 causes the energization .of the, relay 92 which again locks 85 itself up through its left-hand winding, an

prepares the circuitfor the stepping magnet of the register controller, this time, however, for the stepping magnet 96 of the units register controller, this circuit also being prepared by the closure of the springs 83 top and 84 top. Upon the subsequent energization of the relay 91 the stepping magnet 96 moves the disk of the units register controller 97 one step from normal in a clockwise direction. Here again both the impulses and the periods between impulses allow the energization 0r deenergization of the stepping relay 91 for an insufficient time to cause the energization of the relay 93. 100

Consequently for each impulse the disk 9.7 of'the units register controller will be moved one step from normal in a clockwise direc-. tion. At the end of the third impulse, however, in the case assumed the circuit will be closed for a longer period, and the slow acting relay 93 will be energized and close the circuit to move the sequence switch 80 from its fourth into its sixth position. As

the sequence switch 80, however, moves out of its fourth position, springs 83, 84, and 89 are opened, and the relay 93 will be deenergized, since relay 91 is now maintained continuously energized except in case of the premature disconnection by the calling suhscriber, which will be hereinafter considered. The register sequence switch 80 will therefore remain in its sixth position, in which position the tens selection controlling operation in the selector switch shown will take place. 7

In position 6 of the. register sequence switch 80 the fundamental or selection controlling circuit will be closed at the spring 87 and the back contact of the relay 95 to 12.5

energize the line relay 56 of the selector switch, and stepping relay 94 of the registering and controlling equipment. Relay JG energizing drives the sequence switch 20 into its fifth position over a circuit including spring 24 bottom. In the 5th position of the sequence switch 20, the relay 56 being maintained energized, circuit is closed for the tripping spindle power magnet 57 over the spring 35 top and such tripping spindle moves to bring the projections thereon successively into position to trip the various sets of brushes on the brush carriage of the group selector in the well-known manner. As the tripping spindle moves each step or stage that part of the fundamental circuit including the stepping relay 94 is shunted (ground, 69, 38, 94:, 87, ground) and causes the deenergization of such relay while line relay 56 is maintained energized. Of course as the respective projections on the tripping spindle are brought into proper position to trip the corresponding set of brushes, the shunting circuit is opened in the well-understood manner.

When the fundamental circuit was first closed stepping relay 94 closed at its front contact a circuit over spring 85 bottom to energize the restoring magnet 78 of the tens register-controller 77. This caused the disk of the tens register controller to move one, step in a restoring direction, that is, the counter-clockwise direction, and upon the deenergization of the restoring magnet 94 the stepping relay 7 8 is de'e'nergized to prepare for a second step in such direction. Obviously each time that the stepping relav 94 is energized and deenergized the disk of the register controller 77 will take a further counter-clockwise step. When, however, the disk of the tens register controller has taken five steps in a counter-clockwise direction 2'. 0., when disk 77 reaches its normal position, the contact 79 will be closed, and when the relay 94 is deenergized by the closing of the shunt at the tripping spindle, circuit is closed from grounded battery through such siring 79, sequence switch spring 86 top, the wlnding of relay 95, and the back contact and armature of relay 9% to ground, to energize the cut-off relay 95 which opens the fundamental circuit and at the same time drives the sequence switch 80 out of its 6th position. The opening of the fundamental circuit b the cut-off relay 95 took place on the 5th ei nergization of the stepping relay 94, that is, as the tripping spindle closed for the fifth time the shunt of the fundamental circuit, which closure took place as the projection of such tripping spindle adapted to release the fifth set of brushes upon the .brush carriage was coming into position wherein subsequently such set of brushes would be released. The fundamental circuit being open as the tripping spindle comes fully into such position, both circuits for the line relay 56 are opened and, such relay being de'nergized, the tri ping spin- 6.10 is brought to a stop and t e sequence switch 20 is driven by a circuit including spring 24 top into its 6th position.

