US1448420A - Telephone-exchange system - Google Patents

Description

Mar. 13, 1923.

P. C. SMITH TELEPHONE EXCHANGE SYSTEM Filed Sept. 50 1919 5 she eta-sheet 1 Mar, 13, 1923.

P. c. SMITH TELEPHONE EXCHANGE SYSTEM Filed Sept 50, 1919-.

5 sheets-sheet 2 Mar. 12., 1923. 1,448,420

P c. SMITH I TELEPHONE EXCHANGE SYSTEM Filed Sept. 50, 1919 5 sheets-sheet 5 Patented Mar. 13,

TPJC COMPANY,

' YORK.

ESTER, MASSACHUSETTS, ASSIGNOR T0 ESTERN ELEC5 A ooarom rron OF NEW TELEPHONE-EXCHANGE SYSTEM.

Application filed September 30, 1919. Serial No. 327,545.

T 0 all whom it may concern Be it known that I, PERCY C. SMITH, a

citizen of the United States, residing at This invention rel terns, and

Worcester and have invented cer- T eleof whiclithe folates to telephone sysmore particularly to systems in which the talking connection from the callingto the called subscribers line is established by means of automatic or mechanically controlled switching devices.

.Heretofore it has been the common practice to extend a calli ng subscribers line to an idle selector switch by means of a-switch of the rotarytype,.eithei individual to the calling line or individual to the first selector trunk.

obviate the necessity of employing switches by providing a connecting thereby avoiding rotary of the relay type, switch parts, increas Theobject of this invention is to rotary switch ing the speed of connection, and simplifying the switch structure.

In its broadest aspect the invention resides in the provision ofa ing a capacity for serving ing lines and having access switch preferably havone hundred callto a group of ten trunks, which is adapted, to extend a calling line terminating therein,

to a pre-selected trunk line through the operation of a single relay individual to the calling line.

The

line extension is therefore substantially instantaneous and need not be delayed during the search for an idle trunk as has been necessary in systems employing rotary finder switches.

nets and so co-ordinated one for each calling line relays is necessary,

that a minimum of having access to the switch and one for each trunk outgoing from example in aunit serving one the switch. Thus for hundred: lines and having access to ten trunks there are only one hundred and ten relays.

The invention will now be describedin connection with one specific embodiment of the genus of my invention. In the accompanying drawings:

Figures 1 and 2 w hen placed end to end with Fig. 2 at the right of Fig.1 show a diagram of circuit connections illustrating the manner in which my inventionis incorporated in an automatic telephone system. Fig. 1 shows the circuit of my improved line switch and selector anda connector switch; v Figure 3 is a front elevational view of my improved line switch unit, the trunk pre-selecting relays having been omitted for the sake of clearness; v c i I Figure 4 is a vertical sectional View taken on the line H of Fig. 3;

Figure 5 is a transverse sectional view taken on the line 5-5 of .Fig. .4; i I Figure 6 is a detail plan :view of-one of the trunk pro-selecting relaysyand Figure 7 is a detail elevational view of the line extending relays.

Any step-by-step' two-movement switch may be employed with-the ci-rcuitsshown. A switch. of this general character is shown in the patent to Keith and Erickson No. 815,176, althoughpreferably a switch so. constructed as to operate the circuits disclosed in the patent to Martin No. 1,155,672 is employed. Although the features, of the inventionv are of one above referred to, they ,are equally applicable in a system employing ,switches of other types, as forexainple, power driven switches. 7

With each directively controlled switch is associated a circuit changing device for controlling the operating circuits of its respective switch. These devices vmay be of the generalcharacter of the switchwhich is shown in Keith and Erickson and. referred. to as a side switch.

Referring toliigs. 3 to 7 inclusive of the drawings, I have disclosed animproved line Fig. 2 shows the circuit of a disclosed in-jasystem employ lllgStQP-bY-SllQP switches of the general type the above mentioned patent to 1 these vertical bars being provided upon their ends with out-turned extensions by means of which they are secured to the top and bottom plates by machine screws 7.

Supported between the vertical bars 8 and at is a series of super-imposed relays or line 'magnets 8, preferably fifty, and supported between the bars 5 and 6 is a second series of similar relays, the relays of the two series being positioned back to back as most clearly disclosed in Fig. 4-.

Each relay 8 comprises an L-shaped tail piece 9 having a vertically disposed arm 10 and a forwardly extending horizontally disposed arm 11 bent downwardly at each end as at 12 and 13 for attachment to the vertical frame bars. In Fig. 3 the extensions 12 and 13 are shown attached to the "frame bars 3 and 1 by machine screws 14:. The exte sions also serve to space the superinnoosed relays at suitable intervals from each other, the extensions of the lowermost relay spacing that relay from the bottom plate 1 and the extensions of each sue essive relay resting upon the horizontal arm 11 of the relay tail piece next beneath it to space such relays apart. Extending horizontally from the arm 10 of the tail piece is a core-piece 15. This core-piece lies parallel with the 11 of the tail piece and extends substantiallythe whole length of the tail piece. Wound upon the core-piece 15 is a double wound winding comprising a high resistance operating winding 16 and a low resistance looking or holding winding 17.

