US1868994A - Telephone system - Google Patents

Description

July 26, 1932. N. H. SAUNDERS TELEPHONE SYSTEM Filed Nov. 25, 1929 3 Sheets-Sheet 1 limb-r Norman H. Saunders July 26, 1932. N. H. SAUNDERS TELEPHONE SYSTEM Filed Nov. 25 1929 3 Sheets-Sheet II -IL n n n n A llikm ELL-3:1 :11" q Nurman H. Saunders N. H. SAUNDERS TELEPHONE SYSTEM .July 26, 1932.

Filed Nov. 25. 1929 3 Sheets-Sheet 3 1m Nurman H.5aunder's Patented July 26, 1932 UNITED STATES PATENT OFFICE NORMAN H. SAUNDERS, OF HOIEWOOD, rumors, ASSIGIIOB,

RATIO}? OF DELAWARE 3'! IESNE MGM mummies SYSTEM Application filed November 25, 1929. Serial No. 409,452.

The present invention relates to telephone systems, but is concerned more particularly with telephone systems employing automatic switching apparatus including automatic selector switches of the step-hy-step type; and the object, generally stated, is the production oi a new and improved selector performing all necessary and standard operations with only four relays instead of the five relays required heretofore.

Applicant is aware that selectors having only four relays have been proposed heretofore, but he believes that prior four-relay selectors have been unsuccessful except in special systems or under special condiable arrangements, whereby the new fourrelay selectors may be added to existing ex changes and will operate with existing fiverelay selectors, requiring only minor changes in the latter selectors. It may be pointed out at this time, by way of explanation, that the standard five-relay selector requires a line relay, are-lease relay, a series relay, a stepping relay, and a switching relay; and that the improved four-relay selector requires all or the relays just named with the exception of the stepping relay. In certain modifications of the invention, no stepping relay is required due to the revised circuit arrangement, while in one modification of the invention the series relays is arranged to be reoperated during the hunting operation of the selector as a stepping relay.

Qther objects and features, having to do for the most part with the carrying-out of the main object hereinbefore stated, will appear upon a further perusal of the specification.

Referring now to the accompanying drawings compr sing Figs. 1 to 7, they show b means of the usual circuit diagrams, a so;

iicientamount of apparatus employed in a. telephone system embodying the features of the invention to enable the invention to be understood.

Figs. 1 and 2, taken together, show Sullic ent switching apparatus to enable connec tion to be set up from substation A of Fig. 1 to substation A2 of Fig. 2; Figs. show modifications of the selector S1 of Fig. 1; and Fig. 7 shows a modification of the master switch MS of F i g. 1.

More in particular, Fig. 1 shows the lineswitch LS, which is one of a plurality of lineswitches controlled by the master switch and having access to a plurality of selectors, one of which is the selector S1. Mechanically, selector S1 is of the usual vertical and rotary type of switch, having its bank contacts arranged in horizontal rows or levels. The selector S1 has access to a plurality of groups of second selectors {ten groups or less), of which the selector 52, Fig. 2, is one. I

The selector S2 may he the same as the selector S1, or it may be modified slightly as will hereinafter appear.

The selector S3 is a standard five-relay selector to which the vertical-oif normal contacts 23:2 and the associated resistance have been added so as to place a battery potential on release trunk conductor 202 when the switch is idle and in normal position.

The connector C may be any suitable twowire connector which places ground on the associated release-trunk conductor while in use.

Detailed description} call from A1 to substation A In order to explain the operation of the selector S1 and the way in which it cooperates with the associated apparatus, it be assumed that the subscriber at substation A1 desires to converse with a subscriber It substation lVhen the receiver is removed at substw tion A1, a circuit is closed across line conduct-01's 101 and 103 for line relay 105 the contacts of the brid cut-01E armature 106 of the lineswitch L Belay 105 operates and disconnects the axe-called rivetenormal conductor 104 from the bri ge-eut ofl. winding (the upper winding) of the lineswitch magnet 120 and connects it to ground instead, thereby guarding the calling line against seizure by the connectors having access to it. At its lower armature, relay 105 closes a circuit for the-lower winding (the pull-down winding) of the magnet 120 over the associated chain conductor 140, at the same time opening the chain as regards the succeeding lineswitches. It will be noted that und potential is supplied the chain conuctor 140 throu h contacts in the master switch MS and t rough the lower winding of the delay relay 154. By way of explanation, it may be pointed out that the delay relay 154 is included in the circuit so as to delay the operation of a lineswitch for a slight interval following the operation of the line relay so as to give a releasing lineswitch time for the plunger to realign before the lineswitch reoperates, in case it is reoperating immediately following its release. The current-flow through the pulldown winding over the chain circuit is not suflicient to operate either of the armatures of magnet 120 as long as the lower winding of the dela relay is in circuit alone. The upper win ing of the delay relay, it will be noted, is normally short-circuited through the contacts of the relay, makin the relay slow to operate on account of t e fact its short-circuited winding is on the armature end of the relay. When relay 154 operates, it removes the short circuit from around the upperewinding and connects the low-resistance upper winding in parallel with the high resistance lower wmding, allowing suflicient current to flow over the chain conductor 140 to operate both armatures of the lineswitch magnet 120. The bridge-cut-ofi armature 106 operates the associated contacts to disconnect ground and line relay 105 from the conductors of the calling line, and the plunger armature 107 operates the bank springs 109113 and also closes the con- 'tacts 108. The closing of contacts 108 reconnects the upper winding of magnet 120 to the grounded conductor 104.