As the sequence switch 80 reaches its 8th osl tion the sequence switch 20 is already in its 6th position and the fundamental circult is again closed by the spring 87 to enargue the stepping relay 94 and the line relay 56. The energization of the stepping relay 94 causes the first step of the disk of the units register controller 97 over a circuit including spring 85 top in the usual manner. The energization of the line relay 56 drlves the sequence switch 20 into its 7th position. In this position such relay being maintained energized a circuit is closed over spring 36 to energize the brush carriage power magnet 59 and the brush carriage will start in motion. In the first portion of this motion the proper set of brushes, that is, the fifth set, cooperating with sets of terminals of lines numbered from 40 to 49 will be released by the tripping spindle. Subsequently as the released brushes come into cooperative relation with the sets of contacts the interrupter 60 causes the intermittent closure of the contact 62. The closure of this contact takes place each time as the brushes are about to come in contact with the respective set of terminals with which they cooperate; the contact 62 being closed Once for each set of terminals with which the brushes make connection, being open only when the brushes are properly centered upon such terminals. Therefore, before the brushes come in contact with the first set of terminals the contact 62 of the interrupter will once have closed a shunt for that portion of the fluidamcntal circuit including the stepping relay 9 to dccncrgize such relay. As the brushes come squarely in contact with the first set of terminads this shunt will be opened and the relay 9% will be again ener gized to produce a second step in a counterclockwise direction by the disk of the units register controller unless such disk is already in its normal position. As, however, the disk has been set three steps in a clockwise direction the relay 94 will be energized three times before, on its third det nergization, a circuit is found closed for the cut-01f relay 95 including the springs 86 bottom and 99. \Vhen this occurs the selected brushes of the selector are in contact with the third Set of contacts in the selected bank. The energization of the cutoff relay 95 has the fundamental circuit at the back contact of its armature and has driven the sequence switch 80 out of its 8th position and intduts 9th position, in which position the fundamental circu t is opened at spring 87. When the circuit through the interrupter contact 62 is now opened as the selected brushes come squarely in contact with the third set of contacts on the selected level, that is, co

opened tacts of the line No. 42 (the desired line) no circuit will exist for the line relay5(i, and such relay deenergizing opens the circuit of the power magnet 59 and closes a circult over spring 37 top for the holding magnet 63 of the selector brush carriage, thereby bringing such brush carriage positively to a stop w1th the selected brushes accurately centered upon the terminals of the desired line- The deenergization of the line relay 56 at this time also drives the sequence switch 20 out of its 7th and into its 11th position.

Before considering what occurs in the selector apparatus as the sequence switch 20 leaves its 7th position, it will be observed that the sequence switch 80 on coming into its 9th position closes a circuit for the relay 95 over spring 86 top which includes the normal contact 79 of'the tens register controller so that relay 95 energizes and drives the sequence switch 80 into its 10th position. In the 10th position a circuit is closed for this same relay over the spring 86 bottom and the normal contact 99 of the units register controller to energize such relay to drive sequence switch 80 into its or normal position. It will'be observed that if either the tens re ister controller or the units register contro ler had for any reason been left out of its normal position, as, for example, in case'of premature disconnection. which will be hereinafter described, it would be restored to normal position in the 9th and 10th positions respectively of the sequence switch 80. Assuming that the tens register controller was off normal when this sequence switch reached its 9th position the circuit described for energizing the relay 95 would. not have been closed but a circuit would have been closed for the restoring magnet 78 of such tens register controller including spring 85 bottom and spring 90, which would include the interrupter 75, and the restoring magnet 78 would have been intermittently energized until the tens register controller is again in its normal position, when the relay 95, bein r energized, the sequence switch 80 wouwd move out of its 9th position. Correspondingly, if the units register controller was off normal the restoring magnet 98 thereof would be intermittently energized over a circuit including the interrupter until upon the energization of the relay 95, when the spring 99 is closed as its register controller comes into its normal position, the sequence switch 80 is driven from its 10th position into normal position. During the movement of the sequence switch 20 through its 10th position, the test of the desired line on the terminals of which the selected brushes now rest is made by the relays 50 and 51. If the desired line is idle full potential of the battery connected to the cutoff relay thereof will appear upon the test pass through such relay ands terminal thereof. This will be suflicient to energize the test relay 50 through its high should be observed that the test circuit in eludes the front contact of the calling supervisory relay 64 so that in case of a premature disconnection the selector switch will not seize the desired line in the manner to be described, but the operations thereof will proceed in the same manner as though the desired line had been found busy. The calling supervisory relay 64 is energized at this time in a normal call by the battery shown between the terminals of the repeating coil, springs 33 bottom and 34 top having been opened and the springs 33 top and 34 bottom closed upon the completion of units solection to include the left-hand branches of the repeating coil in the circuit of thecalling subscribers line. As long, therefore, as the circuit is closed at the calling subscribers sub-station the calling supervisory relay 6i will be maintained energized. On the test of the desired line in position 10 as soon as the relay 50 was energized upon such line being found idle, the closure of the loweresistance path through the right-hand wind ing of suchrelay so reduces the potential upon the test terminal of the desired line that no other selector switch testing such line would find suflicient potential uponthetest terminal thereof to cause the energization of its test relay 50. At the same time that the relay 50 is energized the cut-off relay 65 of the desired line is energized to prevent the energization of the line relay thereof when the called subscriber answers. Therefore, when such subscriber does answer no selectable potential will be placed upon the test terminal of such line, corresponding to the test terminal 47 of the calling line, in the line finders where such line appears. Assuming that the desired line is found idle, as the seoueuce switch 20 reaches the 11th position the re 1a 51 which has been energized with the re ay 50 will be maintained energized by the circuit including the armature of such relay 50 and the sprin 28 top in spite of the fact that the spring 29 bottom is open. A circuit will therefore be closed over spring 26 bottom to drive the sequence switch 20 through its 11th position and into its 12th positlon.

