US2640108A - Wiper-switching selector - Google Patents

Description

R. TAYLOR WIPER-SWITCHING SELECTOR 4 She ets-Sheet 1 Filed NOV. 5. 1949 //v VE/V me EEG/Maw 77444 02 14 TIDE/V55 5 May 26, 1953 R. TAYLOR WIFER-SWITCHING SELECTOR 4 Sheets-Sheet 2 Filed Nov. 3. 1949 0&6 JMK Arrow/5V5 May 26, 1953 TAYLOR I 2,640,108 4 WIPER-SWITCHING SELECTOR 4 Sheets-Sheet 3 Filed Nov. 5. 1949 m v Z T m v H J m 00 00. a 0 0 000 ......L. W mm Em i. 1 w aw w .l. 114 P v w w w 0 M 1 1% H. 2 H l M 4 m M .l w\ F /4 M B w H a A m I, 3 B H A 2 3 c 1 Al N N R70 6 2 N C m V N 4 5 w N e 0 W A Patented May 26, 1953 WIPER-SWITCHING SELECTOR Reginald Taylor, Liverpool, England, assignor to Automatic Telephone Electric Company Limited, Liverpool, England, a British company Application November 3, 1949, Serial No. 125,299 In Great Britain November 11, 1948 12 Claims.

The present invention relates to automatic switches for use in telephone or like systems and is more particularly concerned with final selectors provided with two sets of wipers the required set being connected up in accordance with discriminating means, and with so-called penultimate group selectors which provide access directly over contact banks to said final selectors. The principal object of the invention is to provide improved circuit arrangements for such se lectors whereby the number of contacts and the amount of wiring in the penultimate selector bank multiples may be reduced and moreover the number of conductors in the cable connecting said bank multiples to the final selectors may be reduced.

According to one feature of the invention, in a group selector switch the wiper set includes a pair of wipers which are effective alternatively and serve to control wiper selection at a succeeding switch, the mechanical setting of the group selector switch being effected in response only to the odd impulses of a received train which also effect a wiper selecting operation as between the alternative wipers of each set, the reverse wiper switching operation being performed in response to even impulses if any.

According to another feature of the invention, in a group selector switch arranged to be set in response to a train of impulses which cause the intermittent tie-energisation of a control relay and provided with a pair of wipers which are used alternatively depending on whether the number of impulses in the train is odd or even, a relay which effects wiper switching is arranged to be energised in response to the first re-energisation of the control relay, to be maintained over a different circuit during the subsequent de-energisation of the control relay and to have its initial circuit opened on the following re-energisation of the control relay.

A further feature of the invention is that in a final selector switch provided with a plurality of sets of wipers the set to be used being determined in accordance with the route over which the switch is taken into use, separate test leads are provided for each access route the remaining leads extending to the switch being common for all access routes.

The invention will be better understood from the following description of typical methods of carrying it into effect, reference being had to the accompanying drawings comprising Figs, 1-5. Although the description has assumed the use of selectors of the two-motion type with so-called 2 rectangular release, the invention is in no way limited thereto.

Fig. 1 shows those circuit elements of a known 200-line final selector which provide for routing of a call to a subscriber in one or other of the two lOO-line subscribers groups in accordance with the speaking path over which the selector is taken into use.

Fig. 2 indicates the modifications to those elements in Fig. 1 to enable call routing to be effected in accordance with the private wire over which the selector is seized.

Figs. 3 and 4, which should be placed side by side with Fig 3 on the left, show the circuit of a penultimate selector which is intended to provide connection to final selectors having paths of entry of the type shown in Fig. 2.

Fig. 5 shows modifications to the outgoing portion of the selector shown in Figs. 3 and 4. to enable it to be used in conjunction with final selectors employing the known speaking path of entry discrimination arrangements shown in Fig. 1.