When the contact springs 109--113 are pressed into engagement withtheir respective associated contacts, and the connection is thereby extended to the selector S1, the ground potential maintained on conductor 104 by the slow-acting line relay 105 is trans- 'mitted to release-trunk conductor 115 and. thence over the branch conductor 163 to the master switch MS,- causing the master switch to reselect another idle trunk in the manner to he described hereinafter.

In the selector S1, line relay 121, which. is connected to the conductors 114 and 116 through contacts of relay 124, now energizes over the calling line, upon operating, relay aseae' 121,. at the normally closed contacts corrtrolied b its upper armature, removes the normal s unt from around the winding of release relay 122., at the same time closing a circuit for relay 122 in series with vertical magnet 126. The circuit of relay 122 at this time includes the lower contact of verticaloff-normal spring 128 and the said spring. Upon operating, relay 122 locks itself to ground independent of spring 128 at its inner-lower armature. In a switch-control circuit of this type, the inner-lower armature of relay 122, together with the lower contact of spring 128, is ordinarily omitted and ground potential is connected directly to the lower terminal of the relay. The present arrangement is used so as to prevent relay 122 from operating in case the selector S1 is seized b a lineswitch before it reaches its norm position. It sometimes happens that a selector becomes stuck mechanically and does not restore. Due to the way in which the master switch MS tests, it will stop on a selector that is not in its normal position provided there is no ground potential on the release-trunk conductor thereof, such as conductor 115, and this selector in oil-normal condition is seized by lineswitch such as LS. When this happens, however, relay 122 does not operate, ow' to the fact that its circuit is not complete at contact spring 128, and the lineswitch LS releases for the want of holding potential on conductor 115, and seizes the newly selected idle trunk, the master switch having operated in the meantime. As a further result of its operation, release relay 122, at its lower armature, opens a point in the circuit of release magnet 127 and closes a point in the circuit of rotary magnet 129, and at its inner-upper armature it removes the shunt from around the lower windin of relay 123 and applies ground potential to release-trunk conductor 115 so as to maintain the lineswitch LS operated through the upper winding of magnet 120 after relay 105 has fallen back. It may be pointed out that current flows through the upper winding of relay 123 from the grounded conductor 115 prior to the operation of relay 122 but relay 123 does not operate at this time because the lower winding is shortcircuited, and because the upper winding is a non-inductive winding. When the short circuit is removed from the lower windin however, relay 123 operates from the groun ed conductor 115, its two windin s being connected-in series at the vertical-o -normal I contacts 132. Upon operating, relay 123 locks itself operated at its inner-lower armature independent of contacts 132, and at its lower armature it opens a point in the circuit of rotary magnet 129. At its upper armature, relay 123. shunts the upper armature and cooperating contact of the line relay 121 so as to prepare an operating circuit for the vertical magnet 126.

It will be noted that a connection normally exists between the lower talking conductor 116 of the selector and the dial-tone transformer 117, through the contacts associated with the over-flow spring 125, and the lower winding of relay 121. On account of this connection, the tone roduced by the dial-tone current is heard by the calling subscriber, and

he is" thereby informed that he may now dial the digits of the desired number.

around the winding of relay 122. By the operation of vertical magnet 126, the wipers 133--135 of the selector S1 operate step-bystep untilthey arrive opposite the desired level of bank contacts. Relay 121 remains operated while it is momentarily short circuited, because of circulating current in its winding.

Each time line relay 121 energizes following its first deenergization, ground potential is applied to the junction of the windings of relay 123 by way of oil-normal spring 128 and its upper contact, contacts of relay 124,

lower armature, operated, of relay 122, lower armature of relay 121, and over-flow spring 131-. Relay 123 does not fall back when the lower winding is intermittently shunted during the vertical 0 eration of the switch, because of the circu ating current in the shortcircuited lower winding. When the line relay comes to rest, however,:at the end-of the vertical movement, the lower winding of relay- 123 remains short-circuited, and the relay falls back; At its lower armature, relay 123 completes the circuit of the rotary magnet 129 through the otf-normal contacts 130 and the self-interrupting contacts of magnet 129. The rotary circuit includes the lower armature operated, of release relay 122, contacts of relay 124, and off-normal spring 128 and its upper contact. v

By the buzzer-like operation of magnet 129, the wipers 133135 are driven over the contacts in the level selected by the vertical 'movement.

When an idle contact set is reached (for example the contact set from which the con-' ductors 136-138 extend to the selectorS2),'

a battery potential is encountered on the test contact thereof by wiper 134, the conductor 137 of S2 being connected to battery through a path corresponding to the one through which the conductor 115 of S1 is norma y connected to battery, including the innerupper armature, normal, of relay 122, vertical-ofi-normal contacts 132, and the non-inductive upper winding of relay 123. The selector S2 is assumed to be similar to the selector S1 except that ground potential is connected directly to the lower winding of the relay therein corresponding to relay 122 instead of through an oil-normal contact. This obviates the use of the inner-lower armature of the relay.