The 12th position of the sequence switch 20 is the ringing position. In this position ringing current the s ource of whichjiSindicated adjacent to the ringing i'layafitii will prihg 39 top scribers line, finding groft "d orerspring 40 bottom. So long as theg ealled-subscribeWs circuit is maintained open to direct current,

his receiver being upon its hook, insuflicient ringing current'will pass through relay 66 to energize such relay. When, however, the called subscriber answers the cireuitto'direct current will be closed at the substation, and suflicient ringing current will pass through relay 6 to energize such relay, and circuit is closed to drive the sequence switch '20 out of its 12th position and into its 14th position. This is the talking position of the sequence switch 20, and the springs 39 bottom and top being closed, talking connection is now extended from the calling subscriber 41 to the called subscriber 42. Conversation may now take place.

lh'sco nnectiom Di connection in the system shown is under th control of the calling subscriber,-but, in case the called subscriber should not immediately replace his receiver on its switch book after the calling subscriber has done so, means are provided whereby the called subscribers line will take upon itself the character of a calling line and thereby engage and make busy some other line finder and its associated connected circuit. Upon the opening of the circuit at the calling subscribers substation the calling supervisory relay 64 will be deenergized.

This will drive the sequence switch 20 out of its 14th and through its 15th positions into its 16th position by a circuit including the spring 22 top. In the 16th position the sequence switch awaits the opening of the circuit of the called subscribers substation, which, as soon as it occurs, causes the deenergization of the called supervisory relay 67 and drives the sequence switch 20 out of its 16th position and into its 17th position over a circuit including spring 30 bottom.

It should be noted that as the sequence switch left its 15th position the opening of the springs 30 top, 33 top and 34 bottom rendered the calling subscribeNs line free to subsequently call or be called and be connected to by any selector or by any idle line finder of the group in which it appears. As the sequence switch 20 came into its 17th position the closure of the spring 23 top makes a test to determine whether the registering and controlling equipment is again in normal condition. If such is the case, that is, if the sequence switch is now in position 1 a circuit is closed over springs .74 bottom and 23 top to drive the sequence switch 20 into its 18th position. In this position the brush carriage power magnet 59 is energized over a circuit including the spring 25 top, back contact of relay 51, spring 26 bottom and back contact of relay 56. The brush carriage now restores, the released brushes being restored in the usual manner in such. movement." 'When the brush carriage reaches its normal position the interrupter brush 60 comes in contact with tripping spindle has been restored by a circuit including the spring 35 bottom in the 16th, 17th or 18th positions of the sequence switch 20 all of the apparatus which has been used is again in its normal position.

Attempted connection to a busy line.If when the sequence switch 20 'was passing through its 10th position the line desired had been busy, the normal potential upon the test terminal thereof in the selector would have been reduced either by the connection of some other selector switch and the connection of a low resistance circuit through the right-hand. winding of the test relay 50 thereof to such test terminal if such line were busy as a called line, or by the connection of a circuit including the spring 30 to to the test conductor leading to the cut-o "rela thereof it such line had been busy as a calling line. Insufiicient current would, therefore, have assed through the high resistance left-hancFwindin of the relay 50 of the testing selector, an such relay would not have been energized. Therefore, when the sequence switch 20 came into its 11th position, no circuit would exist for the relay 51 and such relay not being ener ized in such position the sequence switc 20 would stop. The un-energized condition of the relay 51 in this position would cause the restoration of the selector switch to normal, a circuit being closed for the power magnet 59 thereof through the spring 25 top, back contact of relay 51, spring 26 bottom and back contact of relay 56. The brush carriage would therefore be restored to normal precisely in the manner hereinbefore dethen replaces his receiver upon its switch hook, opening the circuit at his substation, and causes the decnergization'of the calling supervisory relay 6-1. This closes a circuit to drive the sequence switch 20 out of its 15th position. As the called supervisory re- In this posi-.

lay 67 is at this time deenergized the sequence switch will be moved into its 17th position. It beingassumed that the register controlling equipment is again in normal position 5 the sequence switch will continue to move intofits 18th position. The selector switch "beingin itsnormal positiona circuit will be established for the relay 56, which, on-energiz'ing; drives the sequence switch 20 into 1 its first ornormal position, andall the apparatus is. again in normal condition.