The forward edge of the horizontal arm 11 of the tail piece is suitably notched and between the projecting ears 18 thus formed, a plurality of depending armatures 19 are pivoted by means of a pivot pin 20 extending through apertures in the ears and in the armatures. Each relay is preferably equipped with ten armatures which are adapted to be attracted toward the core piece 15, the magnetic circuit for each armature comprising a core 15, the vertical arm 10 of the tail piece 9, the horizontal arm 11 thereof and the armature.

Normally each armature of each relay is held away from the forward end of the core 15 by means of a finger 21 secured to the front face of the armature as by rivets 22, and engaging a hooked spring 23 secured to the tail piece 9, a distance suflicient to remove the armature from the influence of the core 15 so that in such position it is not possible for the core 15 to attract the armature. The retractive movement of each armature is restrained by the engagement of the rearwardly extending portion 2 1 of the spring 21 with the arm 11 of the tail piece. Each armature through the finger 21 is adapted to control a set of contact springs as shown most clearly in Fig. 7. The ten sets of springs of each relay are suitably mounted between strips of insulating material and are supported upon the tail-piece of the relay by screws 25. The springs of the several relays of the switch unit are multipled together in the manner shown in Fig. 1.

Pivotally supported in plates'29 and 30 secured to the top and bottom plates 2 and 1 respectively of the switch, immediately in front of the armatures of each series of relays 8, is a group of ten vertically disposed rods or actuating bars 26. Each rod is assigned to an outgoing trunk line and is provided with a series. of fifty pins. 2-7 for cooperation with an armature of each of the series of fifty relays. Thus the first trunk rod of each group is adapted to cooperate with the No. 1 armature of each relay, the second trunk rod of each group with the No. 2 armature of each relay etc. Normally these rods stand in a position with their pins resting upon the widened portions 28 of the fingers 21 of the arma-tures, permitting the springs 23 to force the armatures away from the pole pieces of the relays and out of the magnetic influence thereof. Upon the rotation of one of these rods the pins 27 Lin thereon force an armature of each relay toward the pole pieces of the relays so that upon a subsequent energization of one of the relays its armature which has been positioned by the rotated trunk rod 26 will be attracted.

For the purpose of rotating the trunk rods 26, ten magnets 31 are provided. F or convenience in mounting and to enable a more compact arrangement of the switch, these magnets are divided into two groups secured respectively upon opposite sides of the switch and preferably at a point midway of its height, to bracket members 32 attached to the upright members 8, 4, 5 and 60f the switch frame by screws 33. Each magnet comprises a tail-piece 34- having a horizontally extending portion 35, a core 36 and a winding T, the portion35 also extending downwardly below the lower edge of the tailpiece at to form means by which the magnet is secured to the bracket member 32, as shown most clearly in Fig. 4. Any suitable means of attachment may be employed such as screws 37.

Secured to each rod 26 is an arm 38, the arms of alternate rods of each series of rods extending from the rods in the same direction and serving as armatures for the magnets 81, the arms of the remaining intermediate rods of each series extending in the opposite direction, as most clearly disclosed in Fig. 5. The arms 38 of corresponding rods of the two series, that is of rods individual to the same trunk and positioned on opposite sides of the switch frame, are interlinked by links 39 secured to the arms by screws 40 in such manner that when a trunk magnet 81 attracts an arm 88 of a trunk rod 26. which it controls, the trunk rod 26 corl. l. O

. snaps back of the piece 34 and side of the switch serve as armatures, the

ari'ns of corresponding rods upon the opposite side of theswitch and linked thereto, serving merely as rocker-arms for transmitting the reciprocatorymovement of the connecting links 39 into a rotary movement ofthe rods 26.

The armature arms 38-are normally held in retracted position, by springs 41 secured thereto by pins 42 and'connccted to 'a central bar 43 by pins'44, the bar 43 being se-' cured at either end to the bracket members 32 vby screws 45. In its retracted position each of these armatures maintains a pair of contact springs 46 and 47 in contact by means of a stud 48of insulating material attached to the backof thearmature and resting against the end of spring 46, but permits the springs to separate when attracted toward its core36; The springs are 1 suitably insulatedvfrom each other and insulatedly mounted upon a bracket strip 49 extending between the side bars of the switch frame. As shown most clearly in. Fig. '6 the tail piece 34 of the magnet 31 is extended into close-associationwith the rod 26 which it controls to establish a substantially closed magnetic circuit between the tail piece and the armature 38 thereby increasing the chiciency of the magnet. r

After having been rotated by the magnet 31 through the energization of the winding T the trunkrod '26 is locked in its rotated position by a hook member 50, which is pivoted to the member 35 of the magnet asby a screw 51 and which engages the .end of the armature 38. The hooked end of the member is urged toward the: end of'armature 38by a spring52 which is-secured at its ends to the hook member andto the armature by pins 53 as most clearly shown in Fig. 6. Normally of the armature 38 the beveled end 54 of the hook rests in contact with the, beveled end of the armature 38 as shown in Fig. 5 but hook upon being attracted. The locked up armature is released by means of a releasing magnet R- which is mounted upon the tail piece .34 withits core 55 secured in the extension. 35 of the. tail piece in alinement withthe core-piece 36 of the winding T. The two magnets R- andT3 thusare united in a single unit but have separate magnetic circuits. The armature 56 of the I magnet R is pivoted to the'end of the tail held in its retracted position in' the "retracted position by :means ofa spring 57 secured to the end of the armature and to .thetail-piece by pins 58.