When this battery potential is encountered by test wiper 134, the switching relay 124, whose upper winding is connected between the now grounded conductor 115 and test wiper 134 through the upper contacts of re lay 122, energizes over wiper 134 and conductor 137. Upon energizing, relay 124 at its middle lower armature opens the circuit of the rotary magnet and a point in the circuit of release magnet 127 at its inner-lower armature it closes a locking circuit for its lower windin in series with the upper winding from con uctor 115; at its inner-upper armature it extends conductor 115 through to wiper 134, short-circuiting the upper winding for the time being; and at its upper and lower armatures it disconnects the incoming conductors 114 and 116 from the windings of line relay 121 and extends them through the wipers 133 and 135 and conductors 136 and 138 to the selector S2, whereupon the relays therein corresponding to ' relays 121, 122, and 123 of the selector S1 energizes to prepare the switch for operation and to place a ground otential on conductor 137 so as to maintain the selector S1 and the lineswitch LS operated. p

In the selector S1, line relay 121 falls back when it is disconnected at the upper and lower contacts of relay 124 and it again shortcircuits relay 122. The vertical magnet 126 does not respond at this time owing to the *fact that relay 123 is at normal. Responsive to being short-circuited, relay 122 falls back and removes the local ground connection from conductor 115 at its inner-upper a'rma ture, leaving this conductor grounded only by way of wiper 134 and conductor 137; and at its upper armature it removes the short circuit from around the upper winding of.

relay 124 so as to decrease the holding cur rent of the relay and so as to avoid a slowed release of relay 124 when its circuit is opened by the removal of ground potential from the release-trunk conductor of the established connection.

When the second digit is dialled, the selector S2 operates in a manner similar to that described hereinbefore in connection with the selector S1, and raises its wipers opposite the desired level of bank contacts and: selects an lac idle trunk, which trunk will be assumed to be the one comprising conductors 201203 and extending to the selector S3.

When this idle trunk is selected, the switching relay (not shown) of the selector S2 operates over conductor 202 and through the vertical-ofi-normal contacts 232 and the associated resistance. Line relay 221 operates over the calling line and over conductors 201 and 203 and closes a circuit for the slow-acting release relay 222. Relay 222 operates and prepares the vertical-magnet circuit at its lower armature, and places ground potential on the release-trunk conductor 202 at its upper armature.

When the third digit is dialled, line relay 221 falls back each time its circuit is opened at the calling substation. Each time it falls back, line relay 221 opens the circuit of the slow-acting relay 222 and closes a circuit through the lower armature, operated, of relay 222 and series relay 223 for vertical magnet 226. By the operation of vertical magnet 226, the wipers 333335 are raised opposite the desired level of bank contacts. Series relay 203 operates upon the first impulse of current transmitted to the vertical magnet and it remains operated throughout the vertical movement. Upon operating, relay 223 prepares a circuit for stepping relay 275, which is closed at the vertical off-normal contacts 230, through the interrupter contacts of magnet 245, as soonas the switch moves from its normal position. When relay 275 operates, it prepares a circuit for rotary magnet 229 at its lower armature, and at its upper armature it closes a locking circuit for itself independent of the contacts of relay 223.

When relay 223 falls back at the end of the vertical movement, it completes the rotarymagnet circuit through the lower contacts of relay 275. When rotary magnet 229 operates it advances the wipers into engagement with the first set of bank contacts in the selected level. and, at the end of its stroke, it opens the circuit of relay275. Relay 275 thereupon falls back and opens the magnet circuit and a further point in its own locking circuit. The rotary magnet falls back when this happens, and again connects up the stepping relay. If the first trunk line is busy, the ste ping relay operates again and the buzzer-1i e action continues untll an idle trunk line is reached, an idle trunk line being characterzed in this case by the absence of ground potential. \Vhen an idle trunk line is reached, the trunk line extending to connector C, for example, relay 275 does not reoperate as no further ground potential is encountered; and relay 224, which has been short-oi rcuited heretofore by the ground potential on test wiper 234, energizes from the grounded releasetrunk conductor 202 in series with relay 275 by way of contacts 231, and 230, and the contacts of rotary magnet 229. Relay 275 does not operate in series with relay 224, owing to the relatively-high resistance of relay 224. Upon operating, relay 224 opens the circuit of release relay 222 and a point in thevertical-magnet and release-magnet circuits at its inner-lower armature; opens a point in the test circuit and connects wiper 234 with the incoming release-trunk conductor 202 at its inner-upper armature; and at its upper and lower armatitres switches the connection through from conductors 210 and 203 to the corresponding conductors of the connector by way of wipers 233 and 235.

The connector C is now prepared for operation in the well-known manner, and ground potential is placed on the release-trunk conductor thereof so as to maintain the established connection.

In the selector S3, line relay 221 falls back responsive to being disconnected, and relay 222 falls back also due to its circuit being opened first at the inner-lower contacts of relay 224, and later at the contacts of relay 221.

