US1614593A - Automatic telephone system - Google Patents

Automatic telephone system Download PDF

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Publication number
US1614593A
US1614593A US13961A US1396125A US1614593A US 1614593 A US1614593 A US 1614593A US 13961 A US13961 A US 13961A US 1396125 A US1396125 A US 1396125A US 1614593 A US1614593 A US 1614593A
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armature
magnet
circuit
relay
winding
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US13961A
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John I Bellamy
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Automatic Electric Inc
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Automatic Electric Inc
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04Q—SELECTING
    • H04Q3/00—Selecting arrangements

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  • the present invention relates, generally stated, to automatic telephone systems and presents new and improved means for makingthe operation of switches, used in such systems, more reliable.
  • my invention contemplates a positive stop arrangement for trunk hunting switches having an operating magnet which is operated in a local circuit.
  • One object of my invention is to produce an efi-"icient circuit arrangement for a finder switch of the single-motion rotary type in which the wipers are operated on the torward stroke of the magnet in hunting-for a calling line, the calling condition of the line being characterized by the presence of ground upon the test contact. Vi hen such grounded test contact is reached, I do not merely disconnect the n'lagnet in order to prevent its further operation, but lock the magnet in its operated position until such circuit changes have taken place which insure against any possibility of advancing the wipers beyond the desired position.
  • 1 apply the same general principle-al though differing in details from the former arrangement-to a finder switch in which: the wipers are advanced on the back stroke rather than on the forward stroke of the stepping magnet.
  • a further object'of my invention resides in modifications of the general principle with the view of producing circuits similar to those described above, adapted for use in connection with switches which test for the absence of ground upon the test contacts. Selector switches of the two-wire type are arranged to test in this manner. Accordingly', this phase of the invention is shown as applied to selector switches, and I have shown: a number of modifications illustrating various ways in which the invention may be carried out, each method having its own particular adaptation.
  • circuits are shown in connection with finder switches and selectors only, it will be obvious that they can be adapted for use in any circuit where a freehunting movement is desired.
  • Fig. l I have shown a finder switch oi the single-motion rotary type advancing. its wipers on the forward stroke of the stepping magnet, and Fig. 3 illustrates a finder switch which operates its wipers on the backstroke, but may to equal advantage be used for a finder operating the wipers on the for-- ward stroke, as will appear clear from the detailed description which is yet to follow.
  • Figs. 1 and 3 I have shown the usual subscriber substation and line equipment, consisting of the substation apparatus A and A, and the line circuits LC and LC, individual to the respective substations and located at the central ofiice.
  • Figs. 2, and 4-10, inclusive I have shown circuits for selector switches of the type which advance the wipers first in a vertical plane to select a group and then in a horizontal plane to automatically select a trunk in the selected group.
  • Fig. 1 it will be assumed that the subscriber at substation A desires to make a call and, accordingly, removes the receiver from the switchhook.
  • Relay 3 When the receiver is removed at substation A, a circuit is closed over line conductors and 31 for the line relay 3.
  • Relay 3 energizes and operates armatures 13, 14 and 15. Armature 13, upon being attracted, connects ground to the test contact 34 of the finder ban; to permit'the finder to test for the calling line; armature 14 prepares a circuit for the cut-oii relay 2 which will be completed when wiper 39 of the finder switch F reaches the bank contact and armature 15 connects ground to the start conductor 15.
  • Line relay 6 of the finder switch energizes upon ground being connected to start conductor 45, and completes a circuit for the stepping magnet 4 over the normally closed contacts controlled by armature 18, back contact and armature 16, front contact and armature 24c to ground.
  • the finder switch F is of the kind which advances its wipers on the forward or energizing stroke of the stepping magnet. Accordingly, the wipers 37%0, inclusive, are now advanced one step.
  • the stepping magnet attracts its armature 16, thus opening its own circuit.
  • the wipers advance another step.
  • the finder switch in this buzzerlike manner, operates very rapidly and moves its wipers over the bank contacts. hen the calling line is reached,
  • the upper winding of switching relay 5 is of low resistance and permits the stepping magnet to remain energized.
  • the finder switch is, therefore, positively and very effectively stopped and it is apparent that no additional step can possibly be taken.
  • the switching relay 5, having been energized over its upper low resistance winding in series with the stepping magnet t attracts its armatures and completes a holding circuit for itself over its lower high resistance winding and armature 18 and its front contact to battery over stepping magnet 4.