The with a laterally extending pin 59 which engages the cammed end=60 .ofthe hook member 50. Up winding R the armaturethrough the pin- 59,- forces :the left hand end .of the hook member 50 toward the magnet windingasviewed in Fig. 6,- thereby. moving the hooked end 54 away from'theflend .of armature'38to release it.

Having thus acter of the apparatus which is. used in the system embodying. the principles'ofmy invention, I'Will'DOW describe the. process by which a calling subscriberv A whose station is illustrated .at the left in Fig. 1, establishes connection with the subscriber A Whose station is illustrated. at the right in Fig. 2 and whose exchange number :we 'will assume to be 225.

When the subscriber A removeshis receiver preparatory tomaking a call, a circuit iscompleted in the usual manner through the windings of the line relay '61,

which is energized and completes a circuit;

from grounded battery, through winding 16 of the relay 8, and throughthefront'contact of relay 61 toground. The connecting relay 7 tion that trunk No. VII leading toa group of first selectors to which the group of lines in which subscribers station A is located,

described the general char- 8 is energizedand-upon the assumpfree end of: armature 56 isprovided v on energization of themagnetf has been preselected for use in a manner hereinafter described and the trunk'rod 26 has positioned the No.4 armaturejof each connecting relay 8 of the group of lines in a position to'be attracted by therelay 8, the armature '19 of the calling s'ubscribers connecting; relay will be attracted. 'Since however the remaining armatures of theenergized relay8are normally out 'of the field of magnetic influence of the; relay, they are not attracted. The armatures of the re maining relays of the group which have been positioned by tracted at thistime since'their respective relays 8 are not energized.

Uponthe attraction of thearmature 19 of relay 8 the set of normally open contacts with which it cooperates ;is closed. The' closure ,ofcontacts- 62 and 63, and 64 w and 65 extends the talking conductors of the calling line by the' heavy conductors to the line relay 66 of the. idle first selector'E which has been 'pre-selectedfor; use. This circuit. extends Fig. 2, through the left hand-winding of the line relay66, through the first position contact andwi-per- 67*of the sideswitch of the first selector,overthelowerhcavy trunk conductor to the spring 62, through the spring 63,- through the-calhng subscribers line'loop,

the trunk rod 26 are not aty from grounded battery in through the springs 64 and 65, over the upper heavy trunk conductor, through. the side-switch wiper 68 and its first position contact, through the right hand winding of the line relay 66, and back to the ground.

The line relay 66 energizes and closes a circuit for the slow acting release relay 69, shown at the right in Fig. l, which extends from grounded battery, through the winding of relay 69, through the front contact and armature of relay 66 to ground. Relay 69 upon energizing closes a locking circuit for the relay 8, an energizing circuit for the cut-off relay of the calling line, closes an energizing circuit for a trunk relay T of the next idle trunk of the group of trunks-to which the line switch has access, and prepares the stepping circuit of the selected first selector. The locking circuit of the connecting relay 8 may be traced from grounded battery through the locking winding 17 of the relay 8, through the closed contacts'70 and 71 of relay 8, through the closed contacts 72 and 73 of relay 69, to ground. The locking winding 17 while energizing the relay 8 sufiL ciently to maintain its armature 19 attracted, does not provide a sufficiently strong energization to attract other armatures should other trunk rods be operated to position other of its armatures within the field of force.

A branch of the locking circuit just traced extends through the winding of. the cut oif relay 74 of the calling line to grounded battery. This relay upon energizing opens the circuit of the line relay 61 in the usual manner, which upon deener izing opens the initial energizing circuit t rough the winding 16 of the connecting relay 8.

Upon the energization of the relay 8 a circuit was also closed through the releasing or unlocking magnet R which extends from groundedbattery through the winding R through contacts 7 5 and 76 to ground. The magnet R upon energization attract-s its armature 56, thereby oscillating the hook 50 to release the locked up armature 38 of the trunk magnet T which upon releasing permits the restoration of the trunk rod 26 under the influence of the spring 41. The rod 26 in turn permits the restoration of all the armatures of relays 8.which it controls, out of the field of magnetic influence of the relays 8 with which they are associated, with the exception of the armature 19 of the energized relay 8 which throu ,,h the influence of holding windin 17 is malntained attracted.

