US1695267A - Automatic telephone system - Google Patents

Description

Dec 18, 1928. 1,695,267

F. ALDENDORFF AUTOMATIC TELEPHONE SYSTEM Filed Jan. 12, 1925 4 Sheets-Sheet 1 Dec. 18, 1928. 1,695,267

F. ALDENDORFF AUTOIA'IIC TELEPHONE sYs'ral Filed Jan 1925 4 Sheets-Sheet 2 Dec. 18, 1928.

F. ALDENDORFF AUTOMATIC TELEPHONE SYSTEM 4 Sheets-Sheet Filed Jan. 12, 1925 mm vk Dec. 18, 1928.

1,695,267 F. ALDENDORFF AUTOMATIC TELEPHONE SYSTEM Filed Jan. 12. 1925 4 Sheets-Sheet 4 49 g 44/ I i 42* 4 a 0 0 Patented Dec. 18, 1923.

UNITED STA E PATENT oFFi-cs.

ram: Ammmom, a mBnm-mfinnsnonn GERMANY; cashmere ALDBNDOBFF music! mum snmnmonrr, DECEASED.

m TELEPHONE srs'rau.

Application filed-January 12 192 Scria1'No.1,889, and in Germany January 14, 1924.

This invention relatesto selectoi'js andtelephone systems operating with selectors and its object is to provide devices by wh ch wrong connections rising from the fact that 5 the line finders, grou selectors etc. operate too slowly to res n to very uick movenients of the switc controllers, are obviated.

In accordance with the invention a selector is used inwhich there is provided for every line connected to its contact bank a designattact, and a brush that wipesover the designating contacts and throughawhich acurrent flows that passes through an electromagnet which causes the voice current breshes to be stopped on a certain line. The hrushes are stop by a detent thatengages with teethof the sh carrier. In accordance, with another feature oftheinvention the brushes are stopped by an armature (retracting) of an electromagnet and a member moved with the brushes thathas as many teeth or the like as there are individualsets of contacts in the contact bank. The res nseof the electroet armature is aoce erated-in accordance wit the invention by ooaincctinga'condenser in. parallel to the electromagnet or weakening the exciting current of the electromagnet after its armature has been attracted,or by causing the armature to retract through the efl'ectof counteracting ampere, turns.

A further feature of the invention consists in a selector in whichone and the same magnet is used for starting and stop ing the selector brushes. Themagnet maybe arranged to start the selector when it is energized and to stop its operation when the magnet is de-energized. 4 vention consists of driving the brushes of a selector by a power such as spring wer, and in case they are not stopped on t e desired line, in moving them step- I K-step by an electromagnet armature until t ey reach thedesired line. The step-by-step motion may be obtained by arranging the electromagnet armature so that it engages with the teeth of the brush carrier and liberates one tooth after another. In accordancewitha further feature of theinvention the line a on whose contacts in the contact bankpf t a selector the brushes have been stopped, is marked by changing the potential of a plurality of bank contacts Further features 015: the invention consist in using a selector vofcthef aforedescribed kind asa line findexggroap selector mg contact in addition to the usualtest con- A further featureof the inorconnector. The brush carrier maybe ar ranged to execute rotary motions only or it may be arranged to also'be moved longitudinal y. i

The invention is illustrated in the drawing in which 7 y 1 v =Fi'g. 1 shows a constructional form of the selector and Fig. 1 showsa part of a selector whose brush carrier may be moved longitudinally and rotated.

Fig. 1 shows the longitudinal movement cF'cmtrolling mechanism a of the switch of ig. 2 shows acircuit arrangement for the selector when used as a linefinder.

I Fi 3 shows circuits of a selector with a longitudinally movable "and rotary brush shaft. I a

, Fig. 3 illustratescircui'ts of a group selectorwhose brushes execute rotary movements only.

Fig. 4 shows circuits of a connectorfthat executes rotary movements only. i

,F'g. 5 shows a circuit in which the quick stopping effect-of the stopping magnet is obtainedby inserting a resistance in its energizing. circuit. q i

.Fig. 6 shows a cir'cuitin which the quickstoppingeffect of the stoppingmagnct armature is attained by counteracting ampere turns.

a F ig. 7 illustrates a form of the selector in which,,instead of two toothed wheels as in Fi 1 only one toothed wheel is employed.