  • the stepping magnet upon being connected in series with the high resistance winding of switching relay 5 does not receive sui'licient current to keep its armature in operated position and releases, while the switching relay remains energized. Accordingly, the armature 16 and the mechanism advancing the wipers assume their normal positions.
  • Stepping magnet 1 cannot be operated again because of its energizing path being opened.
  • the switching relay connects the grounded release trunk conductor 413 to wiper 3.1; connects up wipers 37 and at armatures 17 and 22; and at armature 21 opens the circuit of line relay 6 and prepares the extension of the common start conductor 15 through armature 25 and its resting contact and conductor 11 to the next finder switch.
  • Line relay 6, being slow acting, however, does not release for an interval.
  • the cut-oii' relay 2 of the line circuit LC operates through armature 14 and working contact responsive to the grounding of wiper 39, and disconnects the line relay 3 and ground from the calling line at its armatures 10 and 12, and connects its own winding into a locking circuit at its armature 11.
  • Line relay 3 deenergizes thereupon and removes groundfrom the test contact 34 at its armature 13, and disconnects ground from the common start conductor 15 at its armature 15.
  • Armature 1a is opened also, but the holding circuit of the cut-off relay 2 is maintained over armature 11, which also maintains a ground potential upon the private normal conductor 32 terminating in a connector switch, for marking the line busy in accordance with the usual practice.
  • the line relay of the selector Fig. 2 operates over the calling line and completes a circuit for the release relay 102 .over its armature and its front contact.
  • the release relay 102 energizes and, by means of its armature 111, connects ground to the release trunk conductor 43 before the slowacting line relay 6 of the finder switch has had time to deenergize.
  • Armature 112 prepares a circuit for the rotary magnet 106, and .armature 113 prepares at its front contact a circuit for the vertical magnet 107, and at the same time disconnects the release magnet 105.
  • the calling subscribers substation is now connected to the selector switch and he may operate his dial to transmit the first digit of the desired partys telephone number.
  • the line relay 100 decnergizes a number of times, and upon each deenergization completes a circuit for the vertical magnet 10-7 in series with relay 103 over front .con-
  • line relay 100 energizes for a relatively long period of time, and relay 103, its circuit being opened at armature 110, deenergizes and completes the circuit for rotary magnet 106, which circuit includes the off normal contacts 135 operated in the usual manner upon the first vertical step, front contact and armature 112, armature 11 i and its back Contact, normally closed contact controlled by armature 117, normally closed contact controlled by armature 121, winding of the rotary magnet 106 to a neutral point of battery 140. It will be seen that I haveshown a neutral point tapped off from the regular exchange battery and that the circuit traced above includes only the upper part of said battery.
  • the rotary magnet 106 must be suitably wound to respond to this arrangement.
  • the rotary magnet 106 upon energizing, advances the wipers -127, inclusive, one step and positions them on the first set of bank contacts in the selected level, and at the same time attracts its armature 121, thereby connecting switching relay 104 to the rotary magnet circuit and inserting the resistance 109 in series with the rotary magnet. If the first trunk is idle the rotary magnet 106 remains energized through resistance 109 and the switching relay 10 i operates immediately (over a circuit to be pointed out later), seizing the trunk.
  • This new circuit includes the lower part of the exchange battery 140, center of the battery, rotary magnet 106, front contact and armature 121, resistance 108, back contact and armature 116, wiper 126, and ground at the busy test contact. It will be seen that, with the initial circuit of magnet 106 still established, except for the inclusion of resistance 109, and with the new circuit established through resistance 108, the direction and strengh of current flow through magnet 106 depends upon the relative values of the resistances 108 and 109. Resistance 109 is relatively high and resistance 108 is relatively low. Resistance 109 allows just enough current to pass to maintain magnet 106 operated in case the new circuit is not established, and the reslstance 108 merely high enough to prevent an excessive current flow during the instant when the three contacts of the magnet are all closed together. Accordingly,
  • magnet 106 operates its armature again, thereby advancing the wipers to the second trunk line.
  • the wipers are advanced in this manner until an idle trunk is found. Assume this idle trunk to be the one shown in the drawing and comprising the trunk conductors 131, 132 and 133.
  • this idle trunk to be the one shown in the drawing and comprising the trunk conductors 131, 132 and 133.
  • the rotary magnet 106 remains energized in series with resistance 109 because no ground potential is encountered by the wiper 12.6 to bring about its deenergization.