\Vhen the remaining two digits in the numher are dialled, the connector G operates in the usual manner to select the level in which the called line terminates and to select the contact set of the called line in the selected level. After a line has been selected, and as manner when the called subscriber responds.

lVhen the subscriber at substations Al and A2 have both replaced/their receivers following the ensuin conversation, ground otential is remove from the release-trun conductor of the established connection by the connector C, whereu on the switching relays of the selectors S1, 2, and S3 fall back, and the magnet 120 of lineswitch LS deenergizes and permits the armatures 106 and 107 to restore. When switching relay 124 of the selector S1 falls back, it completes a circuit for release magnet 127 at its middle-lower armature through the vertical-ofi-normal spring 128, and the lower armature of relay 122. Responsive to the energization of release magnet 127, the selector S1 is restored to its normal position, and the circuit of the release magnet is opened at off-normal spring 128. Off-normal spring 128 also prepares a circuit for operating relay 122 when the selector is again seized, and off-normal contacts 132 place a battery potential on conductor 115 by way of the inner-upper armature of relay 122, so as to characterize the selector Sl as idle.

l/Vhen switching relay 224, of the selector S3 falls back, it closes a circuit at its innerlower contacts for release n'iagnet 227 by way release magnet circuit is opened at oil-normal contacts 228. Oil-normal contacts 232 reapply battery potential through the associated resistance to release-trunk conductor 202 to characterize the selector as idle. The

selector S2 is released in the same manner as the selector S1.

The entire connection is now released andthe apparatus involved therein is in readi- Overflow at the selector 8'1 bank contacts, the overflow springs 125 and th 131 are operated. Overflow spring 125 substitutes busy-tone current from the busytone transformer 118 for the dial-tone current through the dial-tone transformer 117, and overflow spring 131 opens the ground connection to the lower terminal of the upper winding of relay 123 and again connects the two windings of the relay in series, whereupon relay 123 reoperates from the releasetrunk conductor 115, grounded atthe innerupper armature of relay 122, and opens the circuit of the rotary magnet 129 at its lower armature so as to stop further rotation of the switch.

When the calling subscriber pauses in his dialling to listen in, he hears the busy-tone fi'om the busy-tone transformer 118 and replaces his receiver. When this occurs, line relay 121 falls back and shunts release relay 122. Incidentally, magnet 126 is operated momentarily. Relay 122 falls back and removes the ground potential from release trunk conductor 115 at its upper armature and again shunts the lower of relay 122. Relay 122 also falls back opening the circuit of magnet 126. The circuit of release magnet 127, as hereinbefore traced, is closed at the lower armature of relay 122 and the switch restores to normal position. The line switch LS releases in the usual manner when the ground potential is removed from. condoctor 115.

Overflow at the selector .83

When the calling subscriber replaces his re ceiver, the selector releases responsive to the deenergization of relay 222.

The selector of Fig. 3

Fig. 3 shows how a fonrrelay selector slow-acting relays, of the type having co per collars placed on the lower end thereo may be made to operate do the line of the four-relay selector S1 of Ijlg. 1.

The various parts in Fig. 3 corresponding to Similar parts in Fig. 1 have been given the same reference characters except that the three-hundred series is employed in F' 3 instead of the one-hundred series as in ig. 1. In Fig. 3, it will be noted that relay 321 is the line relay; relay 322 is the release relay; relay 323 is the series relay; and relay 324; is the switching relay. It will be observed that a battery potential is normally connected to the incoming release-trunk conductor 315 hrough the upper armature, normal, of relay 322, vertical-oif-normal contacts 332 and e associated resistance.

When relay 321 operates responsive to a seizure of the switc it closes a circuit through the inner-lower armature of relay 325 for release relay 322 by way of the vertical oil-normal contacts 328'. Relay 322 thereupon operates and shunts the vertical-ofi-normal contacts 328' at its inner-lower armature;

it prepares the vertical-magnet circuit at its middle-lower armature; and it prepares the rotary-magnet circuit at its lower armature. At its inner-upper armature, relay 322 disconnects the battery potential from conductor 315 and substitutes a direct ground potential; and at its upper armature it prepares a circuit for the test winding of relay 325.

The vertical magnet 326 and the series relay 323 are operated in the manner described in connection with the selector S3 when the digit is dialled to operate the selector of Fig. 3.

When relay 323 falls back at the end of the vertical movement, it completes the rotarymagnet circuit the circuit having been prepared at the vertical-oif-normal contacts 328 through the lower armature, operated, of relay 322. The rotary magnet is a self-interrupting magnet and it drives the Wi ers 333-335 across the contact bank in searcli of an idle trunk. When an idle trunk is reached, the upper winding of relay 324 is energized the same way as the upper winding of relay 124; of selector S1 from battery potential encountered on the release-trunk condoctor of the trunk with which the wipers are in contact. It will be noted that the contacts of relay 324 correspond in function exactly to contacts of relay 124, except in the case of the middle-lower contacts of relay 324. At these contacts, the rotarymagnet circuit is opened as well as the circuit of release relay 322. When the line and release relays 321 and 322 have fallen back, the release-magnet circuit is maintained open at the middle-lowercontacts of relay 324;.

When the ground potential is removed from the release trunk conductor of the succeeding switch, relay 324 falls back and closes the release-magnet circuit at its innerpermittin the lower contacts through off-normal contacts 328 and the lower armature of relay 322.

In case the selector of Fi 3 is unable to find an idle trunk, the over ow springs 325 and 331 operate. The overflow spring 225 may perform the operation of overflow sprin 125, Fig. 1, to substitute busy potential or dial-tone potential, or it may merely substitute busy potential for ground potential. The overflow spring 331 closesa circuit for relay 323 and magnet 326 in series with the associated resistance. The currentflow through this resistance is suflicient to operate relay 323, but it need not be sufficient to operate magnet 326. Relay 323 opens the circuit of the rotar magnet 329 to prevent further operation the rotary magnet.

The selectorof Fig.