When the relay 69 became energized it closed a circuit to preselect another idle trunk for the next call, and assuming that the next trunk in the series No. VIII is at this time idle, a circuit is established for its winding T which extends from grounded battery through the windin T through the normally closed contacts I7 and 7 8 of the release relay individual to the selector to which the trunk N 0. VIII extends, through the alternate contacts 116 and 79 of the energized relay 69 through the contacts 80 and 81 corresponding to contacts l6 and 47 disclosed in Fig. 4 of magnet T of the trunk seized by the calling line, which contacts closed when the armature 38 was re leased as above described, and back 'to round. Upon the energization of winding T the trunk rod 26 of trunk VIII is rotated to position the armatures of the re lays 8 as previously described, and is locked in the rotated position by the hook member associated therewith independent of the 0011- tinued energization of relay 69. I

If upon the energization of the relay 69 the next trunk VIII had been busy, the following circuit for the magnet winding T of trunk No. IX would have been established from the grounded battery, through the winding T through the normally closed contacts 82' and 83 of the releasing relay associated with the trunk IX, through the alternate contacts 84 and 78 of the release relay associated with the busy trunk VIII, through the alternate contacts 116 and 79 of the energized release relay 69 of the busy trunk VII, through the contacts 80- and 81 of the magnet T of the trunk seized by the calling line, and back to ground. It is thus apparent that the trunks are seized in rotation.

The foregoing operations occur upon the removal of receiver at the sub-station A, and before the impulses are sent in for the first digit of the desirednumber. hen the subscribers dial 8 is operated in the usual manner for the first digit two, it causes the subscribers line to be momentarily opened twice, to break. the energizing circuitof the line relay 66 of the selector E twice. The release relay 69 being slow-acting, does not de-energize, as its circuit is momentarily broken at the front contact of the relay 66; therefore the engagement of the armature of the relay 66 with its back contact completes a circuit for the primary stepping magnet PM of the selector E which extends from grounded battery, through the side switch wiper 85 and its first position con tact, through the winding of the primary magnet PM, through the winding of the slow-acting relay 86, through the alternate contacts 87 and 88 of the slow-acting relay 69, through the back contact of line-relay 66, and back to ground. The primary magnet PM energizes twice over this circuit to lift the shaft and shaft wipers two steps opposite the second level of bank contacts.

The relay 86 energizes on the first impulse,

but, being slow-acting, does not de-energize until the last impulse is sent in. In its energized position the relay 86 completes a circuit through the private magnet ESQ over acircuit extending from grounded battery through the'winding of the magnet E50, and through the front contact to relay 86 to ground. As soon as the slow-relay 86 tie-energizes, the circuit of the private magnet is broken, which in' turn de-energizes and permits the side switch to pass to the second position. The passing of side switchwiper 85 to second position shifts the battery connection from the primary to thesecondary magnet SM. The wiper 89 in second position, connects the private wiper 9O wit-h the private magnet ESC. As soonas thebattery is shifted to the circuit of the secondary magnet SM, a circuit is closed extending from grounded battery, through the side switch wiper 85 and its second position contact through the winding of the slow-acting relay 91, through the winding of the secondary magnet SM, through the armature and back con-tact of the magnet SM to ground.

The secondary magnet energizes over this circuit to rotate the shaft and shaft wipers one step, breaks its own circuit at its armature and contact,- and presses down the private magnet armature. The breaking of its own circuit at its armature contact causes it to' de-energize. idle, the private magnet armature will return to normal position, thereby permitting the side switch to pass to third position. If, however, the first contact is busy, the first private bank contact will have a guarding ground upon it, as will be explained later. The private wiper,- 90,.upon engaging, the grounded contact, completes a circuit extending from the bank contact through the private wiper 90, side switch wiper 89-(in second position) and winding of the private 'inagnet ESQ to grounded battery. Thus it is evident that the mains insecond position, and, consequently, the'secondary magnet continues to energize to ro'tate'the'shaft and shaft wipers to an idle contact.

The passing of the side switch wipers 67 and 68 to third position extends the calling line to the connector F. The extending of the line to the connector closes the circuit of the line relay 92 of the connector in the same manner as it did that of the relay 66 of the first selector. The-energizing of the relay 92 closes a circuit through the slowacting relay 93, which energizes to provide a holding circuit for the relay 69 over a circuit extending. from grounded battery through the winding of the relay 69, through the back contact and 91, through the third position contact and side switch wiper 89, over the private wiper 90, and the corresponding bank contactof all the selectorsthat haveacc'ess tothe connector F, through the front contact and armature of the relay 93, and "through the side If the first contact is side switch re-' armature of the relay switch wiper 94k and its first position contact to ground. A short period of time elapses between the time that the side switch wiper 89 leaves the second-position and the time that theguarding ground is supplied to the private bank contact by the connector.. The relay 91 is put in for the'purposeof supplying a guarding ground to theprivate bank contacts during this time. It wilhbe remembered that therelay 91 was energized in series with the secondary magnet and, being a slow relay, it remains held up a short time after theside switch has passed to third position, thereby putting. a ground on the private wiper from ground at its front contact, through its armature in its alternate position through the side switch wiper 89 and its" third position contact to theprivate wiper 90. It is evident that the relay 69 must be slower than the relay91 to prevent the selector from releasing. The apparatus is now ready for the second digit two. I