7 ig. 8 illustrates diagrammatically a portion of the. contact bank and shows the displacement of the designating contacts Selectors whose circuits are arranged as shown in Figs. 2, 3 and 4 may, on the whole, be built in the manner illustrated in Fig. 1 except that a cam disk 300, Fig. 3 or 400,

'Fig. 4 which is not provided in Fig. 1, is

combined with the brush carrier when the selectoris to be usedas a group selector or connector; 7 p y i I 1 a In Fig. 1', 1 is a shaft which has brushes 2,

3, 4', 5 fiixed to it that are insulated from each other and from the shaft. Also fixed on the shaft 1 is atoothed wheel 6 whose hub 7 rests on the bearingS. J ournalled so as to rotate on the shaftl toothed wheel 10 with a spring box 9. The spring box 9 has an upwardlyextending hub 11 and a downwardly extending hub 12 that rests on abushing 13 fixed to the shaft 1. I One end of the spring 14 sprint? iox 9 rotated in the direction of the arrow 16, a holding pawl not shown) being provided which prevents backward rotation of the spring box 9. hen the spring box 9 is wound up the wheel 17 is held against movement by the pawl 18 ot a magnet 19 so that the shat-"t 1 with the brushes i3. 3, 1. is also prevent mil from rotating. Mounted on the wheel 1'? are two slip rings 29 to which current is conduct. by two brursihcs 21. Thetwo slip rings are intercounected by a contact that is carried round with the wheel 11' when this wheel is moved out of its normal rotary position with respect to the spring box 9. int as soon as the wheel occupies a certain position with respect to the wheel 1? a pin 21- ot the wheel 10 raises a pin 23 and thus opens the contact that interconnects the rings 20. This contact or switch designated 25 in The spring 11, when it is wound up, tends to turn the brush carrier 1 with its wheel 17 in the direction of the arrow 26 and it executes a turn in this direction when the starting and stopping magnet 19 is energized.

In a selector with a longitudinally movable shaft 1. Fig. 1, a toothed wheel 1'? corresponding to the wheel 17, Fig. 1 and a spring be); 9 corresponding to the spring box 9, Fig. 1. and having a circle of teeth 19, is provided. The toothed wneel 17 however has a hollow hub 7 upon which the springbox 9 is adapted to rotate. The shaft 1 extends downwardly through the spring box and has a series of circular teeth with which the pawl of a lifting magnet 28 may engage. The shaft 1" has a groove 29 into which a pin 30 arranged in the box 01 the wheel 1'? protrudes. so that the shaft 1 may move lengthwise in the wheel 17 but cannot turn therein. l'lj' the litting magnet 28 the shaft 1. may be lifted step-by-step and when the wheel 17 is then released by a magnet cm'respoinfliug to n'iagnet 19. 1, the shaft is rotated by the spring 1-1 of the spring box until it is stopped in the manner hereinafter described. The shaft 1 is restored to its normal position by its being turned until a pin 31 of the same strikes against a slide way in the form of a long stop 3;. When the snatt is in this position a holding pawl 33, Fig. 1 will register with a groove 34.- in the shaft so that the latter drops down. \Vhen the pin 31 has fallen beneath the slide way -32 the spring turns the shaft a little further round until the pin 31 is restored to the position shown in Fig, 1 and the holding pawl 201, Fig. 8. engages with the wheel 17 and holds it and the brush carrier in the normal position indicated in Fig. 3.

ply placing Figs. 2, and 4 side by side a complete circuit arrangement for an exchange with line finders, Fig. 2, group sclectors, Fig. 3 and connectors. Fig. i, is obtained.