Fig. 4 shows a four relay selector somewhat similar to the selector of Fig. 3, the main difi'erence being that relays without copper collars are used in Fig. 4, and the slow action of the relays during dialling is obtained by circulatin current to flow through main win ings rather than by circulating current flowing copper collars. It will be noted that battery potential is normally present on release-trunk conductor 415 through contacts 432 and the associated resistance, the selector being in this respect similar to the selector S3, Fig. 2.

When line relay 421 operates over conductors 414 and 416 responsive to a seizure of the switch, it closes a circuit for relay 422 in series with vertical magnet 426through the vertical-ofi-normal contacts 428"; Relay 422 operates and locks itself at its inner lower armature independent of contacts 428,

this operation being similar to the operation performed by the lower armature of relay 322. At its middle-lower armature, relay 422 prepares a circuit for vertical magnet 426, and at its lower armature, it opens a point of the circuit of the release magnet and prepares a circuit for the rotary magnet. At its upper armature, relay 422 places ground on conductor 415 to maintain the preceding part of the connection established, and at its inner-upper armature it prepares the test circuit of the uiper winding of relay 424.

When the first igit is dialled subsequent to the seizure of the selector of Fig. 4, line relay 421 falls back one or more times. Each time it does so, it short-circuits relay 422, closing a circuit for vertical magnet 426 by way of the middle lower armature of relay 422 and contacts of relay 424. Relay 423 0 rates in parallel with vertical magnet 426 t rough rotary-ofi-normal contacts 481 when the first impulse of current is delivered to magnet 426, and it remains operated throughout the vertical movement due to the fact that it is in series with relay 422 and in parallel with magnet 426.

At the end of the vertical movement, relay 423 falls back and closes a circuit for rotary magnet 429 through the lower armature of relay 422, contacts of relay 424, and vertical ofi-normal contacts 428. Upon operating, rotary magnet 429 advances the wipers 433- 435 into engagement with the first set of bank contacts in the level opposite which they have been raised. When the switch moves off-normal in a rotary direction, the rotary-ofi-normal contacts 481 disconnect relay 423 from in parallel with magnet 426. Near the end of its. stroke, magnet 429 closes a circuit for relay 423, and relay 423 operates and opens the circuit of the rotary magnet 429. Magnet 429 thereupon falls back and opens the circuit of relay 423, whereupon relay 423 falls back and again closes the circuit of the magnet. In case the trunk line terminating in the first set of bank contacts is idle, relay 424 operates and opens the circuit of the rotary magnet before the rotary magnet again operates. If this set of contacts is busy, relay 424 does not operate and the rotary movement continues.

When an idle trunk line is reached. the upper winding of relay 424 is energized from the grounded conductor 415 through the inner-upper contacts of relay 422 to battery by way of test wiper 434 and the releasetrunk conductor of a succeeding switch. Upon operating, relay 424 opens the rotary-magnet circuit at a pair of its lower contacts; it looks itself to the grounded release-trunk conductor 415 at its inner-lower armature through the inner-lower contacts of relay 422; and at its inner-upper armature it extends the grounded release-trunk conductor 415 to the wiper 434. Other results of the energization of relay 424 are that a point in the vertical-magnet operating circuit is opened at one of the lower armatures of the relay, and the conductors 414 and 416 are extended through the wipers 433 and 435 to the forresponding conductors of the seized trunk When relay 422 falls back responsive to being short-circuited when line relay 421 falls back after having been cut oil at the contacts of relay 424, it removes the shortcircuit from around the upper winding of relay 424, leaving the two windings of relay 424 energized in series from the now grounded wiper 434.

When ground potential is removed from the release-trunk conductor of the established connection, and relay 424 falls back, a circuit is closed through the vertical-oif-normal contacts 448, contacts of relay 424, and the lower contacts of relay 422, for release magnet 427. By the operation of the release magnet the selector is restored to normal position, and the release-magnet circuit is opened at contacts 428.

In case the selector of Fig. 4 is unable to find an idle trunk, the usual circuit change is made by the overflow spring 425, and the overflow spring 431 closes a circuit for relay 423 to open the rotary-magnet circuit.

The selector of Fig. 5

Fig. 5 shows a selector which corresponds more closely to the selector of Fig. 1 than does the selector of Fig. 4, in that the rotary magnet 529 directly interrupts its own circuit instead of operating the series relay to interrupt its circuit, as is done in the case of magnet 429 and relay 423. The operation of the selector of Fig. 5 is the same as the operation of the selector of Fig. 4 until relay 523 falls back at the end of the vertical movement. In this case, as before, the circuit of the rotary magnet is closed, but in this case the rotary magnet 529 directly interrupts its own circuit, and relay 523 remains connected in multiple with vertical magnet 526.

When an idle trunk is reached, relay 524 is energized by means of its upper winding, being connected between release-trunk conductor 516 and test wiper 534 through its own contacts. At its inner-lower contacts. relay 524 locks its lower winding in series with the upper winding to the release-trunk conductor, and at its inner-upper armature it connects the release-trunk conductor to the test wiper, and removes the shunt from around its own upper winding. At its other lower contacts, relay 524 opens a point in the vertical-magnet operating circuit and it stops the rotary movement by opening a point in the rotary-maenet circuit. The releasing operation is the same as described in connection with Fig. 4.