The subscriber A operates the dial for the second digit in the same manner as for the the first digit. The relay 92 de-energizes twice to close a circuit through the primary magnet PM extend-ing fromgrounded battery through the winding, of the slow-acting relay '9 5,through the side switch wiper 96 and its first positionc ontact, through the winding of the primary magnet PM, through the front contact and left hand armature of the slow-acting. relay 93, and through the back contactandarmature of thelinerelay 92 to ground. The primary. magnet PM energizes over this c cuit to raise the shaft and shaft wipers 9i, 8 and 99 two steps and opposite the second vel of bank contacts. As soon as the snaft is lifted. the springs 100 and 101 engage preparing a circuit for the release magnet REL.. The relay 95 alsoenergizes in the circuit with the vertical magnet to cause its armatiires to break with their back contacts and to make with their front contacts. Theleft hand armature closes a circuit which extends from grounded battery through the private magnet ESQ through the left hand armature andfront contact of slowirela'y 95-to ground. The relay 95 remains energizeduntil after the last impulse of the digit has been sent when it de=energizes thereby breaking the circuit of the private magnet.

Upon deenergization of the private magnet,

the side switch wipers escape to the second position. i i i The passing the'side switch wipei'j'96 to the second'p'osition disconnects-the primary magnet and placesv the secondary magnet SM in't-he ci'rcuit with theslow relay 95. The switch is now in position to receive the impulses for the third or last digit five. As the dial is operated for this digit the circuit of the relay 92'is broken five times, as before. The "relay de-energizes five times,

each time closing a circuit extending from grounded battery, through the winding of slow relay 95, through the side switch wiper 96 and its second position contact, through the winding of the secondary magnet SM, through the outer left hand armature and back contact of relay 102, through the front contact and armature of slow relay 93, and through the back contact and armature of line relay 92 to ground. The secondary magnet energizes five times to rotate the shaft and shaft wipers onto the bank contacts of the called line #225. The relay 95 energizes on the first impulse as before, and de-energizes a moment after the last impulse has been sent in, thereby permitting the side switch to pass to the third position. The passing of wipers 103 and 104 to third position connects the calling line to the called sub-station through the condensers 105 and 106. The passing of the wiper 94 from the second position to the third position removes the ground connection, which during the first and second positions of the side switch has been placed on the circuit extending through the right hand armature and front contact of slow relay 93 to the private bank contacts of all selectors having access to the connector F, for guarding the switch F against seizure and for holding the release relay 69 of selector E energized, and connects a new holding ground for this circuit, from the armature and front contact of line relay 92. in its third position the wiper 107 extends a ground connection to the relay 108, and coin pletes a circuit through the inner left hand armature and back contact of relay 102, through the private wiper 99 and back contact to the cutofi relay of the called line (similar to cut-off relay 74: of the calling line). The side switch wiper 96 of the connector in its third position, serves to close a circuit for the ringer relay 109. This circuit extends from grounded battery through the slow relay 95, through the side switch wiper 96 and its third position contact, through the winding of the ringer relay 109, through the left-hand back contact of relay 108, through the ringing interrupter 110 to ground. The ringer relay is energized intermittently todisconnect the calling line and connect the called line with the ringing current generator L. A ringing current then flows from generator L through the front contact and left hand armature of ringer relay 109, through the side switch wiper 10 through the switch wiper 98, through the bank contact and lower line conductor, through the bell 111 at the called subscribers station, through the upper line conductor, bank contact, switch wiper 97, through the side switch wiper 103, through the right hand armature and front contact of relay 109, back to the generator L.

The subscriber at sub-station A removes the receiver in response to the signal, and thereby closes an energizing circuit as soon as relay 109 again de-energizes, should it be pulled up at the time, through the back bridge relay 108 of the connector. This circuit extends from grounded battery through the left-hand winding of relay 108, through the back contact and right hand armature of relay 109, through the side switch wiper 103 through the switch wiper 97, out over the subscribers line, back through the switch wiper 98, side switch wiper 104, left hand armature and back con tact of relay 109, through the right hand winding of back bridge relay 108 to ground at the side switch wiper 107 Thus the called subscriber is supplied with talking current. The relay 108 energizes over the circuit just traced to break the circuit of the ringer relay 109 at its left hand armature contacts.

After the conversation is completed, the release of the central office apparatus used in the foregoing call is initiated by the calling subscriber hanging up his receiver. The release is as follows: The breaking of the line at the sub-station, breaks the circuit of line relay 92- at the connector F which in turn deenergizes thereby breaking the holding ground for the release relay 69 of selector E and for the release relay 93 of connector F. The release relay 69 upon deenergizing closes a circuit for the release magnet REL which extends from grounded battery through the winding of the mag net REL, through the contact 113 and 114 closed when the switch E took its first step oif normal, through the contacts 115 and 88 of the release relay 69, and through the back contact and armature of line relay 66 to ground. The release circuit for connector F, extends from grounded battery through the winding of 'release magnet REL, through contacts 101 and 100, through the back contact and left hand armature of relay 93, and to ground through the back contact and armature of line relay 92. Upon the deenergization of release relay 69, the locking circuit for connecting relay 8 of the calling line and. the circuit through the calling line cut-off relay 7 1 are opened.