It will now be assumed that a subscriber S, Fig. 2, desires to establish a connection with the line 224. When the subscriber S raises his receiver a current flows "lfrom the positive pole through the line relay -19, con tact 41, sub-station S, contact lil of the cut oti' relay 43 to the negative pole. T he line relay 40 closes its contact 41. and opens contacts to, -17. The opening of the contacts 16, 17 results in the positive pole being disconnected from the designating contacts 48, 49. By the closure of the contact -15 the cut-otl' relay 43 is connected to the test wire 59 and test contact- 51 of the cilling subscriber. At contact 11 a circuit closed which extends from the positive pole through the starting relay 51 ot' the line tinder 52. T he relay 51 sends a current from the positive pole through its contact 53, brush 5%. of the trunk finder, contact of relay 56, starting magnet 19 to the negative pole. The starting magnet 19 pulls its stopping pawl 57 away from the wheel 17 and this latter is now turned at a high speed by the spring 11, Fig. l. lVhen the wheel 1? with the brushes 58. 59, 60, 61 is moved out of its normal position the off-normal switch is closed and the relay 56 is energized. The starting magnet 19 is then maintained encrgiz d by a current that flows through the contact 62 of the relay 64, wiper and the designating bank contacts 65 that are connected to the positive pole oi" the battery. The magnet- 19 remains energized until the. brush 58 reaches the bank contact =19. The armature 57 then retracts and stops the wheel 17 so that the wipers 59, 60, in are held on the contacts 66, 67. 69. If magnet 19 does not operate .tast enough it could happen that the brush 5S over-steps the contact 4 9 and only stops on the next; contact 48 from which the positive pole is also disconnected by the contact 4-7. In any case. if necessary, as many contacts 48, 49 are disconnected from the positive pole as are necessarv to prevent the brush 58 from flying past the last b nl; contact that is disconnected from the positive pole. which n'iight happen it' the armature 57 acts too slowly. The calling line is always the one that corrcspoinls to the last contact 48 that is disconn cted from the P it ve pole. \Vhen the brushes are stopped n the first cmitact 419 disconnect d from the positive pole the magnet 19. as soon as its armature L39 falls back, receives a current inipulse that flows through contact 69. T9. 71. (33 to the negative pole. The armature 57 is thus again attracted and allows the toothed wheel 17 to turn through an angle corresponding to a further tooth in the direction of the arrow, because. in consequence of the interruption at 69 and of the disconnection lit) of the positive pole from the contact 48, the armature 57 immediately drops back again and again stops the wheel 17; The .test

brush 58 will now be resting on the bank con tact 51 which is connected through the cutoil' relay 43 to the negative pole. Hence the relay 72 will be energized by acurrent flowing from the positive pole through 53, 5-4, 72, 59, 51, 45, 43 to the negative pole. 'Tho self-interrupter 69"is switched off at 70 so that the armature 57 of the magnet 59 mains still. It is to be noted that the magnet 19 is made to allow its armature 57 to drop back extremely quickly by a'condcnser 7 3. The relay 72 closes its contact 7 3 vand thus renders the calling line engaged so that further relays like 72 or test relays in the connee-tors :unnot be energized when the brushes of other selectors are stopped on the bank contacts of the calling line. The relay 72 by its contacts 74, 75 also connects the calling line through to the group selector, Fig. 3, so

that the impulse relay 202 of the group solector is energized. Furthermore the relay 72 by its contact 76 opens the circuit of the rewinding magnet 15 which would otherwise be closed when the release relay 203and the relay 64 are energized. The calling sub scriber now sends in a series of two impulses, i. e. he causes two interruptions of his loop to ,take place in rapid succession so, that the armatures 204, 205 drop back twice and two impulses flow fromthe negative pole through contact 206 which" was closed (due to a current from the negative pole to 204, 203', 207 to the positive pole) when the relay 202 was first energized, contact 208, c0ntact209, lifting magnet 28 to the positive pole. The lifting magnet 28 now raises the shaft 1, Fig. 1 with the brushes 210, 211, 212, 213 step-by-step until they reach the second level of the contact bank. The calling subscriber having now sent in histwo hundred-impulses, the armatures 204, 205 now remain attracted for a relatively long interval so that the relay 214 which was energized through 206, 214, 215 is kept short circuited at contact 216 until its armature drops back and the contact 217 is closed. As the vertical oif-normal switch 218 was closed at the first vertical step of the shaft the starting magnet 219 now receives a current which flows from the regative pole through 220, 218, 217, ofi-normal switch 221,229 to the positive pole. The wheel 17' and the shaft 1 with the brushes 210213 is now released for rotary movement so that the spring 14' whirls the brushes round until the magnet 219 which is bridged by a condenser 222 and receives current during rotation of the brushes through the contact 223, brush 213 and bank contacts such as 224 connected to the negative pole, is de-energized. This de-energiaa tion takes place as soon-as the brush 213 reaches :1 contact 224 Whose wire 225 is due 212, wire 228, resistance 401, oil-normal sends in twotens impuls s.