The known wiper switching arrangement shown in Fig. 1 is more completely described in United States Patent No, 2,113,119 dated April 5, 1938, and selectors of this type have been employed in conjunction with 200-outlet penultimate selectors of the type described in United States Patent No. 2,504,755, granted April 18, 1950. Such a final selector is normally linked to the penultimate selector bank multiple PSM by five conductors, namely the twisted pair of leads -l and +l which are associated with an outlet on an odd level (say level 1) of said multiple, 2. second twisted pair of leads 2 and +2 which are associated with a corresponding outlet on an even level (say level 8) and a common private lead Pi and P2 which is connected to the private bank contact of each of the said outlets. The use of two twisted pairs is desirable to avoid cross-talk diificulties and the negative leads from the two outlets are connected together at the final selector as indicated. When the final selector is taken into use over the odd level seizing earth is applied by the group selector to lead Pi and P2 and a calling loop is applied to leads -I and +l to operate relay AA. Relay AA thereupon operates relay BB (not shown) which at contacts BB! connects guarding earth to the incoming private lead. The tens digit is subsequently dialled and the wipers are raised to the appropriate level whereupon relay E operates and, in addition to performing the function of directing the units digit impulses to the rotary magnet, at contacts El it removes the shortcircuit from the left-hand winding of the Wiper 3 switching relay WS. The short-circuit remains removed until the rotary off-normal contacts NR close when the wipers advance into the bank in response to the dialling of the units digit. However, since the conductor +2 has not been employed, relay W S remains normal and determines that the final selector connects over wipers l, +1 and Pi to that subscribers line appropriate to the tens and units digits dialled in the odd hundreds group OHG. If that line is idle, relay H operates, applies seizing earth at contacts H3 in known manner and causes the subscribers bell to be rung. Subsequently when the subscriber answers, the battery feeding relay D is introduced and conversation proceeds. On the other hand if the final selector is taken into use over the appropriate even level of the penultimate selector, seizing earth is again applied to the common private lead but the calling loop is applied to leads 2 and +2. Consequently when contacts El open after the tens digit has been dialled, relay WS is enabled to operate on its left-hand winding which is connected in series with the calling loop and the outer windings of relay AA. The lightly adjusted contacts WSl close and together with other contacts, omitted for simplicity, provide a holding circuit for relay WS. The operated contacts WS2, W S3 and W84 ensure that, when the units digit has been dialled, the call is routed over wipers 2, +2 and P2 to the appropriate subscribers line in the even hundreds group EHG.

Reference will now be made to Fig. 2 which Where practicable employs the same reference characters as Fig. l and may be assumed to be a final selector substantially similar to that described with reference to Fig. 1 except that according to the invention access to it is obtained in a somewhat different manner. In this case a single speaking path of entry is provided over leads and while two separate incoming private wires EP and OP are provided. To appreciate the significance of the path of entry arrangement shown in Fig. 2 it will be necessary to consider its function when final selectors including it are employed in conjunction with penultimate selectors of the type shown in the drawingcomprising Figs. 3 and e.

The penultimate selector shown in Figs. 3 and 4 employs a mechanism of the well-known vertical and rotary type which is preferably, although not necessarily, adapted to enable the wipers to be raised a maximum of five steps instead of ten. The selector is employed in conjunction with four bank contact assemblies each of which however includes only five levels each comprising two rows of eleven contacts each. A total of 440 bank contacts is therefore employed and since the 11th step contacts are not used for normal traffic purposes, it will be permissible to refer to the selector as of the 5/20 type i. e. having five levels each of twenty outlets. The twenty outlets on each level all extend to separate final selectors which embody the private wire path of entry discriminating arrangements shown in Fig. 2, teen outlets extending to first choice final selectors FSI and ten to second choice final selectors F82.

When the penultimate selector is taken into use, relay A is operated over its outer windings by the application of the calling loop to the and leads by way of the preceding selector GS. Thereupon a circuit is completed by contacts Al from earth at contacts N4 to operate relay B in series with the vertical magnet VM, the latter remaining inoperative. Relay B on operating, at contacts BI provides a holding circuit for itself and prepares impulsing circuits to the vertical magnet and relay OH, at contacts B2 operates relay C in series with resistor YD, at contacts B3 connects earth to the incoming P lead for guarding purposes and to hold the preceding equipment, at contacts B4 prepares a holding circuit for relay H3, at contacts B5 prepares a circuit to the tone winding of relay A, at contacts BB opens a point in the release circuit which extends to earth by way of delayed alarm equipment over common lead II, and at contacts Bl prepares to operate relays HA and HB.