The de-energization of the calling line cut-off relay, and de-energization of relay 8, restores all apparatus individual to the calling line to normal. The energization of the selector release magnet REL permits the switch to return to normal thereby separating the springs 113 and 114C. The energizetion of the connector release magnet REL in a similar manner permits the switch to return to normal thereby separating the springs 100 and 101. Thus all apparatus is restored to normal position and in readiness for another call.

-magnet ESQ to grounded battery. The

- have passed to the third positiombut Returning now to that point in the operation of the connector while the'side switch is yet in the second position, had the called line been busy, the side switch would-not would have been locked in the second position by the private magnet remaining energized.

The circuit through the private magnet 3 contact would have been from the bank upon which the wiper 99 is resting, WhlCh. contact would have been grounded, through v the wiper 99, back contact and inner left hand armature of relay 102, right hand winding of back bridge relay 108, back contact and left hand armatureof ringer relay 109, side switch 104 and its second position contact, back contact and armature of relay 95, and through the Winding of private simultaneous energization of private magnet E80 and relay 108, closes acircuit through the busy relay 102. This circuit extends from ground through the right hand armature and back contact of relay 95, through the armature. and front contact of private magnet ESC, through the busy relay 102 and through the right-hand armacontact of: relay 108 to ture and front grounded battery. The relay 102 energizes over this circuit to disconnect the'secondary Y magnet SM at its back contact'and outer left hand armature and to shift the holding ground for relay 108 and private magnet. ESC to ground through its inner left hand armature and front contact. "Relay 102 also causes a busy signal to be sent to the calling subscriber over a circuit extending from grounded battery through the secondary of the induction coil 120 of the busy signalling machine M, through the right hand armature and front contact of relay 102, through the side switch wiper 103 and its second position contact, through the right hand armature and backcontact of ringer relay 109, through the condenser 105, thence over theheavy conductors to and through the contact of the inner sub-station A, back over the heavy conductors through the left-hand winding of therelay 92 to ground.

The object inshifting the ground from the private wiper 99 to ground at the front left hand armature of relay 102 is to prevent the side switch magnet from de-energizing should the guarding potential be'removed before the switch F has been released. The release 1' of the switches in case the called line is busy is the same as if the connection had been obtained. Many modifications of the invention other than those enumerated will readily suggest themselvesto those skilled inthe art, and' the'inventlon should thereforebe limited merely by the scope of the claims.

I claim: I

1. I In a telephone "exchange system, :a subscribers line, agroup;v oftrunk lines, multiple contact sets: for said subscribers line for connecting said line to any one of said trunk lines, a connecting relay for said subscribersline, armatures for said relay each individual to a contact set, means individual to each trunk line for predetermining an armature for response to the energization of said relay, and means for pre-selecting an idle trunk line whereby said last named means is rendered effective. I

2. In a telephone exchange system, a-subscribers line, a group; of trunk lines, mu-ltiple contact sets'for .said subscriber s'line for connecting said line to any one of said trunk lines, a connecting relay for said subscribersline, normally"inoperative armatures for said relay each individual to a contactset, means individual to each trunk line for operatively positioning. an armature for response to the energization of said relay, and means for pre-selecting an idle trunk line whereby said lastnamed means is rendered effective.

'3. In a telephone exchange system,- a subscribersline, a group of trunk lines, multiple contact sets for said subscribers line for connecting said line to any one of said trunk lines, a connecting relay; for said subscribers line, armatures for said relay normally positioned outside of its stray magnetic field and each individual; toa contactset,1neans individual to each trunk line I for positioning an armature fo to the energization ofsaid relay, and means" forpre-selecting an idle trunk line whereby said last named means is renderedeffective. j

4. In a telephone exchange system, a subscribers line, a group of'trunk lines, multiple contact-sets for connecting said line: to anyone of'said trunk lines, a connecting relay for saidsubscribers line, armatures for said relay each individual to a contact set, means tending normally to position said armatures beyond the-magnetic influence of said relay, means individual to each trunk line for moving an armature to such a position that-upon ener gization of said relay said armature is at-. trac-ted, andmeans. for'pre-selecting an idle trunk li'ne whereby said last named means is rendered effective;

In a telephone exchange system, a 0 group of subscribers"lines; a groupof trunk r response lines, a switching unit for connecting'iany for said subscribers line Y ual to each spouse to the energization of said relay, and means for pre-selecting an idle trunk line of the group whereby said last named means is rendered effective.

6. In a telephone exchange system, a group of subscribers lines, a group of trunk lines, a switching unit for connecting any subscribers line of the group to any trunk line of the group of trunks, said switching unit comprising a connecting relay individual to each subscribers line, each said relay having ture corresponding to each trunk line for controlling the connection of the line to said trunk lines, means individual to each trunk line for o Jerativel I oositionin the armature corresponding thereto for res onse to the energization of said relay, and means for pie-selecting an idle trunk line of the group whereby said last named means is rendered efiective.

'7.- In a telephone exchange system, a group of subscribers lines, a group of trunk lines, a switching unit for connecting any subscribers line of the group to any trunk line of the group'of trunks, said. s itching unit comprising a connecting relay individsubscribefls line, each said relay having an armature normally positioned outside of the stray magnetic field thereof corresponding to each trunk line for response to the energization of said relay,

line for po- I means individual to each trunk sitioning the armature corresponding thereto for response to the energization of said relay, and means for pro-selecting an idle trunk line of the group Whereb said last named means is rendered effective.