In case the selector of Fig. 5 is unable to find an idle trunk, overflow springs 525 and 531 are operated. Spring 531 disconnects relay 523 from in multiple with vertical magnet 526. and connects it to ground, operating relay 523 to open the rotary-magnet circuit.

The selector of Fig. 6

cuit at its inner-upper contacts; grounds the release-trunk conductor atits upper contacts; and at its lower armature opens a point in the release-magnet circuit and prepares the rotary-magnet circuit and the verticaLmagnet circuit.

When the digit is dialled to operate the selector, line relay 621 falls back one or more times. Each time it does so, it short-circuits relay 622, thereby closing a circuit for vertical magnet 626 through the lower armature of relay 622 and the middle-lower armature of relay 624. Relay 623 operates in multiple with the vertical magnet as in the case of relays 523 and 423.

When relay 623 falls back at the'end of the vertical movement, it closes acircuit for totary magnet 629 through the verticalofl.-normal contacts 630 and the self-interrupting contacts of the magnet. This circuit includes the middle lower armature of relay 624 and the lower armature operated of relay 622. The rotary movement continues until an idle trunk line is found, whereupon relay 624 opcrates through wiper 634 and opens the rotary-magnet circuit at its middle lower armature. The rotary movement is unable to continue through the resistance associated with the armature of relay 621. Relay 624 also closes a locking circuit for itself and connects the release-trunk conductor 615 through to wiper 634, in addition to extending the incoming conductors 614 to 616 to the wipers 633 and 635.

When relay 621 falls back and shortcircuits relay 622, responsive to being disconnected by relay 624, vertical magnet 626 and relay 623 do not again operate owing to the fact that the vertical-magnet operating circuit is opened at the middle-lower armature of relay 624 at the same time that the rotary-magnet operating circuit is opened.

in case the selector of Fig. 6 is unable to find an idle trunk. overflow springs 625 and 631 operate, and the spring 631 performs the same operation as described before in connection with overflow spring 531.

When relay 624 falls back responsive to the removal of the ground potential from the release-trunk conductor of the established connection. the release-magnet circuit is completed at its middle-lower armature of relay 624 through the lower armature of relay 622- and off-normal contacts 628. The releasemagnet circuit is opened at off-normal contacts 628 when the switch restores to normal.

Master-switch operation Referring now to Fig. 1, the operation of the master switch MS will now be explained. The power for operating the master switch is supplied by the solenoid 156, which upon ing on the contact associated with the tenth trunk, leading to the selector S1, Fig. 1.

\Vhen the selector S1 is taken for use in the manner described hereinbefore, a branch circuit is closed over conductor 163 and through test wiper 162 for start relay 155. Start relay 155 operates and removes ground from the operating chain conductor 140, and at the same time closes a circuit for locking magnet 152. Locking magnet 152 operates and unlocks the master-switch segment 161, at the same time closing a circuit for the openchain relay 153. The open-chain relay 153 operates and opens a further point in chain conductor 140, at the same time short-circuiting its upper winding so as to render the relay slow to release. The master switch is propelled in a clockwise direction by the U spring 161, until start relay 155 falls back upon an idle trunk being encountered. When this occurs, the circuit of the locking magnet is opened and the rotation of the master switch is stopped. The open-chain relay falls back a moment later.

When the trunk selecting operation has taken place until the test wiper 162 reaches the contact associated with trunk one, the master-switch finger 157 closes the contact spring 159, preparing a circuit for trip relay 151. The next time start relay 155 operates, trip relay 151 is operated in parallel with the locking magnet 152 through contacts 159. Upon operating, the trip relay 151 operates the associated latch, locking its contact assembly under the control of spring 160. At the outer contacts of trip relay 151, an additional circuit for the locking magnet 152 is closed, and at the inner contacts of relay 151 a circuit is closed for the solenoid 156. When the solenoid operates, the master switch is moved in a clockwise direction to the position shown in drawings. The contacts 159 open the circuit of the trip relay 151 as soon as the movement starts. The contacts of relay 151, however, remain'locked under. the control of spring 160, until spring 160 is moved by finger 158 of the master switch, when the master switch arrives in the position shown in the drawings. When this occurs, the circuit of solenoid 156 is opened and the alternative circuit of the locking magnet 152 is opened at the outer contacts of the trip relay.

Referring now to Fig. 7, the operation of the master switch MSl will be explained. The master switch is the same as the master switch MS of Fig. 1, except that the lower terminal of start relay 155 is connected to ground instead of to battery, as in the case of relay 155, and the front and back contacts of the armature of relay 155 are reversed with respect to the contacts of relay 155. Start relay 155' is normally energized through the test wiper, corresponding to wiper 162, Fig. 1, and over a circuit extending to battery by way of a branch conductor,

such as 163 and the release-trunk conductor such as 115, battery being normally supplied to conductor 115, as above pointed out, through the upper winding of relay 123.

When the trunk line upon which the master switch MS is standing is taken for use, the battery potential thereon is replaced by ground potential, resulting in the deenergization of relay 155'.

When relay 155 falls back, it removes ground from the operating chain conductor, corresponding to conductor 140, Fig. 1, at the same time closing a circuit for the associated locking magnet, corresponding to magnet 152, Fig. 1. This causes the master switch to operate as described in connection with master switch MS, Fig. 1.

When the test wiper of the master switch MS encounters a test contact on which there is a battery potential, relay 155 again operates and stops the operation of the master switch, and replaces ground potential on the associated chain conductor through the delay relay 154.