*Prerridturdisconnection-71f the called suhs'cribershould'not answer in response to the ringing current projected upon his line 5 in the 12th pd'sitionof'the sequence switch 20, the calling subscriber'may producerestoration by merely replacing his receiver upon its hook; This is accomplished by the deenergization of the relay 64 in the 12th or ringing position, which closes circuit over spring 22 top, to drive the sequence switch directly intoits 16th position, where restoration will take place in the normal manner, the called supervisory relay 67 being already retracted. If the calling subscriber should replace his receiver during the 11th position, the apparatus would move in the normal manner into the 12th position of the sequence switch 20, when'restoration wouldtake place as described. If the calling subscriber should replace his receiver during the 8th or 9th or 10th positions of the sequence switch 20 the circuit for the relay 51 would not be closed either at the spring 31 or the front contact of the calling supervisory relay (34:, and therefore neitherfthe relay 50 nor the relay 51 would be energized in the 10th position and the same condition would exist as though the called line were busy, the selector switch restoring to its normal position in the 11th position and the sequence switch moving on into its th position. It would not stop in this position, "however, as the .circuit isclosed therefor over spring 22 top and the back contact of relay (34, and the apparatus would be restored to normal in the manner hereinbeforedescribed. If the calling subscriber should restore hisre'ceiver to its hook at any time while the sequence 0 switch is in positions 2 to 7 the stepping relay 91 is denergized for a relatively long period, thereby ca ing the energization of the slow rela" {a circuit including ontact of such relay cling energized, closes a "sequence switch 80 directly into its 9th os ion.

In the 9th position of the sequence switch 80 the spring 74 is closed to drive the sequence switch 20 into its 8th position, where the restoration of the sequence switch 20, the selector switch (if it had been moved from normal) and the apparatus associated therewith would take place in the manner hereinbefore described. In the 9th position of the sequence switch 80 if the tens register-controller is in normal position, either in the event that it has not been moved from normal or that it has been restored to normal in the normal operation of the system, the sequence switch moves to its 10th position, where a corresponding test would be made of the position of the, units register controller, which, if is found in its normal position causes the movement of the sequence switch'80 into'its normal position.

In case either the disk of the tens register controller 77 or the units disk of the register controller 97 had been off normal such disks would have been restored in the 9th or 10th position of thesequence-switch respectively in the manner hereinbefore described. Itwill be observed that in case of premature disconnection of this character,

if both the tens register-controller and the units-registcr controller. were oil normal it might be that the sequence switch 20 would reach its 17th position before-the restoration of the register controller disks had been completed. In this case the sequence switch 20 would remain in its 17th position as thecircuit therefor from the spring 23 top'is opened at the spring 74 bottom of the sequence switch 80. When, however, the register controlling apparatus is again in its normal position the spring 74 bottom will be .closed and the sequence switch 20 will move into its 18th position, from whence it will be moved in the normal. manner into its normal position, if the selector switch is already in normal position or when such selector is restored to normal position if it is at that time not at normal.

What is, claimed is z? 1. In a telephone exchange system a plurality of automatically operable multiposition switches, an external control circuit, a quick-acting relay in said circuit, a slowacting relay, controlled by said quick-acting relay, and a second quick-acting relay, said quick-acting relays and said slowacting relay cooperating to control the setting,- changeover and restoration of said switches in accordance with circuit changes in said control circuit.

.2. In a telephone exchange system a plurality of automatically operable multiposi tion switches, means for moving said switches in a forward direction, means for restoring said switches in the opposite direction, an external cohtrol circuit over which the setting, changeover and restoration to normal of said switches is controlled and a single slow-acting relay controlled by circuit changes in said circuit and controlling the restoration to normal of one of said switches and the changeover from one of said switches to the next to be operated.

3. In a telephone exchange system a control circuit, a plurality of automatically op-.

erable multiposition switches adaptedto be one after another brought into association with said circuit to be set by series. of short impulses therein and asingle slow-acting relay associated with said circuit responding to aprolonged closure thereof to produce the changeover from one of said switches to the next to be set, and'responding to a prolonged interruption' of said circuit to produce the restoration to normal of said switches.

4. In a telephone exchange system, acontrol circuit, a plurality ofautomatically op-' crable multiposition switches adapted to be one after another brought into association with said circuit to be set by series of short impulses therein,-itwo quick-acting relays, one included in said circuit, directly controlling the setting of said switches, and a single slow acting relay cooperating with said quick-acting relays and controlling the changeover from one of said switches to the next to be operated and the initiation of restoration of said switches to normal.

In witness whereof, I hereunto subscribe my name this ninth day of July, A. D., 1914.

WILLIAM HUGO MA,TT HIES.

- Witnesses:

F. J. WoooWARn,

HENRY ALBERT J ormson.

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