When relay C operates at this stage, it prepares circuits for relays HA and H3 at contacts C3, at contacts C4 prepares a circuit for shortcircuiting its own winding, at contacts C5 opens a point in the locking circuit of relay OH, at contacts CB-short-circuits resistor YB preparatory to the application of impulses to the vertical magnet, and at contacts C1 opens a point in the circuit for the rotary magnet RM. Thus when the selector is seized relays A, B and C are operated.

No further change takes place until the hundreds digit is dialled whereupon relay A responds .in known manner to follow the impulses. Upon the first release of relay A, its contacts simultaneously short-circuit relay B and apply full voltage to the vertical magnet VM. Relay Bv is therefore rendered slow to release while the vertical magnet is operated to actuate contacts VMC and to raise the selector wipers to level I. The latter action causes the vertical off-normal contactsto operate and these, which remain operated until the wipers are subsequently returned to normal, at contacts Ni prepare the rotary magnet circuit, at contacts N2 prepare the ultimate holding circuit for relay HA or HB and later provide a release guarding circuit, at contacts N3 operate the switching relays HB and HA on their upper and lower windings respectively from earth on the P conductor, and at contacts N4 disconnect the earth which initially operated relay B. Relays HA and HB are now effective in that contacts HA2 and HB'l prepare the outlet testing circuit for relay HA, contacts HB2 prepare a similar circuit for relay HB, contacts HA4, HA6 and HB4 prepare circuits to control relay C, and contacts HA5 and H136 prepare the rotary magnet driving circuit.

When the loop is again closed after the first break, relay A re-operates thereby permitting the decaying flux in relay B to build up again and at the same time providing a circuit to maintain the vertical magnet operated and to operate relay OH from earth over contacts Bl, Al, SI and VMC, the fairly low resistance middle winding of relay OI-I, contacts C5 and NR! and the vertical magnet to battery. Relay OH on operating, at contacts OH! connects its left-hand winding in series with relay B, at contacts 0H2 prepares a holding circuit for itself, at contacts 0H3 applies a short-circuit to relay C whereby that relay is rendered slow to release, and at contacts 0H4 and 01-15 respectively prepares testing circuits to the private wipers CPI and 0P2.

It will be apparent from the foregoing that when digit 1 has been dialled the Wipers are raised to level I and relay OH is operated. If however a second break is received, relay A releases again whereupon relay B is again shortcircuited, the short-circuit is removed from relay C, and full voltage is applied to the left-hand winding of relay OH to hold that relay. At'the same time the vertical magnet and the middle winding of relay OH are disconnected by contacts Al, and the magnet releases to restore contacts VMC. Upon the succeeding make, the short-circuit is removed from relay B whereupon the flux due to the left-hand winding of relay OH is reduced to such a value as to enable that relay to release and relay B is then again connected in series with the vertical magnet which is not now operated. Thus when digit 2 has been dialled, the wipers remain at level I but relay OH is normal. Relay C is again short-circuited at this stage.

The penultimate selector continues to function after the manner described if the dialled impulse train includes further impulses, that is to say, the vertical magnet is caused to raise the wipers one step upon each odd break and relay OH is operated on the succeeding make, while the wipers are not raised further by an even break but relay OH is released upon the succeeding make. Thus, by way of example, when digit 7 is dialled, the Wipers are raised to level 4 and relay OH remains operated, while when digit 8 is dialled the wipers are raised to the same level but relay OH is released. It may be noted that the alternate energisation and application of a impulse train. Assume now that the hundreds digit 8 has been dialled, so that the wipers are raised to level 4 and relay OH is deenergised. At the conclusion ,of the impulse train, relays A and B remain operated but relay C is short-circuited by earth over contacts Bl, HA6 and C4 and after a short delay releases. Thereupon at contacts C! it completes the circuit to the rotary magnet RM in series with the low resistance windings of relays HA and H8. The rotary magnet therefore operates to advance the wipers into engagement with the first set of bank contacts, and towards the end of said advancement to open the interrupter contacts RMC whereupon the magnet is de-energised. During this rotary step, the rotary 011- normal contacts also operate and ensure at contacts NRI that resistor YB remains in series with th vertical magnet, at contacts NR2 and NR3 prepare to disconnect relay A, and at contacts NR4 and NR5 open the initial circuits for relays HA and HB so that these relays are consequently made dependent upon the condition encountered by wipers EP2 and EPI respectively.