What is claimed is:

1. In a switch-control circuit for use in automatic switching apparatus, a line relay, a release relay, and a change-over-relay, and means for energizing said relays successively in the order named responsive to the seizure of the switch control circuit.

2. In a switch-control circuit for use in automatic switching apparatus, a line relay operated responsive to a seizure of the control circuit, a release relay operated responsive to the operation of the line relay, and a change-over relay operated responsive to the operation of the release relay.

3. In a switch-control circuit for use in automatic switching apparatus, a line relay operated responsive to a seizure of the control circuit, a release relay operated responsive to the operation of the line relay, a change-over relay operated responsive to the operation of the release relay, an operating magnet, and a circuit for said magnet including contacts of the line relay closed when the line relay is restored and contacts of the change-over relay closed when the changeover relay is operated.

4. In a switch-control circuit for use in automatic switching apparatus, a line relay operated responsive to a seizure of the control circuit, a release relay operated responsive to the operation of the line rleay, a change-over relay operated responsive to the operation of the release relay, a first and a second operating magnet, a circuit for the first operating magnet including back contacts of the line relay and front contacts of the control relay, and a circuit for the second operating magnet including said front contacts of the line relay and including back contacts of the control relay.

5. In a system employing automatic switching devices, a selecting device having a normal ositionand being accessible to a pinralit 0 other selecting devices, said selecting evice having a test conductor and having an operating magnet arranged to move the selecting device to a desired oil-normal position, a control relay in said selecting device arranged to control the operating circuit of said operating magnet, means including a pair of off-normal contacts of said device and a resistance element for connecting a characteristic potential to said test conductor when the said switch is idle and in its normal position, so as to characterize the selecting device as idle to the selecting devices having access to it, and a circuit for said control relay including said elf-normal contacts and said resistance element.

6. In a switch-control circuit, a release relay, an operating magnet, a line relay and means for operating it to close a circuit for said operating magnet and said release relay in series, a control relay and circuit connections for operating it, contacts on the control relay for closing a circuit for the said operating magnet and said release relay in series independent of the contacts of the line relay,

and other contacts on the line relay for shunting the release relay to operate the operating magnet through the control-relay contacts.

7. In an automatic selector switch having a primary or group-selecting movement and a secondary or contact-selecting movement, a primary operating magnet and means for controlling it to bring about the group-selecting operation of the selector, a secondary operating magnet and means for operating it automatically following the termination of the operation of the primary magnet to effect the contact-selecting operation, said switch having a test wiper, a test relay in said selector connected between one pole of a source of current and said test wiper, means responsive to an operation of said test relay when said test wiper encounters the other pole of said source of current to stop the contact-selecting movement and to connect the said other pole of the current source to the test wiper, means including a second winding on said test relay for maintaining it operated thereafter, and means including another relay for opening the circuit of the test winding responsive to the operation of said test relay.

8. In an automatic selecting system wherein the'selecting devices are operated in serial relationship to set up desired connection, a test conductor in a selecting device over which preceding selecting devices are arranged to test for idle-indicating potential, a release relay in said selecting device, a connection for supply idle-indicating potential to said test conductor through back contacts on said release relay and through normallyclosed ofi-normal contacts, circuit connections for operating said release relay upon the seizure ofthe switch, said release relay being efiective when operated to substitute a holding potential for said idle-indicating potential so as to hold the preceding selecting devices in operated position.

9. In a system wherein automatic selectmg devices are operated in tandem to set up desired connections, a selecting device in said system accessible to a plurahty of selecting devices and having access to another plurality of selecting devices, means for permitting one of the selecting devices having access to said selecting device to make connection therewith only in case there is a predetermined potential on the test conductor of said selecting device and for permitting said selecting device to make connection with a succeeding selecting device only in case said predetermined potential is present on the test conductor of such succeeding selecting device, and means in said selecting device and in each of said succeeding selecting devices responsive to the extension of a connection thereto for substituting a holding potential for said predetermined potential.

10. In a two-motion automatic switch, a release relay, two switch-operating magnets arranged to operate the switch in its primary movement and in its secondary movement, respectively, a control relay connected in shunt of the primary magnet, circuit connections for supplying operating current to said release relay through the primary magnet and the said control relay, primary-oil-normal contacts operated when the switch is moved from its normal position by the primary magnet, the relation between the primary magnet and the release and control relays being such that the release relay remains operated and the control relay operates and remains operated while the primary magnet is being operated, a circuit for the secondary magnet closed by said control relay through said off-normal contacts when it falls back at the end of the primary movement, and a circuit controlled by the secondary magnet for reoperating said control relay to interrupt the circuit of the secondary magnet.

11. In a two-motion automatic switch having a directed primary movement and an automatic secondary movement, a control relay in said switch, means for maintaining said control relay operated during the primary movement and for deenergizing it to start the secondary movement, and means for operating said relay in a buzzer-like manner during the secondary movement to control such movement.

12. In an automatic selector switch having a directed primary movement and an automatic secondary movement controlled by primary and secondary magnets, respectively, means for transmitting directed impulses to the primary magnet to effect the rimary movement, a control relay energized t roughout the primary movement and automaticall deenergized at the end thereof, a circuit fbr the secondary magnet including contacts on said control relay closed when 1t deenergizes, and contacts on said secondary magnet for reoperating the control relay to open the circuit of the secondary magnet each time the control rela reoperates.