  • the rotary magnet is in this manner held in its operated position and prevented from taking an extra ste ⁇ Vith magnet 106 operated, and with wiper 126 ungrounded, switching relay 104 (whose low r terminal is connected to the junction of resistance 100 and magnet 106, and whose upper terminal is connected with the grounded release trunk conductor 104;) energizes and locks itself over armature 117 and its front contact to the mid tap of battery in series with resistance 109 and the rotary magnet 106, at the same time disconnecting the high voltage battery lead from the rotary magnet circuit. The rotary magnet 106 is now disconnected from the upper terminal of the battery 1 10 and it accordingly falls back.
  • magnet 106 places a local shunt around the resistance 109 when it falls back, and it also opens at armature 121 the initial circuit of relay 10 1 leaving switching relay 104- locked up at armature 117.
  • switching relay 10 1 opens the test circuit and prepares the usual holding circuit at armature 116 it removes ground from armature 110 at arn'iature 119, thereby opening the release ,relay circuit and opening a point in the release magnet circuit; and at armatures 11:") and 120 it disconnects line conductors 12 and 1 1- from line relay 100 and extends them by way of wipers 125 and 127 and conductors 131 and 133 to the line relay of the switch to which the seized trunk extends.
  • the line and release relays (not shown) of the seized switch now pull up and the latter places ground on release trunk conductor 1232, thereby establishing the usual holding circuit before the slow acting release relay 102 has had time to fall back.
  • a circuit is prepared for the release magnet 105 after the line relay 100 and the releaserelay 102 have restored, which circuit includes the armatures 110 and 118 and the cit normal contact 136. llowever, release magnet 105 cannot energize at present due to its circuit having been opened at armature 119 upon the energization oi? the switching relay 10 1.
  • a circuit for the holding relays or the finder F and the line circuit LC is still established through the upper portion of the exchange battery.
  • the current flow takes a path including the normally closed contacts controlled by armature 121, working contact and armature 117, and switching relay 10 1 to the release trunk conductor 43 of the selector. From this point, the current flow continues over the release'trunk conductor to the exchange battery tap by way of the two paths.
  • One path includes the lower winding of switching relay 5 of the finder l1, armature 18 and its working contact, and the stepping magnet 4C.
  • the other path includes the working contact and armature 20, wiper 39, hank contact 35, armature 11 and its working contact, and cutoil relay 2. Accordingly, it may be assumed hat relays 2 and 5 do not fall back responsive to the mere removal ot' the ground po tential from the release trunk conductor 43, but remain energized in parallel with switching relay 104, Fig. 2.
  • relay 104 disconnects its lower terminal from the rotary magnet circuit at armature 117 current ceases to flow through its winding, and relays 2 and 5, Fig. 1, fall back.
  • relay 10 i completes at its armature 119 the circuit of the release magnet 105, which re.-
  • the restoration of the finder switch F and of the line circuit LC takes place simultaneously with the release of the selector.
  • Switching relay of the finder, and switching relay 2 of the line circuit deenergize as above pointed out, and, as can readily be seen, restore the normal conditions, i. e., the line conductors 30'and 31. are again connected to ground and to the line relay 3, respectively, over the armatures and 12, the wipers 37 and 40 of the finder switch are disconnected from the trunk conductors 4.2 and 44, and wiper 39 from the release trunk conductor 43, while the start conductor 45 is again connected to the line relay 6 by way of armature 21.
  • the wipers will not be advanced but remain positioned on the bank contacts 333'6, respec tively.
  • switch F shown in Fig. 3, which is assumed to operate together with the selector switch shown in Fig. 4.
  • the line circuit LC is in every respect similar to that shown in Fig. 1. I shall, therefore, refrain from repeating the de scription of the operation of the line circuit LC, but limit myself to pointing out the operation of the finder F as far as it differs from that of the finder switch already eX- plained.
  • the finder switch circuit F is particularly designed for finder switches which advance the wipers on the back stroke. How ever, as will be pointed out hereinafter, it can equally be used for finder switches of the other type advancing the wipers on the forward or energizing stroke and will be found to be especially useful in connection with a switch of the latter type, if a stepping magnet is employed which requires a great amount of current for operating and holding.
  • the finder switch F is one which advances its wipers on the back stroke, and that the subscriber at substation A desired a connection and accordingly removed the receiver from the switchhook.
  • tart relay 6 energizes upon ground being connected to start wire 45 and completes at its armature 24s a circuit for the stepping-magnet 4 which circuit includes armature 26 of a relay 7.