t, 'msl contact 41f left hand windin connected from the negative pole gthis wire leading to a tree connector, Fig. 4. The stopping pawl 207 engages with the wheel 17 and arrests the brushes 211, 212, 213 on wires leading to the connector, Fig. 4. In the group selctor, Fig. 3 the relay'226 is now energized by a current thatflows from the negative pole through 220, retracted armature 227 of the magnet 219, 220, brush contact 402 of the connector to the positive pole. The relay 226 opens the contacts 229, 230, 231 and at the some time extends the voice current wires through the wipers 210, 211 to the impulse relay 402 of the connector. The impulse relay 202 of the group selector is disconnected at contacts 230, 231. This does not however result in the restoration of the group selector because the short circuitaround the rclcaserelay 203 is kept open at contact 22:. The calling subscriber now On the first retraction of the armature otthe impulse relay 402 a current impulse flows from the negative pole through contact 400, 407, 408, wire 409, bank contact 410, wiper 414, contact 415 and through the magnet 419 bridged by the condenser 420. The magnet 419 pulls wheel 417 so that this wheel with the brushes 411 414 is rotated. brush 414 leaves the contact 410 but is immediately re-coiinected to negative potential by a long contact 421 so that the magnet 419 remains energized until the brush 410 reaches the contact 422, which in the meantime will have l ven disconnected from the negative pole by the rc-energization of the impulse relay 402. The magnet 419 thus allows thesto 'iping pawl418 to re-engasre with the wheel 4 .750 as to stop thc'brushcs 411, 41.4 on the set of bank: contacts corrcsp mding to the 411--414 is wound in such a way that the long steps of the brushes keep pace with the numerical impulses from the suliiscribcr. During the inter after the series oi ten impulses have been sent in the clni-nge over relay 424., which was energized by a current from the negative pole throu wl'i 0o, 4.25 to the po. t' pole is do -en: the short circuit closed at 420 so relay 427 is e'ner ized by a 0m from the negative pole throi.

n 5 ii) the positive pole. The impulse wire 431. is connected hytlie relay 427 and through contact 421 to an in .c-rrupter controls 1 by a cam disk 409/- :md'tlnoim h th s i 'ieilupter and a contact 434 it extends to the toothedmutant isfully re-woundthe circuit of the rewind-- ing magnet 15 is o ened at contact 83. In cases in which. a subscriber S replaces his receiver,pwithout ebrushes 58, 59, 60,

61 havingreac-hed his, bank contact set, the relaytiel is energized by a current that flows from the positive. pole through 85, 86, 87, left winding of 64 to thenegative pole. The re;

pulses which flow from the negative pole through theinterrupter 89, contact 90, magnet 88, brush 87, contact 83 to the positive pole. The brushes of the trunk finder are thus stepped forward until they reach a trunk whose associated contact83 is open.

In Fig. 7 a. manner of arrangingthe circuits in connection with the designating contacts of the line -finder is shown in which the inewla 3. f ra amp ea of a l scriber so, isconnects the battegyfrom two designating contacts 91, 92 asin Wig. 2. The arrangement of Fig. 7 differs-from that of Fig. 2 however in thatthe callin line is connected to the bank contact set 0 the desi nating contact 92 that is first reached by he finder wipers and thebrushes, if they should overstep the designating contact 92 and only be sto ped at. thenext contact 91, are stepped bad by a magnet 93 onto the contact 92.

In the arrangement shownin v5 the stopping magnet 19 is notbridged a condenser, but its quick operation is rought about by a resistance 94 beingincluded in its energizing circuit as soon as it has attracted its stopping pawl57'. I

In Fig. 6 the stopping magnet 19' has two coils. Theretractlon of the stopping pawl is brought about by the ampere turns of the energizin by'a win mg 96 at the moment in .which the brush 97 reaches adesig'nated contact. The counteracting ampere turns 96 are stronger to a certain degree than thearnpere turns 95 but not so strongasto cause the retracted stoppingpawl to be attracted again.

In Fig. 3? a group selector is shown which executes long rotary steps in response to numerical impulses instead of vertical steps. This is accomplished by means of a camldisk 300. The operation of'the selector will be obvious from the following description ofthe operations that take place in setting it onto the desired bank contact oup.