8. In a telephone exchange system, a group of subscribers lines, a group of trunk lines, a switching unit for connecting any subscribers line of the group to any trunk line of the group of trunks, said switching unit comprising a frame, connecting relays individual to said subscribers lines superim posed in said frame, each said relay having a normally inoperative armature corresponding to each trunk line for controlling the connection of the line to which it is individual to said trunk lines, and means individual to each trunk line for operatively positioning the armature corresponding thereto of each relay for response whereby upon the energization of one of said relays its operatively positioned armature will become attracted to extend the calling line to the trunk. I

9. In a telephone exchange system, a group of subscribers lines, a group of trunk lines, a switching unit for connecting any subscribers line of the group to any trunk line of the group of trunks, said switching unit comprising a frame,-connecting relays individual to said subscribers lines superimposed in said frame, each said relay hava normally inoperative armaing an armature normally positioned beyond the magnetic influence of said relay and corresponding to each trunk line for controlling the connection of the line to which it is individual to said trunk lines, a trunk rod individual to each trunk line ournaled in said frame and provided with means for moving the armature corresponding thereto of each relay into magnetic proximity to such relay, and a magnet for operating each of said rods.

10. In a telephone exchange system, a group of subscribers lines, a group of trunk lines, a switching unit for connecting any subscribers line of the group to any trunk line of the group of trunks, said switching unit comprising a frame, connecting relays individual to said subscribers lines superimposed in said frame, each said relay having an armature normally positioned beyond the magnetic influence of said rela 7 and corresponding to each trunk line for controlling the connection of the line to which it is individual to said trunk lines, a trunk rod individual to each trunk line journaled in said frame and provided with means for moving the armature corresponding thereto of each relay into magnetic proximity to such relay, a magnet for operating each of said rods, and means for energizing one of said magnets to pro-select a trunk line for use. v

11. In a telephone exchange system, a group of subscribers lines, a group of trunk lines, a switching unit for connecting any subscribers line of the group to any trunk line of the group of trunks, said switching unit comprising a frame, connecting relays individual to said subscribers lines superimposed in said frame,.each said relay having an armature normally positioned beyond the magnetic influence of said relay and corresponding to each trunk line for controlling the connection of the line to which it is individual to said trunk lines, a trunk rod individual to each trunk line journaled in said frame and provided with means for moving the armature corresponding thereto of each relay into magnetic proximity to such relay,a magnet for operating each of said rods, means for energizing one of said magnets to pro-select a trunk line for use, and means for locking said operated rod in its rotated position. i

12. In a telephone-exchange system, a group of subscribers lines, a group of trunk lines, a switching unit for connecting any subscribers line of the group to any trunk line of the group of trunks, said switching unit comprising a frame, connecting relays individual to said subscribers lines superimposed in said frame, each said relay having an armature normally positioned beyond the ma netic. influence of said relay and corresponding to each trunk line for controlling the connection of'the 'li-neto which it is individual to said trunk lines, a trunk rod individual to each trunk line journaled in said frame and provided with means for moving the armature corresponding thereto of each relay into magnetic proximity to' such relay, a magnetfor operating each of said rods, means for energizing one of said magnets to 'pre-select'a trunk linefor use, means for locking said operated-rod in its rotated position, and said rod upon connection of a subscribers line to the pre-selected trunk.

13.1n a'telephone exchange system, a switching unit comprising ity of superimposed relays supported lII'SiilCl frame, a plurality of armatures for each of said relays normally held beyond the magnetic influence of said relay windings, verti- 'ally disposed rods journaled within the frame in alinement with corresponding armatures of each of said relays, cam pins on said rods for engagement with said armatures, and a magnet for-each of said rods for rotating said rods to selectively position the armatures of said relays for attraction.

14:. In a telephone exchange system, a switching unit comprising a frame, a plurality of superimposed relays supported in said frame, a plurality of armatures for each of said relays normally held beyond the magnetic influence of said relay windings, vertically disposed rods journaled within the frame in alin'eme-nt with corresponding armatures of each of said relays, cam pins on said rods for engagement with said armatures, a magnet for each of said rods for rotating said rodsto selectively position the armatures of said relays for attraction, and means for locking each rod in its operated position.

15. In a telephone exchange system, a switching unit comprising a frame, a plurality of superimposed relays supported in said frame, a plurality of armatures for'each of said relays normally magnetic influence of said relay windings,

vertically disposed rods journaled within the frame in alinement with corresponding armatures of each of said relays, cam pins on said rods for engagement with said armatures, a magnet for each of said rods for rotating said rods to selectively position the armatures of said relays for attraction, means for looking each rod in its operated position, and means for unlocking each of said rods.