  • the stepping magnet upon energizing, attracts its armature 16 thereby closing a circuit for relay 7 parallel to its own circuit.
  • Relay 7 energizes and opens at its contact 26 the circuit of stepping magnet a.
  • the stepping magnet deenergizes and advances the wipers 3740, inclusive, in the usual manner, one step, positioning them on the next set ofbank contacts, and at the same time opens at its armature 16 the circuit for relay 7 which deenergizes thereupon and starts a new cycle at armature 26.
  • the wipers are thus advanced over the bank contacts, and arrive on the contact set of the calling line with relay 7 energized, and
  • the holding circuit of switching relay 5 and relay 7 includes at this time armatures-19 and 24L to ground.
  • Start relay 6, being a slow-acting relay does not deenergize before the lapse of a sufficient period of time to permit the selector switch to connect ground to the release trunk in the usual manner.
  • the finder switch F is one which advances the wipers upon the forward or energizing stroke.
  • the wipers are advanced in the same buzzerlike manner through the action of stepping magnet 4: and relay 7.
  • the only difference in operation which must be considered is that, whereas the testing operation took place in the former case innnediately upon the arrival of the wipers upon the contacts of the calling line, the testing operation in this case is delay-ed until magnet 1 falls back and opens its armature 16, after having advanced the wipers to the calling line.
  • the selector switch shown in Fig. 4 which is assumed to operate together with the line finder switch F shown in Fig. 3, is, as may be seen from the drawing, very similar to that shown in Fig. 2.
  • the line relay Upon the line conductors of the calling substation being extended over the trunk conductors 12 14, the line relay energizes and causes the operation oi? the release relay.
  • the release trunk is thereby connected to ground before the slow-acting start relay of the finder switch has had time to deenergize, and the circuit for the series relay and for the vertical magnet is prepared
  • the wipers will be raised now opposite a certain level in response to the first digit in a manner described previously.
  • series relay 103 deenergizes and completes at its armature 114 the circuit for the rotary magnet 106', which circuit includes the off normal contacts 135, front contact and armature 112', armature 114C and its back contact, armature 118 and its back contact, back contact and armature 121, and winding of the rotary magnet 106.
  • Current is drawn from the upper part of the battery.
  • the rotary magnet operates and positions the wipers on the first set of bank contacts, and, if this set of contacts is idle, the switching relay operates. Assuming the first set to be busy, however, ground is encountered by wiper 126' at the test contact and the switching relay 10 1* cannot operate due to its upper winding being short-circuited at armature 111. Current is reversed in the winding of the rotary magnet, causing it to de-magnetize quickly, the circuit including the grounded test contact, wiper 126 armature 116 and its back contact, t'ront contact and armature 121. winding of the rotary magnet 106', and the lower part of the battery 140.
  • the connection to the desired party is completed in the usual manner.
  • the release operations of the selector, Fig. 1, and of the line finder F and line circuit LC shown in Fig. 3 are substantially the same as the restoration of the selector Fig. 2 and the finder swi ch disclosed in Fig. 1 with the exception that, since relay 10 1 is held up over the entire exchange battery in this case instead oi": over only half, as in the preceding case, all the relays connected to the release trunk conductor fall away in the usual manner.
  • a circuit for the rotary magnet 202 is completed when the series relay deenergizes upon the termination of the first digit, which circuit includes the oft-normal contact 205, normally closed contact controlled by armature 203, right hand winding of the rotary magnet 202, normally closed contact controlled by armature 208, armature 219 of the series relay to ground at armature 220.
  • the rotary magnet operates and advances the wipers 213-215, inclusive, into engagement with the first set of bank contacts in the desired level. If this trunk is idle. the switching relay 201 energizes immediately.
  • the switching relay 201 is short-circuited over the left hand holding winding of the rotary magnet 202 by ground encountered by the test wiper 21a and does not operate.
  • the rotary magnet upon energizing, attracts its armature 203 thereby opening the normally closed contact.
  • the rotary magnet having the circuit of its right hand operating winding interrupted and its left hand holding winding short-cireuited, deenergizes now, thereby closing the circuit for its operating winding again.
  • the operation of the rotary magnet continues thus until an idle trunk is reached, which trunk it is assumed is the'one terminating in the bank contacts 216218, inclusive.
  • the switching relay 201 being not short-circuited at this time now operates over its lower winding in series with the left hand holding winding of rotary magnet 202 and resistance 200.