The wipers having advanced on level 4 to the first set of bank contacts which are associated with an outlet to a first choice final selector FSl and another outlet to a second choice final selector FSZ, one of four possibilities now obtains namely, that wiper EPI connects with the private conductor of an idle outlet while wiper EP2 connects with a busy outlet, that both wipers connect with idle outlets, that wiper EPZ connects with an idle outlet and wiper EPI with a busy one, or that both wipers connect with busy outlets.

Consider first the possibility in which wiper EPI encounters an idle outlet as evidenced by the absence of earth, while wiper EPZ encounters a busy outlet denoted by the presence of earth. Under these conditions relay HB releases since its low resistance winding is disconnected at contacts RMC and its upper winding is dependent on the condition of wiper EPI on whi h no earth is found. Relay HA is therefore disconnected at contacts HB! and also releases. The rotary magnet circuit is disconnected at contacts H36 and HA5 to prevent re-operation of that magnet upon the closure of contacts RMC. Moreover relay HB at contacts HB2 disconnects its own testing circuit and applies guarding earth to the EPI wiper to seize the encountered idle outlet, and at contacts HB5 prepares a circuit to re-operate relay HA. Meanwhile relay HA on releasing, at contacts HA4 and HA6 removes the short-circuit from relay C which therefore re-operates, where: upon a new circuit is completed to re-operate relay HA on its lower winding from earth extending over contacts B3, N2 and C3, resistor YC and contacts HES. Contacts CI and C2 connect the calling loop through to the wipers and release relay A which short-circuits relay B but, since resistor YB is inserted in series with the vertical magnet by contacts NRI, an earth pulse derived from contacts Al does not effect said magnet. Contacts C4 together with contacts HA4 provide the ultimate holding circuit for relay C, and contacts Cl disconnect a point in the rotary magnet circuit. Meanwhile the operated contacts HA3 and HAI connect the calling loop to the -l and +l wipers whence they are extended to the and conductors of a final selector such as that shown in skeleton form in Fig. 2. It may be mentioned that relay AA in that final selector is consequently operated and in turn operates a relay BB (not shown) which at contacts BBI connects a guarding and holding earth to lead EP, Fig. 2, and thence to lead EPI in the penultimate selector. Contacts HA1 in closing maintain a connection between lead EPI and the incoming P lead upon thesubsequent opening of contacts B t. Relay B is short-circuited at contacts AI and releases after a short delay and at contacts B3 removes the local guarding earth from the P lead, the guarding facility now being provided by earth returned by the seized final selector. Contacts B2 disconnect the initial circuit for relay C, and contacts B6 prepare the driving circuit for the rotary magnet which is .to be completed upon the release of the selector.

It now follows that the condition of the circuit is such that relay HA remains operated from earth returned to the P conductor over contacts BBI and El and lead El? in the final selector, Fig. 2, and wiper EPI, relay C is maintained operated dependent upon relay HA, and a clear signalling and speech path is extended to the final selector. Later during the inter-digital pause following the dialling of the tens digit when relay E in the final selector operates, the short-'- circuit is removed from the left-hand winding of relay WS. Thereupon that relay operates, and then holds on its other winding over contacts WSl in preparation for the closure of the 01T- normal rotary contacts INR upon the units digit being dialled. Relay WS functions as described in connection with Fig. 1 to route the call to a subscriber in the even hundreds group. It may be mentioned that the resistance of the left-hand winding of relay WS is fairly low so as to maintain a guard condition on lead EP during the period when contacts El and NR! are both open.

In the second before-mentioned possibility when both outlets encountered by the penultimate selector wipers are idle, neither HA nor HB can be maintained over the associated test wiper. Both relays therefore release and thereafter the selector functions in the same manner as in the case just described in that relay C re-operates followed by relay HA whereupon the preferential or first choice outlet associated with wipers +l and EP! is taken into use.