13. In a switc -control circuit, a line relay, a release relay, a primary operating magnet, and a secondary operating magnet, means for operating the line relay to close a first circuit for the release relay and the primary operating magnet in series, contacts on the release relay for closing a second circuit for the primary operating magnet and the release rela in series, other contacts on the line relay, 0 osed each time the line relay falls back, to shunt the release relay and operate the primary magnet in the said second circuit, means for closing a circuit for the secondary o erating magnet after the primary magnet as been operated, the circuit for the secondary operating magnet includin a portion of the said second circuit, a switc ing relay and means for operating it to open the said second circuit, and a resistanoe element included in the said first circuit to prevent the secondary operating magnet from operating through the said first circuit.

14. In an automatic switch having a directed primary movement and an automatic secondary movement, a relay operated during the primary movement and deenergized at the end thereof to start the secondary movement, means for terminating the secondary movement, and additional means for reoperating the said relay to terminate the secondary movement in case the first means does not operate.

15. In a selector switch having a directed primary movement and an automatic secondary movement, primary and secondary ma ets for operating said switch in its two sai movements, a control relay operated in shunt of the primary magnet and maintained operated during the primary movement, circuit connections for initiating the secondary movement when the said control relay falls back at the end of the primary movement, and means including overflow contacts for disconnecting the said control relay from the primary magnet circuit and for operating it in a separate circuit to stop the secondary movement in case the secondary movement continues beyond a predetermined position.

16. In an automat1c switch having a primary movement and a secondary movement effected by primary and second magnets, re-

spectively, a control relay in said'switch ar-' ran d to be operated in a control circuit wh' e theprimary magnet is being operated to bring about the primary movement of the switch, means eflective upon the termination of the primary movement fpr starting the secondary magnet into operation to bring about the secondary movement, means operated responsive to the beginning of the secondar movement for removing said control relay om the said circuit, and means for operating said control relay in conjunction with the secondary magnet to exercise acontrol over the secondary magnet during the secondary movement.

17. In a two-motion automatic switch having a control relay, means for maintaining said control relay operated during the primary movement and for restoring it to start the secondary movement, and means eflective responsive to said switch being driven beyond a predetermined point in its secondary movement for reoperating said control relay to terminate the secondary movement.

18. In an automatic selector switch, a release relay and a changeover relay connected in circuit with each other, means for maintaining said changeover relay 0 erated during the primary movement an for deenergizing it to start the secondary movement, secondary off-normal contacts for removing said changeover relay from in circuit with said release relay, and overflow contacts for reoperating said control relay to terminate the secondary movement in case the switch is advanced to overflow position.

19. In a two-motion automatic switch having a primary movement and an automatic secondary movement, a primary magnet and a secondary magnet for bringing about said movements, a slow-acting control relay connected in circuit with said primary magnet and arranged to be operated during the primary movement and to be deenergized at the end of the primary movement to start the secondary movement, overflow contacts arranged to operate responsive to said switch being driven to overflow position during the secondary movement to close a circuit for said primary magnet and control relay, and a resistance element connected in said circuit to limit the current flow to such a value that the primary magnet is not reoperated, while the control relay is reoperated to terminate the secondary movement.

20. In a selector switch having a primary movement anda secondary movement, a primary and secondary operating magnets, a release magnet for restoring said switch to its normal position after it has been operated by its primary and secondary ma ets, a pair of relay contacts, and means or opening said contacts after said switch has been operated in its primary and secondary movements to open a point in the circuit of each of said magnets.

21. In an automatic switch having a primary movement and a secondary movement eifected by a primary magnet and a secondary magnet, respectively, a release magnet arranged to restore said switch to normal position after it has been operated by said primary and secondary magnets, a relay and means for operating it after the switch has been positioned by the primary and secondary magnets, a contact pair on said relay for opening a point in the circuit of two of said magnets, and another contact pair on said relay for opening a point in the circuit of the third magnet.

22. In a switch control circuit for use in automatic switching apparatus, a line relay, a release relay, a changeover relay, means for closing a circuit for said changeover relay upon the seizure of the control circuit, a shunt path around said changeover relay preventmg its energization, means for energizing said line and release relays responsive to the seizure of the control circuit, and means for opening said shunt path responsive to the energization of said release relay to energize said changeover relay.

23. In a switch control circuit for use in automatic switching apparatus, a line relay, 8. release rela a changeover relay, means for closing a circuit for said changeover relay upon the seizure of the control circuit, a shunt path around said changeover relay preventmg its energization, means for energizing said line and release relays responsive to the seizure of the control circuit, means for open ing said shunt path responsive to the energization of said release relay to energize said changeover relay, and a second shunt path for said changeover relay controlled by said line relay.

In witness whereof, I hereunto subscribe my name this 23d day of November, A. D.

NORMAN H. SAUNDERS.

Disclaimer 1,868,994.-N0rmd?n H. Saunders, Homewood, Ill. TELEPHONE SYSTEM. Patent dated July 26, 1932. Disclaimer filed Sept, 8, 1950, by the assignee, Aut0- matic Electric Laboratories, Inc.

Hereby enters this disclaimer to claims 1, 2, 3,

and 4 ofsaid patent. [Ofiicial Gazette October 3, 1 9501 1'}

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