  • the switching relay upon energizing, extends the line conductors and the release trunk in the usual manner and locks itself to ground at the release trunk over its upper winding and armature 208, thereby opening the normally closed contact and disconnecting the holding and operating windings of rotary magnet 202.
  • the rotary n'iagnet operates now over its left hand winding and its interrupt-er armature 232 and advances the wipers 239-21 inclusive, into engagement with the first set of bank contacts.
  • switching relay 227 energizes over its lower winding and the right hand holding winding of the rotary magnet in series with resistance because of the short-circuithaving been removed atarmature 231 upon the energiZ-ation of the rotary magnet. The rotary magnet is thus locked during the operation of the switching relay and prevented from taking an additional step.
  • the switching relay upon energizing, attracts its armatures and extends the line and the release conductors in the usualmanner and locks itself over its upper winding and armature thereby also tie-energizing the rotary magnet.
  • the first trunk to be busy ground is encountered by wiper 240 keeping the lower winding of the switching relay and the right hand holding winding of the rotary magnet further shortcircuited, though the short-circuit at armature 231 has been hereoved upon energization of the rotary magnet, because of ground from armature 228 connected to the lower winding of the switching relay by way of armature 229 and the normally closed contact controlled by armature 235.
  • the rotary magnet dee'nergizes and advances the wipers to the next set of bank contacts and continues with this operation until an idle trunk is reached.
  • Fig. 7 shows a selector switch having a differentially wound rotary magnet. The latter energizes initially over its left hand .vinding upon the closure of armature 255 after the wipers have been positioned op posite a certain level, the circuit including the armature 253 and its front contact, off
  • the switching relay The switching relay
  • the switching relay In energizing, the switching relay extends the line and release trunk in the usual manner and disconnect-s at armature 259 the energizing path of the left hand winding of the rotary magnet and locks itself in series with the latter over its armature 250. The rotary magnet now deenergizes because of the high resistance of the switching relay.
  • the series relay deenergizes and closes its armature 30? upon the. wipers being positioned opposite a certain level.
  • a circuit is completed now for the rotary magnet 300 which includes the armature 305 and its trout contact, oft normal contact 306 which had been closed upon the first vertical step of the switch, armature 307 and its back contact, normally closed contact controlled by armature 300, normally closed contact controlled by armature 311, winding of the rotary magnet 300, and short circuit around resistance 302 at armature 315 and its back contact.
  • the rotary magnet thereupon energizes and advances the wipers 318-320 into engagement with the first set of bank contacts. It this set of contacts is idle, switching relay 301 operates.
  • This latter circuit may be traced from ground at the test contact, wiper 819, armature 313 and its back contact, armature 314i, winding oi? the rotary magnet, normally closed contact controlled by armature 311 and armatin'e 309 to battery over resistance 30 1.
  • the short'circuit around resistance 302 is removed, during testing, at armature 315.
  • the operation of the rotary magnet continues in this manner until an idle trunk is found which trunk it is assumed is the one terminating in the bank contacts 321-323, inclusive.
  • the switching relay in energizing, extends the trunk conductors as usual and locks itself over its armature 311 in series with the rotary magnet 300 to battery, at the same time disconnecting the holding circuit of the rotary i'i'iagnet at the normally closed contact controlled by armature 311.
  • the rotary magnet dc energizes because it is short circuited through armatures 311 and 314;, and it does not operate again on account oi the high resistance of the switching relay.
  • Fig. 9 I have shown a modification ot the selector switch shown in 7.
  • the rotary magnet 330 is also differentially wound, the switching relay 331, hmvever, has two windings instead of one, and the opera tion of the switch is accordingly slightly diiterent. It will also be observed that the contactarrai'igement 330 is different from that shown in Fig. 7 and designated through the numeral 256, and that ll have avoided the use of a resistance such as 252 shown in Fig. 7.
  • the series relay tie-energizes as usual upon the termination of the vertical movement of the switch and closes at its armature 335 a circuit for the left hand winding of the differenti'a-ll'y wound rotary magnet 330.
  • This circuit includes armature 332 and its front contact, ofl normal contact armature 335 and its back contact, and the normally closed contact controlled by armature 339.
  • the rotary mag-net thereupon energizes and moves the wipers into engagement with the first set of bank contacts. If the first trunk encountered is idle, the switching relay 33-1 energizes immediately.