When a calling party as been connected through to the group selector, Fig. 3, its imwinding 95 being counteracted pulserelay 3.01 is energized. Italso results in the energization of the release relay 302 (negative pole, 303, 302, resistance 304, positive pole). Assumingthat the callingsubscriber sends in two numerical impulsesso that the armature of the relay 301 drops back twice, a current impulse will flow at each retraction" of the'armature from the negative pole through 305, 306, 307, 308, ar- I resting magnet 319, to the positive pole. The

magnet 319 pulls-the holding pawl 320 away from the toothed WllGCl 321 and this Wheel with the cam disk300 and the brushes 322. 323,324, 325 is rotated b the tensioned spring (similar to 14, Fig. 1 As soon as the pawl320 is disengaged from the tooth of the wheel 321and this wheel turns through a fraction ofthe pitch of the teeth the cam disk 300 closes thecontact 326, 327 so that the magnet 319 receives a current that flows from the negative pole through 327,326, 307, 308, 319 to the negative pole. The magnet 319 now remains energized until the spring 326 drops into the next notch 329 of the disk 300 so as to open the contact 327 and cause the pawl 320 to engage with a tooth of the wheel 321. The brushes 322-325 will now have executed one tens step. The next numerical iinpulse will now re-energize the magnet 319 in a circuit extending ironi the negative pole through 305,306, 307, 308, 319 to the positive pole. [The stop ping pawl. 310 is Q igainwitlidrawn from the toothed wheel 321, t

e contacts 326, 327 are again closed until thespring 326 drops into the notch .329 and the holding pawl. 320 againcngages the wheel 321; andithe brushes will then have completed.

their second. long step.

In the interval that ensucsafter the series of numerical impulses the changeover relay 330 is d e-energiz'ed by its being short-circuited at contact'331 so that the contact 332 is closed an'dthe relay 333 is energized by a current flowing from the positive pOle throughf332, 333, ofi-norinal contact 334 to negative pole. The relay 333 by its contact 334 now co'nnects the magnet 319 to thebrush 325. If the brush 325 is now standingon the bank contact of a freetrunk the magnet 319 remains de-energized and a current flows through the relay 336 in a circuit that extends from the positive polethrough 337, 336, 325, .wire338 to the next selector ahead. The relay 336 thus extends the calling party to the next selector. But if the brush 325 is standing on a busy trunk, that is'a trunk whose test wire is connected by a con tact 339 in the connector to the negative pole, the magnet 319 will be energized by .a current flowing from thepositivc pole through 319,308, 307, brush 325, contact 339 to the negative pole. The magnet 319 then again withdraws the holding pawl 320 from the wheel 321 and the brushes are rotated by the tension spring until brush 325 reaches a test or designating contact that is not connected with the negative pole and therefore belongs to a tree trunk. The holding pawl 320 now drops into the wheel 321 and arrests the brushes on the contact set of the tree trunk. lVhen the calling subscriber replaces his receiver he contacts 405, 408 are opened and contacts ii l0, 341 closed. The magnet 319 s now energized by a current flowing through the cit- normal contact 334, 341, 319 to the positive pole and this current continues flowing until the cam disk 300 presses the cam 34-2 against the spring 3% and thus opens the oft-normal contact 334. The holding pawl 320 is then released by the magnet 319 and the toothed wheel 321 with the cam disk 300 and the brushes is then arrested by the holding pawl 320 in the normal position illustrated. The rewinding magnet 34:5 receives impulses that flow from the negative pole through the interrupter 346, contact 340, 3&5, contact 3&7 until the contact 347 is opened by a cam 34S mounted on the spring box. The spring now being fully re-wound the rewinding magnet 345 is de-energized.

In Fig. 8 the positions of the bank contacts with respect to each other are diagran'nnatically illustrated. From this illustration it appears that the designating contacts (as F 48. 49) are displaced with respect to the other contacts of the contact row so that the voice current contacts 51, 51 and the contacts 51 connected to the holding wire are opposite to gaps betwen the contacts 41-8, 49. The holding pawl of the stopping magnet is adjusted so that it arrests the toothed wheel (e. g. 17, Fig. 2) moved with the brushes in a position in which the contacting ends of the wipers stand on a gap between two designating contacts but in the middle of the associated bank contacts 51, 51, 51 By this adjustment the greatest time of de-energization of the stopping magnet is attained.

Instead of displacing the bank contacts the same result can of course be obtained by displacing the ends of the brushes with respect to each other in a corresponding manner.

In reference to the selector shown in Fig. 1 it is to be mentioned that instead of the groove 29 and the pin 30 a guide fork 40 placed near the periphery of the wheel 17' and a guide arm 41 projecting from the shaft 1 and arranged to slide in the fork 40 may be provided. By this arrangement the play between the shaft 1 and the Wheel 17 can easily be reduced to a fraction of 21 millimetre.