Considering now the third possibility, arising e i1 ivitli operated f g1ita t e3 t eithds thecallin'g io op rhg g ie elector is as ed by the immediate appli earth over private wiper E112 se are: operated from earth return the seise'tl final selector over w' i "i ate; c'ostacts HB'I, HA2, N2 and c3; re-

as r Y0, and contacts Accordingly the iiicbiiiizig and bendiiabis connected to ase nd choice ana seie'cwr, again s'iniilar to that sudden Fig.2, ever Wipers 2 ami 2 ti 'co'iitacts HE! and use, while relay o matetained eperatu y eoiitacts' Pisa. As in the other the" eimrhpies relay e i the final selector is epeiat'ed and the can is routed to a subscriber in the eir'eh hundreds g oup In the fourth ease; in which both wipers en'- ciii'mt'e'i busy outlets, relays HA and H13 both remain op'ratedfdiie to the earth conditions enceunter'ea by the testing wipers EPI and E152.

censequentiywheri the interrupter contacts RMC close again, the rotary magnet is re-energised to advance the wipers to the second set 01" bank contacts whereupon anyone of the four described conditions 01" the outlets may become op I erative. 'It may be mentioned that resistor YA whichshunt's the rotary magnet is included to controlthe'speed of rotary stepping.

Shouldthe wipers be advanced over thewh'ol'e group of twenty outlets \vithout'enco'untering an idle. one, they will be stepped to the 11th set of bank contacts whereupon the so-called S contacts operate. Contacts S3,..consequently open a point in the path to relay 'HB which, releases, and also complete acircuit toope'rate thefoverfiow meter which terminates on lead l2. Relay HA also re"- leases since, 7 apart from its circuit being broken at contacts H1311, thellth EP2 b'ank contact is left unwire d, Rela Ctheh operates and is foilo edig y the re-operation of relayHA. so that condi one similar to thoseprevailing in the case of wipe'r eneountering an idle contact are i i i te wll sl dm sw p tha se l s i r vert d by way of the llthpositionwiring at banks f +1 to t he outer windings of relay lA E i hi fi i ?ly st a ily. ene is d It .ldivsth'at relay rernains operated this stage hus y toes is 'n i'ade audible in known znannerto the calling pat y by the application of busy tone earth, e iktend ihg from co n non iead lll by consfl fi t. m d wi d n of elay 3A w i h tion's :a fthe "transformer. Contacts Si prevent'th application or" a short-circuit to relay h must remainoperated while contacts S2 rel relay OH if it has been operated.