  • a circuit for the rotary'magnet 351 which includes the normally closed contact controlled armature 35 i, short-circuit around resistance 350, left hand operating winding of th rotary magnet 351, the normally closed contact controlled by armature 359, back contact and armature 355-, off normal contact 353, back contact and
  • the rotary magnet energizes in this circuit and advances the wipers in the usual manner positioning them: on the first set of 7 bank contacts.
  • Armature 354 of the rotary magnet closes its contact and opens the normally closed contactthereby removing the shunt around resistance 350 and connecting this resistance in series with the left hand operating winding, while the right hand, opposedwinding, is' connected to battery.
  • the switching relay 3'52 If the trunk on which the wipers are resting is idle the switching relay 3'52 operates. Assuming the trunk to be busy,however, ground is encountered by test wiper 363 and the switching relay is prevented from energizing because of a short-circuit to ground at armature 356. A circuit is closed instead for the right hand winding of the rotary magnet over armature 358 and its back contact. The rotary magnet having both its windings conn-ected to current restores because of the differential action and closes its original operating circuit again to advance the wipers another step.
  • a stepping magnet a test wiper
  • a stepping magnet a test wiper, a circuit includ ing said test wiper tor intermittently energizing and tie-energizing said magnet to drive the switch over busy lines, and a looking circuit for holding the magnet energized when an idle line is reached.
  • a stepping magnet In an automatic hunting switch, a stepping magnet, a circuit ⁇ or intermittently energizing and de-energizing said magnet to drive the switch over busy lines, a locking circuit for holding the magnet energized when an idle line is reached, and a shunt circuit including the test wiper o1 said switch for rendering said locking circuit ineffective as long as said wiper engages busy test contacts.
  • a stepping magnet a circuit for intermittently energizing and deenergizing said magnet to drive the switch over busy lines, a locking circuit tor holding; the magnet energized when an idle line is reached, a shunt circuitincluding the test wiper of said switch for rendering said locking circuit ineffective as long as said wiper engages busy test 0011- tacts, and a switching relay energized in said locking circuit when the same becomes effective.
  • a stepping magnet In an automatic hunting switch, a stepping magnet, a circuit for intermittently energizing and de-cncrgizing said magnet to drive the switch over lnisy lines, a locking circuit for holding the magnet energized when an idle line is reached, a shunt circuit including the test wiper of said switch for rendering said locking circuit ineffective as long as said wiper engages busy test contacts, a switching relay energized in said locking circuit when the same becomes effective, a. locking circuit for said relay, and contacts on said relay for breaking said magnet circuits.
  • a stepping magnet for driving the switch, and means for operating said magnet by intermittently reversing its polarity.
  • a mag net controlling selection of an idle line, a circuit for energizing said magnet, a switching relay, a circuit for energizing said relay, a test wiper, and a circuit including said test wiper for shunting said relay and for deenergizing said magnet.
  • a mag net for controlling advance of the switch, a circuit for energizing said magnet, a second circuit including said magnet for rendering said first circuit ineffective, and means for operating said magnet by closing and opening said second circuit.
  • a magnet in an automatic hunting switch, a magnet, a circuit for energizing said magnet to advance the switch wipers into engagement with a line, a test wiper, and a circuit including said test wiper and the said magnet for tie-energizing the magnet in case the engaged line is busy.
  • an automatic hunting switch a magnet, a circuit for energizing said magnet to advance the switch wipers into engagement with a line, a test wiper, a circuit including said test wiper and the said magnet for tie-energizing the magnet in case the engaged line is busy, and means for breaking said second circuit when the magnet is deenergized to render the first circuit again effective to advance the wipers to the next line.
  • said magnet having only a single winding and means for operating said magnet by intermittently reversing the direction of current flow in said winding.
  • a magnet in an automatic hunting switch, a magnet, a circuit including a winding of said magnet for energizing the same, a second circuit including said winding but carrying current through the same in the opposite direction, and means controlled by said magnet when energized for closing said second circuit.
  • a magnet In an automatic hunting switch, a magnet, a circuit including a winding oi said magnet for energizing the same to advance the switch wipers into engagement. with a line, and a second circuit closed only in case the engaged line is busy for reversing the direction of current flow in said magnet winding to de-energize the magnet.

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  • Computer Networks & Wireless Communication (AREA)
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US13961A 1925-03-09 1925-03-09 Automatic telephone system Expired - Lifetime US1614593A (en)

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US13961A US1614593A (en) 1925-03-09 1925-03-09 Automatic telephone system

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