It is also to be noted that the contact 433 may simply be opened and closed by the stopping pawl 418 instead of using a special cam disk L00 for this purpose. The cam disk e00 could then be dispensed with.

I claim 1. In a selector switch, a brush, bank contacts, a self-contained power device for driving said brush to any desired bank contact and then to a normal position, a b1usliarresting member that moves with said brush, an clectromagnet whose armature stops the brush on its deenergizing, and a circuit through said bank contacts for the electronn jnet which is opened when the brush reaches a desired bank contact.

An electrically operated switch com prising bank contacts, a brush, a self-contained power device that rotates the brush always in the same direction, a toothed brusharrcsting member that travels with the brush, an electroniaguetically operated stopping member adapted to engage with the teeth of said arresting member to stop the brush on any individual bank contact, electric circuits local to the switch which include bank contacts of same for controlling said stopping member, and a line loop for controlling said local circuits.

3. An elcctricall y operated switch comprisng bani: coi'itacts, a brush, a spring that rothe brush always in the same direction, .oothcd brush-arresting member that travcls with the brush, an electromagnetically operated stopping member adapted to engage with the teeth of said arresting member to stop the brush on any individual bank contact. electric circuits local to the switch for controlling said stopping member, and a line loop for controlling said local circuits.

+L. In a selector switch, a brush, bank contacts, a spring for driving said brush to any desired bank contact and then to a normal position, a ln-ush-arresting member that moves with said brush, and an electromagnet whose. armature stops the brush on its deenergization.

In a switch, bank contacts, a toothed wheel, brushes that wipe over said contacts. a self-contained power device for moving the bresaes and toothed wheel always in the same direction, a stopping pawl normally in engugem-cnt with said toothed wheel, an electromagnet for lifting said pawl from the toothed wheel to start the motion of the brushes and for letting the pawl engage with the wheel to stop the brushes on any desired individual set oi": bank contacts, and a condenser which influences said electromagnet to quicken the action of its armature.

G. In combination with a link circuit or trunk, bank contacts, brushes that wipe over the bank contacts, a brush carrier, a toothed member on the brush carrier, a brush-stopping member, an electromagnet for operating the brush-storming member, a power device for driving said brush carrier in a continuous motion until the brushes reach a desired set of bank contacts, a starting circuit for starting the motion of the brushes. a inotion-inaintaining circuit including said electromagnet. one of said brushes and bank contacts over which it travels, a trunk connecting relay for lid til

messes I means for propelling the brushes, a test mag net for testing the condition of the bank contacts and stopping the action of the propelling means when the brushes reach hank contacts that are in a certain condition, and acondenser cooperating with the test. magnet for accelerating its stopping function.

8. In a switch, rows of sets of bank contacts, brushes for selecting any said row, a self-containedv power device for driving a set of brushes in a continuous motion over a plurality of selectable rowsof sets of bank contacts, a toothed member that moves with said brushes, and a stopping member that engages with the toothed member and stops the brushes when they reach a desired individual set of bank contacts. a

9. In a switch, rows of sets of bank contacts, a longitudinally movable brush shaft with brushes adapted to cooperate with the bank contacts, a magnet for setting the brush shaft into a position in its brushes are in line with a said row of sets of bank contacts, a self-contained power device for moving the brush carrier so that its brushes travel in a continuous motion. over the row onto which they have been set, an arresting member that moves with the brushes when they execute continuous motion, and a stopping member that engages with the arresting membet and arrests it and the brushes when they have reached any desired set of bank contacts.

10. In a selector switch, rows of sets of bank contacts, brushes for selecting any said row, a self-contained power device for driving said brushes to any desired set of contacts in a row andthen to a normal position, a brush-arresting member that moves with said brush, an electromagnet whose armature stops the brush on its decnergization, and field-affecting means for affecting the field of said electromagnet to quicken the brush-stopping action of its armature.

11. An electrically operated conversational switch comprising, rows of sets of bank con tacts, brushes for selecting any said row, a Selfrontained power device for rotating said brushes over a selected row of bank contacts, a toothed brush-arresting member that rotates with the brushes, an electromagnetically operated stopping memberadapted to engage with the teeth of said arresting member to stop the brushes on any individual set of bank contacts, electric circuits local to the switch for controlling said stopping member, and a line for controlling said local circuits.