16. In a telephone exchange system, a subscribers line, a group of trunk lines, multiple contact sets for said subscribers line for connecting said line to any one of said trunk lines, a connecting relay for said subscribers line, operating means individual to said relay for each of said contact sets,

means for unlocking a frame, a pluralgroup of subscribers lines,

' tiple contact sets held beyond the "for each of said trunk means individual to eachtrunltline {for-predetermining one of saidfirs t named means for operation, and means fo-rpreselectingan idle trunk line whereby said'last named means is rendered effective,

17. In a telephone exchange system, a group of subscribers" lines, a group oftrunk lines, switching mechanism comprising multiple contact sets for e'achsubscribers line for connecting such subscribers line toany trunk line of the group of trunk lines,a connecting relay for eachysubscribefs line and operating means individual to said relay for each of said contact sets, a relay individual to each of said trunk lines, and means comprising said last named relays, operative upon connection of a subscribers line to a trunk line for preselecting the'next whereby said trunklines are selected for use in rotation. V p i 18. In a telephone exchange system, a a groupof trunk lines, switching mechanism comprisingmulfor each subscribers line for connecting such subscribers line to "any trunk line of the group of'trunk'linesa connecting relay for each subscribers line and operating means individual to said relay for each of said contact sets, a relay individual to each trunk line and operatiye upon the extension of a subscribers: line thereto, and means comprising the interconnected :contacts of said last named relays for preselecting an idle trunk line for usewhereby said trunk lines are selected in'rotation.

19. In a telephone exchange system, a group of subscribers lines, agroup oftrunk lines, switching mechanism comprisingmuh. tiple contact sets for each subscribers' line for connecting such subscriber s lineto any trunk line of the group of trunk lines, a connecting relay'for each subscribers line;,and

operating means individual toasaidrelay-for each of sa d contact sets,

a relay individual to each trunk line and operative'fupon the extension of a subscribers line "thereto, means for interconnecting the contacts of said last named relays,

lines for predetermining one of said operating means for operation, and means comprising said relays and interconnecting means for operating a selecting magnet corresponding to the next succeeding idle trunk line of the group whereby said trunk lines are selected for use in rotation.

20. In a. telephone exchange system, a group of subscribers lines, a group of trunk lines terminating in a group of firstselector switches, a switching unit comprising multiple contact sets for each subscribers line for connecting such subscribers line to any trunk line of the groupof trunk lines,

a selecting magnet nets operated, means controlled a connecting relay for each subscribers line andoperating means individual to said relay for each of said contact sets, a relay in each of said selector switches adapted to be energized upon the extension of a subscribers line thereto, trunk preselecting magnets in said switching unit corresponding to and controlled by said last named relays respectively predetermining one of said operating means for operation, and means comprising said first named relays, operative upon oonnection of a subscribers line to a preselected trunk line for causing the energization of the trunk preselecting magnet of the next succeeding idle trunk line of the group whereby said trunk lines are selected for use in rotation.

21. In a telephone system, a cross-bar switch comprising a plurality of linemagnets, a plurality of trunk bar magnets, a relay associated with each of said trunk bar magnets, means controlled by said relays for holding a single one of said trunk bar magnets operated, and means controlled by said line magnets for energizing said relay associated with said operated trunk bar magnet.

22. In a telephone system, a cross-bar switch comprising a plurality of line magnets, a plurality of trunk bar magnets, a relay associated with each of said trunk bar magnets, means controlled by said relays for holding one of said trunk bar magnets operated, and means controlled by said energized line magnet and said operated trunk bar magnet for energizing the relay associated with said trunk bar magnet.

23. In a telephone system, a crossbar switch comprising a plurality of line magnets, a plurality of trunk bar magnets, a relay associated with each of said trunk bar magnets, means controlled by said relays for holding a single one of said trunk bar magby said line magnets for energizing said relay associated with said operated trunk bar magnet, and means controlled by said energized relay for releasing said operated trunk bar magnet and operating the next in order of said trunk bar magnets.

24. In a telephone system, a cross-bar switch comprising a plurality of line magnets, a relay associated with each line magnet, a plurality of trunk bar magnets, a relay associated with each of said trunk bar magnets, means controlled by said last relays for holding one of said trunk bar magnets operated, means controlled by said relays associated with said line magnets for energizing said associated line magnet, means controlled by an energized line magnet for energizing said relay associated with said operated trunk bar magnet, and means controlled by said last relays for releasing said associated trunk bar magnet and causing the operation of the next in turn of said trunk bar magnets.

25. In a telephone system, incoming lines, outgoing lines, switching mechanisms for connecting said incoming lines to said outgoing lines, a magnet for each of said incoming lines, an actuating bar for each of said outgoing lines, said bars cooperating with said magnets to operate said switching mechanisms, a relay associated with each of said outgoing lines, and means under the control of each of said relays for preoperating an actuating bar.

26. In a telephone system, incoming lines, outgoing lines, switching mechanisms for connecting said incoming lines to said outgoing lines, a magnet for each of said incoming lines, an actuating bar for each of said outgoing lines, said bars cooperating with said magnets to operate said switching mechanisms, a relay associated with each of said outgoing lines operated upon connection with said outgoing lines, and means under the control of each of said relays for preoperating the next in order of said actuating bars.

In testimony whereof I have ailixed my signature this twenty-seventh day of September, 1919.

PERCY C. SMITH.

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