fjlssurne how that an odd hundreds digit for instance 7 is tr In this case the penultiinate selector ipers are raised to -level A, as'in the case of digit fi being dialled but additionally relay OH is operated, It will be apparent there- .fore, that as the ipers eventually advance over the level the sar egroup of outlets will be tested as e 'te itup nd e tfi bein i lled. Meantime on conclusion of the digit 7 impulse train, relay C releases and, in addition to the functions amass 8 firevfidiis y dse'rnid, provides a holding circuit for i'elay OH hem earth over contacts CA, HA4, C5 a ia om, The Wipers a vance mm the bank ljefo're wh reupon the dfi normal teary con tacts are new enabled at contacts NR6 to peribfi i theadditional function or preparing the ult mate holding circuit for relay OH w en relay e finally operates Iii this case since on is o'p'ere fitted, cohtact s QH Land Ofii presenti'elays HB aii naiej tptiveiy to the CPI an 0P2 wipers respectivel iri' addition to wipers EP! and 1 :92. If. e anaem -s .fii lr e sfi h i busy, i is returnees contacts BBI, Fig. 2, by way of leads El? OP respectively tothe appropriate EPI and GP! pain: contacts and siinilarly if a second eh'o'iee outlet may, earth is connected to the appropriate EP2 0P2 b'aiik contacts; The Wipers of the penultimate selector advance into the b'arik (in level I and it may be assumed that the outlets are tested after the xiianner described in c'o'rinctidh with the dialling; of digit 8. Thus, vay of exarnplc, if an idle first choice outlet EStis encountered, relays H13 and HA release, reia c o erates, re a'y' A reieass and relay HA re operates; The latter relay eikecutes its harm-s1 function's, in'clufdihg the l iteiisihh of the canine loop to the Seized final 'sletbi over timers '--1 anti |l, and finally relay B ilea's's. Relay OH remains operated in series with relay Q When this latter r'elay l e-operates on the removal of the sh'ort ci-rcuit from its Winding. Meantii'ne in the final selector relays AA and BB operate the earth at contacts BB: is connected to lead or directly and to lead E7? over contacts El. Howeversince contacts 0H4 are closed, a full earth is maintained on lead EP 'over said contacts to shortcircuit the left-hand Winding of relay WS e'v'h during the period el'a'psing between the operation of contacts Bi and INR preceding the dialling of the units digit. it will be apparent that if this precaution were not taken it would be possible for another penultimate selector, testing the final selector EP lead during said period, to this-route the callto the even hundreds group by operating relay lN-S when an odd digit is dialled therefore, the W5 relay of the final selector taken into use regnains inoperative and the call is a/ppfopriately routed to a subscriber in the "odd huhsaemuri l 4 I t Whip? evident that had a second choice final selector been takeninto use after the dialline of an odd hundreds digit, contacts 0H5 would have per formecl a similar function to that ix eiesi Q ex n Referring briefly to the release of the :penultiniat'e selector and assuming -by way of example that it has been engaged on a call to a 'su scrilee r in an odd hundreds group 'by way of ja fiis choice outlet. When the calling party clears, ife ays and BBin the final selector, 2 jrlease sothat earth is removed *by con r H f rorn the-ER] and OPI jbank'contacts'w r'e ease relay HA. Relays C and. OH which are cliscon ected at contacts I-IA'A also release "and the fo rrner immediately places a release guard earth on the incoming P lead over contacts C3 and N Relay Q at 'contacts 01 'also 'complets g a driving circuit to the rotary magnet from release alarm earth "extending over 'coinmon lead l so that thewip'ers are advanced "b'eylind the 1 '1th step position-and continue "their sci-'alld ;rectangular path to the hoifiial passion, during which theoff-normal cdntacts NRI to NR6 restore, when the wipers attainthe norm-appasition, the vertical off-normal contacts NI to N4 9 restore and the guarding earth is removed from the incoming P lead at contacts N2 so that the selector may be taken into use for another call. It may be mentioned that contacts B1 are included to prevent false operation of relays HA and HE during the releasing operation.

Referring now to Fig. 5 which includes modifications to the outgoing portion of the penultimate selector shown in Figs. 3 and 4 to enable it to be used in conjunction with existing final selectors of the type shown in skeleton form in Fig. 1, it will be appreciated that of the leads associated with one of the first choice outlets, the common negative lead I extends to the lead designated l and Z in a final selector Fig. 1, the odd positive lead connects with the lead +l, the even positive lead E-i-l with +2, and the private wire Pl connects with the final selector private wire designated Pi and P2. Each of the second choice outlets FSZ is similarly connected to final selectors.

When a hundreds digit is dialled, the modified penultimate selector functions as already described in that the wipers are raised one step in respect of each odd impulse only and, if the digit is odd, relay OI-I remains operated at the end of the impulse train, whereas if the digit is even, relay OH is unoperated at the end of the train. Assume that an even digit has been dialled, the wipers advance along the bank level determined by that digit and the outlets are tested as already explained. If a free first choice outlet is encountered, relay HA finally operates and switches the call to that outlet and contacts 0H4 ensure that wiper E-i-l is employed. Subsequently during the inter-digital pause preceding the dialling of the units digit, the short-circuit is removed from the left-hand winding of relay WS, Fig. 1, which operates in series with the calling loop and the outer windings of relay AA. The operation of relay WS determines that the call shall later be routed to a subscriber in the even hundreds group. When an odd digit is dialled, relay OH remains operated at the end of the train, and, if a first choice outlet is again seized, contacts 0H4 ensure that wiper 0+! is used. Consequently relay WS is not operated later and the call is routed to an odd hundreds subscriber. Similar considerations apply when second choice outlets of the penultimate selector are taken into use.

When penultimate selectors embodying the modifications shown in Fig. 5 are employed, it will be necessary in order to reduce cross-talk interference, to suitably twist together the three speaking conductors throughout the bank multiple and the inter-connecting cable.