12. An electrically operated switch comprising, rows of sets of bank contacts,

brushes forselecting any said row, a spring for rotating the brushes overa selected row of bank contacts, a toothed brush-arresting member that rotates with the brushes, an electromagnetically operated stopping member adapted to engage with the teeth of said arresting member to stop the brushes on anyindividualoset of bank contacts, electric circuits local to the switch for controlling said stopping member, a line for controlling said local circuits, and means for rewinding the spring after each use of the same.

' 13. In a switch, rows of of bank contacts, brushes, a longitudinally movable brush-carrying shaft, a magnet for moving the shaft step-by-step longitudinal] y until its brushes are in line with the said row, and a self-contained power device for rotating the shaft continuously until its brushes reach a desired set of bank contacts.

14. In a selector, sets of bank contacts,

brushes, a power device for driving the brushes over said contacts, means for stopping the brushes on a desired set of contacts, and a magnet for moving the brushes onto the desired set of contacts if the stopping means fails toact. I

' 15. In a selector, sets of bank contacts, brushes, a power device for driving the brushes over said contacts, a toothed memher that moves with said brushes, a stopping pawl that engages withsaid member to stop the brushes on a desired set of bank contacts, and a magnet with an armature that cooperates with the toothed member to move the brushes onto the desired set of contacts if the stopping pawl fails to act.

16., Aselectorcomprising horizontalcurved rows of bank contact sets, brushes, a longitudinally movable and rotatable brush carrier, a stepping mechanism for stepping the brusl'r carrier upwards until its brushes reach a desired row of bank contact sets, a power de vice for then whirling the brush carrier round until its brushcs'reach a desired bank contact set, and an electromagnetically operated stopping member which engages with the brush carrier to stop the brushes on said bank contactset.

17. In a power driven hunting switch, bank contacts,brushes that hunt for a desired set of said contacts, a test magnet for controlling the movement of said brushes, and means operative during the hunting action of said brushes for accelerating the controlling function of the test relay.

18. A switch comprising, bank contacts, brushes that wipe over the bank contacts, a brush carrier, a spring for driving thebrushes,

a toothed member attached to the brush car- 1 rier, a stopping pawl that engages with the toothed member to stop the brushes on a desired set of bank contacts, an electromagnet for controlling the stopping pawl, a circuit for energizing the clectromagnet to withdraw the stopping )awl from the toothed member and to enuhl 1 the ring; to more the brushes, and a second circi i ia'ntaining' the electroin: ashes have i the b1 reached a do contact, said second circui aid brushes and some of sci for driving the brush a brush on niw cit-ow i withd raw 4 m min hruehcz-s, electr' JlilllI contacts, 1 bank contacts.

dev: 1

l 3 ed to the l .7

L ll: 4 7 net to withoraw it ni pawl 'trom i toothed member a1 enable the :ower

rice to more the brushes, second circuit for niainl mg the electron ag uetcnergizeduntil es have reached a at red bank cow iid n:

21 In a power-driven selector. an impulse receiving relay tor receiving electrical nu- 22. The coni itation ot a switch comprisng bank contacts, ln'ushes, a brush carrier, :1 method wheel adapted to rotate with said 1 carrier, at power device 'i'or rotating brush carrier a brush-positiouing pawl Hit coopc ates with said whccl, lines, electric impulse prod uccrs tor transmitting impulsee over said lines, and an clectroinagnet tor operating said p: wl relatively to said wheel to permitsaid power device to move said lDt'ttlitS stepwise in the rhythm of impulses a-aent mom said impulse producer over said lines.

ilfl. The combin; tion of a switch com n'is- "hank cintacts, brushes a brush carrier, a wheel adapted to rotate with said carrier, :1 power device for rotating 'lllil'ili @arrier, a brush-positioning pawl operates with said wheel, lines, electric racers for t 'ansmitting impulses d line 1 an electromagnet tor operat- 'd pawl relatively to said wheel to pereid power device to move sa id brushes wise in the rhythm of impulses sent trom it i inigulse producer over said lines, and an ciectromagnet for lifting said pawl from said wheel.

iZ-l. A rotary switch comprising bank conta cts, brushes, :1 brush carrie a toothed wheel fixed on the brush carrier, a pawl normally engaging with the toothed wheel, a power device for driving the brush carrier, and a sin- Q' Q magnet tor operating said pawl to allow FRITZ ALDENDORFF.

the iowcr device to more the brushes in steps

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