I claim:

1. In a group selector for use in a telephone system, a first relay arranged to be operated intermittently in response to a train of impulses for setting the switch, a stepping magnet, a set of wipers including a first wiper and a second wiper, a second relay arranged to render effective one or both of said first and second wipers determined by its state of de-energization or energization, a first winding on said second relay, means for energizing said second relay by way of said first winding in series with said stepping magnet in response to the first re-energization of said first relay, a second winding on said second relay, means for maintaining said second relay operated over said second winding during the subsequent deenergization of said first relay and means for preventing the completion of the initial circuit through the first wind- [0 ing of said second relay when said first relay again energizes.

2. In a telephone system, a final selector switch, a plurality of sets of wipers for said switch, means for operating said final selector from any one of a plurality of means of access, incoming speaking leads common to all the means of access, a plurality of separate incoming test leads individual to the difierent means of access, and switching means for causing a particular set of wipers to be effective dependent on the particular test lead used.

3. Switching apparatus claimed in claim 1 comprising, in addition, a relay controlling wiper selection means for the succeeding switch, a test circuit in which said alternately effective wipers are included for cooperation with the said relay controlling wiper selection and adapted for connection between the test contacts.

4. The switching apparatus claimed in claim 3 comprising, in addition, means including a second switch for connecting the test wipers together in one of the operating conditions to avoid operation of the relay in the selected succeeding switch at the same instant through the wiper providing a series circuit for said relay.

5. The switching apparatus claimed in claim 1 comprising, in addition, a driving magnet, a series circuit including the relay, contacts controlled by the magnet and the make contacts of the control relay for initially energizing the relay.

6. The switching apparatus claimed in claim 1 comprising, in addition, contact elements for the relay connected to change the impulsing connection from the break contacts of the control relay from the magnet to its own winding.

'7. The switching apparatus claimed in claim 6 comprising, in addition, a third relay having a. break contact element, and means to maintain the control relay operation including a circuit of which the break contact forms a part, said relay remaining energized when the number of impulses in the train is odd and releasing when the impulses series ceases.

8. In a telephone system, a group selector comprising a set of wipers including a first wiper and a second wiper, a set of bank contacts for each of said wipers, a plurality of succeeding switches each having a plurality of sets of wipers, connections extending from said sets of bank contacts to said switches, means in said group selector for completing a control circuit over either said first wiper or said second wiper to efiect wiper selection in a selected one of said succeeding switches, means in said group selector for responding to a train of impulses, means responsive to the odd impulses of said train for effecting mechanical movement of said set of wipers including said first wiper and said second wiper and for transferring control from said first wiper to said second wiper and means responsive to any even impulses of said train for transferring control from said second wiper to said first wiper.

9. The group selector claimed in claim 8 comprising, in addition, means to establish group selecting movement of the wipers in a vertical direction and means to establish hunting movement of the wipers in a rotary direction.

10. The group selector claimed in claim 9 in which the bank for each wiper comprises a unit of five levels only.

11. In a telephone system, a final selector switch having a plurality of sets of wipers, a plurality of control paths, means for operating said final selector from any one of the plurality of i a-cio, 10a

paths, incoming speaking leads =comm0n to all of said paths, a plurality of separate incoming testl'l'eads: individual to the difierent paths, switching means forcausing a selected one of the pin-- 'ralityeof sets of wipers to become effective in accordance with the particular test lead currently .u'sed a relay for controlling the .set of wipers to he used, and means for connecting the relay winding of the set of wipers to be used in series with .the test lead corresponding to one of the separate control paths during the interval between two trains of impulses tO'WhiCh the switch responds.

"I2. Atelephone system comprising a'finalselector switch, a plurality of sets of wipers .Iorsaid J switch, a plurality of control paths, incoming woice connections common to all of the control -pathspa plurality of :"separate incoming test leads individual to the several paths, switching means controlled from the test leads for causing one set-0f wipers to become efiective on a selected test lead, and means for causing the first digit received to eiTect movement of the Wipers in avertical direction, and a second digit received to effect movement of the Wipers in a rotary direc- .tion.

REGINALD TAYLOR.

References .Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,956,371 Christian Apr. 24, 193 4 2,137,422 Taylor Nov. ,22, 1938 2,222,126 Taylor Nov. 19, 1940

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